Off-axis view radiographs for assessing hallux valgus interphalangeus in hallux valgus deformity: A comparison with the traditional anteroposterior standing radiographs

The newly described anteroposterior "off-axis view" (OAV) radiograph might help detect a hallux valgus interphalangeus (HVI) deformity more precisely compared to anteroposterior standing radiographs.A radiographic assessment of HVI angles was performed using preoperative standing anteroposterior and OAV radiographs for 67 ft. Intra- and interobserver agreement for all angles and their correlation with HV severity were analyzed.The proximal-to-distal phalangeal articular angle showed less intra- and interobserver variance (intraclass correlation coefficient: 0.825) than did the other angles. OAV radiographs showed less interobserver reliability than did standing radiographs. HVI was underestimated significantly, by up to 5°, on standing radiographs compared to OAV radiographs (p0.001). The mean differences between OAV and standing radiographs were 3.7° and 5.0° for the proximal-to-distal phalangeal articular and hallux interphalangeal angles, respectively, and were more pronounced for moderate-to-severe HV deformities.Angular measurements of HVI on traditional anteroposterior standing radiographs are significantly smaller than on OAV radiographs. Furthermore, angular measurements on OAV radiographs are associated with higher interobserver reliability. The most precise angle representing an HVI deformity might be the proximal-to-distal phalangeal articular angle.Our findings may facilitate preoperative decision-making for additional akin osteotomy in HV correction.Level II.