Interobserver and intraobserver reliability of Salter-Harris classification of physeal injuries

Prognostic value of Salter-Harris (SH) classification is well established. Its reliability, however, can be questioned. We aim to evaluate the interobserver and intraobserver reliability of SH classification and to correlate the level of rater's experience with the correct scoring for each SH subclass.

Twenty-eight independent raters stratified in three levels of seniority evaluated 50 randomly selected radiographs of physeal injuries. The interval for intraobserver reliability was 12 weeks. The overall agreement between raters was assessed using kappa statistics. Student's t-test and Spearman correlation coefficient used to compare results between groups.

Overall kappa for interobserver reliability was 0.45. The mean kappa difference between specialists and residents was significant (p <0.001). The mean kappa difference was also significant between senior and junior residents (p <0.001), favoring senior residents. Intraobserver kappa differs between specialists (0.55) and residents (0.49), but this did not reach statistical significance (p =0.34). SH type II and III demonstrated the highest category-specific kappa coefficient. Seniority was correlated significantly with the number of correct answers (Spearman rho =0.6 p =0.001).

Moderate interobserver reliability that was improved with greater rater's experience was found. Type II and III are the best scored regardless rater's experience. Type I, IV, and V when in doubt, require additional imaging. Hippokratia 2016, 20(3): 222-226.