Abstract
Introduction
In order to reduce polyethylene wear and incidence of osteolysis, and improve the long-term durability of total hip arthroplasty (THA), highly cross-linked polyethylene was introduced for clinical use in substitution for conventional polyethylene. We performed 35 cementless THAs between December 2000 and February 2002, and cross-linked polyethylene was used in these surgeries. The purpose of this study is to research linear wear rate of these hips, and to find the risk factor for high wear rate.
Patients and Methods
32 hips (26 patients) among the 35 could be evaluated at more than 10 years postoperatively. One hip required reoperations due to infection at 8 years postoperatively, and two were lost to followup in less than 10 years. There were 2 males and 24 females, and the observation period was 11.4 years in average (range 10?13 years). The age at the time of operation was 49.4 years in average (range 24?67 years), and body mass index was 22.4 in average (15?34). We used AHFIX total hip prostheses (KYOCERA Medical Corporation) for both acetabular and femoral replacement, and 22 mm Zirconia head was used in all cases. The median cup diameter was 46 mm (range 42?50). Osteolysis and loosening of the implant was evaluated on the anteroposterior radiograph of the hip. Using software for wear measurement (Hip Analysis Suite), linear wear rate and cup inclination angle were measured. Correlation between linear wear rate and age, BMI, cup inclination angle, and cup diameter was investigated using correlation coefficient.
Results
Osteolysis and loosening were not found in any cases on the final radiograph. Cup inclination angle was 44.7±4.6 degree, and linear wear rate was 0.034±0.019 mm/y in average. No statistical correlation was found between linear wear rate and age, BMI, cup inclination angle, and cup diameter.
Discussion
Long-term clinical performance of cross-linked polyethylene is rarely reported, although it is considered to have excellent wear resistance, and reduces the risk of osteolysis and loosening. Linear wear rate in this series was relatively low, and osteolysis and loosening were not observed. It was demonstrated that cross-linked polyethylene had excellent wear resistance when used in combination with 22 mm zirconia head, and observed for more than 10 years.
