Surgical treatment of patients with painful instability of the second metatarsophalangeal joint.

An unstable second metatarsophalangeal joint may produce pain in the forefoot. Eighteen patients (20 feet) had a transfer of the flexor digitorum longus to the extensor side of the base of the proximal phalanx performed as the primary procedure to stabilize this painful joint. Most patients had a hallux valgus deformity that also required correction, because it either was also symptomatic or was preventing adequate reduction of the second toe. A ruptured plantar plate of the second metatarsophalangeal joint was demonstrated in 13 feet and in these joints appeared to be the cause of the vertical instability. However, all feet showed an unstable joint upon clinical examination. A vertical-stress test almost always reproduced the patient's pain while demonstrating instability in the joint; this was the most prominent physical finding in these patients. Eleven patients (13 feet) had an excellent result. Seven patients (seven feet) had a fair result, but they complained only of mild and occasional pain at the joint on exertion. Although difficult to quantify, it appears that postoperative stiffness in the joint provided some of the joint stability seen in our patients. The flexor tendon transfer appears to be a satisfactory method to treating the unstable metatarsophalangeal joint and of relieving patients' pain, but may not, however, restore a normal alignment of the second toe. Correction of other forefoot deformities as hallux valgus and hammertoes may also be important in restoring metatarsophalangeal stability.