Biomechanical Evaluation Of Unilateral And Bilateral Locking Plate Fixation Of Distal Femoral Fractures With Metaphyseal Comminution

Objective: Recently, with the rapid development of urban construction,transportation, and the increasement of aging population, the incidence of complicated distal femoral fractures is increasing gradually. Treatment of these fractures is a tough work to orthopedic surgeons. The healing rate of distal femur fractures was improved apparently when the locking plate was applied in clinic. However, with the locking plate being widely used,complications of healing, including delayed union, nonunion, malunion,hardware failure were not infrequent. It is speculated that insufficient fixation strength of single lateral used locking plate is the main reason for these complications. In this study, we compare the biomechanical stability of uni- or bilateral locking plates to support clinical bilateral locking plate fixation of distal femoral fractures with metaphyseal comminution.Methods: AO/OTA C2.3 type fractures were made in 22 artificial femoral specimens(Sawbones 3403, Pacific Research Laboratories)with normal bone density, and divided into two groups randomly. In group A,the fractures were fixed with anatomic lateral locking plates, and in group B, the fractures were fixed by anatomical lateral locking plates and locking plates medially. Five Specimens in each group were performed axial compression test, Three of each group were performed cyclic axial loading test, and the other three specimens were performed failure load.The subsidence of medial cortex gap of metaphysics were measured during axial compression and cycle loading test. The maximum load were also recorded during failure loading.Results: For axial compression, the mean subsidence of group A was2.61±0.28 mm, group B was 0.46±0.08 mm, P<0.05; For cyclic axial loading, the mean subsidence of group A was 1.56±0.12 mm, group B was 0.43±0.05 mm, P<0.05; For failure load, the maximum load of group A was 5567±338N, group B was 9147±186N, P<0.05.Conclusions: For metaphyseal comminuted distal femoral fracture,bilateral locking plates provide more support to medial column of distal femur, increasing the stability of fixation, and help patients early functional rehabilitation exercise.