Musculoskeletal Growth/Injury and Repair

Question 1

Why do bones fail?

Answer 1

High energy transfer in normal bones
Repetitive stress in normal bones (stress fracture)
Low energy transfer in abnormal bones (Osteoporosis, osteomalacia, metastatic tumour, other bone disorders)

Question 2

What are the four stages of fracture repair?

Answer 2

Inflammation
Soft callus
Hard callus
Bone remodelling

Question 3

Does bone scar?

Answer 3

No

Question 4

Stage 1 of bone repair: inflammation

Answer 4

Begins immediately after fracture
Hematoma and fibrin clot
Platelets, PMN’s, Neutrophils, Monocytes, Macrophages
By products of cell death – lysosomal enzymes
Fibroblasts
Mesenchymal & Osteoprogenitor cells
Angiogenesis

Question 5

When does soft callus begin?

Answer 5

When pain and swelling subside

Question 6

How long does soft callus formation last?

Answer 6

Until bony fragments are united by cartilage or fibrous tissue

Question 7

Hard callus

Answer 7

Conversion of cartilage to woven bone

“Secondary” bone healing - natural

Question 8

Bone remodelling

Answer 8

Converson of woven bone to lamellar bone

Medullary canal is reconstituted

Question 9

What is delayed union?

Answer 9

Failure to heal in expected time

Question 10

Delayed union causes

Answer 10

High energy injury
Instability
Infection
Steroids
Immune suppressants
Smoking
Warfarin
NSAID

Question 11

What is non union?

Answer 11

Failure to heal

Question 12

What is a peripheral nerve

Answer 12

The part of a spinal nerve distal to the nerve roots.
Bundles of nerve fibres.
Range in diameter from 0.3-22 μm

Question 13

What surrounds a peripheral nerve?

Answer 13

Schwann cells

Question 14

Structure of a nerve

Answer 14

AXONS coated with ENDONEURIUM grouped into FASCICLES (nerve bundles) covered with PERINEURIUM; grouped to form the NERVE which is covered in EPINEURIUM

Question 15

Types of nerve injury

Answer 15

Compression
Trauma - direct (blow, laceration)
Indirect (avulsion, traction)
Neurapraxia
Axonotmesis
Neurotmesis

Question 16

Causes of nerve compression

Answer 16

Entrapment
Classical conditions =>
Carpal tunnel syndrome (median nerve at wrist)
Sciatica (spinal root by intervertebral disc)
Morton’s neuroma (digital nerve in 2nd or 3rd web space of forefoot)

Question 17

What is neurapraxia?

Answer 17

Nerve in continuity
Stretched or bruised
Reversible conduction block - local ischaemia and demyelination
Prognosis good

Question 18

Axonotmesis

Answer 18

Endoneurium intact - tube in continuity, but disruption of axons; more severe injury
Stretched ++ or crushed or direct blow
Prognosis fair (sensory recovery often better than motor)

Question 19

Can peripheral nerves regenerate?

Answer 19

Yes

Question 20

What is neurotmesis?

Answer 20

Complete nerve division
Laceration or avulsion
No recovery unless repaired (by direct suturing or grafting)
Endoneural tubes disrupted so high chance of “miswiring” during regeneration
Prognosis poor

Question 21

What are closed nerve injuries?

Answer 21

Associated with nerve injuries in continuity

Question 22

Nerve injuries in continuity

Answer 22

Neuropraxis

Axonotmesis

Question 23

Closed nerve injuries management

Answer 23

Spontaneous recovery possible

Surgery indicated after 3 months

Question 24

What are open nerve injuries?

Answer 24

Frequently related to nerve division

Neurotmetic injuries

Question 25

Management of open nerve injuries

Answer 25

Early surgery | Distal portion of the nerve undergoes Wallerian degeneration

Question 26

What is Wallerian degeneration?

Answer 26

The axonal skeleton disintegrates, and the axonal membrane breaks apart. Axonal degeneration is followed by degradation of the myelin sheath and infiltration by macrophages. The macrophages, accompanied by Schwann cells, serve to clear the debris from the degeneration

Question 27

What are the main clinical features of nerve injury?

Answer 27

Sensory Motor Reflexes

Question 28

What are the clinical features of nerve injury? | Sensory

Answer 28

Dysaethesiae (disordered sensation) - anaesthetic (numb) - hypo- & hyper-aesthetic - paraesthetic (pins & needles)

Question 29

What are the clinical features of nerve injury? | Motor

Answer 29

``` Paresis (weakness) or paralysis ± wasting Dry skin (loss of tactile adherence since sudomotor nerve fibres not stimulating sweat glands in skin) ```

Question 30

What are the clinical features of nerve injury? | reflexes

Answer 30

Diminished or absent

Question 31

How does healing of injured nerves begin?

Answer 31

Initial death of axons distal to the site of injury Wallerian degeneration Then degradation of myelin sheath Proximal axonal budding occurs after about 4 days

Question 32

What is the rate of regeneration?

Answer 32

About 1 mm/day

Question 33

What is the first modality to return after nerve injury

Answer 33

Pain

Question 34

Is prognosis better for a distal or proximal lesion? (nerve injury)

Answer 34

Distal

Question 35

What is Tinel's sign?

Answer 35

Tap over site of nerve and paraesthesia will be felt as far distally as regeneration has progressed

Question 36

Direct nerve repair

Answer 36

``` Laceration No loss nerve tissue Microscope/Loupes Bundle repair Growth factors ```

Question 37

What is the rule of three (nerve injury)

Answer 37

Immediate surgery within 3 days for clean and sharp injuries Early surgery within 3 weeks for blunt/contusion injuries Delayed surgery, performed 3 months after injury, for closed injuries

Question 38

Tendon injury

Answer 38

``` Degeneration Inflammation Enthesiopathy Avulsion ± bone fragment Tear - rupture Tear - musculotendinous junction Laceration Crush Nodules ```

Question 39

Degeneration of tendon

Answer 39

eg Achilles tendon - Intrasubstance mucoid degeneration - May be swollen, painful, tender; may be asymptomatic - Precursor to rupture

Question 40

Inflammation of tendon

Answer 40

eg de Quervain’s stenosing tenovaginitis - Tendons of EPB + APL passing through common tendon sheath at radial aspect of wrist - Swollen, tender, hot, red - Positive Finklestein’s test

Question 41

Enthesiopathy

Answer 41

Inflammation at insertion to bone

Question 42

Avulsion ± bone fragment

Answer 42

Failure at insertion Load exceeding failure strength while muscle contracting Mallet finger

Question 43

What is mallet finger?

Answer 43

Insertion of extensor tendon into dorsum of base of distal phalanx of finger Forced flexion of extended finger

Question 44

Avulsion treatment

Answer 44

``` Conservative -Retraction tendon Operative -Reattachment tendon -Fixation bone fragment ```

Question 45

Tendon rupture treatment

Answer 45

``` Conservative -Mobilise (partial rupture) -Splint/cast Operative -High risk rerupture -High Activity -Ends cannot be opposed ```

Question 46

Acute knee pain small child differential diagnosis

Answer 46

``` Acute septic arthritis Trauma Acute inflammatory arthritis Transient synovitis Rheumatic fever Haemophilia Soft tissue infection ```