Three-Dimensional Distance Maps Demonstrate Intercuneiform and Naviculocuneiform Joint Involvement in Hallux Valgus Patients Compared with Matched Control Patients

Submission Type: Hallux Valgus Research Type: Level 3 - Retrospective cohort study, Case-control study, Meta-analysis of Level 3 studies Introduction/Purpose: Hallux valgus (HV) is a complex three-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 source of the deformity, but separate work suggests that midfoot joints such as the intercuneiform (IC) and naviculocuneiform joints may also be involved. No studies have investigated whether joint space widening may occur in other joints along the medial column. The primary purpose of this study was to determine if there were differences in medial column joint space distances in HV patients compared with patients with no foot deformity using 3D distance maps (DMs) on weightbearing CT (WBCT) scans. Methods: Twenty-one patients (12 female) with HV who had a preoperative WBCT scan were retrospectively identified and matched with 20 control patients (12 female) with no foot deformity or arthritis who underwent a WBCT scan. Matching was performed based on age, sex, and body mass index. Semi-automatic bone segmentation was performed for each WBCT scan using Disior Bonelogic. 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. Minimum normal distances extracted from the joint DMs were then calculated for each region. Unpaired t-tests were then used to determine if there were differences in joint spaces between HV and control patients. Results: There were no significant differences in minimum joint distances at the dorsal and plantar regions of TMT1 (P-values>0.31), distal region of the IC joint (P=0.66), or lateral region of the NC joint (P=0.08) between HV and control patients (Figure 1). However, at the proximal region of the IC joint, the mean minimum distance between joint surfaces was 0.95 +/- 0.14 mm for the HV patients and 0.74 +/- 0.26 mm for the control patients (P=0.002). At the NC joint, HV patients had significantly increased minimum distance in the medial region of 1.27 +/- 0.19 mm for the HV patients compared with 1.10 +/- 0.20 mm for the control patients (P=0.009). Conclusion: Our study found widening of the proximal aspect of the IC and medial aspect of the NC joint spaces in HV patients. This suggests a more valgus alignment of the medial cuneiform in relation to the navicular and middle cuneiform, which may be compensatory to the varus deformity of the first metatarsal in HV (Figure 1). This widening may reflect involvement of the more proximal joints of the medial column of the foot in HV and may be a source of recurrence. Further work examining surgical stabilization of these midfoot joints may help to decrease recurrent rates after HV surgery.