Relationship between ATFL-CFL-PTFL angle and subtalar instability.

Abstract

Background: Ankle stability depends on lateral ligaments, yet research on Anterior Talofibular Ligament (ATFL), Calcaneofibular Ligament (CFL), and Posterior Talofibular Ligament (PTFL) angle variations in patients with subtalar joint instability (STJI) remains limited.

Purpose: The aim of this study was to investigate the correlation between the ATFL-CFL-PTFL angles and STJI, which could provide a new idea for effective evaluation of STJI.

Study design: Retrospective case series.

Method: This retrospective study compared 220 subjects from 2010 to 2023: 110 patients with STJI and 110 control group subjects. The two groups of participants were positioned in a neutral supine orientation, and measurements using Magnetic Resonance Imaging (MRI) of the ankle region were conducted. Upon obtaining a detailed MRI scan, the ATFL-CFL-PTFL angle was utilized as a benchmark for comparison between individuals with STJI and those who are healthy.

Results: In the STJI group, the ATFL-PTFL angle was 86.3° ± 3.6°, the ATFL-CFL angle was 131.4° ± 4.7°, and the PTFL-CFL angle was 96.5° ± 4.0°. In the control group (non-STJI group), the ATFL-PTFL angle was 79.5° ± 3.8°, the ATFL-CFL angle was 126.8° ± 3.5°, and the PTFL-CFL angle was 86.3° ± 2.9°. There were significant differences (p < 0.01) in the ATFL-PTFL, ATFL-CFL, and PTFL-CFL angles between the STJI group and the control group.

Conclusion: Although ATFL-PTFL-CFL angle distribution overlapped between STJI and control groups, most STJI patients had significantly higher values, supporting its use as a secondary diagnostic index for STJI.