Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Leg – Adjustable shank or thigh
Patent
1988-10-26
1991-05-07
Green, Randall L.
Prosthesis (i.e., artificial body members), parts thereof, or ai
Leg
Adjustable shank or thigh
623 27, A61F 262
Patent
active
050133250
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an artificial leg or leg prosthesis of the kind including a tube, an adjusting head arranged in the proximal end of the tube and intended for attaching the prosthesis to a sleeve mounted on the leg for adjusting the angular position of the tube relative an imagined load line.
A prior art leg prosthesis is illustrated in FIG. 1 and has a tube 1 which is upwardly articulately attached to a head 3 via a first joint 2, the head 3 in turn being attached to an outer sleeve 4, which is arranged on an inner sleeve 5, which is pushed over the stump 6 of the leg. Downwardly, at the distal end of the tube, there is a second articulate joint 7 attached to a foot 8. The chain-dotted line 9 denotes the socalled load line, i.e. an imaged line extending between the foot joint (represented by the joint 7) and the knee, the body weight ideally acting along this line.
An incorrect adjustment means that the wearer of the leg prosthesis loads the leg unnaturally, which results in that when the patient walks the movement pattern of the prosthesis will be unnatural, and also that where there is a knee joint, it and the leg muscles will be unnaturally loaded. In connection with the manufacture of the sleeve 4, the head 3 is moulded in plastics in the best possible position relative the load line 9. In the final walking test, an adjustment must usually be made, partly with the aid of the articulate joint 2 so that the joint 7 coincides with the load line 9, and partly with the joint 7 so that the foot is given the best attitude relative the ground plane. The structure can be linked to a tube with lockable universal joints at each end.
The disadvantage with this design principle is that the distal adjustment means, i.e. the joint 7, has a weight which gives an undesirable, distal loading moment on the stump left after amputation. A clear tendency in orthopedics is that the artificial foot is made as light as possible and that possible adjustment means are placed in the upper part of the prosthesis.
If the entire adjustment means is to be placed in the proximal or upper end of the prosthesis, and if it is to have the same adjustment facilities as in the structure described above, it must have both an angular adjustment facility such as the articulate joint 2 and a rectilinear translatory adjustment facility substantially in the horizontal plane.
There are structures where the final prosthesis tube is sustituted during trials by a temporary tube having at its upper end an adjusting instrument, e.g. a Hosmer instrument, which allows both angular and translational adjustment. After walking tests with the prosthesis and subsequent adjustment thereof, the entire prosthesis is placed in a fixture where the temporary tube and its adjustment instrument is replaced by the final prosthesis tube, which is moulded to the outer sleeve 4 with the aid of a thermosetting resin.
The advantage with this design principle (which is used more and more) is that the finished prosthesis will be light. However, the disadvantages are inter alia the time-consuming extra moulding of the tube, which usually requires a further fitting visit by the patient, and the relatively heavy adjusting instrument which loads the leg during the walking trial with a weight other than that of the final prosthesis. When the final prosthesis tube has been moulded in, no adjustment facility remains. This latter disadvantage is serious, since, particularly in amputations, the stump changes its shape due to the changes in swelling during the healing process. It is then often necessary not only to modify the inner sleeve 5, but is some times also desirable to make an extra adjustment of an angular and/or translatory nature.
Another known prosthesis uses the same method with an adjusting instrument and fixture aS described above, but provides the final prosthesis tube with an adjustment head allowing certain limited extra adjustment facilities. The disadvantages with this known prosthesis are also the required extra fitting visit by the patient, the h
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Green Randall L.
Willse David H.
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