Predictive value of Singh index and bone mineral density measured by quantitative computed tomography in determining the local cancellous bone quality of the proximal femur

Objective. The purpose of this study was to assess the predictive value of the Singh index as well as quantitative computed tomography for the in vitr o local mechanical competence of the cancellous bone of the proximal femur. Design. An experimental study examining the relation between mechanical pro perties and bone mineral density of the femoral neck determined in vitro an d the clinical estimated Singh index on X-rays. Background. Evaluation of the predictive value of the Singh index, an inexp ensive and simple technique for the mechanical properties of the cancellous bone of the proximal femur. Methods. The bone quality of the proximal femur of 34 patients undergoing t otal hip replacement was estimated by roentgenography using the Singh index . Bone mineral density was quantified by quantitative computed tomography u sing cylindrical cancellous bone biopsies harvested during the total hip re placement procedure by a new biopsy method. The mechanical properties of th e bone specimens (Young-s modulus, strength and maximum energy absorption E -max) were measured by mechanical testing of the bone biopsies. Results. A strong correlation of the Singh index versus material properties of cancellous bone was noted (r = 0.66 for Young's modulus, r = 0.73 for s trength and r = 0.69 For E-max, P < 0.0001). The correlations of bone miner al density measured by quantitative computed tomography versus Young's modu lus, strength and energy absorption E-max were significant. Strength was pr edicted best (r = 0.82; P < 0.0001), followed by E-max (r = 0.79: P < 0.000 1) and Young's Modulus (r = 0.73; P < 0.0001). Conclusions. We conclude, that assessment of bone mineral density by quanti tative computed tomography is a reliable and precise method for the estimat ion of cancellous bone material properties. The Singh index provides a roug h estimate for the mechanical competence of the proximal femur. It is inexp ensive, simply to assess and can in some cases replace the measurement of b one mineral density, notably in cases of marked decrease in bone density.