GB2108847A

GB2108847A - Ankle prosthesis

Info

Publication number: GB2108847A
Application number: GB08133514A
Authority: GB
Inventors: Arthur Jacob Helfet
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-11-06
Filing date: 1981-11-06
Publication date: 1983-05-25
Also published as: GB2108847B

Abstract

An ankle prosthesis comprises a first member adapted for attachment to the lower end of the tibia and a second member adapted for attachment to the upper end of the talus. The members cooperate with one another in such a way as to permit movement of the second member with the talus relative to the first member along a generally helical path. As the foot moves upwards it also pivots outwards, whereas as the foot moves downwards it also pivots inwards. <IMAGE>

Description

SPECIFICATION Ankle prosthesis This invention relates to an ankle prosthesis for implantation to replace a diseased or damaged natural joint.

According to the present invention there is provided an ankle prosthesis which comprises a first member adapted for attachment to the lower end of the tibia of the patient, and a second member adapted for attachment to the upper end of the talus of the patient, the first and second members cooperating with one another in such a way as to permit movement of the second member with the talus relative to the first member along a generally helical path, the path being such that as the foot of the patient moves upwards it also pivots outwards, whereas as the foot of the patient moves downwards it also pivots inwards.

The invention is explained further below with reference to the accompanying drawings in which: Figure 1 is a diagram of the natural ankle joint of a human being; Figures 2, 3 and 4 show the member adapted for attachment to the tibia in a side view, a section on line 3-3 of Figure 2, and a plan view, respectively; and Figures 5, 6, 7 and 8 show a member adapted for attachment to the talus in rear view, side view, a section on line 7-7 in Figure 6, and underplan view, respectively.

Turning to Figure 1, this shows the bones of a human ankle, namely the tibia 1 , the fibula 2, the talus 3 and the os calcis 4. The prosthesis of the present invention is designed to replace the natural joint between the tibia and the talus. This natural joint is indicated diagrammatically by a circle 5 in Figure 1.

Turning now to the embodiment of the invention shown in Figures 2 to 8, it must first be emphasised that the drawings are purely schematic and intended to show only the basic principle of the invention. The prosthesis shown in those Figures comprises a member 6, which is shown in Figures 2 to 4, for attachment to the tibia. The upper surface 7 of the member 6 is represented diagrammatically by a straight line, but would in practice have such shape as might be chosen for suitability as to its attachment to the tibia. Attachment could, for example, be by means of a cement. The wider end of the member 6, shown at the left-hand side of Figure 4, is at the front of the joint, and the narrower end is at the back. The underside of the member 6 is concavely curved as viewed in side view (see Figure 2) and carries a rib 8.As can be seen most clearly in Figure 4, this rib extends in a slanting fashion along the underside of the member 6.

Figures 5 to 8 show a member 9 for attachment to the talus. In use, the underside 10 of this member is the side which is attached to the talus, for example by a cement. The wider end of the member 9, shown at the right-hand side of Figure 8, is at the front of the joint, and the narrower end is at the back. The upper surface of the member 9 carries a groove 11 which, as can be seen in Figure 8, extends slantingly along the upper surface of the member 9. When the prosthesis is in place in an ankle joint the rib 8 engages in the groove 1 1 in such a way that the rib is able to slide backwards and forwards along the groove. The slanting dispositions of the rib and groove ensure that as the foot is moved upwards it simultaneously pivots outwards, whilst as the foot moves downwards it simultaneously pivots inwards. This simulates what is in fact the natural motion of the human ankle joint and so enables a person fitted with the prosthesis to move and otherwise use his or her foot in a way which corresponds closely to what would be the case if the natural joint were still present.

If desired, the prosthesis may be provided with side members extending along one or both of the joint regions indicated by 12 in Figure 1 , thereby providing extra stability.

Claims

1. An ankle prosthesis which comprises a first member adapted for attachment to the lower end of the tibia of the patient, and a second member adapted for attachment to the upper end of the talus of the patient, the first and second members cooperating with one another in such a way as to permit movement of the second member with the talus relative to the first member along a generally helical path, the path being such that as the foot of the patient moves upwards it also pivots outwards, whereas as the foot of the patient moves downwards it also pivots inwards.

2. A prosthesis according to claim 1, wherein one of the said members carries a rib which cooperates with a groove in the other of the said members, the rib and groove being slantingly disposed to provide the said movement along a generally helical path.

3. A prosthesis according to claim 2, wherein the said members are wider at one end of the rib and groove than at the other end of the rib and groove so as to permit the said slanting disposition.

4. A prosthesis according to claim 1, wherein the prosthesis is provided with at least one side member arranged to extend along a respective side of the talus to provide increased stability.

5. A prosthesis according to any preceding claim, substantially as herein described with reference to the accompanying drawings.