Orthopaedics Flashcards
Which nerves and blood vessels does articular cartilage contain?
NONE
also relatively hypoxic
What effect do NSAIDs have on the COX pathway?
Inhibit it, therefore preventing the conversion of arachidonic acid to prostaglandin precursors (thus preventing pain)
In which 2 ways can be NSAIDs be administered?
Oral and systemic
How do corticosteroids prevent pain?
Inhibit IL-1, TNF-α, and prostaglandins
Alter signalling pathways and gene expression
What are the equine doses for MPA and TA (corticosteroids)?
MPA: 40-120mg/joint (total horses dose 160mg)
TA: 6-12mg/joint (total horses dose 18-20mg)
Which cytokine is involved with osteoarthritis?
IL-1
How do bisphosphates work?
Inhibit bone resorption (hence prevent loss of bone mass) by inhibiting osteoclasts:
- Competes with ATP, resulting in apoptosis
- Alters ‘rough’ border attachments
- Reduced recruitment of osteoblasts to osteoclasts
May also inhibit NO and IL-1 induced collagenase release in chondrocytes/synovial cells
What are the symptoms of immune-mediated joint disease?
Multiple limb joint pain/swelling, generalised stiffness, shifting lameness, neck pain, lethargy, PUO (pyrexia of unknown origin)
Secondary OA/ joint deformities in chronic cases
How might you diagnose immune-mediated joint disease?
Synoviocentesis
Full clinical exam
Anaemia, proteinuria, leucopenia, low albumin
Radiograph
How would you treat immune-mediated joint disease?
Corticosteroids
Explain the pathophysiology of infective arthritis (synovial sepsis)
Marked inflammatory response:
-Vasodilation and influx of neutrophils
-Release of IL-1 and TNF-a
Fibrin clots trap bacteria (protect bacteria, reduces synovial nutrient exchange)
Cartilage destruction and extension to subchondral bone
What are the clinical signs of infective arthritis?
Acute onset, severe lameness
Stiffness, lying down, pyrexia
Wound near/over joint
Pain on palpation/articular swelling
What is the difference between tendons and ligaments?
Tendons:
Passively transfer force generated by muscle to bony attachments, leading to movement
Support joints
Store energy
Ligaments:
Attach/stabilise bones/joints
Protect tendons
Proprioception
What is the difference in content of collagen type in tendons and ligaments?
Tendon= 95% collagen type I, 1-5% type III Ligament= 90% type 1, 10% type III
What are the causes of intrinsic and extrinsic tendon/ligament injuries?
Intrinsic: overload/degenerative
Extrinsic: external trauma
If a flexor tendon is damaged, what % of original function can be restored?
50% at best
What is PRP therapy?
Platelet-rich plasma therapy
Uses platelets from patient’s own blood to rebuild a damaged tendon or cartilage
Relieves pain and jump-starts healing process
How can we limit inflammation in horses with SDFT tendonitis?
Cold hosing
NSAIDs
Which cells proliferate/migrate during muscle repair?
Satellite/precursor
White muscle disease is caused by a deficiency in what?
Selenium/vitamin E
Which enzymes may be elevated with muscle disease?
What might you see in the urine?
AST/ CK
Myoglobinuria
Give a brief description of polysaccharide storage myopathy
Increased muscle uptake of glucose and synthesis of glycogen
Muscle stiffness, reluctance to exercise, poor performance
Avoid high-energy feeds (give low-carb, high fibre diets)
Which bacteria causes non-exertional rhabdomyolysis?
Clostridium
The fetlock joint is between which bones?
3rd metacarpal/metatarsal bone and P1
What is the white line of a cow’s hoof?
Junction between wall horn and sole horn
How does the pedal bone stay attached to the dermal lamellae?
This may be compromised by what?
Via collagen fibres
Increased activity of MMPs
What is the function of osteoblasts?
What do they develop into?
Form bone matrix
Osteocytes (maintain bone tissue)
What is the function of osteoclasts?
Bone resorption (breakdown of bone matrix)
What are the differences between woven and lamellar bone? (3)
Woven:
Fibrils 0.1-3um diameter (smaller)
Random arrangement
Highly mineralised
Lamellar:
Fibrils 2-3um (larger)
Arranged into sheets
Less highly mineralised
What are the functions of bones?
Skeletal support (movement, muscle attachment) Protection Haematopoesis Regulation of mineral homeostasis Fat storage
What is an osteon (Haversian system)?
Functional unit of bone. Cylindrical structure containing a central (Haversian) canal which contains a blood vessel. Osteocytes exist within their own lacunae. They make contact with each other via canaliculi (small canals) to participate in exchange of nutrients and metabolic waste.
What stimulates bone growth?
Genetic template
Hormones
Load
What stimulates bone adaptation?
Increase in load
Decrease in load
Repetitive load
Plastic deformation
What is meant by the word ‘physis’?
Growth plate
Adaptive response of bone depends on which 3 things?
Strain, magnitude, frequency
What are the advantages of bone remodelling?
Allows bones to change shape in response to compressive forces (increases ability to resist fracture)
Replacement of damaged bone
Prevents accumulation of fatigue damage (repairs micro-cracks)
Contributes to mineral homeostasis
How long does osteoid take to mineralise?
80-90 days
How long does bone resorption by osteoclasts take?
3-4 weeks at 40um/day
In which part of the bone do microcracks form?
Cortical bone
What is the difference between elastic and plastic deformation?
With elastic deformation, the bone deforms and returns to the original shape. With plastic deformation it does not, but remodelling is stimulated.
How does modelling of trabecular bone result in stronger bones?
Increased thickness of trabeculae
Increase in bridging between trabeculae
What impact does cyclic repetitive strain have on trabecular bone?
Microcracks in trabeculae
Resorption of trabecular bone:
Increased porosity and decreased strength
Collapse of subchondral bone under articular cartilage
Predisposition to fracture
What impact does exercise have on the third carpal bone?
Increased bone density
Increased density of trabecular bone
Increased microdamage and remodelling
Increased risk of fracture
What adaptations do bones have to racing? (horses and dogs)
Increase in bone mineral density
Increase in cortical thickness
How is a greyhound’s central tarsal bone adapted to racing?
Right central tarsal bone has a greater bone mineral density vs left (undergoes compression and rotation)
Dorsal aspect of bone undergoes adaptive remodelling-thickened and compacted trabeculae
Where is calcitonin released from?
Thyroid
In which 3 ways does calcitonin decrease blood calcium levels?
Increases calcium deposition in bones
Decreases calcium uptake in intestines
Decreases calcium resorption from urine
Give some examples of complications that may occur following a fracture
Contamination/infection
Damaged blood/nerve supply
Contralateral limb problems
Implant failure
What are the 5 zones of the physeal anatomy?
Resting cartilage Zone of proliferation Zone of hypertrophy Zone of calcification of cartilage Matrix resorption and ossification/secondary spongiosa
What does OCD stand for?
Osteochondrosis dessicans
Cartilaginous or osteochondral flap
What is meant by osteochondrosis?
Family of orthopaedic diseases
Abnormal endochondral ossification
Interruption of blood supply to bone -> bony necrosis -> regrowth of the bone
Abnormalities leading to OCD can occur at which different stages?
Disruption of blood supply
Abnormal chondrocyte maturation
Defective matrix production
Persistence of hypertrophic chondrocytes
How may hormones influence OCD?
Testosterone and growth hormones
Transient hyperinsulinaemia
Transient hypothyroidism (thyroid hormone influences chondrocyte maturation)
Growth factors (TGF-b, IGF-1, IGF-2: alter chondrocyte metabolism)
How may nutrition influence OCD?
Excess energy and protein
Imbalance of Ca:P (excess phosphorus is more influential)
Imbalance of Cu:Zn (Cu deficiency; Cu is involved in collagen cross-linking)
Which radiographic abnormalities might you see with OCD?
Irregular subchondral bone
Osseous densities:
-mineralised cartilage
-osteochondral fragments
What is physitis?
What are the clinical signs?
Enlargement of the physis (inflammation or disrupted endochondral ossification)
Lameness, stiff gait, self-limiting
Hypertrophic osteodystrophy typically affects which kinds of dogs?
Large breeds, 2-8 months old
Briefly describe the pathogenesis of hypertrophic osteodystophy
Necrosis of the capillary loops of the cartilage of the metaphyseal physis
Cuff of metaplastic cartilage and bone
What are the clinical signs of hypertrophic osteodystrophy?
Lameness, fever, lethary, painful bone
Primarily long bones – distal aspect
Bilateral and symmetric
Describe the radiographic abnormalities seen with hypertrophic osteodystrophy
Abnormal bone on diaphyseal side of physis
Decreased radiodensity parallel to physis
Irregular widening of the physis
Sub and extra-periosteal new bone
Panosteitis typically affects which kinds of dogs?
What is it?
Large breeds, 5-18 months old, male
Fibrosis of bone tissue
Which radiographic abnormalities are associated with panosteitis?
Increased opacity of medullary cavity
Indistinct trabecular pattern
Increased endosteal opacity (darker appearance)
Describe the pathogenesis of Legg-Calve-Perthes Disease
Avascular necrosis of the femoral head
Bone remains mechanically stable initially
When SCB loses mechanical strength – collapse of articular surface
Legg-Calve-Perthes Disease affects which kinds of dogs?
Toy breeds, 4-11 months
What is the treatment for Legg-Calve-Perthes Disease?
Surgical, due to severity of arthritis
Femoral head and neck excision
Which 2 terms are used to describe deviation of a limb from the normal axis in angular limb deformities?
Valgus – lateral deviation distally
Varus – medial deviation distally
How do angular limb deformities occur?
Asynchronous growth of a pair of bones
ie radius and ulna
Differential growth between bones, after damage to one (trauma to growth plate)
Shorter (affected) bone acts to create bowing of longer bone
Angular limb deformities affect which kinds of dogs?
Small breeds, eg Shi-tzu
How do flexural limb deformities occur in cows and horses?
Disproportionate growth
Bone is functionally longer than muscle-tendon unit
Which 4 things should you assess when doing an initial static evaluation of an equine orthopaedic exam?
(1) Posture
(2) Balance
(3) Muscling/symmetry
(4) Conformation of the limbs
How can you determine whether swelling is located around the carpal joint or tendon sheath?
Joint effusion is generally horizontal, whereas tendon sheath is vertical
The common calcanean tendon is made up of what?
Where does it insert?
Where does the calcanean bursa lie?
Gastrocnemius, semitendinosus, biceps femoris
Inserts on calcaneus underneath SDFT
Bursa lies between SDFT and calcanean tuberosity
What happens to the SDFT as it inserts on the calcaneus?
Widens
What is ‘curb’ in horses?
Swelling of the distal plantar aspect of the hock, common in highly active horses
How do you determine which forelimb a horse is lame on?
Head/neck RISE as the lame leg bears weight (or just before)
How do you determine which hindlimb a horse is lame on?
Asymmetrical movement of the pelvis
There is increased overall vertical movement of the tuber coxae/hindquarters of the lame leg (compared to the non-lame leg)
What might it mean if a horse lands its feet toe first?
Palmar foot pain
What might it mean if a horse lands its feet heel first?
Abscesses/laminitis
When lunging a horse, which kinds of injury may be worse on the inside and outside?
Inside: foot/joint lameness
Outside: soft tissue injury
Briefly describe how you can manipulate the upper limb
Shoulder and elbow region
Limb pulled caudally will extend elbow and flex shoulder
Limb extended cranially will extend shoulder and flex elbow
