Correlation Between X-Ray and Weight-Bearing Computed Tomography for Imaging Evaluation of Hallux Valgus Deformity

CATEGORY: Bunion; Midfoot/Forefoot INTRODUCTION/PURPOSE: Weight-bearing computed tomography (WBCT) has emerged as a valuable diagnostic tool for foot and ankle pathologies. Hallux valgus deformity values are well described in the literature, but there is a lack of correlation studies between x-rays and WBCT for the most widely used imaging parameters. The role of coronal plane deformity has gained importance in the last few years as a recurrence predictor factor. Most radiological descriptions in this topic are indirect measures of this rotational deformity. WBCT seems more precise to evaluate hallux valgus 3D deformity. Purpose: Correlate Hallux Valgus deformity parameters, metatarsal head morphology, and sesamoids position on x-rays compared to WBCT. METHODS: Hallux valgus (HVA), intermetatarsal (IMA), interphalangeal (IFA), and the distal metatarsal articular angle of the first metatarsal (DMAA) was measured on standing AP load-bearing radiographs (WBXR) and WBCT by 2 observers in hallux valgus patients. Deformity parameters obtained by both imaging methods were correlated with the Spearman Correlation (SCC) and the Intraclass Correlation Coefficient (ICC). Also, WBXR was analyzed to estimate the first metatarsal head rotation (pronation) by the round sign and sesamoids position. Then, direct pronation measurement was measured on WBCT by obtaining the Alpha Angle (AA) and sesamoids position in relation to the metatarsal head was defined. The Kappa concordance index (KCI) was determined. RESULTS: 40 feet with Hallux Valgus were evaluated. In WBXR the medians of HVA, IMA, IFA, and DMAA were 24.5, 12, 8.98, and 13.08 degrees respectively. In WBCT the medians were 24.75, 12.93, 6.05, and 13.03 respectively. The SCC was 0.934 for HVA, 0.956 for IMA, 0.713 for IFA, and 0.487 for DMAA, and the ICC was excellent for HVA, IMA, and IFA for both methods, excellent for DMAA in WBXR, but poor for WBCT. For rotation deformity, the correlation between metatarsal head morphology and AA was poor with a KCI of -0.073, and also for the position of the sesamoids between both methods and the KCI was 0.061. CONCLUSION: Evaluated deformity parameters had an excellent correlation between WBXR and WBCT. Both methods are useful for determining HVA, IMA, and IFA in Hallux Valgus patients, but it was poor for DMAA. Also the correlation between first metatarsal head morphology on WBXR (Round sign) with metatarsal head pronation (Alpha Angle) on WBCT was poor, as well as sesamoids position. Given greater WBCT precision to evaluate rotational deformity, we believe it should be considered in the diagnostic process to most accurately understand this complex deformity.