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- Title
Hindfoot alignment assessment by the foot–ankle offset: a diagnostic study.
- Authors
Lintz, François; Ricard, Claire; Mehdi, Nazim; Laborde, Julien; Bernasconi, Alessio; Richardi, Gérard; Sans, Nicolas
- Abstract
Introduction: Foot–ankle offset (FAO) is a three-dimensional (3D) biometric measurement of hindfoot alignment (HA) measured on images from weight-bearing computed tomography (WBCT). Our aim was to investigate its distribution in a large cohort of patients, hypothesizing that threshold FAO values in valgus or varus could be identified as markers for increased risk of associated pathologies. Materials and methods: Prospective, monocentric, level II study including 125 subjects (250 feet) undergoing bilateral WBCT [58.4% female; mean age, 54 years (18–84)]. Patients were clinically assessed and pathologies were classified according to anatomic location (valgus- or varus associated). HA was measured using FAO on 3D datasets and tibio-calcaneal angles (TCA) on two-dimensional Saltzman-El-Khoury views. Threshold FAO values and area under the receiver operating characteristics curve (AUC) were calculated for predicting increased risk of medial or lateral pathologies. Results: Mean FAO was 1.65% ± 4.72 and mean TCA was 4.15° ± 7.67. Clinically, 167 feet were normal, 33 varus and 50 valgus with FAO values of 1.71% ± 3.16, − 4.96% ± 5.30 and 5.79% ± 3.77, respectively. Mean FAO was 0.99% ± 3.26 for non-pathological feet, − 2.53% ± 5.05 for lateral and 6.81% ± 2.70 for medial pathologies. Threshold FAO values of − 1.64% (51.4% sensitivity, 85.1% specificity, AUC = 0.72) and 2.71% (95% sensitivity, 82.8% specificity, AUC = 0.93) best predicted the risk of lateral and medial pathology, respectively. Conclusion: Patients with FAO between − 1.64% and 2.71% had the least risk of degenerative foot and ankle pathology. This interval could be considered a target for patients undergoing realignment procedures. Clinical relevance: A "safe zone" for Foot Ankle Offset was described between − 1.64% and 2.71%, for which the risk of foot and ankle pathologies is lower. Level of evidence: II—Diagnostic study.
- Subjects
RECEIVER operating characteristic curves; COMPUTED tomography
- Publication
Archives of Orthopaedic & Trauma Surgery, 2023, Vol 143, Issue 5, p2373
- ISSN
0936-8051
- Publication type
Article
- DOI
10.1007/s00402-022-04440-2