A new method of accurate pedicle screw navigation.

Area of Science:

• Spinal surgery
• Surgical navigation
• Orthopedic biomechanics

Background:

• The established planning and alignment (PA) method for pedicle screw navigation relies on referencing patient anatomy for trajectory and entry point (EP) planning.
• Deviations from the planned EP can compromise the final screw position, potentially leading to adverse outcomes.
• There is a need for navigation techniques that are more robust to entry point inaccuracies.

Purpose of the Study:

• To investigate the impact of entry point deviations on pedicle screw placement accuracy.
• To evaluate the efficacy of two novel reference points: screw tip point (STP) and midpoint (MP), as alternatives to the traditional PA method.

Main Methods:

• Computer simulations were employed to assess the performance of the new STP and MP navigation approaches.
• The adapted screw trajectory was defined as the directional vector from the chosen EP to either the STP or MP.
• Navigation techniques were further validated using phantom-sawbone models to analyze screw accuracy in the presence of EP deviations.

Main Results:

• Both STP and MP methods demonstrated a significantly greater number of achievable screw trajectories compared to the PA method (p < 0.01).
• Even with a 4.5 mm EP deviation, the new techniques allowed for perforation-free screw placement with a 4.9 mm diameter.
• Simulated perforations with the PA method were predominantly lateral, with a median distance of 8.45 mm from the medial pedicle wall.

Conclusions:

• The traditional PA navigation method is sensitive to entry point deviations.
• The STP and MP reference point methods represent significant improvements, offering enhanced accuracy and a wider safety margin in pedicle screw navigation.
• These novel techniques hold promise for increasing the reliability and safety of spinal instrumentation procedures.