Second Ray Pathologies Associated with Hallux Valgus: A Radiographic Comparative Study.

Background: Specific factors associated with different pathological mechanisms on the second ray in hallux valgus deformity (HV) are underrepresented in the literature. This study aimed to compare radiographic features of HV with distinct second ray pathologies and identify factors associated with specific second ray pathological conditions. Methods: This retrospective cross-sectional study compared preoperative radiographic measurements between patients with HV who underwent isolated HV surgery (HV group), HV surgery with a concurrent procedure for lesser metatarsophalangeal (MTP) joint lesions (MTP group), and HV surgery with arthrodesis for tarsometatarsal (TMT) joint osteoarthritis (TMT group). Results: The TMT group demonstrated significantly higher radiographic parameters representing first ray hypermobility (first metatarsal-medial cuneiform angle and first TMT dorsoplantar gap), midfoot instability (first-second metatarsal distance), and flatfoot deformity (talonavicular coverage angle and lateral Meary's angle) than other groups. The MTP group had a significantly longer second metatarsal length. Factors associated with the MTP group were first metatarsal-medial cuneiform angle (odds ratio [OR], 0.845), lateral Meary's angle (OR, 0.757), and second metatarsal length (OR, 7.384). Factors associated with the TMT group included talonavicular coverage angle (OR, 1.323), first TMT dorsoplantar gap (OR, 5.345), and lateral Meary's angle (OR, 1.387). Conclusions: HV without radiographic features of midfoot instability tended to be associated with lesser MTP joint lesions, whereas HV with radiographic features of midfoot instability was more commonly associated with lesser TMT joint osteoarthritis. Further prospective longitudinal studies are required to clarify causal relationships among these associations.