Radiographic Evaluation of Congruency of the First Metatarsophalangeal Joint in Hallux Valgus

Abstract Background Congruency of the first metatarsophalangeal (MTP) joint is extremely important for the selection of surgical methods and prognosis, while radiographic evaluation methods are relatively lacking. The purpose of this article was to explore radiographic indicators for evaluating congruency of the first MTP joint.Methods Patients who had a weightbearing X-ray in the outpatient system were selected, excluding patients with trauma, deformity, and history of surgery. A total of 183 patients with 245 feet were included. The hallux valgus angle (HVA), distal metatarsal articular angle (DMAA), metatarsophalangeal joint angle (MTPJA), congruency index (CI) and tibial sesamoid position (TSP) were measured and statistically analysed.Results The higher the degree of hallux valgus was, the higher the proportion of incongruency of the first MTP joint. Significant differences were found in the DMAA, MTPJA and CI between the congruency and incongruency groups of patients with moderate to severe hallux valgus (P<0.05). The areas under the curve (AUCs) of the receiver operating characteristic (ROC) curve for the MTPJA and CI were 0.906 and 0.884, the sensitivity values reached 0.791 and 0.949, the specificity values were 0.862 and 0.644, and the critical values were 10.67 and 0.765, respectively. The correlation test indicated that in the congruency group, the DMAA and HVA were positively correlated, but the MTPJA, CI and HVA had low correlation coefficients. The DMAA and HVA were not correlated in the incongruency group, while the MTPJA and HVA were significantly positively correlated and the CI and HVA showed a negative correlation (P<0.05).Conclusion The MTPJA and CI are indicators that can be used to quantitatively evaluate the congruency of the first MTP joint, taking 10° and 0.765 as the demarcation points, respectively. Clinically, congruency of the MTP joint should be considered when choosing surgical methods for different degrees of hallux valgus, and the MTPJA and CI can be used as quantitative evaluation indicators.Level of evidence: Level III, Retrospective Comparative Study