Shoulder Instability

Original Editor - Johanna Guim and Katherine Burdeaux as part of the Temple University Evidence-Based Practice Project Top Contributors - Katherine Burdeaux, Nupur Smit Shah, Lucinda hampton, Admin, Rachael Lowe, Kim Jackson, Naomi O'Reilly, Johnathan Fahrner, Birgit Schauvliege, Vandoorne Ben, Fasuba Ayobami, Simisola Ajeyalemi, Johanna Guim, WikiSysop, Uchechukwu Chukwuemeka, Joao Costa, Rucha Gadgil, Wanda van Niekerk, Aminat Abolade and Scott A Burns

Introduction

Shoulder Diagram

The glenohumeral joint of the shoulder has the highest range of motion of the human body and the most inherently unstable, often developing recurrent instability.

Shoulder instability is defined as loss of shoulder comfort and function due to undesirable translation of humeral head on the glenoid fossa.

The ligamentous and muscle structures(static and dynamic stabilizers) around the glenohumeral joint, in normal conditions, create a balanced net joint reaction force. If the integrity of any of these structures is disrupted it can lead to spectrum of pathologies from subluxation to dislocation.

Both structural and nonstructural components can contribute to the instability of the shoulder.

Classification of Shoulder Instability

Stanmore Triangle

This classification helps the therapist to correctly diagnose the instability and prioritize the treatment.

There are three main subgroups in this classification:

Polar 1: Shoulder instability is directly related to trauma. There is evidence of a structural deficit in the GH joint

Polar 2: There is evidence of structural deficit and atraumatic instability

Polar 3: No evidence of structural defects. Muscle patterning is present.

Based on the direction of shoulder instability

Anterior Instability

There occurs translation of the humeral head in the anterior. direction It is the most common form of shoulder instability.

Posterior Instability

It accounts for 2 to 5 % of instability cases. Usually, the athletic population is affected by this type of instability who participate in an overhead activity. Structural issues like posterior glenoid erosion and glenoid retroversion or deficiency of rotator interval can predispose patients to posterior instability.

Multidirectional instability (Atraumatic)

There is a combination of anterior /posterior/inferior instability at the GH joint. In many cases, this type of instability is because of generalized laxity throughout the body. Another cause is repetitive trauma during extremes of motion.

Mainly the pain is during the mid ranges of shoulder ROM which indicates main role of altered muscle activation. Inappropriate position of the scapula can also be the reason for pain or any other symptoms.

Traumatic Unidirectional Instability with Bankart lesion (TUBS)

Anterior Dislocation

This is the commonest sports injury in which acute anterior dislocation of GH joint occurs. The arm is forced into excessive abduction and external rotation. It damages the anterior part of the labrum (Bankart lesion).

The patient presentation is arm adduction and internally rotated with loss of deltoid contour. Posterior sulcus/glenohumeral void is observed. The humeral head is palpated anteriorly. Radiographs are used to confirm the diagnosis and rule out other bone injuries.

One of the three following criteria has to be fulfilled in order to prescribe the Xray :

Age>40, first time dislocation, traumatic mechanism of injury.

Posterior Dislocation

It is less common than an anterior dislocation. The cause is a fall on the outstretched hand or a direct blow on the shoulder in internal rotation of adduction. The Cardinal sign is limited external rotation. An X-ray of lateral view or axillary view is necessary for diagnosis.

Acquired sport-specific instability

This type is commonly seen in overhead athletes when the anterior capsule has become lax due to overuse. This is also known as an acquired instability overuse syndrome. Clinical features are recurrent shoulder pain while throwing, sudden inability to throw or smash and a feels like 'dead arm', GIRD /scapular dyskinesia /signs of labral pathology are also seen.

Apprehension /relocation tests are positive.

This condition can turn into impingement due to abnormal translation of humeral head.

Atraumatic

Abnormal position or motion of the shoulder joint that leads to pain, subluxation, dislocation and functional impairment.

Atraumatic (non-traumatic) shoulder instability is a subclassification of glenohumeral joint instability, encompassing those for whom trauma is not considered the primary etiology.

Two main types of atraumatic instabilities:

1. Congenital instabilities;
   • Laxity of structures in the shoulder which may be present since birth.
2. Chronic recurrent instabilities
   • May be seen after surgery for shoulder dislocation, due to glenoid rim lesions.
   • Over time, microtrauma can lead to instability of the glenohumeral joint.

Shoulder Instability Video

This 5 minute video is on shoulder instability and clicking

Clinically Relevant Anatomy 

Glenohumeral stability depends on the combination of various factors that can be grouped into:

1. Capsulo-ligamentary or static stabilizers
2. Musculotendinous or dynamic stabilizers:

1. Static Stabilisers

Glenoid fossa, on R side

The static capsulo-ligamentary elements, are considered to be the main stabilizers of the glenohumeral joint Note - The 3 glenohumeral ligaments are thickenings of the glenohumeral joint capsule.

1. Superior glenohumeral ligament (SGHL) - limits anterior and inferior translation of adducted humerus
2. Medial glenohumeral ligament (MGHL) - limits anterior translation in lower and middle range of abduction
3. Inferior glenohumeral ligament (IGHL) - longest glenohumeral ligament and primary static restraint against anterior, posterior and inferior translation when humerus is abducted beyond 45 degrees
4. Glenoid labrum - increases depth of glenoid cavity and increases stability up to 50%
5. Negative intra-articular pressure - assists in maximizing joint congruency

The proprioception mechanisms of the shoulder joint have been investigated and found to be closely related to the response of the dynamic muscle stabilisers.

• Various histological studies in anatomical specimens have confirmed the presence of afferent nerve endings (Ruffini corpuscles and Pacini mechanoreceptors, sensory receptors that responds to mechanical changes of tissues) and they are distributed in the shoulder capsuloligamentary complex.
• Cuellarsuggests that shoulder instability can be due to injury and/or failure of the static capsulo-ligamentary stabilizing elements (which are supporting the sensitive afferent ending).
• This alteration of the passive stabilizing elements causes a disturbance or delay in the delivery of the proprioceptive signal, delaying or causes errors in coordination of the muscles response. The dynamic stabilizing mechanism is thus altered and the loss of joint congruity is facilitated.

2. Dynamic Stabilisers

Muscles: scapular region posterior

Assist with holding the humeral head in the glenoid fossa during movement

1. Primary

• Rotator cuff muscles (supraspinatus,infraspinatus, teres minor, subscapularis)
• Long head of biceps
• Deltoid

2. Secondary

• Teres major
• Latissimus dorsi
• Pectoralis major

3. Rotator Cuff Interval

Rotator cuff interval

This interval is a triangular-shaped area found in the shoulder, with borders noted below. A large rotator interval allows for increased anterior humeral head translation due to the lack of structures supporting the joint capsule anteriorly.

• Superior border: anterior margin of supraspinatus
• Inferior border: subscapularis  
• Apex: transverse humeral ligament              
• Base: coracoid process of scapular

Potential structures involved in shoulder instability are listed in table below.

Anterior	Posterior	Multidirectional
SGHL,MGHL, Anterior IGHL	SGHL, Posterior IGHL	Dysfunction of dynamic stabilisers
Anterior capsule	Posterior capsule	Joint capsule in 2 or more directions. Inferior capsule is primarily affected.
Coracohumeral ligament	Coracohumeral ligament	All structures involved in anterior or posterior instability can be affected
Superior anterior labrum
Long head of biceps
Subscapularis

Mechanism of Injury

GH joint anterior dislocation

1. Traumatic

The most common glenohumeral dislocation occurs anteriorly, usually as a result of sporting accidents or falls, particularly when the upper extremity is in 90° abduction and external rotation.

Posterior dislocations most commonly result from seizures, shock and falls.

2. Atraumatic

Chronic Recurrent

Abducted, extended shoulder - Tennis serve

Caused by repetitive extreme external rotation with the humerus abducted and extended (i.e.pitching motion). Instability may be caused by gradual weakening of the anterior and inferior static restraints. The humeral head will tend to move away from shortened structures. For example: posterior shoulder capsular tightness will cause the humeral head to shift anteriorly, resulting in a loss of integrity of all anterior structures. Commonly associated with participation in sports such as gymnastics, baseball, softball, tennis, swimming, and weight training.

Common concomitant features or causes:

• Bankart lesion
• Hill­Sachs lesion
• SLAP lesion (Superior Labrum Anterior Posterior)
• HAGL lesion (Humeral Avulsion of Glenohumeral Ligaments)
• ALPSA lesion (Anterior Labroligamentous Periosteal Sleeve Avulsion)
• Laxity of the joint capsule

Right shoulder pain after repetitive shoulder posterior dislocation.

Congenital Instability  

Congenital instability may be the result of:

• Glenoid hypoplasia, also known as glenoid dysplasia, is an uncommon congenital condition resulting from underdevelopment of inferior glenoid ossification centre.
• Decrease anterior-posterior diameter of glenoid
• Increased retroversion of glenoid
• Increased amount and composition of collagen and elastin
• Bony anomalies

Clinical Presentation 

Possible signs and symptoms of chronic/recurrent instability

Anterior Instability

• Clicking
• Pain
• Complain of the dead arm with throwing
• Pain posteriorly
• Possible subacromial or internal impingement signs
• The patient may have a positive apprehension test, relocation test, and/or anterior release test
• Increased joint accessory motion particularly in the anterior direction

Posterior Instability

• Possible subacromial or internal impingement
• Glenohumeral internal rotation deficit (GIRD) may be present 
• Pain
• Clicking
• Increased joint accessory motion particularly in the posterior direction

Multidirectional Instability

• Antero-inferior laxity most commonly presents with global shoulder pain, cannot pinpoint to a specific location
• May have a positive sulcus sign, apprehension/relocation test, anterior release tests
• Secondary rotator cuff impingement can be seen with microtraumatic events caused during participation in sports such as gymnastics, swimming and weight training
• Increased joint accessory motion in multiple planes

Red flags

• Trauma, pain and weakness (indicates rotator cuff tear)
• Swelling/mass (Indicates tumor/malignancy)
• Fever or any systemic illness
• Unreduced dislocation
• Infected joint

Differential Diagnosis

• Rotator Cuff Tear
• Subacromial Impingement
• Internal Impingement
• Cervical Spine Mechanical Pain (referring to shoulder)
• Biceps Tendinopathy
• Labral Pathology
• Laxity due to Congenital Causes (ie: Ehlers-Danlos Syndrome) 

Examination 

Subjective History

• May have history of: trauma with or without a previous dislocation; lax joints (consider elbow, knee, thumb hyperextension, use Beighton scale to evaluate hypermobility)
• Activities of daily living may be difficult to complete
• Global pain around shoulder

Physical Examination

Screen cervical spine and thoracic spine

Observation/Palpation

• Long head of biceps, supraspinatus tendon, AC joint, SC joint, spine, 1st rib, other regional muscles

Posture

• Asymmetry
• Scapular winging
• Atrophy

Active ROM

• Glenohumeral flexion, extension, abduction, adduction, rotation - internal & external, scaption
• Look for apprehensive behavior

Passive ROM

• May have pain and/or stiffness
• Apprehension will be present

Muscle Length Testing

• Upper trapezius, levator scapulae, scalenes, latissimus dorsi, lower trapezius, pectoralis minor, pectoralis major

Resistive Testing

Functional Testing

• Hand to posterior neck
• Hand to scapula
• Hand to opposite scapula

Joint Accessory Motion Testing

• Increased mobility in the direction of the instability (anterior, posterior, multidirectional)

Scapular/Thoracic Motion

Proprioception

Special Tests

• Possibly sulcus sign, apprehension/relocation and/or anterior release tests depending on suspected form of instability. See special tests below.

Special Tests

Provocative tests and laxity examinations may be used to confirm a hypothesis of shoulder instability:

Psychometric Properties of Special Tests

Test	Sensitivity	Specificity	+ LR	-LR
Sulcus	0.17	0.93	2.43	0.89
Anterior  Release Test	0.92	0.89	8.36	0.09
Apprehension	0.53	0.99	53	0.47
Relocation	0.46	0.54	1	1

Laxity Tests

1. Load and Shift Test

Application: The patient lies on their back with the scapula on the table but the caput free. Load the caput humerus into the glenoid and then translate the caput in the anterior and posterior directions.

Conclusion: The test aims to evaluate the amount of translation of the caput humerus on the glenoid. There are many methodes to grade the test but the most common one is the Hawkins grading. This method is considered to be the best one because it has a clinical basis. Hawkins divided the movement in four grades: Grade 0 = little to no movement; grade 1 = the humeral head rises up onto the glenoid rim; grade 2 = when the caput humerus can be dislocate but relocate spontaneously; grade 3 = when the head does not relocate after the pressure. Clinical Bottom Line:Tzannes and Murell have concluded that this test is entirely reliable (p<0,0001) and a LR > 80 for instability.

2. Drawer Test

Application: The patient is positioned supine. The examiner holds the patients scapula with his left hand while grasping the patient’s upper arm and drawing the humeral anterior head with his right hand. You can hold the shoulder in a different position.

Conclusion: The test tells you more about the laxity. The test is positive when the thumb was felt to slide past the coracoid. Clinical Bottom Line: Tzannes and Murell have concluded that this test is still to be assessed as to its validity and reliability.

3. Sulcus Sign

Application: The patient’s elbow is pulled inferiorly while the patient is relaxed

Conclusion: This manoeuvre tests the superior glenohumeral ligament. The test is positive when there is a sulcus of more than 2 cm between the acromion and caput humerus. Clinical Bottom Line: Tzannes and Murell also evaluate this test as being completely reliable (p<0,0001). Nakagawa et al report a specificity of 0.93.

Provocative Tests 

1. Anterior Release Test

Application: In this test, the examiner applies posteriorly directed force to the humeral head, with the patient being in abduction and external rotation.

Conclusion: The test is positive in case of pain or apprehension when easing the pressure. Clinical Bottom Line: In the light of the results of Tzannes and Murell (p<0,0001) and Ian et al we can conclude that it is a reliable test for the detection of the unstable shoulder. Gross et al report a sensitivity of 0.92 and a specificity of 0.89, making this test useful to rule out shoulder instability with a negative result.

Apprehension/Augmentation Test

Application: The apprehension test is being applied when the patient is lying or sitting with the shoulder in a neutral position (90° abduction). The examiner holds the patient’s wrist with one hand and with the other hand he applies anteriorly directed force to the humeral head.

Conclusion: Signs of glenohumeral anterior instability are: pain, a feeling of subluxation or clear defence. If a relocation test is being applied almost immediately after the apprehension test and if this relocation test results to be negative, than we can decide that there is anterior instability. Clinical Bottom Line: Based on the results of Levy et al. ; Ian et al. (sensitivity = 53 & specificity = 99), Tzannes and Murell  (p= 0,0004 pain and/or apprehension and a LR 8-100 for anterior instability) and Marx et al., we are able to conclude that there is not sufficient clinical proof to detect or exclude instability. Lo et al report a specificity of 0.99.

Relocation Test

Application: The patient is in the starting position of the apprehension test and the examiner now applies posteriorly directed force to the humeral head.

Conclusion: When this test results to be negative, there is glenohumeral anterior instability. Clinical Bottom Line: The article by Ian et al.  (sensitivity = 45 & specificity = 54) states that the relocation test is not clinically evident. However, other articles by Tzannes and Murell (p= 0,0003 pain and/or apprehension) and Liu et al. provide evidence to the contrary. Lo et al report poor psychometric properties on this test.

Outcome Measures

• Disabilities of Shoulder, Arm, and Hand (DASH)
• Quick DASH
• Visual Analogue Scale
• Shoulder Pain And Disability Index

Diagnosis specific questionnaires

• Western Ontario Shoulder Instability Index
• Oxford Shoulder Instability Questionnaire
• Melbourne Instability Shoulder Scale

Medical Management 

Medical management will hinge on the specifics of the patient presentation including the mechanism of injury, severity, patient goals, etc. In some cases, particularly those with a traumatic mechanism, surgical intervention may be warranted to restore joint stability.

Types of surgical procedures for traumatic glenohumeral dislocations

1. Open capsular shift
2. Arthroscopic thermal capsulorraphy
3. Labral repair

Physical Therapy Management 

Non-operative physical therapy management will vary in a case-by-case situation and each patient’s care should be individualised to target their specific goals. Physical therapy management is largely impairment-based and response-driven as there is little high-level evidence to assist decision making but commonly includes:

• Education to prevent recurrence
• Postural re-education
• Motor control training of specific muscles during functional activities (rotator cuff muscles, scapular stabilisers)
• Strengthening in particular the deltoid, rotator cuff muscles and scapular stabilisers
• Stretching in particular posterior shoulder structures, pectoralis major and minor and any other muscles with flexibility impairments

Manual therapy targeting impairments of mobility in the glenohumeral, acromioclavicular, sternoclavicular joints and cervico-thoracic spine

Exercise Therapy Findings

A 2020 study to assess the efficacy and safety of physical therapist–supervised, shoulder instability neuromuscular exercise (SINEX) versus self-managed, home-based, standard care shoulder exercise (HOMEX) in patients with traumatic primary and recurrent anterior shoulder dislocations ASDs, concluded "Neuromuscular shoulder exercise (SINEX) was superior to HOMEX in patients with traumatic ASDs. SINEX Program was focused on neuromuscular exercises with movement quality feedback by supervision from physical therapists. The neuromuscular program included strength, coordination, balance, and proprioception exercises. Treatment was a 12 weeks program, individually tailored and supervised, progressing shoulder exercise and functional kinetic chain exercises. It included 7 exercises targeting the glenohumeral and scapular muscles, with 7 progression levels (basic to elite). Exercises followed general strength training principles, with basic and elite levels referring to low and high load exercises.

A 2018 study "The effects of a conservative rehabilitation program for multidirectional instability (MDI) of the shoulder" evaluated the effectiveness of a physiotherapy-led exercise program for participants with MDI. The rehabilitation program focused on regaining stability and control of muscles acting on the glenohumeral joint and scapulothoracic joints and gradually progressing the shoulder into functional positions and activities. The program, which has been published in detail, required participants to attend rehabilitation once weekly for 12 weeks. The results "identified improvement in functional status, shoulder muscle strength, and scapular positioning after rehabilitation" highlighting the value of conservative management of MDI.

Exercise therapy after Bankart and reverse Bankart.

Following surgery, a shoulder immobilizer was worn for 3 weeks.

Isometric exercise in the sling was started at 1 day postoperatively. Increasing range of motion exercises were prescribed for 2 weeks after surgery.

• The shoulder immobilizer was removed, and active flexion exercise in the supine position and passive external rotation exercise were started at 3 weeks postoperatively.
• Rotator cuff exercise was started using a rubber band at 4 weeks postoperatively, and unlimited activities of daily living were allowed at 6 weeks postoperatively.
• Upper limb muscle training was permitted using a <2kg dumbbell at 2 months, and push-ups were permitted at 3 months.
• Noncontact sports were permitted at 2 to 3 months, and contact sports and overhead throwing were permitted at 6 months.

Posterior shoulder instability is divided dimensionally: unidirectionally (posterior), bidirectionally (posteroinferior), and multidirectionally (posterior, inferior, and anterior). Bidirectional and multidirectional instability being the most common. Multidirectional instability may have an inciting traumatic event, but it is due to preexisting global capsular laxity. Conservative physiotherapy management is the primary option for treatment. If conservative treatment is unsuccessful after a 6-month course, surgery may be considered.

• For the first month, the shoulder should be kept in relative external or neutral rotation to relax the posterior capsule and antevert itself.
• Between the first and second months’ postsurgery, passive and active assisted range of motion can begin in a protected fashion while still limiting end ranges of motion in positions that maximally stress the posterior capsule.
• The sling use may be discontinued around 6 weeks.
• Between 2 and 5 months, strengthening can begin with isometrics for the rotator cuff and periscapular muscles.
• Full motion should be achieved between 2 and 3 months.
• Between months 5 and 8, patients may begin gradual return to previous sports, activities, and work duties but under controlled conditions.
• Full return depends on full functional range of motion, no pain or tenderness, good strength, and satisfactory clinical examination..

Post-Op Physical Therapy Management

Depends on:

• Surgical procedure
• Surgeon’s protocol 
• Mechanism of injury 
• Concomitant injuries 
• Tissue quality
• Impairments noted at evaluation

This 4 minutes video gives some examples of exercises for shoulder instability.

Rehabilitation Of Posterior Shoulder stabilization

• Posterior shoulder stabilization is done in the patients of posterior shoulder instability who failed conservative management.

Phase One - Protection Phase

Goals

To reduce pain, edema, restore the movement of accessory joint and educate the patient.

Rehabilitation

Postoperative Day 1 to Day 15. Protection Phase.

• The first visit of physiotherapy includes history taking, assessing the postoperative status, and establish functional goals.
• Surgical findings such as the procedure, postoperative restrictions, rehabilitation protocol, and prognosis are reviewed.
• The plan of care is prepared by the physiotherapist along with the inputs from the surgeon.
• The limb is immobilized with a sling and abduction pillow placing the limb in the scaption plane.
• Cryotherapy is to be applied five to six times a day to reduce pain , spasm, and edema.
• Active range of motion is applied on other joints of the body and postural education is provided.
• Usually, passive range of motion is initiated after 2 weeks with prior permission from the surgeon.
• PROM is limited to 120 degrees of flexion, 90 degrees of abduction, internal rotation till the abdomen, and external rotation till 30 degrees.
• Isometrics of rotator cuff and scapulothoracic muscles to improve the dynamic joint stability.
• Isometrics can be prescribed as home program and the patient can use wall as the resistance. Submaximal amount of force is used in the initial sessions.

Criteria to progress to AROM and muscle endurance(phase 2)

• PROM mentioned above has to be fulfilled inorder to ensure proper stability of GH joint.
• Patient should be able to perform scapular clock exercise while using minimal substitution. Clock exercise includes protraction, retraction, elevation and depression of scapula.
• Pain level has to be 3/10.
• The score of Quick DASH score has to be less than 60%.

Postoperative phase TWO (Active Motion and Endurance Phase) (Day 16 to Day 44)

• The goal of this phase is to achieve AROM and improve the strength of rotator cuff and periscapular muscles.

• Active assisted range of motion exercises are started initially with progression to Active ROM exercises.
• At first, the active-assisted ROM is done in a supine or prone lying position to minimize the effect of gravity then progressed to sitting position followed by standing as per the tolerance of the patient.
• Active assisted ROM is done by using normal extremity or lightweight wooden dowel within the surgical restrictions.
• For more function involvement, standing forward flexion with support can be started. This can be prescribed as a home exercise program and the patient can do it with dowel or ski pole and progress it in multiple planes.

Active Range Of Motion Exercises( After 6 weeks)

• This is initiated when the patient can perform isometrics and AAROM exercises with minimum compensatory movements and minimal pain.
• The sling is removed.
• It is commenced in supine position and progressed to standing as the firing of the muscles is improved.

It is important to activate the RC properly as it enhances the dynamic stability of the shoulder and prevents impingement by restricting abnormal superior translation of humeral head.

Criteria for progression to Initial resistance strengthening

Pain <3/10 during active ROM

Quick DASH score <40%

AROM : Flexion 120degrees, Abduction 120degrees, External Rotation 45 degrees

Posses normal scapula movements

Ability to perform the following motions at least for 20 repetitions without fatigue:

• Elevation up to 90 degrees in scaption plane

• Abduction upto 90 degrees

• Side-lying external rotation to zero degrees

Criteria for progression to advanced strengthening

Quick DASH <20%

AROM of flexion, abduction and external rotation > 90% as compared to contralateral side.

>80%on hand held dynamometer in all the planes of the shoulder joint.

Clinical Bottom Line

Shoulder instability may have a traumatic or atraumatic cause. There is a high recurrence rate after a primary shoulder dislocation, which is greatest in individuals < 20 years old. Rehabilitation should be based on each individual patient’s case with consideration to the type of surgery and surgeon’s preference where surgery is undertaken.