الفهرس | Only 14 pages are availabe for public view |
Abstract SUMMARY The shoulder is an extremely mobile joint, but at expense of its stability. Glenohumeral joint instability can be globally classified into anterior instability, as well as the less common posterior and multidirectional instabilities. The most common findings in the anterior instability is the Bankart lesion, both type I (Cartilagenous) and type II (bony) Bankart lesions. Associated depression injury at the postero-lateral superior aspect of the humeral head may be also noted and called Hill Sachs lesion. Perthes lesion represent a variant of Bankart lesion where there is detachment of the inferior glenohumeral ligament complex from its glenoid attachment with intact scapular periosteum which is seen stripped off medially. The anterior shoulder dislocation may also results in another types of injuries as the ALPSA lesion representing the anterior labroligamentous periosteal sleeve avulsion, GLAD lesion described as the gleno-labral articular disruption, as well as the HAGL lesion mentioned as the humeral avulsion of the glenohumeral ligament. Posterior shoulder instability is relatively rare and it should be suspected in the presence of posterior labral disruption or fragmentation. The common finding in posterior instability is the reversed Bankart lesion, which represent posterior labral/ capsular/glenoid rim injury secondary to posterior dislocation. An associated antero-medial superior humeral head impaction may also be identified. Another injury encountered in posterior dislocation is the Bennet lesion which represent cresentic posterior extracapsular ossification secondary to posterior capsular avulsion. In multidirectional instability the ligament laxity is bilateral and atraumatic with generalized joint laxity. No visible labral or ligamentous injury are seen in these patients and the capsular ligaments are redundant and the labrum is often hypoplastic. Some patients may present with a dominant unidirectional instability. Operative treatment is considered only after failure of conservative therapy. In management of recurrent shoulder instability there are many different surgical procedures, open and arthroscopic have been used. MRI can be of significant benefit in understanding the alterations of anatomy mediated by surgery in patients with shoulder lesions, particularly those related to rotator cuff disease and shoulder instability. It can detect pathology that may mimic such pathology, such as paralabral cysts, or uncover lesions of instability that may be mediating such rotator cuff pathology. In patients with recurrent instability, it may reveal the anatomic lesions that are causing such dysfunction, including recurrent Bankart lesions, and bony defects. It may reveal other complications such as degenerative joint disease, or recurrent instability in another direction. In evaluation of the postoperative shoulder, choices among MR imaging sequences and techniques should be made carefully. To avoid magnetic susceptibility artifacts at MR imaging, inversion recovery may be used instead of fat saturation, and fast spin-echo sequences may be used instead of conventional spin-echo sequences or gradient-echo sequences. MR arthrography, whether indirect or direct is most useful for optimal delineation of the capsulolabral structures, rotator cuff and tendon defects, yielded fewer errors and thus is accurate in the diagnosis of pathological labral conditions in patients with recurrent or residual symptoms after shoulder instability repair. It is also accurate for depicting Hill-Sachs lesions and long head of biceps tendon abnormalities as well as glenoid and \ or humeral articular cartilage abnormalities so is recommended over non-enhanced MR imaging. |