Inter-metacarpal Bone Graft for Thenar Paralysis

In 1930 Foerster described an operation for restoring opposition of the thumb in cases of paralysis of abductor brevis and opponens pollicis ; a bone graft was inserted between the first two metacarpals to maintain the thumb in palmar abduction and opposition. The method was elaborated by Thompson (1942) and the results in seven cases were reviewed. Both authors were satisfied that the function of the hand was considerably improved. The alternative operation of fusing the trapezio-metacarpal joint was tried by Stiles and ForresterBrown (1922), but they found, as did Lyle (1926), that the grip between the thumb and index was weak. That this is probably due to increased movement at the trapezio-carpal joint is substantiated by Muller (1949) who has found that a good range of movement of the thumb is retained after arthrodesis of the trapezio-metacarpal joint for osteoarthritis. This paper is based on a review of sixteen cases in which bone graft operations were performed for thenar paralysis from peripheral nerve lesions. Some unexpected sequelae have been encountered and have led to certain modifications in technique. Indications for operation-The sole indication for an opponens bone graft is permanent paralysis of the abductor brevis and opponens pollicis muscles for which tendon transplantation to restore active opposition cannot be performed. When flexor pollicis brevis and abductor pollicis longus are working strongly, control of the thumb is often good and no reconstructive operation is necessary. As Highet (1943) and Rowntree (1949) have shown, flexor brevis is often supplied by the ulnar nerve and may therefore be spared even in complete median palsy. The employment of the tendon of flexor sublimis to the ring finger as a motor tendon for opposition of the thumb has become almost as reliable as tendon transplantation for radial palsy; flexor or extensor carpi ulnaris, though less satisfactory, can also be used (Bunnell 1948, Irwin 1942, Thompson 1922). A tendon for transplantation is not available when these three muscles are either paralysed or weak. Lack of independent movement of muscles that have recovered after suture of a main nerve is a well-known phenomenon. Thus, after high suture of the median nerve, even though flexor profundus and flexor sublimis digitorum may contract strongly together, there is loss of independent contraction of flexor sublimis-one of the special merits of this muscle. Furthermore, scarring about the wrist may make tendon transplantation impossible. Under such circumstances stabilisation of the first metacarpal bone in the best position is indicated. Just as in tendon transplantation, any fixed adduction contracture, particularly of the skin, should be overcome before bone-grafting. If the deformity is secondary to shortening in the adductor pollicis muscle alone, it may be corrected either at operation or by means of preliminary stripping of the first metacarpal. The preliminary stripping was done in cases where there seemed to be some prospect of recovery in abductor pollicis brevis; in a few cases power returned soon after the over-stretching of the abductor had been corrected and there was then no need to proceed to the grafting operation. If the patient is in doubt about the benefit he will derive from the operation, trial plaster fixation of the thumb in the position of function will help him to make up his mind.