الفهرس 
Anatomy of the shoulderOnly 14 pages are availabe for public view
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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.