The Association of Bohler's Angle With Postoperative Pain and Gender for Displaced Intra-Articular Calcaneal Fracture, Multicenter Retrospective Study—TRON Study

A relationship between Böhler angle (BA) before or after surgery and clinical outcomes remains unclear. This retrospective multicenter cohort study aimed to compare pain and functional outcomes between a group in which the reduction angle was preserved and a group in which the reduction angle was lost during follow-up, and to clarify the risk factors leading to loss of last follow-up BA. From 2014 to 2018, 271 cases of calcaneal fractures were surgically treated at ten facilities. We divided patients into Group L (lost reduction of fracture) and Group P (preserved reduction of fracture). We matched subjects between the 2 groups according to age, sex and BA before surgery and compared American Orthopedic Foot and Ankle Society (AOFAS) score between the groups. We investigated the correlation between the amount of BA loss and postoperative pain. The factors leading to loss of last follow-up BA were examined by logistic regression analysis. Ultimately, 112 patients were eligible. After matching, each group included 38 patients. There was no difference between the 2 groups in total AOFAS score. However, the pain component of AOFAS score at 6 months and 12 months were worse in group L than in group P (p = .011, p = .031, respectively). We also showed a weak correlation between the amount of BA loss and postoperative pain. Logistic regression analysis revealed that female and BA before surgery independently predicted loss of reduction (odds ratios: 4.66, 95% CI: 1.15-18.9 and odds ratios: 0.90, 95% CI: 0.82-0.99, respectively). We clarified that reduction and preservation of BA within its normal range should lead to decrease postoperative pain. Female and lower pre-BA were risk factors leading to loss of reduction of BA in operative treatment of calcaneal fractures.