Floating knees: variables affecting bone union and functional outcomes: a retrospective study of 72 cases

INTRODUCTION: Floating knee involves concomitant and ipsilateral fractures of the femur and tibia, sometimes associated with a patellar fracture. Complications are common, and functional outcomes are often poor. This study aimed to evaluate bone healing and to identify factors influencing nonunion and functional results. METHODS: This retrospective study included 72 knees, with a mean follow-up of 4.5 years. The primary outcome was bone union. Neurological, vascular and meniscoligamentous injuries were analyzed. Follow-up parameters were clinical, radiological and functional, including the Karlström and Olerud score. RESULTS: At least one fracture was open in 69% of cases. Mean time to union was 10.5 months for the femur, 7.5 months for the tibia, and 4.4 months for the patella. Nonunion occurred in 68% of femoral fractures, 57% of tibial fractures, and 42% of patellar fractures. Open fractures and tibial vascular injuries were significant predictors of nonunion. Meniscoligamentous injuries were diagnosed in 32% of cases and were more frequent with increasing Ran stage (p = 0.004). Surgical site infection occurred in 30.6% of cases and was significantly associated with open fractures (p < 0.001). Functional outcomes worsened with increasing Ran stage, meniscoligamentous injuries, open fractures, and infection. CONCLUSION: Floating knee injuries are characterized by prolonged healing, high rates of nonunion and infection, and limited functional outcomes.