Biomechanical changes following surgical treatment of MTP-I-Osteoarthritis

Abstract Operative treatment of osteoarthritis of the first metatarsophalangeal joint (MTP I) produces gross modification to the anatomy of the joint. The purpose of this study was to evaluate biomechanical changes following two different surgical procedures, arthrodesis of the MTP I (group 2) and resection of the base of the proximal phalanx I (Keller 1904, Brandes 1929) in combination with transposition (McBride 1928, Joplin 1950) of the abductor hallucis tendon (group 3) compared with normal volunteers (group 1). Dynamic measurements of plantar foot pressures were used to evaluate the biomechanical conditions of the sole contact phase during normal gait. Measurements were obtained from 15 patients undergoing arthrodesis (group 2), 11 patients after resection of the base of the proximal phalanx I (group 3) and 20 volunteers with normal feet serving as a control (group 1). In group 2 there was a significant increase in pressure beneath the hallux and a decrease underneath the first metatarsal head in the push off phase of gait. Group 3 demonstrated a marked decrease in pressure underneath the hallux in the push off phase. There was no lateralisation of the load in patients in either of these groups compared with normal controls (group 1). The pressure over time course on the metatarsal heads was alterated by both surgical procedures. These post surgical changes should be taken into account for the differential indication between both these procedures for individual patients. In addition, marked biomechanical changes call into question the surgical treatment of simple hallux valgus in the absence of osteoarthritis.