Post-traumatic subtalar osteoarthritis: which grading system should we use?

To assess and compare post-traumatic osteoarthritis following intra-articular calcaneal fractures, one must have a reliable grading system that consistently grades the post-traumatic changes of the joint. A reliable grading system aids in the communication between treating physicians and improves the interpretation of research. To date, there is no consensus on what grading system to use in the evaluation of post-traumatic subtalar osteoarthritis. The objective of this study was to determine and compare the inter- and intra-rater reliability of two grading systems for post-traumatic subtalar osteoarthritis. Four observers evaluated 50 calcaneal fractures at least one year after trauma on conventional oblique lateral, internally and externally rotated views, and graded post-traumatic subtalar osteoarthritis using the Kellgren and Lawrence Grading Scale (KLGS) and the Paley Grading System (PGS). Inter- and intra-rater reliability were calculated and compared. The inter-rater reliability showed an intra-class correlation (ICC) of 0.54 (95 % CI 0.40-0.67) for the KLGS and an ICC of 0.41 (95 % CI 0.26 – 0.57) for the PGS. This difference was not statistically significant. The intra-rater reliability showed a mean weighted kappa of 0.62 for both the KLGS and the PGS. There is no statistically significant difference in reliability between the Kellgren and Lawrence Grading System (KLGS) and the Paley Grading System (PGS). The PGS allows for an easy two-step approach making it easy for everyday clinical purposes. For research purposes however, the more detailed and widely used KLGS seems preferable.