Configuration of anchorage holes affects fixation of the acetabular component in cemented total hip replacement—a finite element study

Abstract

Our survey of current practice among UK orthopaedic surgeons shows wide variations in fixation techniques. The aim of this study is to investigate the effect of drilling different configurations of anchorage holes in the acetabulum on implant stability. To avoid variables that could incur during in-vitro testing, we used commercially-available COSMOS finite element analysis package to investigate the stress distributions, deformations, and strains on the cement mantle when drilling three large anchorage holes and six smaller ones, with straight and rounded cement pegs. The results, which are in line with our in-vitro studies on simulated reconstructed acetabulae, indicate better stability of the acetabular component when three larger holes than six smaller holes are drilled and when the necks of the anchorage holes are rounded. The longevity of total hip replacements could be improved by drilling three large anchorage holes, rather than many smaller ones, as initially proposed by Charnley.

Total Hip Replacement: Tensile Stress in Bone Cement is influenced by Cement Mantle Thickness, Acetabular Size, Bone Quality, and Body Mass Index

“…Previous computational and in vitro studies show that stress distributions and torsional strengths of the reconstructed hip joint are influenced by the geometry and configurations of the cement pegs [14,[22][23][24]. However, our survey of current practice among orthopaedic surgeons (454 respondents) shows wide variations in surgical fixation techniques [25].…”

“…We have therefore verified our FE model by conducting a parallel in vitro study on the Third Generation synthetic Sawbones (Sawbones Europe AB, Malmö, Sweden) [15]. The aim of that study was to investigate the effect of cement mantle thickness on the stability of cemented reconstructed acetabulum.…”

“…The acetabulum was virtually reamed into a hemispherical bed, which is reported to result in a uniform cement mantle, smooth stress distribution and, consequently, a stable reconstruction [27,28]. Three 8-mm deep and 8-mm diameter anchorage holes were then modelled perpendicular to the bed of the acetabulum, one in each of the iliac, pubic and ischial regions, to simulate a good cemented surgical fixation [15].…”

“…Cement pegs, created during a THR to provide implant stability and to improve the torsional strength of the reconstructed acetabulum, can be subjected to high stress levels, especially near the neck [14,15], and where failure often occurs in vivo. We postulate that implant fixation can be improved if the cement mantle is subjected to a smooth stress distribution as opposed to high peak stress [14].…”

Stand der zementierten Hüftendoprothetik in Deutschland 2010

“…Andersson et al [27] stellten in den 70er-Jahren fest, dass Bohrlöcher im Pfannendach keinen Stabilitätsgewinn darstellten. Aktuelle Studien zeigen allerdings, dass wenige große Bohrlöcher (3 × 12 mm) das Knochen-Zement-Interface verstär-ken und so höhere Scherbelastungen ermöglichen [28] allerdings 2009 von insgesamt 15 646 Primärimplantationen immerhin noch ca. 67 % komplett zementiert und nur 17 % komplett zementfrei implantiert wurden.…”