An in vitro study of proximal femoral allograft strains in revision hip arthroplasty

✍ Scribed by M.D. Ries; M.A. Gomez; D.G. Eckhoff; D.A. Lewis; M.R. Brodie; J.D. Wiedel

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 641 KB
• Volume: 16
• Category: Article
• ISSN: 1350-4533
• DOI: 10.1016/1350-4533(94)90053-1

✦ Synopsis

Bone allografts are used frequently to replace bone stock subsequent to total hip arthroplasty. Revision of the failed hip replacement results in a complex structure of allograft bone, host bone and a metal fnnoral component. To evaluate the mechanics of the allograjt-implant-host bone structure at the time of surgery, a strain gauge study was undertahen with six fresh/frozen human fmora. Under defined loading conditions, cortical strain distributions were measured for five dtfferent cases: (1) normal bone, (2) bone with a frmoral implant, (3) bone with the fmtoral component and an osteotomy at the mid-stem level of the implant (i.e. to simulate the proximal allograft-host junction around the fnnoral stem), (4) bone with an osteotomy and an implant cemented into the 'allograft' (i.e. the proximal end of the fnnur), and (5) bone with an osteotomy and the implant cemented into both the proximal 'allografP and the distal host bone. The results showed that, prior to making the osteotomy, proximal femoral strains were &creased with the insertion of a fnnoral stem. These strains were further decreased when an osteotomy had been made. This strain distribution did not change when the stem was cemented into the proximal kllograft' bone, or cemented into the proximal 'allograft' and distal host bone. The decreases in strain for these test cases implied that the discontinuity between the bony segments caused an extended reduction in the tensile or compressive stresses transmitted through the cortices. Since strains in the

distal host bone also did not change for all the dyerent test cases, the decreased strains measured for the proximal 'allograft' suggested that the presence of the osteotomy causes the implant to undergo higher stresses for an applied load.