[Straight femoral taper in cementless primary total hip replacement in less than 65 year-old patients: multicenter study of 115 consecutive implantations at mean 8,2 year follow-up].

PURPOSE OF THE STUDY: The Swedish Arthroplasty Registry experience with cemented primary total hip arthroplasty (THA) has pointed out age below 65 and high activity level as 2 major factors impairing THA long-term outcome. The aim of this study was to provide intermediate results of cementless femoral replacement in primary THA with use of the Alloclassic-SL grit-blasted titanium stem in "high risk" groups of patients.

MATERIAL AND METHODS: From June, 1988 to June, 1992, 127 cementless primary THA's were consecutively performed in<65 year old patients in 2 institutions. Acetabular components were all cementless (threaded cup in 74%) and bearing surfaces were all alumina-ceramic 28mm heads on polyethylene (PE). Five patients (6 hips) died and 6 other hips were lost to follow-up before the 5-year minimum follow-up. Thus, 115 hips in 106 patients could be fully reviewed after a 8.2 year average follow-up period (range, 5 to 12 years). Mean age at surgery of the 62 male and 44 female patients was 52 years (range, 27 to 65 years).

RESULTS: Of the index group (127 hips), intra-operative fracture of the greater trochanter and early dislocation were noted in 4.7% and 3.2% of hips, respectively. Of the study group (115 hips), clinical results according to the Merle d'Aubigné and Charnley rating system were graded excellent and good in 94% of hips and fair in 6% (7 hips), with no poor result. Radiologically, early subsidence of more than 2mm could be detected in 8 hips (7%). Calcar atrophy and spot welds were noted in 81% and 89% of hips, respectively. Proximal reactive and lucent lines and mild proximal stress shielding were observed in 10.5% and 4.3% of hips, respectively. Ten-year survivorship with stem revision for any reason as the end point was 99.2% (92.4-99.9) (1 stem exchanged and reoriented for immediate dislocation). One revision is pending for extensive femoral osteolysis due to polyethylene (PE) wear. There was no stem fracture and no ceramic head breakage thus far. Overall PE-wear rate ranging 1-2 mm was detected in 13 hips (9.6%) and femoral osteolysis in 4 hips (3.5%).

DISCUSSION: Mid-term results of this cementless straight taper at 10 year are at least equal to those of well performing cemented components, even in "high risk" groups of patients. Conversely, 28mm alumina-ceramic heads can reduce but not prevent the occurrence of PE-wear in such a healthy and active population.

CONCLUSION: Press-fitting but not filling the femoral canal with rough titanium straight tapers like the Alloclassic-SL femoral component represent a promising alternative to modern femoral cementing technique in primary THA. Improvement is expected through the use of more wear resistant bearing surfaces.