Abstract
Purpose
Current coronoid fracture classification systems are based on fragment size and configuration using plain radiographs and/or CT. During surgery, coronoid fracture fragments appear much larger than anticipated because cartilage is radiolucent and therefore not taken into account with preoperative imaging. The purpose of this study was to quantify the articular cartilage thickness of the coronoid process, with reference to coronoid fracture classifications.
Method
Twenty-four cadaveric ulnae were dissected, imaged, and analyzed using the OsiriX software program (3.6–64 bit, Geneva). Thirteen identifiable landmarks were chosen on the coronoid, olecranon and proximal radioulnar joint to measure articular cartilage thickness. Intra-observer and inter-observer reliability were calculated.
Results
Cartilage thickness was highest at the coronoid tip with a mean of 3.0 mm (range, 1.7–4.6mm). Cartilage thickness at the tip was inversely correlated with age (p<0.01), and strongly correlated with overall ulnar height and ulnar length (p<0.05). All measurements had excellent intra-observer and inter-observer reliability.
Conclusion
The thickness of cartilage on the coronoid tip is not insignificant. For example, a 2mm coronoid tip fracture on CT scan may actually appear to be 6 mm thick when viewed clinically at the time of surgery, which may alter the classification category, the decision to treat, or the fixation chosen. Similarly, published cadaveric biomechanical studies have incorporated the thickness of cartilage when creating simulated fractures, introducing a discrepancy between biomechanical studies and clinical studies relying on radiographs. Surgeons should be aware of this discrepancy.
