GLENOHUMERAL DISLOCATION

EPIDEMIOLOGY

The shoulder is the most commonly dislocated major joint of the body, accounting for up to 45% of dislocations.

Anterior dislocations account for 96% of cases. Posterior dislocations, the second most common direction of dislocation, account for 2% to 4% of cases.

Inferior (luxatio erecta) and superior shoulder dislocations are rare, accounting for approximately 0.5% of cases.

The incidence of glenohumeral dislocation is 17 per 100,000 population per year.

Incidence peaks for males in the 21 to 30 year age range and for women in the 61 to 80 year age range.

Recurrence rate in all ages is 50% but rises to almost 89% in the 14 to 20 year age group.

ANATOMY (FIG. 14.1)

Glenohumeral stability depends on both passive and active mechanisms, including:

• Passive:

  1. Joint conformity.

  2. Vacuum effect of limited joint volume.

  3. Adhesion and cohesion owing to the presence of synovial fluid.

  4. Scapular inclination: for >90% of shoulders, the critical angle of scapular inclination is between 0 and 30 degrees, below which the glenohumeral joint is considered unstable and prone to inferior dislocation.

  5. Ligamentous and capsular restraints (Fig. 14.2).

     • Joint capsule: Redundancy prevents significant restraint, except at terminal ranges of motion. The anteroinferior capsule limits anterior subluxation of the abducted shoulder. The posterior capsule and teres minor limit internal rotation. The anterior capsule and lower subscapularis restrain abduction and external rotation.

     • Superior glenohumeral ligament: This is the primary restraint to inferior translation of the adducted shoulder.

     • Middle glenohumeral ligament: This is variable, poorly defined, or absent in 30%. It

       limits external rotation at 45 degrees of abduction.

     • Inferior glenohumeral ligament: This consists of three bands, the superior of which is of primary importance to prevent anterior dislocation of the shoulder. It limits external rotation at 45 to 90 degrees of abduction.

     • Coracohumeral ligament: This is a secondary stabilizer to inferior translation.

        

        

        

  6. Glenoid labrum.

  7. Bony restraints: acromion, coracoid, glenoid fossa.

• Active:

  1. Biceps, long-head

  2. Rotator cuff

  3. Scapular stabilizing muscles

Coordinated shoulder motion involves:

1. Glenohumeral motion

2. Scapulothoracic motion

3. Clavicular and sternoclavicular motion

4. Acromioclavicular motion

Pathoanatomy of shoulder dislocations:

• This involves a stretching or tearing of the capsule, usually off the glenoid, but occasionally off the humerus due to avulsion of the glenohumeral ligaments (HAGL lesion).

• Labral damage: A “Bankart” lesion refers to avulsion of anteroinferior labrum off the glenoid

  rim. It may be associated with a glenoid rim fracture (“bony Bankart”). This is found in 40% of shoulders undergoing surgical intervention.

Hill-Sachs lesion: A posterolateral head defect is caused by an impression fracture on the glenoid rim; this is seen in 27% of acute anterior dislocations and 74% of recurrent anterior dislocations (Fig. 14.3).

Shoulder dislocation with associated rotator cuff tear.

• Common in older individuals.

  • >40 years old: 35% to 40%

    • Ultrasound may be considered in patients >40 years old with a first-time dislocation.

  • >60 years old: may be as high as 80%

• Beware of an inability to lift the arm in an older patient following a dislocation.

   

  ANTERIOR GLENOHUMERAL DISLOCATION

  Incidence

Anterior dislocations represent 96% of shoulder dislocations.

Mechanism of Injury

Anterior glenohumeral dislocation may occur as a result of trauma, secondary to either direct or indirect forces.

Indirect trauma to the upper extremity with the shoulder in abduction, extension, and external rotation is the most common mechanism.

Direct, anteriorly directed impact to the posterior shoulder may produce an anterior dislocation.

Convulsive mechanisms and electrical shock typically produce posterior shoulder dislocations, but they may also result in an anterior dislocation.

Recurrent instability related to congenital or acquired laxity or volitional mechanisms may result in anterior dislocation with minimal trauma.

Clinical Evaluation

It is helpful to determine the nature of the trauma, the chronicity of the dislocation, pattern of recurrence with inciting events, and the presence of laxity or a history of instability in the contralateral shoulder.

The patient typically presents with the injured shoulder held in slight abduction and external rotation. The acutely dislocated shoulder is painful, with muscular spasm.

Examination typically reveals squaring of the shoulder owing to a relative prominence of the acromion, a relative hollow beneath the acromion posteriorly and a palpable mass anteriorly.

A careful neurovascular examination is important, with attention to axillary nerve integrity. Deltoid muscle testing is usually not possible, but sensation over the deltoid may be assessed. Deltoid atony may be present and should not be confused with axillary nerve injury. Musculocutaneous nerve integrity can be assessed by the presence of sensation on the anterolateral forearm (Fig. 14.4).

Patients may present after spontaneous reduction or reduction in the field. If the patient is not in acute pain, examination may reveal a positive apprehension test, in which passive placement of the shoulder in the provocative position (abduction, extension, and external rotation) reproduces the patient’s sense of instability and pain (Fig. 14.5).

Radiographic Evaluation

Trauma series of the affected shoulder: Anteroposterior (AP), scapular-Y, and axillary views taken in the plane of the scapula (Figs. 14.6 and 14.7).

• Prereduction radiographs should be considered in all first-time dislocations, patients over age 40 years, and following high-energy trauma as these patients have a higher risk of associated fracture.

   

   

   

   

   

Velpeau axillary: If a standard axillary cannot be obtained because of pain, the patient may be left in a sling and leaned obliquely backward 45 degrees over the cassette. The beam is directed caudally, orthogonal to the cassette, resulting in an axillary view with magnification (Fig. 14.8).‌

Special views:

• West Point axillary: This is taken with patient prone with the beam directed cephalad to the axilla 25 degrees from the horizontal and 25 degrees medial. It provides a tangential view of the anteroinferior glenoid rim (Fig. 14.9).

• Hill-Sachs view: This AP radiograph is taken with the shoulder in maximal internal rotation to visualize a posterolateral defect.

• Stryker notch view: The patient is supine with the ipsilateral palm on the crown of the head

  and the elbow pointing straight upward. The x-ray beam is directed 10 degrees cephalad, aimed at the coracoid. This view can visualize 90% of posterolateral humeral head defects (Fig.

  14.10).

   

   

   

   

Computed tomography may be useful in defining humeral head or glenoid impression fractures, loose bodies, and anterior labral bony injuries (bony Bankart lesion).

Single- or double-contrast arthrography may be utilized to evaluate rotator cuff pathologic processes.

Magnetic resonance imaging may be used to identify rotator cuff, capsular, and glenoid labral (Bankart lesion) pathologic processes.

Classification

Degree of stability: Dislocation versus subluxation

Chronology: Congenital

Acute versus chronic

Locked (fixed) Recurrent

Acquired: generally from repeated minor injuries (swimming, gymnastics, weights); labrum often intact but with capsular laxity; increased glenohumeral joint volume; subluxation common

Force: Atraumatic: usually owing to congenital laxity; no injury; often asymptomatic; self-reducing

Traumatic: usually caused by one major injury; anterior or inferior labrum may be detached (Bankart lesion); unidirectional; generally requires assistance for reduction

Patient contribution: Voluntary versus involuntary

Direction: Subcoracoid Subglenoid Intrathoracic

Treatment

Nonoperative

Closed reduction should be performed after adequate clinical evaluation and administration of analgesics, intra-articular block, and/or sedation. Described techniques include:

• Traction–countertraction (Fig. 14.11)

• Hippocratic technique: This is effective with only one person performing reduction, with one foot placed across the axillary folds and onto the chest wall, with gentle internal and external rotation with axial traction on the affected upper extremity.

• Stimson technique: After administration of analgesics and/or sedatives, the patient is placed prone on the stretcher with the affected upper extremity hanging free. Gentle, manual traction or 5 lb of weight is applied to the wrist, with reduction effected over 15 to 20 minutes (Fig. 14.12).

• Scapular manipulation technique: The patient is placed prone similar to the Stimson technique. Once the patent is relaxed, the inferior tip of the scapula is pushed medial and inferior while the superomedial scapula is held stationary.

• Milch technique: With the patient supine and the upper extremity abducted and externally rotated, thumb pressure is applied by the physician to push the humeral head into place.

• Kocher maneuver: The humeral head levered on the anterior glenoid to effect reduction; this is

  not recommended because of increased risk of fracture.

   

   

   

   

   

Postreduction care includes immobilization for 2 to 5 weeks. A shorter period of immobilization may be used for patients older than 40 years of age because stiffness of the ipsilateral hand, wrist, elbow, and shoulder tends to complicate treatment. Younger patients with a history of recurrent dislocation may require longer periods of immobilization.‌

In comparison to a simple sling, immobilization in a Velpeau dressing does not appear to alter the subsequent development of recurrent instability.

Controversy exists whether immobilization in internal or external rotation can better prevent recurrence of dislocation.

Therapy should be instituted following immobilization, including increasing degrees of shoulder

external rotation, flexion, and abduction as time progresses, accompanied by full, active range of motion to the hand, wrist, and elbow.

Irreducible acute anterior dislocation (rare) is usually the result of interposed soft tissue and requires open reduction.

Operative

Indications for surgery include:

• First-time dislocation in young active men

• Soft tissue interposition

• Displaced greater tuberosity fracture that remains >5 mm superiorly displaced following joint reduction

• Glenoid rim fracture >5 mm in size

Surgery for stabilization typically involves arthroscopic ligamentous repair of the anterior/inferior labrum (Bankart lesion). Procedures such as capsular shift, capsulorrhaphy, muscle or tendon transfers, and bony transfers are reserved for refractory cases.

Postoperative management typically includes the use of a shoulder immobilizer for up to 3 weeks in patients <30 years old, 2 weeks for patients 30 to 40 years, and 1 to 2 weeks for patients >50 years old, depending on the type of surgical stabilization. Patients are allowed to remove the immobilizer two to four times per day for shoulder, wrist, and hand range-of-motion exercises. Therapy is aimed at active and passive range of motion and regaining upper extremity strength.

Complications

Recurrent anterior dislocation: related to ligament and capsular changes.

• The most common complication after dislocation is recurrent dislocation.

• Incidence:

  • Age 20 years: 80% to 92% (lower in nonathletes)

  • Age 30 years: 60%

  • Age 40 years: 10% to 15%

• Most recurrences occur within the first 2 years and tend to occur in men.

• Prognosis is most affected by age at the time of initial dislocation.

• Incidence is unrelated to the type or length of immobilization.

• Patient activity has been identified as an independent factor for developing recurrent instability.

Osseous lesions:

• Hill-Sachs lesion

• Glenoid lip fracture (“bony Bankart lesion”)

• Greater tuberosity fracture

• Fracture of acromion or coracoid

• Posttraumatic degenerative changes

Soft tissue injuries:

Rotator cuff tear (older patients)

Capsular or subscapularis tendon tears

Vascular injuries: These typically occur in elderly patients with atherosclerosis and usually involve the axillary artery. They may occur at the time of open or closed reduction.

Nerve injuries: These involve most commonly the musculocutaneous and axillary nerves, usually in elderly individuals; neurapraxia almost always recovers, but if it persists beyond 3 months, it requires further evaluation with possible exploration.

POSTERIOR GLENOHUMERAL DISLOCATION

Incidence

These injuries represent 2% to 4% of shoulder dislocations and 2% of shoulder injuries.

They are often unrecognized by primary care and emergency physicians, with 60% to 80% missed on initial examination.

Mechanism of Injury

Indirect trauma: This is the most common mechanism.

• The shoulder typically is in the position of adduction, flexion, and internal rotation.

• Electric shock or convulsive mechanisms may produce posterior dislocations owing to the greater muscular force of the internal rotators (latissimus dorsi, pectoralis major, and subscapularis muscles) compared with the external rotators of the shoulder (infraspinatus and teres minor muscles).

Direct trauma: This results from force application to the anterior shoulder, resulting in posterior translation of the humeral head.

Clinical Evaluation

Clinically, a posterior glenohumeral dislocation does not present with striking deformity; the injured upper extremity is typically held in the traditional sling position of shoulder internal rotation and adduction. These injuries may be missed if a complete radiographic series is not obtained.

A careful neurovascular examination is important to rule out axillary nerve injury, although it is much less common than with anterior glenohumeral dislocation.

On examination, limited external rotation (often <0 degrees) and limited anterior forward elevation (often <90 degrees) may be appreciated.

A palpable mass posterior to the shoulder, flattening of the anterior shoulder, and coracoid prominence may be observed.

Radiographic Evaluation

Trauma series of the affected shoulder: AP, scapular-Y, and axillary views. A Velpeau axillary view (see earlier) may be obtained if the patient is unable to position the shoulder for a standard

axillary view.

On a standard AP view of the shoulder, signs suggestive of a posterior glenohumeral dislocation include:

• Absence of the normal elliptic overlap of the humeral head on the glenoid.

• Vacant glenoid sign: The glenoid appears partially vacant (space between anterior rim and humeral head >6 mm).

• Trough sign: impaction fracture of the anterior humeral head caused by the posterior rim of

  glenoid (reverse Hill-Sachs lesion). This is reported to be present in 75% of cases.

• Loss of profile of humeral neck: The humerus is in full internal rotation.

• Void in the superior/inferior glenoid fossa, owing to infero-superior displacement of the dislocated humeral head.

Glenohumeral dislocations are most readily recognized on the axillary view; this view may also

demonstrate the reverse Hill-Sachs defect.

Computed tomography scans are valuable in assessing the percentage of the humeral head involved with an impaction fracture.

Classification

Etiologic Classification

Traumatic: Sprain, subluxation, dislocation, recurrent, fixed (unreduced)

Atraumatic: Voluntary, congenital, acquired (due to repeated microtrauma)

Anatomic Classification

Subacromial (98%): Articular surface directed posteriorly with no gross displacement of the humeral head as in anterior dislocation; lesser tuberosity typically occupies glenoid fossa; often associated with an impaction fracture on the anterior humeral head

Subglenoid (very rare): Humeral head posterior and inferior to the glenoid

Subspinous (very rare): Humeral head medial to the acromion and inferior to the spine of the scapula

Treatment

Nonoperative

Closed reduction requires full muscle relaxation, sedation, and analgesia.

• The pain from an acute, traumatic posterior glenohumeral dislocation is usually greater than with an anterior dislocation and may require general anesthesia for reduction.

• With the patient supine, traction should be applied to the adducted arm in the line of deformity

  with gentle lifting of the humeral head into the glenoid fossa.

• The shoulder should not be forced into external rotation, because this may result in a humeral

  head fracture if an impaction fracture is locked on the posterior glenoid rim.

• If prereduction radiographs demonstrate an impaction fracture locked on the glenoid rim, axial traction should be accompanied by lateral traction on the upper arm to unlock the humeral head.

Postreduction care should consist of a sling and swathe if the shoulder is stable. If the shoulder

subluxes or redislocates in the sling and swathe, one should consider surgical stabilization.

• With a large anteromedial head defect, better stability may be achieved with immobilization in external rotation.

• External rotation and deltoid isometric exercises may be performed during the period of

  immobilization.

• After discontinuation of immobilization, an aggressive internal and external rotator strengthening program is instituted.

  Operative

Indications for surgery include:

• Major displacement of an associated lesser tuberosity fracture

• A large posterior glenoid fragment

• Irreducible dislocation or an impaction fracture on the posterior glenoid preventing reduction

• Open dislocation

• An anteromedial humeral impaction fracture (reverse Hill-Sachs lesion)

• Twenty percent to 40% humeral head involvement: transfer the lesser tuberosity with attached subscapularis into the defect (modified McLaughlin procedure)

• Greater than 40% humeral head involvement: hemiarthroplasty with neutral version of the

  prosthesis

• Recurrent instability

Surgical options include open reduction, infraspinatus muscle/tendon plication (reverse Putti-Platt procedure), long head of the biceps tendon transfer to the posterior glenoid margin (Boyd-Sisk procedure), humeral and glenoid osteotomies, and capsulorrhaphy.

Voluntary dislocators should be treated nonoperatively, with counseling and strengthening exercises.

Complications

Fractures: These include fractures of the posterior glenoid rim, humeral shaft, lesser and greater tuberosities, and humeral head.

Recurrent dislocation: The incidence is increased with atraumatic posterior glenohumeral dislocations, large anteromedial humeral head defects resulting from impaction fractures on the glenoid rim, and large posterior glenoid rim fractures. They may require surgical stabilization to prevent recurrence.

Neurovascular injury: This is much less common in posterior versus anterior dislocation, but it may include injury to the axillary nerve as it exits the quadrangular space or to the nerve to the

infraspinatus (branch of the suprascapular nerve) as it traverses the spinoglenoid notch.

Anterior subluxation: This may result from “overtightening” posterior structures, forcing the humeral head anteriorly. It may cause limited flexion, adduction, and internal rotation.

INFERIOR GLENOHUMERAL DISLOCATION (LUXATIO ERECTA)

This very rare injury is more common in elderly individuals.

Mechanism of Injury (Fig. 14.13)

It results from a hyperabduction force causing impingement of the neck of the humerus on the acromion, which levers the humeral head out inferiorly.

The superior aspect of articular surface is directed inferiorly and is not in contact with the inferior glenoid rim. The humeral shaft is directed superiorly.

Rotator cuff avulsion and tear, pectoralis injury, proximal humeral fracture, and injury to the axillary artery or brachial plexus are common.

Clinical Evaluation

Patients typically present in a characteristic “salute” fashion, with the humerus locked in 110 to 160 degrees of abduction and forward elevation. Pain is usually severe.

The humeral head is typically palpable on the lateral chest wall and axilla.

A careful neurovascular examination is essential, because neurovascular compromise almost always complicates these dislocations.

Radiographic Evaluation

Trauma series of the affected shoulder: AP, scapular-Y, and axillary views are taken.

The AP radiograph is typically diagnostic, with inferior dislocation of the humeral head and superior direction of the humeral shaft along the glenoid margin.

The radiograph must be carefully scrutinized for associated fractures, which are common and may be clinically not detected because of a diffusely painful shoulder.

Treatment

Nonoperative

Reduction may be accomplished by the use of traction-countertraction maneuvers.

Axial traction should be performed in line with the humeral position (superolaterally), with a gradual decrease in shoulder abduction. Countertraction should be applied with a sheet around the patient, in line with, but opposite to the traction vector.

The arm should be immobilized in a sling for 3 to 6 weeks, depending on the age of the patient. Older individuals may be immobilized for shorter periods to minimize shoulder stiffness.

Operative

Occasionally, the dislocated humeral head “buttonholes” through the inferior capsule and soft tissue envelope, preventing closed reduction. Open reduction is then indicated with enlarging of the capsular defect and repair of the damaged structures.

Complications

Neurovascular compromise: This complicates nearly all cases of inferior glenohumeral dislocation, but it usually recovers following reduction.

SUPERIOR GLENOHUMERAL DISLOCATION

This very rare injury is less common than inferior glenohumeral dislocation.

Mechanism of Injury

Extreme anterior and superior directed force applied to the adducted upper extremity, such as a fall from a height onto the upper extremity, forces the humeral head superiorly from the glenoid fossa.

It is associated with fractures of the acromion, clavicle, coracoid, and humeral tuberosities, as well as injury to the acromioclavicular joint.

Typically, it is accompanied by soft tissue injury to the rotator cuff, glenohumeral capsule, biceps tendon, and surrounding musculature.

Clinical Evaluation

The patient typically presents with a foreshortened upper extremity held in adduction.

Clinical examination typically reveals a palpable humeral head above the level of the acromion.

Neurovascular injuries are common and must be ruled out.

Radiographic Evaluation

Trauma series of the affected shoulder: AP, scapular-Y, and axillary views are obtained.

The AP radiograph is typically diagnostic, with dislocation of the humeral head superior to the

acromion process.

The radiograph must be carefully scrutinized for associated fractures, which are common and may be clinically not detected because of a diffusely painful shoulder.

Treatment

Closed reduction should be attempted with the use of analgesics and sedatives.

Axial traction with countertraction may be applied in an inferior direction, with lateral traction applied to the upper arm to facilitate reduction.

As with inferior dislocations, soft tissue injury and associated fractures are common; irreducible dislocations may require open reduction.

Complications

Neurovascular complications are usually present and typically represent traction injuries that resolve with reduction.