Modified Boyes' procedure for the multiple finger extensor tendon ruptures in patients with rheumatoid arthritis: A report of two cases.

Multiple subcutaneous extensor tendon ruptures in more than the ulnar three fingers sometimes occur in patients with rheumatoid arthritis accompanied by wrist deformity. In these situations, the flexor digitorum superficialis tendon of the middle finger (the FDS3 tendon) and that of the ring finger (the FDS4 tendon) are used for the transferred tendon (modified Boyes' procedure). Here, we treated two patients with rheumatoid arthritis, whose extensor tendons of more than three fingers were ruptured, using the modified Boyes' procedure. Case 1 had ruptures in four fingers (index through little), and Case 2 had ruptures in three fingers (middle through little). The FDS3 and FDS4 tendons were passed subcutaneously around the radial side of the wrist to the extensor sides and interlaced with the distal stump of the ruptured tendons. Switching of the finger movement was achieved smoothly in both cases. The post-operative evaluation showed an extension lag of -15° for the index finger 0° for the middle through the little fingers in Case 1, and 0° for the middle finger and -5° for the ring and little fingers in Case 2. The average post-operative extension lag was -3.5°. However, median nerve palsy occurred in both cases, and it gradually recovered. Stretching of the nerve by the correction of the wrist deformity and increased pressure in the carpal tunnel were supposed to be causes of this palsy. Modified Boyes' procedure is a useful method for more than three ulnar finger extensor tendon ruptures; however, post-operative median nerve palsy should be considered.