The Influence of Thread Tap Mismatch on Pedicle Screw Pullout Strength

Area of Science:

• Orthopedic biomechanics
• Spinal implant technology
• Surgical technique optimization

Background:

• The Dynamic Surgical Guidance Screw (DSG Screw) is designed for direct insertion.
• Understanding the biomechanical properties of surgical screws is crucial for implant performance.
• Optimizing screw insertion techniques can improve fixation strength and patient outcomes.

Purpose of the Study:

• To evaluate the in vitro pullout strength of the SpineGuard/Zavation Dynamic Surgical Guidance Z-Direct Screw (DSG Screw).
• To compare the pullout strength of the DSG Screw using different insertion techniques, including direct insertion without a pilot hole.
• To determine the optimal insertion method for maximizing DSG Screw pullout strength.

Main Methods:

• Dynamic Surgical Guidance Screws (5.5 and 6.5 mm) were inserted into polyurethane blocks (10 PCF density).
• Insertion techniques included: no pilot hole, pilot hole without tapping, undertapping, and line-to-line tapping.
• Screw pullout tests were conducted using a universal testing machine.

Main Results:

• Screws inserted without a pilot hole and tapping exhibited statistically higher pullout strength.
• Insertion without tapping or with undertapping resulted in increased pullout strength compared to line-to-line tapping.
• The direct insertion technique without pilot hole and tapping yielded the greatest pullout strength.

Conclusions:

• The Dynamic Surgical Guidance Screw (DSG Screw) achieves maximum pullout strength when inserted directly without a pilot hole and tapping.
• This insertion technique may enhance screw stability in surgical procedures.
• Further in vivo studies are warranted to confirm these biomechanical findings.