Purpose

The lateral ankle ligament complex consists of three major ligaments: anterior talofibular ligament (ATFL), calcaneofibular ligament (CFL), and posterior talofibular ligament (PTFL)¹. ATFL injury occurs most frequently and is thus of high clinical importance, followed by combined injury of ATFL and CFL². 10%–30% of patients with repeat ankle sprains may develop into chronic lateral ankle instability (LAI)¹. Chronic LAI altered tibiotalar kinematics, which has been suggested to contribute to the development of chondral lesions and the progress of osteoarthritis (OA)³. Previous studies mainly focused on the cartilage change resulting from isolated ATFL injury. However, there are limited data on the cartilage alteration of combined ATFL and CFL tear. Therefore, the purpose of this study was to quantitatively evaluate the cartilage alteration of talus for chronic LAI with isolated ATFL tear and combined ATFL and CFL tear using T2-mapping, which is a very powerful tool for noninvasive assessment of biochemical changes in the cartilage matrix that precede morphological deterioration4, and analyze the correlation between T2 value and AOFAS score.

Methods

A total of 27 patients and 21 healthy controls were included in this study. Patients were divided into two groups: 1) ATFL group, 17 patients with ATFL tear; 2) ATFL+CFL group, 10 patients with combined ATFL and CFL tear. MRI examinations were performed on a 3T scanner(MAGNETOM Verio, Siemens Healthcare, Erlangen, Germany) with a gradient strength of 45mT/m using an 8-channel phased array coil. The MR imaging sequences and parameters are displayed in Table 1. T2 maps and AOFAS scores were acquired for all patients. The total talar trochlear cartilage (TTC) was manually segmented into six compartments by two radiologists: medial anterior (MA), medial center (MC), medial posterior (MP), lateral anterior (LA), lateral center (LC), and lateral posterior (LP), and the T2 value of each compartment was measured from the T2-mapping images. Then, the color-scale T2-mapping images were fused with T2-weighted images to reflect the detailed topographic distribution of T2 value using a MRWP workstation (Siemens Healthcare, Erlangen, Germany). Data were analyzed with one-way analysis of variance (ANOVA), Student's t-test and Pearson's correlation coefficient. Statistical significance was defined with P<0.05.

Results

There were no significant differences in age, sex or BMI between patients and control subjects. The T2 values of MA, MC, MP, LC cartilage compartments and TTC were significantly different among the ATFL, ATFL+CFL and control group (Table 2). More specifically, the T2 values of the ATFL group were significantly higher than those of controls in MA, MC, MP cartilage compartments and TTC (P<0.001, P=0.033, P=0.003, P<0.001, respectively) (Fig.1, Fig. 2. A). The T2 values of the ATFL+CFL group were significantly higher than those of controls in MA, MC, MP, LC, LP cartilage compartments and TTC (P=0.011, P=0.001, P<0.001, P=0.005, P=0.032, P<0.001, respectively) (Fig.1, Fig. 2. B). Moreover, the T2 values of the ATFL+CFL group were higher than those of the ATFL group in MC, MP, LC cartilage compartments and TTC (P=0.016, P=0.017, P=0.037, P=0.04, respectively) (Fig.1, Fig. 2. C). The AOFAS score of the ATFL+CFL group was significantly lower than those of the ATFL group (57.50±5.06 vs 70.71±6.19, P<0.001). The T2 values of MA compartment in ATFL and ATFL+CFL groups were negatively correlated with AOFAS scores (r=-0.596, P=0.012; r=-0.690, P=0.027, respectively), while no statistically significant correlations were found between T2 values of other cartilage compartments and AOFAS scores (P>0.05).

Discussion and Conclusion

Chronic LAI with isolated ATFL tear may be connected to the occurrence of cartilage degeneration in talus trochlea, mainly involving medial cartilage compartments. This finding is consistent with previous studies using finite element analysis5,6, which indicated that the increased anterior translation and internal rotation of the talus may lead to increased abutment and stress distribution on the medial cartilage compartment of the talus. Besides, the combined ATFL and CFL tear may result in much larger and more severe cartilage degeneration than isolated ATFL tear. The CFL is injured by more severe inversion stress than ATFL. When the ATFL and CFL were damaged, significant increases in inversion and supination have been observed compared to isolated ATFL7,8. Additionally, MA is the main cartilage compartment which may affect the patient’s clinical symptom and prognosis. This finding may suggest that the monitoring of MA is important for chronic LAI patients, and the degeneration of MA should require early intervention in order to improve the patient’s clinical symptoms and prognosis. Finally, MRI T2-mapping can play a major role in detecting cartilage degeneration at an early stage to help plan treatment and monitor disease progression for chronic LAI.

Acknowledgements

No acknowledgement found.

References

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