The hemispherical porous acetabular component fixed by press-fit technique and additional screws

Documentation of hip prostheses used in NorwayA critical review of the literature from 1996–2000

We have conducted a systematic review of the scientific literature concerning outcome and clinical effectiveness of prostheses used for primary total hip replacement (THR) in Norway. The study is based on two Health Technology Assessment reports from the UK (Faulkner et al. 1998, Fitzpatrick et al. 1998), reviewing the literature from 1980 to 1995. Using a similar search strategy, we have evaluated the literature from 1996 through 2000. We included 129 scientific and medical publications which were assessed according to a specific appraisal protocol. The majority (72%) were observational studies, whereas only 9% were randomized studies. We could not retrieve any peer-reviewed documentation for one third of the implants. The Charnley prosthesis had by far the best and most comprehensive evidence base with better than 90% implant survival after about 10 years. Survival of the Charnley prosthesis declines by about 10% during each of the two following decades. Except for the Charnley and Lubinus IP, no other prosthesis on the market in Norway has given long-term results (> 15 years). 5 other cemented implants have given comparable results at about 10 years of follow-up. Some uncemented stems have shown promising medium-term outcome, but no combination of uncemented cup and stem fulfilled the benchmark criterion of > or = 90% implant survival at 10 years, which we propose as a minimum requirement for unrestricted clinical use for prostheses used in primary THR. New or undocumented implants should be introduced through a four-step model including preclinical testing, small series evaluated by radiosterometry, randomized clinical trial involving comparison with a well-documented prosthesis, and finally, surveillance of clinical use through registers.

Long-term results with cementless Fitek (or Fitmore) cups

Fitek cementless cups have been adopted in our department in 1989. The first 100 consecutive Fitek implants were analyzed clinically (Harris hip score) and radiographically (anteroposterior and lateral x-rays) with a mean follow-up of 9.7 years. We did not have any case of cup loosening or any other problem requiring cup revision. In this series, we had 86 excellent, 10 good, 2 fair, and 2 poor results. The 2 poor results were because of 2 cases of aseptic loosening of the stem (1 cemented and 1 cementless). The x-rays showed an average angle of cup inclination of 36.5 degrees (range 16 degrees -54 degrees ) after surgery and no variations at the last follow-up. Bidimensional linear wear of the acetabular component showed 6 cases of measurable wear with an average wear rate per year of 0.265 mm. The overall wear rate per year was 0.02 mm. At the time of the last follow-up examination, we had 3 femoral osteolysis and no case of acetabular osteolysis. In our series, we observed "lack of contact" zones above the polar depression in 71 cases immediately after surgery. The average thickness of these lines was 1 (range 0.5-3.5) mm. Of these, at the last follow-up, 61 cases (86%) showed a complete "filling" of the "lack of contact," whereas in 10 (24%), the "filling" was incomplete (4 cases still showing a radiolucent line [<or=0.5 mm] in zone II). In the first group with "complete filling," we found 23 (37%) cases with bone ingrowth and no migration of the cup, whereas 38 (63%) cases showed bone ingrowth with evidence of cup migration. The Mann-Whitney nonparametric U test and the Kruskal-Wallis test showed that the survival rate of the 100 analyzed cups, after a follow-up time of 9.7 years, was 100% (end point: revision for any cause). Fitek cup showed good clinicoradiographic results.

A 10-year minimum follow-up of hydroxyapatite-coated threaded cups: clinical, radiographic and survivorship analyses with comparison to the literature

We evaluated the clinical, radiographic, and survivorship outcomes in a series of 418 threaded hydroxyapatite-coated acetabular cups (Arc2f; Osteonics, Allendale, NJ) implanted in a consecutive series of 384 patients undergoing primary total hip arthroplasty. In all cases, the cup was screwed into the prepared acetabulum. Bone screws were used to provide secondary fixation. At a minimum 10-year follow-up, 304 cups were available for analysis. The cumulative survivorship (mechanical failure as endpoint) at that time was 99.43% +/- 0.0104. Two hundred seventy-six hips were available for full clinical and radiographic review at or after the tenth anniversary. No unstable implants were noted; all implant fixation interfaces were classified as "stable bone ingrown," and the cup migration rate was zero. Based on the survivorship achieved with this implant, our results compare favorably with survivorship reported for the best cemented and cementless acetabular implant designs.