Biomechanical Study on the Stress Distribution of the Knee Joint After Distal Femoral Fracture Malunion With Residual Varus-valgus Deformity

Abstract BackgroundThis study aims to examine the biomechanical influence of residual varus and valgus deformity after malunion of distal femoral fractures on the knee joint. MethodsWe selected 14 adult cadaver specimens to establish the femoral fractures models and subsequently fixed them at neutral position and malunion positions, i.e. at 3°, 7° and 10° at valgus and varus positions, respectively. Ultra-low pressure sensitive film technology was used to quantitatively measure the stress distribution on the medial and lateral plateau of the tibia.ResultsAt neutral position, with 400 N vertical load applied, the stress values of the medial and lateral plateau of tibia were 1.162±0.114 MPa and 1.103±0.144 MPa, respectively. Compared with those measured at neutral position, the stress on the medial plateau of the valgus tibia significantly increased, while that on the lateral plateau of the valgus tibia significantly decreased (both P<0.05). In contrast, the stress on the lateral plateau of the valgus tibia significantly increased, while that on the medial plateau of the valgus tibia significantly decreased (both P<0.05). The medial plateau of tibia demonstrated significantly higher stress values than those on the lateral plateau at neutral position and 3°, 7°, 10° varus deformities, respectively (all P<0.05), but showed significantly lower values than the those on the lateral plateau at 3°, 7°, 10° valgus deformities, respectively (all P<0.05). ConclusionsThe residual varus and valgus deformities after mulunion of the distal femoral fracture resulted in significant changes of the stress distribution of the knee joint. Anatomical reduction and firm fixation of distal femoral fracture should be as possible to be obtained to avoid possible varus and valgus deformities.