DensiProbe Spine: First Clinical Experience with Intraoperative Measurement of Bone Quality

Introduction Poor bone quality due to osteoporosis is an increasing problem in dorsal transpedicular instrumentation of the aging spine. As the number of patients and indications are increasing, complications as screw loosening, cut-out, migration and loss of reduction are more and more observed [1,2]. These complications can be avoided to a large degree by choosing appropriate implant design and length of the instrumentation as well as by augmentation of the screw anchorage using bone cement. However, these techniques are often costly and time consuming and bear, in the case of cementation, the risk of cement leakage with possible pulmonary embolisms or neurological complications. Furthermore in most cases no information of the quality of the bone is available at surgery. Therefore, there is a need for a diagnostic device that can intraoperatively support the surgeon’s decision on the appropriate treatment. The measurement device called DensiProbe Spine consists of a modified pedicle probe and an electronic system to measure the peak torque to break-away of trabecular bone in the vertebral body at the site of the pedicle screw tip. Previous reported in vitro validation of the DensiProbe Spine tool was performed on ten human cadaver lumbar vertebrae. A highly significant (r = 0.90; p = 0.002) correlation between peak torque measured by DensiProbe Spine and regional bone mineral density (BMD) measured by micro-CT was found. A significant result was also found when correlating bone strength using DensiProbe with maximum loads to cut-out of the pedicle screw in a biomechanical test setup (r = 0.959, p = 0.003) [3]. The objective of this pilot study with 30 patients is to investigate safety, handling and feasibility of the newly developed DensiProbe Spine measurement device under clinical conditions.