Can we recreate intraoperative weight bearing in hallux valgus surgery? A radiographic study using a reproducible technique of load bearing to simulate weight bearing

Introduction: Correction of the hallux valgus angle, intermetatarsal angle and sesamoid subluxation in hallux valgus surgery is key to restoring normal joint biomechanics. This is difficult to judge accurately intraoperatively as the foot is not weight bearing. We examine the reproducibility of a simulated weightbearing test on intraoperative images. Methods: This is a prospective study of 20 patients undergoing a scarf osteotomy for hallux valgus. All patients were operated by one fellowship trained surgeon and were excluded if they had inflammatory arthropathy. At the time of surgery, two intraoperative images were taken after surgical correction. A standard positional anterior posterior (AP) image was taken followed by a reproducible simulated weight bearing view (i.e. load bearing view). A retrospective review of 6 week and 4-6 month weight bearing images was conducted to assess any measurable differences in a separate group of patients. Results: The mean preoperative HVA was 30.7, IMA was 14.5, sesamoid position was 5.6. On completion of surgical correction the HVA was 6.6, IMA was 7.2 and sesamoid position was 1.8. On simulated weight bearing with an average of 131.2N (range 98.9-163.5N), the HVA was 8.9, IMA was 10.7 and sesamoid position was 2; this was a closer approximation to the 6-week weight bearing view in all indices recorded. No observed difference was noted between 6 week and 3-6 month weight bearing images. Conclusions: We have found that our standardized simulated load bearing intraoperative view will yield reproducibility and is a good surrogate marker for the 6-week weight-bearing radiograph. We believe locking the ankle joint will avoid rotation of the foot and allow for an accurate evaluation of final correction (HVA, IMA, and sesamoid position) and aid meaningful evaluation of surgical technique. However, it does not represent a final united position therefore we could not recommend its use in isolation.