Shoulder Resources

Shoulder dislocation and instability (R)(M) Shoulder dislocation and instability (R)(M)


Epidemiology
Anterior shoulder dislocation is the commonest dislocation in the body, and makes up 95% of shoulder dislocations.
It occurs in around 2% of individuals at some stage.
Dislocation is more common in the dominant limb.
In young people it is much more common in males. By the 6 th to the 7 th decade it is more common in females.
Instability is bilateral in around 15%.

Conceptualizing instability
Two acronyms are used to think about shoulder instability:
• TUBS: traumatic unidirectional dislocations with a Bankart lesion, often require surgery.
• AMBRI: Atraumatic multidirectional bilateral shoulder instability, often responds to rehabilitation and occasionally inferior capsular shift may be required.

Anatomy and stability
The shoulder has more movement than any other joint, at the expense of stability.

Bony factors
• Glenoid
• Shallow cup, deepened by glenoid labrum, 35mm by 25mm.
• Has superior tilt of 5 degrees, helping to control inferior instability.
• Has a retroversion with respect to the body of the scapula of 7 degrees.
• Cartilage is thicker peripherally, deepening socket.
• Humeral head
• Surface has three times the articular cartilage of the glenoid, with only 25 to 30% of the humeral head cartilage articulating at any time with the glenoid.
• Cartilage is thicker centrally.
• The radius of curvature of the head and glenoid are normally within 2mm.
• Labrum
• The labral attachment in the anterior superior quadrant is variable, but any detachment below the glenoid equator is believed to be pathological.

Ligamentous factors
The ligaments act as check reins and are most important at the extremes of movement. They do not act during mid range activities.
• Superior glenohumeral ligament – extends from the anterosuperior edge of the glenoid, near the origin of LHB, runs to top of lesser tuberosity of the humerus.
• Primarily resists downward movement and external rotation of the humerus with the arm adducted
• Middle glenohumeral ligament – originates from the supraglenoid tubercle, superior labrum or glenoid neck. Runs to the inferior half of the lesser tuberosity.
• Resists anterior translation with the arm abducted to 45 degrees
• Most variable of the ligaments; is poorly defined or absent in 40% of population
• Inferior glenohumeral ligament
• Has two bands (thicker anterior and thinner posterior) separated by an axillary pouch
• The anterior band resists forwards translation with the arm abducted
• The posterior band is a posterior stabilizer with the arm flexed and internally rotated
• Most important ligament complex for GH stability
• Coracohumeral ligament – runs from the horizontal arm of the coracoid to the transverse humeral ligament.
• Acts in concert with superior glenohumeral ligament
• Joint capsule
• Reinforced anteriorly by the glenohumeral ligaments
• Weaker posteriorly

Muscular factors
The rotator cuff and long head of biceps are vital for dynamic stability.

Other factors
Concavity compression
Negative intra-articular pressure.
Adhesion/cohesion of joint fluid (this is not seen in shoulder replacement).
These are most important during mid range activities.
Anterior shoulder dislocation

Aetiology
Usually follows a fall onto the upper limb where the humerus is flexed, abducted and externally rotated.

Pathology
Detachment of the anterior labrum and anterior rim of the glenoid – Bankart lesion.
Indentation on postero-lateral aspect of humeral head – Hill-Sachs lesion
Stretching of inferior glenohumeral ligaments.
There is further damage to the soft tissues with each dislocation.

Clinical
In an acute dislocation the patient has typically fallen onto the arm in a flexed, abducted and ER position, then had it reduced and immobilized. A traumatic dislocation will not usually spontaneously reduce.
Ask about the positions that produce the patient's symptoms:
• If overhead, abducted, externally rotated, think anterior instability
• If on late cocking when pitching, think anterior instability
• If flexed, adducted, internally rotated, think posterior instability
• If on pushing open heavy door, think posterior instability
• If on follow-through in a throw, think posterior instability
• If on carrying a heavy suitcase, think inferior instability
In recurrent dislocation, there may be a catching sensation, followed by numbness or weakness (dead arm syndrome) whenever the arm is used in an overhead position, e.g. when serving in tennis. When the arm is in a neutral position it usually doesn't have any symptoms.
The most consistent functional impairment is the inability to throw a ball overhead.
The apprehension relocation test should be positive.
Remember to always test for ligamentous laxity .

Imaging

Plain XR
If possible, films documenting an initial dislocation should be obtained.
Typical position of the humeral head on the AP is inferior to the coracoid.
A Hill-Sachs lesion will be best demonstrated on an AP with internal rotation; another way of visualizing the Hill Sachs lesion is with the Stryker notch view. This is taken with the hand resting on the head, the patient lying on the table and the AP beam directed 10 degrees cephalad.
Duckworth prefers an apical oblique view, to show a bony Bankart lesion or a Hill-Sachs lesion.
Note that a Hill Sachs lesion occurs in 38%-90% of patients with a primary glenohumeral dislocation. Patients with a Hill-Sachs lesion have an 82% chance of redislocation, whereas patients without a Hill Sachs lesion have only a 50% chance of redislocation.
CT arthrogram or MRI will reveal an associated cuff tear. Labral tears occur in 56% of patients with anterior dislocation.
Duckworth gets an MRI:
• If there is no XR evidence of a dislocation, e.g. Bankart lesion, or documented dislocation
• If the story doesn't add up
EUA
This can be particularly useful in the heavily muscled athlete who can't relax properly.
The anterior and posterior drawer signs are often one grade higher when the patient is anaesthetized.
Arthroscopy
This can allow examination of the labrum and the undersurface of the cuff and can be combined with EUA.

Complications

Rotator cuff tear
Occurs in more than 40% of patients over 40 and more than 80% of patients over 60.

Nerve palsies
Axillary nerve palsies occur in more than 35%.
The risk of an axillary nerve palsy increases with age, duration of dislocation, and force of trauma.
Axillary nerve lesions have a good prognosis for complete recovery.

Treatment

Reduction
All maneuvers should be gentle, with good levels of sedation and muscle relaxation. Miller et al showed (JBJSA 2002) that intra-articular lignocaine (20mL) was safe, effective and patients left hospital much quicker than with intravenous sedation for reduction. Patient monitoring wasn't required.

Kocher maneuver
• Progressive ER then rapid adduction and internal rotation
• Associated with iatrogenic fracture
• Not recommended

Spaso technique
• The patient is supine. The arm is pulled vertically up to provide traction, then externally rotated slightly to reduce
• If the pec major starts to spasm at any time back off on traction

Stimson technique
The patient is placed prone on the bed with 10lb of weight hanging from the arm. Reduction takes around 10 minutes.

Immobilization in sling

Position of immobilization
Usual position is in adduction and internal rotation.
JBJS May 2001: Itoi et al used MRI to show that holding the arm in external rotation actually resulted in better coaptation of the Bankart lesion than holding in internal rotation. They placed arms in 29 degrees of internal rotation and 35 degrees of external rotation to demonstrate this. In internal rotation the anterior portion of the labrum shifts medially and the anterior structures are lax.
A follow up letter commented that MRI of a posterior dislocation showed better coaptation of the ligaments with the arm internally rotated.
Length of immobilization: OKU 7 says that length of immobilization has not been shown to correlate with results. In patients under 22 the incidence of shoulder instability is virtually unaffected by the length of immobilization. Hovelius found in a prospective study that there was no difference in the rate of recurrence of instability between patients slinged for 3 weeks vs. those allowed early use of the arm. One regime is to place in a sling for 3 weeks, starting isometric exercises immediately, then moving onto isotonic exercises. Patients older than 30 may be placed in a sling for only a week to try to avoid stiffness.
Physiotherapy
The rotator cuff, deltoid and scapular muscles are strengthened, and range of motion exercises are started after 6 weeks. The patient is allowed to return to sport when he has a full range of motion, and strength equal to the other side, after at least a three month healing period.
Patients with posterior instability tend to do better with nonoperative methods than patients with anterior instability.

Operative treatment
Can be open or arthroscopic. OKU 7 says open procedure have a lower recurrence rate. Arthroscopic procedures have used staples in the past, with considerable morbidity as the staples migrated, often into the joint or the subacromial bursa. Arthroscopic transglenoid suture techniques have fared better.
• Bankart type repair, with repair of the torn glenoid labrum and capsule (gold standard). Long term followup at mean of 12 years has 92% good or excellent results and redislocation rate of less than 5%.
• Putti-Platt type repair, with shortening and double breasting of the subscapularis – provides good stability at the expense of decreased external rotation
• Magnuson-Stack repair – transposition of the subscapularis from the lesser tuberosity to the greater tuberosity
• The Putti-Platt and Magnuson-Stack repairs limit external rotation and lead to a dramatic increase in early onset glenohumeral arthritis.
• Bristow-Laterjet repair, where the antero-inferior capsule is reinforced by redirecting muscles across the front of the joint – the coracoid process with its attached muscles is transposed to the front of the neck of the scapula
• Boyd-Sisk – transfer of biceps laterally and posteriorly
• Osteotomies e.g. correction of reduced retroversion angle of the humeral head (Brostrom and Kronberg)
Technique of Bankart repair (Matsen)
He makes no attempt to tighten the capsule.
Deltopectoral approach. Subscapularis and subjacent capsule incised 5mm medial to the lesser tuberosity. The subscapularis and capsule are retracted medially as a unit and the humeral head is retracted with a humeral head retractor. The Bankart lesion is exposed and the labrum held away with an angled spiked retractor. The anterior lip of the glenoid is roughened up, then holes are placed in the glenoid 5mm apart and 3-4mm back from the edge of the glenoid, and using an angled curette the holes are extended onto the anterior aspect of the neck.
The sutures are then passed through the medial capsule and the base of the labrum, and tied so the knots lie over the capsule rather than the glenoid. The subscapularis and capsule is then repaired.
If an unexpected deficiency of the anterior glenoid is noted at surgery, it can be addressed by transferring the coracoid process into the defect.
Postoperatively the patient is limited to passive 90 FF and 0 ER for three weeks, then 140 FF and 40 ER for the next three weeks.

Prognosis
Redislocation rates range from 47% to 100%.
Recurrence can occur regardless of the type or duration of immobilization.
Lavaging the haematoma from an acute dislocation reduces the redislocation rate.
One third of initial dislocations do not recur.
One fifth of recurrent dislocations stabilize spontaneously.
Chronic dislocation
A dislocation is termed chronic if it has been for 6 weeks or more.
If the shoulder has been dislocated for 6 months or more an arthroplasty can be an appropriate salvage.

Posterior dislocation

Epidemiology
Up to 70% of posterior shoulder dislocations are missed.
Aetiology
The muscles passing anterior to the shoulder joint axis of rotation are stronger than the ones passing behind, and in a very violent contraction, as in an epileptic fit or electrocution, they may force the humeral head posteriorly.
Labral detachment is only seen in around 10% of cases.

Clinical
Usually caused by electrocution or fitting.
The arm is flexed, adducted and internally rotated, and attempts at external rotation are resisted.
Recurrent episodes usually take the form of subluxation rather than dislocation.
With posterior instability there may be slight winging of the scapula. Tenderness on palpation of the posterior joint line is seen in 2/3.
The posterior apprehension test (jerk) test involves forward flexion and internal rotation of the shoulder with a posterior force on the elbow. This leads to posterior subluxation, which is reduced by bringing the arm out into abduction. The reduction produces a palpable and audible clunk.

Imaging
AP may have a light bulb appearance
Axillary view will confirm the diagnosis.
May develop a reverse Hill-Sachs lesion.
May be associated with lesser tuberosity fractures.

Treatment

Closed reduction.

Physiotherapy should emphasize posterior deltoid strengthening and external rotator strengthening.
Recurrent dislocations may warrant surgery but the results are not as good as in anterior dislocations.
The posterior capsule may be plicated arthroscopically.
Open techniques include posterior capsulorrhaphy and glenoid osteotomy. The posterior capsular reconstruction may be augmented with a posterior bone block, and the shoulder is held abducted and externally rotated in a spica for 6/52. It has been thought that excessive retroversion of the head may contribute, (treated with an internal rotational osteotomy of the humerus) but this is actually rarely the case. Defects in bony anatomy are rarely implicated, so the usual approach is a posterior capsular shift.
The surgical approach to the shoulder is via a deltoid split, from the posterolateral corner of the acromion (which marks the junction of the middle and posterior thirds), followed by an infraspinatus splitting incision. In the approach, remember that the axillary nerve is 65mm from the posterolateral corner of the acromion (the suprascapular nerve is 20mm medial to the glenoid rim).
A CT scan should be performed prior to operation and if there is excessive glenoid retroversion an opening wedge osteotomy should be considered.
Chronic posterior dislocation can be managed with the McLaughlin operation. This involves reduction of the humeral head and transfer of the subscapularis into the reverse Hill-Sachs defect.

Multidirectional instability
Associated with capsular and ligamentous laxity, and often shoulder muscle weakness and incoordination. The instability may occur during mid range activities.
Little force is required to displace the joint and subluxation may occur during daily activities. The patient feels the joint has become loose and they may feel it slip out and clunk back in with different activities.
Often familial and bilateral, because often reflects developmental abnormalities.
Often painful, whereas traumatic anterior and posterior instability is often not painful.

Examination
Assess for ligamentous laxity.
Matsen advises getting the patient to demonstrate the actions that provoke instability.
Inferior instability may be demonstrated by the sulcus test. The instability tests are repeated on the other side, which provides an opportunity for the patient to be educated that the asymptomatic shoulder must be stable from good mechanics, and the symptomatic shoulder can be treated with appropriate strengthening.

Imaging
The XR characteristically show no bony pathological changes, apart from developmental changes such as glenoid hypoplasia which may be seen in some cases.
They may show subluxation.

Treatment
Muscle strengthening and proprioceptive exercises may be beneficial. Matsen emphasizes that the patient should avoid any temptation to “pop the shoulder”.
Surgery is rarely performed and if done is an inferior capsular shift. Matsen emphasizes that the patient must have complied well with a programme of physiotherapy prior to surgery, as it is the physiotherapy and mid range proprioception that will provide a successful result. The theoretical problem in performing a shift is that instability is usually felt with the shoulder in midrange positions, and tightening the capsule will only stabilize the extremes of movement. Capsular shift provides satisfactory outcomes in 85-90% over the long term, but the success of inferior capsular shift in reestablishing normal shoulder function is substantially less than with traumatic instability.
Technique Essence: the rotator interval is tightened and the posteroinferior capsular recess is reduced. A substantial defect is seen consistently in the AMBRII syndrome.
A deltopectoral incision is made. The subscapularis is dissected free of the underlying capsule. The defect in the rotator interval is repaired with Ethibond sutures. The capsule is then divided around to approximately the 6 or 7 o'clock position – far enough such that superior traction on the capsule will cause the capsule to tighten on a finger introduced into the capsular recess.
A bony trough is then created along the capsular border of the anteroinferior neck, and the capsule is sutured to the bone while superior traction is maintained on the capsule. The redundant superior flap is folded back down anteriorly to reinforce the repair.
After an inferior capsular shift a neutral rotation brace is used to protect the repair for a month. Isometric abduction and external rotation exercises are started immediately. Swimming is allowed 6 months after surgery, and sports are restricted for one year.
It is emphasized that the patient shouldn't “test out” the new repair at any time.
Thermal capsular shrinkage seemed to be in vogue for a period but is now out.

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