Anterior shoulder dislocation

Aetiology:

This is a common traumatic sports injury. It can result from either direct trauma to the humeral head or indirect trauma, with the arm being forced into excessive abduction and external rotation. It may occur without trauma and with a sudden wrenching movement e.g. over throwing, or missing a punch in boxing.

Recurrence of dislocation:

Younger patients have a higher content of ‘stretchy’ type III collagen in tendons and ligaments. With each passing decade collagen-producing cells progressively convert to synthesizing type I collagen, which is insoluble and more stable. The recurrence rate after conservative treatment of acute dislocations depends on age:

  • <10 is 100%
  • 10-20 is 94%
  • 20-30 is 79%
  • 30-40 is 50%
  • >40 is 10-15%

Treatment:

Kocher’s method to relocate- Reduce with traction, initial external rotation to 90°, and then internal rotation and adduction, obtain post-reduction films. This is said to be a traumatic manoeuvre which can potentially further damage the joint.

Associated injuries:

  • Bankart lesions (anterior labral and periosteum tears) occur in up to 95% of acute dislocations.
  • The glenohumeral ligaments may be stretched or the IGHL may be detached from the glenoid. The weak point for IGHL disruption in young patient is the glenoid attachment while in the older patient it is the capsule.
  • HAGL’s occur in 9-39% of cases. The incidence of a HAGL lesion is ↑ed if there is a traumatic dislocation, first time dislocation and/or no Bankart lesion.
  • Signs that are suggestive on plain x-ray of a HAGL lesion include: Hill-Sachs lesion; a scalloped medial neck; and bone fragments. MRI should show a ruptured inferior pouch with a free edge of the inferior capsule.
  • ALPSA lesions are ‘anterior labral periosteal sleeve avulsions’ where the IGHL, labrum and periosteum are stripped medially down to the neck of the scapula.
  • Perthes lesion is an undisplaced tear of the anterior labrum with an intact periosteum.
  • Rotator cuff tears are much more common in older patients.
  • Hill-Sachs lesion is a compression # of the humeral head posteriorly and occurs in >80% of traumatic instability cases. Large humeral defects may need an osteochondral graft or infraspinatus transfer. Lesions involving>30% of the proximal humeral head play a role in recurrent instability.
  • Occasionally there may be an associated SLAP tear.
  • Greater tuberosity #’s may be a complication of shoulder dislocation, but should reduce adequately with reduction of the shoulder.
  • GLAD (Glenolabral articular disruption) is an impaction injury in the ABER position causing damage to the chondral surface. The labrum is intact and the shoulder is stable. These patients have pain rather than instability, and may be treated with arthroscopic debridement.

History/Examination:

Acute trauma, sudden pain and may have a feeling of popping out. Look for associated axillary nerve palsy (axillary neuropraxia occurs in 5-35%). Look for a prominent humeral head and hollowing beneath the acromion and check the peripheral pulses.

Chronic dislocators may describe posterior arm pain or a ‘dead’ arm. There may be posterior capsular tightness or a redundant anterior capsule due to recurrent dislocation.

Surgical treatment:

Important issues include age, subsequent demands, activity, and pre-injury status (e.g. throwers may lose ER with operative intervention and capsular tightening, whereas footballers may not be as concerned about this.

Potentially all first time dislocations should be managed operatively to prevent the extremely high recurrence rate.

Early surgical opinion for acute:

  • associated bony Bankart lesion or labral Bankart tear
  • associated rotator cuff tear
  • SLAP tear
  • elite athlete or overhead manual worker
  • large HAGL lesion
  • Hill Sachs lesion >30% articular surface

Arthroscopic procedure

Select patients do well with this approach: no bony lesion or HAGL and an intact capsule. Arthroscopic techniques for reattaching the labrum can be divided into 3 categories: (1) a transglenoid suture technique (2) arthroscopically delivered and tied suture anchors and (3) arthroscopically delivered biodegradable tacs.

Advantages include that the joint is visualized, subscapularis is not affected, there is ↓ loss ROM (particularly ER) and ↓ scar. At present however, open operations seem to have slightly better outcomes than arthroscopic ones.