Arthroscopic Characteristics and Risk Factors for Syndesmosis Widening in Chronic Lateral Ankle Instability: A Cross-sectional Study of 521 Patients

Background: To report the measured characteristics of inferior tibiofibular syndesmosis (iTFS) widening—a condition involving abnormal separation of the distal tibia and fibula in patients with chronic lateral ankle instability (CLAI)—and to investigate its associated risk factors. Methods: Consecutive CLAI patients undergoing arthroscopy and Broström surgery between June 2020 and August 2023 were included. The anterior, middle, and posterior parts of the transverse iTFS space was measured by using the customized probe under arthroscopy to explore the characteristics of iTFS widening. Univariate and multivariate logistic regression analysis were used to analyze the relationship between related factors (gender, age, body mass index [BMI], time after initial injury, sprain recurrence, Beighton score, and intra-articular lesions) and iTFS widening. Results: A total of 521 CLAI patients were included. Among those patients, 272 (52.2%) were found with arthroscopic widening at middle syndesmosis ≥3 mm, with 67.3% demonstrating wider posterior interval and narrower anterior interval, 31.3% equivalent posterior and anterior interval, and 1.5% wider anterior interval and narrower posterior interval. According to univariate analysis, female sex ( P < .001), Beighton score ( P = .001), BMI ( P = .008), and osteochondral lesion at lateral talus ( P = .040) were significantly associated with the presence of iTFS widening. Multivariate analysis revealed that female sex ( P < .001; odds ratio 3.130, 95% CI 2.076-4.720) was an independent risk factor of syndesmotic widening in CLAI patients. Conclusion: Among CLAI patients undergoing surgery, 52.2% demonstrated concomitant iTFS widening. Arthroscopic measurements revealed an overall trend of a wider posterior iTFS space and a narrower anterior iTFS space. Female sex was identified as an independent risk factor for arthroscopic iTFS widening in CLAI patients. However, the clinical significance of this widening remains uncertain, as no correlation with patient-reported outcomes or postoperative function was assessed.