A randomized study on migration of the Spectron EF and the Charnley flanged 40 cemented femoral components using radiostereometric analysis at 2 years

Abstract

Background and purpose We performed a randomized study to determine the migration patterns of the Spectron EF femoral stem and to compare them with those of the Charnley stem, which is regarded by many as the gold standard for comparison of implants due to its extensive documentation.

Patients and methods 150 patients with a mean age of 70 years were randomized, single-blinded, to receive either a cemented Charnley flanged 40 monoblock, stainless steel, vaquasheen surface femoral stem with a 22.2-mm head (n = 30) or a cemented Spectron EF modular, matte, straight, collared, cobalt-chrome femoral stem with a 28-mm femoral head and a roughened proximal third of the stem (n = 120). The patients were followed with repeated radiostereometric analysis for 2 years to assess migration.

Results At 2 years, stem retroversion was 2.3° and 0.7° (p < 0.001) and posterior translation was 0.44 mm and 0.17 mm (p = 0.002) for the Charnley group (n = 26) and the Spectron EF group (n = 74), respectively. Subsidence was 0.26 mm for the Charnley and 0.20 mm for the Spectron EF (p = 0.5).

Interpretation The Spectron EF femoral stem was more stable than the Charnley flanged 40 stem in our study when evaluated at 2 years. In a report from the Norwegian arthroplasty register, the Spectron EF stem had a higher revision rate due to aseptic loosening beyond 5 years than the Charnley. Initial stability is not invariably related to good long-term results. Our results emphasize the importance of prospective long-term follow-up of prosthetic implants in clinical trials and national registries and a stepwise introduction of implants.

TK: planning, conduction, and first writer. GH: planning, conduction, and writing. AA, RSA: analysis and review of the writing process. KI: planning, conduction, and writing. MB: conduction and review of the writing process. LIH: planning, conduction, and writing. TS: conduction of the RSA examinations and review of the writing process. KH: RSA analysis and review of the writing process. BE: planning of statistics and writing of parts dealing with statistics. OF: conception, planning, and conduction of the study, and writing.

The study was jointly financed by OrtoMedic AS, Smith and Nephew Norway AS, and the Regional Health Board of Western Norway. None of the funding sources played any role in the preparation, performance, or analysis of the results of this study. One author (TK) has received PhD grants from the Regional Health Board of Western Norway.

No competing interests declared.