Musculoskeletal Growth, Injury and Repair Flashcards
1
Q
What are the main anatomical components of a long bone?
A
Diaphysis - haematopoietic tissues Metaphysis - flare at end of shaft Epiphysis - on joint side of physis Physis - growth plate Medullary canal
2
Q
Why is the diaphysis follow?
A
To increase diameter and strength but keep the bone light
3
Q
What centres are particularly important in bone growth?
A
Ossification centres
4
Q
What does cortical bone e.g. the diaphysis resist?
A
Bending and torsion
5
Q
What are the features of cortical bone?
A
Laid down circumferentially
Less biologically active
Made up of tubes with blood vessels in the middle
Contains osteocytes
Always remodelling without affecting the whole bone
6
Q
What does cancellous bone e.g. the metaphysis resist?
A
Resists/absorbs compression
7
Q
What are the features of cancellous bone?
A
Site of longitudinal growth
Very biologically active
8
Q
What is a fracture?
A
Any break in the structural continuity of bone
May be a crack, break, split, crumpling or buckle
9
Q
What is the shorthand sign for a fracture?
A
#
10
Q
What energy is needed to cause normal bones to fracture?
A
High energy transfer - takes a lot of energy in a normal bone to cause a fracture, energy applied in an unexpected way
Or repetitive stress e.g. stress fractures in athletes
11
Q
What energy is needed to cause abnormal bones to fracture?
A
Only low energy transfer required to fracture an abnormal bone e.g. a bone with osteoporosis, osteomalacia, metastatic tumour, other bone disorders etc.
The older you get, the less energy it takes to cause a fracture
12
Q
What is the general biological effect of a fracture?
A
Mechanical and structural failure of bone
Disruption of blood supply
Regenerative process - no scar, four stages
13
Q
What is critical for the progression of fracture healing?
A
Mechanical properties of tissues and there environment
14
Q
What is involved in stage 1 of the regenerative process following a fracture?
A
Begins immediately after fracture
Haematoma and fibrin clot form immediately
Platelets, PMNs, neutrophils, monocytes and macrophages produce
Lysosomal enzymes
Fibroblasts
15
Q
What is the role of mesenchymal and osteoprogenitor cells in the regenerative process following a fracture?
A
Transformed endothelial cells from the medullary canal and/or periosteum
Osteogenic induction of cells from muscle and soft tissues
16
Q
How does angiogenesis occur following a fracture?
A
Oxygen gradient is required in normal bone, this is low in fractures
Macrophages produce angiogenic factors under hypoxic conditions
17
Q
What can have an effect on stage 1 of the regenerative process?
A
NSAIDs
Loss of haematoma e.g. surgery or open fractures
Extensive tissue damage and poor blood supply
18
Q
What is stage 2 of the regenerative process following a fracture?
A
Soft callus formation
19
Q
What is involved in stage 2?
A
Provides some stability of the fracture - fibroblasts produce collagen around the fracture which prevents shortening of the fracture
Angulation can still occur
Continued increase in vascularity
20
Q
When does stage 2 begin and end?
A
Begins when pain and swelling subside
Lasts until bony fragments are united by cartilage or fibrous tissue
21
Q
What can have effects on stage 2?
A
Replacing cartilage e.g. DMB
Bone graft
Bone substitutes
22
Q
What are the features of autogenous cancellous bone graft?
A
Gold standard, best choice for majority of bone graft needs
Osteoconductive or osteoinductive
23
Q
What are the types of allograft bone grafts?
A
Cortical Cancellous Fresh Prepared Structural Osteoconductive Non-osteoconductive
24
Q
What does allograft bone carry a risk of?
A
Disease transmission from donor to recipient
25
What is stage 3 of the regenerative process following a fracture?
Hard callus formation
26
What is involved in stage 3?
Conversion of cartilage to woven bone
Typical long bone fracture - endochondral bone formation and membranous bone formation
Increasing rigidity - secondary bone healing, obvious callus
Although bone is healing it cannot take normal load
27
What is stage 4 of the regenerative process following a fracture?
Bone remodelling
28
What is involved in stage 4?
Conversion of woven bone to lamellar bone
Extra bone is removed as far as possible
Medullary canal is reconstructed
Bone responds to loading characteristics
29
How does strain affect bone healing?
Degree of instability is best expressed as magnitude of strain
If strain is too low, mechanical induction of tissue differentiation fails
If strain is too high, the healing process does not progress to bone formation
30
What is delayed union?
Failure to heal in the expected time
31
What are the causes of delayed union?
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High energy injury
Distraction
Instability
Infection
Steroids
Immunosuppression
Smoking
Warfarin
NSAIDs
Ciprofloxacin
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32
What is the effect of smoking on union?
50% extension to union
33
What is non-union?
Failure to heal
34
What are the causes of non-union?
```
Failure of calcification of fibrocartilage
Usually due to instability
Abundant callus formation
Pain and tenderness
Persistent fracture line
Sclerosis
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35
What should be considered in delayed healing?
Alternative management:
- different fixation
- dynamisation
- bone grafting
36
What are the features of ligaments?
Dense bands of collagenous tissue
Span a joint
Anchored to the bone at either end
Joint stability through a range of motions
Different portions of the ligament are tensioned at different joint positions
37
What is the structure of ligaments?
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Collagen fibres - type 1
Fibroblasts - communication
Sensory fibres - proprioception, stretch and sensory
Vessels
Crimping - allows stretch
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38
What is the difference of percentage of collagen, proteoglycans and water, organisation of collagen fibres and shape of fibroblasts between tendons and ligaments?
Ligaments have
- lower percentage of collagen
- higher percentage of proteoglycans and water
- less organised collagen fibres and rounder fibroblasts
39
What causes ligament rupture?
When forces applied to the ligament exceed the strength of the ligament - can be complete or incomplete
40
What needs to be considered in ligament rupture?
Effects on the stability of the joint and proprioception loss
41
What is involved in the healing of ligaments?
Haemorrhage
Proliferative phase
Remodelling
42
What are the features of haemorrhage in the healing of a ligament rupture?
Blood clot reabsorbed
Replaced with a heavy cellular infiltrate
Hypertrophic vascular response
43
What are the features of the proliferative phase of healing of a ligament rupture?
Production of scar tissue
| Disorganised collagenous connective tissue
44
What are the features of remodelling in the healing of a ligament rupture?
Matrix becomes more ligament-like
| Major differences in composition, architecture and function persists
45
What are the treatment options for ligament injury?
Conservative
- partial
- no instability
- poor candidate for surgery
Operative
- instability
- expectation e.g. athletes
- compulsory, multiple e.g. knee dislocation
46
Where is the motor unit (efferent) located?
Anterior horn cell located in the grey matter of the spinal cord
Motor axon and muscle fibres
47
Where is the sensory unit located?
Cell bodies in the posterior root ganglia (i.e. outside the spinal cord)
48
Nerve fibres join to form what?
Anterior (ventral) motor roots
| Posterior (dorsal) sensory roots
49
What combines to form a spinal nerve?
Anterior and posterior roots
50
How do spinal nerves exit the vertebral column?
Via an intervertebral foramen
51
What are the features of peripheral nerves?
The part of a spinal nerve distal to the nerve roots
Bundles of nerve fibres
Range in diameter from 0.3-22um
Schwann cells form a thin cytoplasmic tube around them
Larger fibres arranged in a multi-layered insulating membrane myelin sheath
Multiple layers of connective tissue surrounding the axons
52
What are peripheral nerves composed of?
Highly organised structures comprised of nerve fibres, blood vessels and connective tissue
53
What are axons coated with?
Endoneurium
54
What are axons grouped into?
Fascicles
55
What are fascicles covered with?
Perineurium
56
What are fascicles grouped into?
Grouped to form the nerve
57
What is the nerve covered with?
Epineurium
58
What are the functions of group IA and IB (A-alpha) afferents?
Large motor axons
Muscle stretch
Tension sensory axons
59
What are the functions of group II (A-beta) afferents?
Touch, pressure, vibration and joint position sensory axons
60
What are the functions of A-gamma fibres?
Gamma efferent motor axons
61
What are the functions of group III (A-delta) afferents?
Sharp pain, very light touch and temperature sensation
62
What are the functions of B fibres?
Sympathetic preganglionic motor axons
63
What are the functions of group IV (C fibres) afferents?
Dull, aching, burning pain and temperature sensation
64
How can peripheral nerves be injured?
Compression
Trauma e.g. direct blow, laceration, avulsion
Neurapraxia, axonotmesis, neurotmesis
65
When might peripheral nerves become compressed?
Entrapment
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 foot
66
What is neurapraxia?
Temporary loss of sensory and motor function due to blockage of nerve conduction - local ischaemia and demyelination, reversible conduction block
Good prognosis
67
What is axonotmesis?
Damage to a peripheral nerve where disruption of the axons occurs, but endoneurium, perineurium and epineurium remain intact
Wallerian degeneration follows
68
What causes axonotmesis?
Nerve stretched (15% elongation disrupts axons), crushed or a direct blow
69
What causes neurapraxia?
Nerve stretched or bruised
70
What is the prognosis of axonotmesis?
Fair - sensory recovery often better than motor
| Often not returned to normal but returned enough to recognise pain, temperature and sharp and blunt objects
71
What is neurotmesis?
Complete nerve division - both the nerve and the nerve sheath are disrupted
Endoneural tubes disrupted so high chance of mis-wiring during regeneration
72
What causes neurotmesis?
Laceration or avulsion
73
What is the prognosis of neurotmesis?
Poor prognosis
| No recovery unless repaired, either by direct suturing or grafting
74
What are closed nerve injuries associated with?
Nerve injuries in continuity - classically neuropraxia or axonotmesis
75
When is surgery indicated for closed nerve injuries?
After 3 months if no recovery is identified (clinical, electromyography)
76
What is the axonal growth rate?
1-3mm/day
77
Give an example of a closed nerve injury
Brachial plexus injuries
| Radial nerve in humeral fracture
78
What are open nerve injuries usually associated with?
Laceration
| Frequently related to nerve division - neurotmetic injuries e.g. knives, glass
79
How are open nerve injuries treated?
With early surgery
80
At what point does Wallerian degeneration occur?
2-3 weeks after the injury
81
What are the sensory clinical features of nerve injury?
Dysaesthesiae
Anaesthesia
Hypo/hyper-aesthetic
Paraesthetic
82
What are the motor clinical features of nerve injury?
```
Paresis or paralysis +/- wasting
Dry skin (loss of tactile adherence since sudomotor nerve fibres are not stimulating the sweat glands in skin)
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83
What are the reflex clinical features of nerve injury?
Diminished or absent reflexes
84
What are the features of healing of a nerve injury?
Very slow
Starts with initial death of axons distal to site of injury (Wallerian degeneration), then the degradation of the myelin sheath
Proximal axonal budding after about 4 days
85
What is the rate of the regeneration process of a nerve injury?
1mm/day
86
What is the first modality to return in the healing of a nerve injury?
Pain
87
What does the prognosis for recovery from a nerve injury depend on?
Whether the nerve is pure or mixed, and how distal the lesion is
Prognosis is worse with more proximal lesions
88
What sign can be used to monitor recovery?
Tinel's sign - tap over the site of the nerve and parasthesia will be felt as far distally as regeneration has progressed
89
How can nerve injury be assessed and recovery monitored?
By electrophysiological nerve conduction studies
90
When is direct repair of a nerve injury indicated?
Laceration
| No loss of nerve tissue
91
What are the methods of direct repair for a nerve injury?
Microscope/Loupes
Bundle repair
Growth factors
92
When is nerve grafting indicated?
Nerve loss
| Late repair - retraction, sural nerve
93
What is the 'rule of three' - surgical timing in traumatic peripheral nerve injury?
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
94
What are the examination findings of an UMN lesion?
```
Decreased strength
Increased tone
Increased deep tendon reflexes
Clonus present
Babinski's sign present
Atrophy absent
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95
What are the examination findings of a LMN lesion?
```
Decreased strength
Decreased tone
Decreased deep tendon reflexes
Clonus absent
Babinski's sign absent
Atrophy present
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96
What is the structure of the muscle/tendon composite unit?
```
Muscle origin from bone
Muscle belly
Musculotendinous junction
Tendon
Tendinous insertion into bone
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97
What is the anatomy of a tendon?
Longitudinal arrangement of cells and fibres, orientated along the line of stress
Fascicles of long, narrow, spiralling collagen bundles
Collagen bundles covered by endotenon
Fascicles covered by paratenon
Tendon covered by epitenon
98
What is the blood supply to tendons?
Needs to come from outside - rather than running through the middle, this allows tendons to move without damaging blood supply
Viniculum
Fine network of blood vessels in the paratenon
99
How are tendons connected to the tendon sheath?
By vincula, synovial lining and fluid
100
What do thickenings of the tendon sheath form?
Strong annular pulleys, where tendons have to move round an angle
101
What are the functions of tendons?
Flexible and very strong in tension
| Movement of the limb in order to enable function
102
What does immobility cause in tendons?
Immobility reduces water content and glycosaminoglycan concentration and strength
103
What are the types of tendon injury?
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Degeneration
Inflammation
Enthesiopathy
Traction apophysitis
Avulsion +/- bone fragment
Tear - intrasubstance or musculotendinous
Laceration/incision
Crush, ischaemia or attrition
Nodules
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104
What are the features of degeneration of a tendon?
Intra-substance mucoid degeneration
May be swollen, painful, tender or asymptomatic
Possible precursor to rupture
Rheumatoid arthritis should be considered
105
What are the features of inflammation of a tendon?
Swollen, tender, hot and red
| Positive Finklestein's test
106
What are the features of enthesiopathy of a tendon?
Inflammation at insertion to bone
Usually at muscle origin rather than tendon insertion
Common extensor origin
Tennis elbow - classic presentation
107
What are the features of traction apophysitis?
Insertion of patellar tendon into anterior tibial tuberosity
Common in adolescent active boys
Recurrent load
Bone hypertrophies, inflammation occurs
Painful
No cure or treatment other than reducing activity
108
What are the features of avulsion +/- bone fragment?
Failure at insertion
| Load exceeding failure while muscle contracts
109
What is the treatment for avulsion?
Conservative
- if you can, get tendon ends to re-join
- limited application
- retraction tendon
Operative
- reattachment of tendon, normally through bone
- fixation bone fragment
110
What causes intrasubstance rupture?
Tear
| Load exceeds failure strength
111
What is the mechanism of rupture?
53% - pushing off with weight bearing forefoot whilst extending knee joint
17% - unexpected dorsiflexion of ankle
10% - violent dorsiflexion of plantar flexed foot
112
What are the features of Achilles tendon rupture?
Positive Simmond's test
| Palpable tender gap
113
What is the treatment of tendon rupture?
Conservative
- where ends can be opposed, mobilise, splint/cast
- where healing will occur
Operative
- high risk of re-rupture
- high activity
- where ends cannot be opposed
114
Why is there no chance of re-joining finger tendons following laceration?
Tendon end retracts as soon as it is lacerated
115
What is the treatment of laceration?
Repair surgically and early
