膝半月軟骨囊腫之超音波影像

Sonographic Features of Meniscal Cyst

骨骼肌肉超音波在軟組織疾患的應用已日益廣泛。然而，在膝半月軟骨囊腫（meniscal cyst）的研究報告仍然不多。本研究的目的在探討膝半月軟骨囊腫的超音波影像特徵及超音波是否為膝半月軟骨囊腫合適的評估工具。此為回溯性研究，收集自民國85年1月至89年7月，臺大醫院超音波檢查診斷為半月軟骨囊腫之病例，共13例；超音波診斷條件為：1）緊鄰膝關節線上的囊腫，2）囊腫直接與半月軟骨相通或在半月軟骨內。其中有9例曾進一步接受核磁共振攝影或手術，此9例皆證實有膝半月軟骨囊腫，顯示超音波對膝半月軟骨囊腫診斷的準確率很高。此13例囊腫的最大徑範圍為0.85公分至8公分（平均2.7公分）。有6例（46.2%）在膝部可摸到腫塊，另7例（53.9%）臨床臆斷為膝內部障礙（internal derangement）。超音波影像的表現有7例呈局部膨大，6例呈延伸長形；囊腫內部回音特性呈單純低回音有7例，另有6例呈混合性回音；大部份的囊腫（61.5%）內部具有隔膜呈多葉性；有69.2%的病例在超音波上可見到半月軟骨有水平方向的裂縫；除|例有輕微血液灌流增加外，其餘12例皆無血流增加現象。骨骼肌肉超音波對膝半月軟骨囊腫的診斷有一定的價值，建議可做為膝部腫塊評估的第一線工具。

This retrospective study included 13 cases of meniscal cyst diagnosed by high resolution ultrasonography, rhe sonographic diagnostic criteria were cyst located adjacent to the knee joint line and in continuity with the meniscus. Nine patients among these 13 had undergone further magnetic resonance imaging or surgical intervention after sonography, and all the diagnoses were confirmed. On sonograms, the size ranged between 0.85 to 8 cm, the shape was a focal bulge in 7 and an extended elongation in 6. Seven were hypoechoic, and 6 had mixed echogenicity-with echogenic substance within a hypoechoic cyst. That is, almost half of the meniscal cysts were mixed echoic rather than hypoechoic. 61.5% of meniscal cysts were lobulated with septa. 69.2% cases were associated with a horizontal tear of meniscus sonographically. Only one case had increased vascularity on color Doppler ultrasonography. We conclude that the accuracy of sonographic diagnosis in meniscal cyst was good, suggesting that sonography could be a simple, inexpensive and accurate tool to evaluate a palpable mass at the knee joint.