Enhancing fixation strength in periprosthetic femur fractures by orthogonal plating-A biomechanical study.

Orthogonal plate osteosynthesis enhances fixation stability in periprosthetic femur fractures. Another option are locking attachment plates (LAP) allowing bicortical locking screw placement lateral to the prosthesis stem. Stability of lateral plate osteosynthesis with two LAP (2LAP) was compared to anterolateral orthogonal plate osteosynthesis (OP) with one LAP in a periprosthetic femur fracture model. In six pairs of fresh frozen human femora with cemented Charnley hip prosthesis, a transverse osteotomy was set distal to the tip of the prosthesis simulating a Vancouver type B1 fracture. Each pair was instrumented using a plate tensioner with either one lateral plate and two LAP, or two orthogonal anterolateral plates and one LAP. Stiffness was determined in a four-point-bending test prior to cyclic testing (2Hz) with physiologic profile and progressively increasing load up to catastrophic construct failure. Paired t-test and Wilcoxon-signed-rank test were used for statistical evaluation at a level of significance p = 0.05. The OP construct exhibited a significantly higher number of cycles and load to failure (39,627 cycles ± 4,056; 4,463 N ± 906) compared to the 2LAP construct (32,927 cycles ± 3,487; 3,793 N ± 849), p < 0.01. Mediolateral bending and torsional stiffness of the OP (1610 N/mm ± 249; 16.9 Nm/mm ± 6.3) were significantly higher compared to 2 LAP (1077 N/mm ± 189; 12.1 Nm/mm ± 3.9), p = 0.03 for both comparisons. Orthogonal plate osteosynthesis is a valuable option in periprosthetic fracture surgery, offering increased stability compared to a single lateral plate fixed with two LAP.