Intensity Matters in Joint Wear

It is not the amount of physical activity but the intensity of it that determines how long a cross-linked polyethylene joint implant will last. That is the conclusion of Rachel Senden, Ph.D., of the Department of Orthopaedic Surgery and Traumatology at Atrium Medical Center in Heerlen, Netherlands.

According to a report in Orthopaedics Today, Senden and colleagues compared two patient groups similar in age, weight and BMI (body mass index) who had Stryker ABG-II 28-mm cobalt chromium total hip arthroplasty systems. Between both groups, Hip Dysfunction & Osteoarthritis Outcome Score, Short Questionnaire to Assess Health-Enhancing Physical Activity score and physical activity were similar. However impact loading was greater in one group, resulting in a higher annual wear rate of 0.134 mm/year compared to 0.047 mm/year in the group with more intense activity.

“It seems like implant wear in patients behaves similar to wear in a car engine where fast driving and many short trips cause higher wear than slow, long distance driving, ” said Senden. “Based on this information, patients can be better instructed on what protects their joint from wear and what activities can be performed without affecting longevity. Given our results, patients can protect the longevity of their implants without being less active.” The investigators reported their results at the January Orthopaedic Research Society Annual Meeting in San Antonio, Texas.