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. 2008 Mar;9(1):49-54.
doi: 10.1007/s10195-008-0105-4. Epub 2008 Mar 13.

Perspectives on metaphyseal conservative stems

F Falez  1 , F Casella, G Panegrossi, F Favetti, C Barresi
Affiliations

Perspectives on metaphyseal conservative stems

F Falez et al. J Orthop Traumatol. 2008 Mar.

Abstract

Total hip replacement is showing, during the last decades, a progressive evolution toward principles of reduced bone and soft tissue aggression. These principles have become the basis of a new philosophy, tissue sparing surgery. Regarding hip implants, new conservative components have been proposed and developed as an alternative to conventional stems. Technical and biomechanical characteristics of metaphyseal bone-stock-preserving stems are analyzed on the basis of the available literature and our personal experience. Mayo, Nanos and Metha stems represent, under certain aspects, a design evolution starting from shared concepts: reduced femoral violation, non-anatomic geometry, proximal calcar loading and lateral alignment. However, consistent differences are level of neck preservation, cross-sectional geometry and surface finishing. The Mayo component is the most time-tested component and, in our hands, it showed an excellent survivorship at the mid-term follow-up, with an extremely reduced incidence of aseptic loosening (partially reduced by the association with last generation acetabular couplings). For 160 implants followed for a mean of 4.7 years, survivorship was 97.5% with 4 failed implants: one fracture with unstable stem, 1 septic loosening and 2 aseptic mobilizations. DEXA analysis, performed on 15 cases, showed a good calcar loading and stimulation, but there was significant lateral load transfer to R3-R4 zones, giving to the distal part of the stem a function not simply limited to alignment. Metaphyseal conservative stems demonstrated a wide applicability with an essential surgical technique. Moreover, they offer the options of a "conservative revision" with a conventional primary component in case of failure and a "conservative revision" for failed resurfacing implants.

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Figures

Fig.1
Fig.1
Intact cortical ring in which cancellous bone can be impacted
Fig.2
Fig.2
Mayo reduced diaphyseal segment functional just to varus-valgus alignment along lateral femoral cortex
Fig.3a
Fig.3a
Nanos stem. b Metha stem
Fig.4
Fig.4
More proximal filling of Nanos stem (related to its rounded cross-section)
Fig.5
Fig.5
Surface finishing of Mayo stem: grit blasting with mesh pads
Fig.6
Fig.6
Prevalence of distal stress transfer along the stem to the lateral femoral cortex
Fig.7
Fig.7
Revision of a failed Mayo stem with a primary implant
Fig.8
Fig.8
Revision of a failed resurfacing implant with a Mayo stem
Fig.9
Fig.9
Revision of a failed CFP stem with a Nanos stem
See this image and copyright information in PMC

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