Long-term Outcomes After First Metatarsophalangeal Joint Arthrodesis: With Focus on Degenerative Changes on Adjacent Joints

Background: First metatarsophalangeal joint arthrodesis is a reliable treatment for painful end-stage degenerative, inflammatory, and post-traumatic conditions and severe deformities of the first ray. Although long-term functional outcomes are well documented, the incidence and relevance of degenerative changes in adjacent joints of the medial column after first metatarsophalangeal joint (MTP1) fusion remain uncertain. Methods: This exploratory single-center follow-up study included patients who underwent isolated MTP1 arthrodesis between 2012 and 2018. Preoperative and final follow-up weight-bearing radiographs were assessed for osteoarthritis progression in the interphalangeal (IP), tarsometatarsal (TMT1), naviculocuneiform (NC), and talonavicular (TN) joints using the Kellgren-Lawrence classification. Radiographic alignment parameters (hallux valgus angle, intermetatarsal angle, hallux-ground angle, and dorsal extension angle) were recorded. Clinical outcome was evaluated using American Orthopaedic Foot & Ankle Society hallux metatarsophalangeal-interphalangeal score (AOFAS HMI) score, Foot and Ankle Outcome Score (FAOS), Foot Function Index (FFI), and a study-specific questionnaire. Paired statistical tests and Pearson correlation analyses were performed. Results: Seventy-seven patients (45 female, 32 male) were available for follow-up at a mean of 106.9 ± 25.3 months. Radiographic osteoarthritis progression was significant in all assessed adjacent joints (P < .001) and was most pronounced in the IP joint (66 of 77 joints; 34 of 77 joints progressed by ≥2 grades). TMT1 progression occurred in 23 of 77 joints (≥2 grades in 5 of 77 joints), and NC or TN progression in 30 of 77 joints (≥2 grades: NC 6 of 77, TN 8 of 77). Radiographic alignment was not associated with adjacent-joint osteoarthritis progression, metatarsalgia, or patient-reported outcome. Overall, 90.9% reported good or excellent satisfaction. The mean AOFAS HMI score was 79.9 ± 9.1, FAOS 86.4 ± 15.2, and FFI 18.5% ± 9.3%. Wound healing complications were more frequent with dorsal plating than screw fixation. One nonunion required revision. Conclusion: MTP1 arthrodesis provides excellent long-term satisfaction and functional outcomes with low revision rates. Although radiographic adjacent-joint degeneration, particularly involving the interphalangeal joint, may occur over time, these changes do not appear to influence clinical outcomes.