Analysis of Stress Distribution on the First-Second Intercuneiform Joint and Associated Factors in Patients With Hallux Valgus: A Computed Tomography–Based Study

BackgroundInstability of the first cuneiform (C1)-second cuneiform (C2) joint (C1C2J) is a risk factor for hallux valgus (HV) recurrence after first tarsometatarsal joint arthrodesis. This instability could be associated with mechanical stress on C1C2J. This study aimed to investigate the stress distribution on C1C2J in patients with HV based on subchondral Hounsfield unit (HU) values and determine the associated factors.MethodsWe retrospectively reviewed 123 feet with HV. The control group included 29 feet without HV. The HU value of the subchondral bone was measured on coronal slices of preoperative computed tomography in 8 regions of C1C2J: anterodorsal (AD), anteroplantar (AP), posterodorsal (PD), and posteroplantar (PP) regions of C1 and C2. The HU values of C1C2J were divided by those of the fourth metatarsal (HU ratio). The HU ratios were compared between the HV and control groups, and the relationship between the HU ratios and radiographic parameters was compared in the HV group.ResultsThe HU ratios were significantly higher in the HV group than in the control group in AD, AP, and PD regions of C1 and C2. In the HV group, the HU ratios were negatively correlated with the calcaneal pitch angle (CPA) in all regions (r = -0.56 to -0.32) and Meary's angle (MA) in all regions of C1 and AD, AP, and PD regions of C2 (r = -0.41 to -0.21). Furthermore, the HU ratios were significantly higher in all regions for CPA under 15 degrees. The HU ratios were significantly higher in AD, AP, and PD regions of C1 and C2 for MA under -4 degrees. There was no correlation between the HU ratio and the HV angle.ConclusionsPatients with HV had higher stress loads on C1C2J than those without HV. This stress was associated with the medial longitudinal arch.