REVISION OF CEMENTED HIP ARTHROPLASTY USING HAC COATED ENDOPROSTHESIS- A SEVEN TO FIFTEEN YEAR FOLLOW UP

Abstract

Purpose: We report the clinical and radiological outcome of revision of cemented hip arthroplasties using Hydroxyapatite ceramic (HAC) coated femoral and acetabular components.

Patients and Methods: 66-revision hip arthroplasties were performed in 64 patients with JRI Furlong HAC coated femoral and acetabular components. The patients were followed for a mean 10.6 years (7–15). The femoral component was revised in all hips and the acetabular cup was revised in 52 hips (79%). The clinical outcome was measured using Harris, Charnley and Oxford hip scores. Anterior thigh pain was quantified on a visual analogue scale (VAS). The quality of life was assessed using EuroQol EQ-5D. All pre op, immediate post op and last follow up radiographs were analysed for ace-tabular and femoral component loosening.

Results:The mean age was 78.2yrs (58–89yrs). The mean time to revision of the primary hip replacement was 96 months (24 to 161). 11 patients died due to causes unrelated to the index revision. At last follow up, the mean Harris and Oxford hip scores were 82 (59 – 100) and 24.4 (12-52) respectively. The Charnley score was 5.0 (3-6) for pain, 4.9 (3-6) for movement and 4.4 (3-6) for mobility. Acetabular bone grafting was performed in 26 (50%) hips. Migration > 4mm of the acetabular component was seen in 2 (4%) hips. Acetabular radiolucen-cies were present in 26 hips (55%). The mean linear polythene wear was 0.05mm/year. The mean stem subsidence was 1.6mm (0.30- 2.4mm). Radiolucencies were present around 21 (33%) stems. Stress shielding was seen in 40 of the 56 stems. Calcar resorption was seen in 11 stems (16%). Endosteal cavitation was seen around 2 stems. Ectopic calcification was seen in 12 (19%) hips. Of the 3 hips re- revised, 2 were for deep sepsis and 1 for recurrent dislocation. The mean EQ- 5D description scores and health thermometer scores were 0.69 (0.51-0.89) and 79 (54-95) respectively (p> 0.05 for both scores compared to average UK population scores). With failure defined as repeat revision because of aseptic loosening, the rate of survival at 12 years was 100% for the acetabular and femoral components. Overall survival at 12 years with removal or repeat revision of either component for any reason as the end point was 93% (95% CI ± 2.3).

Conclusion:The results of this study support the continued use of this prosthesis and document the durability of the HAC coated components. Our study had fewer cases of loosening of the components and had a better survival than bipolar implants or cemented acetabular components. As loosening can occur as a late phenomenon, a longer follow up is needed to determine the longevity and durability of the HAC coated prosthesis.