GB2558717A

GB2558717A - Orthopaedic reference gantry

Info

Publication number: GB2558717A
Application number: GB1717832.8A
Authority: GB
Inventors: Papadionysiou Filippos
Original assignee: Individual
Current assignee: Individual
Priority date: 2016-10-28
Filing date: 2017-10-30
Publication date: 2018-07-18
Also published as: GB201717832D0

Abstract

An orthopaedic reference gantry for planning and implementation of orthopaedic procedures has a base platform (100, figure 1) to which is releasably attached a reference gantry kinematic loop 300. A reference gantry arm 250 for receiving and adjusting the orientation and position of a plurality of instruments is mounted on the loop. Instruments are connected or applied to one or more bone segments. The reference gantry defines a Cartesian coordinate system for defining the orientation and position of the instruments and/or the one or more bone segments placed in the coordinate system. The base platform may have a radiolucent reference grid with cutaway channels to receive additional (vertical) reference grids (25, figure 8) or clamp assemblies (60, figure 3). The kinematic loop may comprise two vertical guide rails 180 connected by a horizontal stage 210 bearing a vertical stage 230 on which is mounted the gantry arm.

Description

(54) Title of the Invention: Orthopaedic reference gantry Abstract Title: Orthopaedic reference gantry (57) An orthopaedic reference gantry for planning and implementation of orthopaedic procedures has a base platform (100, figure 1) to which is releasably attached a reference gantry kinematic loop 300. A reference gantry arm 250 for receiving and adjusting the orientation and position of a plurality of instruments is mounted on the loop. Instruments are connected or applied to one or more bone segments. The reference gantry defines a Cartesian coordinate system for defining the orientation and position of the instruments and/or the one or more bone segments placed in the coordinate system. The base platform may have a radiolucent reference grid with cutaway channels to receive additional (vertical) reference grids (25, figure 8) or clamp assemblies (60, figure 3). The kinematic loop may comprise two vertical guide rails 180 connected by a horizontal stage 210 bearing a vertical stage 230 on which is mounted the gantry arm.

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DESCRIPTION

ORTHOPAEDIC REFERENCE GANTRY

Field of the invention

This invention relates generally to orthopaedics and, more particularly, to an orthopaedic reference gantry, which is intended for planning and implementation of multiple orthopaedic procedures such as registration, milling, drilling, reduction and consolidation of bone segments.

Background of the invention

Pre-operative planning of an orthopaedic operation such as a fracture repair or deformity correction is facilitated by imaging of bone segments. Typically, two-dimensional images e.g. radiographs have been used to depict three-dimensional objects (bone segments) for calculating six deformity parameters (anteroposterior, lateral and axial plane translation and rotation). However, the magnitude of the deformity parameters is not the same if the images of the bone segments are obtained from different perspectives. Conventional deformity analysis has approached this problem by generating a reference system based on predetermined bone landmarks of a reference bone segment. This solution relies on positioning the reference bone segment perpendicular to the imaging beam or scan by means of external visible or palpable landmarks.

However, in some cases such as combined angular and rotational deformities, the ability of the physician to obtain images truly perpendicular to a reference bone segment based on external landmarks is limited. Hence, the assessment of the deformity parameters can be inaccurate. For example, length assessment can be accomplished by means of various radiographic rulers used to measure directly the relative distance between two anatomic landmarks. Projectional artifacts can be generated due to non-parallel positioning of the line defined by two anatomic landmarks (true length) relative to the plane defined by the ruler/x-ray film. Thus, the ruler can indicate the apparent distance of these landmarks projected to the plane of the ruler/x-ray film. Projectional artifacts related to angulation deformity assessment are also generated if a reference bone segment is not placed, such that the imaging beam or scan is perpendicular to the axiai/longitudinai reference axis of the reference bone segment.

It is important that the choice of the reference bone segment has not changed between image acquisition and surgical intervention. Reduction of bone segments based on pre-operative planning requires an image-to-patient registration process to match the operating anatomy with its pre-operative image. Registration based on external visible or palpable landmarks can be inaccurate. Registration by use of optical markers requires the insertion of navigation frames. However, the navigation frames cannot be used pre- or post-operatively and may obscure the surgical field intra-operatively, as they need to remain inserted throughout the surgical procedure.

Three-dimensional reconstruction of a bone from CT/MRI images or stereoradiography can be used for registration of a bone and calculation of the deformity parameters. However, the applicability of these methods intra- and post-operatively is limited because of the significant radiation exposure, cost and artifacts created by the implants.

After pre-operative planning, accurate positioning of screws contributes to the ideal static integrity of spinal or orthopaedic fusion and fixation. For this purpose various trajectory finding devices have been used, such as the apparatus described in US 2014/0275955 issued Sep. 18, 2014 to Crawford, Theodore and Foster. Lack of manual control/actuation entails a high cost.

Various orthopaedic devices have been used for mechanical reinforcement of the reduction to counteract any muscle contraction that potentially has caused bone segments to override, such as the apparatus described in WO1998/046156 issued Oct. 22, 1998 to Moorcroft, Ogrodnick and Thomas or in US2013/0253514 issued Sep. 26, 2013 to Starr. However, the devices described in these documents are primarily designed for reduction of certain bones. If used elsewhere, surgical and anatomic restrictions may result in limited reduction capacity or they may obscure the surgical field.

Alternatively, certain external fixators may be used to accomplish the reduction of bone segments provided they comprise a kinematic mechanism. A kinematic mechanism is a linkage of rigid members connected through kinematic joints, such that the relative motion between them is constrained. Kinematic joints are either active or passive. The active joints comprise actuators while the passive joints are free to move. Active joints used in orthopaedics are rotary (revolute) or sliding (prismatic) joints. External fixators (EFs) designed to accomplish reduction can be broadly divided into EFs based on an open- or closed-loop kinematic mechanism.

EFs based on a closed-loop kinematic mechanism (parallel manipulators) comprise one or more closed kinematic loops i.e. linkages of interconnected rigid members where the last rigid member is connected back to the first rigid member and the relative motion between them is constrained. Parallel-type EFs are broadly divided into fully parallel-type EFs originally based on an industrial platform introduced by Gough and Whitehall in 1962 and by Stewart in 1965; and Ilizarov-type EFs introduced by G. A. Ilizarov during the early 1950’s.

Fully parallel-type EFs were originally employed in industry to perform repetitive pick-and-place operations. The orthopaedic reduction is a single pick-and-place operation. An example of a fully parallel-type EF is disclosed in U.S. Pat. No. 5,702,389 issued Dec. 30, 1997 to Taylor et al. They always provide six degrees of freedom (DOF). However, six DOF are not always necessary, as in many cases reduction can be accomplished either by a single translation along a correction axis or by a single rotation about a correction axis. Additionally, parallel manipulators cannot be customised in terms of number, type and orientation of their kinematic joints. Hence, they always load the EF frame with the same number of rotary and sliding joints leading to bulky EFs. Bulky EFs can cause discomfort to patients or interfere with obtaining radiographic images. Furthermore, they may create a shield effect on the healing fractured or osteotomized site.

Ilizarov-type EFs comprise closed kinematic loops that can be customised to provide six or fewer DOF. If they provide six DOF, they require many parts and it can be relatively cumbersome and time-consuming to assemble them. They usually have to be modified progressively after primary assembling by repositioning the kinematic joints to convert from one correctional axis to another.

In EFs based on an open-loop kinematic mechanism (serial manipulators) one end segment of the kinematic mechanism is fixed while the other end can move freely. Monolateral fixators are typical examples of serial manipulators. They are less bulky than parallel-type EFs. If they provide six DOF, their kinematic mechanism usually comprises a minimum of three sliding and three rotary joints disposed such that the central functional axes of the joints are perpendicular to each other. Customizing their kinematic mechanism by adjusting the orientation of the central functional axis of one kinematic joint relative to another is not always possible.

After accomplishing reduction of the bone segments, the physician can further customise the EF by constructing an EF frame (i.e. an assembly of connecting rods, rings, clamps and the like for consolidating the bone segments) according to the unique static requirements of every consolidation. Conventional EF frames with pre-affixed kinematic mechanisms have torsional, flexural and axial stiffness characteristics determined by the position and the orientation of their kinematic joints. Hence, the physician has limited ability to customise the EF frames. Furthermore, the placement of bone fasteners relative to the bone is occasionally determined by the limitations of the chosen EF frame rather than the frame being adjusted based on the required position of the bone fasteners. Hence, monolateral fixators tend to be relatively weak cantilever devices, while Ilizarov and fully parallel-type EFs tend to be more robust than required.

The present invention provides methods and apparatuses to alleviate the aforementioned drawbacks.

Summary of the invention

Aspects and embodiments of the present invention are defined in the appended claims.

This invention provides an orthopaedic reference gantry (RG) adaptable at any operated anatomic site.

A particular object of this invention is to provide the physician with a multi-instrument orthopaedic tool for accomplishing planning and implementation of multiple orthopaedic procedures such as registration, milling, drilling, reduction, and consolidation of bone segments with reference to a Cartesian coordinate system defined relative to the present invention. The said coordinate system is based on three mutually perpendicular reference axes.

It is another object of this invention to provide an RG that defines the orientation, position and intersection point of the three mutually perpendicular reference axes relative to the RG such that the said reference axes are independent of the position of any bone segments placed in the coordinate system or any axes associated with the deformity analysis of the bone segments. The RG is provided with a plurality of radiolucent reference grids (RRGs) that comprise a plurality of embedded radiopaque calibrated lines. The RRGs can be connected such that the said calibrated lines correspond to the reference axes of the coordinate system.

According to one aspect of the present invention, there is provided a method whereby registration of a bone segment, an instrument, and/or a correction axis can be accomplished by bi-planar imaging for extrapolating the coordinates of at least three noncollinear points of the bone segment, at least three noncollinear points of the instrument, and/or at least two points of the correction axis. Each point is either visually discernible or identifiable by its known density or geometric properties in both planar images. Each point designated by three RG-extrapolated coordinates will be defined hereafter as a three-dimensional point (3DP). Three noncollinear 3DPs of a bone segment define a reference triplet.

According to another aspect of the present invention, there is provided a method whereby the physician can register a 3DP by calculating the coordinates of the 3DP. The physician can geometrically correlate extrapolated coordinates of the 3DP with a local coordinate system defined by a reference triplet pre-operatively. After registration of the reference triplet intra- and/or post-operatively, the physician can calculate the coordinates of the 3DP based on their pre-operatively established geometric correlation with the local coordinate system.

It is another object of this invention to provide an RG that temporarily consolidates bone segments without obstructing surgical interventions and yet is portable and remains substantially rigid while transferring patients.

It is another object of this invention to provide a kinematic mechanism attached to a base platform of the RG that comprises an RG-kinematic loop and an RG-arm. The RG-kinematic loop comprises an assembly of prismatic joints for translating instruments and/or bone segments. The RG-arm comprises a pair of directional hinges for receiving a plurality of instruments. The first hinge is a trend hinge and defines a trend central functional axis; the second hinge is a plunge hinge and defines a plunge central functional axis.

According to another aspect of the present invention, there is provided a method whereby the physician can orientate an instrument attached to the RG-arm.

According to another aspect of the present invention, there is provided a method whereby the physician can register an instrument attached to the RG-arm by correlating a central functional axis of the instrument with a calibrated intersection point of the trend and the plunge central functional axes.

It is another object of this invention to provide an RG that can be used as a trajectory finding device by means of an RG-drilling guide attached to the RG-arm.

It is another object of this invention to provide an RG that can be used as a milling machine to facilitate procedures such as drilling, milling, reaming, and tapping of registered bone segments by actuation of an RG-milling drill attached to the RG-arm.

According to another aspect of the present invention, there is provided a method whereby the kinematic mechanism of the RG can be customised for substantially fully accomplishing reduction of one or more bone segments intra-operatively. An RG-rotating ring can be attached to the RG-arm to facilitate rotation of the one or more bone segments. After reduction, part of the RG-rotating ring can be incorporated into an EF frame for consolidation of the bone segments.

It is another object of the present invention to provide a method, whereby the kinematic mechanism of the RG can be used for partially accomplishing reduction intra-operatively and for customizing an EF kinematic mechanism capable of accomplishing the remaining part of the reduction postoperatively. An RG-rotating ring and/or an RG-translation unit can be attached to the RG-arm for intra-operative reduction. After intra-operative reduction, the physician can disconnect the RG-rotating ring and/or the RG-translation unit from the RG-arm to configure a customised EF open-loop kinematic mechanism for post-operative reduction.

It is another object of the present invention to provide a method whereby the physician can configure an EF closed-loop kinematic mechanism by connecting one or more RG-passive prismatic joints to the RG-rotating ring.

It is another object of this invention to separate the placement and configuration of an EF kinematic mechanism from the placement and configuration of the EF frame before all the parts become interconnected for definitive fixation. Hence, the EF kinematic mechanism and the EF frame are not subservient to each other.

These and other object features and advantages of one or more aspects will become apparent from a consideration of the ensuing description and accompanying drawing.

Brief description of the drawings

FIG. 1 is a perspective view of one embodiment of the base platform of the present invention.

FIG. 2 is an exploded view of the base platform depicted in FIG 1.

FIG. 3 is a perspective view of one embodiment of a platform clamp assembly coupling a bone segment to the base platform.

FIG. 4 is an exploded view of the platform clamp assembly depicted in

FIG 3.

FIG. 5 is an exploded view of one embodiment of a platform-to-rod clamping coupling.

FIG. 6 is a perspective view of the platform-to-rod clamping coupling in cross section along plane a-a of FIG. 5

FIG. 7 is an exploded view of one embodiment of a rod-to-rod clamping coupling.

FIG. 8 is a perspective view of one embodiment of the base platform and an additional reference grid exposed to bi-planar imaging for registration of a bone segment.

FIG. 9 is a perspective view of one embodiment of the additional reference grid.

FIG. 10 is a diagram of a reference gantry-based Cartesian coordinate system for registration of an anatomic point A of a bone.

FIG. 11 is an exemplary illustration of a plurality of three-dimensional points of the bone.

FIG. 12 is a perspective view of one embodiment of a pair of base carriages engaged with the base platform of the present invention.

FIG. 13 is an exploded view of a base carriage depicted in FIG 12.

FIG. 14 is an exploded view of one embodiment of two vertical beams.

FIG. 15 is a perspective view of one embodiment of the kinematic mechanism of the present invention.

FIG. 16 is another perspective view of the kinematic mechanism of the present invention.

FIG. 17 is an exploded view of one embodiment of a horizontal stage, a vertical stage and a reference gantry-arm of the kinematic mechanism of the present invention.

FIG 18 is a diagram of a reference gantry-based Cartesian coordinate system for defining the orientation of an axis.

FIG. 19 is another exploded view of the vertical stage and the reference gantry-arm depicted in FIG 17.

FIG. 20 is a perspective view of one embodiment of a directional hinge of the reference gantry-arm, in cross section along plane b-b of FIG. 19.

FIG. 21 is a vectorial diagram that shows rotation of a unit vector AB about an axis A1 by angle Θ.

FIG. 22 is a vectorial diagram that shows rotation of the unit vector AB about a vector IA’ by angle φ.

FIG. 23 is a perspective view of another embodiment of an additional reference grid attached to the reference gantry-arm.

FIG. 24 is another perspective view of the additional reference grid depicted in FIG 23.

FIG. 25 is a perspective view of one embodiment of a reference gantrydrilling guide attached to the reference gantry-arm.

FIG. 26 is an exploded view of the reference gantry-drilling guide depicted in FIG 25.

FIG. 27 is a perspective view of one embodiment of a reference gantrymilling drill attached to the reference gantry-arm.

FIG. 28 is another perspective view of the reference gantry-milling drill of the present invention.

FIG. 29 is a perspective view of one embodiment of a reference gantryrotating ring attached to the reference gantry-arm.

FIG. 30 is another perspective view of the reference gantry-rotating ring attached to the reference gantry-arm.

FIG. 31 is an exploded view of the reference gantry-rotating ring depicted in FIG 30.

FIG. 32 is an exploded view of one embodiment of a housing unit of the reference gantry-rotating ring.

FIG. 33 is a perspective view of a bone segment coupled to the reference gantry-rotating ring

FIG. 34 is a perspective view of the bone segment depicted in FIG 34 after reduction by the kinematic mechanism of the present invention.

FIG. 35 is a perspective view of one embodiment of an external fixator comprising part of the reference gantry-rotating ring.

FIG. 36 is a perspective view of one embodiment of a kinematic mechanism of an external fixator comprising a reference gantry-rotating ring and one embodiment of a reference gantry-translation unit.

FIG. 37 is an exploded view of the kinematic mechanism depicted in FIG 36.

FIG. 38 is a perspective view of the reference gantry-translation unit depicted in FIG 37 in cross section along plane c-c.

FIG. 39 is a perspective view of one embodiment of another kinematic mechanism of an external fixator comprising a reference gantry-rotating ring, a reference gantry-translation unit and one embodiment of a reference gantrypassive prismatic joint.

FIG. 40 is an exploded view of the reference gantry-passive prismatic joint.

FIG. 41 is a perspective view of one embodiment of a dynamic barrel of the reference gantry-passive prismatic joint depicted in FIG 40 in cross section along plane d-d.

Detailed description

Throughout the description and claims of this invention, the word “ comprise” and variations of the word, such as “comprising” and “comprises”, means “including but not limited to” and it does not exclude other components, integers or steps. The term “bone segment” as used herein refers to any intact normal or deformed bone or vertebra, bone or vertebra fragment generated by fractures, defects or osteotomies and/or a sum of vertebrae fused by means of conventional spinal fixation methods.

FIGS 1 and 2 show an overview of one embodiment of the base platform 100 of a reference gantry (RG) 10. The RG 10 is a multi-instrument orthopaedic tool for accomplishing planning and implementation of multiple orthopaedic procedures such as registration, milling, drilling, reduction, and consolidation of bone segments with reference to a Cartesian coordinate system defined relative to the RG 10.

The base platform 100 comprises one or more base platform members

50. Each base platform member 50 can be constructed in various manners, out of various materials, and in various shapes and size. Each base platform member 50 comprises a radiolucent reference grid (RRG) 20, which is supported by a pair of base stages 30. Base stages 30 are in contact with a rigid surface such as an operating table, a radiographic table or other suitable fixture. Base stages 30 are part of a kinematic mechanism of the RG 10 as will become hereinafter apparent.

Each RRG 20 comprises a plurality of cutaway channels 101 for receiving additional RRGs 25 or platform clamp assemblies 60 (as shown in FIG 3). Screws 35 secure the RRGs 20 on the top surface of the base stages

30.

The base stages 30 are generally hollow oblong structures that comprise end caps 32 and guide rails 33, 34. The end caps 32 are typically end plates with snap fit connectors configured to fit within the bores 31 of the base stages 30. The base stages 30 are provided with two rails 33, 34. A toothed rack rail 33 is located adjacent to, and parallel with, the edge of an RRG 20. A smooth rail 34 runs parallel to the rack rail 33.

The base platform members 50 can be connected by means of a modular system comprising smooth connecting rods 21 and toggle latches 22, although it can be appreciated that any other suitable attachment means can be used. Smooth connecting rods 21 enter corresponding bores 31 of the base stages 30 to align the base platform members 50, while toggle latches 22 firmly secure the attachment of the base platform members 50. It is to be emphasised that in some cases more than two base members 50 may be required to span the entire length of the operated site (this case is not illustrated).

FIG 3 shows one embodiment of a platform clamp assembly 60 attached to the base platform 100 for stabilizing a bone segment 5 temporarily, either in an emergency trauma case, where a potentially long operation has to be delayed or prior to the application of any implant. The physician can fasten bone fasteners 2a, b, with the bone segment 5 according to the preferred conventional surgical norm. Bone fasteners 2a, b can be rigidly connected therebetween via an external fixator clamp 41.

A rod-like post 41a of the external fixator clamp 41 can be coupled to the base platform 100 by a platform clamp assembly 60. The platform clamp assembly 60 comprises a platform-to-rod clamping coupling 65, a plurality of connecting rods 66, and rod-to-rod clamping couplings 70. The physician can adjust the number and position of the connecting rods 66 and rod-to-rod clamping couplings 70 in any plane as required.

As shown in FIGS 5 and 6, the platform-to-rod clamping coupling 65 comprises a base member 65a, an anti-rotational cylinder 65b and a base fastener 80. Two cut sections 80a, b designate four projections 80c that together form a shape complimentary to the cutaway channels 101. The intersection of the cut sections 80a, b corresponds to a central threaded bore 65c that receives a base fastener screw 81. When the physician tightens the base fastener screw 81, the projections 80c splay to expand against the sidewall of the cutaway channels 101 and thereby secure the platform-to-rod clamping coupling 65 into the cutaway channels 101.

The anti-rotational cylinder 65b of the platform-to-rod clamping coupling 65 is shaped to receive a connecting rod 66 within a central bore 65d. The central bore 65d communicates with a transverse threaded bore 65e for receiving a rod fastener 75. Tightening the rod fastener 75 urges a connecting rod 66 placed within the said bore 65d against the sidewall of the rotational cylinder and thereby is secured in place.

FIG 7 shows an exploded view of one embodiment of a rod-to-rod clamping coupling 70 designed to couple connecting rods 66. It comprises a dual fastener means 71 and two clamps 72. Each clamp 72 comprises bores 72a, b. Each clamp 72 is configured to receive connecting rods 66 or rod-like posts of EF clamps through bore 72a. The Bore 72b is configured to receive a dual fastener means 71. Each bore 72a, b is associated with a cut section 72c that can be compressed by tightening the dual fastener means 71 for clamping the connecting rods 66 or the said posts.

A dual fastener means 71 comprises a hexagonal shaft 71b, a washerlike member 71c and a partially threaded shaft 71 d, as shown in FIG 7. The said shaft 71 d is capped by a handle 71a. Tightening the dual fastener means 71 can be performed either manually using the handle 71a or by a corresponding tool (not illustrated) applied to the hexagonal shaft 71b.

FIG 8 shows one embodiment of the RG 10 used for pre-, intra- and/or post-operative registration. The RG 10 defines a Cartesian coordinate system, said coordinate system is based on three mutually perpendicular reference axes (yy’, xx’, zz’) for defining the orientation and position of bone segments or instruments placed in the coordinate system, and/or any axes associated with the deformity analysis of the bone segments.

The orientation, position and intersection point (origin of the coordinate system) of the three mutually perpendicular reference axes are defined relative to the RG 10, such that the reference axes are independent of the position of any bone segments or instruments placed in the coordinate system, and/or any axes associated with the deformity analysis of the bone segments.

As shown in FIGS 8 and 9, an additional RRG 25 can be coupled to an RRG 20. An additional RRG 25 comprises two base members 25a. Each base member 25a is configured to correspond to a cutaway channel 101 of the RRG 20, thus the additional RRG 25 can be temporarily inserted into a pair of cutaway channels 101 of the RRG 20. The RRGs 20, 25 comprise a plurality of embedded calibrated lines R1, R2, R3 illustrated by a plurality of lines arranged in a square crisscross pattern. The calibrated lines R1, R2, and R3 designate a metric scale that corresponds to the metric scale of the reference axes of the coordinate system. Calibrated lines R1 correspond to the yy’ axis, calibrated lines R2 correspond to the xx’ axis, and calibrated lines R3 correspond to the zz’ axis. The RRGs 20, 25 are preferably constructed from radiolucent materials, whereas the calibrated lines R1, R2, R3 can be constructed from radiopaque materials. This allows the calibrated lines to be seen during imaging, whereas the RRGs are not.

The RRGs 20 comprise calibrated lines R1, R2 that define a first imaging plane. The additional RRGs 25 comprise calibrated lines R1, R3 that define a second imaging plane. After an additional RRG 25 is connected to an RRG 20, a bone segment and/or an instrument can be placed adjacent to the interconnected pair of RRGs 20, 25. The physician can orientate the imaging beam or scan of an imaging device (x-ray, fluoroscopic, CT devices and the like as indicated by arrows x), such that the imaging beam or scan is perpendicular to the first imaging plane. After exposing the bone segment and/or the instrument to imaging or scanning for generating a first planar view, the physician can orientate the imaging beam or scan such that is perpendicular to the second imaging plane. Re-exposing the bone segment and/or the instrument to imaging or scanning generates a second planar view. It is to be emphasised that the imaging beam or scan does not have to be orientated perpendicular to a longitudinal axis (centerline) of the bone segment.

The generated bi-planar view can be used for extrapolating three Cartesian coordinates for each anatomic landmark (point) of the bone segment or each fiducial point of the instrument that is visually discernible or identifiable by its known density or geometric properties (e.g. mid-diaphyseal anatomic point) in both planar images. Fiducial points are small radiopaque objects that show up as small bright spots in images such as radiographs.

FIG 10 shows an example of a point A visually discernible in both views obtained such that the first view is perpendicular to the RRG 20 and the second view is perpendicular to the additional RRG 25. Point A can be correlated with the calibrated lines R1, R2, R3 of the RRGs 20, 25. Two Cartesian coordinates can be extrapolated from each imaging plane (i.e. x1, y1 and y1, z1), of which one of them is common, yielding a total of three Cartesian coordinates (x1, y1, z1) for point A.

It is to be emphasised the RRGs 20, 25 can be disposed either perpendicular or oblique to each other (the latter case is not illustrated). If occasionally an anatomic point is not discernible in orthogonal views, it can be discernible in oblique views. If oblique coordinates are extrapolated, they can be correlated to Cartesian coordinates. Hence, the term “coordinates” as will be used herein refers to Cartesian coordinates.

Anatomic or fiducial points designated by three coordinates will be defined hereafter as three-dimensional points (3DPs). At least two 3DPs are required to define an axis in the coordinate system. At least three noncollinear 3DPs are required to define the position of a bone segment or an instrument in the coordinate system. Three noncollinear 3DPs of a bone segment will be defined hereafter as a reference triplet.

As shown in FIG 11, extrapolating the coordinates of a reference triplet ABC pre-operatively is a simple type of registration that establishes a local frame of reference on the bone segment, thus integrates it into the coordinate system by the exclusive use of bi-planar imaging. Extrapolating the coordinates of the same reference triplet ABC intra- and/or post-operatively integrates the bone segment into the same coordinate system.

To calculate six deformity parameters (anteroposterior, lateral and axial plane translation and rotation), the physician can use a conventional twodimensional deformity analysis method (2D method) or a three-dimensional deformity analysis method (3D method). The physician can also combine aspects of a 3D and 2D method. For example, the physician may calculate rotation parameters by using a 2D method and calculate translation parameters by using a 3D method to avoid direct measurements by means of radiographic rulers. The measurement of the relative distance of two extrapolated 3DPs e.g. 3DPs A (x1, y1, z1) and D (x2, y2, z2) to assess axial, lateral and/or anteroposterior translation deformity can be indirectly derived from their coordinates i.e. the length AD of the line segment bounded by points A and D is: AD=7(x2 - xl)² + (y2 - yl)² + (z2 - zl)² (equation 1)

If a 2D method is used, the RG 10 can be used for registration of an axial axis of the reference bone segment, as will become hereinafter apparent. The physician can adjust the imaging beam or scan based on the position of the axial axis, such that the imaging beam or scan is perpendicular to the axial axis.

If a 3D method is used, the position of the bone segments in the coordinate system can vary without affecting the magnitude of the deformity parameters. However, registration is required intra- and post-operatively as well. The RG 10 can be used for registration of bone segments by means of biplanar imaging avoiding three-dimensional reconstruction of the bone segments.

Calibrating the imaging beam or scan for pre-operative registration/preoperative deformity analysis, calibrating the imaging beam or scan for intraoperative registration, and calibrating the kinematic mechanism used for reduction can be facilitated by transposing the origin of the reference system from a point related to a reference bone segment to a point related to the RG 10 (e.g. point O as illustrated in FIG 10). Thus, calibration is always referenced to the coordinate system of the RG 10.

The kinematic mechanism of the RG 10 comprises an RG-kinematic loop 300 and an RG-arm 250, as shown in FIG 15.

FIG 12 shows one embodiment of a pair of base carriages 150 disposed on the base stages 30 for assembling the RG-kinematic loop 300. A base carriage 150 can be slidably mounted on the guide rails 33, 34 of the base stage 30. The base carriage 150 comprises a series of wheels 152 configured to run along the smooth rail 34 and the non-toothed side of the rack rail 33. The wheels 152 are connected via bearings 151 to a base carriage platform 155. The base carriage 150 can translate along the rails 33, 34 of the base stage 30 by a pinion 170.

The pinion 170 comprises a pinion handle 175 and a pinion brake 157. The pinion 170 is pivotally connected to the base carriage platform 155 via the pinion brake 157. The pinion 170 is configured to engage with the toothed side of the rack rail, thereby forming a prismatic joint. Translation can be prevented by engaging the pinion brake handle 158.

As shown in FIGS 13 and 14, a pair of guide rails 153 is rigidly connected to the top surface of the base carriage platform 155 for receiving one embodiment of a vertical beam 180 of the RG-kinematic loop 300. Each guide rail 153 is provided with a stop wall 153a.

The vertical beam 180 comprises a vertical shaft 180a and a base member 180b, The vertical shaft 180a is provided with a vertical guide rail 180c. The base member 180b comprises a pair of longitudinally extending tracks 180d on the underside, which correspond to guide rails 153, thereby the vertical beam 180 can register and advance up to the guide rail stop wall 153b. Alternatively, the vertical beam 180 may be rigidly fixed to the base carriage platform 155. However, occasionally the bone fasteners may extend beyond the edge of the RG 10. Hence the physician may need to slide the carriage platform 155 under the bone fasteners, and then couple the vertical beam 180 to the carriage platform 155.

Furthermore, the base member 180b comprises a guide rail brake 190 for securing the vertical beam 180 to the base carriage platform 155. The guide rail brake 190 comprises a handle 190a and a compression body 190c rigidly attached to the base member 180b. The handle 190a comprises an end segment configured as a head 190b. When the handle 190a is tightened, the head 190b compresses the sidewall of the guide rails 153 and thereby secures the vertical beam 180 in place.

As shown in FIGS 15, to fully assemble the RG-kinematic loop 300, the physician can slidably engage one embodiment of a horizontal stage 210 with the vertical guide rails 180c of the vertical beams 180. Attached to the horizontal stage 210 can be a vertical stage 230 and an RG-arm 250.

As shown in FIGS 17 and 19, the horizontal stage 210 is capped at either end by a track 210b configured to engage with the corresponding vertical guide rail 180c. After the horizontal stage 210 is positioned, it can be rigidly coupled to the vertical beams 180 by engaging a guide rail brake 190 attached to an end surface of the track 210b.

The horizontal and vertical stages 210, 230 comprise a stage platform 210a, 230a respectively. Each stage platform 210a, 230a comprises a pair of longitudinally extending guide rails 210c, 230c that correspond to a pair of grooves 230b of the vertical stage 230 and a pair of grooves 260b of a directional hinge 260 respectively.

Platforms 210a, 230a also comprise bores 21 Od, 230d on their sidewalls for receiving a ball bearing 212. Each ball bearing 212 has a central bore through which a leadscrew 215, 236 is pivotally connected to platforms 210a and 230a respectively. The thread of the leadscrews 215, 236 is configured to mate with threaded openings 230e, 260a of the vertical stage 230 and the directional hinge 260 respectively.

As shown in FIG 16, each stage 30, 210, 230 of the kinematic mechanism of the RG 10 provides a prismatic joint orientated such that it generates translation along a reference axis xx’, yy’, zz’ of the coordinate system. The actuators of each stage 30, 210, 230 (i.e. the pinion 170 and leadscrews 215, 236) are provided with ridged thumbwheels (handles) 175, 215a, 236a respectively. Rotation of a ridged thumbwheel 175, 215a, 236a can be performed either manually or by means of a servo/stepper motor actuator affixed thereto. The latter case is not illustrated. This allows a precise degree of movement of the RG-arm 250 along the reference axes of the coordinate system.

As shown in FIGS 14, 16 and 17 the kinematic mechanism of the RG 10 can be calibrated by a ruler (R) disposed adjacent to, and parallel with the rails of each stage 30, 210, 230. Each ruler corresponds to a reference axis of the coordinate system. Rulers R1 measure translation of the RG-arm 250 along the yy’ axis. Rulers R2 measure translation of the RG-arm 250 along the xx’ axis. Rulers R3, R4 measure translation of the RG-arm 250 along the zz’ axis of the coordinate system. Rulers 3 measure translation of the RG-arm 250 along zz’ axis after gross adjustments, whereas rulers R4 depicted on the vertical stage 230 measure translation of the RG-arm 250 along the zz’ axis after fine adjustments.

Markers M1 on the base carriages 150 (as shown in FIG 13), marker M3 on the horizontal stage 210 (as shown in FIG 18), marker M2 on the vertical stage 230 (as shown in FIG 16), and marker M4 on the RG-arm 250 (as shown in FIG 19) provide an indication of the displacement along the yy’, xx’, and zz’ reference axes respectively.

FIGS 17 and 19 show one embodiment of an RG-arm 250 attached to the vertical stage 230. The RG-arm 250 comprises two directional hinges 260, 280. Directional hinges 260, 280 will be defined hereafter as a trend and plunge hinge 260, 280 respectively. Trend and plunge hinges 260, 280 define a trend and plunge central functional axis A1, A2 respectively. The said axis A1, A2 are preferably perpendicular to each other

A “central functional axis” of an instrument or a hinge will be defined hereafter as a virtual axis that shows the direction along or about which the main function of the instrument or the hinge is performed e.g. milling, drilling, rotation, translation and the like.

The trend and plunge hinges 260, 280 comprise a central bore 260d, 280d respectively as shown in FIG 19. The directional shaft 285 of the plunge hinge 280 is received within the bore 260d of the trend hinge 260. The bore 280b of the plunge hinge 280 is generally configured to receive a directional shaft of an instrument.

The directional shaft 285 of the plunge hinge 280 and the directional shaft of any instrument attached to the plunge hinge 280 can be scored by a marker at an end face, as shown in FIGS 19, 24 26. In particular, FIG 19 shows a marker 285M of the directional shaft 285 configured to correspond to a protractor P1 depicted on a sidewall of the trend hinge 260 for defining a trend angle. FIGS 24 and 26 show the marker M of the directional shaft of instruments attached to the plunge hinge 280, which is configured to correspond to a protractor P2 depicted on a sidewall of the plunge hinge 280 for defining a plunge angle.

As shown in FIGS 17 and 18, the physician can adjust the orientation of the central functional axis of any instrument attached to the plunge hinge 280 according to the orientation of a registered correction axis by using the following method:

The physician can register a correction axis along or about which a bone segment can be translated, rotated, drilled, milled and the like by a pair of 3DPS e.g. 3DP O (x2, y2, z2) and 3DP D (x5, y5, z5), as shown in FIG 18. A set of mutually orthogonal unit vectors i, j, and k form the basis of the coordinate system. Vectors ί and; define a horizontal plane, whereas vectors j, and k define a vertical plane. The physician can normalize the vector OD by using the set of 3DPs O and D:

OD= (x5-x2) i + (y5-y2) j + (z5-z2) k (equation 2).

The normalised (unit) vector u of vector OD that passes through the origin according to equations 1 and 2 is:

OD _ (x5-x2) i + (y5-y2) j+ (z5-z2) k |OD| / (%5-x2)² +(y5-y2)² + (z5-z2)² (equation 3)

The orientation of the unit vector can be defined by a plunge angle φ and a trend angle Θ. The plunge angle φ is the angle between the unit vector u and the horizontal plane of the coordinate system:

. ; ^0D' , / φ = +/-arcos— = +/—arcos ^Ύ od '

V(x5-x2)² +(y5-y2)²7 (%5-x2)² +(y5-y2)² + (z5-z2)² (equation 4), where D’ is the projection of D onto the horizontal plane.

The trend angle Θ is the angle between the projection of the unit vector u on the horizontal plane and the vertical plane of the coordinate system:

OC xS-x2 θ= +/-arcos—= +/-arcos . (equation 5), where C is the

OD' ' 7(x5-x2)² + (y5-y2)^{2 v} ' projection of D’ onto the xx’ reference axis. The sign (+/-) can be determined by the mathematical convention of the reference axes and the right-hand rule

As shown in FIG 17, the physician can rotate the directional shaft of the plunge hinge 280 to set the central functional axis of an instrument (represented by the unit vector AB) at trend angle Θ. Additionally, the physician can rotate the directional shaft of the instrument received by the plunge hinge 280 to set its central functional axis at plunge angle φ. Thus, effectively the central functional axis of the instrument has the same orientation as the correction axis OD.

As shown in FIGS 19 and 20, the physician can secure the directional shaft 280 and the directional shaft of the instrument in place by an internal clamp mechanism (ICM). The ICM comprises a cut section ICM1 along the sidewall of the bores 260d, 280d and a cut section ICM2 perpendicular to ICM1. These cut sections define a block that comprises a partially threaded bore ICM3 for receiving a bolt fastener 262. When said fastener 262 is tightened, the cut sections are compressed and thus the sidewall of the bore is urged against the directional shaft.

Additionally, the bore 260d communicates with a threaded opening 260c as shown in FIG 19 for receiving a corresponding screw retainer 261. The screw retainer 261 can be threadably advanced to engage with a groove 285a of the directional shaft 285, such that the directional shaft 285 can rotate without translating.

After adjusting the orientation of an instrument attached to the RG-arm 250, the physician can register the instrument by correlating the coordinates of two 3DPs of a central functional axis of the instrument with a point of the kinematic mechanism of the RG 10.

As illustrated by the diagrams in FIGS 21 and 22, the physician can calibrate the intersection point I (xT, yT, zT) of the trend and plunge central functional axes A1, A2 (illustrated also in FIG 17). The indications of marker M1 (y1), marker M2 (x1) and markers M3 +/- M4 (z1) correlate with the coordinates of point I:

(xT, yT, zT) = (x1 + a, y1 + b, z1 + c), where a, b, c are determined by the manufacturing dimensions of the RG-arm 250.

FIG 21 shows a unit vector AB that represents the central functional axis of an instrument attached to the RG-arm 250 and a vector IA’ that represents the central functional axis A2. If the directional shaft of the instrument is set at 0° plunge and trend angle, such that the unit vector AB is parallel to the xOy and xOz plane of the coordinate system, the coordinates of points A (x3, y3, z3) and B (x4, y4, z4) can be correlated with the coordinates of the intersection point I (χΓ, y1’, zT):

(x3, y3, z3) = (xT +/- |IA|, y1’, zT) (x4, y4, z4) = (xT +/- |IA|, y1 ’ +/- |AB|, zT), where |IA| is determined by the manufacturing dimensions of the instrument. The sign (+/-) can be determined by the mathematical convention of the reference axes and the right-hand rule.

After rotation of the unit vector AB about the central functional axis A1 by trend angle Θ, points A (x3, y3, z3) and B (x4, y4, z4) are represented by points A’ (x7, y7, z3) and B’ (x8, y8, z4), where the z coordinates remain unaltered. According to one method the coordinates x7, y7, x8, y8 can be correlated with the coordinates xT, yT:

x7= xT +/- IA”, where A” is the projection of A’ onto the xx’ axis, thus IA”= IA’cos0 y7= y1 ’ +/- A’A” ,where A’A”= lA’sinfl, x8= xT +/- IB”, where B” is the projection of B’ onto the xx’ axis, thus

IA IA

IB”= IB’cos (0 - <5), where Cos<5=— δ= arcos —, where |IB| is determined by

IB IB the manufacturing dimensions of the instrument.

y8= yT +/- B’B”, where B’B”= IB’sin (0 - <5), hence

A’ (x7, y7, z3) = A’ (x1’+/-IAcos0, y1’+/-IAsin0, zT)

B’ (x8, y8, z4)= B’ (xT +/- IBcos (0 - 5), yT +/- IBsin (0 - 5), zT)

As shown in FIG 22, after rotation of the unit vector A’B’ about the plunge central functional axis A2, point A’ remains stationary. According to equations 2 and 3, the normalised vector IA’ that represents said axis A2 is:

_Λ _ IA> _ (x7—xlv) i + (y7-yl') j+ (z3-zl') k ^u

1«/ II I 1 x7—xl' y7-yl' , Z3-ZH

We will let- =u, -—— =v and-=w |M| |M| |M|

According to a second method, the physician can use the following normalised 3 X 1 rotation matrix to calculate the coordinates of point B1 (x9, y9, z9) that represents point B’ (x8, y8, z4) after rotation about the vector IA’ defined by unit/direction vector ύ <u, v, w> and point I (χΓ, y1 z’) by angle φ\

B1 (x9, y9, z9) = f(x8, y8, z4, xT, y1 ’, zT, u, v, w, <p) = (matrix 1), where:

K= [xl'(u² + w²) — u (yl'u + zl'w — ux8 — uy8 — wz4)j (1 — cos<p) + %8cos<p + +(—zl'u + yl'w — wy8 + uz4) sm<p

L= [yl'(u² + w²) — u (xl'u + zl'w — ux8 — uy8 — wz4)j (1 — cos<p) + y8cos<p + +(zl'u — xl'w + wx8 — uz4) sirup

M=[zl'(u² + u²) — w (xl'u + yl'u — ux8 — uy8 — wz4)j (1 — cos<p) +z4cos<p + +(—yl'u + xl'u — ux8 + uy8) sirup

It is to be emphasised that the physician can use any of the first method, the second method, any other suitable method, and/or any combination thereof for registration of the central functional axis of an instrument attached to the RG-arm 250. Subsequently, the physician can translate the instrument along the reference axes of the coordinate system to adjust the position of its central functional axis relative to the position of a registered correction axis.

Instruments attached to the RG-arm 250 via their directional shaft can vary. The instruments are either connected to one or more bone segments or applied to one or more bone segments. Instruments attached to the RG-arm 250 include one embodiment of an additional RRG 26 as shown in FIG 23 for spinal registration. FIG 24 shows a perspective view of the additional RRG 26 that can be constructed in a similar way to the additional RRG 25. Attached to the additional RRG 26, there is a directional shaft 26a for connecting the additional RRG 26 to the plunge hinge 280.

Another instrument attached to the RG-arm 250 can be an RG-drilling guide 299 for accurate placement of screws or wires according to the preoperative plan, as shown in FIGS 25 and 26. The RG-drilling guide 299 comprises a directional shaft 309 for connecting the RG-drilling guide 299 to the plunge hinge 280 and a hollow cylinder 308 for receiving various drill bits. The directional shaft 309 comprises a screw 309a for fastening the hollow cylinder 308 into a bore 309b of the directional shaft 309. It is to be appreciated by those skilled in the art that any type of cutting or drilling guide may be additionally used with appropriate adaptation.

One embodiment of another instrument applied to one or more bone segments can be an RG-milling drill 300, as shown in FIGS 27 and 28. The RG-milling drill 300 comprises a chuck 300b for receiving a plurality of milling or drilling bits (the milling or drilling bits are not illustrated), a motor 300a for actuating the milling or drilling bits, and a directional shaft 310 for connecting the RG-milling drill to the plunge hinge 280. The combined action of the RGmilling drill 300 and the RG 10 generates a milling machine. Effectively, this allows precise milling, drilling, tapping, and/or reaming of the bone segments.

As shown in FIGS 29, 30, 31 and 32, one embodiment of another instrument that can be connected to one or more bone segments is an RGrotating ring 320 for rotating the one or more bone segments. The RG-rotating ring 320 comprises a ring plate 360 and a housing unit 380. In particular, the ring plate 320 comprises a serrated surface 360a about its periphery that forms a rack. Furthermore, on each sidewall of the ring plate 360 there is a groove 360b that extends around the circumference and a plurality of bores 360c that pass all the way through the ring plate 360.

One embodiment of a housing unit 380 comprises flattened parallelepiped sides advantageously shaped to accommodate a worm gear 381. The housing unit comprises a pair of directional shafts 385, 386. However, it can comprise more than two directional hinges. The latter case is not illustrated. The housing unit 380 is rotatable about the serrated surface 360a of the RG-rotating ring 320 via the worm gear 381. The housing unit 380 comprises a pair of protrusions 380a, which correspond to grooves 360b of the ring plate 360.The worm gear 381 is pivotally connected to the housing unit 380 by a pair of bearings 382 and accommodated within the cutaway interior of the housing unit 380. A slot 381a of the head of the worm gear 381 is configured to receive a corresponding tool or a servo/stepper motor (not illustrated). By actuation of the tool, the ring plate 360 effectively rotates about its central functional axis A4.

The physician can reduce a bone segment from its original position to its reduced position by translating the bone segment relative to three mutually perpendicular correction axes and/or rotating the bone segment about each of those three axes. Alternatively, a bone segment can be reduced by a translation along a registered translation correction axis (TCA) and/or a rotation about a registered angulation correction axis (ACA). The TCA and the ACA express the total translation and/or rotation equivalent to three translations and/or three rotations along or about the three mutually perpendicular correction axes.

The physician can register a correction axis either by extrapolating or by calculating the coordinates of two 3DPs of the correction axis.

As shown in FIG 11, for calculating the coordinates of a 3DP, the physician can establish a geometric correlation of the 3DP with an extrapolated reference triplet e.g. ABC that defines a local coordinate system. We will let C’ be the projection of 3DP C on the line defined by 3DPs A and B. The cross product of vectors C’C and C’B defines a normal vector N. The normal vector N, the vector C’C, and the vector C’B define three mutually perpendicular reference axes, where C’ is their intersection point (origin of the local coordinate system). The vectors C’C and C’B define a horizontal plane of the local coordinate system. The normal vector N and the vector C’C define a vertical plane of the local coordinate system.

A 3DP can be geometrically correlated with a local coordinate system by the magnitude and the orientation of a position vector of the 3DP defined with respect to the local coordinate system. For example, 3DP F can be geometrically correlated with the local coordinate system ABC by the magnitude of the position vector C’F, a plunge angle between the position vector C’F and the horizontal plane of the local coordinate system, and a trend angle between the projection of the position vector C’F on the horizontal plane and a vertical plane of the local coordinate system. The trend and plunge angles can be calculated in a similar way as described in FIG 20 for calculating the orientation of vector OD (see equations 4 and 5).

The physician can geometrically correlate two 3DPs of a correction axis with the local coordinate system ABC pre-operatively. After registration of the reference triplet ABC by extrapolating the coordinates of 3DPs A, B and C intra-operatively, the physician can register the correction axis by calculating the coordinates of the two 3DPs based on their pre-operatively established geometric correlation with the local coordinate system ABC. Furthermore, the coordinates of the 3DPs of other reference triplets that define the position of a bone segment or an instrument can be also calculated according to the above method.

A registered TCA or ACA can be represented by a vector. The said vector can be resolved into its components along the reference axes of the coordinate system. Hence, translating a bone segment along a TCA is equivalent to translating the bone segment along the reference axes of the coordinate system.

The physician can use the kinematic mechanism of the RG 10 to reduce a bone segment according to a “total reduction mode” or a “split reduction mode”. The bone segments do not have to be placed, such that a reference axis of the coordinate system is substantially parallel to a centerline of a bone segment. The kinematic mechanism of the RG 10 can be customised to provide six degrees of freedom for reduction of bone segments. The degrees of freedom (DOF) refer to translation relative to three reference axes and rotation about each of those axes.

According to the “total reduction mode”, the reduction can be decomposed into one or more translations along the reference axes of the coordinate system and/or a single rotation about a registered ACA.

FIGS 29 and 30 show an RG-rotating ring 320 attached to the RG-arm 250. The central functional axis A4 of the RG-rotating ring 320 is orientated and positioned such that is coincident with a registered ACA. A bone segment 5 is connected to the RG-rotating ring 320 by a plurality of connecting rods 66 and rod-to-rod clamping couplings 70.

According to the “total reduction mode”, rotating the bone segment 5 about the central functional axis A4 is equivalent to three DOF and/or translating the bone segment 5 along the central functional axes of the stages 30, 210, 230 is equivalent to three DOF. Thus, the RG 10 provides six DOF for fully accomplishing reduction intra-operatively. In FIGS 33 and 34, the bone segment 5 is rotated about the said axis A4 and translated along the yy’ reference axis.

After reduction the physician can check the alignment of the bone segments. Any necessary additional adjustments can be easily accomplished before the application of the EF frame for definitive fixation. Thus, the physician can avoid time-consuming adjustments of any parts of the EF frame relative to the bone segments if additional correction is required.

As shown in FIG 35, after rotating the bone segment 5, the RG-rotating ring 320 can be connected to a stationary bone segment 6. Subsequently, by disconnecting the RG-rotating ring 320 from the RG-arm 250, the ring plate 360 of the RG-rotating ring 320 can be integrated into the EF frame. The physician can customise the configuration of the EF frame according to the unique static requirements of every consolidation. Modular building parts such as connecting rods 66 and rod-to-rod clamping couplings 70 can be used, although it can be appreciated that any other suitable EF frame parts can also be used. It is to be appreciated by those skilled in the art that any type of internal fixation can be alternatively used.

According to the “split reduction mode”, the reduction can be partially accomplished intra-operatively, while the remaining part can be accomplished post-operatively.

For this mode of reduction, the physician can use one embodiment of an RG-translation unit (RG-TU) 400 for translating one or more bone segments, as shown in FIGS 36, 37 and 38. The RG-TU 400 can be a telescopic strut that comprises an outer tube 400a, a translating shaft 400b, and a threaded bar 400d. The outer tube 400a has a central square bore configured to receive a translating shaft 400b. A threaded bar 400c is pivotally connected to the outer tube 400a via a bearing 405. The translating shaft 400b has a central threaded bore engaged with the threaded bar 400c. Rotating the threaded bar 440c translates the said shaft 400b along the central functional axis A5 of the RG-TU 400. A ruler R5 depicted on the sidewalls of the translating shaft 400b indicates the magnitude of the translation accomplished along the central functional axis A5.

Additionally, the translating shaft 400b comprises a directional hinge 430 and/or a directional shaft. The directional shaft is not illustrated. The directional hinge 430 can be constructed in a similar way to plunge hinge 280 hence will be defined hereafter as a Translational Unit (TU)-plunge hinge 430.

For intra-operative reduction according to the “split reduction mode”, the physician can either couple an RG-rotating ring 320 via its directional shaft to the RG-arm 250 or an RG-TU 400 via its directional shaft to the RG-arm 250. If the RG-rotating ring 320 is attached to RG-arm 250, the RG-TU 400 can be coupled to the directional shaft 385 of the RG-rotating ring 320 via an independent pair of directional hinges. The independent pair of directional hinges comprises the TU-plunge hinge 430 and another directional hinge 420, as shown in FIG 37.

The directional hinge 420 is preferably constructed in a similar way to trend hinge 280, hence will be defined hereafter as a TU-trend hinge 420. The TU-trend and TU-plunge hinges 420, 430 define a TU-trend and a TU-plunge central functional axis A6, A7 respectively. Any instrument attached to the RGrotating ring 320 via an independent pair of directional hinges will be defined hereafter as an independent instrument.

The TU-trend hinge 420 is attached to a corresponding reference side P1 of the housing unit 380. The reference side P1 and the central functional axis A6 define a local coordinate system. The TU-trend and TU-plunge hinges 420, 430 define a TU-trend and a TU-plunge angle θ', φ' about the TU-trend and the TU-plunge central functional axis A6, A7 with reference to the local coordinate system. The said angles θ', φ' define the orientation of the central functional axis A5 of the RG-TU 400.

According to the “split reduction mode”, the physician can accomplish part of a rotation about a registered ACA and/or part of a translation along a registered TCA intra-operatively. Alternatively, the physician can fully accomplish the rotation about the registered ACA intra-operatively and subsequently fully accomplish the translation along the registered TCA postoperatively or vice versa. The central functional axis A5 of the RG-TU 400 is orientated and positioned such that is either coincident with the registered TCA or parallel to the registered TCA. The central functional axis A4 of the RGrotating ring 320 is orientated and positioned such that is coincident with the registered ACA.

FIG 36 shows an RG-rotating ring 320 and an RG-TU 400 connected to a bone segment 5 via a connecting rod 66, a shaft-to-rod clamping coupling 390, and a rod-to-rod clamping coupling 70. After intra-operative reduction, the physician can connect the RG-rotating ring 320 and/or the RG-TU 400 to one or more stationary bone segments 6 via a plurality of connecting rods 66, rodto-rod clamping couplings 70, and/or other suitable EF frame parts.

Subsequently, the physician can disconnect the RG-rotating ring 320 and/or the RG-TU 400 from the RG-arm 250 and use both of them or one of them to configure an EF open-loop kinematic mechanism (serial manipulator) customised in terms of number, type, position and orientation of its kinematic joints. The said kinematic mechanism provides the desired (six or fewer) DOF for accomplishing the remaining part of the reduction post-operatively.

FIG 37 shows one embodiment of the shaft-to-rod clamping coupling 390. Its construction can be similar to a rod-to-rod clamping coupling 70. However, the bore 390a of the shaft-to-rod clamping coupling 390 has an inner diameter corresponding to the outer tube 400a.

As shown in FIG 39, the physician can further customise the EF openloop kinematic mechanism to configure an EF closed-loop kinematic mechanism (parallel manipulator) by coupling one or more RG-passive prismatic joints (RG-PPJ) 450 to the RG-rotating ring 320.

As shown in FIGS 40 and 41, the RG-PPJ 450 comprises a dynamic barrel 470 and a directional hinge 460, said hinge 460 defines a central functional axis A8. The two parts can be locked together by tightening a translation-locking nut 471 that urges a telescopic shaft 460a of the said hinge 460 against the sidewall of the dynamic barrel 470.

The dynamic barrel 470 comprises a central square bore 470a for receiving the telescopic shaft 460a and a cutaway channel 470b. The dynamic barrel 470 is configured to receive two corresponding elastic O-rings 473. The mid section of the dynamic barrel 470 comprises a threaded opening for receiving a micromovement-locking nut 472. When the translation-locking nut 471 and the micromovement-locking nut 472 are both loosened the dynamic barrel 470 is free to translate along the telescopic shaft 460a. When the translation-locking nut 471 is loosened but the micromovement-locking nut 472 is tightened, the dynamic barrel 470 marginally translates by compressing the elastic O-rings 473 and thus provides stimulation (cyclic micromovement) to the fractured or osteotomized site.

The directional hinge 460 can be constructed in a similar way to plunge hinge 280 hence will be defined hereafter as a passive prismatic joint (PPJ)plunge hinge 460. The RG-PPJ 450 can be connected to the directional shaft 386 of the RG-rotating ring 320 via another directional hinge 480, which is constructed in a similar way to trend hinge 260, hence will be defined hereafter as a PPJ-trend hinge 480. The PPJ- trend and plunge hinge 480, 460 form another independent pair of directional hinges.

The PPJ-trend hinge 480 and a corresponding reference side P2 of the housing unit 380 define a local coordinate system. The PPJ-trend and plunge hinges 480, 460 define a PPJ- trend and plunge central functional axis A9, A10; and PPJ- trend and plunge angles θ, φ with respect to the local coordinate system. The said angles θ, φ define the orientation of the central functional axis A8 of the RG-PPJ 450. The said axis A8 is orientated such that is parallel to the central functional axis A5 of the RG-TU 400.

FIG 39 shows an EF closed-loop kinematic mechanism that comprises an orientated RG-rotating ring 320, an orientated RG-TU 400 and an orientated RG-PPJ 450 configuring a single closed kinematic loop. The configuration and placement of the EF frame can be customised by connecting the EF kinematic mechanism to the bone segments via a plurality of connecting rods 66, shaft-to-rod and rod-to-rod clamping couplings 390, 70.

An advantage of customising the kinematic mechanism of an EF by adjusting the orientation of the central functional axis of each kinematic joint independent of the central functional axis of other joints is that the EF kinematic mechanism can be loaded with the minimum required amount of kinematic joints for providing the desired (six or fewer) degrees of freedom. It is to be emphasised that two or more RG-PPJ 450 can also be connected to two or more directional shafts of the RG-rotating ring 320 for configuring an EF kinematic mechanism comprising two or more closed kinematic loops (e.g. a tripod). The latter case is not illustrated.

It is to be appreciated by those skilled in the art that the present invention may be additionally used with appropriate adaptation for threedimensional printing of EF frame members, RG-instruments, and/or other implants. Furthermore, the present invention may be alternatively used with appropriate adaptation in any situation in which bone immobilization is important such as joint replacement, soft tissue injuries, radiotherapy treatment, brain or spine surgery and the like. Furthermore, numerous modifications may be made to the illustrative embodiments and other arrangements may be devised without departing from the scope of the present invention as defined by the appended claims.

Claims

1. An orthopaedic reference gantry for planning and implementation of orthopaedic procedures, said reference gantry comprising:

a base platform comprising:

one or more base platform members; and a kinematic mechanism removably attached to the base platform, said kinematic mechanism comprising:

a reference gantry-kinematic loop; and a reference gantry-arm for receiving and adjusting the orientation and position of a plurality of instruments, wherein said instruments are either connected to one or more bone segments or are applied to one or more bone segments;

wherein the reference gantry defines a Cartesian coordinate system, and wherein said coordinate system is based on three mutually perpendicular reference axes for defining the orientation and position of the instruments and/or the one or more bone segments placed in the coordinate system.

2. The reference gantry of claim 1, wherein the reference gantry defines the orientation, position and intersection point of the three mutually perpendicular reference axes relative to the reference gantry, such that the said reference axes are independent of the position of any bone segments placed in the coordinate system or any axes associated with a deformity analysis of the bone segments.

3. The reference gantry of claim 1 or claim 2, wherein two or more base platform members are connected by clamping means.

4. The reference gantry of any preceding claim, wherein the base platform comprises one or more reference grids.

5. The reference gantry of claim 4, wherein the one or more reference grids comprise cutaway channels for receiving additional reference grids and/or platform clamp assemblies.

6. The reference gantry of claim 5, wherein each reference grid is radiolucent.

7. The reference gantry of claim 6, wherein each reference grid comprises a plurality of radiopaque calibrated lines, said calibrated lines defining an imaging plane.

8. The reference gantry of any one of claims 4 to 7, wherein the reference grids and any additional reference grids are arranged perpendicular to each other such that the calibrated lines correspond to the reference axes of the coordinate system.

9. The reference gantry of claim 8, wherein the reference grids and the additional reference grids are arranged oblique to each other such that the calibrated lines correspond to the reference axes of an oblique coordinate system, and wherein said oblique coordinate system can be correlated to the coordinate system defined by the reference gantry.

10. The reference gantry of any claim directly or indirectly dependent on claim 5, wherein the platform clamp assemblies couple one or more bone segments to the base platform.

11. The reference gantry of claim 10, wherein each platform clamp assembly comprises one or more connecting rods, one or more rod-to-rod clamping couplings, and a platform-to-rod clamping coupling.

12. The reference gantry of claim 11, wherein the platform-to-rod clamping coupling is configured to splay against the cutaway channels to form a friction fit.

13. The reference gantry of any preceding claim, wherein the reference gantry-kinematic loop comprises a plurality of stages for translating one or more instruments and/or bone segments.

14. The reference gantry of claim 13, wherein each stage has a central functional axis for defining the direction of the translation.

15. The reference gantry of claim 14, wherein each said central functional axis is parallel to a reference axis of the coordinate system, and wherein adjacent to, and parallel with, the central functional axis of each stage there is provided a ruler for calibrating the stages.

16. The reference gantry of claim 15, wherein each stage comprises a carriage member for connecting either one stage to another stage or one stage to a reference gantry-arm.

17. The reference gantry of claim 16, wherein the reference gantry-arm comprises two directional hinges.

18. The reference gantry of claim 17, wherein each hinge defines a central functional axis, and wherein each said central functional axis defines a rotation axis.

19. The reference gantry of claim 18, wherein the central functional axes of the hinges are arranged perpendicular to each other.

20. The reference gantry of any one of claims 17 to 19, wherein the first directional hinge is a trend hinge and wherein the second directional hinge is a plunge hinge.

21. The reference gantry of claim 20, wherein the plunge hinge is configured to receive an instrument via a directional shaft of the instrument.

22. The reference gantry of claim 21, wherein each instrument has a central functional axis for defining the direction of its main function, and wherein said central functional axis has an orientation defined by a trend angle and a plunge angle.

23. The reference gantry of claim 22, wherein the plunge hinge defines the plunge angle about its central functional axis, said plunge angle being an angle between the central functional axis of the instrument and a horizontal plane of the coordinate system; and wherein the trend hinge defines the trend angle about its central functional axis, said trend angle being an angle between the projection of the central functional axis of the instrument on the horizontal plane and a vertical plane of the coordinate system.

24. The reference gantry of any one of claims 21 to 23, wherein the instruments include one or more of: an additional reference grid; a reference gantry-translation unit for translating one or more bone segments; a reference gantry-rotating ring for rotating one or more bone segments; a reference gantry drilling guide for accurate positioning of screws or wires; and a reference gantry-milling drill for drilling, milling, reaming, and/or tapping one or more bone segments.

25. The reference gantry of claim 24, wherein the instruments include a reference gantry drilling guide, and wherein said reference gantry drilling guide comprises a directional shaft and a hollow cylinder for receiving a plurality of drilling bits, and wherein the reference gantry-milling drill comprises a chuck for receiving a plurality of milling or drilling bits, a motor for actuating the milling or drilling bits and a directional shaft.

26. The reference gantry of claim 24, wherein the instruments include a reference gantry-translation unit, and wherein said reference gantry-translation unit comprises a telescopic strut for actuating translation, a directional shaft and/or a translation unit-plunge hinge.

27. The reference gantry of claim 24, wherein the instruments include a reference gantry-rotating ring, and wherein said reference gantry-rotating ring comprises a ring plate, a housing unit for actuating rotation, and two or more directional shafts for coupling the reference gantry-rotating ring to the reference gantry-arm and/or for coupling the reference gantry-rotating ring to one or more independent instruments via one or more independent pairs of directional hinges.

28. The reference gantry of claim 27, wherein an independent pair of directional hinges comprises an independent instrument-trend hinge and an independent instrument-plunge hinge, and wherein said independent instrument-plunge hinge is attached to each independent instrument.

29 The reference gantry of claim 28, wherein the independent instrumenttrend hinge defines a first central functional axis; and wherein the independent instrument-plunge hinge defines a second central functional axis.

30. The reference gantry of claim 29, wherein the independent instrumenttrend hinge defines an independent instrument-trend angle about the first central functional axis with respect to a corresponding reference side of the reference gantry-rotating ring; and wherein the independent instrument-plunge hinge defines an independent instrument-plunge angle about the second central functional axis with respect to the said corresponding reference side.

31. The reference gantry of any one of claims 27 to claim 30, wherein each independent instrument defines a central functional axis, and wherein the said central functional axis has an orientation defined by the independent instrument-trend angle and the independent instrument-plunge angle.

32. The reference gantry of claim 31, wherein the independent instruments include the reference gantry-translation unit and a reference gantry-passive prismatic joint for dynamizing an associated fracture or osteotomy site.

33. The reference gantry of claim 32, wherein the reference gantry-passive prismatic joint comprises a passive prismatic joint-plunge hinge, and a dynamic barrel, and wherein said dynamic barrel adjustably translates along a telescopic shaft of the passive prismatic joint-plunge hinge.

34. A method of registration of an axis, a bone segment and/or an instrument by extrapolating coordinates, said method comprising the steps of:

providing a reference gantry according to any preceding gantry claim directly or indirectly dependent on claim 4;

connecting an additional reference grid to a reference grid of the base platform;

placing a bone segment and/or an instrument adjacent to the interconnected pair of reference grids;

orientating an imaging beam or scan of an imaging device, such that the imaging beam or scan is perpendicular to the imaging plane of the additional reference grid;

exposing the said additional reference grid, the bone segment and/or the instrument to imaging or scanning for generating a first planar view;

orientating the imaging beam or scan of the imaging device, such that the imaging beam or scan is perpendicular to the imaging plane of the reference grid of the base platform;

re-exposing the said reference grid, the bone segment and/or the instrument to imaging or scanning for generating a second planar view;

identifying at least two points of the axis, at least three noncollinear points of the bone segment, and/or at least three noncollinear points of the instrument in both planar views, wherein said points are either visually discernible in both planar views or identifiable by their known density or geometric properties in both planar views; and extrapolating three coordinates for each identified point by correlating each said identified point of the axis, each said identified point of the bone segment, and/or each said identified point of the instrument with the calibrated lines of the said reference grid and the said additional reference grid.

35. A method of registration of an axis, a bone segment and/or an instrument by calculating coordinates, said method comprising the steps of:

extrapolating pre-operatively the coordinates of at least three points according to claim 34;

defining a local coordinate system from the at least three registered points;

extrapolating the coordinates of at least two points of the axis, at least three noncollinear points of the bone segment, and/or at least three noncollinear points of the instrument;

defining a position vector for each point with reference to the local coordinate system;

calculating the magnitude of each position vector; normalizing each position vector;

calculating a plunge angle φ between each normalised position vector and a horizontal plane of the local coordinate system;

calculating a trend angle Θ between the projection of each normalised position vector on the horizontal plane and a vertical plane of the local coordinate system;

re-registering the local coordinate system; and calculating the coordinates of the at least two points of the axis, the at least three noncollinear points of the bone segment, and/or the at least three noncollinear points of the instrument by the trend and the plunge angle of their position vectors, and by the magnitude of their position vectors with reference to the re-registered local coordinate system.

36. A method of orientating a central functional axis of an instrument attached to the reference gantry-arm according to the orientation of a correction axis, said method comprising the steps of:

registering an axis defining a correction axis according to claim 34 or claim 35;

defining a vector by two registered points of the correction axis; normalizing the vector calculating a plunge angle φ between the normalised vector and a horizontal plane of the coordinate system defined by the reference gantry;

calculating a trend angle Θ between the projection of the normalised vector on the horizontal plane and a vertical plane of the coordinate system defined by the reference gantry;

placing a directional shaft of an instrument into the plunge hinge of the reference gantry-arm;

rotating the directional shaft of the plunge hinge to set the central functional axis of the instrument at trend angle Θ; and rotating the directional shaft of the instrument to set its central functional axis at plunge angle φ.

37. A method of registration of a central functional axis of an instrument attached to a reference gantry-arm, said method comprising the steps of:

orientating the central functional axis of the instrument attached to the reference gantry-arm according to claim 36;

calibrating an intersection point of the trend and plunge central functional axes for defining the coordinates of the intersection point;

defining two points of the central functional axis of the instrument; and correlating the coordinates of each said point with the coordinates of the intersection point for calculating the coordinates of each said point.

38. A method of using the kinematic mechanism of a reference gantry for substantially fully accomplishing reduction, said method comprising the steps of:

registering an axis defining an angulation correction axis according to claim 34 or claim 35;

connecting a reference gantry-rotating ring to the reference gantry-arm; orientating a central functional axis of the reference gantry-rotating ring, such that is parallel to the angulation correction axis;

registering the central functional axis of the reference gantry-rotating ring;

positioning the reference gantry-rotating ring such that its central functional axis is coincident with the angulation correction axis;

connecting one or more bone segments to the reference gantry-rotating ring;

reducing substantially fully the one or more bone segments by translating along the central functional axis of one or more stages of the reference gantry and/or rotating about the central functional axis of the reference gantry-rotating ring;

connecting one or more stationary bone segments to the reference gantry-rotating ring; and disconnecting the reference gantry-rotating ring from the reference gantry-arm.

39. A method of using the kinematic mechanism of a reference gantry for partially accomplishing reduction and for customizing an external fixator kinematic mechanism capable of accomplishing the remaining part of the reduction, said method comprising the steps of:

registering one or more axes defining an angulation correction axis and/or a translation correction axis according to claim 34 or claim 35;

connecting a reference gantry-rotating ring and/or a reference gantrytranslation unit to the reference gantry-arm;

orientating a central functional axis of the reference gantry-rotating ring, such that is parallel to the angulation correction axis; and/or orientating a central functional axis of the reference gantry-translation unit such that is parallel to the translation correction axis;

5 registering the central functional axis of the reference gantry-rotating ring;

positioning the central functional axis of the reference gantry-rotating ring such that is coincident with the angulation correction axis;

connecting the reference gantry-rotating ring and/or the reference 10 gantry-translation unit to one or more bone segments;

reducing partially the one or more bone segments about the angulation correction axis and/or along the translation correction axis;

connecting the reference gantry-rotating ring and/or the reference gantry-translation unit to one or more stationary bone segments;

15 disconnecting the reference gantry-rotating ring and/or the reference gantry-translation unit from the reference gantry-arm.

reducing substantially fully the one or more bone segments about the angulation correction axis and/or along the translation correction axis.

Intellectual

Property

Office

Application No: GB1717832.8 Examiner: Andrew Hughes