In Vitro DEXA-BMD Measurements Affected by Type of Soft Tissue Surrogate

Dual-energy x-ray absorptiometry (DEXA), the technique most widely used to assess skeletal integrity, is routinely performed on cadaveric tissue to ensure that the bone mineral densities (BMD) of the test specimens are representative of the target patient population for a particular orthopaedic device [1]. It is well established that DEXA-BMD measurements are sensitive to the amount of fat and other soft tissue present in the region of interest [2]. Recognizing that the removal of perivertebral soft tissue may affect DEXA-BMD readings of in vitro cadaveric specimens, biomechanics researchers have used various “torso surrogates” to simulate the removed tissue and x-ray attenuation. These include: 1) submersion of spinal sections in a physiological saline bath, 2) surrounding spinal sections with gel-filled packs, and 3) packing rice-filled bags around spinal sections and within the internal cavity of eviscerated torsos [3, 4]. It is unknown whether these inter-study differences in technique affect in vitro DEXA measurements. Given the prevalence of soft tissue artifacts in vivo, the goal of this study is to examine the sensitivity of in vitro DEXA-BMD to the quantity and composition of soft tissue surrogates. This work is the first step in a broader study to develop a set of best practices for DEXA scanning of cadaveric tissue.