Relationship between the medial cuneiform bone morphology and the severity of hallux valgus

Background It has been reported on the relationship between the medial cuneiform bone morphology, especially in terms of obliquity, and the severity of hallux valgus (HV), however, no consensus has been obtained. On the other hand, there are no reports on the relationship between the difference in height between the medial and intermediate cuneiforms and the severity of hallux valgus. The purpose of this study was to clarify the relationship between the medial cuneiform bone morphology and the severity of HV. Methods The authors retrospectively analyzed 200 feet of 116 patients who had a weightbearing anteroposterior foot radiograph taken between April 2017 and July 2022 and diagnosed with HV. Measurements included the hallux valgus angle (HVA), the intermetatarsal angle (IMA), the distal medial cuneiform angle (DMCA) and the cuneiform first-second length (C1-2D). HV groups were classified into one of three groups: mild (15 ≦ HVA<30°, 9 < IMA<13°), moderate (30 ≦ HVA<40°, 13 ≦ IMA≦20°) and severe groups (HVA≧40°, IMA>20°), and the relationship to DMCA or the difference in height between the medial and intermediate cuneiforms was analyzed. Results A total of 163 feet of 93 patients were included in this study. There were significant correlations between the HVA and the DMCA (r = 0.47, p < 0.001) or the C1-2D (r = 0.64, p < 0.001). There was no significant difference in DMCA between the mild and moderate groups (p = 0.14). On the other hand, significant differences in C1-2D were observed between the three groups (mild-moderate; p < 0.001, moderate-severe; p = 0.03, mild-severe; p < 0.001). IMA was also positively correlated with the DMCA (r = 0.30, p < 0.001) or the C1-2D (r = 0.47, p < 0.001). However, the DMCA (p = 0.07) and the C1-2D (p = 0.39) did not differ significantly from IMA between the moderate and severe groups. Conclusions The difference in height between the medial and intermediate cuneiforms, referred to as C1-2D, is closely associated with the HVA. The C1-2D may influence the progression of HV and be a novel radiographic parameter that indicates severity of HV.