Shoulder Flashcards
What is the shoulder? Is it stable? Why?
- Glenohumeral joint
- It’s exceptionally mobile but very unstable
- There is poor bony congruence hence stability relies heavily on muscles, ligaments and brain to coordinate muscle patterns
- The humeral head sits within glenoid fossa, which is deepened by the glenoid labrum
- The capsule and Extracapsular ligaments function to restrain translation of humeral head within glenoid
- Muscle patterning moves the shoulder with force pairs where the agonist is the primary mover and the antagonist opposes it to prevent subluxation and dislocation
- When we move the shoulder, proprioceptive fibres in the capsule and muscles are activated and send signals to the brain
- The brain then sends a reflexive signal back to the antagonist, which will contract and bring the humeral head back to the centre of the glenoid
What is the glenohumeral joint?
-Surface area of humeral head is 4x larger than glenoid fossa hence humeral head and glenoid cavity have a small contact area hence easy to dislocate
Has glenoid labrum
- fibrocartilage
- triangular cross section
- 50% of glenohumeral depth is provided by labrum
- attachment to underlying bone are loose;superior portion is congruent with long head of biceps brachii tendon
What are the features of the proximal humerus?
- Head articulates with glenoid fossa
- Anatomical neck
- Surgical neck (axillary nerve and posterior circumflex arteries are here)
- Greater tubercle (lateral)
- Smaller tubercle (medial)
- Intertubercular groove (bicipital groove)
- Deltoid tuberosity
- Spiral groove (radial nerve and profunda brachi are here)
What are the movements of the shoulder?
- Flexion-extension
- Abduction-addiction
- Internal and external rotation
-Occurs in sagittal and coronal plane
Flexion = 167-171 degrees Extension = 45-60 degrees
What is the anatomy of the clavicle?
- S shaped double curve
- Protects underlying brachial plexus and vascular structure
- Elevates with upper limb elevation
- Transmit forces
Sternal end
- impression for costoclavicular ligament
- there are anterior and posterior costoclavicular ligaments which is attached to 1st rib costal cartilage to anterior and posterior aspects of clavicle. Resists superior clavicle displacement and anterior/posterior translation
Acromium end
- Conoid tubercle = for conoid ligament (medial aspect of coracoclavicular ligament)
- Trapezoid line = for trapezoid ligament (lateral aspect of coracoclavicular ligament)
What is costoclavicular ligament?
- Anterior and posterior
- Attached to 1st rib costal cartilage to anterior and posterior part of clavicle
- Resists super displacement
- Limits anterior and posterior translation
What are the conoid ligament and trapezoid ligament (coracoclavicular ligament)?
-Support scapula and stabilise against thorax
Conoid ligament:
- Runs from coracoid process to Conoid tubercle
- Restrains axial rotation and posterior translation of clavicle
Trapezoid ligament:
- Runs from coracoid process to trapezoid line
- Resists axial compression around a horizontal axis
What are the clavicular joints?
- Sternoclavicular joint: between sternal end of clavicle and manubrium
- Acromioclavicular joint: between acromium and acromial end clavicle
What is the sternoclavicular joint?
- Saddle shaped synovial joint
- Articular surfaces are covered by fibrocartilage
- Allows clavicle and sternum to slide over allowing rotation and movement
- Only bony connection of upper limb to thorax
- 4 degrees of clavicular rotation occurs for every 10 degrees of arm elevation at this joint
- Permits anterior, posterior, vertical movement and limited rotation
Ligaments involved
- Interclaviclar ligament = spans gap between sternal ends of each clavicle
- Costoclavicular ligament = anterior and posterior. From costal cartilage of 1st rib to anterior and posterior aspect of clavicle. Resists superior clavicle displacement; limits anterior and posterior translation
- Capsular ligament = forms anterior and posterior sternoclavicular ligaments. Stabilises the joint and prohibits excess displacement
What movement occur at the sternoclavicular joint?
- Elevation (shrugging, abduction at 90 degrees’
- Depression (drooping, extending shoulder behind body)
- Protraction and retraction
- Rotation
What is the acromioclavicular joint?
- Planar synovial joint
- May rotate up to 35 degrees at maximal shoulder abduction
- Both aspects of joint is covered with fibrocartilage
- Joint slopes infero-medially causing the clavicle to override acromium
- Allows axial rotation
- No muscles directly act at this joint so supported by scapulothoracic articulations
Ligaments: They prevent displacement
-Acromioclavicular ligaments = covers joint capsule. Restrains axial rotation and posterior translation of clavicle
-Coracoclavicular ligaments = Conoid and trapezoid ligament.
Conoid ligament: restrains axial rotation and posterior translation
Trapezoid ligament: resists axial compression around horizontal axis
-Coracoacromial ligament = confers stability to unstable joint
What are the ligaments of the sternoclavicular joint and acromioclavicular joint?
Sternoclavicular joint:
- Interclavicular ligament
- Costoclavicular ligament (anterior and posterior)
- Capsule ligament (sternoclavicular ligaments - anterior and posterior)
Acromioclavicular joint:
- Acromioclavicular ligament (covers joint capsule)
- Coracoclavicular ligament (Conoid and trapezoid)
- Coracoacromial ligament
What is fibrous capsule?
- Loose outerfibrous layer
- Inner synovial membrane (secretes synovial fluid which fills the joint capsule)
- Allows joint laxity and range of motion
Attachment points
- Glenoid labrum
- Anatomical neck
- Base coracoid process
Tightens during abduction, adduction, external and internal rotation
Posterior capsule:
-secondary restraint to anterior dislocation —> stabilises structure
What are the glenohumeral ligaments?
- Coracohumeral ligament
2. Glenohumeral ligament
What is the coracohumeral ligament?
- Reinforces superior aspect of capsule
- Prevents inferior displacement of humerus
- More important in individuals with less developed superior glenohumeral ligament
What is the glenohumeral joint?
Superior:
- Only well developed in 50% of people.
- Main restraint to inferior translation with arm in adductor position
Middle:
- Absent in 30% of shoulders
- Secondary restraint to inferior translation in abducted and externally rotated position
- Restrains anterior translation
Inferior:
- Has anterior band, posterior compartment and axillary pouch
- Anterior band = tightens in abduction and external rotation
- Posterior component = tightens with abduction and internal rotation
- Axillary pouch = allows abduction, flexion and extension
Inferior band limits:
- anterior translation
- posterior translation
- inferior translation
What are the important muscles here?
Outermost layer:
- Deltoid (anterior, middle and posterior fibres)
- Pec major (sternoclavicular head and clavicular head)
- Pec minor (scapular stabiliser)
Innermost layer:
-Rotator cuffs (infraspinatus, supraspinatus, subscapularis, teres minor)
What are the roles of the outermost muscles?
Deltoid = flexor, internal rotator and abductor of humerus
Supply: axillary nerve, deltoid and acromial branches of thoracoacromial artery + Subscapular artery
Pec major = rotates, flexes and extends humerus
Supply: medial and lateral pectoral nerves, pectoral branches of thoracoacromial artery and internal thoracic artery
Pec minor = scapula stabiliser
Supply: medial and lateral pectoral nerves, thoracoacromial artery
What are the roles of the deeper muscles?
-Deep layers abduct and rotate humerus and allow glenohumeral stabilisation. Create compressive forces
-Supraspinatus = forms forced couple with deltoid for abduction of humerus
Supply: subscapular nerve
-Infraspinatus and teres minor = external rotators of humerus
Supply: subscapular nerve
-Subscapularis = internal rotation of humerus
Supply: upper and lower subscapular nerves
What is the accessory muscles?
- Trapezius = elevates, retract, rotate scapula
- Lat dorsi = extends, adductor and internally rotate humerus
- Levator scapulae = elevate and interior rotate scapula
- Rhomboid major and minor = retract and rotate scapula
- Teres major = arm adduction and internal rotation
- Biceps brachii = flexes and supinate forearm. Elevates and depresses humerus
What are the features of the scapula?
- Glenoid fossa
- Supraglenoid tubercle (origin of long head of biceps brachi)
- Infraglenoid tubercle (origin of long head of triceps brachi)
- Spine (separates supraspinous and infraspinous fossa)
- Supraspinous fossa
- Infraspinous fossa
- Scapular notch
- subscapluaris
-Scapulothoracic articulation
What is the scapulothoracic articulauton?
- Sternoclavicular joint
- Acromioclavicular joint
Allows mobility around scapula.
Scapula moves by gliding against chest wall
Ranges of motion:
- protraction/abduct (20degrees)
- retraction/adduct (15 degrees)
- elevation (40 degrees)
- depression (10degrees)
- internal rotation (30 degrees)
- external rotation (60 degrees)
What are the scapulothoracic movements?
- Protraction = serratus anterior, pec minor
- Retraction = rhomboid major, minor and trapezius
- Elevation = levator scapulae, trapezius
- Depression = trapezius, lat dorsi
- Scapular rotation
What are the shoulder movements?
Flexion (anterior humeral elevation):
- Male = 167 degrees
- Female = 171 degrees
Extension (highest point you can lift your arm to the back)
-45 degrees to 60 degrees
Abduction
-limited by impingement of of greater tuberosity and acromium
Adduction
Internal and external rotation
What muscles are involved in forward elevation?
Supraspinatus and deltoid
What muscles are involved in depression?
Infraspinatus, teres minor and subscapularis
What muscles are involved in abduction?
Agonist: supraspinatus, trapezius
Syngergist: deltoid
What muscles are involved in adduction?
-Lat dorsi, pec major
What muscles are involved in flexion?
Deltoid, pec major, biceps, pec major
What muscles are involved in extension?
-Lat dorsi, deltoid and pec major
What is the Stanmore triangle?
- If shoulder becomes unstable, it can do so in several ways that are summarised by the Stanmore triangle
- It defines 3 polar types of instability
Type 1 (traumatic structural instability):
- traumatic structural instability
- this is where trauma damages the joint architecture, leading to excessive translation of humeral head within glenoid
- a force pushes the humeral head in one direction (usually anteriorly) and the glenoid labrum is torn off
- the humeral head then dislocates and knocks into the edge of the glenoid
- Since humeral head is soft and glenoid is hard, it often results in a compression fracture of humeral head called a Hills-Sachs lesion
- If you sustain traumatic dislocation once, it’s likely you will have a detached labrum because the avascular nature of cartilage nature means it’s bad at healing itself
- There will be lack of congruency
- On MRI we can see detached labrum which will affect ligaments and capsule
- The overall result is that structures of the shoulder are now loose and less effective at keeping humeral head centred
- This means that the next time the shoulder takes a hit, the proprioceptive information is sent to the brain but before the brain can send a signal back to the brain to re-centre the humeral head, it dislocates as there’s nothing passive to stop it popping out
- This will keep occurring unless the labrum is reattached
Type 2 (atraumatic structural):
- atraumatic structural instability
- This is hypermobility due to lax labrum and capsule
- The humeral head can translate a lot more than normal, as a result, it can potentially dislocate
- If it doesn’t dislocate, it will have a feeling of instability
Type 3 (muscle patterning):
- Proprioceptive issues and defective muscle patterning
- These people are often known as voluntary dislocators
- We rely on muscles (which act in force pairs) for shoulder stability
- Proprioception and subsequent reflective muscle patterning usually mean agonist and antagonist produce equal and opposite forces keeping the humeral head centred in the glenoid
- E.g pec major draws shoulder anteriorly whilst subscapularis draws head of humerus in the opposite direction, preventing anterior translation. As scapula retracts, pec major relaxes, otherwise it pulls the humeral head anteriorly. If pec major doesn’t relax, it pulls humeral head anteriorly whilst subscapularis retracts the scapula, pulling the glenoid posteriorly. This means the pec major essentially pulls the humeral head out of the glenoid
- It leads to multiple dislocations without structural damage
What is type 1 (traumatic structural instability)?
Type 1 (traumatic structural instability):
- traumatic structural instability
- this is where trauma damages the joint architecture, leading to excessive translation of humeral head within glenoid
- a force pushes the humeral head in one direction (usually anteriorly) and the glenoid labrum is torn off
- the humeral head then dislocates and knocks into the edge of the glenoid
- Since humeral head is soft and glenoid is hard, it often results in a compression fracture of humeral head called a Hills-Sachs lesion
- If you sustain traumatic dislocation once, it’s likely you will have a detached labrum because the avascular nature of cartilage nature means it’s bad at healing itself
- There will be lack of congruency
- On MRI we can see detached labrum which will affect ligaments and capsule
- The overall result is that structures of the shoulder are now loose and less effective at keeping humeral head centred
- This means that the next time the shoulder takes a hit, the proprioceptive information is sent to the brain but before the brain can send a signal back to the brain to re-centre the humeral head, it dislocates as there’s nothing passive to stop it popping out
- This will keep occurring unless the labrum is reattached
What is type 2 (atraumatic structural)?
Type 2 (atraumatic structural):
- atraumatic structural instability
- This is hypermobility due to lax labrum and capsule
- The humeral head can translate a lot more than normal, as a result, it can potentially dislocate
- If it doesn’t dislocate, it will have a feeling of instability
What is type 3 (muscle patterning)?
Type 3 (muscle patterning):
- Proprioceptive issues and defective muscle patterning
- These people are often known as voluntary dislocators
- We rely on muscles (which act in force pairs) for shoulder stability
- Proprioception and subsequent reflective muscle patterning usually mean agonist and antagonist produce equal and opposite forces keeping the humeral head centred in the glenoid
- E.g pec major draws shoulder anteriorly whilst subscapularis draws head of humerus in the opposite direction, preventing anterior translation. As scapula retracts, pec major relaxes, otherwise it pulls the humeral head anteriorly. If pec major doesn’t relax, it pulls humeral head anteriorly whilst subscapularis retracts the scapula, pulling the glenoid posteriorly. This means the pec major essentially pulls the humeral head out of the glenoid
- It leads to multiple dislocations without structural damage
What is Stanmore classification as a continuum?
- Patients can move between different types of instability
- If a patient starts off with a type 1 dislocation but it reoccurs, the joint capsule and ligaments will stretch out so they may become more of a type 2
- Patient may be aware of tendency for their shoulder to dislocate or proprioceptive pathways may become damaged, leading to type 3
- You can go from type 3 to type 1 as dislocations damage the joint architecture
- You can go from type 3 to type 2 as dislocations and lack of muscle patterning cause joint capsule and ligaments to become lax over time
- We need to diagnose which part is causing the most issues - this determines treatment approach
How would you treat shoulder instability?
- Surgery can only treat abnormal anatomy such as type 1 and type 2. Surgery would make type 3 worse
- Patient suffering from type 1 issue (labra tear or Hills-Sachs lesion), you can do labral repair and bony reconstruction of humeral head
- Patient suffering from type 2 issue (lax and loose), you can do capsular shift to attempt to tighten up the joint capsule and ligaments
- Patient suffering both type 1 and type 2, you can perform a labral repair and capsular shift
- Patient with type 3, do physiotherapy to help coordinate correct muscle patterns
Note: if you try and operate on a type 3, you will destroy normal anatomy so follow up physiotherapy will be useless - it will just result in more dislocations
What is arthroscopic stabilisation for a labral tear?
- Labral tears in type 1 stability can be approached with a labral repair
- This can be done arthroscopically
- Firstly, where the bone was attached to labrum is cleaned up and irritated so that it bleeds
- It needs to bleed because things stick to bleeding bone (remember bleeding is the first stage in tissue healing)
- A Kevlar stitch is then passed through the labrum before a small hole is drilled into the bone
- The stitch is then attached to an anchor which is subsequently driven into the hole of the bone
- The loose ends of the stitch are then cut and another 2-3 stitches are done
- This essentially pulls the detached labrum back down to the surface of the glenoid
What is the function of the rotator cuffs?
-Function to centralise the axis of rotation whilst other muscles of the shoulder girdle act on the humerus
- Deltoid attaches to acromium and deltoid tuberosity of humerus - as a result, it can only pull the humeral head superiorly until it hits the acromium
- When it hits the acromium, it then has a fixed point to rotate around, although bone rubbing on bone is not pleasant
- This is when the rotator cuffs come in - it pulls the humeral head medially into the glenoid which counteracts the upward pull of the deltoid
- The result is that deltoid now pulls the arm into abduction as the action of the rotator cuffs fixes the point of rotation
What is rotator cuff impingement?
- Clinical diagnosis where greater tuberosity catches on underside of acromium
- This can happen due to e.g anatomy (overgrown acromium reduced the subcromial space), weak or uncoordinated rotator cuffs allowing humeral head to ride up towards acromium when deltoid contacts, weak scapula muscles allowing humerus to ride up
Presentation:
- patients are often 40+
- if they’re young, it’s more likely to be instability not impingement
- complain of pain in lateral arm over deltoid area
- clinical tests will point to impingement
Treatment:
- reduce pain using analgesics
- steroid injections to reduce inflammation
- physiotherapy - can help balance rotator cuffs and strengthen scapula muscles
- if this fails , do surgery called subacromial decompression
What is surgical decompression?
- Usually done arthroscopically
- Patient is anaesthetised
- Arm in traction
- Subacromial space is pumped with fluid - this distracts the space
- A shaver is used to tidy up the overlying bone and detach the Coracoacromial ligament (which has no clear function)
- The bone is exposed and a grinder is introduced from the posterior aspect
- This is used to shave off small parts of the acromium to make it smoother and create some more space in the subacromial space
What is a rotator cuff tear?
- Tears affecting rotator cuff tendon, but it’s normally the avascular supraspinatus tendon
- As tears get bigger, they go into infraspinatus, though teres minor is rarely affected
- Tears are detachment of muscle tendon from the bone
- They start small and progress, peeling from bone
Causes:
- degenerative. Happens with age. Can be symptomatic or asymptomatic
- traumatic. Affect younger patients. Can be caused by slipping on ice and landing on lateral aspect of arm which forces adduction. The rotator cuff pulls in the opposite direction and something fails in the middle. Always symptomatic
Presentation:
- 40+ years
- anterosuperior muscular pain
- clinical tests indicate tear as opposed to impingement
Treatment:
- similar to rotator cuff impingement
- pain - this can be helped with analgesics
- steroid injections to help with inflammation
- physiotherapy
What is rotator cuff repair?
If a patient has a 2cm tear in the supraspinatus tendon, we operate as follows:
- look at tear arthroscopically
- we will not put the tendon back exactly where it came from as the muscle belly will retract the tendon
- we will remove the separated distal end of the tendon
- we then use a burr to make the bone bleed at the attachment site
- kelvar stitches are then fired through the tendon and pulled tight reducing the tendon over the bone
- a hole is then made in the bone and the stitch is anchored with a screw
- the tails of the stitch are then cut and the repair is done
- the weak point in this whole situation is the tendon
- it is likely to re-tear if too much load is put through it
- hence rehab involved 4 weeks in a sling is required and no load bearing for 8 weeks
- Recovery takes 6-9 months
What are the clinical examinations?
- a thorough history
- expose the patient
- inspect front and back e.g scars (open or arthroscopic), muscle wasting (deltoid or supraspinatus), deformity (clavicular fractures, ACJ dislocation)
- Palpate the clavicle, ACJ, greater tuberosity, long head of biceps
- Range of motion - flexion, extension, abduction, rotation
Special tests:
- Instability
- laxity - sulcus sign (tests for inferior glenohumeral instability), anterior and posterior draw
- anterior apprehension test
- relocation test - Impingement
- Neer’s sign
- Hawkin’s test
- Jobe’s test - Rotator cuffs
- external rotation lag sign
- hornblower’s sign (infraspinatus and teres minor)
- internal rotation lag sign
- liftoff test (subscapularis)
- These tests have high sensitivity but poor specificity
What are Neer’s sign, Hawkin’s sign and Jobe’s sign?
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