Posterior Dislocation of Shoulder: This is a rare pathological condition of the shoulders in which the shoulder gets dislocated posteriorly. Anterior dislocation of the shoulder is quite common but posterior dislocation of the shoulder is pretty rare and usually occurs after a trauma or an epileptic shock. The delayed diagnosis of posterior shoulder dislocation causes difficulties in treatment and results in surgery.1
What Is Posterior Dislocation Of Shoulder?
The shoulder joint is a ball and socket joint. The socket of the shoulder joint is shallow which gives the shoulder increased range of motion than other ball and socket joints in the body but at the same it makes the shoulder joint prone to various injuries. Majority of shoulder dislocations are anterior but in rare cases a posterior dislocation of the shoulder also takes place.
Causes of Posterior Dislocation Of Shoulder
As stated, Posterior Dislocation of Shoulder is a pretty rare phenomenon. It is usually caused due to trauma or impact with the shoulder being held in internal rotation (arm turn inwards) and adduction (arm close to body or chest wall). The injury mostly occurs when an individual suffers from an epileptiform seizure or as a result of an electrocution injury. If an individual develops Posterior Dislocation of the Shoulder of unknown etiology then the possibility of a convulsion needs to be considered. This injury can also occur as a result of a direct trauma in some cases. Improper weight distribution while weight lifting can cause posterior dislocation.2
Types Of Posterior Dislocation Of Shoulder
Partial (25% or Less Separation) Subluxation:
A defect is defined as partial dislocation when 25% of articular surface of head is outside the glenoid cavity.
Medium (25 to 50 % Separation) Dislocation-
A partial subluxation of 25 to 50% separation is also known as medium dislocation.
Total dislocation is complete separation of head of the humerus from glenoid cavity.
Symptoms Of Posterior Dislocation Of Shoulder
Some Of The Symptoms Of Posterior Dislocation Of The Shoulder Are:
- Severe shoulder joint pain is felt at rest and during any attempt to move shoulder joint.
- The arm is in fixed position as being in an adducted and internally rotated position
- Examination suggests presence of a posterior bulge at the back of shoulder joint. The bulge is felt as smooth round swelling caused by protrusion of humeral head beneath the acromial process
- Pain becomes severe with attempt to abduct (move arm away from body) or external rotation of arm (turn arm outward).
- Inability to supinate the arm at elbow joint.
Diagnosis of Posterior Dislocation Of Shoulder
Usually, these dislocations are identified on x-ray views, especially the antero-posterior (AP) and lateral view of shoulder joint.
The AP view may reveal the humeral head as normal shape sitting outside glenoid cavity or may look like bulb as a result of rotation.
The axillary view will reveal the humeral head to be posterior to the glenoid.
X-ray diagnosis is confirmed with MRI or X-Ray films.
Treatment For Posterior Dislocation Of Shoulder
Treatment depends on diagnosis. Posterior Shoulder Dislocation is carefully evaluated. Appropriate treatment of a Posterior Shoulder Dislocation is dependent on the size of defect, the duration of dislocation, the age of the individual, and profession.
Conservative Treatment For Posterior Dislocation of Shoulder-
- Partial dislocation is treated with shoulder braces and arm support until close reduction is performed.
- Arm support is also used following close reduction and surgery.
- Cold therapy like cold pack or ice pack is used to reduce edema and swelling.
- Cold therapy helps to reduce the pain as well as improve partial movement of the arm.
- Severe pain is treated with opioids.
- Opioids are prescribed for 2 to 3 weeks only.
- Pain is severe until dislocation is reduced to normal joint by close reduction of surgery.
- Severe pain last for 7 to 10 days after close reduction and 3 to 4 weeks after open reduction.
- Most common opioids prescribed are hydrocodone (Vicodin and Norco) and oxycodone (Percocet).
- Muscle Relaxants-
Close Reduction Treatment For Posterior Dislocation Of Shoulder
Partial posterior dislocation of shoulder is treated with close reduction. Partial dislocation is managed with following choice of treatment.
- The time passed since the dislocation and the size of humeral head are vital statistics in determining whether a closed reduction can be done.
- If the defect is below 25% of separation of the articular surface resulting in dislocation then closed reduction may be done.
- If history suggest patient had pain and deformity over 3 to 4 weeks then close reduction may not be the choice of treatment.
Surgical Treatment or Open Reduction For Posterior Dislocation of Shoulder-
Indication For Open Reduction-
- Failed close reduction
- Partial dislocation undiagnosed for over 4 weeks.
- Partial dislocation involving over 25% of the articulating surface.
Open Reduction Surgery-
Mild (Less Than 25% To Moderate (25 to 50%) Subluxation or Dislocation-
Deltoid-pectoral approach is preferred type of open reduction surgery.
Total Dislocation-Total dislocation or dislocation of over 50% subluxation is treated with open reduction
- Segmental reconstruction of humeral head4
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1.Acute traumatic posterior shoulder dislocation.
Rouleau DM, Hebert-Davies J, Robinson CM.
J Am Acad Orthop Surg. 2014 Mar;22(3):145-52.
2.Posterior shoulder dislocation while lifting weights: a missed diagnosis.
Cuffolo G1, Coomber R, Burtt S, Gray J.
.BMJ Case Rep. 2014 Feb 20;2014.
3.Anatomic shoulder arthroplasty as treatment for locked posterior dislocation of the shoulder.
Wooten C, Klika B, Schleck CD, Harmsen WS, Sperling JW, Cofield RH.
J Bone Joint Surg Am. 2014 Feb 5;96(3):e19. doi: 10.2106/JBJS.L.01588.
4.Long-term outcome of segmental reconstruction of the humeral head for the treatment of locked posterior dislocation of the shoulder.
Gerber C1, Catanzaro S2, Jundt-Ecker M2, Farshad M2.
J Shoulder Elbow Surg. 2014 Jun 12. pii: S1058-2746(14)00206-7.
5.Functional outcome and quality of life after rehabilitation for voluntary posterior shoulder dislocation: a prospective blinded cohort study.
Merolla G1, De Santis E, Cools AM, Porcellini G.
Eur J Orthop Surg Traumatol. 2014 Jun 3.