title: DensiProbe Spine: an intraoperative measurement of bone quality in spinal instrumentation. A clinical feasibility study.
abstract: BACKGROUND
  A new device, DensiProbe, has been developed to provide surgeons with intraoperative information about bone strength by measuring the peak breakaway torque. In cases of low bone quality, the treatment can be adapted to the patient's condition, for example, by improving screw-anchorage with augmentation techniques.
  
  
  OBJECTIVE
  The objective of this study was to investigate the feasibility of DensiProbe Spine in patients undergoing transpedicular fixation.
  
  
  METHODS
  Prospective feasibility study on consecutive patients.
  
  
  METHODS
  Fourteen women and 16 men were included in this study.
  
  
  METHODS
  Local and general bone quality.
  
  
  METHODS
  These consecutive patients scheduled for transpedicular fixation were evaluated for bone mineral density (BMD), which was measured globally by dual-energy X-ray absorptiometry and locally via biopsies using quantitative microcomputed tomography. The breakaway torque force within the vertebral body was assessed intraoperatively via the transpedicular approach with the DensiProbe Spine. The results were correlated with the areal BMD at the lumbar spine and the local volumetric BMD (vBMD) and a subjective impression of bone strength. The feasibility of the method was evaluated, and the clinical and radiological performance was evaluated over a 1-year follow-up. This study was funded by an AO Spine research grant; DensiProbe was developed at the AO Research Institute Davos, Switzerland; the AO Foundation is owner of the intellectual property rights.
  
  
  RESULTS
  In 30 patients, 69 vertebral levels were examined. The breakaway torque consistently correlated with an experienced surgeon's quantified impression of resistance as well as with vBMD of the same vertebra. Beyond a marginal prolongation of surgery time, no adverse events related to the usage of the device were observed.
  
  
  CONCLUSIONS
  The intraoperative transpedicular measurement of the peak breakaway torque was technically feasible, safe, and reliably predictive of local vBMD during dorsal spinal instrumentations in a clinical setting. Larger studies are needed to define specific thresholds that indicate a need for the augmentation or instrumentation of additional levels.
authors.affiliation: Department of Osteoporosis, Inselspital, Berne University Hospital and University of Berne, Freiburgstrasse, 3010 Bern, Switzerland.
authors.forename: Albrecht W
authors.initials: AW
authors.lastname: Popp
authors.forename: Ronald
authors.initials: R
authors.lastname: Schwyn
authors.forename: Damiano
authors.initials: D
authors.lastname: Schiuma
authors.forename: Marius J
authors.initials: MJ
authors.lastname: Keel
authors.forename: Kurt
authors.initials: K
authors.lastname: Lippuner
authors.forename: Lorin M
authors.initials: LM
authors.lastname: Benneker
mesh_terms: D000368:Aged; D015519:Bone Density; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007432:Intraoperative Period; D008159:Lumbar Vertebrae / Q000502:physiology* / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D013123:Spinal Fusion / Q000295:instrumentation* / Q000379:methods
keywords: Bone mineral density; Local bone strength; Pedicle screw failure; Spinal fixation