Radiological study of the secondary reduction effect of early functional exercise on displaced intra-articular calcaneal fractures after internal compression fixation

Purpose Early post-operative exercise and weight-bearing activities are found to improve the functional recovery of patients with displaced intra-articular calcaneal fractures (DIACFs). We hypothesized that early functional exercise after surgery might have a secondary reduction effect on the subtalar joint, in particular the smaller fracture fragments that were not fixed firmly. A prospective study was conducted to verify this hypothesis. Methods From December 2012 to September 2013, patients with unilateral DIACFs were enrolled and received a treatment consisting of percutaneous leverage and minimally invasive fixation. After surgery, patients in the study group started exercising on days two to three, using partial weight bearing starting week three, and full weight bearing starting week 12. Patients in the control group followed a conventional post-operative protocol of partial weight bearing after week six and full weight bearing after the bone healed. Computed tomography (CT) scanning was performed at post-operative day one, week four, week eight, and week 12 to reconstruct coronal, sagittal, and axial images, on which the maximal residual displacements of the fractures were measured. Function was evaluated using the American Orthopaedic Foot and Ankle Society (AOFAS) scoring scale at the 12th post-operative month. Results Twenty-eight patients in the study group and 32 in the control group were followed up for more than 12 months; their data were collected and used for the final analysis. Repeated-measures analysis of variance (ANOVA) of the maximal residual displacements of the fracture measured on CT images revealed significant differences between the study and the control groups. There were interaction effects between group and time point. Except for the first time point, the differences between the groups at all studied time points were significant. In the study group, the differences between all studied time points were significant. Strong correlations were observed between the AOFAS score at post-operative month 12 and the maximal residual displacement of the fractures on the CT images at postoperative week 12. Conclusions Early functional exercise and weight bearing activity can smooth and shape the subtalar joint and reduce the residual displacement of the articular surface, improving functional recovery of the affected foot. Therefore, early rehabilitation functional exercise can be recommended in clinical practice.