Difference between revisions of "Joints Degenerative - Pathology"

Revision as of 14:48, 26 September 2008

()Map MUSCULOSKELETAL SYSTEM (Map) JOINTS

Degenerative joint disease (DJD)

DJD in a horse (Image sourced from Bristol Biomed Image Archive with permission)

Osteoarthritis, osteoarthrosis
Due to acceleration of normal ageing process - wear and tear
Destructive disease leading to:
- Loss of weight-bearing articular cartilage
- Erosion, fibrillation of cartilage
  - Clefts in the cartilage, perpendicular to the surface
- Complete exposure of underlying bone
  - Bone appears polishes, dense - eburnation
  - Radiographically - joint space reduction due to loss of cartilage
- Osteophyte formation at joint margins
- Remodelling of adjacent bone
- Brown/yellow discolouration
- Synovial hypertrophy
- Capsular fibrosis
May affect one or multiple joints
May or may not be symptomatic
Pathogenesis:
- Not entirely clear but linked to loss of proteoglycans and subsequent lubrication
- Increased water content due to improper binding -> softening of cartilage = chondromalacia

Predisposing factors:
- Persistent trauma
- Joint instability / dysplasia
- Conformational abnormalities / congenital malformations
- Osteochondrosis dissecans
- Intra-articular fractures
- Calve Legg-Perthe's disease

Luxations and subluxations

Patellar

In stifle joints of dogs and horses
Possibly inherited
Small dog breeds:
- Medial luxation
- Due to underdevelopment of medial femoral condyle
Large dog breeds and horses:
- Lateral luxation

Atlantoaxial

In dogs, calves, horses and goats
Miniature dog breeds:
- Failure of fusion of odontoid process to rest of axis
Calves:
- Aplasia or hypoplasia of odontoid process

Temporomandibular

In dogs, particularly Basset Hounds, Irish Setters
Normal movement of mandibular coronoid process is interfered with by zygomatic arch
Happens on one side -> open jaw locking

Calve Legg-Perthe's disease

Almost exlusively in small dogs, particularly terriers and poodles
Clinical signs appear at age of 4-11 months
Grossly:
- Aseptic ischaemic necrosis in central parts of femoral head
  - Possibly due to occlusion of blood vessels
- Fragmentation of trabecular bone
- Collapse of femoral head
- Revascularisation of femoral head
- Formation of new bone and osteophyte formation around femoral head and acetabular rim prior to old bone reabsorption
- -> severe degenerative arthropathy

Degenerative arthropathy

In older dogs (8+ years)
Occurs bilaterally
In shoulders
?Due to gradual atrophy of muscles with age -> joint laxity

Traumatic injuries

Sudden
Varying severity
Acute injuries:
- Sprains
  - Minor - resolved without any consequences
  - More severe may result in persistent capsular and ligament laxity -> degenerative arthrosis -> impaired function
- Subluxations
- Luxations
- Intra-articular fractures
  - Fracture healing may cause discontinuity of the articular surfaces
- Puncture wounds to foot may allow infection to travel to joints, bursae and tendon sheaths
- Haemorrhage into joint
  - May occur in animals with clotting defects without special trauma
    - Usually polyaricular
    - Recurrent
    - May cause pitting of articular surfaces -> degenerative arthrosis

Nutritional diseases

Hypervitaminosis A

See metabolic diseases of bones
May cause spondylosis of cervical vertebrae
Mainly on dorsolateral surface
Also in elbow and shoulder joints -> fixation of joint
May resolve with changes of diet

Disc protrusion

Intervertebral disc degeneration (Image sourced from Bristol Biomed Image Archive with permission)

Occurs mainly in dogs
Almost always dorsal protrusion due to eccentric position of nucleus pulposus
Main sites are cervical and lumbar regions
- Thoracic vertebrae have conjugal ligaments
Degeneration precedes protrusion (two patterns):
- Chondroid
  - In chondrodystrophic breeds
  - Concurrent calcification of degenerated nucleus pulposus
  - Progressive loosening and fragmentation of overlying annulus fibrosis fibres
    - Damaged by both compressive and rotational forces
  - Predisposing degeneration of the discs occurs by one year of age in most of the dogs
  - Protrusion usually occurs in males, 3-6 years of age
  - Sudden complete protrusion -> severe damage to spinal cord in the area
  - Widespread necrosis and haemorrhage
  - Extruded material is gritty, hemorrhagic or “cheesy”
- Fibroid
  - In non-chondrodystrophic breeds, horses, pigs
  - Usually occurs later in life
  - Pathogenesis:
    - Progressive dehydration and collagenisation of nucleus pulposus
    - Fraying and fragmentation of lamellar annulus fibrosis fibres
    - -> Attempts to repair by fibrosis
    - -> Weak area in the annulus
    - -> Partial protrusion (rarely may calcify) of nucleus into spinal canal
      - May be dorsal or lateral
    - -> Pressure on spinal cord
    - -> Demyelination of white matter
    - -> Progressive weakness of structures innervated distally to the lesion
  - Disk material may enter blood vessels causing fibrocartilagenous embolism
    - May present without any disk symptoms

Sudden protrusion can occur in any breed due to traumatic compression of spinal cord

Cervical spinal stenosis

Usually funnel-shaped
Stenosis in dorso-ventral plane
May occur at more than one site
Predisposed in some breeds: Great Dane, Doberman, Basset Hound, Irish Wolfhound, Old English Sheepdog
Clinical signs: cervical pain -> ataxia -> quadriplegia

Cervicospinal arthropathy

= "Wobbler" in horses
Usually presents in first two years of life
Mainly in fast growing thouroughbreds
Most common site is C3-C4, can occur anywhere
Abnormal laxity between the vertebrae + cervical vertebral malformation may be evident
Osteophyte formation at edges of synovial components of joint
Some due to stenosis of neural canal later in life (1-4 years of age)
Clinical signs:
- Ataxia - hindlimbs more affected
Presumed cause is rapid growth

Spondylosis

Spondylosis (Image sourced from Bristol Biomed Image Archive with permission)

Often in bulls and dogs, occurs also in horses, cats and pigs
Osteophyte formation on ventral aspect of vertebrae
- Often around lumbar region
- Adjacent to intervertebral spaces
- Varies in size - small spurs -> 'bridges' between vertebrae
- May extend over few vertebrae
Pathogenesis:
- Repeated abnormal movement between joints -> stress
- -> Degeneration of annulus fibrosis
- -> Osteophyte formation
In dogs usually no symptoms
In bulls may cause inability to mount
In severe cases repeated damage may progress to recurrent posterior weakness and ataxia in conjuction with fractures of spondylitic and vertebral bone

Cranial cruciate ligament rupture

Autoantibodies against collagens seen in the joint fluid – no relationship to the disease (ie: not an autoimmune disease) – can be seen in any joint disease

Steroid arthropathy

From glucocorticoids injected into joint as antiinflammatories
Injection sometimes causes rapid progression of degeneration
Glucocortyicois suppress anabolic effect of chondrocytes -> reduction of cartilage matrix syhthesis -> proteoglycan depletion -> slower repair

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