Does the bone mineral density measured on a preoperative CT scan before total hip arthroplasty reflect the bone's mechanical properties?

Abstract

IntroductionNo method exists to quantify the bone quality and factors that will ensure osteointegration of total hip arthroplasty (THA) implants. A preoperative CT scan can be used to evaluate the bone mineral density (BMD) when planning a THA procedure. The aim of this study was to validate BMD measurement as a marker of bone quality based on a preoperative CT scan. HypothesisBMD reflects the bone's mechanical properties for the purposes of preoperative THA planning. MethodsPatients who underwent primary THA for hip osteoarthritis or dysplasia with cementless implants and 3D preoperative plan were enrolled prospectively. The cortical BMD was calculated on CT scans used in the preoperative planning process. During the surgical procedure, the femoral head and neck were collected. These bone samples were subsequently scanned with a calibrated micro-CT scanner. The BMD was derived from the micro-CT scan and used as input for a finite element model to determine the bone's mechanical properties. Correlations between BMD, apparent moduli of elasticity and porosity were calculated. ResultsThe values of cortical BMD measured on the micro-CT and CT scan were significantly correlated (cc=0.52). The mean angular cortical BMD measured with the micro-CT scan was 1472.33mg/cm3 (SD: 357.53mg/cm3, 980.64–2830.6mg/cm3). There was no significant correlation between cortical BMD and the various apparent moduli of elasticity, except for Eyy and Gzy. Cortical BMD and porosity were inversely correlated with a Spearman coefficient of −0.41 (CI95: [−0.71; −0.02], p=0.03). There was also an inverse correlation between the apparent moduli of elasticity (independent of their orientation) and porosity (p<0.01). DiscussionBMD provides information about porosity, which is a major factor when evaluating the bone's mechanical properties before THA. Level of evidenceIV.