Description and Reliability of a Novel Classification System for Comminuted Fractures of the Patella

This study developed a classification system for comminuted patella fractures based on anatomic zones of comminution: Type 1 (proximal), Type 2 (central or stellate), and Type 3 (distal). The system's reliability was tested by 30 graders (junior residents, senior residents, fellows, and attendings) who assessed 60 fracture cases twice, one month apart, for a total of 120 assessments. Interobserver reliability, measured by Fleiss' kappa, was 0.67, showing substantial agreement, while intraobserver reliability, measured by Cohen's kappa, was 0.82, indicating excellent agreement. Reliability was consistent across experience levels. This novel classification system for comminuted patella fractures demonstrated substantial interobserver and excellent intraobserver reliability, but clinical validation is needed to confirm its practical utility.