GB2565793A

GB2565793A - Patient positioning apparatus

Info

Publication number: GB2565793A
Application number: GB1713464.4A
Authority: GB
Inventors: Langton David
Original assignee: PXD Ltd
Current assignee: PXD Ltd
Priority date: 2017-08-22
Filing date: 2017-08-22
Publication date: 2019-02-27
Anticipated expiration: 2037-08-22
Also published as: GB201713464D0; WO2019038536A1; GB2565793B

Abstract

A patient positioning apparatus with an arm assembly 8 connected to an arm support 2 wherein the arm assembly 8 has a patient engaging member 11 and is able to rotate relative to the arm support 2 and be locked in position. The arm support may have a mount 5 which it engages using a sliding rod 4. The rod 4 or shaft may be shaped so that it cannot rotate. The connection between the support and assembly may involve teeth which can be pushed to mesh together. The arm assembly may have first and second elements 9 which can slide relative to each other and each include a patient engaging pad 11. A threaded fastener may be used to lock the arm elements in position. A digital spirit level may be used to measure the angle of rotation of the arm assembly. The device is designed for use in hip replacement surgery.

Description

Patient Positioning Apparatus

Field of the Invention

The present invention relates to apparatus for positioning patients for surgical procedures and in particular to an apparatus for positioning a patient for hip replacement surgery.

Background of the invention

Prosthetic hip joints are routinely used to replace a patient’s hip joint when that joint is damaged. Many tens of thousands of such hip replacement operations are performed each year around the world.

The prosthetic hip joint typically comprises an acetabular prosthetic socket or cup, which is placed in the hip and a femoral head, which fits into the cup.

It has long since been appreciated that the acetabular cup substituting for the acetabulum has to be inserted into the pelvis in the correct orientation. However, the extent to which the acetabular cup is often incorrectly oriented has only been established in recent years.

The techniques used by orthopaedic surgeons for orienting the prosthetic acetabular cup range from the most basic “eyeballing”, where the surgeon uses his experience and orients the cup as he thinks best, with no particular equipment to assist him in establishing that the cup is correctly oriented, to very complex navigation systems, with basic spirit levels and laser beams mounted on the introducer falling in between.

The Applicant describes a prosthetic hip alignment apparatus in WO2014045064. The apparatus comprises a number of components. One of those components is a patient alignment instrument. One of the steps in the procedure described in W02014045064 is to orient the patient so that a datum line that lies on a vertical plane through the patient’s body when the patient is standing also lies on in a vertical plane when the patient is lying on an operating table. The patient alignment apparatus is used to check the two anterior superior iliac spines (ASIS) lie in a common vertical plane. The instrument comprises a rod with two spaced apart plates, each for engaging one of the ASIS and a spirit level. The position of the patient is manipulated until each plate is m contact with a respective one of the ASIS and the spirit level shows that the rod is vertical in all three planes.

It was recognised in W02014045064 that when lying on an operating table the pelvis may be tilted such that the axis b-b lies off vertical by up to 10 degrees to either side of the vertical.

The present invention is concerned with providing a better means of supporting a patient on an operating table and an improved means of measuring the angle of tilt of the pelvis when a patient is so positioned.

The hip is designed to function with the person in the standing position. However, hip replacement operations are performed with the patient lying down, usually on his side, with the hip to be replaced uppermost. The position occupied by the pelvis when the patient is lying down is different to the position occupied by the pelvis when the person is standing.

It would be desirable to provide an apparatus that would allow the prosthetic acetabular cup to be oriented as closely as possible to the desired orientation.

The prosthetic acetabular cup must be oriented in two planes. With the patient in the standing position it is desirable that the face of the cup should be aligned at 45 degrees to the vertical and that the face of the cup should lie at approximately 15 degrees of anteversion with respect to a vertical plane extending through the femoral balls.

Obtaining accurate information regarding the angle of tilt of the pelvis prior to performing hip replacement surgery and supporting the patient in a desired position during surgery can result in more successful outcomes for patients.

Summary of the Invention

According to the invention there is provided a patient positioning apparatus comprising an arm assembly, an arm support and connection means configured to connect the arm assembly to the arm support, wherein the arm assembly includes at least one patient engaging member, and wherein the connection means provides for selective rotational movement of the arm assembly relative to the arm support and selective locking in position of the arm assembly relative to the arm support.

The patient positioning apparatus may further comprise a member to which the arm support is mountable.

It is preferred that the arm support is mounted on the member by an arm support mounting means and the arm support mounting means provides for movement of the arm support towards and away from the member.

Advantageously, the arm support mounting means comprises a shaft and the shaft is slidably mounted in one or both of the member and the arm support.

Preferably, the shaft and at least one of the arm support and the member are shaped and dimensioned so as to prevent relative rotation between the shaft and said at least one of the arm support and the member.

The connection means may comprise first and second connector elements and the first element may include a first surface and the second connector element includes a second surface, the connection means including an engagement member adapted to exert a force selectively on the first and second elements, the force causing the first and second surfaces to engage with one another.

The first and second surfaces may include teeth and the teeth of one of the first and second surfaces may be so shaped and dimensioned as to mesh with the teeth of the other of the first and second surfaces.

It is preferred that the arm assembly includes first and second arm elements, and preferably one of the first and second arm elements is mounted on the other so as to slide relative thereto.

The arm assembly may further comprise a securing means configured to prevent relative sliding between the first and second arm elements.

The securing means may be provided by one of: the first and second arm elements being a tight fit within the other, a threaded fastener mounted in an outer one of the first and second arm elements and adapted to engage a surface of the other of the first and second arm elements, or a threaded fastener mounted in an outer one of the first and second arm elements and adapted to engage with one of a series of fastener receiving portions in the other of the first ands second arm elements.

Preferably, the at least one patient engaging member includes a pad.

The arm assembly may include two spaced apart patient engaging members and one of the patient engaging members may be mounted on one of the first and second arm elements and the other of the patient engaging members may be mounted on the other of the first and second arm elements.

The patient positioning apparatus may further comprise a measuring means configured to indicate the angle of rotation the arm assembly relative to the arm support.

The measuring means may include a spirit level and preferably a digital spirit level.

Brief Description of the Drawings

In the Drawings, which illustrate a preferred embodiment of patient positioning apparatus according to the invention:

Figure la is a schematic side view of the apparatus;

Figure lb is a schematic view of one component of the apparatus shown in Figure la;

Figure 2 is a schematic front view illustrating the apparatus shown in Figure la and a patient;

and

Figure 3 is a schematic side view illustrating the apparatus shown in Figure la and the patient.

Detailed Description of the Preferred Embodiments

Referring now to Figures 1 to 3, there is shown a patient alignment apparatus 1 comprising an arm support 2 including a hole 3. A bar 4 is attachable via a bracket 5 to an operating table 6. The arm support 2 attaches to the bar 4 via the hole 3 and preferably, the arm support 2 may slide on the bar 4 and/or the bar 4 may slide in the bracket 5. The sliding arrangement of the support 2 on the bar 4 or the bar 4 in the bracket 5 allows the support and those components mounted thereon, to move in the direction x-x across the operating table 6. This is useful as the apparatus may be adjusted to suit the position of the patient 15 on the operating table 6 rather than the patient 15 being moved to suit the position of the apparatus 1.

An arm assembly 8 comprises two arm elements 9, 9’, one of the arm elements 9’ being slidable on the other are element 9 in the direction z-z. In the illustrated example the arm element 9’ is larger in cross-section than the arm element 9, the arm element 9 sliding within the arm element 9’. Each arm element may be formed of a material that in cross-section may be one of: tubular, rectangular, channel shapes (with the larger element 9’ having an inward projecting return on each side wall) for example. A means to retain the arm elements 9, 9’ in a desired configuration is provided. This function may be provided by a number of alternative or complementary arrangements. For example, the fit of the arm element 9 within the arm element 9’ may be tight, so that a person may move the arm elements 9, 9’ relative to one another by application of force, but once the force is removed the arms 9, 9’ do not move further. Alternatively, a screw may be provided in a threaded hole in one of the arm elements 9, 9’. Depending on which of the arm elements 9, 9’ the threaded hole is provided in, either the end of the screw or the underside of the screw head will engage with the other of the arm elements 9, 9’ to lock the arm elements 9, 9’ in a desired position.

The arm assembly 8 includes pads 11, each attached to a respective one of the arm elements 9, 9’ by a spacer 10,10’. The pads 11 are brought up against the two ASIS 16, 16’ of the patient 15 shown lying on the operating table 6. The spacers 10, 10’ may provide for the respective pads 11, 11’ to rotate relative to the arm elements 9, 9’ or not.

The arm 8 serves two functions: the first being to support the patient in the position shown, with the front points two ASIS 16,16’ lying in a substantially vertical plane on axis a-a; and the second being to measure the angle of tilt of the pelvis, that is the angle of a line extending between the two ASIS 16, 16’ relative to the axis b-b. In Figure 2 the pelvis is not tilted meaning that a line extending between the two ASIS 16, 16’ lies parallel with the axis b-b.

The whole arm 8 may rotate about the axis y-y so that the angle of tilt of the pelvis may be measured and so that each ASIS 16, 16’ of a pelvis tilted relative to the axis b-b may be supported.

The support 2 and the arm element 9 have plates 7a, 7b respectively attached thereto. The face of each plate 7a, 7b is provided with a plurality of teeth 7c which mesh with one another, the teeth 7c extending radially from the centre of the plate and being spaced one degree apart as best shown in Figure lb.

The arm support 2 and each of the plates 7a, 7b include holes 2a, 7d, 7e respectively. The aforesaid holes are aligned so that an elongate fastener element may pass therethrough. The elongate fastener may comprises a threaded rod attached to the plate 7b, by threads or other means such as welding. A correspondingly threaded nut fastened on to such a threaded rod allows the plates 7a, 7b to be pressed together in a desired orientation. When a different patient is on the operating table 6, the fastening means may be released so that the toothed faces of the plates 7a, 7b may rotate relative to one another. When the pads 11 are aligned with the two ASIS 16, 16’ of the new patient the fastening means is tightened, locking the plate 7b relative to plate 7a.

Rather than a fastener passing through a hole 7e in the plate 7b these two parts may be machined as a single component.

Preferably, one of the plates 7a, 7b is provided with indicia indicating the angle of teeth 7c relative to the axis b-b and the other of the plates is provided with a marker or pointer so that when the position of the arm about the axis y-y is adjusted, the resulting angle relative to the axis b-b can be read off. Alternatively, or additionally, a digital spirit level may be provided for measuring the aforementioned resulting angle relative to the axis b-b.

Claims

1. A patient positioning apparatus comprising an arm assembly, an arm support and connection means configured to connect the arm assembly to the arm support, wherein the arm assembly includes at least one patient engaging member, and wherein the connection means provides for selective rotational movement of the arm assembly relative to the arm support and selective locking in position of the arm assembly relative to the arm support.

2. A patient positioning apparatus according to Claim 1, further comprising a member to which the arm support is mountable.

3. A patient positioning apparatus according to Claim 2, wherein the arm support is mounted on the member by an arm support mounting means and the arm support mounting means provides for movement of the arm support towards and away from the member.

4. A patient positioning apparatus according to Claim 3, wherein the arm support mounting means comprises a shaft and the shaft is slidably mounted in one or both of the member and the arm support.

5. A patient positioning apparatus according to Claim 4, wherein the shaft and at least one of the arm support and the member are shaped and dimensioned so as to prevent relative rotation between the shaft and said at least one of the arm support and the member.

6. A patient positioning apparatus according to any preceding claim, wherein the connection means comprises first and second connector elements and wherein the first element includes a first surface and the second connector element includes a second surface, the connection means including an engagement member adapted to exert a force selectively on the first and second elements, the force causing the first and second surfaces to engage with one another.

7. A patient positioning apparatus according to Claim 6, wherein the first and second surfaces include teeth and wherein the teeth of one of the first and second surfaces are so shaped and dimensioned as to mesh with the teeth of the other of the first and second surfaces.

8. A patient positioning apparatus according to any preceding claim, wherein the arm assembly includes first and second arm elements, and wherein one of the first and second arm elements is mounted on the other so as to slide relative thereto.

9. A patient positioning apparatus according to Claim 8, wherein the arm assembly further comprises a securing means configured to prevent relative sliding between the first and second arm elements.

10. A patient positioning apparatus according to Claim 9, wherein the securing means is provided by, one of the first and second arm elements being a tight fit within the other, a threaded fastener mounted in an outer one of the first and second arm elements and adapted to engage a surface of the other of the first and second arm elements, or a threaded fastener mounted in an outer one of the first and second arm elements and adapted to engage with one of a series of fastener receiving portions in the other of the first ands second arm elements.

11. A patient positioning apparatus according to any preceding claim, wherein the at least one patient engaging member includes a pad.

12. A patient positioning apparatus according to any of Claims 8 to 10, or to 11 when dependent on Claim 8preceding claim, wherein the arm assembly includes two spaced apart patient engaging members and wherein one of the patient engaging members is mounted on one of the first and second arm elements and the other of the patient engaging members is mounted on the other of the first and second arm elements.

13. A patient positioning apparatus according to any preceding claim, further comprising a measuring means configured to indicate the angle of rotation the arm assembly relative to the arm support.

14. A patient positioning apparatus according to Claim 13, wherein the measuring means is a digital spirit level.