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

Abstract

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.

Three-dimensional computed tomography mapping and analysis of distal femur fractures (AO/OTA types 33A, 33B, and 33C)

“…All the bone models used for biomechanical tests in the above studies were composite models instead of cadaveric femurs. For the intercondylar osteotomy plane of the fracture model in these studies (20)(21)(22), a sagittal cut was made directly between both condyles through the intercondylar notch.…”

“…In type C fractures, the distance from the lower border of the fracture line hot zone to the joint line was approximately 5 cm, and the perpendicular length of the hot zone was about 4 cm. Although the distance of the hot zone measured on the femur template can only be used as a reference, osteotomy gaps created in the former studies (18)(19)(20)(21)(22) were not long enough to accurately simulate the fracture morphology, which may underpower the results drawn from those studies. According to the scale of the template model, we suggest that for type A fracture model, the osteotomy gap should be made approximately 4 cm and the supracondylar osteotomy at 4 cm proximal to the joint line.…”

Biomechanical Analysis and Design Method for Patient-Specific Reconstructive Implants for Large Bone Defects of the Distal Lateral Femur

“…In vitro biomechanical cyclic load tests were conducted as previously reported to compare the mechanical performance between femur defects repaired with a bone scaffold implant and bone cement [ 5 , 6 ]. The femur used for the experiment was made of composite synthetic bone (Femur, 4th Gen., Composite, 17 PCF Solid Foam Core, Small, Sawbones Inc., Vashon, WA, USA).…”

“…This procedure results in considerable bone defects that require biological reconstruction. A liquid-nitrogen–inactivated autograft is commonly used for such reconstruction [ 3 , 4 , 5 , 6 ]. For larger tumors, bone defects remain after surgical reconstruction, making the overall support structure relatively fragile.…”

Distal femural fractures. Surgical options

“…To reduce the risk of mechanical failure with varus collapse, some authors, including Zhibiao 33 , Ziran 34 and Fontenot 35 suggested adding a medial plate in the osteosynthesis of superdiacondylar fractures in case of metaphyseal comminution. In his study, Zhibiao used a double plate in 12 of 60 cases having the indication for a double stabilization when, after having fixated the fracture with a lateral plate, the varus test of the construct is positive.…”