The new AO classification system for intertrochanteric fractures allows better agreement than the original AO classification. An inter- and intra-observer agreement evaluation

Background: A new AO classification for intertrochanteric fractures was recently published; no studies have evaluated its inter- and intra-observer agreement. Methods: Six evaluators (three hip subspecialists and three residents) assessed radiographs of 68 intertrochanteric fractures; fractures were classified using the original and the new AO classifications. The cases were displayed in a random sequence after a six-week interval for repeat evaluation. We used the Kappa coefficient (k) to determine inter- and intra-observer agreement. Results: Inter-observer agreement was slight (k = 0.128 [0.092-0.170]) using the original and fair (k = 0.250 [0.186-0.327]), with the new AO classification. Orthopedic residents exhibited better agreement than hip surgeons using the original classification (k = 0.302 [0.210-0.416] and k= -0.018 [-0.058-0.029], respectively) and the new classification (k = 0.388 [0.294-0.514] and k = 0.109 [0.031-0.192], respectively). Using both classifications as dichotomous variables (stable or unstable patterns), the agreement was slight (k = 0.158 [0.074-0.246]) using the original classification and moderate (k = 0.425 [0.308-0.550]) with the new AO classification. Intra-observer: The agreement was fair using the original (k = 0.350 [0.278-0.424]) and the new (k = 0.295 [0.239 to 0.353]) AO classifications, respectively. Residents had better agreement than hip specialists using the original (k = 0.405 [0.303-0.512]) versus (k = 0.292 [0.193-0.293]) and the new classification (k = 0.449 [0.370 to 0.528] versus k = 0.129 [0.064 to 0.208]). Conclusion: The inter-observer agreement using the new AO classification was significantly better than using its original version. Also, the new AO classification system allowed better agreement when distinguishing stable from unstable patterns. (C) 2020 Elsevier Ltd. All rights reserved.