Exploring pelvis and thigh movement and coordination patterns during walking in patients after total hip arthroplasty

Background: Patients after total hip arthroplasty (THA) have altered hip kinematics compared to healthy controls, specifically hip extension and range of motion are lower. Exploring pelvis-thigh coordination patterns and coordination variability may help to elucidate why differences in hip kinematics are evident in patients following THA. Research Question: Do sagittal plane hip, pelvis and thigh kinematics, and pelvis-thigh movement coordination and coordination variability differ between patients following THA and healthy controls during walking? Methods: Sagittal plane hip, pelvis and thigh kinematics were collected using a three-dimensional motion capture system while 10 patients who had undergone THA and 10 controls walked at a self-selected pace. A modified vector coding technique was used to quantify pelvis-thigh coordination and coordination variability patterns. Peak hip, pelvis and thigh kinematics and ranges of motion, and movement coordination and coordination variability patterns were quantified and compared between groups. Results: Patients after THA have significantly (p ≤.036; g ≥ 0.995) smaller peak hip extension and range of motion, and peak thigh anterior tilt and range of motion compared to controls. Additionally, patients following THA have significantly (p ≤.037; g ≥ 0.646) more in-phase distally and less anti-phase distally dominated pelvis-thigh movement coordination patterns compared to controls. Significance: The smaller peak hip extension and range of motion displayed by patients following THA is due to smaller peak anterior tilt of the thigh, which in turn limits thigh range of motion. The lower sagittal plane thigh, and in turn hip, motion used by patients after THA may be due to increases in the in-phase coordination of pelvis-thigh motion patterns, which cause the pelvis and thigh to work as a singular functional unit