Achievable pin spanning angulation in anterosuperior pelvic external fixation

Area of Science:

• Orthopedic surgery
• Biomechanical engineering
• Medical imaging analysis

Background:

• Anterosuperior pelvic external fixation offers rapid stabilization without fluoroscopy.
• Current literature lacks clear guidelines on optimal angular differences between iliac crest fixation pins.
• Understanding these parameters is vital for improving surgical outcomes.

Purpose of the Study:

• To determine the maximum sagittal pin spanning angulation (SPSA) achievable with two iliac crest pins.
• To investigate the impact of intraosseous depth (ID) on SPSA and transverse pin spanning angulation (TPSA).

Main Methods:

• Utilized a novel computer algorithm to generate sagittal cross-sections of 3D pelvic models.
• Simulated pin insertions with intraosseous depths (ID) of 60, 75, and 90 mm at 5° increments.
• Assessed pins for cortical containment to establish SPSA and TPSA values.

Main Results:

• Observed a bimodal distribution for pin insertion frequency and SPSA.
• Caudal pin placement demonstrated superior cortical containment with larger SPSA and TPSA values.
• A 60 mm ID yielded the highest insertion frequency (85.7%) and largest SPSA (155°), with increased ID reducing SPSA and TPSA.

Conclusions:

• Achieving wider SPSA in anterosuperior pelvic fixation is limited by the iliac wing's narrow corridor for intraosseous pin containment.
• A 60 mm ID provides superior SPSA and cortical containment compared to greater IDs, enhancing pelvic stabilization.
• These findings aid in optimizing pin placement for improved external fixation outcomes.