Safe Supra-Acetabular Pin Insertion in Relation to Intraosseous Depth

Area of Science:

• Orthopaedic Surgery
• Biomechanical Engineering
• Medical Imaging Analysis

Background:

• Pelvic ring dysfunction often requires supra-acetabular pin insertion for stabilization.
• Current literature lacks standardized guidelines for pin selection and optimal insertion angles.
• Understanding safe corridors is crucial for minimizing complications during pelvic fracture fixation.

Purpose of the Study:

• To quantitatively analyze the narrowing of safe pin corridors in sagittal and transverse planes.
• To determine the impact of increasing intraosseous screw depths on the available insertion space.
• To provide data-driven recommendations for supra-acetabular pin placement in pelvic fractures.

Main Methods:

• A computer algorithm was used to create cross-sections of 3D pelvic reconstructions.
• Simulated screw insertions were analyzed at various sagittal inclinations (45° cranial to 45° caudal) and transverse angles (45° medial to 45° lateral).
• Intraosseous containment was evaluated for screw depths ranging from 60mm to 120mm in 15mm increments.

Main Results:

• The 60mm screw depth offered the widest sagittal (60.9° ± 6.9°) and transverse (27.5° ± 4.1°) ranges at a 30° caudal inclination.
• Increasing screw depth by 15mm significantly reduced these safe ranges (p < 0.01).
• Screws >90mm had limited insertion frequency, requiring more cranial placement and increasing breach risk.

Conclusions:

• While 60mm screw depths allow for greater insertion flexibility, incremental increases significantly restrict safe corridors.
• Screw depths exceeding 90mm are associated with a higher risk of breaching the safe zone.
• Optimal pin selection and trajectory planning are essential for safe and effective supra-acetabular fixation in pelvic fractures.