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BONE PRESERVATION WITH A CONSERVATIVE METAPHYSEAL LOADING IMPLANT

7th Congress of the European Federation of National Associations of Orthopaedics and Traumatology, Lisbon - 4-7 June, 2005



Abstract

Introduction Significant cortical bone mass has been demonstrated at the proximo-lateral flare of the femur (Fetto et al). Experiments have shown that if a femoral stem has a medial and lateral flare proximally, the loads are transferred to the proximal femur and stress protection in this area is avoided. Furthermore, the results suggested that a stem below the lesser trochanter was unnecessary (Walker et al).

Methodology This paper reports on two cohorts of ten patients that had either a short stemmed fully coated implant (Group I) or an unstemmed metaphyseal implant on which all but the polished tip was coated (Group II). All implants were customised based on pre-operative CT data. All hips had serial post-operative AP and lateral radiographs and bone densitometry was assessed with DEXA scanning.

Results The most recent post-operative radiographs of all patients in Group I revealed buttressing in zone IV with trabeculae streaming from the cortices onto the tip of the stem. Qualitatively there appeared to be osteope-nia in Gruen zones I and VII. The x-rays of the Group II patients revealed good condensation of bone along the textured surface in zone I and VII with preservation of bone density in these regions. These findings were confirmed by the DEXA results which showed a reduction of the BMD in zones I and VII in Group I, while Group II revealed preservation of the BMD in these zones.

Conclusion A conservative prosthesis without a stem which effectively loads both medial and lateral proximal femoral flares not only removes less bone at the index operation but preserves proximal bone stock in the longer term.

Theses abstracts were prepared by Professor Roger Lemaire. Correspondence should be addressed to EFORT Central Office, Freihofstrasse 22, CH-8700 Küsnacht, Switzerland.

Fetto JF, Bettinger P, Austin K. Reexamination of hip biomechanics during unilateral stance. Am J Orthop1995; Aug: 605–12 Google Scholar

Walker PS, Culligan J, Hua J, Muirhead-Allwood SK, Bentley G. The effect of a lateral flare feature on unce-mented hip stems. Hip International1999; 9: 71–80 Google Scholar