Influence of Hip Geometry Reconstruction on Frontal Plane Hip and Knee Joint Moments During Walking Following Primary Total Hip Replacement.

Background: Following total hip replacement (THR), hip geometry reconstruction parameters such as the femoral offset (FO) correlate with hip stability and wear. The purpose of this study is to determine the relationship between hip geometry parameters and knee and hip joint loading during walking.

Methods: Forty-one patients were examined before and a minimum of 1 year after primary THR. Pearson correlation coefficient (r) was performed to identify relationships between radiographic parameters and gait data. In addition, we divided patients into 2 groups according to the restoration of the FO (within ±5 mm vs more than 5 mm increment).

Results: The FO and global offset (GO) showed a positive correlation with the first (r = 0.469, P = .002; r = 0.542, P < .001) and second (r = 0.365, P = .019; r = 0.484, P = .001) knee adduction moment (KAM). The neck-shaft angle revealed a negative correlation with the first hip adduction moment (r = -0.375, P = .047). The reconstruction of FO with an increment of more than 5 mm was associated with a significant higher first KAM (+16%, P = .045) compared to the restored group.

Conclusion: Our findings suggest that abnormal hip and knee joint loading during walking after THR have a biomechanical background originating from hip geometry reconstruction. Patients with a high FO/GO were more likely to have an increased KAM during walking or vice versa. Surgeons need to be aware that an accurate control of FO, GO, and neck-shaft angle restoration in THR has an impact on hip and knee joint loading that may influence degenerative changes of the knee and higher wear of the artificial hip joint, respectively.