膝关节内侧半月板前角罕见异常插入点的关节镜、组织学及影像学观察

Arthroscopic,histological and imaging studies of rare abnormal insertion points in the anterior root of the medial meniscus

目的探讨膝关节内侧半月板前角罕见异常插入点的关节镜、影像学及组织学特征。方法2018年1月至2021年4月,于6500余例膝关节镜手术中发现7例半月板撕裂患者的膝关节内侧半月板前角与前十字韧带之间有罕见的异常插入(前内板股韧带),男4例、女3例;年龄(37.85±7.70)岁(范围27~50岁)。疾病诊断为内侧半月板撕裂4例、内侧盘状半月板撕裂1例、外侧半月板撕裂1例、前十字韧带撕裂+内侧半月板撕裂1例;行半月板修复缝合手术5例、半月板次全切除手术2例。于术中切取异常插入结构即前内板股韧带组织行病理学检查。回顾患者术前MRI片,对照关节镜术中前内板股韧带位置观察前内板股韧带的MRI表现。结果膝关节内侧半月板前内板股韧带起自内侧半月板前角,向外上延伸,匍匐于前十字韧带前方,止于股骨外侧髁前十字韧带前方。在5倍光镜下前内板股韧带实质部表现为束状胶原纤维组织,而前十字韧带残端表现为致密纤维胶原组织,呈束状排列。在术前矢状面MRI T2WI中可清晰识别前内板股韧带,呈低信号,与前十字韧带的信号强度相近。在矢状面图像中7例均可识别,在横断面和冠状面图像中各有2例可识别。3例行双侧膝关节MR检查的患者,双侧膝关节内均见前内板股韧带结构。结论膝关节内侧半月板前角与股骨外髁之间存在解剖变异结构——前内板股韧带,发生率约为0.1%,一般为双侧膝关节同时出现;前内板股韧带为变异结构,存在前内板股韧带的病例半月板前角无骨性止点,通过前内板股韧带与前十字韧带连接;前内板股韧带离断后半月板纤维环形结构破坏,半月板丧失力学特性,术中需小心保护。

Objective To investigate the characteristics of an abnormal attachment point of the anterior horn of the medial meniscus(AHMM)by methods of arthroscopy,radiological imaging,and pathology.Methods A total of seven cases of a rare abnormal attachment(anteromedial meniscofemoral ligament,AML)connecting the AHMM and anterior cruciate ligament(ACL)were identified in the more than six thousand arthroscopic procedures from January 2018 to April 2021.During the procedures,subtotal meniscal resection or meniscal repair was performed in all cases.Tissue removed intraoperatively was used for pathologic examination.For this study,the preoperative MRI films of these patients were retrospectively examined.Results Finally,seven cases with diagnosed meniscal tears were included in this study,including 4 males and 3 females with a mean age of 37.85±7.70 years(range,27-50 years).The AML,which extends outward and upward and is anterior to the ACL,begins at the AHMM and ends anterior to the femoral attachment of the ACL.The histological staining showed that the AML was a bundle of collagen fibers,whereas the ACL was a bundle of dense fibrous collagen.The AML could be clearly identified in the proton-weighted image of sagittal MRI preoperatively and showed a low signaling similar to the signal intensity of the ACL.AML was easily identified on sagittal MRI but not on axial and coronal MRI.In three patients who underwent bilateral MRI,the AML structure was found in both knees.Conclusion The incidence of rare anatomic variation between the AHMM and the lateral condyle of the femur is 0.1%,usually occurring in both knees simultaneously.In cases with this variation,there is no bony attachment in the AHMM connected to the ACL via the AML.After transection of the AML,the annular fibrous structure and mechanical properties of the meniscus are damaged,as consequently the AML should be carefully protected in clinical practice.