Activity level in young patients with primary total hip arthroplasty: a 5-year minimum follow-up.

Increased activity level after total hip arthroplasty (THA) is considered a risk factor for early prosthetic failure in young patients. Forty-one primary total hip arthroplasties in 34 patients were evaluated. Walking activity was measured using a pedometer to record gait cycles. Patients completed a University of California, Los Angeles (UCLA) activity questionnaire. Linear wear rates were measured. Mean ages at surgery and final follow-up were 42 and 50.3 years, respectively (mean gait cycles per year, 1.2 million; mean UCLA score, 6; mean linear wear, 0.16 mm/y). Increased body mass index and age correlated with decreased gait cycles per year. Patients with systemic disease were less active than patients with localized hip conditions. Femoral head diameter was a predictor of linear wear. The average gait cycles per year and wear rate for this population do not appear accelerated relative to average values reported in older populations.