J Neurosurg Spine 21:821–825, 2014 821 ©AANS, 2014 J Neurosurg: Spine / Volume 21 / November 2014 P edicle screw instrumentation is widely used in the lumbar spine as a means of stabilization to enhance arthrodesis, and it has recently gained acceptance for use in the thoracic spine. The use of pedicle screws for fxation is not without complications, however, with reported rates of breach ranging from 15% to 54%. 2,3,12,13 Perforations can further lead to complications such as dural tear, nerve root injury, spinal cord injury, vascular injury, or vertebral fractures. The accuracy with which such instrumentation can be placed has been and continues to be the topic of much investigation. Much of the variation in perforation rates in the literature depends on the method used to determine the perforation. Studies using a postoperative CT scan show higher rates of perforation than those using radiographic assessment. Learch et al., using cadaver specimens of the lumbar spine, found that only 63% of screw positions were correctly identifed on radiographs as compared with 87% on CT images. 9 No test exists that gives surgeons 100% sensitiv- ity and specifcity with regard to impending breach, and electromyography-assisted pedicle screw placement warns of impingement on nerves but only after a breach has oc- curred. Therefore, the PediGuard dynamic surgical guid- ance device (SpineGuard) has been developed to aid sur - geons in achieving safer pedicle screw placement. This hand-held pedicle placement device uses audio alerts along with light-emitting diode (LED) warning lights to guide the surgeon. Electrical conductivity is mea- sured at the tip of the probe, allowing relative differen- tiation of tissue conductivity, measured at 5 samples per second. The PediGuard device emits a different sound (frequency and pitch) to differentiate cancellous bone from cortical bone (“anticipation” of impending breach) and saline (indicating breach). Previous studies claim up to 98% specifcity and 99% sensitivity with regard to the detection capabilities of this new pedicle-probing device. Other claims include up to a 30% reduction in the use of intraoperative fuoroscopy and a 15.4% reduction in screw placement time. 1 The purpose of the present study was to impartially Independent assessment of a new pedicle probe and its ability to detect pedicle breach: a cadaveric study Laboratory investigation PhilliP T. Guillen, M.D., 1 Ryan G. KnoPPeR, B.S., 2 JaReD KRoGeR, B.S., 2 naThaniel D. Wycliffe, M.D., 3 oluMiDe a. DaniSa, M.D., 1 anD W ayne K. chenG, M.D. 1 Departments of 1 Orthopaedic Surgery and 3 Radiology, Loma Linda University Medical Center, and 2 School of Medicine, Loma Linda University, Loma Linda, California Object. The authors undertook an independent, non–industry funded cadaveric study to evaluate the effcacy of a pedicle-probing device, which uses impedance measurement to warn of impending and actual pedicle screw breach. Methods. A previously validated fresh-frozen cadaver model (saline-soaked spine) was used. Individuals at 3 levels of training (attending spine surgeon, orthopedic surgery resident, and medical student) used a cannulated pedi- cle-probing device to cannulate each of the levels between T-2 and S-1. Each pedicle was cannulated freehand using 2 approaches: 1) a standard trajectory through the middle of the pedicle, and 2) a medial trajectory aimed to breach the medial wall of the pedicle. A 16-slice helical CT scanner was used. The images were interpreted and analyzed by 2 orthopedic spine surgeons and a neuroradiologist. Results. The sensitivity of the pedicle probe to detect impending breach or breach of 4 mm or less was 90.06%. The sensitivity in detecting medial wall breach was 95.8%. The positive predictive value was 87.1%. The device detected medial breach more often than lateral breach. Conclusions. This study showed that this pedicle-probing device could reasonably be used to detect impending breach and actual breach of 4 mm or less. Medial breach was detected better than lateral breach. Use of the pedicle probe may improve patient safety. (http://thejns.org/doi/abs/10.3171/2014.6.SPINE131028) Key WoRDS • pedicle screw • PediGuard • pedicle breach • cadaveric study • technique Abbreviation used in this paper: PPV = positive predictive value.