Comparison of talar cartilage thickness between those with and without chronic ankle instability: a ultrasonography study

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Purpose: Chronic ankle instability (CAI) has been linked with the development of ankle post-traumatic osteoarthritis. Individuals with CAI demonstrate early degenerative changes in talar cartilage composition using advanced MR techniques. However, MR-based imaging techniques are not clinically accessible or cost effective. Ultrasonography (US) has emerged as an alternative to MR to assess femoral cartilage morphology, but it remains unknown if US is able to assess between group differences in cartilage thickness at ankle joint. Therefore, the purpose of this study is to determine if US measures of talar cartilage thickness at rest differ between those with CAI and uninjured healthy individuals. Methods: Fifteen individuals with CAI (age: 21.2±1.8 years, height: 1.7±.8m, mass: 67.0±7.7kg) and fifteen uninjured controls (age: 21.0±2.5 years, height: 1.7±.8m, weight: 69.6±13.2kg) volunteered to participate. As recommended by the International Ankle Consortium, individuals with CAI demonstrated a history of at least one lateral ankle sprain and at least two episodes of giving way within the past 6 months; an Identification of Functional Ankle Instability (IdFAI) >11, a Foot and Ankle Ability Measure Activities of Daily Living subscale (FAAM-ADL) < 90%, and a FAAM-Sport subscale (FAAM-S) < 80%. Controls demonstrated no history of ankle sprains and giving way episodes; an IdFAI of < 11, a FAAM-ADL of ≥98%, a FAAM-S of ≥98%. Relative to the controls, CAI participants had a history of multiple lateral ankle sprains (4.0±2.1 vs. 0.0±0.0 sprains), multiple giving way episodes within the past 6 months (6.6±5.1 vs. 0.0±0.0 episodes), higher IdFAI scores (22.9±2.8 vs. 0.1±0.5), and greater limitations in self-reported function based on the FAAM-ADL (85.9±9.7% vs. 100.0±0.0%) and FAAM-S (68.4±20.6% vs. 100.0±0.0%). The US images of talar cartilage thickness were acquired using a LOGIQe system with a 12 MHz linear probe after unloading the cartilage for 30 minutes. For US imaging, participants were positioned supine with the knee in 90 degrees of flexion and the ankle plantar flexed so that the foot was flat on the support surface. The US probe was placed transversely in line with the medial and lateral malleolus and rotated to maximize reflection of the talar articular cartilage surface. Talar cartilage images were manually segmented using ImageJ software to identify the medial, lateral, and overall cross-sectional area (mm2). Cross-sectional area was then normalized to the length of the cartilage-bone interface to obtain an average thickness (mm). Average thickness in each region of interest (i.e. medial, lateral, overall) were compared between CAI patients and healthy controls using independent sample t-tests and an a priori alpha level of 0.05. Results: The CAI and controls groups were similar in terms of their age, height, and weight (p≥0.433). Measures of injury history and self-reported function differed between the groups (p<0.001) as expected. There is no significant difference between the CAI and control groups in the medial (CAI: 0.394±0.089mm, control: 0.435±0.112mm, p=0.276), lateral (CAI: 0.441±0.131mm, control: 0.458±0.117mm, p=0.717), or overall (CAI: 0.427±0.094mm, control: 0.450±0.083mm, p=0.493) regions of interest. Conclusions: Previous studies showed that CAI patients had worse compositional changes (i.e. higher T1rho and T2 mapping relaxation times) of the talar cartilage compared to healthy individuals without morphological degradation (i.e. no decline in cartilage volume). Our results indicate that US thickness measures at rest did not differ between CAI and control groups. This finding supports the existing literature that illustrates no morphological changes in talar cartilage in the early stage of joint degeneration. US appears to be a feasible method for evaluating ankle cartilage morphology, but future research is needed to determine if US based measures of cartilage deformation or resiliency following a standardized loading protocol, which may provide information regarding cartilage composition, differ between CAI and uninjured individuals.