The effect of lateral wall perforation on screw pull-out strength: a cadaveric study

Area of Science:

• Spinal surgery
• Orthopedic biomechanics
• Spinal instrumentation

Background:

• Pedicle screw fixation is crucial in spinal surgery.
• Lateral pedicle wall perforations are common during screw insertion.
• The biomechanical impact of these perforations on screw stability is not well-quantified.

Purpose of the Study:

• To biomechanically quantify the reduction in pedicle screw pull-out strength caused by lateral wall perforations.
• To compare screw fixation strength in vertebrae with and without lateral perforations.

Main Methods:

• Twenty fresh cadaveric lumbar vertebrae underwent bone mineral density (BMD) assessment.
• Pedicle screws were inserted into two groups: control (no perforation) and experimental (lateral wall perforation).
• Maximal screw pull-out strength was measured using a material-testing system.

Main Results:

• The average BMD was 0.850 g/cm² for both groups.
• Maximal pull-out forces were 1015.8 N (experimental) and 1326.0 N (control).
• The difference in pull-out strength was statistically significant (P < 0.001).

Conclusions:

• Lateral pedicle wall perforations reduce pedicle screw maximal pull-out strength by approximately 23.4%.
• This finding highlights the importance of accurate pedicle screw placement for spinal construct stability.