• Matthieu Lalevée, Barbachan MansurNacime SalomaoNS0000-0003-1067-727XDepartment of Orthopedics and Rehabilitation, Carver College of Medicine, University of Iowa, 200 Hawkins Dr, John PappaJohn Pavillion (JPP), Room 01066, Lower Level, Iowa City, IA, 52242, USA.Department , Hee Young Lee, Amanda Ehret, Tutku Tazegul, Kepler Alencar Mendes de Carvalho, Eric Bluman, and Cesar de Cesar Netto.
• Department of Orthopedics and Rehabilitation, Carver College of Medicine, University of Iowa, 200 Hawkins Dr, John PappaJohn Pavillion (JPP), Room 01066, Lower Level, Iowa City, IA, 52242, USA.
• Arch Orthop Trauma Surg. 2023 Mar 1; 143 (3): 133113391331-1339.

IntroductionBluman et al., flatfoot classification is based on posterior tibial tendon (PTT) dysfunction leading to a chronological appearance of several foot deformities. An expert consensus recently proposed a new classification named Progressive Collapsing Foot Deformity (PCFD) in which the focus was shifted to five different independent foot and ankle deformities and their flexibility or rigidity. The aim of this study was to compare Bluman and PCFD classifications. We hypothesize that both classifications will be reliable and that the PCFD classification will allow a larger distribution of the different types of foot deformity.Materials And MethodsWe performed a retrospective IRB-approved study including 92 flatfeet. Three foot and ankle surgeons reviewed patient files and radiographs to classify each foot using both classifications. Bluman classification was performed one time as initially described and a second time after removing the Angle of Gissane sclerosis sign. Interobserver reliabilities were determined with Fleiss' kappa values.ResultsInterobserver reliabilities of Bluman and PCFD classifications were, respectively, substantial 0.67 and moderate 0.55. PCFD Class C and D reliabilities were, respectively, slight 0.07 and fair 0.28. The 276 readings were spread into 10 substages in Bluman and 65 subclasses in PCFD. The progressivity of the Bluman classification prevented the combination of flexible hindfoot valgus (II Bluman, 1A PCFD), midfoot abduction (IIB, 1B) and medial column instability (IIC, 1C) which was frequent in our study (112/276 readings, 40.6%). By removing the Angle of Gissane sclerosis sign from the Bluman classification, the prevalence of stage III decreased from 44.2 to 10.1%.ConclusionsBluman and PCFD classifications were reliable. The PCFD classification showed a larger distribution of different types of flatfeet but Classes C and D need better definition. The progressivity of Bluman classification causes inconsistencies and Gissane angle sclerosis sign is inappropriately used and might lead to incorrect surgical indications.© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.

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