Increased Intercuneiform and Naviculocuneiform Joint Spacing in Hallux Valgus: A 3-Dimensional Distance Mapping Pilot...

Hallux valgus (HV) is a complex 3-dimensional (3D) deformity of the first ray. Recurrence rates following surgical intervention for HV remain high, which may be due to unrecognized midfoot instability. Previous studies have suggested that instability at the first tarsometatarsal (TMT1) is the source of deformity, but separate work suggests that midfoot joints such as the intercuneiform (IC) and naviculocuneiform (NC) joints may also be involved. No studies have investigated whether joint space widening occurs in other joints along the medial column. The goal of this study was to compare spacing of midfoot joints between HV patients and controls.

A retrospective pilot study of 20 HV patients with preoperative weightbearing CT scans were identified and matched with 20 selected control patients. Midfoot bones were segmented from scans, and 3D distance mapping was performed to evaluate regional differences in minimum joint spacing at the TMT1, IC, and NC joints. The segmented WBCT scans were uploaded to Geomagic Design X, and automated coordinate systems for each bone were calculated using a previously published open-source code in Matlab. The TMT1 joint was divided into dorsal and plantar regions, the IC joint was divided into distal and proximal regions, and the NC joint was divided into medial and lateral regions.

Joint spacing was greater in the proximal IC joint of HV patients (0.95 mm, IQR: 0.89-1.02 mm), compared with controls (0.61 mm, IQR: 0.48-0.76 mm, P = .006). Spacing was also greater in the medial NC joint of HV patients (1.23 mm, IQR: 1.14-1.36 mm) compared with controls (1.11 mm, IQR: 0.93-1.24 mm, P = .007). With the numbers available, no significant difference was observed at the TMT1 joint.

HV patients demonstrated differences at the proximal IC and medial NC joints compared with controls, suggesting an association between proximal midfoot joint spacing and HV deformity. These findings highlight that structural changes in HV may extend beyond the TMT1 joint, and consideration of the broader midfoot in patients with HV may be relevant when evaluating the deformity.

Level III, retrospective cohort study, case-control study, meta-analysis of Level III studies.