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

Abstract

BackgroundA new AO classification for intertrochanteric fractures was recently published; no studies have evaluated its inter- and intra-observer agreement. MethodsSix 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. ResultsInter-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-observerThe 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]). ConclusionThe 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.