Serial measurement of polyethylene wear of well-fixed cementless metal-backed acetabular component in total hip arthroplasty: An over 10 year follow-up study

Serial radiographic measurements of polyethylene wear were performed in 38 hips (33 patients) with primary cementless total hip arthroplasty (THA). Th e average follow-up period was 131.8 months. All prostheses were assessed a s radiographically stable at the latest follow-up. A two-dimensional method was used to calculate the relative migration of the femoral head center to the cup center. The average total linear wear and wear rate were 1.22 mm a nd 0.11 mm/year, respectively. The degree of wear in the first 2 postoperat ive years accounted for nearly 40% of the total wear at the end of the stud y (average follow up: 131.8 +/- 10.0 months, +/-SD). The migration of the f emoral head at an average period of 3.4 months after operation accounted fo r 56% of the amount of wear in the first 2 years. Wear rate decreased gradu ally with time and stabilized after the fourth year. However, in 2 patients , a progressive increase in the wear rate was associated with severe osteol ysis and failure of THA. Both creep and wear contributed to the femoral pen etration into the polyethylene liner. The influence of creep cannot be rule d out, especially in the early period after operation. Polyethylene wear is a multifactorial process, and the study of individual wear patterns might be useful in identifying patients who are at risk of late failure of THA.