Total Hip Arthroplasty Using Metal Head on a Highly Cross-linked Polyethylene Liner

Abstract

Purpose: This retrospective study was performed to evaluate the clinical results and measure polyethylene liner wear in total hip arthroplasty (THA) with highly cross-linked polyethylene.

Materials and methods: Except for patients who had died or were unable to have follow-up at least 2 years, 60 of 78 hips that underwent THA were included this study. The mean age was 64.5 years (range, 25-81 years) and the mean body mass index (BMI) was 23.0 kg/m(2) (18.1-32.3 kg/m(2)). Diagnosis at the time of the operation was osteonecrois of the femoral head in 28 hips, primary osteoarthritis in 14, hip fracture in 13, and other diseases in 5. The mean follow-up period was 3.8 years (2.1-7.1 years). Harris hip score (HHS) was reviewed before THA and at the last follow-up. On the anteroposterior pelvic radiographs, acetabular cup inclination and ante-version were also measured. The annual linear wear rate was measured using Livermore's method on the radiographs.

Results: The mean HHS was 60.1 (28-94) before operation and 90.4 (47-100) at the last follow-up. In the immediate post-operation, the average inclination and anteversion angles of the acetabular cups were 46.3° (standard deviation, ±6.7°) and, 21.4°(±10.1°) respectively. The mean of the annual linear polyethylene wear was 0.079 mm/year (0.001-0.291 mm/year). Age, gender and BMI were not statistically related to linear polyethylene wear but the period of follow-up and the acetabular cup's inclination showed significant negative and positive correlation respectively.

Conclusion: The wear rate of a highly cross-linked polyethylene was shown to correlate negatively with duration of follow-up. However, our study was based on a short-term follow-up, so a long-term follow-up study is necessary in the future.

Keywords: Highly cross-linked polyethylene; Linear wear rate; Total hip arthroplasty.

Fig. 1. A scatter plots show linear correlation the annual wear rate of polyethylene versus the period of follow-up (A) and inclination angles of the acetabular cups (B). The y-axis is the annual wear rate of polyethylene (mm/year), x-axis are the period of follow-up (years) and inclination angles of the acetabular cups (°). The dash lines show the regression lines of linear correlation the annual wear rate of polyethylene versus the period of follow-up and inclination angles of the acetabular cups.

Fig. 2. Each divided into groups of the period of follow-up (A) and inclination angles of the acetabular cups (B), a flow plots show the means of annual wear rate of polyethylene and the total wear during follow up. The y-axis is the means of annual wear rate of polyethylene (mm/year), x-axis are different groups by the period of follow-up (years) and inclination angles of the acetabular cups (°). The dash lines represent the regression lines of linear correlation.