外側踝扭傷為常見的運動傷害，易造成關節結構或動作模式的改變，進而形成慢性踝關節不穩定。慢性踝關節不穩定會影響本體感覺回饋和肌肉協同收縮策略，因而影響姿勢平衡能力。近似熵為一種統計邏輯分析模式，適於量化時間序列資料的複雜性與隨機性。本研究目的為比較慢性踝不穩定患者健側和患側姿勢平衡參數近似熵的差異。本研究共招募20位單側慢性踝不穩定患者(11位男性和9位女性)，平均年齡21.31.5歲，平均身高166.78.0公分，平均體重65.311.5公斤。受試者測試腳站在Kistler力板上進行8個方向的星型平衡測試，並分析前後方向和內外方向的足底壓力中心軌跡之近似熵，使用成對樣本T檢定比較患側和健側的差異，統計顯著性設為p<.05。足底壓力中心近似熵的結果顯示，在後外方向星型平衡測試中，患側的內外方向足底壓力中心軌跡近似熵值顯著大於健側(p<0.05)，在前內方向星型平衡測試中，患側的前後方向足底壓力中心軌跡近似熵值顯著大於健側(p<0.05)。慢性踝不穩定患者星型平衡測試時患側的足底壓力中心軌跡近似熵顯著高於健側，顯示曾有過扭傷病史不穩定的踝關節在姿勢平衡控制上具有較高的動作變異性。
Lateral ankle sprain is a common sports injury and prone to alteration in ankle joint structure or motion pattern, resulting in chronic ankle instability. Proprioception, muscle contraction strategy and posture balance are affected by chronic ankle instability. Approximate entropy (ApEn) is a suitable model to analyze the regularity and randomness in time series data. Therefore, the purpose of this study was to compare the differences on approximate entropy of postural balance between the affected side and unaffected side in the subjects with chronic ankle instability. Twenty subjects participated in this study (age: 21.31.5years, length: 166.78.0 cm, weight: 65.311.5 kg). The testing leg was on the Kislter force plate to perform the star excursion balance test. The center of pressure (COP) data were collected and ApEn was analyzed. Paired t-test was used to compare the difference between the affected and unaffected sides. The level of significance was set as =0.05. The ApEn on the medial-lateral COP at the affected side was significantly greater than that at the unaffected side in star excursion balance test in the posterior-lateral direction (p<0.05). The ApEn on the anterior-posterior COP at the affected side was significantly greater than that at the unaffected side in star excursion balance test in the anterior-medial direction (p<0.05). This study suggested that high variability on posture balance control was found at the chronically unstable ankle.