The Shoulder Flashcards
What is the normal scapulohumeral rhythm?
2:1 humeral to scapular movement normally
What are the normal strength ratios of the shoulder?
IR:ER - 3 to 2 (IR is 50% stronger)
Add : Abd - 2 to 1 (adduction is 100% stronger)
Ext to flex: 5 to 4 (ext is 25% stronger than flex)
Which ligament limits ER with arm at the side and is usually contracted in shoulders with adhesive capsulitis?
Coracohumeral ligament (inserts into RC interval). Usually has to be released to regain full ER.
What is the RC interval?
Described by Neer as the capsular tissue interval between suscapularis and supraspinatus tendons. It is composed of parts of the supraspinatus and subscap tendons, the coracohumeral ligament, and the superior glenohumeral ligament. All of these structures contribute to stability by limiting inferior translation and ER when adducted, post translation when the arm is flexed
What are the 4 parts of the proximal humerus?
shaft, greater tuberosity, lesser tuberosity, articular or head segment. These corresponds to four ossification centers. The surgical neck is below the tuberosities, the anatomical neck is above. These 4 sections are common sites of fracture and are the basis of Neer’s classification of prox humerus fractures.
Describe the layers of the rotator cuff.
The rotator cuff has 5 layers at its superior portion at greater tubercle insertions.Variation in tissue properties/loads among these layers may contribute to RC tears.Basically layer 1 and 4 are coracohumeral ligaments, with layer 2 being the actual RC tendon and 3 being random orientation.fasicles. Layer 5 is the capsule itself.
Describe the anatomy of the supraspinatus tendon and its clinical significance.
Supraspinatus has 2 muscle bellies (ant and post). The anterior belly is larger and pulls through a smaller tendon area, meaning increase stress compared to posterior tendon. This is important during surgical repairs.
What does the long head of the biceps do?
Opinions vary. May contribute to anterior stability and help depress humeral head in the presence of large RC tear. Elbow flexion strength can dec by up to 30% and supination/abd up to 20% if a tear occurs due to loss of stabilizing function.
What is the labral origin of the bicep anchor?
40-60% of the origin is from the supraglenoid tubercle, while the remaining fibers originate from the glenoid labrum in various patterns.
What is the quadrangular space?
Antomic interval formed by the humeral shaft laterally, the long head of the triceps medially, the teres minor superiorly, and the teres major inferiorly. The axillary nerve and posterior circumflex humeral artery pass through here.
What is the triangular space?
An anatomic interval medial to the quadrangular space. Borders are formed by the long head of the triceps laterally, the teres minor superiorly, and the teres major inferiorly. The circumflex scapular artery (branch of scapular artery) passes through here.
How is the GHJ stability maintained?
Through both static and dynamic stabilizers. Statis structures include the capsule and ligaments and are normally lax during mid range, dec movement at extreme ranges. Dynamic is primarily the deltoid and RC and are more active at mid range.
What structure is the most important static restraint to anteiorr humeral translation in the 90-degree abd/ER position?
Anterior band of inferior glenohumeral ligament. This is the position most traumatic shoulder dislocations occur. The middle glenohumeral ligament is the restraint at mid range, while the superior ligament prevents excessive ER and inf translation with the arm by the side.
What is a Bankart lesion?
Detachment of the anchoring point of the anterior band of the inferior glenohumeral ligament and middle glenohumeral ligament from the glenoid rim (also the labrum) This is a result of a truamatic anterior dislocation. This is the opposite of the HAGL lesion. This can be treated by suturing the ligament and the labrum back to the glenoid.
What is a HAGL lesion?
Uncommon. Avulsion of the humeral attachement of the glenohumeral ligament after dislocation. Opposite of Bankart lesion.
What is a Hill-Sachs lesion?
An impression fracture of the posterolateral margin of the humeral head caused by impaction on the rim of the glenoid during anterior shoulder dislocation.
What is the function of the clavicle?
Acts as a strut to inc biomechanical efficiency of axiohumeral muscles.
Subclavius.
O: first rib
I: inferior middle third of clavicle
N: Nerve to Subclavius (C5, C6)
A: stabilizes sternoclavicular joint.
What is the primary areterial supply to humeral head?
Anterior circumflex artery. It ascends via the bicipital groove along with the LHB tendon.
Describe the course of the suprascapular nerve/
Arises from the superior trunk of the brachial plexus (C5, C6). Courses posteriorly to the suprascapular notch along with the artery. The nerve travels through the suprascapular notch, under the transverse scapular ligament, while the artery goes above. Next it passes through the spinoglenoid notch below the spinoglenoid ligament.
What neurovascular structure is at greates risk during anterior shoulder surgery?
Axillary nerve. It travels posteriorly from the post cord of the brachial plexus to innervate the deltoid and teres minor. It, along with the posterior circumflex humeral artery, passes below the inferior border of the subscap and travels along the inferior genohumeral joint capsule.
Which nerve lies superficial in the posterior cervical triangle and is susceptible to injury?
Spinal Accessory nerve (CN XI), just below cervial fascia. The post cervical triangle is borderd by the SCM anteriorly, the trap posteriorly, and the clavicle inferioly. May be injured during cervical lymp node biopsy. Will result in drooping of the shoulder, pain, and weakness in arm elevation.
Which nerve causes classical medial scapular winging?
Long Thoracic nerve
Describe the course of the musculocutaneous nerve.
Terminal branch of the lateral cord of the brachial plexus (C5,6,7). Penetrates coracobrachiallis and sends off motor branches. Travels between brachialis and biceps brachii, inervating both. Sensry branches emerge between the brachialis and brachioradialis muscles and travels into the forearm as the lateral antebrachial cutaneous nerve.
Is the acromial attachment of the coracoacromial ligament and anterior deltoid preserved during arthroscopic acromioplasty?
No, typically it is released. The overlying deltoid insertion remains attached by a bridge of tissue composed of periosteum and deltoid tendon.
Describe the anatomy of the pec major tendon and associated nerves.
The pec major insertion is aprpox 2 inches wide with a broad undersurface and small anterior surface. The sternal head spirals posterior, the clavicular anterior. The medial pec nerve is inferior to the lat pec nerve insertion. The lateral pectoral nerve passes medial to the pec minor befor entering the pec major, whereas the medial pec nerve passes through or lateral to pec minor befor entering pec major.
What are the main stabilizers of the AC joint?
The AC ligament and joint capsule are primary constraints for posterior displacement and rotation. Conoid ligament constrains anterior/superior rotation and displacement. The trapezoid ligament constrians vertical and horizontal displacement.
What is the articular version of the proximal humerus?
Typically 30 degrees of retroversion.
What is the normal version/tilt of the glenoid?
Approx 8 degrees of retroversion relative to the scapula. Relative to the body, it is oriented anteriorly. Excessive retroversion may contribute to posterior instability, while upward facing glenoids may inc RC disease risk.
What are the three morphologic types of the acromion?
Bigliani classified 3 types. Type 1 - Acromion is flat (17%) Type II - Acromion is curved (43%) Type III Acromion is hooked down (40%) Out of patients c RC tears, 70% have type III, 27% have type II, and 3% have type I. Types II and III impinge on RC tendons
Are types II and III acromia aquired or developmental?
Possibly aquiared. The hooks lie with in the coracoacromial ligament and may be traction spurs due to the humeral head pushing up on the arch.
Describe Neer’s RC pathology classification.
Stage 1: edema and hemorrhage; pt is less than 25 yo and have pain that resolves with rest. Reversible. Conservative Tx.
Stage 2: fibrosis and tendinitis. Patients typically 25-40 and have recurrent pain. Possibly consider SAD if conservative Tx fails.
Stage 3- Bone spur and tendon rupture. Pts typically older than 40 with history of progressive disability. RCR advised.
Stage 4- Pt typically older than 60. cuff tear arthropathy. RCR, TSA recommended
What is the coracoacromial arch and why is it important?
Formed by the coracoacromial ligament, it is the roof of the shoulder. Protects the subacromial bursa and RC tendons. Restricts excessive superior migration. With elevation and IR the greater tuberosity and RC tendons may compress against this.
What is a partial-thickness RC tear?
Naturally degenerates with increasing age, especially in 40s+. Degeneration begins deep within the tissue near the undersurface attachment of the tuberosity. Tears may also occur on the bursal side of the cuff near the insertion.
Do partial-thickness tears heal or progress to full-thickness tears?
Usually. Typically occurs because ruptured fibers can no longer sustain load so surrounding fibers have more stress. Disruption also disrupts local blood supply within the tendon. Disrupted fibers are exposed to joint fluid which has a lytic effect. If the tendon does heal, the scar tissue does not have the same tensile strength.
What is RC arthropathy?
With massive tearing, tendons slide off the humeral head. They then act as elevators and promote superior humeral head translation, causing excessive wear and degeneration. May lead to TSA or hemi-arthroplasty if it becomes severe enough.
When are acromioplasty and subacromial decompression required?
Typical patient is between 25-40 years old and has recurrent pain and failed conservative treatment. Some surgeons advocate retaining the coracoacromial ligament to preserve teh arch/superior migration.
What is the Mumford procedure?
An excision of the distal 2cm of the clavicle. Often used to allow greater RC decompression or to dec pain from AC dislocation.Distal stability of the scapula is maintained through the intact costoclavicular ligaments (conoid and trapezoid) since the AC joint no longer exists.
What are some primary RC exercises?
Supraspinatus: can be worked with prone Y’s
Teres minor: Prone ext with ER (T’s with thumbs up)
Subscapularis: IR can be performed any way.
What RC exercises result in the greatest EMG activity?
Sidelying ER results in greatest EMG activity of infraspinatus and Teres minor. Suprasinatus is greatest in prone Y’s with thumbs up, but this is an advanced exercise.
What is the difference between primary and secondary RC impingement?
Primary (structural) is a mechanical impingement of RC below coracoacromial arch and results from overcrowding.
Secondary is due to space being decreased because of instability/poor control
What is posterior (internal) impingement?
Pinching of the infraspinatus adn supraspinatus between teh posterior superior aspect of genoid and the upper limb, when in the cocked position (Throwing position). Occurs on the undersurface rather than the bursal side. May be associated c ant instability.
What classification is used to describe the extent or size of RC tears?
AAOS: small tear is <5
Stage 3 is 5 cm +
