Laser resonance frequency analysis of pedicle screw stability: A cadaveric model bone study

Area of Science:

• Biomedical Engineering
• Orthopedic Surgery
• Materials Science

Background:

• Current methods for assessing intraoperative pedicle screw fixation (PSF) strength are lacking.
• Accurate intraoperative assessment is crucial for preventing implant failure.

Purpose of the Study:

• To establish and validate a novel laser-based resonance frequency analysis (RFA) system for quantitative, noncontact measurement of intraoperative PSF strength.
• To compare the performance of the laser RFA system with conventional methods.

Main Methods:

• A laser-based RFA system was developed for high-speed, noncontact measurements.
• Pedicle screws were implanted in human cadaveric vertebrae and model bone.
• Measurements included screw pull-out force, peak torque, implant stability quotient (ISQ) via magnetic RFA, and fixation force via laser RFA.
• Data were analyzed using linear and logarithmic approximations to compare laser RFA with conventional metrics.

Main Results:

• In model bone, resonance frequency (RF) strongly correlated with peak torque (R=0.931) and pull-out force (POF) (R=0.931) using logarithmic approximation.
• RF showed a strong linear correlation with ISQ values (R=0.981).
• In cadaveric vertebrae, significant correlations were found between RF and peak torque/POF, with linear approximation yielding higher coefficients for peak torque (R=0.811) and logarithmic for POF (R=0.644).

Conclusions:

• The laser-based RFA system demonstrates a consistent correlation with conventional methods for measuring PSF strength.
• This technology shows promise as a new index for evaluating implant fixation force intraoperatively.
• Laser RFA has the potential to improve the assessment of surgical implant failure risk.