Intraoperative Dual-Cantilever Probe for Rapid Measurement of Cancellous Bone Compressive Strength Within the Vertebral Body

Abstract

Abstract. Dual X-ray absorptiometry (DEXA) scans are the current standard in assessing bone mineral density (BMD) and are used to identify patients who may need screw augmentation during spinal fusion. DEXA scans are not always available and tend to overestimate BMD. This paper describes the development of a dual-cantilever mechanical probe and tested in polyurethane foam blocks with varying compressive strengths. The probe was modeled after a 5.5 mm tap and foam block holes were prepared replicating intra-operative conditions. Calibration curves were acquired for each probe using six foam blocks (1.5–12.9 MPa). Verification tests were performed in a different set of four foam blocks (2.05–9.65 MPa). Four probes were machined and tested for repeatability. Three users separately acquired measurements of foam blocks to test for reliability. The root-mean-square error of all four probes measuring the 2.05 MPa, 3.65 MPa, 5.80 MPa, and 9.65 MPa samples were 0.89 MPa, 0.32 MPa, 1.41 MPa, and 1.71 MPa, respectively. There was not a significant difference between different probes or different users. The dual-cantilever probe provided measurements within the clinically relevant range of compressive strengths for vertebral trabecular bone. A targeted and reliable bone strength measurement technique could reduce the occurrence and revision surgeries and improve patient outcomes.