Arthrodesis of the first metatarsophalangeal joint for hallux rigidus—Optimal position of fusion

Abstract Background Good results are usually reported after arthrodesis of the first metatarso-phalangeal joint, but there is no definite agreement concerning the position that provides the best result. Methods We reviewed 35 patients with 39 fusions of the first metatarso-phalangeal joint 8 (2–15) years after surgery. In addition to clinical evaluation we measured the position of the arthrodeses radiographically and clinically, and also the distribution of pressure under the foot using insoles with pressure sensors. Results A total of 28 of 39 cases had an AOFAS score of 75 or better (90 best possible). Almost all patients experienced pain relief. Union was observed in 31 out of 39 feet, but the satisfaction rate was not significantly lower in those with pseudarthrosis. There was no strong correlation between the arthrodesis position and patient satisfaction. There was a good correlation ( r = 0.8; p < 0.001) between the weight-bearing radiographic extension angle and the height between the plantar surface and the pulp of the hallux and a flat board manually pressed against the sole of the foot. There was significantly increased local pressure under the pulp of the great toe in operated feet. Conclusions There is only a weak correlation between position and clinical outcome. A good estimate of the extension angle is made by measuring the height between a flat object placed under the foot and the pulp of the distal phalanx.