Inter- and intra-observer reliability of the new AO/OTA classification of proximal femur fractures

•The 2018 AO/OTA classification has a “moderate” inter-observer reliability at group (e.g. 31-A1) level, this reduces to “fair” reliability at sub-group (e.g. 31-A1.1) with sub-group classifications.•Intra-observer reliability is comparably higher than inter-observer reliability being “substantial” to “moderate”.•Despite attempts to simplify and re-define inter-trochanteric fractures, the 2018 AO/OTA classification remains difficult to apply consistently and reliably.