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MSK2 > Bone pathology 2 > Flashcards

Bone pathology 2 Flashcards

1
Q

Outline how fracture management can lead to osteopaenia

A
  • Stress protection
  • Implants reduce stress on bone
  • No early mobility due to repair, leads to reduced mineral deposition on bone
  • Weakened and at risk of pathological fracture
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2
Q

Compare the radiographic appearance of a traumatic fracture compared with a pathological fracture?

A

Pathological fracture usually has more bony changes around the fracture site, more lytic areas

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3
Q

Compare osteitis and osteomyelitis

A

Osteitis: centripetal i.e. moving towards marrow
Osteomyelitis: centrifugal i.e. starts in marrow and moves out

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4
Q

Describe the appearance of osteomyelitis on radiography

A
  • Disorganised, areas of lucency
  • Soft tissue swelling
  • Irregular, semi-aggressive periosteal reaction
  • More extensive than fracture callus
  • Area of sclerosis around focus
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5
Q

What features are assessed in the determination of an aggressive vs non-aggressive lesion on radiography?

A
  • Lysis
  • Periosteal reaction pattern
  • Lytic edge character
  • Cortical disruption
  • Transition zone
  • Rate of change (10-14 days)
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6
Q

Briefly outline the bone lysis patterns that may be seen and rank these from non-aggressive to aggressive

A
  • Geographic (single, well demarcated focus)
  • Geographic (more aggressive if affecting only medulla)
  • Moth eaten lysis (multiple areas)
  • Permeative lysis (most aggressive)
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7
Q

Describe the benign (continuous) periosteal reaction patterns

A
  • Lines parallel to the cortex typically

- Solid, lamellar (flat line), lamellated (slight rounding)

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8
Q

Briefly describe the interrupted (aggressive) periosteal reaction patterns and rank these from least to most aggressive

A
  • Thick brush like (thick lines of periosteum perpendicular to the cortex)
  • Think brush like (think lines)
  • Sunburst (lines of periosteum from focus moving outwards in a divergent pattern)
  • Amorphous bone production (no lines visible, disorganised)
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9
Q

What determines a radiographic lesion as aggressive, semi-aggressive or non-aggressive?

A

The most aggressive radiographic sign is used to determine the lesions degree of aggressiveness

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10
Q

What disease may be suggested by non-aggressive, slow developing radiographic signs?

A

Degenerative joint disease

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11
Q

Compare the radiographic appearance of neoplasia and infection in terms of degree of aggression

A
  • Neoplasia: aggressive if malignant
  • Non-aggressive/semi-aggressive if benign
  • Infection: often semi- aggressive
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12
Q

Describe the orientation for viewing a lateral radiograph

A
  • Proximal part of limb at top of image

- Cranial aspect of limb to the left

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13
Q

Describe the orientation for viewing a craniocaudal radiograph

A

Proximal part at the top

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14
Q

Describe the orientation for viewing a ventrodorsal radiograph

A
  • Cranial part at the top

- Left marker on the right of the image when viewed

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15
Q

What normal feature of bone may commonly be mistaken as a small fracture?

A

Nutrient foramen

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16
Q

What are the advantages of MRI for imaging of the spinal column?

A
  • Cross sectional image avoids superimposition

- Excellent soft tissue definition

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17
Q

Describe the appearance of discospondylitis on MRI

A
  • Loss of signal from nucleus pulposus so appears hypointense
  • Maybe some dislocation of vertebrae
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18
Q

Outline the advantages of CT in imaging of the spinal column

A
  • Can be combined with myelography
  • Can be useful where MRI not feasible e.g. metal implants
  • Avoids superimposition
  • Better for osseous structures vs. MRI
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19
Q

Describe the appearance of the subarachnoid space on a transverse CT myelogram

A

Radiopaque circle within the vertebral canal

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20
Q

Briefly outline the principles for myelography

A
  • Injection of water-soluble non-ionic iodine contrast medium into the subarachnoid space
  • Use of non-ionic medium in order to reduce side effects
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21
Q

What locations are used for the injection of contrast medium for myelography?

A
  • Cisterna magna

- Caudal lumbar suubarachnoid space

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22
Q

What are the risks associated with myelography?

A
  • Short term side effects e.g. incoordination

- Injection into spinal cord itself can result in permanent paralysis, or rarely, death

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23
Q

Compare cisternal and lumbar puncture for myelography

A
  • Cisternal technically easier but less useful for thoracolumbar lesions as contrast may not reach that far
  • Lumbar technically more difficult, better for thoracolumbar or lumbar lesions, may have less risk as not injecting near to proximal spinal cord
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24
Q

What modalities can be used for head and neck imaging?

A
  • Radiography
  • Ultrasound
  • CT
  • MRI
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25
Q

Outline the limitations of radiography for imaging of the skull

A
  • Anatomy complex
  • Structures bilaterally symmetrical, can be impossible to distinguish on lateral views
  • Accurate positioning difficult
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26
Q

What radiographic views can be taken of the skull?

A
  • Lateral
  • Dorsoventral
  • Lateral oblique
  • Rostrocaudal
  • Rostrocaudal open-mouth
  • Dorsoventral intraoral
  • Ventrodorsal open-mouth oblique
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27
Q

Outline the positioning and centring for a lateral radiograph of the skull

A
  • Lateral recumbency, nose and mandible raised with lucent pads to ensure sagittal plane of skull is parallel to the cassette
  • Centre beam mid-way between eye and ear
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28
Q

Outline the positioning and centring for a dorsoventral radiograph of the skull

A
  • Sternal recumbency, nose and mandible raised with lucent pads so transverse plane of skull is parallel to the cassette
  • Centre beam mid way between medial canthi of eyes
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29
Q

What are the indications for use of a lateral oblique radiograph of the skull?

A

Imaging of the temporomandibular joints or bullae

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30
Q

Outline the positioning for a lateral oblique radiograph of the skull

A
  • Wedge pad to raise rostral aspect of the head

- Lateral recumbency

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31
Q

What are the indications for use of a rostrocaudal “skyline” radiograph of the skull?

A

Imaging for frontal sinuses, zygomatic arch, temporal region, sagittal crest

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32
Q

Outline the positioning for a rostrocaudal “skyline” radiograph

A
  • Dorsal recumbency
  • Skull secured with tape around nose so hard palate is perpendicular to cassette
  • Beam angled at 5-10degrees in rostrocaudal direction
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33
Q

What are the indications for a rostrocaudal open-mouth view in dogs and what modification is used in cats?

A
  • Closed mouth in cats

- Used for tympanic bullae

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34
Q

Outline the positioning for a rostrocaudal open mouth radiograph

A
  • Dorsal recumbency
  • Mouth held open using tape
  • Primary beam centred on base of skull
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35
Q

What are the indications for a dorsoventral intraoral radiograph?

A

demonstration of nasal chambers, premaxilla, upper incisors, rostral portions of maxilla and premolar teeth

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36
Q

Outline the positioning of a dorsoventral intraoral radiograph

A
  • Sternal recumbency
  • Screen film used for incisor region but non-screen film for fuller examination of maxillary arcades
  • For incisors, angle beam around 20degrees
  • ET tube tied to lower jaw
  • Film placed above tongue and tube
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37
Q

What are the indications for ventrodorsal open-mouth oblique radiographs?

A
  • Nasal chambers
  • Is alternative to dorsoventral intraoral
  • Preferred view for feline nasal cavity
38
Q

Outline the positioning for a ventrodorsal open-mouth oblique radiograph

A
  • Dorsal recumbency and mouth held wide open with tapes attached to the table and radiolucent gag
  • Place sandbag or bandage roll under neck to ensure hard palate is parallel to table top
  • Tongue and ET tube tied to mandible
  • X-ray tube angle 20degrees rostrocaudally
  • Centre beam on midline of palate at third premolar teeth
39
Q

What are the general indications for radiography of the head?

A
  • Trauma
  • Malformation
  • Foreign body
  • Neoplasia
  • Dental investigation
  • Intracranial pathology
  • Ear disease
  • Nasal disease
40
Q

Describe the radiographic appearance of hydrocephalus

A
  • Exaggerated dome shape of skull
  • Thinned bones of calvarium
  • Open fontanelle and suture bones
41
Q

Describe the possible appearance of ear disease on radiography

A
  • Otitis media: increased soft tissue/fluid opacity of the tympanic bulla, thickened +/- irregular bulla wall
  • Loss of air shadow in external ear canal may be seen in cases of severe otitis, polyps and neoplasia
  • External ear cartilages may be calcified in chronic otitis
42
Q

Describe the radiographic appearance of rhinitis

A

Increased nasal cavity radiopacity with retention of underlying turbinate pattern

43
Q

Describe the radiographic appearance of nasal neoplasia

A

Increased radiopacity with loss of turbinates

44
Q

Describe the radiographic appearance of fungal rhinitis

A

Decreased radiopacity with loss of turbinates

45
Q

When might ultrasonography of the head be useful?

A

If fontanelle still open, can visualise ventricles and determine if they are enlarged e.g. in hydrocephalus

46
Q

List the treatment options for osteosarcomas

A
  • Euthanasia
  • Analgesia only (poor prognosis, unlikely to be enough to remove pain)
  • Limb sparing surgery or limb amputation
  • Chemotherapy
  • Palliative radiation
  • Chemo + limb sparing surgery
47
Q

Describe limb sparing surgery with chemotherapy as a treatment for osteosarcomas

A
  • Remove tumour with a margin and fill gap with plate

- Fill with bone graft (prevents bending of plate)

48
Q

What chemotherapeutic agents are used in the treatment of osteosarcomas?

A

Cisplatin and doxorubicin

49
Q

Which breeds are predisposed to osteosarcomas?

A
  • Large to giant breed dogs with late closing growth plates
  • Taller for breed more at risk
  • Scottish deerhound, Rottweiler, Irish wolfhound, St Bernard, Great Dane, Doberman, German shepherd
50
Q

Where are osteosarcomas typically found?

A
  • Close to the knee, away from the elbow
  • Metaphyses typically affected
  • Thoracic limb > pelvic
  • Distal radius, proximal humerus, uncommon in ulna
  • Typically appendicular, can affect axial and soft tissues
51
Q

Outline the signalment for osteosarcomas

A
  • 7-8yo
  • Neutered
  • Large/giant breeds, tall individuals
52
Q

Outline the diagnosis of osteosarcomas

A
  • Initial clinical presentation
  • Radiographic findings
  • FNA and cytology (ALP staining to differentiate osteosarc from other primary bone tumours)
  • Bone biopsy
53
Q

Describe the typical clinical presentation for osteosarcomas

A
  • Progressive lameness, leg swelling
  • Lameness usually intermittent and progressive and severe (initially mild)
  • Mass site firm and painful
  • Often pathological fractures
54
Q

Outline the staging of osteosarcomas

A
  • Radiography, assess joint above and below
  • MRI and CT ideal
  • MRI best before operation to indicate medullar extent
  • CT best for lung mets
55
Q

Outline the metastatic rate of osteosarcomas

A
  • 90% have mets at diagnosis but only 10% are identifiable at diagnosis
  • Appendicular OSA are highly malignant
56
Q

Describe the common sites of metastasis for osteosarcomas

A
  • Lungs most common initially
  • Bone mets more prevalent following tx with surgery and chemotherapy vs surgery alone
  • Distant limp nodes, kidney, spleen, myocardium, diaphragm, mediastinum, spinal cord, small intestine, gingiva and subcut tissue also sites of metastasis
57
Q

Where do osteocytes originate from and where are they located?

A
  • Originate from osteoblasts

- Surrounded by bone matrix (osteoid) in bone spicules

58
Q

How is lamellar bone formed and arranged?

A

Newly formed bone is woven, remodelled by osteoclasts into lamellar bone arranged into Haversian systems

59
Q

Outline the structure of an osteon

A
  • Central nerve, lymphatic vessel, vein and artery
  • Surrounded by lamellae
  • Osteocytes between layers of lamellae, enclosed by lucunae
  • Around outside are osteoblasts, and occasional osteoclasts
60
Q

Where is hyaline cartilage found?

A
  • Joint surfaces
  • Physes
  • Nose
  • Trachea
61
Q

Where are chondrocytes located?

A

Often as groups of 2-4 within lucanae, in amorphous matrix

62
Q

Where are chondroblasts found?

A

In perichondrium

63
Q

Where is elastic cartilage found?

A

Ears

64
Q

What is the main difference between elastic and hyaline cartilage?

A

Increased numbers of elastic fibres in elastic cartilage

65
Q

Describe the structure and location of fibrocartilage

A
  • No periochondrium
  • Intermediate between connective tissue and hyaline cartilage
  • Found in intervertebral discs only
66
Q

Describe the histological appearance of a new fracture

A
  • Similar to tumour in terms of increased number of cells
  • No bizarre cells present
  • Lots of osteoblasts (producing osteoid to form lamellae)
67
Q

Describe the histological appearance of older fractures

A
  • Spicules of spongy bone beginning to make lamellae

- Contain osteocytes

68
Q

Describe the immediate response to structural damage within the bone

A
  • Haematoma forms containing inflammatory mediators
  • e.g. kinins, complement, histamine, serotonin, prostaglandins, leukotrienes
    → vasodilation, chemotaxis of white blood cells, platelet aggregation and release, mesenchymal cell proliferation
69
Q

What are the 3 phases of bone reparation?

A

Inflammation
Repair
Remodelling

70
Q

Describe the inflammatory phase of bone healing

A
  • Occurs within first 2-3 weeks
  • Clearance of debris/necrotic/devitalised bone
  • Fracture gap widens
  • Influx of cytokines and growrth factors
  • Phagocytosis of tissues
  • Fragment end resoprtion
  • By 4 weeks have callus formation
71
Q

Describe the reparative phase of bone healing

A
  • INdirect repair, healing under motion
  • 2-12 months duration
  • angiogenesis (initially in adjacent tissues, the medullary blood supply restored)
  • Periosteal and endosteal callus formation
  • Bone union
72
Q

Describe the periosteal and endosteal callus formation in the reparative phase of bone healing, and what may suppress this

A
  • Large surface area, not strong bone but large surface area provides good and rapid stabilisation
  • Suppressed by rigid immobilisation, excessive mobilisation
73
Q

Describe the bone union in the reparative phase of bone healing

A
  • Cancellous bone formed by combination of intramembranous and endochondral ossification
  • Cartilage component mineralised resulting in cancellous bone union, subsequently remodelled into lamellar bone
74
Q

Explain the difference between the endochrondal and intramembranous ossification that occurs in the reparative phase of bone healing

A
  • Endochondral: occurs at growth plates/fracture gap, initially get fibrous scaffold (fibroplasia, replaces haematoma) → cartilage (chondrogenesis)→ bone (mineralisation)
  • Membranous ossification: fibrous structure → mineralised bone (NO cartilage stage)
75
Q

Describe the remodelling phase of bone healing

A
  • Bone resorption and bone formation

- Cortical callus undergoes Haversian remodelling to form lamellar bone

76
Q

List the types of regulatory molecules involved in bone healing and give examples

A
  • Growth factors (e.g. TGFbeta, IGF-1/2, FGF)
  • Cytokines (IL-1, Il3, CSF, IL6)
  • Others: osteoponin, osteocalcin, osteonectin, prostaglandins
77
Q

What are the basic patterns of bone repair?

A

Primary (direct) or secondary (indirect) repair

78
Q

Describe primary (direct) fracture healing

A
  • Exact alignment
  • Rigid fixation
  • Sufficient blood supply
  • Provides rapid strength to fracture
  • No periosteal callus formation
  • Contact healing or gap healing
79
Q

Compare contact and gap healing in fracture healing

A
  • Contact: secondary osteonal (Havesian) remodelling of the fracture at interfragmentary contact points
    Gap: small gaps filled with woven then lamellar bone, secondary osteonal remodelling, grow across gap
80
Q

What are the fixation principles of direct fracture repair?

A
  • Anatomic reduction
  • Stable internal fixation
  • Interfragmentary compression
  • Preservation of blood supply
  • Early active, pain free mobilisation
81
Q

What are the methods of direct/primary bone repair?

A
  • External fixation (casts, braces, ESF)

- Internal fixation (screws, plates, IM pins)

82
Q

How is compression of a fracture commonly achieved to facilitate primary (direct) healing?

A
  • Dynamic compression plate

- Creates friction between plate and bone and compresses the 2 sides of a fracture together

83
Q

What are the advantagesof secondary (indirect) bone healing?

A
  • Allows rapid stabilisation

- Callus formation early on, provides strength

84
Q

What are the disadvantages of secondary (indirect) bone healing?

A
  • Long period of remodelling
  • Repair pattern influenced by both biology and mechanics
  • Not as successful in long bones in horses
85
Q

What may lead to difficulty in achieving accurate reduction of a fracture site?

A
  • Eburnation
  • Muscle contraction (esp. if fracture older than 12-24 hours)
  • Severe comminution
86
Q

What are the potential consequences of not achieving accurate anatomical reduction of a fracture?

A
  • Osteoarthritis (if articular misalignment)

- Cyclical implant loading which can lead to implant failure

87
Q

How can muscle contraction, preventing accurate fracture reduction, be overcome in the horse?

A
  • Early treatment

- Suspension of the limb with a mechanical hoist can allow better reduction

88
Q

Discuss the complications that may occur with stable internal fixation

A
  • Too stable and no motion at fracture gap → no callus formation
  • Excessive motion at fracture gap → hypertrophic non-union due to persistence of fibrous tissue
89
Q

Discuss the problems in fracture repair that are specific to horses

A
  • Large animals, enormous mechanical loads on recovery from GA
  • Rapid weight bearing following anaesthesia
  • Bed rest not an option
  • Often open fractures, soft tissue damaged
  • Contralateral overload (laminitis, angular limb deformity in younger animals, elongation of stay apparatus, cartilage degeneration
90
Q

List the potential consequences of prolonged limb immobilisation for fracture repair in the horse

A
  • Osteoporosis
  • Joint laxity
  • Tendon laxity
  • Cartilage degeneration
  • Pressure or rub sores
91
Q

Outline how surgical techniques can facilitate biological fracture healing

A
  • Small incisions
  • Minimal disruption to fractuer haematoma
  • Periosteum largely left in tact
92
Q

How can fracture repair be enhanced beyond standard techniques (i.e. direct, indirect fixation)?

A

Expensive, area of research

  • Cancellous bone grafting
  • Osteoconduction (scaffold)
  • Osteoinduction (stimulation of osteogenesis)

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