Background:​ The success of the operative treatment of mild to moderate hallux valgus (HV) relies greatly on the osseous union of the osteotomies at the desired position. Full weight-bearing is often allowed immediately postoperatively with special forefoot off-loading shoes. No precise methodology exists for the estimation of foot immobilization inside those shoes. The aim of this study was to assess the reliability of a new radiological measurement method to assess the immobilization of the first metatarsophalangeal (M1P1) joint inside a postoperative forefoot off-loading rocker shoe.

Methods:​ A prospective single-center study was conducted during 2012. Patients operated on for mild or moderate HV deformity with a percutaneous technique by the same surgeon were included. Twenty-four patients (33 feet) fulfilled the inclusion criteria, all women and mean age of 56.6 ± 12.7 years. Standard lateral foot X-rays were obtained 1 week postoperatively with the patient standing in 2 positions, wearing the same forefoot off-loading rocker shoe:​ the foot flat on the ground (imitating midstance) and on the toes (imitating propulsion). The main evaluation criterion was the immobilization of the M1P1 joint estimated through the difference between the values of the M1P1 angle in the sagittal plane in these positions. Validity and reliability of this new measurement were assessed with Pearson’s correlation coefficients (r) and intraclass correlation (ICC, ρ) coefficients.

Results:​ The inter- and intraobserver reliability of the measurement was excellent to good. The mean M1P1 angle was 17.5 ± 7 degrees in the position imitating the midstance and 20.7 ± 7.5 degrees in the position imitating propulsion (P < 10⁻⁵).

Conclusion:​ This new radiological measurement for assessing immobilization of the M1P1 joint was a valid and reliable method.

Level of Evidence:​ Level II, diagnostic study.