Anterior shoulder dislocations are very common and we all have our favorite ways to reduce them. I’ve noticed lately, however, that many residents don’t know what complications to look out for and what to do if they find them. The Hill-Sachs deformity and Bankart lesion are the most common dislocation complications, with axillary nerve injury being the most discussed complication of reduction.
So what are Hill-Sachs and Bankart lesions and why do we care? The Hill-Sachs deformity is an “indentation fracture” of the posterolateral aspect (important for in-service exam/boards) of the humeral head that occurs during an anterior shoulder dislocation. It occurs because the base of the humeral head is relatively soft compared to the hard anterior glenoid. This occurs in 35-40% of all anterior dislocations and in about 80% of chronic dislocations. These fractures are clinically important, as they predispose the patient to having more dislocations in the future. Ensure the patient has appropriate follow-up with orthopedics, but more importantly make sure you look at all of your own X-Rays to look for this on every dislocation (if you got an X-Ray – you don’t always need to). Fractures less than 20% of the surface area of the humeral head are usually managed non-operatively.
I also hear a lot of people talk about Bankart lesions but they get confused by the word bony being added to it. Basically, a Bankart lesion occurs when the glenoid labrum is interrupted during an anterior shoulder dislocation. If no bone was avulsed then it is a soft Bankart. If bone was avulsed, this is now a “bony Bankart”. Soft Bankarts occur very commonly in young patients with anterior shoulder dislocations, but the bony Bankart occurs in only 5% of cases. If approximately 20% or more of surface area of the inferior glenoid is involved in the fracture, then urgent orthopedic referral is indicated.
Nerve and vascular injuries during reduction of anterior shoulder dislocations are relatively rare, but in Emergency Medicine we must pick up all of these complications to ensure the patient does not have long-term morbidity. The most commonly discussed complication on test questions is the injured axillary nerve. This is more common in the elderly and possibly more common with reduction techniques involving traction on an abducted arm. The axillary nerve innervates the deltoid, teres minor, and the skin on the lateral shoulder. The axillary nerve runs inferiorly to the humeral head and wraps around the surgical neck of the humerus. Many people have said that testing sensation of the axillary nerve over the lateral shoulder is sufficient for ensuring an intact axillary nerve, but according to Wheeless’ Textbook of Orthopedics, this is incorrect. They claim that in an anterior dislocation the innervation to the skin over the lateral shoulder will be intact, and you must instead test for abduction after reduction.
Only 200 cases of axillary artery injuries have been reported, but they are almost all in the elderly population. Ensure you check vascular status after reduction. Young patients usually don’t have rotator cuff tears with the dislocation or reduction, but half of patients over 40 may have at least a partial tear. Just for a quick reminder, the muscles of the rotator cuff are the subscapularis, supraspinatus, infraspinatus, and teres minor. Whenever you reduce an anterior shoulder dislocation, make sure you perform a good neurovascular exam before and after the reduction and document well. If you choose to get plain films, make sure you look for the Hill-Sachs and Bankart, as more prompt orthopedic follow-up may be warranted.
Wheeless’ Textbook of Orthopaedics. Wheelessonline.com. From Duke Orthopaedics.
Sherman S. Shoulder dislocation and reduction. Uptodate.com. Updated Oct 3, 2012.