MSK Growth Injury and Repair Flashcards
What are the parts of the long bone
Diaphysis - shaft Metaphysic - fare at end of shaft Epiphysis - on joint side of physis Physis Growth - plate Medullary canal
In what part of a long bone is cortical bone found
Diaphysis
In what part of a long bone is cancellous bone found
Metaphysis
What does cortical bone resist
Bending and torsion
What does cancellous bone resist
Compression
How is cortical bone laid down
Circumferentially
What is cancellous bone the site of
Longitudinal bone growth (physis)
Is cortical or cancellous bone more biologically active
Cancellous bone is very biologically active
What are the stages or repair of a fracture
Inflammation
Soft callus formation
Hard callus formation
Bone remodelling
What happens in the inflammation stage of fracture healing
Haematoma and fibrin clot form
Angiogenesis
Cells Accumulate
Platelet Concentrate
What factors are needed for angiogenesis
Low oxygen gradient
Macrophages to produce angiogenic factors under hypoxic conditions
What iatrogenic factors can affect the inflammation stage of fracture healing
NSAIDs
Open #, Surgery - loss haematoma
Poor blood supply - extensive tissue damage
What cells accumulate in the inflammation stage of fracture repair
- Platelets
- PNMs
- Neutrophils
- Monocytes
- Macrophages
- Fibroblasts
- Mesenchymal and osteoprogenitor cells
What molecules are found in the platelet concentrates of inflammation in fracture healing
Platelet-derived growth factor (PDGF)
Transforming growth-factor-beta (TGF-B)
Insulin like growth factor (IGF)
Vascular endothelial growth factor (VEGF)
When does stage 2 of fracture healing begin
When pain and swelling subside until bony fragments are united by cartilage or fibrous tissue
How can the 2nd stage of fracture healing by affected
Replace cartilage with demineralised bone matrix
Bone graft
Autogenous cancellous bone graft
Allograft bone
What happens in the 3rd stage of fracture healing
Conversion of cartilage too woven bone
Increasing rigidity
What happens in the 4th stage of fracture healing
Conversion of woven bone to lamellar bone
Medullary canal is reconstituted
Bone responds to loading characteristics Wolff’s law
What is strain in relation to fractures
Expresses the degree of instability
- if strain is too low, mechanical induction of tissue differentiation fails
- If strain is too high, healing process does not progress to bone formation
Causes of delayed union
High energy injury Instability Infection Steroids Immune suppressants Smoking Warfarin NSAID Ciprofloxacin
What is delayed union
Failure to heal in expected time
What is non-union
Failure of fracture healing
Signs of non-union
Failure of calcification fibrocartilage Instability due to excessive osteoclasts Abundant callus formation Pain + tenderness Persistent fracture line Sclerosis
Alternative management for delayed healing
Different fixation
Dynamisation
Bone grafting
What is the structure of ligaments made up of
Collagen fibres (type 1) Fibroblasts (communicate) Sensory fibres - proprioception, stretch, sensory Vessels (at surface) Crimping (allow stretch)
How are ligaments different to tendons
Ligaments have:
- lower percentage of collagen
- high percentage of proteoglycans and water
- less organised collagen fibres
- rounder fibroblasts
What do you need to assess in ligament rupture
Complete vs incomplete
Stability of joint?
Proprioception loss?
What happens in ligament rupture healing
Haemorrhage
Proliferative phase
Remodelling
What happens in the haemorrhage stage of ligament healing
Blood clot forms
Resorbed
Replaced with a heavy cellular infiltrate
Hypertrophic vascular response
What happens in the proliferative phase of ligament healing
Production of scar tissue
Disorganised collagenous connective tissue
What happens in the remodelling phase of ligament healing
Matrix becomes more ligament like
Major differences in composition, architecture and function persist
Treatment of ligament rupture
Conservative - if partial, no instability or poor candidate for surgery
Operative - if unstable, expectation (sportsmen), or compulsory (multiple)
What fibres are found in the tendinous insertion into bone
Sharpey’s fibres
How are the cells and fibres of tendons arranged
Longitudinallarrangement of tenocytes and type I collagen
Fascicles of long narrow spiralling collagen bundles
What are the collagen bundles in tendons covered by
Endotendon
What are the fascicles in tendons covered by
Epitendon
What are tendons covered by
Epitenon
Where can the blood supply for tendons by found
In the paratenon
How are tendons connected to their tendon sheath
By a vincula
What happens in achilles tendon degeneration
Intrasubstance mucoid degeneration
May be swollen, painful, tender
Precursor to rupture
What happens in de Quervain’s stenosing tenovaginitis
Tendons of EPB and APL passing through common tendon sheath at radial aspect of wrist become inflamed
Causes swelling, tenderness, heat, redness
Positive Finklestein’s test
What is enthesiopathy
Inflammation at insertion to bone - can occur in a:
- muscle / tendon (usually at muscle origin rather than tendon insertion) - tennis elbow
- ligament - i.e. plantar fasciitis
What is traction apophysitis
i. e. Osgood Schlatter’s Disease
- inflammation in the insertion of patellar tendon into anterior tibial tuberosity
- occurs in adolescent active boys due to recurrent load
What is an avulsion fracture
An injury to the bone in a location where a tendon or ligament attaches to the bone
When an avulsion fracture occurs, the tendon / ligament pulls off a piece of the bone
Treatment of avulsion
Conservative
- limited application
- retraction tendon
Operative
- reattachment of tendon through bone
- fixation of bone fragment
What are the mechanism of an achilles tendon intrasubstance rupture
50% - Pushing off with weight bearing forefoot whilst extending the knee joint - i.e. sprint starts of jumping movements
15% - unexpected dorsiflexion of ankle (i.e. slipping into hole)
10% - violent dorsiflexion of plantar flexed foot i.e. fall from height
Signs of achilles tendon rupture
Positive simmonds test
Palpable tender gap
What is an example of a musculocutaneous junction tear
Medial head of gastrocnemius at musculotendinous junction with achilles tendon
Treatment of tendon rupture
Mobilise Splint Physio Steroid injection Operative - if high risk re-rupture, high activity, ends cannot be opposed
A alpha fibre
- size in microns
- speed (m/sec)
- function
- 15 microns
- 60-100 m/sec
- Large motor axons, muscle stretch and tension sensory axons
A beta fibres
- size in microns
- speed (m/sec)
- function
- 12-14 microns
- 30-60 m/sec
- touch, pressure, vibration and joint position sensory axons
A gamma fibres
- size in microns
- speed (m/sec)
- function
- 8-10 microns
- 15-30 m/sec
- gamma efferent motor axons
A delta fibres
- size in microns
- speed (m/sec)
- function
- 6-8 microns
- 10-15 m/sec
- sharp pain, very light touch and temperature sensation
B fibres
- size in microns
- speed (m/sec)
- function
- 2-5 microns
- 3-10 m/sec
- sympathetic preganglionic motor axons
C fibres
- size in microns
- speed (m/sec)
- function
- <1 microns
- <1.5 m/sec
- dull, aching, burning pain and temperature sensation
Common nerve compression syndromes
Carpal tunnel syndrome - median nerve at wrist
Sciatica - spinal root by IV disc
Mortons’ neuroma - digital nerve in 2nd or 3rd webspace of forefoot
What are axons of peripheral nerves covered in
Endoneurium
What are nerve fascicles covered with
Perineurium
What is a peripheral nerve covered with
Epineurium
What is the classification of nerve trauma
Sunderland
- Grade 1 - neurapraxia
- Grade 2 - axonotmesis
- Grade 3 - neurotmesis
- Grade 4 - neurotmesis +
- Grade 5 - neurotmesis ++
What is neurapraxia
Nerve is stretched or bruised but in continuity (endometrium intact)
Causes reversible conduction block (local ischaemia and demyelination)
Prognosis good - weeks-months
What is axonotmesis
Endoneurium intact but axons disrupted either by stretching, crushing or direct blow
Wallerian degeneration follows
Prognosis fair - sensory recovery better than motor
What is Wallerian degeneration
An active process of degeneration occurring when a nerve fibre is cut or crushed and part of the axon distal to the injury degenerates
What is neurotmesis
Complete nerve division due to laceration or avulsion
No recovery unless repaired operatively
Endoneural tubes disrupted so high chance of misfiring during regeneration
Poor prognosis
what are closed nerve injuries associated with
Nerve injuries in continuity - neuropraxis, axonotmesis
What are open nerve injuries associated with
Nerve division - neurotmetic injuries, knives or glass
Treatment of closed nerve injuries
Spontaneous recovery possible
Surgery after 3 months if no recovery seen clinically or by electromyography
Treatment of open nerve injuries
Early surgery
Sensory features of nerve injury
Dysaethesiae (disordered sensation)
- anaesthetic
- hypo / hyper aesthetic
- paraesthetic (pins and needles)
Motor features of nerve injury
Paresis (weakness) Paralysis Wasting Dry skin Diminished reflexes
Why does dry skin occur in nerve injury
Loss of tactile adherence as sudomotor nerve fibres not stimulating sweat glands in skin
What is the process of healing in a nerve injury
Wallerian degeneration Degradation of myelin sheath Proximal axonal budding - after ~4 days Regerenation at rate of 1mm/day / 1"/month Pain is first modality to return
What does prognosis of nerve injury depend on
Whether nerve is pure (only sensory or motor) or mixed (both sensory and motor within same nerve)
How distal the lesion is (proximal nerve)
What test and investigation can be done to monitor recovery of a nerve injury
Tinel’s test - tap over site of injury and paraesthesia will be felt as far distally as regeneration has progressed
Electrophysiological Nerve Conduction Studies
When would you use direct repair for a nerve injury
Laceration
No loss of nerve tissue
When would you use nerve grafting for a nerve injury
Where there is nerve loss
Use sural nerve
What is the rule of 3 in relation to surgical timing in a traumatic peripheral nerve injury
Immediate surgery within 3 days for clean and sharp injuries
Early surgery within 3 weeks for blunt contusion injury
Delayed surgery, after 3 months for closed injury
How is tone affected in UMN and LMN lesion
UMN - increased tone
LMN - decreased tone
How are deep tendon reflexes affected in UMN and LMN lesion
UMN - reflexes increased
LMN - reflexes decreased
How is clonus affected in UMN and LMN lesion
UMN - clonus present
LMN - clonus absent
How is babinski affected in UMN and LMN lesion
UMN - present
LMN - absent
How is atrophy affected in UMN and LMN lesion
UMN - absent
LMN - present
