Risk Factors for Knee Stiffness in Distal Femoral Fractures

Abstract

Financial support: None. Conflict of interests: None. Purpose: The aims of this study were to evaluate risk factors for knee stiffness after the fixation of distal femoral fractures, and to analyze the clinical and radiologic outcomes. Materials and Methods: This is a retrospective case control study of 104 consecutive patients who have a distal femoral fracture and were treated with a submuscular locking plate. The case group comprised of patients with 12-month postoperative range of motion (ROM) ≤90° or a history of manipulation under anesthesia. The case group was compared with the control group of patients with a 12-month postoperative ROM >90°. The possible risk factors were evaluated by univariate and logistic regression analysis. The postoperative ROM and Knee Society clinical rating system was evaluated for the clinical assessment and the distal femoral angle on a whole-extremity scanogram was measured for radiologic assessments. Results: Fifty-four patients were included in the study (14 in the case group, 40 in the control group). Univariate analysis showed that comminuted fracture, intra-articular fracture, open fracture, temporary external fixation, severe osteoarthritis, and prolonged immobilization placed patients at an increased risk for knee stiffness. On the other hand, multivariate logistic regression showed that an extensor mechanism injury was the only significant predictor (p=0.001; odds ratio, 42.0; 95% confidence interval, 5.0-350.7). The ROM and Knee Society score were significantly lower in the case group; however, the coronal alignment was similar in the case and control group. Conclusion: Various factors that delay postoperative knee motion place patients at increased risk of knee stiffness. Understanding these risk factors may help surgeons prevent postoperative knee stiffness after distal femoral fractures. In particular, extensor mechanism injury, such as patella fracture or open quadriceps injury, was found to be an independent predictable factor associated with knee stiffness.