Understanding coronoid process morphology and O'Driscoll Type 1 and Type 2 fracture patterns through 3D fracture and heat mapping techniques.

BACKGROUND: Coronoid process fractures, which comprise 10-15% of elbow injuries, are critical contributors to joint instability but remain poorly characterised in three dimensions (3D), particularly at the fragment level. This study addressed this gap by generating 3D fracture and heat maps of O'Driscoll Type 1 and Type 2 coronoid fractures to improve the understanding of coronoid process morphology, fracture patterns and inform device designs. METHODS: Thirty-three unilateral CT scans underwent in-silico reduction using Quantitative 3D Computed Tomography (Q3DCT). Fracture lines were overlaid on a healthy coronoid template in anterior, superior, lateral, and medial views to produce detailed maps, and frequency-based heat maps highlighted structural high-fracture points. RESULTS: From the analysed sample, Type 2 fractures predominated (63.6%), with 15 cases of Subtype 2 (oblong anteromedial) and 6 of Subtype 3 (comminuted), while 12 cases were Type 1. Heat maps revealed a single dominant anterior high-density fracture point for Type 1 and Type 2 Subtype 2, multiple superior high fracture-line frequency zones, a mid-height lateral band, and an extended medial path from the trochlear surface to the rim. The analysis shows that these patterns exhibit repetitive fragment shapes: trapezoidal for Type 1, oblong for Subtype 2, and variable for Subtype 3, all of which are crucial for achieving targeted device coverage. CONCLUSION: The findings align with prior mapping studies of O'Driscoll Type 1 and Type 2 fractures; however, they contrast with the reported frequency of anteromedial radial head fractures. Limitations include variable scan quality, exclusion of Type 3 fractures, and a male-dominant, regionally confined cohort. Future work should incorporate Type 3 fractures, broaden demographic diversity, leverage machine-learning segmentation, and perform biomechanical validation to refine patient-specific fixation strategies and generalizability. LEVEL OF EVIDENCE: Level IV: Case Series; Prognosis Study.