Shoulder Dislocations 101

The shoulder is the #1 dislocated joint in the body. I would wage that nearly everyone either knows someone who’s experienced one or will at some point in their medical career assist in their reduction. Ahhh that ‘clunk’ is so satisfying! So might as well learn a few things before helping, right? The goal is to facilitate key points about these dislocations from which are most common, sensitive tests for diagnosing and a few radiographic tips too. (This tutorial will NOT cover ‘how to reduce’ since most sites uses slightly modified techniques and attempting to perform a non-preferred maneuver puts the patient, yourself and the hospital at risk.)

A couple of quick pointers:

  • Look at the patient. The dead give away most of the time is the position the patient is holding their arm. This provides maximal comfort while maintaining the shoulder in dislocation, so any movements opposite these will cause significant discomfort. Notice specifically how the hand is positioned (turned in/out), how the humorous is angled (in/out) or if there’s a visible gap between the arm and the torso.
  • Get that Image! There was one instance I’ll never forget when I assumed the patient had a simple shoulder dislocation only to have my jaw drop when the X-ray returned with a transverse fracture of the humorous. Don’t be the person that attempts to manipulate a fractured arm and lacerates an artery/nerve in the process. Image first, treat second.
  • Pain does not equal dislocation. Related to the last point, shoulder dislocations affect people differently. Some will walk into the ED simply because their arm is not moving appropriately or appears asymmetric. Others will be brought in by ambulance writhing in pain. Your thorough patient history, clinical exam and xrays will provide everything you need for an accurate diagnosis.
  • Check nerves and blood. Dislocations mean a bone isn’t where its intended to be and it’s potentially compressing adjacent soft tissues (ligaments, nerves, arteries, etc.). Check the shoulder cap quickly for sensation (axillary nerve), palpate for the radial pulse, check capillary refill and have the patient give you a quick OK, thumbs up and crossed fingers (radial, median and ulnar nerves). You want to document all finding pre-treatment and compare them following reduction for any changes. If you don’t check and the patient can’t feel their pinky after reduction who’s to say (aka which lawyer) that you didn’t cause that?
  • Conceptualize the injury: A dislocation refers the position the proximal bony structure is at in relation to its joint (in this case the glenohumoral). So if the humoral head is in front of the GH joint, it’s an anterior dislocation. Simple right? However, realize that the arm itself is frequently in the OPPOSITE direction. An anterior dislocation requires the arm to be BEHIND the patient in order to push the humeral head FORWARD. See how that works? Let that sink in for a second while you watch this quick video:

Anterior Dislocation

  • 95% of cases
  • Occurs when arm is positioned away from the body (often overhead) while rotated backwards
    • examples: blocking a basketball shot or fall on an outstretched arm
    • Posterior arm – anterior dislocation
  • Ruled out if patient can touch opposite shoulder
    • Think about it, this movement requires the shoulder to move in the exact opposite direction of its dislocation. The dislocation occurred via abduction, extension, external rotation –> touching the opposite shoulder requires adduction, flexion, internal rotation. If you can perform this simple maneuver then it’s almost impossible for there to be an anterior dislocation and you need to look for another explanation.
  • Treatment: immediate reduction
  • Patient unable to lift the arm after reduction?
    • Younger – Axillary nerve palsy
    • Elderly – Rotator cuff tear

Posterior Dislocations

  • 5% cases
  • Associated with seizures/electrical shock
    • If you image someone convulsing, their arms are in front violently shaking combined with muscular contractions force the humeral head behind the glenohumeral socket.
    • Also associated with direct anterior blows to the shoulder
    • Anterior arm – posterior dislocation
  • Diagnostic sign: arm locked into internal rotation
  • Missed 50% radiographically

Inferior Dislocations

  • Hyperabduction
    • example: Patient falling & grabs object above head
    • Diagnostic sign: holds arm above head, unable to adduct
    • 80% have greater tuberosity fracture or rotator cuff tear
    • 60% have axillary nerve injury
    • Treatment: immediate reduction
  • Deltoid muscle atrophy
    • The deltoid is the primary shoulder muscle holding the glenohumeral joint together. If this muscle weakens (injury, disuse, musculoskeletal disease, etc.), the dead-weight of the arm + gravity + minor traction injury provides enough force to dislocate the joint.
    • Treatment: physical therapy and/or electrical stimulation

Hope that helped a few! Good luck!

Image Credit: [1]

Clinical Reference: UpToDate

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