Surgery – Truss – Pad
Patent
1981-04-15
1983-03-08
Apley, Richard J.
Surgery
Truss
Pad
128 92C, A61F 104, A61F 504
Patent
active
043757030
DESCRIPTION:
BRIEF SUMMARY
This invention concerns endoprosthetic bone joint devices, and more particularly such devices for the metacarpal phalangeal (hereinafter referred to as MCP) joints.
Endoprosthetic MCP joint devices are already available and are probably best known in a form devised by Swanson involving a one-piece elongate structure of silicone rubber providing terminal portions for respective location in the bones of the joints, and a hinge portion interconnecting the terminal portions. Other forms of MCP devices have been proposed in which separate terminal components are provided and mechanically interlinked by respective mutually articulatory portions. Although the general form of these prior MCP joint devices has been subject to some variety, it is a common feature of all such devices that they are applied individually to joints in a one-to-one manner.
In practice, MCP joint devices are frequently used to combat the results of advanced rheumatoid arthritis and in this event it is common for all of the MCP joints of a hand to be replaced by individual devices. However, this situation is one which is accompanied by so-called ulnar drift in the hand, with the MCP joints becoming subluxated by lateral and dorsal-palmar shear forces, and the consequent movement of the extensor tendons from longitudinal alignment exacerbating the situation.
Moreover, experience indicates that, while the provision of a set of MCP joint devices in such a situation can provide relief for a time, device failure is highly likely and recurring deterioration almost inevitable because the underlying condition remains unchanged and will give rise to stress in the individual devices in a similar manner to that which affected the original joints.
An object of the present invention is to improve this situation and it is proposed in general terms that this be achieved by mechanically interlinking two or more MCP devices in order to effect a mutual stabilisation of the devices and to distribute thereover the deleterious stresses applied to individual ones of the devices.
To this end the present invention provides, in a presently preferred form thereof, an endoprosthetic MCP joint assembly comprising a plurality of devices which each include a pair of components for respective connection to the bones of an individual MCP joint, and which devices include a common hinge pin member for hingedly connecting the components of each of said devices.
Preferably the phalangeal component of each device of the assembly comprises two sub-components of which one is connectable to the bone and the other of which is connectable with the hinge pin member, said other sub-component being slidably and rotatably receivable in said one sub-component.
Also it is preferred that the hinge pin member have slight longitudinal curvature.
It is also preferable that the components should be restrained against dislocation from the pin, and this can be effected by providing stops at the ends of the pin, at least one such stop being separately connectable to the axle, suitably by provision thereof in the form of a snap fit cap. This last feature is appropriate for the presently intended surgical procedure in which the components are first secured to their respective bones and the pin threaded through the components thereafter. Also, it may be appropriate for the two components of each device to be directly connectable, suitably by a snap fit, to facilitate threading of the pin therethrough.
In order that the above and other features of the invention may be more clearly understood, the invention will now be described by way of example with reference to the accompanying drawings, in which:
FIG. 1 is a half-sectional side view, taken on I--I in FIG. 2, of one embodiment of a device according to the invention, and
FIG. 2 is an end view of said embodiment.
The assembly of the illustrated embodiment is denoted as a whole by reference numeral 10 and comprises a plurality of similar MCP joint devices 11 of which only one is shown for the sake of simplicity. Each device includes a phalangeal comp
REFERENCES:
patent: 3909853 (1975-10-01), Lennox
patent: 3939496 (1976-02-01), Ling et al.
patent: 3990117 (1976-11-01), Pritchard et al.
patent: 4011603 (1975-03-01), Steffee
patent: 4063314 (1977-12-01), Loda
patent: 4131957 (1979-01-01), Bokros
Evans David M.
Weightman Barry O.
Apley Richard J.
Isabella David J.
National Research Development Corporation
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