A preliminary study of reliability of impedance measurement to detect iatrogenic initial pedicle perforation (in the porcine model)

Abstract

Accidental perforation of the vertebral pedicle wall is a well-known complication associated with standard approach of pedicle screw insertion. Depending on detection criteria, more than 20% of screws are reported misplaced. Serious clinical consequences, from dysesthesia to paraplegia, although not common, may result from these misplaced screws. Many techniques have been described to address this issue such as somatosensory evoked potentials, electromyography, surgical navigation, etc. Each of these techniques presents advantages and drawbacks, none is simple and ergonomic. A new drilling tool was evaluated which allows for instant detection of pedicle perforation by emission of variable beeps. This new device is based on two original principles: the device is integrated in the drilling or screwing tool, the technology allows real-time detection of perforation through two independent parameters, impedance variation and evoked muscular contractions. A preliminary animal study was conducted to assess the safety and efficacy of this system based upon electrical conductivity. A total of 168 manual pedicle drillings followed by insertion of implants were performed in 11 young porcine lumbar and thoracic spines. The presence or absence of perforation detection, which defines the reliability of the device, was correlated with necropsic examination of the spines. Using this protocol the device demonstrated 100% positive predictive value, 96% negative predictive value, 100% specificity, and 97% sensitivity. Of 168 drillings there were three (1.79%) false-negatives, leading to a minor effraction, cranially in the intervertebral disks, nine (5.36%) screw threads breaching the vertebral cortex when inserting screws, although preparation of the holes did not indicate any perforation, 34 (36%) breaches detected by the instrument and not detected by the surgeon. These results confirm that the impedance variation detection capability of this device offers a simple and effective means to detect perforation in vertebral pedicle, prior to insertion of pedicle screws. Due to the porcine nerve root anatomy, it was not possible to evaluate the added benefit of cross-linking impedance and EMG detection. A future clinical study may further explore the subject of current study.

Monitoring the reduced scattering coefficient of bone tissues on the trajectory of pedicle screw placement using near-infrared spectroscopy

“…Researchers have reported the false-negative results as high as 23% using EMG monitoring method during PS placement. 18,19 With the development of computer technology, imageguidance in the spine has become an interactive and effective navigation method. Computer-aided stereotactic navigation can provide a three-dimensional (3-D) guide for PS placement.…”

Electrical conductivity measurement: a new technique to detect iatrogenic initial pedicle perforation

“…Initial studies carried out using a large animal model confirmed that the electrical conductivity variation detection capability of this device offers a potentially simple technique to detect pedicle perforations, prior to inserting the screw [4]. A multi-centre trial was undertaken for clinical validation.…”

Reduction in Radiation (Fluoroscopy) While Maintaining Safe Placement of Pedicle Screws During Lumbar Spine Fusion

“…Currently, established guidelines recommend monitoring for personnel who are exposed to greater than 10% of the maximum permissible annual whole-body dose. 21,28,29 Given a permissible whole--body dose of 5000 mrem per year, the levels of radiation exposure documented in this study would place many spine surgeons above this 10% limit.…”

“…The electrical impedance changes as the instrument passes through cancellous and cortical bone as well as soft tissue. 21 When the electrical impedance at the tip of the PediGuard changes, the surgeon is alerted to this change via audible and visual means. The PediGuard is used in an anticipatory function during drilling of the vertebral pedicle.…”