Objective: Based on the anatomical study and clinical trial of transposition of the flexor pollicis brevis muscle (M. f. p.b.) for the reconstruction of thumb opposition, we suggested a new method for the treatment of irreparable median nerve injury which causes paralysis of the opponens pollicis and the abductor pollicis brevis muscles (M.a.p.b) and leads to loss of thumb opposition.
Material and methods: Anatomical study and biomechanic analysis were performed on 20 cadaveric hands and 8 patients who had been treated and followed up on an average for 12 months.
Results: The M.f.p.b. overlaps the M.a.p.b. for about half of its width at the muscle origins and the overlapping reduced to about 1/3 of the width at the muscle belley level. The M.f.p.b. chiefly inserted on the palmar aspect of the base of proximal phalanx. The M.a.p.b. primarily was inserted on the radial side of the first metacarpophalangeal(MP) joint, and the M.f.p.b. was entirely innervated by the deep branch of the ulnar nerve. In an attempt to increase the angle between longitudinal force lines of these two muscles for 7 degrees-9 degrees, we transferred the insertion of the M.f.p.b. to the radial side of the MP joint, so that it gives this muscle the function of opposition. Eight patients were treated and followed up on an average for 12 months. All had fine functional results.
Conclusions: This method is effective, and least traumatic, and does not need transposition of another tendon.