Weightbearing CT 3-D Mapping of First Metatarsophalangeal and Sesamoid Joint Interactions in Hallux Valgus: A Case-Control Study.

Abstract

Background: Traditional methods of evaluating Hallux Valgus (HV) have limitations in assessing 3D deformity elements such as first metatarsal pronation and sesamoid subluxation. This study aimed to use coverage mapping (CM) to analyze surface interactions of the first metatarsophalangeal joint (MTPJ) and metatarsosesamoid joints in HV and control patients, correlating findings with visual analog scale (VAS) pain scores. We hypothesized that patients with HV would show decreased joint coverage, reflective of joint subluxation, and that these changes would correlate with higher VAS scores.

Methods: A distance mapping (DM) algorithm was applied to weightbearing computed tomography (WBCT) images from 44 symptomatic HV patients and 43 controls. Color-coded CMs were obtained from these distance measurements and were divided into quadrants for analysis. Regions showing joint space widths <5 mm indicated normal intraarticular coverage. VAS scores were obtained from the electronic medical record at the time of clinical assessment. Angular measurements were semiautomatically obtained, including the hallux valgus angle (HVA) and first metatarsal rotation angle (MRA). Statistical analyses included paired t tests, Wilcoxon tests, and regression models.

Results: CM revealed significant reductions in joint coverage in HV patients, particularly in specific quadrants of the first MTPJ and metatarsosesamoid joints. No association was found between CM features and VAS scores. Higher VAS scores were associated with younger age, lower MRA, and higher BMI.

Conclusion: 3D WBCT CM revealed significant subluxation and deviation in HV patients. VAS scores were influenced by demographic variables and metatarsal rotation, but not CMs, suggesting unique challenges beyond subluxation and pain. WBCT mapping generates hypothesis-generating visualizations of HV deformity; prospective studies are required before it can guide diagnosis or surgical planning.