Posterior Shoulder Dislocations
– less common (≤4%)
-may be missed by treating physicians, & diagnosis is delayed in nearly all cases.
– Failure in diagnosis & treatment→ complications: recurrent dislocations, AVN of the humeral head, degenerative disease, & chronic pain.
Diagnosis: by clinical & radiological examinations
-classically in pt. with seizure disorder (external rotators stronger)
-Pain of the shoulder with limited Ext. rotation-00 & forward flexion- <900
-Axillary N. injury may be +nt (less than Ant. Dislocation)
-Reverse Hill-sachs (impaction of anterior humeral head) +nt in 75% cases
–Other association: Reverse Bankart (posterior laberal tears); disruption of posterior band of Inf. Glenohumeral ligament; Teres minor tear ; Posterior Glenoid fracture
X-ray: AP view- Proximal humerus internally rotated: losing the profile of the neck; but may be missed
Scapular Y view- needed in posterior dislocation
Axillary View- to confirm reduction
Other important views- Velpeau view, West point view, Hill-Sachs view, Stryker Notch view
CT: for evaluation of proximal humerus & glenoid
MRI: to evaluate rotator cuff, Bankart lesion, ligamentous/capsular lesions
Classification of Post. Shoulder Dislocation:
-Subacromial (MC)- the articular surface of head posteriorly directed with lesser tubercle in glenoid fossa
-Subglenoid (rare)- the head posterior & inferior to glenoid
-Subspinus (rare)- the head medial to Acromian & inferior to spine of Scapula
Closed reduction (in ER)-usually by “traction-countertraction” method.
– indicated in pt. with uncomplicated posterior shoulder dislocation (diagnosed within 6 weeks), with no defect/defect<20%.
-contraindicated in a) Delayed (>6 weeks) presentation, b) Large humeral head defect, c) Displaced/multipart fracture-dislocations; these cases need Sx.
Open Reduction by Surgery: depends on the extent of the reverse Hill–Sachs lesions, the duration of the dislocation, the condition of the glenoid fossa, & the age & the general health of the patient
Arthroscopic Surgery– posterior capsule imbrication
Open Surgery– 1. Postero-Inferior Capsular Shift (by Bigliani, et al & Fuchs B, et al)
- McLaughlin Technique– a Subscapularis tendon transfer into the defect
- Modified McLaughlin Procedure– for Neglected Locked Posterior Dislocation of the Shoulder
– transfer of lesser tuberosity with its attached Subscapularis tendon into the defect;
– indicated for defects > 20% but < 40% of the joint surface;
-disadvantage- limitation of internal rotation
- Allograft Reconstruction– for pt. >40% defect in the head with recurrent instability
-insertion & fixation of a shaped piece of allograft in the defect.
-advantage: No limitation of internal rotation
- Shoulder Arthroplasty– for defect >50% in which case stability cannot be restored by any other method; but humeral head replacement should be avoided in younger pt. as long as possible