Cumulated ambulation score as predictor of postoperative mobility in patients with proximal femur fractures

Introduction: The cumulated ambulation score (CAS) has been developed as an index for evaluating mobility in the early postoperative period. This study aimed to estimate the association between CAS and independent ambulation after surgery for proximal femur fractures. Materials and methods: This retrospective cohort study included 223 elderly patients who underwent surgery for proximal femur fractures and had independent ambulation before the injury. Multivariable logistic regression analyses with cognitive impairment, pre-injury Barthel index, and CAS as the test variables were used to predict independent ambulation at 2 weeks (model 1) and 3 months (model 2) postoperatively. We established scoring systems based on the modeling results. Results: The number of patients with independent ambulation at 2 weeks and 3 months postoperatively was 115 and 169, respectively. Univariate analysis showed that the CAS was significantly associated with independent ambulation at 2 weeks and 3 months postoperatively. Multivariable analysis showed that models 1 and 2 had good predictive accuracies, with areas under the receiver-operating characteristic curve of 0.855 and 0.868, respectively. Among the explanatory variables, only the CAS in model 2 was not significantly associated with the postoperative ambulatory ability. Scoring systems for both models 1 and 2 also had good predictive accuracies, with cut-off scores of 3.5 for model 1 and 9.5 for model 2. Conclusions: The CAS predicted independent ambulation at 2 weeks postoperatively; however, this relationship was limited at 3 months postoperatively. Therefore, the CAS may help estimate independent ambulation at discharge from an acute-care hospital.