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Clinical History(临床病史): The patient is a 35-year-old man who presents with a painful knee after a sports injury.
35岁男性，运动后出现膝关节疼痛。
Findings(影像所见): Sagittal proton density MR images of the patient's knee demonstrate truncated anterior and posterior horns of the medial meniscus without the normal bow-tie configuration as well as a low-signal intensity band parallel and anterior to the PCL (double-PCL sign). Coronal STIR images demonstrate a displaced meniscal fragment within the intercondylar notch.
Diagnosis(诊断): Bucket-handle tear of the medial meniscus.内侧半月板桶柄状撕裂
桶柄状撕裂(bucket handle tear , BHT) 是半月板损伤一种特殊类型,病损严重,常导致膝关节交锁, 但在MRI 检查上却极易遗漏。
Helms在诊断BHT 时提出蝶结消失征(absent bow tie sign ,ABTS) ,敏感性97 %。根据Helms 描述 ,正常膝关节在矢状面上内侧或外侧半月板前角和后角通过体部相连接,断面上形状像蝴蝶领结状,简称蝶结。在层厚4～5 mm ,间距0～0. 5 mm的MRI 影像上,这种靠体部连接的蝶结至少有2 个。半月板BHT损伤时,蝶结只有一个或没有，这种影像称蝶结消失征。
BHT损伤是半月板纵行撕裂的特殊形式,大样本的发生率为9 %～24 %。发生在年轻患者居多,损伤在内侧半月板是外侧的2～3 倍。用MRI 诊断有很大难度,常见的征像包括(1) 冠状面上,髁间窝内有低信号的半月板组织位于交叉韧带旁。(2) 矢状面上出现双后交叉韧带征。(3) 矢状面显示残余的前角或后角变小或截断,信号有或无增高。(4) 蝶结消失征。
正常成人半月板宽度9～12 mm , 故在常规层厚4～5 mm,间距0～0. 5 mm的MRI 矢状面成像上至少有2 个以上蝶结存在。一旦BHT 桶柄移入髁间窝,半月板宽度显著减小,将会出现ABTS ,此时可伴有双后交叉韧带征。但少数病例如内、外翻膝关节畸形中,内、外侧间室变小,半月板退变、磨损,小儿半月板也会出现ABTS。
Discussion(讨论): A displaced longitudinal tear of the meniscus is called a bucket-handle tear because the separated central fragment resembles the handle of a bucket. Patients with bucket-handle tears may present with a locked knee or a lack of full extension. Bucket-handle tears involve the medial meniscus three times more often than the lateral meniscus. The central fragment may be partially displaced or may be completely displaced into the intercondylar notch as is frequently demonstrated on coronal images. Bucket-handle tears effectively reduce the width of the meniscus, resulting in truncation of the anterior and posterior horns on sagittal images, and peripheral sagittal images fail to demonstrate the normal bow-tie configuration of the body of the meniscus. Another helpful imaging finding which is sometimes seen is the double-PCL sign which is the presence of a low-signal intensity band parallel and anterior to the PCL, caused by the displaced meniscal fragment within the intercondylar notch. A partial menisectomy can be performed for nonseparated symptomatic tears.
Reference:
Stoller DW, Cannon WD, Anderson LJ. The Knee. In: Magnetic Resonance Imaging
in Orthopedics and Sports Medicine, 2nd Edition. Stoller DW. Lippincott-Raven;
Eds. 1997:273-277.
Resnick D. Internal Derangements of Joints. In: Diagnosis of Bone and Joint Disorders,
3rd Edition. Ed. Resnick D. W. B. Saunders, Co., Philadelphia; 1995(5):3069-3098.
Weissleder R, Rieumont MJ, Wittenberg J. Primer of Diagnostic Imaging, 2nd Edition.
Mosby, St. Louis; 1997:372-374.
文章来自：影像园
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