Metaphyseal Screw Augmentation of the LISS-PLT Plate With Polymethylmethacrylate Improves Angular Stability in Osteoporotic Proximal Third Tibial Fractures

Abstract

The incidence of osteoporotic proximal tibial fractures has increased during the last 2 decades. A promising approach in osteoporotic fracture fixation is polymethylmethacrylate-based cement augmentation of implants to gain better implant purchase in the bone. This study investigates the biomechanical benefits of screw augmentation in less invasive stabilization system-proximal lateral tibial (LISS-PLT) plates in cadaveric extraarticular comminuted proximal tibial fractures (OTA-41-A3.3). Standardized extraarticular proximal tibial fractures were stabilized with the LISS-PLT plate in 6 paired osteoporotic cadaveric tibiae. Bone mineral density was measured with high-resolution, quantitative computed tomography scans to identify bone quality. In the augmented group, the 5 proximal screws of the LISS-PLT plate were augmented with 1 mL of bone cement each, whereas the contralateral tibia was instrumented conventionally as the control. Cyclic axial loading was applied to each specimen with a starting load of 150 N, using a ramp of 0.05 N per cycle to 10-mm axial displacement. Varus displacement was identified from anterior-posterior radiographs. Bone mineral density showed no significant difference between the 2 groups (P = 0.47). The nonaugmented group reached 9417 load cycles (SD 753) until failure, compared with 14,792 load cycles (SD 2088) in the augmented group (P = 0.002). In the early-onset failure (deformation at 8250 load cycles), varus displacement was significantly smaller in the augmented group (0.46 degrees, SD 0.6) than in the nonaugmented group (3.23 degrees, SD 1.7) (P = 0.01). This biomechanical study showed that cement augmentation of the LISS-PLT plate screws in osteoporotic proximal extraarticular tibial fractures significantly lowers the propensity toward screw migration and secondary varus displacement.