Clinical Review of the Zweymuller Femoral Stem

Abstract

This review summarizes published literature from a range of reputable sources regarding hip prostheses (stems) utilized currently in cementless Total Hip Arthroplasty. The critical review of published clinical studies shows Zweymuller style (Alloclassic and SL-Plus) stems in all critical characteristics.Since the introduction of cementless total hip arthroplasty in the 1970s, a range of design philosophies for femoral and acetabular components have demonstrated variable clinical success 1,3 .Recently cementless components have been yielding clinical results on par and in some cases even surpassing their cemented predecessors 2,4,6 . As a result, cementless THA is gaining in popularity 1,7 . The short-term results of four of the best cementless femoral components recorded in the Norwegian Arthroplasty Register as described by Havelin et al, included the Corail, lMT, Profile and Zweymuller stems with revision for loosening <1% at 4.5 years which was comparable to cemented counterparts.The Zweymüller stem was introduced to the global market in 1973 8 . Since its introduction the Zweymüller stem has been implanted in over 700,000 patients 9 and has undergone minor design updates. The first generation Hochgezogen was a straight stem with a rectangular cross section tapering in the sagittal plane. The stem was forged from titanium alloy (Ti-6Al-4V) with a grit-blasted surface finish. In 1986 the second generation Alloclassic-SL (StepLess) was introduced 10 . The Alloclassic evolved from the Hochgezogen to taper in both the sagittal and frontal plane and to replace the Vanadium with Niobium in the Titanium alloy due to cytotoxicity concerns 11 . The SL alludes to the way the stem sizes increase steplessly and proportionally to allow downsizing without sacrificing stability 9 . The latest generation of the Zweymüller stem, the SL-PLUS has been selected as the predicate for the Signature Pegasus stem. The SL-PLUS differs slightly from the Alloclassic geometrically, with slight modifications to the neck, proximal surface and cross section 3,12 .The review presents the findings of a literature review conducted to evaluate the clinical performance and survivorship outcomes of the later generations of the Zweymüller stems.