Glenohumeral Instability -

Aetiology

Atraumatic
- Instability can develop with no injury
Traumatic
- Indirect (common) – Abduction/ Extension/ External rotation force
- Direct (rare) – Posterior blow
TUBS
- Traumatic onset
- Unidirectional instability
- Bankart lesion often present (85%)
- Surgery to achieve stability
AMBRI
- Atraumatic
- Multidirectional
- Bilateral involvement
- Rehabilitation in first instance (successful 88%)
- Inferior shift if failed rehabilitation

Epidemiology

most frequently dislocated major joint
50% anterior shoulder dislocations occur in persons aged 15 to 29 years
males 3: females 1

Anatomy

Biomechanics of Shoulder Stability

Static Stabilisers

Bony Stability
- Very little inherent stability
- Glenoid surface only slightly concave & 1/4 the size of the humeral head
  - concavity measuring 2.5 mm deep
- pear-shaped glenoid measures 5 cm in its craniocaudal dimension and 2.5 cm in its inferior anteroposterior dimension
- anteroinferior rim of the glenoid is important to antero- inferior glenohumeral stability
- In biomechanical studies, loss of 20% of the anterior glenoid rim has been shown to significantly reduce the force required for anterior glenohumeral translation
Labrum
- Important in deepening of the labrum & ↑ contact area of humeral head to 3/4
- adds to glenohumeral stability by increasing the depth of the socket by between 2.5 and 5 mm and by providing negative hydrostatic pressure between the humeral head and the glenoid
- Provides site of attachment of capsule & glenohumeral ligaments
- There are differences between the superior & anteroinferior regions
  - Superior labrum
    - meniscal pattern
    - triangular cross section
    - loose glenoid attachment
  - Anteroinferior labrum
    - firm attachment to rim
    - serves as fibrous attachment to site of the IGHL complex
    - Detachment of only the IGHL from the labrum was not enough to cause anterior instability
Capsular Ligamentous Structures
- Three glenohumeral ligaments reinforce the anterior capsule
  - IGHL
    - Most Important
    - Resists anterior translation
    - Anterior band limits external rotation at abduction > 90°
    - Anterior & Posterior band with sling between
    - Origin
      - Anterior band glenoid 3 o’clock,
      - Posterior band 9 o’clock
      - Continuous with glenoid labrum
    - Insertion
      - Inferior anatomical neck humerus
  - MGHL
    - Secondary restraint anterior translation
    - Limits external rotation at 45° abduction
    - Present in 60%
    - Origin
      - Superior glenoid
    - Insertion
      - Medial to lesser tuberosity
  - SGHL
    - Functions only in adduction
    - Prevents inferior subluxation
    - No function in decreasing anterior translation
    - Present in 50%
    - Origin
      - Superior glenoid anterior to LH biceps
    - Insertion
      - Lesser tuberosity
Rotator Cuff and Long Head of the Biceps
- subscapularis tendon also acts as a passive restraint to anterior translation
- the rotator interval, including the biceps tendon, SGHL, and cor- acohumeral ligament, play an important role in static glenohumeral stability in conjunction with the MGHL

Dynamic Stabilisers

Rotator Cuff
- Rotator cuff acts by compressing the humeral head against the glenoid
- This ensures that the more compression that is achieved then the harder it is to translate anteriorly or posteriorly
Scapulohumeral Balance
- Periscapular muscles align the glenoid cavity to the joint reaction force of the humeral head (ie. balancing ball on seal’s nose)
The capsuloligamentous structures provide afferent proprioceptive feedback to muscles stabilising the shoulder

Structure	Function
Coracohumeral ligament	Primary restrait to inferior translation of the adducted arm and to ER
Glenoid labrum	Increases surface area Static stabilizer
SGHL	Primary restraint to ER in adducted or slightly abducted arm Primary restraint to inferior translation in the adducted arm
MGHL (absentup to 30%)	Primary stabilizer to anterior translation, with the arm abducted to 45 degrees
IGHLC	Primary stabilizer for anterior and inferior instability in abduction

Glenohumeral stabilizers

Classification

Mechanism
- Traumatic
- Atraumatic
- Laxity
- Overuse
Direction
- Unidirectional
  - Anterior (98%)
  - Posterior (2%)
  - Inferior (Luxatio Erecta)
- Multi-Directional
  - Anterior/ Inferior
  - Posterior/ Inferior
  - Anterior/ Posterior/ Inferior
Chronology
- Congenital
- Acute
- Chronic
- Locked
- Recurrent
Volition
- Involuntary
- Voluntary
Degree
- Subluxation
- Dislocation

Pathology

Bankart lesion

Inferior & middle glenohumeral ligament labral avulsion
- First described by Perthes (1906) & popularised by Bankart (1938)
Bony avulsion may be present
- > 85% TUBS have Bankart lesion (Rowe, 1978)

Bony involvement

Glenoid Rim Avulsions
- Usually part of Bankart lesion
- Management
  - Reattach if large
  - Ignore if small
- May see erosions with repeated dislocations
Hill Sachs Lesion
- Osteochondral lesion in posterosuperior humeral head
- Impaction of humeral head against the glenoid rim in anterior dislocation
- Reverse lesion seen anteriorly with posterior dislocation
- Result of initial dislocation
- May produce subsequent dislocations as defect lies in glenoid cavity when shoulder abducted & externally rotated

Muscle

Uncommon cause of instability
Cuff Tears
- Subscapularis may be torn & contribute to instability
- Cuff tears seen with dislocations in older age groups
  - > 40 years 30%
  - > 60 years 80%
Present as pain or weakness
Rotator interval may be ↑
Between Supraspinatus & Subscapularis
Tends to open up with AMBRI

History

Dislocation
- Ask patient
  - First dislocation
    - time
    - mechanism
    - age of first dislocation
    - management
  - Frequency
    - mechanism
    - how reduced each time
      - self reduced
      - in Emergency department
      - in Theatre
  - Sports
  - Work
  - ADLs
    - are you dislocating when sleeping?
    - do you dislocate with performing everyday activites?
  - Handedness
  - General flexibility

Examination

Seated patient
- First ask them to reproduce their “party trick”
  - If can then habitual dislocator don’t operate
Look
- Deltoid atrophy and hypoesthesia over the lateral aspect of the proximal arm may indicate axillary nerve injury
- More extensive motor and sensory disturbances may suggest an underlying brachial plexus injury
ROM
- Decreased abduction, ER & extension
- Reduced abduction actively may suggest
  - Rotator Cuff pathology
  - Impingement syndrome
- Loss of ER occurs with disuse
- Increased passive external rotation with the arm at the side suggests a tear of the subscapularis tendon, whereas reduced external rotation in 90 of abduction may indicate a medially healed Bankart lesion
Anterior Apprehension Test
- Arm at 45°, 90° & 135° abduction then external rotation insecurity
- Main pathognomic sign
- Patient seated with examiner behind
- One hand grasps the patient elbow & raises to 90° of abduction in ER
- The other pushes the humeral head anteriorly with the thumb & fingers placed anteriorly to control the amount of displacement
Posterior Apprehension Test
- Arm adducted, internally rotated & flexed across chest
- Posterior force insecurity
Anterior Draw
- Seated
  - Test performed with patient sitting & forearms resting on thighs with shoulders relaxed
  - Examiner stands behind with one hand stabilising the scapula & the other clasping the head to test A-P mobility
  - There should be no anterior translation
  - Click suggests labral lesion
- Lying
  - Gerber & Ganz
  - Performed this supine & in the anaesthetised patient
Sulcus Sign
- May suggest multidirectional instability
- Patient sitting with shoulders relaxed & arms by side
- Downward traction on arm with development of sulcus under the acromion evidence of inferior laxity
- Positive test
  - test other side (frequently bilateral)
Jobe Relocation Test
- Patient supine & shoulder protruding over the table
- Arm in abduction & ER with humeral head gently pushed forwards by examiner’s knee under patient’s arm while being supported anteriorly by examiners hand
- With anterior instability pain or apprehension present when the head is subluxed anteriorly
- Pain disappears with relocation by pushing posteriorly
Posterior Apprehension Sign
- May suggest MDI in setting of anterior dislocation
- Patient seated with examiner in front
- Arm in forward flexion, adduction & IR across the chest
- Examiner applies posteriorly directed force & other hand stabilises the scapula
- Apprehension or pain is positive
Volition
- Ask patient if can reproduce dislocation

Investigations

Xray

True AP
True axillary
Scapula lateral (transverse scapula)
Things to look for
- direction
- associated fractures
How shoulder radiographs are taken
- True AP of GHJ
  - AP at 30-45° to sagittal plane with plate behind scapula
  - Can be done with IR, neutral, ER to look for calcific tendonitis
  - Can be done with full IR to show Hill-Sach’s lesion
- Axillary Lateral
  - Abduction of shoulder to 90° with beam aimed through the axilla
  - Shows orientation of humeral head with glenoid
  - Can also be useful in acute trauma with only 20° shoulder abduction
- Scapular Lateral (Y-scapular, transverse scapular)
  - If axillary view not possible
  - Beam from posterior along line of scapula to plate held perpendicular to scapular spine over front of shoulder
- Garth
  - AP beam aimed 45° laterally in coronal plane & 45° caudal in transverse plane to plate held behind the shoulder
  - Visualises the anterior & anteroinferior rim of the glenoid & shows bony Bankart lesions
- West-Point
  - Patient prone with arm hanging off bed & plate superior to shoulder
  - Beam aimed 25° caudal to transverse plane & 25° lateral to sagittal plane
  - Visualises the anterior & anteroinferior rim of the glenoid & shows bony Bankart lesions
- Stryker Notch
  - Patient supine with shoulder flexed with affected hand on head
  - Beam then directed in AP plane with 10° cephalad tilt
  - Displays Hill-Sach’s lesion
- Supraspinatus Outlet
  - Similar set-up as Y-scapular with posterior-to-anterior beam with 5-10° caudal tilt
  - Delineates morphology of acromion
- Anterior Acromial
  - AP of GHJ with 30° caudal tilt
  - Visualises subacromial spurs
- ACJ
  - AP with 10° cephalad tilt
  - Stress view with 10-20lb weight suspended from wrists
- Serendipity
  - AP view of SCJ with patient supine with beam directed in 40° cephalic tilt
  - Useful for SCJ dislocation but CT often gives more information

MRI

MRI is very sensitive for confirming the clinical suspicion of a labral tear.

CT Scan

Useful to assess the anterior structures – labrum & bony rim of glenoid
Axial CT scans are helpful in deter- mining the extent of glenoid bone loss and humeral head impaction

EUA/ Arthroscopy

When examination & other investigations not diagnostic
Two areas important on the arthroscopy are
- Hill-Sach’s lesion in posterosuperior humeral head
- Labral-Capsular complex

Treatment

The treatment depends on level of disability
- Frequency of dislocations
- Ease or difficulty of reduction
- Presence of interval symptoms
- Activity requirements of patient
- Age of patient
Indications for surgery
- Failure rehabilitation
- Moderate-Severe disability
- In skeletally immature delay surgery for as long as possible else recurrence
Contraindications for surgery
- The patient with mild to moderate disability
- The patient with pain due to secondary impingement
- Voluntary dislocators

Non operative

Principles
- Avoid provocative positions
- Strengthen cuff, deltoid & periscapular muscles
- Balance the shoulder function

Operative

Should recognise the following factors prior to undertaking surgery
- Generalised ligamentous laxity
- Multidirectional instability
- Humeral head or Glenoid defects
Divided into 4 groups (> 150 procedures described)
- 1. Bony
- 2. Musculotendinous
- 3. Capsulolabral
- 4. Combination

1. Bony Procedures

Seek to achieve stability through bony containment
Includes
- Anterior Bone Block
- Humeral osteotomy
- Glenoid neck osteotomy
Bristow’s Procedure
- Developed in 1958 by Arthur Helteland & named after chief Sir Rowely Bristow
- Acts as
  - Non-anatomical glenoid bone block
  - Dynamic sling in abduction & ER & prevents the subscapularis migrating superiorly
- Detach the predrilled coracoid process with conjoined tendon & transferred to anterior glenoid neck through split in subscapularis & attached with screw to decorticated bed
- Significant complications
  - Non union of coracoid
  - Screw problems 2-14%
  - Musculocutaneous Nerve injury
  - Instability 1-20%
  - Loss of ER 12-20°

2. Musculotendinous

Putti-Platt
- Described in 1948 by Osmond-Clark but first used by Sir Henry Platt of England & Vittorio Putti of Italy
- Principle based on trying to buttress the anteriorly unstable humeral head
- Functions through limiting ER & Concomitant capsular shift
- Indications
  - Dislocation secondary to neuromuscular imbalance
  - > 40% Hill-Sach’s lesion that allows camming of head in glenoid
- Technique
  - Divide subscapularis 2.5cm from the humeral insertion
  - Lateral stump reattached to most convenient soft tissue structure along the anterior rim of glenoid
  - Medial stump lapped over the lateral producing significant shortening
- Complications
  - Loss of ER
  - Osteoarthritis if over tightened
  - Only 50% of athletes return to sport
- Recurrence
  - rate of 3%
Magnuson Stack
- Described by Paul Magnuson & James Stack in 1940
- Shift the subscapularis laterally & inferiorly to close the gap when subscapularis moves superiorly with abduction
- Technique
  - Detaching subscapularis from the LT & transferring to GT lateral to biceps tendon & 10mm inferiorly
  - Capsule shifted with subscapularis
- Complications
  - Limiting ER
  - Recurrence rate 3%

3. Capsulolabral

Restoration of anatomy
Bankhart Repair
- First described by Perthes in 1906 but popularised by Bankart in article from 1923
- The original article described reattachment of the Bankart lesion to the glenoid with drill holes & had 27 cases with full movement & no recurrence of dislocation
- Rowe & Zarins in 1981 – outlined the procedure
- Advantages are
  - Direct anatomical repair of damaged structures
  - Able to add intraoperative capsular shift if only see redundant capsule
  - No loss of ER
- Surgical Technique: Open Bankhart Repair

Results

95% successful with 3% redislocation rate

Complications

Infection
Recurrent instability
Musculocutaneous or Axillary Nerve injury
Motion restriction

Risks with beach chair position
- Head position
- Eyes padded & taped
- Airway may be dislodged
- Head taped to Mayfield head rest but be careful of neck injuries
Neurological complications
- Brachial plexus injury
- Ulnar nerve injury
- Sciatic nerve palsy
- Make sure you have knees flexed
- CPN palsy
Pressure areas
- Back of head
- Ischial tuberosities
- Heels
Air embolism from sucking vein
- Avoid opening large veins
- If so then tell anaesthetist & lay patient head down
Control of bleeding
- Tell the anaesthetist
- Contact a vascular surgeon
- Direct pressure
- Proximal & distal control
- Extend the wound proximally & distally & Ligate offending vessel
- If not Divide conjoint tendon (biceps & coracobrachialis) ± pectoralis minor to get access to subclavian artery
- If not Osteotomise the clavicle
- If not Pressure on subclavian artery behind sternoclavicular joint
- Important Vessels
  - Subclavian artery
    - Arise from L. common carotid on left & from the brachiocephalic trunk on the right then passes behind the scalenus anterior which divides it into three parts
    - 1st part vertebral, thyrocervical trunk, internal thoracic
    - 2nd part costocervical trunk
    - 3rd part (no branches)
    - 3rd part lies behind the SCJ
  - Subclavian vein
    - Passes anterior to scalenus anterior
  - Axillary artery
    - Arises from lateral border of 1st rib (behind midpoint of clavicle) to lower border of teres minor & divided into three parts as it passes behind pectoralis minor
    - 1st part superior thoracic
    - 2nd part acromiothoracic, lateral thoracic
    - 3rd part subscapular, anterior & posterior circumflex humeral

Arthroscopy prior to open repair

Uncertain if of value

Arthroscopic Repairs

Introduced as stated to
- Allow better joint visualisation
- Reduce the skin incision & dissection
- Improve ROM (ER)
Indications uncertain
- Best is
  - Young patient < 25
  - First traumatic anterior dislocation
  - Bankart lesion demonstrated
Reattach using
- Sutures (Caspari)
- Tags
- Anchors
Redislocation rates
- 12-40%

Other Procedures

McLaughlin
- For posterior dislocation when IR
- Reverse Hill-Sach’s filled with bone from osteotomy of LT & attached subscapularis mm
- Suture or screw
Reverse McLaughlin
- For anterior dislocation when ER
- Hill-Sach’s filled with bone from osteotomy of GT & attached infraspinatus mm
- Suture or screw
Chronic Stiffness Post Operative
- Consider anterior release when external rotation less then 0°
- Accept when it is > 30°
- Individualize in between
- Loss of rotation at 0° abduction with good rotation at 90° abduction
  - Suggests subscapularis the cause

Prognosis

Natural History

Hovelius et al 1996

Hovelius L, Saeboe M: Neer Award 2008: Arthropathy after primary anterior shoulder dislocation: 223 shoulders prospectively followed up for twenty-five years. J Shoulder Elbow Surg 2009;18(3):339-347.

247 primary anterior dislocations (245 patients) followed for 10 years
Age range 12-40 years
Sling immobilisation for variable periods
At 10 years
- 48% redislocated
- 23% required operative stabilisation for recurrent dislocation
- 22% spontaneously stabilised
Hill-Sach’s lesion associated with higher rates of recurrence
Fractures of greater tuberosity were less likely to recur
Type & duration of initial treatment had no effect on rate of recurrence
Post-dislocation arthropathy at 10 years
- 11% mild
- 9% moderate/ severe
Some shoulders with arthropathy did not have recurrence (suggesting initial injury responsible for arthropathy rather than repeated episodes of dislocation)