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.

We have evaluated the in vivo migration patterns of 164 primary consecutive Charnley-Kerboull total hip replacements which were undertaken in 155 patients. The femoral preparation included removal of diaphyseal cancellous bone to obtain primary rotational stability of the stem before line-to-line cementing. We used the Ein Bild Roentgen Analyse femoral component method to assess the subsidence of the femoral component.

At a mean of 17.3 years (15.1 to 18.3) 73 patients were still alive and had not been revised, eight had been revised, 66 had died and eight had been lost to follow-up. The mean subsidence of the entire series was 0.63 mm (0.0 to 1.94). When using a 1.5 mm threshold, only four stems were considered to have subsided. Our study showed that, in most cases, a highly polished double-tapered stem cemented line-to-line does not subside at least up to 18 years after implantation.

We carried out a prospective randomised study designed to compare the penetration rate of acetabular polyethylene inserts of identical design but different levels of cross-linking at a minimum of four years follow-up. A total of 102 patients (102 hips) were randomised to receive either highly cross-linked Durasul, or contemporary Sulene polyethylene inserts at total hip replacement. A single blinded observer used the Martell system to assess penetration of the femoral head. At a mean follow-up of 4.9 years (4.2 to 6.1) the mean femoral head penetration rate was 0.025 mm/year (sd 0.128) in the Durasul group compared with 0.106 mm/year (sd 0.109) in the Sulene group (Mann-Whitney test, p = 0.0027). The mean volumetric penetration rate was 29.24 mm³/year (sd 44.08) in the Durasul group compared with 53.32 mm³/year (sd 48.68) in the Sulene group. The yearly volumetric penetration rate was 55% lower in the Durasul group (Mann-Whitney test, p = 0.0058). Longer term results are needed to investigate whether less osteolysis will occur.