[Secondary tendon reconstruction on the thumb]

Influence of the flexor digitorum superficialis tendon transfer on grip strength

The flexor digitorum superficialis tendon of the ring finger can be transferred to the thumb flexor. We followed ten patients after such a transfer for 5-128 months and measured grip strength and force transmission of the fingers and individual phalanges while the patients gripped 10-cm or 20-cm diameter cylinders. The grip strength of the middle, ring and little fingers was reduced when gripping the 10-cm cylinder, with a significantly larger decrease in the ring finger. With the 20-cm cylinder, grip forces of all fingers were almost identical, with slightly lower force of the ring finger and slightly higher forces in the index and small fingers. We conclude that after transfer of flexor digitorum superficialis tendon from a ring finger, grip strength of the ring finger is reduced. Finger forces are more hampered while gripping objects with smaller circumferences than large ones.

[Extensor tendon injuries of the thumb]

Extensor tendon injuries of the thumb include lesions of the tendons of the extensor pollicis longus, extensor pollicis brevis and abductor pollicis longus muscles. The latter is practically only affected in open injuries. Open injuries require a tendon reconstruction by suture followed by immobilization in the distal and an adequate aftercare depending on the zone of injury. In distal injuries static splinting is applied, whereas proximal injuries from T4 on require a dynamic after-treatment. Different courses of the tendon of the extensor pollicis brevis muscle exist distal to the metacarpophalangeal joint and must be considered. The rare ruptures of the extensor hood at the metacarpophalangeal joint provoke an ulnar displacement of the extensor pollicis longus or both extensor tendons with concomitant lack of active extension in the metacarpophalangeal and interphalangeal joints. This injury is often misdiagnosed as a rupture of the ulnar collateral ligament of the metacarpophalangeal joint. It should be treated by refixation of the ruptured structures. Closed chronic ruptures of the extensor pollicis longus tendon go along with a defect that requires a tendon transfer or a tendon autograft.

[Secondary reconstruction of flexor tendons]

The secondary reconstruction of flexor tendons is in most cases very demanding and tedious. The indications, selection of the correct surgical procedure, operative technique and further treatment have to be individually adjusted and are mostly very difficult. Due to the previous operations unpleasant surprises may occur intraoperatively, which must be recognized and treated by the surgeon. Nevertheless, a significant improvement of the function of the whole hand can be achieved for most patients, e.g. by a two-stage flexor tendon transplantation or other techniques described in this article.