Supplementation of Lateral Locked Plating for Distal Femur Fractures: A Biomechanical Study.

Objectives: To investigate the biomechanical properties of a lateral locked plate alone or in combination with a supplemental medial plate or an intramedullary nail (IMN).

Methods: Intra-articular distal femur fractures with metaphyseal comminution (OTA/AO 33-C) were simulated with a standardized model in 28 synthetic femora and divided into 4 groups. Group I was instrumented with a 4.5-mm lateral locked distal femoral plate alone, group II with a lateral locked plate plus a low-profile precontoured 3.5-mm medial distal tibial plate, group III with a lateral locked plate plus a medial 3.5-mm reconstruction plate, and group IV with a lateral locked plate plus a retrograde IMN. Specimens were then axially loaded and cycled to failure or runout. Outcomes of interest were baseline stiffness, survivability, and cycles to failure.

Results: Groups III and IV have a significantly higher baseline stiffness (P < 0.001) when compared with groups I and II. Furthermore, groups III and IV had a higher max load to failure (P < 0.01) when compared with groups I and II. The survivability in groups III and IV was 71% and 100%, respectively, while no specimens in group I or II survived maximum loading. There was no significant difference between group III and IV regarding stiffness, survivability, and cycles to failure.

Conclusion: When considering fixation for intra-articular distal femur fractures with metaphyseal comminution (OTA/AO 33-C), we found that supplementation of a lateral locked plate with a medial plate or an IMN to be biomechanically superior to lateral locked plating alone regarding stiffness, survivability, and cycles to failure. A low-profile precontoured plate did not add significantly to the construct stiffness in this study.