Lesser metatarsophalangeal joint replacement arthroplasty for degenerative joint disease: development in vitro of a new design

Abstract

Background Isolated lesser metatarsophalangeal joint arthritis is often post traumatic or due to Freiberg’s infraction. The condition is initially treated conservatively with modification of life style, nonsteroidal anti-inflammatory agents, orthotics and even intra-articular hydrocortisone injections. When conservative treatment is no longer effective, surgery is considered as the condition can become very debilitating. This is an in vitro study of a new design replacement arthroplasty. Methods A three component joint replacement implant was developed following accurate skeleton measurements. Fifteen fresh frozen cadaver feet were utilized over a period of four years. The implant evolved in its design until finally the last four implanted devices were tested for mobility and stability using custom made equipment. Once the surgical technique was perfected, a further two devices were implanted by an independent surgeon to establish the surgical reproducibility. Furthermore, the implant was subjected to dynamic wear and fatigue testing in the laboratory under various compressive forces. Results Cyclical loading for wear and tear under physiological forces showed almost no sign of wear or surface deformation after 5 million cycles. Range of motion was well within the functional range and the implant was stable with forces in both dorsiflexion and dorsal displacement beyond the described forces for disrupting the joint. The surgical technique was found to be reproducible. Conclusion This novel lesser metatarsophalangeal joint replacement arthroplasty has been developed to fill the void of surgical options in the isolated arthritic lesser metatarsophalangeal joint. This implant is the basis for clinical trials.