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

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. 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. Seventy-seven patients (45 female, 32 male) were available for follow-up at a mean of 106.9&#x2009;&#xb1;&#x2009;25.3&#x2009;months. Radiographic osteoarthritis progression was significant in all assessed adjacent joints (&#x2009;<&#x2009;.001) and was most pronounced in the IP joint (66 of 77 joints; 34 of 77 joints progressed by &#x2265;2 grades). TMT1 progression occurred in 23 of 77 joints (&#x2265;2 grades in 5 of 77 joints), and NC or TN progression in 30 of 77 joints (&#x2265;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&#x2009;&#xb1;&#x2009;9.1, FAOS 86.4&#x2009;&#xb1;&#x2009;15.2, and FFI 18.5%&#x2009;&#xb1;&#x2009;9.3%. Wound healing complications were more frequent with dorsal plating than screw fixation. One nonunion required revision. 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.