LONG-TERM MIGRATION USING EBRAFCA OF STEMS CEMENTED LINE-TO-LINE ACCORDING TO THE ‘FRENCH PARADOX’ PRINCIPLES

Introduction: The aim of this study was to evaluate the in vivo migration patterns using EBRA-FCA of a consecutive series of polished femoral components cemented line-toline. Materials and Methods: Between January 1988 and December 1989, 164 primary total hip arthroplasties were performed in 155 patients. The mean age at the time of the index arthroplasty was 63.8 ± 11.6 years. A single design prosthesis was used combining an all-polyethylene socket and a 22.2 mm femoral head. The mono-block double tapered (5.2°) femoral component made of 316-L stainless steel had a highly polished surface (Ra = 0.04 μm) and a quadrangular section(Kerboull ® MKIII, Stryker). The femoral preparation included removal of diaphyseal cancellous bone to obtain primary rotational stability of the stem prior to the line-to-line cementation. For each patients, all available AP radiographs of the pelvis were digitized (Vidar Sierra Plus, Vidar System Corporation, Herdon, Virginia) and linked to an IMB-compatible computer. The EBRAFCA software is a validated method designed to assess migration of a femoral component through comparable pairs of radiographs. Results: At the minimum 15-year follow-up, 73 patients (77 hips) were still alive and had not been revised at a mean of 17.3 ± 0.8 years (15–18 years), 8 patients (8 hips) had been revised for high polyethylene wear associated with periacetabular osteolysis, 66 patients (69 hips) were deceased, and 8 patients (10 hips) were lost to follow-up. Among the 8 revision procedures, the femoral component was loose in 3 hips. A total of 1689 radiographs (mean 10.3 per hip) were digitized. At the last follow-up, the mean subsidence of the entire series was 0.63 ± 0.49 mm (median of 0.61 mm; range 0 to 1.94 mm). When using a 1.5 mm threshold (accuracy of the EBRAFCA method) for subsidence, 4 of the 142 stems with adequate EBRA-FCA data were considered to have migrated. Using a threshold of 2 mm for subsidence, none of the 142 stems were considered to have migrated. The patterns of migration were calculated every 2 years giving 9 intervals. The evolution of mean subsidence during the whole follow-up period remained below 1.5 mm. Discussion: Mean subsidence of this quadrangular highly polished femoral component remained below the accuracy of the method (± 1.5 mm) throughout the entire follow-up period. Of the 142 hips analyzed, only four (2.8%) had subsided of more than 1.5 mm and none more than 2 mm. This study demonstrates that contrary to other cemented femoral components that have provided excellent survival in the long term frequently associated with stem subsidence, a highly polished cemented double tapered femoral component with a quadrangular cross-section cemented line to line does not subside up to 18-year follow-up.