Biomechanical changes in the lumbar and hip joint after curved periacetabular osteotomy.

Background: The alignment of the spine and pelvis significantly impacts overall body balance; therefore, alterations in hip and lumbar spine biomechanics following curved acetabular osteotomy (CPO) can help surgeons optimize acetabular correction. To achieve this goal, we conducted patient-specific finite element analyses to compare hip and lumbar disc contact pressure (CP) between patients with developmental dysplasia of the hip (DDH) and healthy individuals. Additionally, we examined the influence of CPO on the CP of both the hip and lumbar discs in patients with DDH.

Methods: We conducted finite element analyses of the hip and lumbar spine before and after CPO and compared them with those of a healthy human model. Subsequently, we simulated CPO on the preoperative model. Nonlinear contact analysis was employed to calculate the CP of the acetabular cartilage and lumbar discs during a single-leg stance.

Results: The maximum and average acetabular CP in patients with DDH were 5.4 MPa and 4.5 MPa, respectively. The average CP for the five lumbar discs were 3 MPa, 2.5 MPa, 2 MPa, 3.5 MPa, and 4.4 MPa. In contrast, the maximum and average acetabular CP in normal subjects were 3.7 MPa and 2.1 MPa, respectively, and the average CP of their lumbar discs were 1 MPa, 2 MPA, 1.88 MPa, 2.1 MPa, and 2.1 MPa, respectively. After CPO, the maximum and average CP of the hip decreased, as did the average CP of the lumbar discs. The maximum and average compressive stress of the acetabulum decreased to 3.79 MPa and 2.3 MPa, respectively, and the average compressive stress of the five intervertebral discs decreased to 1.96 MPa, 0.79 MPa, 0.78 MPa, 1.13 MPa, and 3.14 MPa, respectively.

Conclusion: Our finite element analysis indicated that CPO effectively normalizes hip contact pressure while reducing lumbar disc contact pressure. However, further investigation is required to elucidate the specific biomechanical mechanisms underlying these changes.