Sesamoid malalignment in hallux valgus: Radiographic and MRI measurements and their correlation with internal derangement findings of the first metatarsophalangeal joint

Abstract

Objective: Sesamoid displacement (SD) and rotation are important components in the preoperative assessment of hallux valgus (HV). To date, Inter reader reliability (IRR) of SD on X-rays and MRI, correlations with hallux valgus angle (HVA), and qualitative changes of the hallux-sesamoid complex (HSC) on MRI have not been studied. The aim of this study was to correlate sesamoid malalignment with HV severity and findings of internal joint derangement. Methods: Two readers analyzed a series of 56 consecutive patients who had X-rays and MRI performed on the same foot within 3 months of each other. Multiple measures of SD on X-rays and MRI and the sesamoid rotation angle (SRA) on MRI were assessed and correlated with HVA and various qualitative features at the HSC including cartilage, plantar plate, and collateral ligament abnormalities. Results: We found excellent IRR (ICC = 0.79 – 0.99) for SRA on MR, but poor IRR for lateral sesamoid displacement (LDS) and tibial sesamoid position (TSP) scales on both modalities. Good IRR was also seen for morphologic abnormalities of HSC. The absolute value of the SRA on MR positively correlated with HVA ( p < 0.0001). LDS and TSP on both modalities lacked a significant correlation with HVA ( p > 0.05). No correlation was found between any measure of SD or rotation with HSC morphologic changes ( p > 0.05). Conclusion: Among different measures of sesamoid malalignment, sesamoid rotation angle measured on MRI can be used to judge the severity of HV; however, it does not correlate with qualitative morphologic abnormalities of the HSC. Advances in knowledge: The MRI measurement of SRA is a better indicator of sesamoid displacement relative to the HSC than standard AP radiographic measures of non-rotational sesamoid displacement; however, it should not be used to predict qualitative morphologic abnormalities of the HSC.