On two occasions, five surgeons classified a cohort of 150 consecutive patients with congenital upper limb anomalies according to the Oberg-Manske-Tonkin classification (2020 update). We estimated reliability for the main anomaly code by means of Cohen's kappa (Κ) for ten rater pairs for five common and easily distinguishable anomalies (Group 1), and for all the other anomalies (Group 2). Inter-rater reliability for all patients (n = 150) was substantial, almost perfect for Group 1 (n = 64), but only moderate for Group 2 (n = 86). Intra-rater reliability was higher for all groups. We suggest simplifications to the Oberg-Manske-Tonkin classification and highlight specific requirements for instructions to increase its reliability.Level of evidence: I.
Keywords: Classification; OMT; Oberg–Manske–Tonkin; congenital anomaly; reliability.