A Novel Method for Minimizing Variability in Biomechanical Research: Validation Study of a Low-Cost, High-Quality Biomechanical Research Laboratory

Introduction: Spine biomechanical research affords the invaluable opportunity to translate in vivo clinical observations into advances in clinical spine care. Most published spine biomechanical studies evaluating pedicle screw performance have very high relative standard deviations (SD), with some SD reported as high as 78% of the mean.We present a novel method for improving the quality of pedicle screw performance testing using a novel, low-cost biomechanical testing laboratory.

Methods: A novel testing method for measuring the axial pullout strength (PO) and insertional torque (IT) of a pedicle screw was developed. Means and standard deviations of 30 index test specimens were compared to prior literature using the coefficient of variance (CoV) F-test. Estimated interquartile ranges (eIQR) were calculated assuming a normal distribution of data, using the MedCalc Software Package 2023.

Results: The mean IT for our 30 test blocks was 97.65 Ncm, with an eIQR of 17.5 Ncm, SD of 8.89 Ncm, and CoV of 9.11%. The axial PO data had a mean of 1016.67 N, eIQR of 108 N, SD of 77.65 N, and CoV of 7.64%. Our study demonstrated significant reductions in CoV for both PO and IT testing compared to historical cadaveric studies, with comparable or better results when compared to synthetic model studies.

Conclusion : This study proposes a novel method to minimize variability in basic spine biomechanical research. Our results suggest that this new method significantly improves the quality of spine biomechanical research data at a reduced cost over the existing method.