A 25-year-old male patient presents with chronic left shoulder pain. The patient reports that he initially hurt the shoulder in a motor vehicle accident when age 16. Since the age of 21, the patient has felt sudden and catching pain in the shoulder with activity, especially overhead activity, and occasional popping sounds.
Given this brief history, what would be a reasonable working hypothesis at this stage?
The best working hypothesis at this point would be shoulder instability secondary to past history of shoulder dislocation.
Describe the passive and active stabilizing mechanisms for the glenohumeral joint.
The passive stabilizing mechanisms include the concavity of the glenoid and labrum, finite joint volume, and surface tension provided by joint fluid; the active stabilizing mechanisms include the various shoulder muscles.
How do the size, shape, and tilt of the glenoid fossa affect glenohumeral joint stability?
The glenoid faces anteriorly at an angle of about 45 degrees to the coronal plane. Its depth is enhanced by contributions of the articular cartilage and glenoid labrum.
What is the most common direction and the most common mechanism of injury causing shoulder instability?
The most common direction is anterior -- the intrinsic instability of the shoulder is increased when shoulder abduction is superimposed on external rotation and extension, which commonly occurs when falling backward.
What are the four kinds of anterior dislocation?
The four kinds of anterior dislocation are subcoracoid, subglenoid, subclavicular, and intrathoracic.
What are the three kinds of posterior dislocation?
The three kinds of posterior dislocations are subacromial, subglenoid, and subspinous.
Which, vascular, tendinous, or skeletal structures are the most vulnerable with an anterior shoulder dislocation?
The structures that are the most vulnerable with an anterior shoulder dislocation include bone (compression fractures of the humeral head), rotator cuff (tears), blood vessels (injury may occur in the axillary artery, vein, or the branches of the axillary artery), nerves (the axillary nerve).
What is the typical mechanism and clinical presentation for a posterior dislocation, and how is it managed?
A posterior dislocation most commonly occurs from a direct blow to the front of the shoulder or from a fall onto an outstretched upper extremity.
What is meant by the acronym TUBS when describing shoulder instability?
The acronym TUBS is an abbreviation for traumatic, unidirectional instability with Bankart lesion requiring surgery.