Posterior second sacral alar iliac screw insertion: anatomic study in a Chinese population

Area of Science:

• Spinal surgery
• Orthopedic biomechanics
• Radiographic analysis

Background:

• Posterior second sacral alar iliac (S2AI) screw fixation is crucial for spinal instrumentation and fusion.
• Accurate placement is essential for surgical success and avoiding complications.
• Population-specific radiographic parameters are needed for optimal S2AI screw insertion.

Purpose of the Study:

• To define optimal radiographic parameters for S2AI screw placement in a Chinese population.
• To guide the safe and effective instrumentation and fusion of scoliosis to the second sacral level.

Main Methods:

• Three-dimensional computed tomography (3DCT) reconstructions of 60 adult Chinese pelves were analyzed.
• Ideal S2AI screw trajectories were mapped by optimizing length and width, considering entry points 1 mm inferior and lateral to the S1 dorsal foramen.
• Sagittal and transverse plane angulations, trajectory lengths, and entry point distances were measured.

Main Results:

• Ideal S2AI screw trajectories were identified in all pelves.
• Males and females exhibited significant differences in caudal angulation and iliac canal width, with females showing narrower canals.
• Despite differences in maximal trajectory length, intrasacral lengths were comparable between genders.

Conclusions:

• The study successfully identified feasible S2AI screw trajectories and optimal entry angles and lengths for the Asian population.
• These parameters are valuable for clinical practice in guiding S2AI screw insertion for spinal fusion.
• The findings contribute to improving the safety and precision of scoliosis correction surgery in this demographic.