Abstract
Acetabular dysplasia results in a shallow acetabulum, which reduces femoral head contact, leading to overloaded cartilage and high risk of early osteoarthritis. Periacetabular osteotomy (PAO) is a surgical procedure used to correct acetabular alignment before cartilage degeneration occurs. There is limited data on how PAO affects joint contact pressures. This study aims to analyze the joint mechanics in dysplastic hips before and after PAO during tasks such as squatting and walking.
CT scans were taken before and after PAO for six participants (2 males, 4 females, ages 18-43) with acetabular dysplasia. They performed squatting and walking tasks in a lab pre- and post-surgery. An optoelectronic camera system recorded pelvis and limb displacement, while force platforms measured ground reaction forces. Joint angles and reaction forces were calculated from this data using personalized musculoskeletal models in OpenSim. Joint contact areas and pressures were simulated using a discrete element model with patient-specific bone meshes and cartilage surfaces generated based on Nishii’s method. Peaks in contact area, maximal pressure and mean pressures were compared with the Wilcoxon test.
Walking results showed a significant increase in peak joint contact area post-surgery (6.5 ± 1.5 cm2 to 8.1 ± 2.4 cm2, p = 0.03), though no significant changes were found in peak max pressure (17.2 ± 3 MPa to 15.5 ± 3.9.4 MPa, p = 0.56) and peak mean pressure (7.0 ± 0.9 MPa to 5.2 ± 1.5 MPa, p = 0.09). There was no significant change in peak contact area (6.3 ± 1.7 cm2 to 7.0 ± 1.6 cm2, p = 0.31) nor in peak max and mean pressures (13.9 ± 5.6 MPa to 13.6 ± 2.6 MPa; 5.7 ± 2.8 MPa to 4.6 ± 0.8 MPa) for the squat.
PAO improved joint contact area in dysplastic hips during walking, although this did not lead to significant changes in peak pressures. In high-flexion activities like squatting, lateral acetabular repositioning may not fully offset the loss of posterior coverage. Although all metrics’ means moved in the desired direction, the benefits of PAO to reduce peak stresses are not apparent in this small cohort.