by: Michelle Thomas
True shoulder dislocation occurs when the head of the humerus becomes dislodged from the glenoid cavity. It is the joint that is most prevalent for dislocation. The shoulder normally dislocates anteriorly but it can also be displaced posteriorly or inferiorly. If the humerus is dislocated once, there is a greater chance that it can later be dislocated again, especially if the person is 30 years or younger. Many times when a shoulder dislocation occurs, ligaments and other tissues are damaged and movement of the humerus is highly limited. Once the shoulder is relocated normal function is usually restored but structures around the glenoid area may still be damaged. The two most common injuries associated with an anteriorly dislocated shoulder are a Bankart lesion and a Hill-Sach’s lesion. A Bankart lesion occurs when the anterior labrum is torn. A Hill-Sach’s lesion takes place when the humeral head impacts the glenoid fossa causing a fracture of the head of the humerus. These lesions can also occur in the posterior joint with posterior dislocation, and are known as reverse Bankart and Hill-Sach’s lesions.1,2,4
All About Shoulder Dislocation
The anatomy of the glenohumeral joint consists of the humeral head of the humerus and the glenoid fossa of the scapula.
These two structures together create a cavity with a surrounding capsule. Attached to the glenoid cavity is the glenoid labrum which acts as a fibrocartilaginous bumper between the humeral head and the glenoid fossa.
The capsule is supported by the rotator cuff muscles which are the supraspinatus, infraspinatus, subscapularis, and teres minor.
The deltoid muscle and the biceps tendon also offer some support for the capsule.
The superior glenohumeral ligament (SGHL), middle glenohumeral ligament (MGHL), and inferior glenohumeral ligament (IGHL) are three structures that provide support as well.3
III. Prevalence & Etiology
Anterior dislocations occur in 98% of shoulder dislocations. The other 2% of shoulder dislocations take place posteriorly. The majority of dislocations occur from a traumatic incidence. Forced external rotation and abduction of the humerus is the most prevalent cause of anterior dislocation. About 5% occur atraumatically, usually because of excessive laxity of the capsule. Recurrence of dislocation can also be problematic. In people aged 20 years or younger, dislocation can recur in 66% to 100% of cases. For people between 20 and 40 years old 13% to 63% of dislocations recur and for people 40 years and over 0% to 16% dislocate their shoulder again.4
IV. Clinical Presentation
Most patients will state that they heard a popping sound at the time of injury. Anterior dislocation is the most common form of shoulder dislocation and normally the patient will have had their arm abducted and externally rotated at the time of injury. It may also present this way in clinic if it has not been relocated. They may have also felt numbness or tingling down the arms after injury if a nerve was affected. If the shoulder was not put back into place, then AROM will be decreased and painful, and the humeral head may be palpable anteriorly. Brusing may be visible if blood vessels were ruptured. With a posterior dislocation, ROM and strength tests are usually normal unless a rotator cuff muscle or nerve has been damaged. Crepitus may be present when the shoulder is internally rotated and the posterior joint line may be tender to palpation. If the humeral head has not been relocated, the humerus may appear internally rotated and will not be able to externally rotate.1,2,5
V. Diagnostic Tests
With both anterior and posterior shoulder instability, an anteroposterior (AP) view and a Y-view image should be obtained. The AP view can show anterior dislocation and a reverse Hill-Sach’s sign for posterior dislocation. The Y-view can show a Hill-Sach’s lesion for anterior dislocation and a posterior dislocation.6,7
Reverse Hill-Sach's Lesion
CT scans can also be used to assess the integrity of the labrum. An MRI shows Bankart lesions and any soft tissue injuries.6,7
MRI Bankart Lesion
VI. Special Orthopedic Tests
The three tests that are most reliable for anterior shoulder instability are the apprehension, relocation, and anterior release tests.8,9
Apprehension Test – Pain or apprehension indicate a positive test.
Relocation Test – Decreased pain or apprehension indicate a positive test.
Anterior Release Test – Pain or apprehension upon release of the humeral head indicate a positive test.
The two most reliable tests for posterior instability are the posterior stress test and the jerk test.5
Posterior Stress Test (Posterior Apprehension Test) – Pain or apprehension indicates a positive test.
Jerk Test – A clunk, or jerk, upon axial load or horizontal adduction indicates a positive test. Another clunk may also occur upon relocation (horizontal abduction).
VII. Conservative Treatment
If immobilization is the sole treatment, the arm is usually immobilized anywhere from 2 to 6 weeks. Combined with exercise, it will usually be immobilized for a lesser time period. For anterior dislocations, the humerus is normally placed in a traditional internally rotated position. However, new studies are being conducted which may show that placing the humerus in an externally rotated position may be more beneficial for healing especially if a Bankart lesion is present. For posterior dislocations the humerus is normally placed in a slightly extended and externally rotated position.4,5,10
Exercise is normally used in conjunction with immobilization. The shoulder will usually be immobilized for 1-3 weeks. During this time period, wrist and elbow range of motion exercises can be performed so that it is not lost. After immobilization, range of motion of the shoulder can begin followed by strengthening. In the case of anterior dislocation, strengthening programs should emphasize the internal rotators, adductors, scapular muscles. For posterior dislocation, programs to strengthen the external rotators, posterior deltoid, and scapular muscles are performed. Conservative protocols may take up to 3 months for full recovery.4,5,10
click on the link below to view PT management of shoulder dislocation:
VIII. Surgical Treatment
For an anterior dislocation, open or arthroscopic surgeries may be performed. During an open Bankart repair, the subscapularis is detached so that the labrum can be repaired on the anterior glenoid. The shoulder is reduced and sutures are applied to hold it in place. In an arthroscopic procedure, portals are made and the anterior labrum is reattached and the humerus is reduced.
For a posterior dislocation, open surgery or arthroscopic surgery may be performed as well. In an open posteroinferior capsular shift, the humerus is placed in 20 degrees of abduction. The incision is made in the posterior axilla. The humerus is placed back into the capsule and the posterior capsule is repaired. During arthroscopic surgery, three or four portals are used anteriorly and posteriorly. If a reverse Bankart lesion is present it is then repaired with sutures. The humerus is placed back into the capsule and the portals are stitched back up. Both open and arthroscopic surgeries have their advantages and disadvantages. With open surgery there is a lesser rate of redislocation. However, there is usually a greater loss in external rotation than with arthroscopic surgery. Treatment following surgery is basically the same as a conservative protocol consisting of range of motion and strengthening exercises for the shoulder. Depending on the type of surgery, full recovery time may take anywhere from 4 to 9 months.4,5,10
Arthroscopic Bankart Repair Animation
IX. Additional Web-Based Resources
For information all about shoulder dislocations visit: http://www.ori.org.au/bonejoint/shoulder/contents.htm
For an extensive list of special orthopedic tests visit: http://www.shoulderdoc.co.uk/article.asp?section=497.
For treatment protocols visit: http://www.pt.armstrong.edu/davies/pdf/Anterior%20Shoulder%20Dislocation.pdf
1. Seade EL, Josey R. Shoulder Dislocation. Medscape Reference Website. Available at: http://emedicine.medscape.com/article/93323-overview. Accessed October 28th, 2011.
2. Mayo Clinic Staff. Dislocated Shoulder. Mayo Foundation for Medical Education and Research. Available at: http://www.mayoclinic.com/health/dislocated-shoulder/DS00597. Accessed November 26th, 2011.
3. Sizer PS, Phelps V, Gilbert K. Diagnosis and management of the painful shoulder. Part 1: clinical anatomy and pathomechanics. Pain Practice, 2003;3(1):40-57.
4. Hayes K, Callanan M, Walton J, Paxinos A, Murrell G. Shoulder instability: management and rehabilitation. Journal of Orthopaedic & Sports Physical Therapy, 2002;32(10):1-13.
5. Millett PJ, Clavert PC, Hatch RGF, Warner JJP. Recurrent posterior shoulder instability. Journal of the American Academy of Orthopaedic Surgeons, 2006;14(8):464-476.
6. Satterwhite YE. Evaluation and management of recurrent anterior shoulder instability. Journal of Athletic Training, 2000;35(3):273-277.
7. Tseng GY, Peh WCG. Shoulder Dislocation Imaging. Medscape Reference Website. Available at: http://emedicine.medscape.com/article/395520-overview. Accessed November 26, 2011.
8. Hegedus EJ, Goode A, Campbell S, Morin A, Tamaddoni M, Moorman CT, Cook C. Physical examination tests of the shoulder: a systematic review with meta-analysis of individual tests. Journal of Sports Medicine, 2008;42(1):80-92.
9. Farber AJ, Castillo R, Clough M, Bahk M, McFarland EG. Clinical assessment of three common tests for traumatic anterior shoulder instability. Journal of Bone and Joint Surgery, 2006;88(7):1467-1474.
10. Handoll HHG, Al-Maiyah MA. Surgical versus non-surgical treatment for acute anterior shoulder dislocation. The Cochrane Collaboration, 2010;(5):1-34.