Board Review: Oh SNAP!

19-year-old male with past medical history significant for seizures presents with right shoulder pain. He woke up from sleep with the pain. It is 10/10 and worse with movement. He has multiple prior episodes for which he has been treated for in the ED. Vitals are as follows: BP 140/70, HR 115, RR 20, Pulse Ox 92%, Temp 37 C. On exam, patient has diffuse tenderness of the right shoulder. Pain worsens with any range of motion. There is also posterior flattening. Radial pulse if 2+ and sensation over the deltoid is intact. You obtain a stat Xrays which show the following:


What is the appropriate mechanism of reduction of the injury above?


A. Caudal traction with external rotation and abduction

B. Abduction with pronation

C. Caudal traction with internal rotation and adduction

D. Extension with supination




















Answer: C. Caudal traction, internal rotation, and adduction. 2-4% of shoulder dislocations are posterior. It is typically associated with seizures or electrocution. Patients are at high risk of reverse hill-sachs fractures and recurrent dislocations. Extensive ligamentous injuries are often seen. These are commonly missed on plain film. The most common finding on x-ray is the lightbulb sign, which is caused by the humeral head being stuck in internal rotation. Another finding is widening of the glenohumeral joint space. CT may be required to make the diagnosis. Reduction is performed using the Depalma method: placed the arm in adduction and internal rotation while applying caudal traction. Once the patient is in this position lateral traction should be applied to the upper extremity to help lift the humeral head over the posterior lip of the glenohumeral joint. Once reduced the patient should be placed in abduction and external rotation to prevent recurrence. Splint should be worn at all times until orthopedic follow up. Confirm reduction with repeat x-rays. 


Images obtained from:

Cadogan, M. "Posterior Shoulder Dislocation." LIFTL. May 2020. <> July 31, 2020. 


For more information on dislocations check out:





10 ways to reduce a shoulder: 

Mellick, L. "Ten Ways to Reduce a Shoulder." Aug 2015. <>. 7/31/20.