Mono- versus polyaxial locking plates in distal femur fractures: a prospective randomized multicentre clinical trial

Treatment of complex fractures of the distal femur utilizing monoaxial locking plates (e.g. Less Invasive Stabilisation System, LISSA (R), Synthes) is considered to be superior to conventional plating systems. Due to the limitation that the thread forces the screw into pre-determined positions, modifications have been made to allow screw positioning within a range of 30A degrees (Non Contact Bridging, NCBA (R)-DF, Zimmer). For the first time, this multicenter prospective randomized clinical trial (RCT) investigates the outcome of LISSA (R) vs. NCBA (R)-DF treatment following complex fractures of the distal femur. Since June 2008, 27 patients with a fracture of the distal femur (AO ASIF 33-A-C and periprosthetic fractures) were enrolled in this study by four university trauma centres in southern Germany. Clinical (e.g. range of motion, Oxford knee score, Tegner score) and radiological (e.g. axis deviation, secondary loss of realignment) follow-ups were conducted one and six weeks, as well as three, six, and 12 months after the operation. This study comprises data of 27 patients (8 male, 19 female; 15 NCBA (R)-DF, 12 LISSA (R)). Polyaxial osteosynthesis using the NCBA (R) system tended to result in better functional knee scores and a higher range of motion. Interestingly, fracture union tended to be more rapid using the polyaxial plating system. We present the analysis of a multicenter prospective RCT to compare the monoaxial LISSA (R) vs. the polyaxial NCBA (R)-DF treatment following complex fractures of the distal femur. NCBA (R)-DF treatment tended to result in better functional and radiological outcomes than LISSA (R) treatment. Level I.