Osteoarthritis across the entire medial column in hallux valgus: arch alignment marks the midfoot, bunion severity the first metatarsophalangeal joint

Hallux valgus is treated as a first-ray deformity, and radiographic osteoarthritis beyond the first metatarsophalangeal joint is rarely examined. We asked how it is distributed along the medial column and whether its location is associated with bunion severity or arch collapse. Cross-sectional study of preoperative weight-bearing radiographs of 254 feet in 143 patients. Two orthopaedic surgeons independently graded the five medial column joints with the OARSI foot atlas, each blinded to the other. Because the adjudicated consensus record was unavailable, the primary outcome was a consensus surrogate; prevalence and the headline associations are also reported for each reader. Analyses used patient-clustered generalised estimating equations and Benjamini–Hochberg adjustment. Reliability was moderate: ICC(2,1) 0.55 (95 % CI 0.51–0.60) for osteophytes and 0.45 for joint space narrowing. Any degenerative change was present at 69.7% of first metatarsophalangeal (MTP) joints, 23.2% of talonavicular, 14.6 % of naviculo-first-cuneiform and 7.5% and 3.5% of first and second cuneo-metatarsal joints. The prevalence order was identical under all five reader combinations. Bunion angles were associated with first MTP involvement (intermetatarsal angle odds ratio 1.64 per SD, 1.14–2.34) but not with midfoot involvement; arch collapse was associated with talonavicular and naviculo-first-cuneiform involvement (calcaneal pitch 0.60 and 0.52, four-index planus composite 1.66 and 2.13, all pBH = 0.038) but not with first MTP involvement. Joint × exposure interaction tests supported the contrast in both directions. In feet undergoing hallux valgus correction, radiographic osteoarthritis extends well beyond the first ray, in an order shared by every reader combination: from most to least often involved, the first MTP, talonavicular, naviculo-first-cuneiform, first and second cuneo-metatarsal joints. Bunion severity was associated with first MTP involvement and arch collapse with midfoot involvement. Midfoot grading was only moderately reliable, so a single reader’s midfoot estimate should be treated as a range. These findings rest on a surrogate for the adjudicated consensus grades, which were unavailable. This study adds a two-reader grading of the whole medial column in preoperative hallux valgus, showing that bunion and arch alignment are associated with different joints.