GB2610821A

GB2610821A - Surgical instrument and cartridge therefor

Info

Publication number: GB2610821A
Application number: GB2113174.3A
Authority: GB
Inventors: Ridler Keir
Original assignee: Salthaus Ltd
Current assignee: Salthaus Ltd
Priority date: 2021-09-15
Filing date: 2021-09-15
Publication date: 2023-03-22
Anticipated expiration: 2041-09-15
Also published as: GB2610821B; GB202113174D0

Abstract

A cartridge 200 configured to store a fluid to be dispensed by a surgical instrument 100, comprising an elongate cartridge body 210 having a longitudinal axis, a cartridge reservoir in the cartridge body for storing the fluid and a first protrusion 220 and a second protrusion 230 on an outer surface of the cartridge body. The second protrusion is longitudinally and angularly offset from the first protrusion with respect to the longitudinal axis and rotation of the cartridge along its longitudinal axis causes the first protrusion to engage or disengage a latch in the surgical instrument to respectively secure or release the container from the carriage. The surgical instrument comprises a hand-held housing 150 having a proximal opening for the cartridge and a drive arrangement (110, fig 2) with a carriage (600, fig 4) which facilitates the engagement/disengagement of the cartridge. In other embodiments the drive arrangement comprises a dual pawl ratchet (fig 2a). The dual pawl ratchet comprises a ratchet wheel and two pawls arranged so that when one of the pawls is engaged to drive one or more teeth of the ratchet wheel, the other pawl is disengaged from any of the teeth of the ratchet wheel.

Description

SURGICAL INSTRUMENT AND CARTRIDGE THEREFOR

Technical Field

The present invention relates to surgical instruments and in particular to surgical instruments for fluid delivery.

Background

Many surgical procedures involve the delivery of fluids, such as surgical adhesives, to anatomical sites. Devices have been proposed which allow delivery of fluids during surgery. Typically, these are devices with a handle allowing a predefined volume of fluid to be dispensed accurately.

Existing fluid delivery devices have a number of limitations. One such limitation is dispensing a single predetermined volume of fluid each time. This will generally be small, to avoid dispensing too much, and means that repeated dispensing operations are required for a larger volume of fluid. A related limitation is that the volume to be dispensed cannot be selected by a user. To address this, devices comprising syringes that are advanced directly by a user have been proposed. While this allows a wide variation of dispensed volume, it is difficult to consistently dispense a desired quantity of fluid using such devices, and the syringes can be prone to "stick-slip", potentially leading to an inadvertent dispensation of a large quantity of fluid.

Another limitation is that fluid delivery devices for surgery are often single use devices capable of dispensing a particular volume of fluid. It may be necessary to use several single use devices during the course of a surgical procedure if more fluid is required than the particular volume, or fluid may be wasted if less than the predetermined volume is required.

It would be desirable to provide a surgical instrument for fluid delivery which addresses at least one of these limitations.

Summary

According to a first aspect of the invention, there is provided a cartridge for a surgical instrument, the cartridge configured to store a fluid to be dispensed by the surgical instrument, the cartridge comprising: an elongate cartridge body having a longitudinal axis; a cartridge reservoir in the cartridge body for storing the fluid; and a first protrusion and a second protrusion on an outer surface of the cartridge body, wherein the second protrusion is longitudinally and angularly offset from the first protrusion with respect to the longitudinal axis.

By spacing the first and second protrusions as such, the cartridge may be insertable and/or securabl e in the surgical instrument i n a parti cul ar orientation. This may, for example, ensure the cartridge is inserted correctly and/or that the surgical instrument and/or cartridge is appropriately primed. This may also reduce the likelihood of the fluid being unintentionally discharged when inserting the cartridge into the surgical instrument.

The cartridge may also be referred to as a "container'.

Optionally, the first protrusion is located towards a distal end of the cartridge, and the cartridge is insertable into the surgical instrument distal-end first. Optionally, the cartridge comprises plural first protrusions located at the distal end of the cartridge, such as two first protrusions located on opposite outer surfaces of the cartridge body. The or each first protrusion may herein be referred to as a "distal protrusion", while the or each second protrusion may herein be referred to as an "offset protrusion".

The first protrusion may be configured to pass through a proximal opening of the surgical instrument when a distal end of the cartridge is inserted through the proximal opening.

Optionally, the proximal opening comprises a groove shaped to permit the passage of the first protrusion therethrough. Optionally, the proximal opening comprises plural grooves configured to permit a passage of the respective first protrusions therethrough The second protrusion may be proximally spaced and angularly offset from the first protrusion so as to engage the proximal opening of the surgical instrument when the distal end of the cartridge is inserted into the surgical instrument in a first orientation of the cartridge The second protrusion may be proximally spaced from the first protrusion by an amount such that the distal end of the cartridge is in a first dispensing position in the surgical instrument when the second protrusion engages the proximal opening. The first dispensing position may be such that the distal end of the cartridge, or a part thereof, is engaged with a plunger and/or carriage of the surgical instrument, the plunger and/or carriage configured to cause the fluid to be expelled from the cartridge, in use. Optionally, the distal end of the cartridge is configured to receive a plunger of the surgical instrument. In this way, the cartridge may be inserted into the surgical instrument in a distal direction and/or removed from the surgical instrument in a proximal direction without being obstructed by the plunger. Optionally, the first dispensing position corresponds to a position at which the plunger extends into the cartridge by a predetermined amount, such as to prime the surgical instrument and/or cartridge for use. Providing the second protrusion may therefore ensure the cartridge is properly positioned in the surgical instrument before use, such as to avoid a premature dispensation of the fluid from the surgical instrument.

Optionally, the cartridge comprises a plunger seal at the distal end of the cartridge. The plunger seal may be slidable in the cartridge, such as within the cartridge reservoir, to cause the fluid to be dispensed from the cartridge. Optionally, the plunger seal comprises a plunger seal aperture therethrough, through which the fluid can be dispensed from the cartridge, in use. Optionally, the plunger seal is configured to interface with the plunger of the surgical instrument, so that the plunger causes the plunger seal to advance within the cartridge as the cartridge is advanced relative to the plunger. Optionally, the plunger comprises an opening at a proximal end thereof, and the plunger seal aperture is fluidically couplable to the plunger opening. In this way, fluid stored in the cartridge is dispensable from the cartridge reservoir, through the plunger seal aperture, and into the plunger via the plunger opening. Optionally, the plunger head and plunger seal are reciprocally shaped, such as to provide a fluid-tight seal between the plunger head and plunger seal, such as between the plunger opening and the plunger seal aperture.

Optionally, the first orientation is a first rotational orientation of the cartridge along a longitudinal axis thereof In this way, the cartridge can be inserted into the housing by aligning, such as by rotationally aligning, the first protrusion with a corresponding groove in the proximal opening of the housing. Optionally, the protrusion is located towards a distal end of the cartridge, and the cartridge is inserted into the housing distal-end first.

The second protrusion may be located so that, following a rotation of the cartridge from the first orientation to a second orientation in the surgical instrument, the second protrusion can pass through the proximal opening.

The first and second protrusions may be located so that the cartridge can only be rotated into the second orientation when the cartridge has been inserted into the housing by a predetermined amount, such as when the second protrusion abuts, or is in very close proximity to, the proximal end of the housing. This may ensure the cartridge is properly inserted into the surgical instrument, and/or that the surgical instrument and/or cartridge is properly primed, before the cartridge is rotated into the second orientation. For instance, the surgical instrument may comprise a distal opening and a conduit, or fluid path, fluidically connectable between the cartridge reservoir and the distal opening. The surgical instrument may be "primed" when the fluid path comprises, or is filled with, fluid stored in the cartridge reservoir, such as due to the action of inserting the cartridge into the housing until the second protrusion abuts the housing. The cartridge may comprise a gas in the cartridge, in addition to the fluid to be dispensed, and the cartridge may be primed when the gas has been expelled from the cartridge. Alternatively, there is no such gas in the cartridge, and the cartridge is already primed for use.

The first protrusion may be configured to engage a carriage of the surgical instrument to secure the cartridge to the carriage when the cartridge is rotated from the first orientation to the second orientation in the surgical instrument.

Optionally, the first protrusion is configured to disengage from the carriage to release the cartridge from the carriage when the cartridge is rotated from the second orientation to the first orientation in the surgical instrument.

Optionally, the second orientation comprises a rotation of the cartridge from the first orientation by an angle of up to 45°, up to 90°, or up to 120°. A greater angle of rotation may improve a level of engagement between the protrusion and the latch and/or the connector. The rotation may be a clockwise rotation when viewed along the longitudinal axis from the proximal end. Alternatively, the rotation may be an anti-clockwise direction when viewed along the longitudinal axis from the proximal end. Optionally, the second protrusion is angularly offset from the first protrusion by up to 45°, up to 90°, or up to 120°. The angular offset of the second protrusion may correspond to the angle of rotation of the cartridge from the first orientation to the second orientation, such as to ensure sufficient engagement of the protrusion with the latch and/or connector. Optionally, the second protrusion is longitudinally offset from the first protrusion by up to 15mm, up to 25mm, or up to 40mm. A greater longitudinal offset of the second protrusion may ensure the cartridge is inserted further into the housing and/or carriage before being rotated into the second orientation. This may provide improved stability of the cartridge in the carriage, such as in use, or when coupling and decoupling the cartridge from the carriage A shorter longitudinal offset may reduce a size, such as a length, of the housing required to accommodate the cartridge, and/or improve an ease of insertion / removal of the cartridge by providing a greater portion of the cartridge that can be gripped external to the housing. As such, it will be understood that the longitudinal offset of the second protrusion from the first protrusion may be any other suitable value depending on the size of the cartridge and/or the housing.

Optionally, the cartridge is rotatable along a longitudinal axis thereof from the first orientation to the second orientation Optionally, the surgical instrument comprises a carriage for receiving the cartridge. Optionally, first protrusion is configured to engage the carriage to secure the cartridge to the carriage when the cartridge is rotated from the first orientation to the second orientation. Optionally, the first protrusion is configured to disengage from the carriage to release the cartridge from the carriage when the cartridge is rotated from the second orientation to the first orientation Optionally, the proximal opening comprises a flexible portion configured to prevent the passage of the second protrusion therethrough into the housing when the cartridge is in the first orientation, but to permit the passage of the second protrusion therethrough out of the housing when the cartridge is in the first orientation. In this way, removal of the cartridge can be achieved by rotating the cartridge to the first orientation.

Optionally, a proximal side of the second protrusion comprises a ramp, or slope, to facilitate removal of the cartridge past the first and second flexible portions when the cartridge is in the first orientation.

According to a second aspect of the invention, there is provided a surgical instrument for use with the cartridge of the above described first aspects, the surgical instrument comprising the proximal opening into which the cartridge is insertable and a carriage for receiving the cartridge, the carriage comprising a latch, wherein a rotation of the container along its longitudinal axis in the carriage causes the first protrusion to engage or disengage the latch to respectively secure the container in or release the container from the carriage.

Optionally, the surgical instrument comprises any one or more of: a housing to be held in the hand, the housing comprising the proximal opening, a hollow shaft extending in a distal direction from the housing and defining a distal opening at a distal end thereof; a fluid inlet for fluid connection to the cartridge; a conduit extending between the fluid inlet and the distal opening of the housing; and a drive arrangement operable to cause the fluid to be dispensed through the conduit from the inlet, the drive arrangement comprising the carriage.

Optionally, a rotation of the cartridge along its longitudinal axis from the first orientation to the second orientation causes the first protrusion to engage the latch. Optionally, a rotation of the cartridge along its longitudinal axis from the first orientation to the second orientation causes the first protrusion to disengage from the latch. That is, the container may be secured in the carriage when it is rotated into the second orientation.

Optionally, the carriage is slidable in the housing. Optionally, the surgical instrument comprises a plunger that is receivable in the cartridge, such as in a distal end of the cartridge. Optionally the plunger is fixed in the housing. Optionally, the cartridge comprises a connector for connecting the cartridge to a drive element of the drive arrangement, such as via a drive transmission, so that movement of the drive element causes a corresponding movement of the carriage. That is, a movement of the drive element may cause a movement of the carriage relative to the plunger to cause the plunger to slide in the container to dispense the fluid from the container, in use.

Optionally, the connector is caused to engage the drive transmission when the cartridge is secured in the carriage. That is, a rotation of the cartridge to the second orientation may cause the connector to engage the drive element via the drive transmission. In this way, the surgical instrument may only be operated to cause the fluid to be dispensed from the cartridge when the cartridge is properly secured in the carriage. Optionally, the drive transmission comprises a rack and pinion arrangement. Optionally, the connector is urged toward the drive transmission, such as towards the rack, by the first protrusion when the cartridge is in the second orientation. Optionally, the connector and the latch are a part of the same assembly, such as a latch assembly of the carriage.

Optionally, the proximal opening comprises a groove shaped to permit a passage of the first protrusion therethrough when the cartridge is in a first orientation and to prevent the passage of the second protrusion therethrough when the cartridge is in the first orientation. Optionally, the groove is shaped to permit the passage of the second protrusion therethrough when the cartridge is in a second orientation.

Optionally, when the cartridge comprises the second protrusion on an outer surface thereof, the groove in the proximal opening is shaped to prevent the passage of the second protrusion therethrough when the cartridge is in the first orientation. Optionally, the groove is shaped to permit the passage of the second protrusion therethrough when the cartridge is in the second orientation. This ensures that, when a second protrusion is present on the cartridge, the cartridge is only permitted to move further into the housing when it is secured to the carriage in the second orientation. This reduces a risk that the fluid may be prematurely dispensed from the surgical instrument when inserting the cartridge, such as when inserting a new cartridge during a surgical procedure. Optionally, the proximal opening comprises a flexible portion configured to prevent the passage of the second protrusion therethrough into the housing when the cartridge is in the first orientation, but to permit the passage of the second protrusion therethrough out of the housing when the cartridge is in the first orientation. In this way, removal of the cartridge can be achieved by rotating the cartridge to the first orientation.

According to a third aspect there is provided a surgical instrument for dispensing a fluid, the surgical instrument comprising: a housing to be held in the hand; a hollow shaft extending in a distal direction from the housing and defining a distal opening at a distal end thereof; a fluid inlet for fluid connection to a container storing the fluid; a conduit extending between the fluid inlet and the distal opening of the housing; and a drive arrangement operable to cause the fluid to be dispensed through the conduit from the inlet, wherein the drive arrangement comprises a dual pawl ratchet comprising a ratchet wheel and two pawls arranged so that when one of the pawls is engaged to drive one or more teeth of the ratchet wheel, the other pawl is disengaged from any of the teeth of the ratchet wheel.

The pawls of the dual pawl ratchet are staggered so as to provide twice as many engagement positions as a single pawl ratchet having the same number of teeth on its ratchet wheel. That is, the dual pawl ratchet provides finer control of the ratchet wheel without reducing a size of the teeth of the ratchet wheel and/or increasing a number of the teeth of the ratchet wheel. In this way, the dual pawl ratchet may provide improved control of the quantity of fluid dispensed from the surgical instrument, while improving

S

a strength of the drive arrangement and/or allowing a reduction in size of the drive arrangement.

Optionally, the pawls are coupled to each other and are biased towards a first pawl position. Optionally, a movement of the pawls from the first pawl position, in a first ratchet direction, causes the ratchet wheel to move in the first ratchet direction.

Optionally, the ratchet wheel is configured to remain stationary when the pawls return to the first pawl position in a second ratchet direction, opposite to the first ratchet direction. It will be understood that the pawls may slide over the teeth of the ratchet wheel without moving the ratchet wheel, or other elements of the surgical instrument that are driven by the ratchet wheel, when the pawls are moved in the second ratchet direction. In other words, the dual pawl ratchet may be "driven" by moving the pawls in the first ratchet direction and -reset" by moving the pawls back to the first pawl position, in the second ratchet direction.

Optionally, each pawl comprises an engaging portion arranged to engage one or more teeth of the ratchet wheel. Optionally, when the engaging portion of one of the pawls is located in a position to drive one or more teeth of the ratchet wheel, the engaging portion of the other of the pawls is located in-between two or more teeth of the ratchet wheel.

Optionally, the surgical instrument is a surgical instrument for minimally invasive surgery. The hollow shaft can form part of an outer surface of the instrument. It may have a generally elongate shape with a substantially constant cross-sectional shape, for example a circle, a square, a hexagon, an octagon, or any other polygon, regular or otherwise. A generally circular cross-sectional shape can be preferable for minimally invasive surgery to allow the instrument to be rotated easily about the shaft in use and allow a seal to be maintained regardless of the rotation of the instrument.

Optionally, the surgical instrument comprises a reservoir that is fluidically connected, or connectable, to the fluid inlet. The reservoir may be for storing the discrete quantity of fluid before it is dispensed through the outlet. Optionally, the conduit is fluidically connected, or connectable, between the fluid inlet and the distal opening.

The drive arrangement may comprise a rotary indexer configured to index the ratchet wheel so that the ratchet wheel is incrementally rotatable.

Optionally, the rotary indexer is configured to index the ratchet wheel so that the ratchet wheel is incrementally rotatable in the first ratchet direction. That is, the rotary indexer restricts a motion of the ratchet wheel to prevent a continuous rotation of the ratchet wheel in the first ratchet direction. The indexer may provide a resistance to a movement of the ratchet wheel in the second ratchet direction, such as to hold the ratchet wheel stationary as the ratchet is reset.

Optionally, the drive arrangement is operable to cause a discrete quantity of the fluid to be dispensed through the conduit from the inlet. Optionally, rotating the ratchet wheel by a single angular increment in the first rachet direction causes the discrete quantity of the fluid to be dispensed from the surgical instrument. This may provide a greater control over, and confidence in, the quantity of the fluid dispensed by the surgical instrument. The rotary indexer may also provide haptic feedback to a user of the surgical instrument to facilitate an accurate control of the amount of the fluid dispensed during operation.

The rotary indexer may be configured to index the ratchet wheel so that a different one of the pawls is engaged with one or more teeth of the ratchet wheel each time the pawls are returned to a first pawl position after being moved an odd number of increments of the rotary indexer from the first pawl position.

In other words, the angular increments of the rotary indexer correspond to those of the dual pawl ratchet. That is, each time the ratchet wheel is rotated by an odd number of increments of the rotary indexer, and then reset, a different one of the pawls is located to drive the ratchet wheel on a subsequent increment. This may provide an improved control of the amount of fluid dispensable from the surgical instrument.

Optionally, the rotary indexer and ratchet are aligned so that, after dispensing the quantity of the fluid, such as by incrementing the drive arrangement by one or more increments to dispense a discrete quantity of the fluid, at least one of the pawls of the ratchet is engaged with one or more teeth of the ratchet wheel, ready to drive the ratchet wheel in a subsequent increment. That is, when the pawls are reset to the first pawl position after moving one or more increments of the rotary indexer, a distance the pawls need to travel in the first direction until at least one of the pawls engages a tooth of the ratchet wheel is reduced, or minimised, in this way, the discrete quantity of fluid dispensed by the surgical instrument is generally the same at each increment. This improves a reliability of the surgical instrument.

The rotary indexer may comprise an indexer ring comprising plural detents circumferentially spaced around the indexer ring, and at least two protrusions for engaging respective detents of the indexer ring to provide the incremental rotation, wherein the protrusions are arranged so that when one of the protrusions is engaged with a detent, the other protrusion is disengaged from any of the detents.

In other words, the protrusions are offset from one another so as to alternately engage a respective detent as the indexer wheel is rotated, in a similar way to the pawls and teeth of the dual pawl ratchet. In this way, without increasing a number of the detents and/or reducing a size of the detents, the rotary indexer can provide twice as many increments as a rotary indexer having a single protrusion, or a rotary indexer having plural protrusions that simultaneously engage the detents. This may improve a strength of and/or a resistance to rotation provided by, the rotary indexer, and/or allows a reduction in the overall size of the rotary indexer, such as to provide a more compact surgical instrument.

Optionally, the rotary indexer and/or the rachet is configured to rotate in angular increments of up to 10, up to 2°, up to 50, up to 10°, or more than 100. In this way, the discrete quantity of fluid dispensable by the surgical instrument may correspond to the angular increment. Incrementing the drive arrangement by multiple angular increments may cause a corresponding multiple of the discrete quantity of fluid to be dispensed via the conduit. For example, the angular increment may be 5°, so that two increments causes the ratchet to rotate by 10° and causes the surgical instrument to dispense two of the discrete quantities of the fluid, while three angular increments may cause the ratchet to rotate by 15° and cause the surgical instrument to dispense three of the discrete quantities of the fluid, etc. Optionally, the rotary indexer comprises two sets of protrusions, wherein each protrusion in one of the sets of protrusions is arranged to engage a respective detent simultaneously with each other protrusion in that set, and alternately with each protrusion in the other set. Providing plural sets of alternately-engaging protrusions may improve a strength and/or holding capability of the rotary indexer. The protrusions within each set of protrusions may be equally angularly distributed around the indexer ring.

The housing may comprise a proximal opening at a proximal end of the housing, the proximal opening configured to receive the container.

In other words, the container may be a separate insertable and/or removable cartridge storing the fluid, and the surgical instrument may be configured to receive the cartridge. In this way, once the fluid stored in the container has been dispensed, the container can be replaced. More specifically, the container may be removably insertable into the housing via the proximal opening. This may improve an ease of insertion and/or removal of the cartridge, such as when the surgical instrument is in use and the proximal opening is facing a user of the surgical instrument.

Reference to the "distal direction" is a direction away from an operator of the surgical instrument, while reference to the "proximal direction" is a direction towards the operator of the surgical instrument.

Optionally, the proximal opening comprises a groove for receiving a first protrusion on an outer surface of the container. Optionally, the groove is shaped so that the first protrusion can pass through the groove when the cartridge is in a first orientation. Optionally, the groove is shaped so that a second protrusion of the container cannot pass through the groove when the container is in the first orientation. Optionally, the groove is shaped so that, when the cartridge is rotated in the housing into a second orientation, the second protrusion can pass through the groove.

Optionally, the drive arrangement comprises a drive element operable by a user. Optionally, the drive arrangement comprises a carriage. Optionally, the carriage is configured to receive the cartridge. Optionally, the carriage is coupled, or couplable, to the drive element, such as by the dual pawl ratchet, so that moving the drive element in a first element direction causes the carriage to move in a first carriage direction. Optionally, movement of the carriage in the first carriage direction causes the fluid to be dispensed along the conduit, such as from the cartridge.

In this way, a user may cause the quantity of the fluid to be dispensed by operating the drive element. Optionally, the drive element is coupled to the ratchet wheel to cause a rotation of the ratchet wheel. Optionally, the drive element is a trigger, such as a trigger pivotably mounted to the housing. Optionally, the housing comprises a handle to be held in the hand and the trigger is mounted on, or in proximity to, the handle In this way, the trigger is conveniently operable by a user's hand while the user is gripping the handle The handle can be anything suitable for holding by hand. Preferably, the handle is designed for one handed operation of the instrument.

U

Optionally, the drive element is rotatable around an axis of the ratchet. Optionally, the drive element is coupled to the pawls of the dual pawl ratchet so that movement of the drive element from a first element position in the first element direction causes the pawls to move from the first pawl position in the first ratchet direction. In this way, the drive element is used to operate the ratchet. The ratchet may be "reset" by returning the drive element to the first element position, such as under the effect of a biasing element coupled to the drive element and/or to the pawls.

The surgical instrument may comprise a plunger, at least a part of which is receivable in the cartridge, or container, in use, and wherein movement of the carriage is operable to cause the container to advance relative to the plunger.

The container may comprise a plunger seal that is slidable in the container to dispense the fluid stored in the container. Optionally, the plunger seal comprises a plunger seal aperture through which the fluid in the container is dispensable. The proximal end of the plunger may interface with the plunger seal to cause the plunger seal to advance within the container as the container is advanced relative to the plunger. The opening of the plunger may be fluidically couplable with the plunger seal aperture so that the fluid is dispensable through the plunger via the plunger aperture and the opening. Optionally, the plunger head and plunger seal are reciprocally shaped, such as to provide a fluid-tight seal between the plunger head and the plunger seal, such as between the plunger opening and the plunger seal aperture.

The plunger seal aperture may be of a smaller cross-sectional area than the plunger inlet, which may help prevent accidental escape of the fluid in the cartridge, such as during insertion and/or removal of the cartridge.

The plunger seal may comprise a soft, deformable, and/or resilient material, such as silicone or TPE, or any other suitable material. This may allow a seal to be created between the plunger and plunger seal in use.

Alternatively, or in addition, the plunger may sealably engage an interior surface of the container so that movement of the container relative to the plunger causes the fluid to be expelled from the container. This provides a reliable mechanism for dispensing the fluid from the container.

At least a part of the plunger may be arranged to be received in a distal end of the container, in use. The plunger seal may be located at a distal end of the container, and may be configured to move proximally in the container, in use. Ii

That is, the plunger may extend proximally in the housing. A proximal end of the plunger may be configured to connect to a distal end of the container, and/or a part thereof, such as the plunger seal. In this way, the container may be inserted into the housing in a distal direction so that the proximal end of the plunger engages with a distal end of the container, such as the plunger seal. In this way, there may be no need to retract the plunger from the container in order to remove the container from the housing. That is, it may be possible to remove the container from the housing in the proximal direction, through the proximal opening, without the container being obstructed by the presence of the plunger. This may allow the container to be more easily replaced, such as during a surgery, when it would be preferable not to disturb the distal opening of the surgical instrument, particularly if the distal opening is inserted in the body of a patient.

The plunger may comprise an opening for receiving the fluid from the container, such as for interfacing with a corresponding opening on the distal end of the container, or for interfacing directly with the fluid in the container. The opening of the plunger may be fluidically connected or connectable to the fluid inlet of the surgical instrument.

The plunger may be fixed relative to the housing and the carriage may be slidably mounted in the housing to advance the container relative to the plunger upon operation of the carriage In other words, moving the carriage in the first carriage direction may cause the container receivable therein to move in the first carriage direction. This may cause the fixed plunger to extend into the container to cause the fluid to be expelled from the container, such as by moving the plunger seal in the container. The first carriage direction may be a distal direction, so that the container, inserted in a proximal end of the housing, moves into the housing as the carriage moves in the first carriage direction. In this way, moving the carriage in a second carriage direction, opposite to the first carriage direction, may cause the container to move in a proximal direction, out of the housing, so that the container can be more easily removed by a user. Alternatively, the plunger may be coupled to the carriage and the container may be fixed relative to the housing, such as when inserted in the surgical instrument, so that the plunger is movable relative to a stationary container.

The carriage may be releasably couplable to the drive element.

N

That is, the carriage may be movable independently of the drive element and vice-versa. This may allow the container to be more easily removed without operating the drive element.

The carriage may comprise a latch, and a rotation of the container in the carriage may cause a protrusion of the container to engage or disengage the latch to respectively secure the container in or release the container from the carriage.

That is, the container may be securable in the carriage by way of a bayonet fitting, in which the container can be inserted into carriage, such as from the proximal end of the housing, and twisted to engage the carriage. It will be understood that the latch may be any suitable opening, detent, or other engaging element in a wall or other suitable part of the carriage. The turning of the container may be from the first orientation to the second orientation, as described hereinbefore. That is, the container may be secured in the carriage when it is rotated into the second orientation. This ensures that, when a second protrusion is present on the container, the container is only permitted to move further into the housing when it is secured to the carriage in the second orientation. This reduces a risk that the fluid may be prematurely dispensed from the surgical instrument when inserting the container, such as when inserting a new container during a surgical procedure.

Optionally, the container may be twisted in the opposite direction, such as towards the first orientation, to decouple the container from the carriage and permit the cartridge to be removed. This may improve an ease of, and safety associated with, inserting and removing the container, such as to replace the container during a surgical procedure. The carriage may comprise a connector configured to couple the carriage and the drive element when the container is secured in the carriage, and to decouple the carriage and the drive element when the container is not secured in the carriage.

In other words, the drive element may only be operable to move the carriage, and cause the fluid to be dispensed from the container, when the container is secured in the carriage. This may prevent an accidental discharge of the fluid from the container when inserting the container and/or connecting it to the fluid inlet. Moreover, releasing the container from the carriage may permit the carriage to move independently of the drive element, thereby improving an ease of removal of the container as described hereinbefore. The drive arrangement may comprise a rack and pinion arrangement for coupling the carriage and the dual pawl ratchet, and wherein, upon rotation of the container to secure the container in the carriage, the connector is caused to engage the rack. Optionally, a rotation of the container in the carriage causes a protrusion of the container to move the connector in a direction towards or away from the rack, to cause the connector to engage or disengage the rack. Optionally, the connector and the latch are a part of the same assembly, such as a latch assembly of the cartridge, so that a rotation of the container in the carriage causes a protrusion of the container to both: engage or disengage the latch; and cause the connector to engage or disengage the rack.

The engagement of the connector with the rack couples the carriage to the rack, and thereby to the dual pawl ratchet. Optionally, the engagement of the connector with the rack couples the carriage to the drive element via the rack and pinion arrangement and the dual pawl ratchet. In this way, the protrusion of the container serves a dual purpose to simultaneously secure / release the container in the carriage and to cause the carriage to respectively engage / disengage the rack. This provides a reliable mechanism for ensuring the cartridge is fully secure before the surgical instrument is operated.

Optionally, the dual pawl ratchet may be coupled to the pinion, such as directly via the ratchet wheel or indirectly via a gear arrangement. Optionally, there may be more than one pinion wheel, and/or the ratchet may comprise its own pinion wheel coupled to the ratchet wheel. In this way, movement of the dual pawl ratchet, such as by operation of the drive element, causes a corresponding movement of the rack via the pinion(s). The rack and pinion arrangement provides a reliable mechanism for translating the rotational motion of the ratchet to a linear motion of the carriage. The rack also provides a reliable way to engage the carriage with the ratchet.

Optionally, the rack is a continuous rack. That is, the rack may form a loop in the housing, such as by being looped around one or more or pinion gears, pulleys, or pivots, in the housing. Optionally the rack comprises an inner face facing inwardly to the loop, and an outer face facing outwardly from the loop. Optionally, the rack comprises teeth, or grooves, on either or both of the inner and outer faces. The connector of the carriage may be configured to engage one or more teeth or grooves of the rack, such as on the outer face of the rack. The or each pinion may comprise teeth configured to engage reciprocal teeth, or grooves, of the rack, such as on the inner face of the rack. In this way, a rotation of the pinion, such as caused by a corresponding rotation of the dual pawl ratchet, may cause the rack to move around the loop. Alternatively, the rack may be a discontinuous rack configured, for example, to reciprocate in the housing.

Optionally, the connector is biased away from the rack, so that when the container is released from the carriage, the connector decouples the carriage and the rack. In this way, the carriage may be released and the container may be removed without requiring any motion of the rack. The surgical instrument may thereby be more reliable in that no additional mechanism is required for coupling and/or decoupling the rack, the pinion, the dual pawl ratchet and/or the drive element to one another.

The surgical instrument may comprise a carriage biasing element configured to bias the carriage in a second carriage direction, opposite to the first carriage direction.

In this way, the carriage biasing element causes the carriage to move in the second carriage direction when the carriage and the drive element are decoupled, such as when the carriage is decoupled from the rack. As noted hereinbefore, optionally, the first carriage direction is in a distal direction relative to the housing, and the second carriage direction is in a proximal direction relative to the housing. In this way, upon rotation of the container to release the container from the carriage, the carriage may be urged in a proximal direction by the carriage biasing element. This may cause a proximal end of the container to extend from the housing, such as from the proximal opening of the housing, to allow the container to be more easily grasped and removed from the housing.

The drive element may be biased towards a second element direction, opposite to the first element direction.

Optionally, the drive arrangement comprises a spring, or other suitable biasing element, configured to bias the drive element towards the second element direction. In this way, the drive element may be operated in the first element direction to drive the dual pawl ratchet, such as by one or more increments as described hereinbefore, to dispense the fluid from the surgical instrument. The drive element may then be released and urged in the second element direction back to its starting position.

The surgical instrument may comprise an adjuster operable to limit a range of movement of the drive arrangement.

The adjuster may allow a user to control how many multiples of the discrete quantity of fluid are dispensable by moving the ratchet in one direction. For instance, the adjuster may be set so that the ratchet is rotatable in one direction by a certain number of increments as described hereinbefore, such as one, two, three, or more than three increments. If the increments are, for example, 5°, then the adjuster may be set so that the ratchet can be rotated by 5°, 10° or 15°, but by no more than 15°, at least until the ratchet F' is reset. In this way, a reliability and/or safety of the surgical instrument may be improved, such as by ensuring that the quantity of fluid dispensed by the surgical instrument is consistent over multiple operations of the ratchet.

Optionally, the adjuster comprises a tab coupled to move with any suitable part of the drive arrangement described hereinbefore, such as the drive element, one or both pawls, the ratchet wheel, the pinion, the rack and/or the carriage. Optionally, the adjuster comprises a limiter that is movable to one or more positions so that when the drive arrangement, or a part thereof, reaches a predetermined range of motion, the limiter engages the tab to prevent further motion of the drive arrangement. Optionally, the tab comprises plural engaging portions, and the limiter is arranged to engage a respective one of the engaging portions at respective positions of the limiter.

Preferably, the tab is coupled to move with the drive element and/or the dual pawls, so that when the ratchet is "reset", such as by releasing the drive element to return to its starting position, the location of the tab is also reset, so that the drive element can be operated again. That is, the adjuster is configured so that when the drive element is operated in the first element direction described hereinbefore, such as to cause one of the pawls to drive the ratchet wheel, the tab moves towards the limiter. When the tab reaches the limiter, the drive element may no longer be movable in the first element direction. This may advantageously prevent excess fluid being dispensed from the surgical instrument. Then when the drive element is released, such as to return to its starting position in the second element direction, the tab may move away from the limiter to allow the drive element to be operated once more. In this way, the adjuster may be adjustable to set a "dose" of the fluid, which may be a multiple of the discrete quantity of fluid. That is, the discrete quantity of the fluid may be a "part-dose" of the fluid. This may improve an accuracy and level of control achievable by using the surgical instrument.

Optionally, the surgical instrument is the surgical instrument of the second aspect and/or comprises any of the optional features of the surgical instrument of the second aspect. That is, it will be understood that any of the features of the surgical instrument of the second aspect may be combined with any of the features of the third aspect, and vice versa, for example the surgical instrument of the second aspect may comprise the dual pawl ratchet of the surgical instrument of the third aspect.

According to a fourth aspect of the invention, there is provided a surgical instrument comprising the cartridge of the first aspect. The surgical instrument may be the surgical instrument of the second aspect or the third aspect.

According to a fifth aspect, there is provided a method of inserting a cartridge into a surgical instrument, the cartridge configured to store a fluid to be dispensed by the surgical instrument, the cartridge comprising: an elongate cartridge body having a longitudinal axis; a first protrusion and a second protrusion on an outer surface of the cartridge body, wherein the second protrusion is longitudinally and angularly offset from the first protrusion with respect to the longitudinal axis; and the surgical instrument comprising a proximal opening configured to receive the cartridge, the proximal opening comprising a groove, wherein the method comprises inserting the distal end of the cartridge into the proximal opening so that the first protrusion passes through the groove, and urging the cartridge into the housing until the second protrusion abuts the proximal opening.

Optionally, the method comprises, when the second protrusion abuts the proximal opening, rotating the cartridge in a first rotation direction so that the second protrusion is aligned with the groove. Optionally, the cartridge is prevented from rotating until the second protrusion abuts, or is close to, the proximal opening. Optionally, rotating the cartridge causes the first protrusion to engage a carriage of the surgical instrument, to couple the cartridge to the carriage. Optionally, the rotation of the cartridge causes the carriage to engage a drive element of the surgical instrument.

Optionally, the method comprises operating the surgical instrument by moving the drive element to dispense the fluid from the cartridge. Optionally, the method is a method of inserting and/or removing the cartridge from the surgical instrument.

Optionally, the method comprises, such as when the cartridge is ready to be replaced, rotating the cartridge in a second rotation direction, opposite to the first rotation direction, so that the carriage is disengaged from the drive element of the surgical instrument and/or so that the second protrusion is aligned with the groove of the proximal opening.

Optionally, the method comprises moving the cartridge in a proximal direction so that the second protrusion passes through the grooves in the proximal opening. Optionally, the method comprises, such as when the second protrusion is outside the surgical instrument, rotating the cartridge so that the first protrusion is aligned with the groove, and/or so that the first protrusion is disengaged from the carriage of the surgical instrument. Optionally, the method comprises, when the first protrusion is aligned with the groove, removing the cartridge from the surgical instillment through the proximal opening. The method may be repeated to insert a new cartridge into the surgical instrument.

Optionally, the surgical instrument is the surgical instrument of the second aspect or the third aspect and/or comprises any of the optional features of the second aspect or the third aspect Further features and advantages of the invention will become apparent from the following description of preferred embodiments of the invention, given by way of example only, which is made with reference to the accompanying drawings.

Brief Description of the Drawings

Figure 1 shows an example surgical instrument and an example cartridge.

Figure 2A shows a drive arrangement of the surgical instrument of Figure 1 Figure 2B shows an exploded view of the drive arrangement of Figure 2A. Figures 3A and 3B show a dual pawl ratchet of the drive arrangement of Figures 2A and 2B.

Figure 4 shows a part of the drive arrangement of the surgical instrument of Figure Figure 5 shows a rack of the drive arrangement of Figures 2A, 2B and 4.

Figures 6A and 6B show a carriage of the drive arrangement of Figure 4, comprising the container of Figure 1.

Figures 7A, 7B and 7C show an example of an insertion of the cartridge of Figure 1 into the surgical instrument of Figure 1 Figure 8A shows an alternative example of a proximal opening of the surgical instrument of Figure 1.

Figure 8B shows an alternative example of the cartridge for use with a surgical instrument having a proximal opening of Figure 8A.

Figure 9 shows an example method of inserting the cartridge of Figure 1 into the surgical instrument of Figure 1

Detailed Description

An "illustrated example" of the invention is now described with reference to the Figures.

Figure 1 shows a surgical instrument 100 for surgery. Specifically, the surgical instrument 100 is for dispensing a fluid, such as into a body of a patient. The surgical instrument 100 may be used in minimally invasive surgeries such as laparoscopy, arthroscopy and endoscopy, or in "open" surgical procedures.

In some examples, the fluid is a surgical adhesive, a regenerative medicine scaffold, an injectable tissue repair technology, or any other suitable fluid that may be used in a surgery. The fluid is stored in a "cartridge" or "container" 200 that is receivable in the surgical instrument 100. In the illustrated example, the container 200 is a replaceable container 200. In other examples, the container 200 is comprised in the surgical instrument 100, such as fixed in the surgical instrument 100.

The surgical instrument 100 comprises a housing 150, the housing 150 comprising a handle 151 to be held in the hand. The surgical instrument 100 comprises an elongate hollow shaft 120 extending in a distal direction, i.e. in a direction away from an operator of the surgical instrument 100, from the housing 150. The hollow shaft 120 is circular in cross-section, but may be any other suitable cross-sectional shape, such as a square, a hexagon, an octagon, or any other polygon, regular or otherwise.

The hollow shaft 120 defines a distal opening 121 at a distal end thereof The distal end is intended to be inserted into a patient, in use. The surgical instrument 100 is configured to dispense the fluid stored in the container 200, via the hollow shaft, and through the distal opening 121, such as into the patient. In the illustrated example, although not visible, the hollow shaft comprises a shaft conduit passing therethrough, such as a flexible or rigid hose, tube or pipe, through which the fluid is tlowable from the container to the distal opening 121. In other examples, the fluid is flowable within the hollow shaft itself The surgical instrument 100 comprises a drive element 140, which in the illustrated example is a trigger 140, pivotably connected to the housing 150. The drive element 140 is operable to cause the fluid to be dispensed from the container 200, in use.

In other examples, the drive element 140 is any other suitable drive element 140, such as a piston slidably mounted to the housing 150.

An adjuster 180 is provided to limit a range of travel of the drive element 140, such as to limit an amount of the fluid dispensable from the container 200, and thus the surgical instrument 100, when moving the drive element 140 to its maximum range of travel. The adjuster 180 is slidable in the housing 150 to adjust the maximum range of travel of the drive element. In other examples, the adjuster 180 is configured to limit a range of travel of the ratchet wheel or any other suitable part of the drive arrangement 110.

The surgical instrument comprises a proximal opening 170 at a proximal end of the housing 150. (A proximal direction is the direction towards an operator, in use.) The container 200 is receivable in the housing 150 through the proximal opening 170. The container 200 comprises an elongate cartridge body 210. The cartridge body 210 is cylindrical, but may be any other suitable shape, such as a shape having a semi-circular, square, pentagonal, or hexagonal cross-section, or any other polygonal cross-section. The container 200 further comprises, on an outer surface of the cartridge body 210, a distal pair of protrusions 220 at a distal end of the container 200 and an offset pair of protrusions 230, which are each offset from a respective one of the distal protrusions 220. As will be described in more detail hereinafter with reference to Figures 6A and 6B, the distal and offset protrusions restrict a movement of the container 200 through the proximal opening 170 and act to engage the container 200 with a carriage of the surgical instrument.

Not visible in Figure 1, but described later with reference to Figures 4, 6A and 6B, the surgical instrument 100 comprises a carriage 600 into which the container 200 is receivable and a plunger 700 that is receivable into the container 200. The carriage 600 is slidable relative to the housing 150 to cause the container 200 to move linearly relative to a plunger 700, thereby causing the fluid to be dispensed from the container 200. The housing 150 comprises a window 152 through which a location of the carriage 700, and the container 200 located therein, can be determined, to indicate an amount of the fluid remaining in the container 200. In other examples, no such window may be provided. The window also functions as a track to guide the motion of the carriage 600.

Turning now to Figures 2A and 2B, the surgical instrument comprises a drive arrangement 110 for moving the carriage 700 and the container 200, in use. Figure 2A shows an isometric view of the assembled drive arrangement 110, while Figure 2B shows an exploded isometric view of the drive arrangement 110.

The drive arrangement 110 comprises a trigger or drive element 140, which is biased towards a first position by a spring 160. The drive arrangement 110 also comprises a dual pawl ratchet 300 coupled to the drive element 140. Specifically, the dual pawl ratchet 300 comprises a first pawl 310a and a second pawl 310b which are each connected to the drive element 140. In the illustrated example, this is by the first and second pawls 310a, 310b being integrally formed with the drive element 140. In other examples, the first and second pawls 310a, 310b are connected or affixed to the drive element 140 in any other suitable way. The first and second pawls 310a, 310b are biased towards a first pawl position, corresponding to the first position, due to the biasing of the drive element 140 to the first position by the spring 160.

Movement of the drive element 140, which, in the illustrated example, is rotatable about a ratchet axis 301 of the dual pawl ratchet 300, causes the first and second pawls 310a, 310b to move circumferentially around the ratchet axis 301. The dual pawl ratchet 300 comprises a ratchet wheel 320 comprising a plurality of ratchet wheel teeth 321 circumferentially spaced around the ratchet wheel 320. The first and second pawls 310a, 310b are arranged to engage the ratchet wheel teeth 321 to cause the ratchet wheel 320 to rotate around the ratchet axis 301 in a first ratchet direction when the drive element 140 is moved in a first element direction. That is, a movement of the drive element 140 in the first element direction causes the first and second pawls 310a, 310b, and thereby the ratchet wheel 320, to move in the first ratchet direction. In the illustrated example, the first element direction (and the first ratchet direction) is anti-clockwise when viewed as depicted in Figure 2A.

The ratchet teeth 321 and first and second pawls 310a, 310b are angled so that, when the drive element 140 is moved in a second element direction, opposite to the first element direction, the first and second pawls 310a, 310b are able to slide in a second ratchet direction, opposite to the first ratchet direction, over the ratchet teeth 321, while the ratchet wheel 320 remains stationary. That is, the dual pawl ratchet 300 can be rotated by moving the first and second pawls 310a, 310b in the first ratchet direction, such as by gripping the trigger 140, and reset by moving the first and second pawls 310a, 310b to the first pawl position, in the second ratchet direction, such by releasing the trigger 140.

The dual pawl ratchet 300 will be described in more detail hereinafter with reference to Figures 3A and 3B.

The drive arrangement comprises a rotary indexer 400 coupled to the dual pawl ratchet 300 and configured to index the ratchet wheel 320 so that the ratchet wheel 320 is incrementally rotatable in the first ratchet direction. That is, the rotary indexer is configured to restrict movement of the ratchet wheel 320 in the first ratchet direction to discrete angular increments. The indexer 400 is also configured to provide a resistance to a movement of the ratchet wheel 320 in the second ratchet direction, so that the ratchet can be reset by movement of the first and second pawls 310a, 310b in the second ratchet direction while the ratchet wheel 320 is stationary.

Incrementing the dual pawl ratchet 300 by a single angular increment causes a discrete quantity of the fluid to be dispensed. In some examples, the angular increments provided by the rotary indexer are up to 10, up to 2°, up to 50, up to 10° or more than 100 In the illustrated example, the indexer is configured to allow the ratchet wheel 320 to rotate in angular increments of 50, so that two increments of the rotary indexer causes the ratchet wheel 320 to rotate by 10°. The rotary indexer will be described in more detail hereinafter with reference to Figures 3A and 3B.

The dual pawl ratchet 300, and specifically the ratchet wheel 320, is coupled to a drive transmission 500 for transmitting a motion of the ratchet wheel 320 to the carriage 600, in use. The drive transmission 500 of the illustrated example comprises a rack and pinion arrangement 500 comprising a first pinion gear 520a drivable by the ratchet wheel 320, a second pinion gear 520b that is drivable by the first pinion gear 520a, and a rack 510, or belt 510, that is coupled to pinion teeth 521b of the second pinion gear 520b to be driven by the second pinion gear.

More specifically, as best shown in Figure 2B, the ratchet wheel 320 is a compound gear comprising a hub 322, the ratchet wheel teeth 321 on a first axial side of the hub 322, and a set of intermediate teeth 323 on an opposite axial side of the hub 322.

The intermediate teeth 323 engage outer teeth 521a of the first pinion gear 520a to drive the first pinion gear 520a. The first pinion gear 520a also comprises inner teeth 522, which engage the pinion teeth 52 lb of the second pinion gear 520b to drive the second pinion gear 520b, and subsequently the rack 510. It will be understood that, in other examples, any other suitable combination of gears may be used to convert a rotational movement of the ratchet wheel 320 into a linear motion of the rack 510.

The carriage 600 is couplable to the rack 510, as will be described in more detail later with reference to Figures 6A and 6B. In this way, the drive transmission 500 converts a rotational movement of the ratchet wheel 320 into a linear motion of the carriage 600 when coupled to the rack 510.

The rack 510 is a continuous rack 510 forming a loop in the housing, so that rotation of the ratchet wheel 320 in the first ratchet direction causes the rack 510 to move in a first rack direction around the loop. The rack 510 is looped around the second pinion gear and, in some examples, also around one or more idle gears, guiding ribs, pivots and/or pulleys (not shown) within the housing 150, such as to constrain and/or guide the rack 510. In other examples, the drive transmission 500 comprises plural pinion gears, such as plural second pinion gears 520b, each being coupled to drive and/or constrain a motion of the rack 510. In other examples, the rack 510 is discontinuous, and is able to reciprocate back and forth in the housing. In some such examples, the rack 510 is flexible, and is able to conform to the shape of the housing 510, thereby to reduce a size of the housing 150. In other such examples, the rack 510 is rigid. In other examples, the drive transmission 500 is any other suitable transmission for converting a rotational movement of the dual pawl ratchet 300 to a linear movement of the carriage 600.

Figure 2A also show the adjuster 180, which comprises a limiter 181 that is slidably coupled to the housing 150, and a tab 182 which is coupled to move with the drive element 140. The tab 182 specifically extends from the drive element 140 in a direction substantially orthogonal to the ratchet axis 301, though in other examples the tab 182 may extend in any other suitable direction. The tab 182 and limiter 181 are arranged so that when the drive arrangement 110, or a part thereof, such as the drive element 140 in the illustrated example, reaches a predetermined range of motion in the first element direction, the tab 182 engages the limiter 181 to prevent further movement of the drive element 140 in the first element direction. The tab 182 comprises plural engaging portions, which in the illustrated example form a stepped structure. The different engaging portions of the tab 182 are shaped to provide different ranges of movement before the respective engaging portion engages with the limiter 181. The limiter 181 is moveable to engage a respective one of the engaging portions at a respective position of the limiter 181. In this way, the maximum range of movement of the drive element 140 in the first element direction, such as a maximum number of increments of the rotary indexer 400, can be adjusted by moving the limiter 181. The adjuster is therefore adjustable to set a maximum volume of the fluid dispensed.

It will be understood that the adjuster 180 may be provided in any suitable way to limit a maximum volume of the fluid dispensable from the surgical instrument 100 from a single operation of the drive element 140. For instance, the tab may be configured to move with any other suitable "resettable" element of the drive arrangement 110 that can be returned to an initial position following dispensation of fluid from the surgical instrument 100, such as the carriage 600, to restrict a motion of that element. In other examples, the limiter is pivotably coupled to the housing. In other examples, the adjuster is not present.

The operation of the dual pawl ratchet 300 and the rotary indexer will now be described in more detail with reference to Figures 3A and 3B. Figure 3A shows the dual pawl ratchet 300 and the rotary indexer 400 at a first ratchet position of the ratchet wheel 320. The drive element in Figure 3A is located in the first element position. As highlighted in Figure 3A, the first and second pawls 310a, 310b are angularly offset from each other so as to alternately engage the ratchet teeth 321. That is, only one of the first and second pawls 310a, 310b is located to drive a ratchet tooth 321 of the ratchet wheel 320 at any given time. In Figure 3A, it is the second pawl 310b that is "engaged" to drive a ratchet tooth 320, while the first pawl 310a is located in-between two ratchet teeth 321. The first pawl 310a is, in other words, "disengaged" from any of the teeth 320 of the ratchet wheel 320 and is unable to drive the ratchet wheel 320 from the first ratchet position.

Figure 3B shows the dual pawl ratchet 300 and the rotary indexer 400 in a second ratchet position of the ratchet wheel 320. The second position is achieved by operating the drive element 140 to move the ratchet wheel 320 by a single increment (or an odd number of increments) of the rotational indexer 400. In Figure 3B, the dual pawl ratchet 300 has been "reset" by releasing the drive element back to the first element position. It can be seen that, when the ratchet wheel 320 is in the second ratchet position, with the first and second pawls 310a, 310b in the first pawl position, the first pawl 310a is now engaged to drive a ratchet tooth 321 of the ratchet wheel 320, and the second pawl 310b is disengaged from any of the teeth 321 of the ratchet wheel 320. Moving the ratchet wheel 320 by further increments of the rotary indexer 310 will cause the ratchet wheel 320 to alternate between the first and second ratchet positions. Resetting the dual pawl ratchet 300 when the ratchet wheel 320 is in the first position will cause the second pawl 310b to be engaged to drive the ratchet wheel, while resetting the dual pawl ratchet 300 when the ratchet wheel 320 is in the second ratchet position will cause the first pawl 310a to be engaged to drive the ratchet wheel 320.

In other words, more generally, after incrementing the ratchet wheel 320 by an odd number of increments of the rotary indexer 400, and moving the first and second pawls 310a, 310b back to the first pawl position, a different one of the pawls 310a, 310b will be engaged to drive the ratchet wheel 320. Providing the two pawls 320a, 310b in such a staggered fashion has the same effect as doubling the number of teeth of a corresponding single-pawl ratchet. That is, the dual pawl ratchet 300 provides finer control of the ratchet wheel 320 without reducing a size of the ratchet teeth 321 of the ratchet wheel 320 and/or increasing a number of the ratchet teeth 321 of the ratchet wheel 320.

Returning now to Figure 3A, when the ratchet wheel 320 is in the first ratchet position, the rotary indexer 400 is in a first indexer position. The rotary indexer comprises an indexer ring 410 comprising a plurality of detents 411 circumferentially spaced around the indexer ring 410. The indexer ring 410 in the illustrated example is a part of the ratchet wheel 320. The detents 411 are circumferentially spaced around an interior surface of the ratchet wheel 320, while the ratchet teeth 321 are circumferentially spaced around an exterior surface of the ratchet wheel 320. In other examples, the indexer ring 410 may be separate and coupled to the ratchet wheel 320. In some such examples, the detents 411 are arranged on an exterior surface of the indexer ring 410.

The rotary indexer 400 also comprises a first set of protrusions 421a and a second set of protrusions 421b. Each set of protrusions 421a, 421b comprises three protrusions. Each of the protrusions 421 in the first and second sets of protrusions 421a, 421b is located to engage a respective detent 411 of the indexer ring. The first and second sets of protrusions 421a, 421b are here provided on a ring 420 that is located inwardly of the indexer ring 410 (i.e. inwardly of a part of the ratchet wheel 320) and fixed relative to the housing 150.

The first and second sets of protrusions 42 la, 42 lb are offset from each other in a similar way to the first and second pawls 310a, 310b, so that a rotation of the indexer ring 410 as the ratchet wheel 320 rotates causes the first and second sets of protrusions 421a, 421b to alternately engage the detents 411. In the example shown in Figure 3A, in the first ratchet position, the three protrusions of the first set of protrusions 421a, which are highlighted with black dots, are engaged with respective detents 411, while the three protrusions of the second set of protrusions 421b are disengaged from any detents 411. Specifically, in the first ratchet position, each protrusion in the second set of protrusions 421b is located between a respective pair of detents 411 of the indexer ring 410. In this example, the first and second sets of protrusions are offset by 5° around the circumference and the detents are spaced by 100 around the circumference, so that altogether there are 36 detents.

When the ratchet wheel 320 is moved by a single increment (or an odd number of increments) to the second ratchet position, as shown in Figure 3B, then the three protrusions of the second set of protrusions 421b, which are highlighted with black dots, are instead engaged with respective detents 411, while the three protrusions in the first set of protrusions 42 la are each disengaged from any detents 411. In this way the number of indexed positions is double that of the number of detents, 72 in this example, corresponding to a 50 rotation.

As well as indexing, the rotary indexer 300 provides haptic feedback to a user whenever the ratchet wheel 320 is moved by an increment. This allows an operator of the surgical instrument to reliably move the drive element by a select number of increments, and thereby accurately control the quantity of the fluid dispensed from the surgical instrument, in use. This indexing is independent of the limiter 180, so that the limiter provides a maximum volume that can be dispensed, while the indexing provides accurate dispensing of an amount less than the maximum.

In other examples, each of the first and second pawls 310a, 310b is configured to engage plural respective teeth 421 of the ratchet gear 320 simultaneously. This may improve a strength of the dual pawl ratchet 300. In other examples, there may be more than two pawls 310a, 310b, each of the pawls 310a, 310b staggered with respect to each of the other pawls 310a, 310b, thereby to provide even finer control of the ratchet 300, or to permit larger teeth 321 to be used.

In other examples, the detents 411 and protrusions 421a, 421b are provided in any other suitable way. For example, the detents 411 may be provided on an exterior surface of the indexer ring 410, and the protrusions 421a, 421b may be provided outside the indexer ring 410. In some examples, the indexer ring 410 is fixed relative to the housing and the protrusions 421a, 421b are fixed to the ratchet wheel 320 to rotate with the ratchet wheel 320. In some examples, the detents are provided on an exterior surface of the indexer ring 410, and the protrusions are exterior to the indexer ring 410. In some examples, the protrusions may instead be provided on the indexer ring 410. That is, the indexer ring 410 may comprise plural circumferentially spaced protrusions on an interior and/or exterior surface thereof the protrusions configured to engage detents to provide the functionality described hereinbefore.

In other examples, there are any number of protrusions in each set of protrusions 421a, 421b, such as only one protrusion, two protrusions, or more than three protrusions. Increasing a number of protrusions may improve a strength of the rotary indexer 400 and/or a capacity of the rotary indexer 400 to hold the ratchet wheel 320 in place as the ratchet 300 is reset. In some examples, there are any number of sets, such as only one set or more than two sets. Reducing a number of sets of the protrusions may require an increase in the number of detents and/or a reduction in the sizes of the detents and protrusions. Therefore, providing two or more sets of protrusions may increase the strength and/or holding capacity of the rotary indexer.

Turning now to Figure 4, shown is a cross-sectional view of part of the surgical instrument 100. The drive transmission is visible, as well as the carriage 600 and plunger 700 referred to hereinbefore.

The carriage 600 comprises a carriage wall 610 defining a carriage cavity 630 therein. The carriage 600 is configured to receive the container 200 in the carriage cavity 630 in use, specifically by inserting a distal end of the container 200 through the proximal opening 170 and into the carriage 600. The carriage 600 is slidably movable in the housing 150, such as by the carriage 600, or the carriage wall 610, being mounted on tracks (not shown) in the housing 150. Specifically, the carriage 600 is movable in a first carriage direction, which is a distal direction, and a second carriage direction, which is a proximal direction towards the proximal opening 170. The carriage 600 is urged in the second carriage direction by a carriage spring 750, which is fixed relative to the housing and is coupled to a distal mounting portion 640 of the carriage 600. It will be understood that the carriage spring 750 may instead be any other suitable biasing element capable of biasing the carriage 600 in the second carriage direction.

The plunger 700 comprises a plunger stem 710 which extends into the carriage 600 so that the carriage 600 can slide along the plunger stem 710. The plunger 700 comprises a plunger head 720 located at a proximal end of the plunger stem 710. In the illustrated example, the plunger head 720 is located in the carriage cavity 630, but in other examples, the plunger stem 710 and/or the plunger head 720 may remain external to the carriage 600 when the carriage 600 is adjacent to the proximal opening, and may extend into the carriage 600 when the carriage 600 is moved distally, in the first carriage direction. In the illustrated example, the carriage spring 750 is concentrically located around the plunger stem 710.

The plunger head 620 is arranged to be receivable in the container 200 when the container is received in the carriage 600. Specifically, the container 200 comprises a distal opening 260 (best seen in Figures GA and 6B) at a distal end of the container 200, configured to receive the plunger head 720 when the container 600 is received in the carriage 600. The plunger head 720 comprises a plunger inlet 740 configured to interface with an internal reservoir (not shown) of the container 200 storing the fluid to be dispensed. The plunger inlet 740 is fluidically connected to the distal opening 121 of the surgical instrument 100 by a plunger conduit 730 defined within the plunger stem 710. In the illustrated example, the plunger stem 710 is an extension of the hollow shaft 120 into the housing, and the plunger conduit 730 is an extension of the shaft conduit between the plunger inlet 740 and the distal opening 121. In other examples, the plunger stem 710 is separate to the hollow shaft. In some such examples, the plunger conduit 730 may still be a part of the shaft conduit. In other examples, the plunger conduit 730 is fluidically connected, or connectable, to the hollow shaft 120, and/or to the shaft conduit located in the hollow shaft 120. In other examples not shown here, the surgical instrument 100 comprises a reservoir for storing, such as temporarily storing, the fluid in the housing 150. The reservoir may be fluidically connected, or connectable, to the plunger inlet 740 to receive the fluid from the container 200. The reservoir may also be fluidically connected, or connectable, to the distal opening 121, to provide the fluid to be dispensed from the distal opening 121.

As will be described in more detail later with reference to Figures GA and 6B, the carriage 600 comprises first and second engaging portions 620a, 620b, or latches, and the container 200 comprises the distal and offset pairs of protrusions 220, 230. The distal protrusions are each configured to engage a respective one of the first and second engaging portions 620a, 620b of the carriage GOO to secure the container 200 in the carriage 600. As will also be described hereinafter with reference to Figures 6A and 6B, the carriage 600 also comprises a connector 650 configured to couple the carriage 600 to the drive transmission 500, specifically to the rack 510, when the container 200 is secured in the carriage 600. The connector 650 is also configured to decouple the carriage 600 from the rack 510 when the container 200 is not secured in the carriage 600.

Turning now to Figures, shown is a schematic isometric view of the rack 510 of the illustrated example. The rack 510 comprises a first set of grooves 512a on an outer surface 511a thereof (i.e. on an outer surface of the loop formed by the rack 510), configured to engage respective engaging portions of the connector 650. The rack 510 also comprises a second set of grooves 512b on an inner surface 511b thereof, configured to engage corresponding pinion teeth 521b of the second pinion gear 520b. The rack 510 of the present example is made from Polypropylene (PP). In other examples, the rack 510 may be made from any other suitable material, such as Polyethylene (PE) or a Thermoplastic Elastomer (TPE).

Figures GA and 6B show the carriage 600 of Figure 4 when the container 200 is inserted into the carriage 600. The container body 210 interfaces with the carriage wall 610 to locate the container 200 in the carriage cavity 630. The container 200 comprises a longitudinal axis 250 and is shown in Figure 6A in a first rotational orientation in the carriage 600 with respect to the longitudinal axis 250. The distal pair of protrusions 220 comprises a first distal protrusion 220a and a second distal protrusion 220b located on an opposite side of the container body 210 to the first distal protrusion. In the first orientation, neither of the first and second distal protrusions 220a, 220b are engaged to secure the container 200 in the carriage 600. This permits the container 200 to slide relative to the carriage 200, such as to allow the container 200 to be removed from the carriage 600 and the housing 150 via the proximal opening 170.

Rotating the cartridge along its longitudinal axis 250, as shown by the arrow in Figure 6B, causes the first distal protrusion 220a to engage the first engaging portion 620a of the carriage 600 and the second distal protrusion 220b to engage the second engaging portion 620b of the carriage 600. This causes the container 200 to be secured to the carriage 600, so that the container 200 can move with the carriage 600 relative to the plunger 700. In other words, the container 200 is securable in the carriage 600 by way of a bayonet fitting, in which the container 200 can be inserted into carriage 600, specifically through the proximal opening 170 of the housing 150, and twisted to engage the carriage 600. The engaging portions 620a, 620b of the carriage may take any suitable form, such as depending on the shape of the first and second distal protrusions. For example, the engaging portions 620a, 620 of the carriage 600 can be any suitable opening, detent, or other engaging element in the carriage wall 610 or other suitable part of the carriage 600.

As is also shown in Figure 6B, when the container 200 is in the second orientation, the second distal protrusion 620b causes the connector 650 to engage with the rack 510. Specifically, the distal protrusion 620b engages with, and urges the connector 650 towards the rack 510 so that engaging portions of the connector 650 engage with the grooves 512a in the upper surface 510 of the rack. In this way, the distal protrusions 220 of the container 200 serve a dual purpose to simultaneously secure / release the container 200 in the carriage 600 and to cause the carriage 600 to respectively engage / disengage the rack 510.

It will be understood that operation of the drive element 140 when the container 200 is secured in the carriage 600 will cause the container 200 to move distally into the housing and onto the plunger 700. The relative movement of the container 200 and the plunger 700 will cause the fluid in the container 200 to be dispensed through the plunger conduit 730 and, ultimately, out through the distal opening 121 of the surgical instrument 100. The rotary indexer 400 provides a holding force to prevent the ratchet wheel 320 from rotating in the second ratchet direction, such as under the action of the carriage spring 750 when the carriage 600 is engaged with the rack 510. In this way, when the carriage 600 is engaged to the rack, the container 200 is always moved distally in the first carriage direction, into the housing 150. The dual pawl ratchet 300 allows the drive element 140 to be released without the carriage 600 and cartridge 200 moving proximally in the second carriage direction. In this way, the plunger 700 is prevented from receding from the container 200 during operation, at least until the carriage 600 is released from the rack 510. This ensures a flow of the fluid from the surgical instrument 100 is accurate

and predictable.

When the container 200 has been driven in the first carriage direction and is empty of the fluid, the container 200 can be twisted in a direction opposite to that shown in Figure 6B, towards the first orientation, to disengage the distal protrusions 220a, 220b from the respective engaging portions 620a, 620b of the carriage 600, and to cause the connector 650 to disengage from the rack 510. In this way, under the action of the carriage spring 750, the carriage 600 and the container 200 are caused to move proximally in the second carriage direction. This may cause a proximal end of the container 200 to extend from the proximal opening 170 to be more easily grasped and removed by an operator of the surgical instrument. If it is then required to dispense more fluid using the surgical instrument 100, a new container 200 may be inserted and the process repeated.

In the illustrated example, the container 200 comprises a plunger seal 240 that is slidable within the container 200, and specifically within the reservoir storing the fluid within the container 200. The plunger seal 240 comprises a plunger seal aperture 241 through which fluid from the container is flowable as the plunger seal 240 is advanced relative to the container 200. The plunger head 720 is configured to engage the plunger seal 240 so that the plunger inlet 740 is fluidi catty coupled with the plunger seal aperture 241. In this way, movement of the container 200 relative to the plunger 750 causes the plunger seal 240 to be moved proximally relative to the container 200, thereby to cause the fluid in the container 200 to be dispensed through the plunger conduit 730, specifically via the plunger seal aperture 241 and the plunger inlet 740. In the illustrated example, the plunger head 720 and plunger seal 240 are reciprocally shaped to facilitate engagement thereof, though in other examples this may not be the case.

In other examples, the plunger head 740 comprises the plunger seal 240, so that the plunger head 740. In other examples, there is no plunger seal 240, and the distal end of the container 200 comprises a valve (not shown) configured to seal the fluid in the container 200, and to allow the plunger head 720 to be inserted into the container 200 through the valve. In this way, the valve forms a seal around the plunger head 720 and/or the plunger stem. In other examples, the distal end comprises a frangible portion for forming a seal that is broken when the plunger head 720 is inserted into the container 200. It will be understood that the plunger head 720 and/or container 200 may be configured in any other suitable way to facilitate a fluid coupling of the plunger conduit 730 with the fluid stored in the container 200.

Figures 7A to 7C show an example of an operator inserting the container 200 into the housing. As can be seen most clearly in Figure 7A, the container comprises the first and second distal protrusions 220a, 220b, and first and second offset protrusions 230a, 230b. The first and second offset protrusions are each longitudinally and angularly spaced, or offset, from the respective first and second distal protrusions 220a, 220b with respect to the longitudinal axis. The proximal opening 170 of the surgical instrument 100 comprises first and second opposing grooves 171a, 171 b shaped to receive the first and second distal protrusions 220a, 220b of the container 200 when the container 200 is in the first orientation discussed hereinbefore. That is, as shown in Figure 7A, the shape and location of the first and second grooves 171a, 171b correspond to the shape and location of the first and second distal protrusions 220a, 220b.

As shown in Figure 7B, the first and second offset protrusions 230a, 230b are longitudinally and angularly offset from the first and second distal protrusions 220a, 220b so as to engage the proximal opening 170 when the distal end of the cartridge 200 is inserted into the surgical instrument 100 in the first orientation. That is, when inserting the container 200 into the housing 150 in the direction and orientation shown in Figure 7A, eventually the second protrusions will abut the housing 150 in proximity to the proximal opening 170 to prevent the container 200 being inserted any further.

Specifically, the first and second offset protrusions 230a, 230b are proximally, i.e. longitudinally, spaced from the first and second distal protrusions 220a, 220b by an amount such that the distal end of the container 200, or cartridge 200, is in a first dispensing position in the surgical instrument 100 when the first and second offset protrusions 230a, 230b engage the proximal opening 170. That is, the distal end of the container 200 is in the first dispensing position in Figure 7B.

The first dispensing position is such that the proximal plunger head 720 is engaged with, and/or inserted into the container 200 to a suitable extent to "prime" the container 200 and/or the surgical instrument 100, such as to prime the plunger conduit 730 and/or the hollow shaft 120, or shaft conduit. In other words, the first dispensing position of the illustrated example corresponds to a position at which the plunger 700, or a part thereof, such as the plunger head 720, extends into the container 200 by a predetermined amount, such as to prime the surgical instrument 100, and specifically the plunger conduit 730, and/or the container 200 for use. It will be understood that when the surgical instrument 100 is suitably primed, at least some of the fluid stored in the container 200 may be passed at least partly through the plunger conduit 730 and/or the hollow shaft 120, or shaft conduit, towards the distal opening. In some examples, when the surgical instrument 100 is primed, the plunger conduit 730 and/or hollow shaft 120 is filled with fluid up to, or close to, the distal opening 121, so that the fluid can be dispensed from the surgical instrument 100 on first operation of the drive element 140 following insertion of the container 200. In some examples, the container 200 comprises an internal reservoir for storing the fluid to be dispensed. The internal reservoir is entirely filled with the fluid, but may alternatively comprise a gas in addition to the fluid to be dispensed. In some such examples, priming the container 200 comprises expelling some or all of the gas in the container.

In other examples, it may be necessary to operate the drive element 140 by one or more increments of the rotary indexer to move the fluid toward the distal opening 121.

In any event, providing the second protrusion prevents the cartridge 200 from being inserted too far into the housing 150 to ensure the cartridge 200 is properly positioned in the surgical instrument 100 before use, such as to avoid a premature dispensation of the fluid from the surgical instrument 100.

The distal protrusions 220a, 220b and offset protrusions 230a, 230b are located so that the container 200 can only be rotated to the second orientation when the first and second offset protrusions engage, or abut, the proximal opening 170. In some examples, this is by the housing 150 and/or carriage 600 comprising grooves and/or tracks, such as extending from the first and second grooves 171a, 171b of the proximal opening 170 into the housing 150, and/or along the carriage 600, to slidably engage with the first and second distal protrusions 220a, 220b to prevent the container 200 from rotating This ensures that the container 200 is properly inserted into the surgical instrument 100, and/or that the surgical instrument 100 is properly primed, before is the cartridge 200 is rotated into the second orientation and coupled to the rack 510 via the carriage 600. In other examples, no such grooves and/or tracks extending into the housing 150 and/or carriage 600 are present.

As shown in Figure 7C, the first and second offset protrusions 230a, 230b are arranged relative to the respective first and second distal protrusions 220a, 220b, and the first and second grooves 171a, 171b of the proximal opening 170 are so shaped that, when the container 200 is in the second orientation, the first and second offset protrusions 230a, 230b can pass through the respective first and second grooves 171a, 171b, That is, once the container 200 has been rotated into the second orientation, i.e. to couple the container 200 to the carriage 600 and the rack 510, the surgical instrument 100 can then be operated to move the container 200 distally into the housing 150 relative to the plunger 700 to cause the fluid to be dispensed from the container 200.

The first and second offset protrusions 230a, 230b are shaped so as to be able to pass through the respective first and second grooves 171a, 171b when the container 200 is in a third orientation, between the first and second orientations, in which the first and second distal protrusions 220a, 220b are located so as not to cause the connector 650 to engage the rack 510. In this way, when the first and second offset protrusions 230a, 230b are inside the housing 150, such as following an operation of the surgical instrument 100, the carriage 600 and container 200 may be disengaged from the rack 510 and moved proximally by the carriage spring 750 without the first and second offset protrusions 230a, 230b catching the proximal opening 170. In some examples, the housing 150 and/or carriage 600 comprises features, such as tracks, for engaging with the first and/or second offset protrusions 230a, 230b to prevent the container 200 from being rotated into the first orientation. That is, the tracks may constrain the container to being in the second or the third orientation when the first and second offset protrusions 230a, 230b are located in the housing 150. In some examples, in the third orientation, the first and second distal protrusions 220a, 220b are engaged with the first and second engaging portions 620a, 620b of the carriage 600. In other examples, in the third orientation, the first and second distal protrusions 220a, 220b are disengaged from the carriage 600.

Figure 8A shows an alternative example of the proximal opening 170 absent the container 200, for clarity. The construction of this example is the same as that described above with respect to Figure 1, but, in addition to the first and second opposing grooves 171a, 171b, the proximal opening 170 comprises first and second flexible portions 172a, 172b. The first and second flexible portions 172a, 172b are located so that the first and second offset protrusions 230a, 230b are aligned with the first and second flexible portions 172a, 172b when the container 200 is in the first orientation. The first and second flexible portions 172a, 172b are configured so that the first and second offset protrusions 230a, 230b are prevented from moving in the distal direction past the first and second flexible portions 172a, 172b, but are permitted to move in the proximal direction past the first and second flexible portions 172a, 172b. That is, the first and second flexible portions 172a, 172b prevent insertion of the container 200 past the first and second offset protrusions 230a, 230b when the container 200 is in the first orientation. Then, following dispensation of the fluid from the container 200, the container 200 can be rotated from the second orientation into the first orientation to disengage the container 200 from the carriage 600. The first and second flexible portions 172a, 172b then permit passage of the first and second offset protrusions 230a, 230b in the proximal direction, such as by the first and second flexible portions 172a, 172b deforming, to allow the container 200 to be ejected from the housing 100 in the first orientation.

Figure 8B shows an alternative example of the container 200 for use with the example of Figure 8A in which a proximal portion of the respective first and second offset protrusions 230a, 230b comprises a ramp 23 la, 231b, or slope to facilitate removal of the cartridge 200 past the first and second flexible portions 172a, 172b in the first orientation.

The first and second flexible portions 172a, 172b may comprise a corresponding ramp on a distal portion, to engage the ramp 231a, 231b.

In some examples, the second orientation comprises a rotation of the container 200 from the first orientation by an angle of up to 20°, up to 45°, up to 90°, or up to 180°. In the illustrated example, the second orientation is achieved by rotating the container 200 from the first orientation by an angle of 900. The rotation from the first to the second orientation shown is a clockwise rotation when viewed along the longitudinal axis 2 from the proximal end. In other examples, the rotation from the first orientation to the second orientation is in an anti-clockwise direction when viewed along the longitudinal axis from the proximal end.

In the illustrated example, the first and second offset protrusions 230a, 230 are angularly offset from the respective first and second distal protrusions 220a, 220b by 900 to allow the container 200 to rotate by 90° between the first and second orientations. In other examples, the first and second offset protrusions 230a, 230b, and/or parts thereof, are angularly offset by any other suitable amount, such as up to 20°, up to 45°, up to 90°, or up to 180°. In the illustrated example, the first and second offset protrusions 230a, 230b are longitudinally offset from the respective first and second distal protrusions by 20mm. In other examples, the second the first and second offset protrusions 230a, 230b are longitudinally offset from the respective first and second distal protrusions by any other suitable amount such as up to 15mm, up to 25mm, or up to 40mm.

It will be understood that, in other examples, more than two distal protrusions 220 may be provided, or only one distal protrusion 220 may be provided. Moreover, in other examples, more than two offset protrusions 230, or only one offset protrusion 230 may be provided. Similarly, there may be more than two or only one groove 171 in the proximal opening 170. Providing a pair of opposing distal protrusions 220a, 220b and a pair of opposing proximal protrusions 230a, 230b, instead of say, one of each, may ensure that any forces applied to the container 200 such as due to the engagement of the distal protrusions 220a, 220b in the carriage 600 and/or due to the abutment of the offset protrusions 220a, 220b with the proximal opening 170, are symmetrical. Providing plural distal and offset protrusions 220, 230 may also improve an alignment of the container 200 provided by the respective protrusions.

Finally, Figure 9 shows an example method 800 of inserting the cartridge 200 into the surgical instrument. The method 800 comprises inserting 810 the distal end of the cartridge 200 into the proximal opening 170 so that the first and second distal protrusions pass through the respective first and second grooves 171a, 171b in the proximal opening 170, and urging 820 the cartridge into the housing 150 until the first and second offset protrusions 230a, 230b abut the proximal opening 170, and/or respective first and second flexible portions 172a, 172b thereof In some examples, the method 800 further comprises, when the first and second offset protrusions 230a, 230b abut the proximal opening 170, rotating 830 the cartridge to the second orientation so that the first and second offset protrusions 230a, 230b are aligned with the respective first and second grooves 170a, 170b, and/or so that the first and second distal protrusions 220a, 220b are engaged with the carriage 600. In some examples, the method 800 comprises operating 830 the surgical instrument 100 by moving the drive element 140 to dispense the fluid from the container 200.

In some examples, the method 800 comprises, such as when the cartridge is ready to be replaced, rotating 840 the container 200 to the first orientation, or a third orientation, so that the carriage 600 is disengaged from the rack 510, as described above. In some examples, the method 800 comprises moving 850 the container 200 proximally so that the first and second offset protrusions 230a, 230b pass back through the respective first and second grooves 171a, 171b, or through the first and second flexible portions 172a, 172b described above. In some examples the method 800 comprises, such as when the first and second offset protrusions 230a, 230b are outside the housing 150, rotating 860 the container 200 into the first orientation, so that the first and second distal protrusions 220a, 220b are aligned with the respective first and second grooves 171a, 17 lb, and/or so that the first and second distal protrusions 220a, 220b are disengaged from the carriage 600. In some examples, the method 800 comprises, when the container 200 is in the first orientation, removing 870 the container 200 from the surgical instrument 100 through the proximal opening 170. The method 800 can be repeated to insert a new container 200.

The above embodiments are to be understood as illustrative examples of the invention only. It is to be understood that any feature described in relation to any one example may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. For example, the surgical instalment 100 may be provided with the dual pawl ratchet 300 arrangement but without a replaceable cartridge 200. In other examples, the surgical instrument 100 may be provided with the removable cartridge 200 comprising the distal and offset protrusions but using only a single pawl ratchet or other drive arrangement. Other examples are envisaged. Furthermore, modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims 3 9

Claims

CLAIMSA cartridge for a surgical instrument, the cartridge configured to store a fluid to be dispensed by the surgical instrument, the cartridge comprising: an elongate cartridge body having a longitudinal axis; a cartridge reservoir in the cartridge body for storing the fluid; and a first protrusion and a second protrusion on an outer surface of the cartridge body, wherein the second protrusion is longitudinally and angularly offset from the first protrusion with respect to the longitudinal axis.
2. The cartridge of claim 1, wherein the first protrusion is configured to pass through a proximal opening of the surgical instrument when a distal end of the cartridge is inserted through the proximal opening.
3 The cartridge of claim 2, wherein the second protrusion is proximally spaced and angularly offset from the first protrusion so as to engage the proximal opening of the surgical instrument when the distal end of the cartridge is inserted into the surgical instrument in a first orientation of the cartridge.
4. The cartridge of claim 3, wherein the second protrusion is located so that, following a rotation of the cartridge from the first orientation to a second orientation in the surgical instrument, the second protrusion can pass through the proximal opening.
5. The cartridge of claim 4, wherein the first protrusion is configured to engage a carriage of the surgical instrument to secure the cartridge to the carriage when the cartridge is rotated from the first orientation to the second orientation in the surgical instrument.
A surgical instrument for use with the cartridge of any one of claims 1 to 5.
The surgical instrument of claim 6, comprising: a housing to be held in the hand, the housing comprising a proximal opening into which the cartridge is insertable; a hollow shaft extending in a distal direction from the housing and defining a distal opening at a distal end thereof; a fluid inlet for fluid connection to the cartridge; a conduit extending between the fluid inlet and the distal opening of the housing; and a drive arrangement operable to cause the fluid to be dispensed through the conduit from the inlet, the drive arrangement comprising a carriage for receiving the cartridge, the carriage comprising a latch, wherein a rotation of the cartridge along its longitudinal axis in the carriage causes the first protnision to engage or disengage the latch to respectively secure the container in or release the container from the carriage.
8. A surgical instrument for dispensing a fluid, the surgical instrument comprising: a housing to be held in the hand; a hollow shaft extending in a distal direction from the housing and defining a distal opening at a distal end thereof; a fluid inlet for fluid connection to a container storing the fluid; a conduit extending between the fluid inlet and the distal opening of the housing; and a drive arrangement operable to cause the fluid to be dispensed through the conduit from the inlet, wherein the drive arrangement comprises a dual pawl ratchet comprising a ratchet wheel and two pawls arranged so that when one of the pawls is engaged to drive one or more teeth of the ratchet wheel, the other pawl is disengaged from any of the teeth of the ratchet wheel.
9. The surgical instrument of claim 8, wherein the drive arrangement comprises a rotary indexer configured to index the ratchet wheel so that the ratchet wheel is incrementally rotatable 10. The surgical instrument of claim 9, wherein the rotary indexer is configured to index the ratchet wheel so that a different one of the pawls is engaged with one or more teeth of the ratchet wheel each time the pawls are returned to a first pawl position after being moved an odd number of increments of the rotary indexer from the first pawl position 11. The surgical instrument of either claim 9 or claim 10, wherein the rotary indexer comprises an indexer ring comprising plural detents circumferentially spaced around the indexer ring, and at least two protrusions for engaging respective detents of the indexer ring to provide the incremental rotation, wherein the protrusions are arranged so that when one of the protrusions is engaged with a detent, the other protrusion is disengaged from any of the detents.12. The surgical instrument of any one of claims 8 to 11, wherein the container is an insertable cartridge, wherein the housing comprises a proximal opening at a proximal end of the housing, the proximal opening configured to receive the cartridge, and wherein the drive arrangement comprises a carriage for receiving the cartridge, the carriage comprising a latch, wherein a rotation of the cartridge in the carriage causes a protrusion of the cartridge to engage or disengage the latch to respectively secure the cartridge in or release the container from the carriage 13. The surgical instrument of claim 12 for use with the cartridge of any one of claims Ito S. 14. The surgical instrument of claim 7, or either of claims 12 and 13, wherein the drive arrangement comprises a drive element operable by a user, and wherein the carriage is coupled, or couplable, to the drive element, so that moving the drive element in a first element direction causes the carriage to move in a first carriage direction; wherein movement of the carriage in the first carriage direction causes the fluid to be dispensed along the conduit from the cartridge.The surgical instrument of claim 14, comprising a plunger, at least a part of which is receivable in the cartridge, in use, and wherein movement of the carriage is operable to cause the cartridge to advance relative to the plunger.16. The surgical instrument of claim 15, wherein the at least a part of the plunger is arranged to be received in a distal end of the cartridge, in use.17. The surgical instrument of claim 15 or claim 16, wherein the plunger is fixed relative to the housing and the carriage is slidably mounted in the housing to advance the cartridge relative to the plunger upon operation of the carriage.18. The surgical instrument of any one of claims 14 to 17 wherein the carriage is releasably couplable to the drive element 19. The surgical instrument of any one of claims 14 to 18, wherein the carriage comprises a connector configured to couple the carriage and the drive element when the container is secured in the carriage, and to decouple the carriage and the drive element when the container is not secured in the carriage.20. The surgical instrument of claim 19, wherein the drive arrangement comprises a rack and pinion arrangement for coupling the carriage and the drive element, and wherein, upon rotation of the container to secure the container in the carriage, the connector is caused to engage the rack.21. The surgical instrument of any one of claims 14 to 20, wherein the drive element is biased towards a second element direction, opposite to the first element direction.22. The surgical instrument of claim 7 or any one of claims 12 to 21, comprising a carriage biasing element configured to bias the carriage in a second carriage direction, opposite to the first carriage direction.23. The surgical instrument of any one of claims 7 to 22, comprising an adjuster operable to limit a range of movement of the drive arrangement.24. A surgical instrument comprising the cartridge of any one of claims 1 to 5.The surgical instrument of claim 24, wherein the surgical instrument is the surgical instrument of any one of claims 7 to 23.