Pedicle screw reinsertion using previous pilot hole and trajectory does not reduce fixation strength.

Area of Science:

• Orthopedic surgery
• Spine biomechanics
• Implant technology

Background:

• Pedicle screw instrumentation is crucial for spinal stability.
• Abnormal intraoperative findings necessitate pedicle screw removal and reassessment.
• The biomechanical impact of reinserting pedicle screws into the same trajectory is not well-established.

Purpose of the Study:

• To biomechanically evaluate the consequence of pedicle screw reinsertion in the thoracic spine.
• To compare the pullout strength and insertional torque of reinserted versus initial pedicle screws.

Main Methods:

• A fresh-frozen human cadaveric biomechanical study involving 31 thoracic vertebral levels.
• Pedicle screws were instrumented, removed, and reinserted along the same trajectory.
• Insertional torque (IT) was measured, and screws were subjected to tensile load to failure to determine pullout strength (POS).

Main Results:

• No significant difference in pedicle screw pullout strength (POS) was observed between reinserted and control screws (P = 0.78).
• Insertional torque (IT) for reinserted screws significantly decreased by 29-33% compared to initial insertions (P = 0.00).
• Significant correlations were found between initial IT and POS (r = 0.79, P = 0.00) and moderate correlations between reinsertion IT and POS (r = 0.56, P = 0.00).

Conclusions:

• Despite a significant reduction in insertion torque, pedicle screw reinsertion along the same trajectory does not compromise fixation strength.
• Surgeons can confidently reinsert pedicle screws using the original trajectory when removal is necessary for intraoperative assessment without significantly impacting biomechanical stability.