Rotator cuff injury Flashcards
What muscles make up the rotator cuff?
Supraspinatus
Infraspinatus
Subscapualris
Teres minor
Why are the rotator cuff muscles important?
For shoulder movement and stability of the shoulder joint.
What is the origin, insertion/attachment and function of the Supraspinatus muscle?
Supraspinous fossa of scapula
Greater tubercle of humerus
Assists deltoid in abducting the shoulder joint
What is the origin, insertion/attachment and function of the Infraspinatus muscle?
InfraspinOUS fossa of scapula
Greater tubercle of humerus
Laterally rotates arm at shoulder joint
what muscle initiates abduction of the shoulder?
Deltoid
What is the origin, insertion/attachment and function of the teres minor muscle?
Inferior lateral border of the scapula
Greater tubercle of humerus
lateral rotation of arm and extends arm at shoulder joint
What is the origin, insertion/attachment and function of the subscapularis muscle?
Subscapular fossa of the scapula
Lesser tubercle of humerus
Internal rotation of shoulder joint
which rotator cuff muscle is most anterior?
Subscapularis
What is a tendon?
A band of dense, fibrous connective tissue that connects skeletal muscles to bone.
What is the function of tendons?
Transmits mechanical force of muscle contraction to the bones
What are the 2 main structural divisions/components of tendons and what percentages do the make up?
Cellular component: 20%
Extracellular component: 80%
what do tendons attach to ?
fascia of muscle and periosteum of bones
what makes up the cellular part of tendons? what is their function?What shape are they?
tenocytes/fibroblasts: synthesise ECM
They are spindle shaped
what are tenoblasts?
immature tendon cells which turn into tenocytes
What are the divisions of the EC component of tendons?
70% = water 30% = type 1 and 3 collagen, ground substance, elastin
Describe how the collagen in tendons is arranged and its vascularity
Arranged as parallel fibres in direction of force
Sparsely vascularised
Explain the arrangement of tendons
Collagen fibrils = triple helix polypeptide chain, make up a collagen fibre
Collagen fibres make up Primary fibre bundle (sub fascicle).
Sub fascicles make up a secondary fibre bundle (fascicle)
Fascicles make up a tertiary fibre bundle.
Tertiary fibre bundles make up a tendon.
What is a paratenon?
Sheath of connective tissue that acts as an elastic sleeve
What does epitenon cover?
Covers the whole tendon
What does the endotenon cover?
Endotenon covers the primary, secondary and tertiary fibre bundles
What are the 3 phases of tendon healing? How long does each stage last for?
Inflammation (day 0-7)
Repair (day 3-60)
Organisation and remodelling (day 28-180)
Describe the inflammation stage of tendon healing
Inflammatory cells migrate form the epitendinous tissues (sheath, periosteum, soft tissues), and the epitendon and endotendon.
Defect is rapidly filled with granulation tissue, haematoma (blood clot) and tissue debris.
MAtrix proteins lay down the scaffolding for collagen synthesis.
EXTRA: (MMPs degrade the ECM) Chemotactic and vasoactive factors are released to recruit more inflammatory cells, proliferation of tenocytes, increase vascular permeability and initiate angiogenesis.
Describe the repair stage of tendon healing
Tenocytes migrate to the wound site and begin to synthesise type 3 collagen and ECM components ON DAY 5. It is laid down in random orientation.
On week 4, intrinsic fibroblasts proliferate and these cells take over the healing process both synthesising and reabsorbing collagen. = tendon callus
Tenocytes switch to synthesis of type 1 collagen which is increasingly orientated along lines of force.
Vascular ingrowth via collagen scaffolding occurs.
Describe the remodelling/organisation stage of tendon healing
Final stability is acquired through normal physiological use of the tendon. Also, there is cross linking of collagen fibrils which increases tendon tensile strength.
Tendons never return to pre-injury strength: thinner collagen fibrils and defect remains hypercellular (excess cells)
What cytokines are involved in tendon healing? what do they do?
PDGF - stimulates the production of other growth factors TGF Beta (transforming growth factor Beta) - aids ECM deposition
what is the most common rotator cuff tear?
Supraspinatus
Describe the difference between acute and chronic tendon problems
Acute: due to injury/trauma. such as a fall or lifting something heavy suddenly or awkwardly
Chronic: micro trauma and wearing down of tendon due to overuse. Usually found in older people (over 40)
What are the signs and symptoms of rotator cuff tears?
Dull ache deep in the shoulder Disturbed sleep - pain at night, especially when lying on affected shoulder Pain in overhead activities Weakness of muscle Shoulder stiffness
Describe the diagnosis of rotator cuff tears
Clinical examination - strength tests and rotator cuff tests
X-Rays - to check for sclerosis and osteophyte formation on the acromian
MRI
Ultrasound
Describe the management of rotator cuff injury
Painkillers Active rest: avoid movements that could worsen injury/pain Physiotherapy Steroid injections Surgery - open or arthroscopy
How can steroid injections help?
Reduce swelling, pain and stiffness
why do tendons have high tensile strength?
high proportion of collagen
collagen is closely packed in parallel arrangement in direction of force.
