MSK - growth, injury and repair Flashcards
Give a brief description of a ligament
dense bands of collagenous tissue which are anchored to bone at each end and allow joint stability
Type of collagen fibres in ligaments
1
5 components of the structure of a ligament
type 1 collagen vessels at the surface fibroblasts sensory fibres crimping to allow stretch
4 differences in ligaments compared to tendons
less % of collagen and less organised
higher % of proteoglycans and water
rounder fibroblasts
When does ligament rupture occur?
when forces exceed the strength of ligament
3 phases of ligament healing
haemorrhage
proliferative phase
remodelling
Describe the haemorrhage stage of ligament healing
blood clot
replaced with heavy cellular infiltrate
hypertrophic vascular response
describe proliferative phase of ligament healing
scar tissue
disorganised collagenous connective tissue
describe the remodelling of ligament healing
matrix becomes more ligament like
major differences persist
Treatment of ligament rupture and reasons for this
conservative if partial/no instability/poor candidate
operative –> replace or augmentation
–> expectation ie sportsman, instable or compulsory/multiple
Where is cortical bone found in a bone?
diaphysis
what does cortical bone resist?
bending and tension
How is cortical bone laid down?
circumferentially
Is cortical or cancellous bone more biologically active?
cancellous
Where in a bone is cancellous bone found?
metaphysis
What does cancellous bone resist?
compression
sign for a fracture
#
3 reasons why bones fail
high energy transfer in normal bones
repetitive stress in normal bones –> stress fracture
low energy transfer in abnormal bones eg osteoporosis
4 stages of fracture regeneration
inflammation
soft callus
hard callus
bone remodelling
Inflammation in fracture healing brief description
occurs immediately after with a haematoma and fibrin clot
platelets, PMN, neutrophils, MO, monocytes
What are the by products of cell death in stage 1 of fracture healing?
lysosomal enzymes
Where are mesenchymal and osteoprogenitor cells derived?
transformed endothelial cells from medullary canal and or periosteum
Requirement for angiogenesis and macrophages producing angiogenic factors
low oxygen gradient
hypoxic conditions
How may we affect the inflammation phase of fracture healing?
NSAIDs
loss haematoma - open fractures and surgery
extensive tissue damage - poor blood supply
4 growth factors in buffy coat platelet concentrates
IGF
VEGF
TGF-B
PDGF
When does soft callus of fracture healing begin and end?
when pain and swelling subside
bony fragments united by collagen/fibrous tissue
angulation
abnormal bend
How might we affect soft callus phase?
replace cartilage
jump straight to bone - graft
Is autogenous cancellous bone graft osteoinductive or conductive?
both
Is allograft bone osteoconductive or inductive?
osteoconductive
Risk of allograft bone
disease transmission
Brief description of hard callus
cartilage –> woven bone
endochondral and membranous bone formation
Bone remodelling
woven bone –> lamellar bone
What law does bone remodelling follow?
wolff’s
Best way to express instability
magnitude of strain - % change of initial dimension
What happens if strain is too low?
mechanical induction of tissue differentiation fails
What happens if strain is too high?
healing process does not progress to bone formation
10 things which can lead to delayed union
instability NSAIDs warfarin ciprofloxacin smoking steroids high energy injury distraction infection immune suppressants
6 reasons for non union
failure of calcification fibrocartilage instability --> increased osteoclasis pain and tenderness abundant callus formation sclerosis persistent fracture line
3 alternatives if healing delayed
different fixation
bone graft
dynamization
Fibres named when tendon inserts into bone
sharpeys fibres
Arrangement of tenocytes
longitudinal
collagen type in tendon
1
State which each of these is covered by
a- collagen bundles
b - fascicles
c - tendon
a = endotendon b = paratenon c = epitenon
How are tendon connected to sheath in flexor tendon in palm?
vincula
Thickenings of tendon sheath form?
annular pathways - pulleys
function of tendon sheath
flexible and very strong in tension
What does immobility do to water content and glycosaminoglycan concentration and strength?
reduce
Name 10 tendon injuries
degeneration nodules inflammation laceration/incision avulsion +/- bone fragment enthesiopathy ischaemia traction apophysitis tear - intrasubstance/rupture tear - musculotendinous junction
Tendon degeneration
mucoid degeneration
swollen, pain, tender or no symptoms
precursor to rupture
positive test in de Quervains stenosing tenovaginitis
finklestein
Where does enthesiopathy occur? eg..
muscle origin
common extensor origin at lateral humeral epicondyle - tennis elbow
traction apohpysitis example and explain
Osgood schatters disease
insertion of patellar tendon into anterior tibial tuberosity
active adolescent boys
recurrent load and inflammation
When does avulsion occur
failure at insertion when load > fail strength when muscle contracting
Mallet finger
insertion of extensor tendon - fixed flexion
Treatment of mallet finger
conservative = limited application, retraction tendon
surgery - reattach tendon through bone or fixation of bone fragment
When does intrasubstance rupture occur?
load > failure strength
ruptured achilles tendon
3 mechanisms of achilles rupture and explain
pushing off with weightbearing forefoot when extending knee joint eg jumping
unexpected dorsiflexion of ankle - slip into hole
violent dorsiflexion of plantarflexed foot eg fall from height
2 findings of achilles tendon rupture
positive Simmonds squeeze test
palpable tender gap
example of musculotendinous junction tear
medial head of gastrocnemius at musculotendinous junction with achilles tendon
treatment of musculotendinous junction tear
conservative
- where ends can be opposed mobilise of splint
- healing will occur
operative -high risk of rerupture, high activity and ends cannot be opposed
Finger flexor laceration
common in young adult males - need surgery early
motor unit
anterior horn cell in gray matter of spinal cord, motor axon and muscle fibres
sensory unit
cell bodies in posterior root ganglia
how do spinal nerves exit spinal cord?
intervertebral foramen
what are these coated with?
a - axons
b - fascicles
c - nerve
a - endoneurium
b - perineurium
c - epineurium
entrapment of nerve example
mortons neuroma - digital nerve in 2nd or 3rd web space of forefoot
classical nerve compression - 2 examples
sciatica
carpal tunnel syndrome
briefly describe neurapraxia
nerve in continuity and good prognosis
stretched or bruised
reversible conduction block
briefly describe axonotmesis
endoneurium intact but axons disrupted
stretched, crushed or direct blow
prognosis fair
sensory or motor more likely to recover?
sensory
Name for degeneration which follows axonotmesis?
wallerian
briefly describe neurotmesis
complete nerve division and no recovery unless repaired or graft
endoneural tube disruption
closed nerve injuries
neuropraxis and axonotmesis
spontaneous recovery possible - surgery after 3 months
axonal growth rate
1-3mm/day
example of closed nerve injury
brachial plexus injury
radial nerve humeral fracture
open nerve injury
eg knife, early surgery and distal proportion undergoes Wallerian degeneration 2/3 weeks after injury
sensory features of nerve injury
dysaesthesia - anaesthetic, hypo and hyper aesthetic, paraesthesia
motor features of nerve injury
paresis or paralysis and muscle weakness
dry skin
Why dry skin due to motor disruption?
loss of tactile adherence since sudomotor nerve fibres not stimulating sweat glands in skin
Healing of nerve injury - brief explanation
slow and starts with initial death of axons distal to injury
proximal axonal budding, 1mm/day
What returns first after nerve injury?
pain
3 things prognosis of nerve injury depends
how distal lesion is - proximal worse
nerve is pure ie sensory mixed
nerve mixed
What sign can monitor nerve injury recovery and explain
Tinels
tap over nerve and paraesthesia felt as distally as regeneration
How is nerve injury assessed and recovery monitored?
electrophysiology nerve conduction studies
direct nerve repair
laceration - no loss of nerve tissue
microscope - bundle repair and growth factors
Nerve grafting done when?
nerve loss and late repair (retraction)
sural nerve
rule of 3 - surgical timing in traumatic peripheral nerve injury
immediate surgery in 3 days - clean and sharp injury
3 weeks - blunt/contusion
delayed - closed injuries
