Five-year follow-up of a hydroxyapatite coated stem

Purpose of the study.-We studied a cementless anatomic stem combination with a cementless press-fit cup. The purpose of this work was to assess prospectively in a homogeneous consecutive series of patients, the clinical and radiological outcome of this prosthesis at five years follow-up. Material and methods.-The series included 176 hips with a total hip arthroplasty implanted between September 1997 and December 1998 by the same surgeon through an antero-lateral approach (Watson-Jones). We retained for study first intention implantations for primary or secondary joint degeneration. Fractures and revisions were excluded from the analysis. At last follow-up the survival was 93.2%. Patients were revised clinically (satisfaction Harris score). An independent surgeon unaware of the clinical results performed the radiological analysis (Engh and Ara score, Brooker classification). The Kaplan-Meier method was used for the survival curve expressed with 95% confidence interval and considering revision for all causes as failure. Results.-The five-year survival of the prosthesis was 98.8%. Clinically, the Harris score varied significantly (p < 0.0001) from 32.9 +/- 1.2 preoperativety to 93.1 +/- 0.8 at last follow-up. Among the score items, pain exhibited the greatest improvement since at five years only, 10.2% of patients complained of mild pain. Thigh pain, often associated with cementless stems, was very low, 1.3%. Radiologically, the femoral implant was very stable with excellent bone remodelling as illustrated by the high Engh and Ara scores, 20.7 +/- 0.5 and 5 +/- 0.2 respectively. Polyethylene wear, 0.075 mm/year, was below the usually observed levels. We noted a high rate of heterotopic ossifications, 65.1%, most Brooker 1. Discussion.-The SPS stem has shown good results at five years, both clinically and radiographically. The objectives of a stable fixation over time and harmonious remodelling appear to be achieved. These promising results should be reexamined in a series with a longer follow-up. (C) 2008 Publie par Elsevier Masson SAS.