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Defining Radiographic Threshold Values for the Progressive Collapsing Foot Deformity Classification System: A Large-Cohort Diagnostic Study
Journal article   Peer reviewed

Defining Radiographic Threshold Values for the Progressive Collapsing Foot Deformity Classification System: A Large-Cohort Diagnostic Study

Rebekah Belayneh, François Lintz, Nacime Salomão Barbachan Mansur, Grayson Talaski, Donald Anderson, Scott J Ellis and Cesar de Cesar Netto
Foot & ankle international
07/07/2026
DOI: 10.1177/10711007261449247
PMID: 42411763

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Abstract

The Progressive Collapsing Foot Deformity (PCFD) classification categorizes deformity patterns into 5 classes (A, hindfoot valgus; B, midfoot/forefoot abduction; C, medial column collapse; D, peritalar subluxation; E, ankle valgus). Currently, the classifying process relies on surgeons' experience and interpretation of clinical and radiographic measurements. The goal of the present study was to establish cut-off threshold values for commonly used PCFD measurements assessing class A to D, using 2 large cohorts of PCFD patients and controls. This prospective comparative diagnostic study included 154 neutrally aligned or asymptomatic flatfoot volunteers (103 females, mean age 41.7 years, body mass index [BMI] 28.9) and 321 PCFD patients (136 females, mean age 50.7 years, BMI 29.8). Participants underwent weight-bearing computed tomography (WBCT). Measurements were obtained after blinded segmentation and included hindfoot moment arm (HMA, class A), talonavicular coverage angle (TNCA) and talus-first metatarsal angle axial (TFMA-A, class B), talus-first metatarsal angle sagittal (TFMA-S) and forefoot arch angle (FAA, class C), and coverage maps (middle facet [MF], posterior facet [PF], sinus tarsi [ST], class D). Receiver operating characteristic curves, Youden indexes, and areas under the curves (AUCs) identified optimal cut-offs. A partition prediction model refined those values, and a multivariate analysis identified independent predictors of symptomatic PCFD. Optimal cut-off values (all  < .0001) included the following: HMA ≥ 13.9 mm (AUC 85.3%, class A); TNCA ≥ 38.7° (AUC 84.4%) and TFMA-A ≥ 20.3° (AUC 82.1%, class B); FAA ≤ 8.7° (AUC 83.9%) and TFMA-S ≥ 18.7° (AUC 82.9%, class C); MF coverage ≤ 73.5% (AUC 73.4%), PF coverage ≤ 84.5% (AUC 82.7%), and ST coverage ≥ 25.7% (AUC 84.4%, class D). HMA, TNCA, MF, and ST coverages were identified as independent predictors of PCFD. This study established robust cut-off values for PCFD measurements across classes A-D using large comparative cohorts, significantly enhancing diagnostic performance (AUC ≥ 80% for most). These thresholds improve the clinical applicability and reliability of the PCFD classification, supporting clinical and surgical decision making and facilitating future comparative research. Level II, prospective comparative diagnostic study.
 weightbearing CT diagnostic study peritalar subluxation progressive collapsing foot deformity flatfoot threshold values staging

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