Abstract
PurposeMuscle strength training is a common strategy for treating chronic ankle instability (CAI), but the effectiveness decreases for mechanical ankle instability (MAI) patients with initial severe ligament injuries. The purpose of this study was to investigate the characteristics and the potential predictors of muscle strength deficit in MAI patients, with a view to proposing a more targeted muscle strength training strategy.MethodsA total of 220 MAI patients with confirmed initial lateral ankle ligament rupture and a postinjury duration of more than 6 months were included. All patients underwent a Biodex isokinetic examination of the ankle joints of both the affected and unaffected sides. Then, the associations between the limb symmetry index (LSI) (mean peak torque of the injury side divided by that of the healthy side) and the patients’ sex, body mass index, postinjury duration, presence of intra-articular osteochondral lesions, presence of osteophytes and ligament injury pattern (i.e., isolated anterior talofibular ligament (ATFL) injury or combined with calcaneofibular ligament injury) were analysed.ResultsThere was significantly weaker muscle strength on the affected side than on the unaffected side in all directions (p < 0.05). The LSI in plantar flexion was significantly lower than that in dorsiflexion at 60°/s (0.87 vs 0.98, p < 0.001). A lower LSI in eversion was significantly correlated with female sex (0.82 vs 0.94, p = 0.016) and isolated ATFL injury (0.86 vs 0.95, p = 0.012). No other factors were found to be associated with muscle strength deficits.ConclusionMAI patients showed significant muscle strength deficits on the affected side, especially in plantar flexion. There were greater strength deficits in eversion in females and individuals with an isolated ATFL injury. Thus, a muscle strength training programme for MAI patients was proposed that focused more on plantar flexion training and eversion training for females and those with an isolated ATFL injury.
Highlights
Lateral ankle sprains are a frequently occurring musculoskeletal injury in sports [1]
34% of individuals suffer from chronic ankle instability (CAI), which is characterized by a recurrent sprain, episodes of giving-way of the ankle joint, pain, swelling and decreased function [2]
The basic patient parameters included sex, body mass index (BMI) and postinjury duration. Data such as the presence of Osteochondral lesion (OCL), osteophyte, isolated anterior talofibular ligament (ATFL) injury or combined calcaneofibular ligament (CFL) injury were gathered from the operative records, which were written by both the operator and the assistant at the operation
Summary
Lateral ankle sprains are a frequently occurring musculoskeletal injury in sports [1]. 34% of individuals suffer from chronic ankle instability (CAI), which is characterized by a recurrent sprain, episodes of giving-way of the ankle joint, pain, swelling and decreased function [2]. Functional treatment, such as muscle strength training and balance training, is a common strategy for treating CAI with good results, especially for those with grade I and II ligament injuries [3]. The conventional muscle strength training programme that applies the same training intensity in each direction of each patient’s ankle joint might not be targeted for those with severe ligament injury and relatively more instability, thereby reducing the training effect. The characteristics and the predictors of muscle strength deficits in MAI patients have rarely been studied
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