Traumatic Anterior Shoulder Instability

Sanj Anand & Lennard Funk

Edited from Orthoteers using JBJS; Current Orthopaedics, Cochrane review

Laxity vs instability

• Difference = symptoms
• Laxity implies a degree of translation at GH joint which falls within a physiological range and is asymptomatic
• Instability is an abnormal symptomatic motion for that shoulder which results in pain, subluxation or dislocation of that shoulder

SHOULDER STABILISERS

Static restraints

These keep the shoulder in joint when at rest

1. Intracapsular pressure: normally the intracapsular pressure of the shoulder is negative
2. Suction effect: glenoid labrum acting on humeral head like a “plunger”
3. Adhesion-cohesion: between 2 wet smooth surfaces
4. Glenoid version: may have bearing on a few cases with recurrent posterior dislocation but exception is in patient with congenital glenoid dysplasia
5. Humeral retroversion: normal 21-30º, some studies have shown a significant reduction in patients with recurrent anterior dislocation
6. Labrum: “chock block” to humeral head movement, increases depth of the glenoid by 50%
7. Ligaments:
1. Coracohumeral ligament
2. Superior glenohumeral ligament (SGHL)
3. Middle glenohumeral ligament (MGHL)
4. Inferior glenohumeral ligament complex (IGHLC)
5. Posterosuperior capsule

Dynamic constraints

Keep the shoulder in joint during activity

• Lephart et al 1994 studied proprioception in three groups of patients: Normal, Unstable, Reconstructed shoulders.
• Study found that proprioception was significantly reduced in unstable shoulders but returned to near normal in reconstructed shoulders

3. Long head of biceps: biceps is much more active in patients with recurrent dislocation

CLASSIFICATIONS

TUBS and AMBRI (Matsen)

TUBS or “Torn Loose”

• Traumatic aetiology
• Unidirectional instability
• Bankart lesion is the pathology
• Surgery is require

AMBRI or “Born Loose”

• Atraumatic: minor trauma
• Multidirectional instability may be present
• Bilateral: asymptomatic shoulder is also loose
• Rehabilitation is the treatment of choice
• Inferior capsular shift: surgery required if conservative measures fail

Voluntary Dislocator

• Often associated with a psychiatric condition or alternative gain
• The desire to voluntarily dislocate the shoulder cannot be treated surgically.

STANMORE CLASSIFICATION

Takes into account the marked overlap between traumatic and atraumatic dislocators and also the fact that these do change over time.

[Lewis et al Current Orthopaedics 2004 18; 97-108]

PATHO-ANATOMY

Capsule:

• Stretch of capsule in continuity
• Congenital laxity
• Wide rotator interval

Glenoid:

• Bony Bankart
• Ideburg-1 fracture
• Crevassing

LHB:

• SLAP tear

Labrum:

• Bankart tear
• Posterior labral tear

Humerus:

• Tear of the ligamentous insertion (HAGL)
• Greater tuberosity fracture
• Hill-Sachs lesion

Rotator cuff:

• Supraspinatus tear
• Subscapularis avulsion

 

• Experiments have shown that removal of the antero-inferior labrum decreases stability ratio by 65%.
• Stability deteriorates further when the Bankart lesion is assoc with stretching or tearing of the capsule and the GH ligs
• Labrum and IGHL, with its ant band, play a crucial role in stability

CLINICAL CLASSIFICATION

When ? - Acute / Neglected (chronic) / Recurrent

How ? - Traumatic / Atraumatic / Voluntary

Direction? - Anterior / Posterior (~ 2% of shoulder dislocations) / Inferior – luxatio erecta / Multidirectional

Degree ? - Dislocation / Subluxation

Why ? - Torn loose / Born loose

Classifications can also be based on:

• Bone condition – humeral head and glenoid
• Patient condition – age, laxity, sport activity etc

CLINICAL ASSESSMENT

Neurovascular examination - All nerves can be affected but most commonly the axillary and musculocutaneous nerves

Laxity tests

1.  Anterior and posterior draw with patient supine or seated
2. Inferior draw “Sulcus sign” – hallmark of multidirectional instability
3. Load & shift test - performed with the patient supine; the examiner abducts & ER the shoulder & pushes from behind. This can dislocate the shoulder fully & is thus better on an anaesthetised patient.

Instability tests

1. Anterior apprehension test
2. Relocation test - once the patient feels the joint slipping out with the ant. apprehension / crank tests, the examiner then pushes backwards & relocates the joint.

Also look at:

1. Core Stability
2. Scapula Patterning through flexion and abduction
3. Generalised Laxity (Beighton Score)

Investigations

 

NATURAL HISTORY OF ANTERIOR DISLOCATION

• Adolescent when the patient's proximal humeral growth plate is open, there is up to 100% rate of redislocation
• Young adults (18-30 years) the rate of redislocation ranges from 17% to 96%, mean 67%
• Increased rate of recurrence in younger age groups
• Patients > 30years redislocation rate <10%

SURGICAL TREATMENT

Indications

• No hard criteria, but:
• Young patient < 30years
• Athletic
• 2 dislocations in 2 years

Anterior reconstruction

• Repair of the Bankart lesion
• Repair of SLAP lesion if present
• Inferior capsular shift
• Subscapularis closed without tension

ARTHROSCOPIC SURGERY FOR SHOULDER STABILISATION

• Arthroscopic stabilisation allows repair of structures anatomically without affecting the surrounding normal tissues
• Results are variable and depend on many factors including surgical technique, surgeon experience and patient factors

Assessment of intraarticular lesions

• Bone fracture assessment
• Hill-sachs lesion
• Glenoid fracture
• Humeral insertions of MGHL and IGHL are critical
• Detachment of these is a contraindication to arthroscopic repair
• Flex shoulder and IR to allow scope under subscap to assess ant/inf humeral insertion area
• Glenoid rim
• Looking for labral or capsular detachment
• Attempt assessment of plastic deformation of ligaments
• Detachment of capsuloligamentous structures
• VAPR radiofrequency can be used along the length of the lesion
• Should be extended above lesion to allow for tensioning on reattachment
• Simple reattachment of labrum is not enough to stabilise joint
• Release residual adhesions
• After release south-north tightening is assessed

Reattachment of capsule with bone anchors

• According to amount of south-north translation

Adequate knot tying

Other capsular structures can be repaired using the same technique

• If labral detachment extends posteriorly
• SLAP lesions

OPEN PROCEDURES FOR SHOULDER INSTABILITY

Open Bankart repair

• Deltopectoral approach
• ER allows subscap tendon to be visualised
• If required feel for axillary nerve
• Identify precise location of GT, bicipital groove and LT
• Incise subscap tendon vertically 1cm from its attachment to LT, and dissect between tendon and capsule and mobilise tendon
• Incise capsule vertically immediately lateral to glenoid rimand extend laterally – T incision
• Complete any capsulolabral avulsion
• Retract labrum and subscap medially to prepare bone for anchors (bleeding bone)
• Place anchor holes at glenoid rim, and test pullout strength of anchors 
• Reattach labrum/medial capsular flap
• Shift and reattach lateral capsular flap
• Should be done with arm in some ER
• Inferior capsule shifted superiorly
• Superior capsule shifted inferiorly
• Reinforce with sutures between these two flap
• Reattach subscap
• Consider closure of rotator interval if large
• Postoperatively restrict elevation above horiz and ER for 6 weeks

Redislocation rates are reported to be between 1 and 7%

Restriction of movement

OA

Transposition of the coracoid process (Bristow-Latarjet)

• Bone block of coracoid is transferred to anterior scapular neck; can be screwed in place
• Thought to give increased support of ant/inf aspect of joint by conjoined tendons in AB an ER
• Good long term results, with redislocation 3%
• However restriction of ER was found
• OA in 71% at 20 years
• Indicated if glenoid fracture of >25% of glenoid surface

Subscapularis shortening (Putti-Platt)

• Historical
• Lateral stump of subscap is attached to most convenient ST structure on glenoid rim
• Stitched with arm IRd
• Medial portion of capsule is pulled laterally to overlap subscap tendon
• Further overlap with subscap muscle belly being attached to sacrificed tendon
• 90% good results reported
• Restriction of ER in 70%
• Recurrence rate 23% at 27 years; OA in 58%
• Useful in revision surgery or if marked capsular deficiency

Post-operative rehabilitation

0-3 Weeks

• Sling
• Full Passive ROM as comfortable
• Active Assisted ROM
• Isometrics & Closed Chain

3-6 weeks

• Active assisted -> Active
• Open chain

6-12 weeks

• Return to Sports Rehab.

Complications

1. Nerve injury:

• Meta-analysis of 53 papers (3187 patients) following surgical repair showed an average redislocation rate of 3%

4. Infection

• Rare

5. Arthritis

• Can occur after too tight a closure, as seen with the Putti-Platt
• Hovelius 1996 found 20% had radiographic evidence of OA at 10 years
• Incidence was not related to the number of dislocations