Rotator Cuff and Tendon Flashcards
(36 cards)
What are the four muscles of the rotator cuff?
Supraspinatus, Infraspinatus, Teres Minor and Subscapular
What is the function of the rotator cuff muscles as a whole?
They form a sleeve around the shoulder (Gleno-humeral) joint, compressing the humeral head into the glenoid cavity. They also provide stability for the joint.
Origin, Insertion, Innervation and Action: Supraspinatus
Origin: supraspinous fossa of scapula and deep fascia covering the muscle
Insertion: Greater tubule of the humerus
Innervation: Suprascapular Nerve (C5-C6)
Action: initiates first 15 degrees of abduction
Origin, Insertion, Innervation and Action: Infraspinatus
Origin: Infraspinous fossa of scapula and deep fascia covering muscle
Insertion: Greater tubule of humerus
Innervation: Suprascapular nerve (C5-C6)
Function: External/Lateral rotation
Origin, Insertion, Innervation and Action: Teres Minor
Origin: Lateral border of scapula
Insertion: Greater tubule of humerus
Innervation: Axillary Nerve (C5-C6)
Action: External/Lateral rotation
Origin, Insertion, Innervation and Action: Subscapularis
Origin: Subscapular fossa on scapula
Insertion: Lesser tubule of humerus
Innervation: Upper and lower suscapular nerves from posterior cord of brachial plexus
Action: Internal/Medial rotation
Tests for each muscle
Range of movement:
- Supraspinatus; forward elevation / aduction
- Infraspinatus & Teres Minor; external rotation with elbows at side
- Subscapularis; Internal rotation i.e. thumb behind back
Strength:
- Supraspinatus; Arms out in lateral plane, ‘don’t let me push arms down’
- Infra/TM; Arms tucked in and resisted external rotation
- Subscapularis; Belly press or push hands off back
What is the function of tendons?
- Attach bones to muscle
- Connective tissue transmitting mechanical force of muscle contraction to the bones
What is responsible for the strength of tendons?
High tensile strength necessary to withstand stress of contraction
- Attributes to hierarchical structure, parallel orientation and tissue composition of tendon fibres (Collagen Type I)
What connections are made by tendons?
One muscle has 2 tendons; proximal and distil
- Where tendon attaches to muscle; musculotendinous junction
- Where tendon attaches to bone; osteotendinous junction
- Proximal attachment; origin and distil attachment; insertion
What can be said about tendons attached to muscles generating a lot of power?
The tendons will be shorter and wider than those performing more delicate movements (long and thin)
Describe the hierarchical structure of tendons.
- 3 collagen fibres make tropocollagen
- 5 tropocollagen bound together form microfibrils
- Microfibrils surrounded by an endotenon sheath in bundles to give primary fibre bundles
- P. fibre bundles group to give secondary fibre bundles
- S. fibre bundles grouped into a fascicle
- Tendon; groups of fascicles bound by interior endotenon sheath and and exterior sheath of connective tissue (epitenon)
- All bounded by paratenon
What is the composition of tendons?
- Sparsely vascularised dense connective tissue
- 20% Cellular (mostly tenocytes and fibroblasts)
- 80% ECM (70% water, 30% solids i.e. Collagen Type I&III, elastin)
Function of tenoblasts in tendons.
Immature tendon cells, all different in shape and size, that elongate and become spindle shaped as they age - turning to tenocytes
Function of tenocytes in tendons.
- Responsible for maintaining the turnover of ECM
- Respond to mechanical load of tendon and adapt accordingly
- Arranged in longitudinal rows for communication with adjacent cells through gap junctions
Describe the extra-cellular matrix of tendons.
Mainly Type I collagen fibres and proteoglycan (viscoelastic nature - stretch with strain and regain original shape again)
What happens to the fascicles as we age?
They are small in diameter in children and grow in size until the age 20-29.
Then diameter gets smaller (linked to decrease in muscle strength)
- Diameter can also shrink if tendon gets damaged)
How are tendons innervated?
- Cutaneous, peritendinous and muscular nerves from the moyotendinous cross and enter the endotenon.
- In paratenon; nerve fibres form rich plexuses and send branches to penetrate the epitenon.
- Majority of nerve fibres terminate and reside on tendon surface.
- Myelinated nerve endings for sensing tension and pressure and unmyelinateud for sensing and transmitting pain.
What are the two types of blood supply to the tendon?
- Intrinsic; at MTJ/OTJ i.e. origin and insertion points.
- Extrinsic; synovial sheath supplying mid-tendon.
- Important for tendon healing.
What are the 3 phases of tendon healing?
- Inflammation (Day 0-7)
- Repair (Day 3-60)
- Remodelling (Day 28-180)
Under the action of cytokines and other mediators (PDGF and TGFBeta)
Name and describe the first phase of tendon healing.
Inflammation
- Erythrocytes, platelets and inflammatory cells (e.g. neutrophils, monocytes, macrophages) migrate from the epitendinous tissues (sheath, periosteum, soft tissues) and the epitendon and endotendon
- They clean site of dead materials by phagocytosis
- Also release phaso-active and chemo-tactic factors recruiting tendon fibroblast to begin collagen synthesis and deposition
- Matrix proteins are laid down as scaffolding for collagen synthesis
Name and describe the second phase of tendon healing.
Fibroblasts/Tenocytes migrate to injury zone and synthesise collagen Type III which is laid down in a random orientation.
4th week;
- Intrinsic fibroblasts proliferate and these take over the healing process to synthesise and reabsorb collagen.
- Production switched to Type I
Name and describe the third phase of tendon healing.
Remodelling
- Final stability acquired by normal physiological use of the tendon
- Paired with cross-linking between fibrils to further increase tensile strength
- Complete regeneration never achieved (thinner collagen fibres and defect remains hypercellular)
What are the benefits of patient rehab?
- Early controlled mobilisation will reduce scar adhesions and stimulates remodelling i.e. facilitates healing
- Excessive loading would disrupt repair tissue
- Optimal healing requires; surgery and mechanical stabilisation, minimal soft tissue damage and a good healing environment.
