Related Experiment Video
Updated: Oct 12, 2025
An Anesthesia, Surgery, and Harvest Method for the Evaluation of Transpedicular Screws Using an In Vivo Porcine Lumbar Spine Model
Published on: May 31, 2017
The effect of hydroxyapatite on titanium pedicle screw resistance: an electrical model
Scott Davis1, John P Walsh2, Scott Crosby3
1Department of Anesthesiology, LSU School of Medicine, 1542 Tulane Ave, Room 659, New Orleans, LA 70112, USA; Department of Anesthesiology, Tulane School of Medicine, 1430 Tulane Avenue, HC73, New Orleans, LA 70112, USA; Neuromonitoring Associates, Hualapai Commons, 9811 W Charleston Blvd, Las Vegas, NV 89121, USA.
Background Context:
Intraoperative detection of a pedicle wall breach implicitly reduces surgical risk, but the reliability of intraoperative neuromonitoring has been contested. Hydroxyapatite (HA) has been promulgated to increase pedicle screw resistance and negatively influence the accuracy of electromyography.
Purpose:
The primary purpose of this experiment is to evaluate the effect of HA on pedicle screw electrical resistance using a controlled laboratory model.
Study Design:
Controlled laboratory study.
Methods:
Stimulation of pedicle screws was performed in normal saline (0.9% NaCl). The experimental group included 8 HA coated (HAC) pedicle screws and matched manufacturer control pedicle screws without HAC (Ti6Al4V). All screws were stimulated at 5, 10-, 15-, 20-, and 25-mm submersion depths. Circuit current return was recorded, and pedicle screw electrical resistance was calculated according to Ohm's Law. Data were assessed for normality and variance. Mann-Whitney U and Kruskal-Wallis tests compared groups with Bonferroni correction for multiple testing. Effect size is reported with 95% confidence intervals (95CI). p values <.05 were considered significant.
Results:
Current return was detected for all screws (N=24) following subclinical 8.5 µA stimulation at 5, 10-, 15-, 20-, and 25-mm submersion depths (N=144). The effect estimate of HA on pedicle screw electrical resistance is -0.07 (-0.17 to 0.01 95CI). The estimated effect of HA on pedicle screw electrical resistance did not differ across manufacturers. Electrical resistance values were inversely related to submersion depth. Electrical resistance values were lower in the experimental group at 10 mm (p=.04), 15 mm (p=.04), and 25 mm (p=.02) submersion depths. The HA effect ranged from -0.03 to -0.08 as submersion depth varied.
Conclusions:
We found no evidence that HA increased pedicle screw electrical resistance in a matched manufacturer control laboratory model. Electrical stimulation of pedicle screws may be reliable for pedicle breach detection in the presence of HA. Future research should investigate if laboratory findings translate to clinical practice and confirm that electrical stimulation of pedicle screws is a reliable method to detect pedicle breach in the presence of HA.
