Shoulder Dislocation

Definition: Separation of the humerus from the scapula at the glenohumeral joint

Epidemiology:

• Most commonly dislocated joint in the body  (17/100,000 people/year)
• Young males most commonly injured

Classification:

• Anterior: 97% (Rowe 1956)
• Posterior: < 3%
• Inferior: < 1% (Also known as: Luxatio Erecta Humeri)
• IMAGE: www.newhealthadvisor.com

Mechanism:

• Anatomy
  • Inherently unstable joint, relies on soft tissues for stabilization
  • Only 25-30% of humeral head articulates with glenoid at any one time
  • Axillary nerve wraps around surgical neck of humerus, most commonly injured nerve in dislocations of any direction
    • Motor: Deltoid muscle
    • Sensory: Anterolateral shoulder
• Anterior:
  • Fall onto outstretched hand
  • Force/blow to abducted and externally rotated +/- extended arm (ie. Blocking basketball shot)
• Posterior:
  • ~50% secondary to trauma (Matsen 2007)
  • 34% associated with seizures (Rouleau 2012)
    • Strongest shoulder muscles (latissimus dorsi, pectoralis major, subscapularis) overpower others and pull shoulder internally, posteriorly
    • Most common dislocation during seizures is anterior due to associated fall
• Inferior:
  • Very high energy injuries. Hyperabduction force levers arm on acromion forcing the humeral head into the infraglenoid region
  • Concomitant injury rate (humerus fracture, rotator cuff tears) as high as 80% (Groh 2010)
  • Concomitant neurologic injury as high as 60% (Groh 2010)

Physical Examination:

• Anterior
  • Arm is held in internally rotated and abducted position
  • Shoulder silhouette flattened with a prominent acromion

Netter’s Concise Orthopaedic Anatomy, Second Edition

• Posterior
  • Arm is fixed, internally rotated, and adducted
  • Posterior shoulder prominence
• Inferior
  • Fixed, abducted position 
  • Arm held above the head

X-Ray Imaging (All Images in Gallery Below):

• For any suspected dislocation, obtain 3 views: AP, Scapula Y, and Axillary (see Approach to Traumatic Shoulder Pain for normal X-ray anatomy)
• Anterior Dislocation
  • AP View: Humeral head dislocated anteriorly and rests under the coracoid process
  • Scapula Y View: Scapula Y view: humeral head displaced medially (to the right) of the scapula
  • Axillary view: Humeral head displaced anteriorly in front of the coracoid process
• Posterior Dislocation
  • AP: “Light bulb on a stick” – often the only sign of a posterior dislocation. The humeral head does not appear displaced from the glenoid BUT it is internally rotated and thus the contour of the humeral head appears rounded – like a light bulb
  • Scapula Y: Humeral head displaced laterally (to the left) of the scapula
  • Axillary: Humeral head displaced posteriorly behind the coracoid process
• Inferior Dislocation
  • Luxatio Erecta: Humeral head displaced inferior to glenoid and arm/humerus fixed above head/superiorly

Important Additional X-Ray Findings

• Hill Sachs Lesion
  • Impaction fracture of humeral head against glenoid rim
  • Anterior dislocations,
    • Occurs against posterolateral surface
    • Incidence rate 40-90%
    • As high as 100% in recurrent dislocations (Provencher 2012)
  • Posterior dislocations
    • Occurs against anterolateral surface (“reverse Hill Sachs lesion”)
    • Incidence 86%.
  • May require accentuating rotational force (internal vs external) when reducing dislocation to dislodge the lesion off glenoid rim

• Bankart Lesion
  • Detachment of anterior inferior labrum from glenoid
  • “Soft” – Labrum only
  • “Bony” – impaction fracture involving glenoid margin

Management/Reduction Techniques

• Provide adequate analgesia
  • The more the patient tenses his or her muscles from pain, the more difficult it will be to reduce the joint
  • Consider systemic analgesia vs intraarticular local anesthetics vs both
  • Procedural sedation may be required in select cases
• Complete a full neurologic and vascular assessment prior to the performance of any manipulation technique
• Anterior
  • Cunningham Technique
    • Physician massages the patient’s biceps muscle as the patient holds arm adducted and elbow flexed
    • Patient gradually moves shoulders up and back (shoulder shrug) as tolerated

https://www.youtube.com/watch?v=MkdCGV_MOCM

• Stimson Maneuver

• Scapular Manipulation
  • Stimson technique applied
  • Scapula manipulated counterclockwise: stabilized superiorly, medial force applied on inferior angle

• Traction-Countertraction
  • Gradual, smooth traction is applied to the affected arm until patient’s muscles relax or tire sufficiently to release the dislocated humeral head
  • An assistant maintains counter traction to maintain patient in place

• Milch

• Posterior: requires 2 operators
  • Traction-Countertraction recommended for all posterior dislocations
  • Sitting patient upright and applying forward traction might be useful
• Inferior
  • Arm traction superiorly with gradual shoulder adduction 
  • Sheet wrapped around upper torso to hold patient in place
  • Traction-Countertraction
  • Two-Step (Youm 2014)
    • Arm traction superiorly while pushing humerus laterally
    • This will either reduce the shoulder entirely or convert it to anterior dislocation, which can be reduced as above

Relative Contraindications to ED Reduction:

• Associated fracture of humeral neck
• Associated nerve injury/deficit
• Suspected major vascular injury
• Chronic Dislocation
  • > 48 hours
  • Success rate exceedingly low
  • Refer to orthopedics for surgical evaluation if initial attempts fail

Follow Up

• Immobilize in sling for 3-4 weeks (older patients 1-2 weeks to avoid joint stiffening)
• Rehab should begin with passive range of motion exercises
• Anterior dislocations: no external rotation past neutral and no abduction past 90 degrees for the first 4-6 weeks
• Posterior dislocations: no internal rotation for first 4-6 weeks.

Take Home Points:

• Be vigilant for concomitant neurovascular injuries and always perform a full neurovascular assessment before and after reduction
• Carefully review radiographs for posterior dislocations as they may appear “normal” on first glance
• Be comfortable with multiple reduction techniques. No one approach will reduce all shoulder dislocations.
• Joint injections and systemic analgesia will facilitate reduction. Depending on patient response to initial attempts, procedural sedation may be necessary.

Read More:

LITFL: Posterior Shoulder Dislocation

LITFL: Cunningham’s Shoulder Relocation

EM Sandbox: The Cunningham Technique – Deep Dive Swaminathan

References

Youm T et al. Acute Management of Shoulder Dislocations. J Am Acad Orthop Surg. 2014 Dec;22(12):761-771.PMID: 25425611.

Rowe CR: Prognosis in dislocations of the shoulder. J Bone Joint Surg Am 1956; 38(5):957-977 PMID 13367074

Matsen FA et al. Principles for the evaluation and management of shoulder instability. Instr Course Lect 2007; 56:23-34. PMID: 17472289

Rouleau DM et al. Incident of associated injury in posterior shoulder dislocation: Systematic review of the literature. J Orthop Trauma 2012 ;26(4):246-251. PMID: 22183196

Robinson CM, Aderinto J. Posterior shoulder dislocations and fracture- dislocations. J Bone Joint Surg Am 2005; 87 (3):639-650. PMID: 15741636

Patel DN et al. Luxatio erecta: Case series with review of diagnostic and management principles. Am J Orthop 2011;40(11): 566-570. PMID: 22263209

Groh GI et al. Results of treatment of luxatio erecta (inferior shoulder dislocation). J Shoulder Elbow Surg 2010;19(3):423-426. PMID: 19836975

Provencher MT et al. The Hill-Sachs lesion: Diagnosis, classification, and management. J Am Acad Orthop Surg 2012;20(4):242-252. PMID: 22474094

Schwartz D. Emergency Radiology Case Studies. Upper Extremity: Patient 6. 271-279. McGraw-Hill Education / Medical; 1 edition (November 26, 2007)

Thompson J, Netter F, Machado C. Netter’s Concise Orthopaedic Anatomy. Second edition. Saunders Elsevier 2010.