Center of Mass Compensation during Gait in Hip Arthroplasty Patients: Comparison between Large Diameter Head Total Hip Arthroplasty and Hip Resurfacing

Objective . To compare center of mass (COM) compensation in the frontal and sagittal plane during gait in patients with large diameter head total hip arthroplasty (LDH-THA) and hip resurfacing (HR). Design . Observational study. Setting . Outpatient biomechanical laboratory. Participants . Two groups of 12 patients with LDH-THA and HR recruited from a larger randomized study and 11 healthy controls. Interventions . Not applicable. Main Outcome Measures . To compare the distance between the hip prosthetic joint center (HPJC) and the COM. The ratio (R HPJC-COM ) and the variability (CV HPJC-COM ) were compared between groups. Hip flexor, abductor, and adductor muscle strength was also correlated between groups while radiographic measurements were correlated with the outcome measures. Results . In the frontal plane, HR shows less variability than healthy controls at push-off and toe-off and R HPJC-COM is correlated with the muscle strength ratios (FR ABD ) at heel contact, maximal weight acceptance, and mid stance. In the sagittal plane, LDH-THA has a higher R HPJC-COM than healthy controls at push-off, and CV HPJC-COM is significantly correlated with FR FLEX . Conclusions . One year after surgery, both groups of patients, LDH-THA and HR, demonstrate minor compensations at some specific instant of the gait cycle, in both frontal and sagittal planes. However, their locomotion pattern is similar to the healthy controls.