VCA 341 Fall 2011
Andrea Matthews, DVM, Dip ACVR
Assistant Professor of Radiology

Hypertrophic Osteopathy
(HO)
Occurrence
 Middle aged to older dogs
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Usually due to concurrent thoracic or abdominal disease
Often pulmonary neoplasia; also reported with pulmonary abscesses, bronchopneumonia, bacterial endocarditis, heartworm disease, esophageal pathology, as well as hepatic and bladder neoplasia
Gradual or occasional acute onset in lameness
Animal reluctant to move
Symmetric, non-edematous, firm swelling of the distal limbs
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Hypertrophic Osteopathy
(HO)
Roentgen signs
 Solid, irregular periosteal reaction
• Palisading or columnar new bone formation
 Never confined to a single location
- Usually bilaterally symmetrical and generalized
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Hypertrophic Osteopathy
(HO)
Roentgen signs
 Begins on the abaxial surface of the 2 nd and
5 th metacarpal/metatarsal bones and progresses proximally
 Spares the small bones of the carpus and tarsus
• But is seen on the accessory carpal bone and calcaneus
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Hypertrophic Osteopathy
(HO)
 Location of periosteal reaction is diaphysis of tubular bones
Radiographs of the thorax and abdomen should be obtained to investigate for underlying disease
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Fungal Osteomyelitis
Occurrence
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Typically seen in young to middle-aged dogs
May be seen in any breed; however, more common large breeds such as working or sporting breeds
Usually hematogenous in origin
Often systemically ill
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Fever
Lethargy
Anorexia
Lymphadenopathy, etc…
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Fungal Osteomyelitis
Roentgen signs
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Variable radiographic appearance
Both lytic and productive changes
Periosteal reaction usually semi-aggressive
Osteolysis may extend through the cortex
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Usually in the metaphyseal region of long bones
May be joint involvement with extensive bone destruction
 Often polyostotic but can be monostotic
Differential Diagnoses
 Primary bone tumors
 Metastatic bone tumors
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Fungal Osteomyelitis
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Fungal Osteomyelitis
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Bacterial Osteomyelitis
Occurrence
 Usually secondary to…
• Direct inoculation (bite wound, open fracture, or surgery)
• Extension from soft tissue injury
 May be hematogenous in young or immunocompromised animals
• Hematogenous route is much less common in small animals
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Bacterial Osteomyelitis
Roentgen signs
 Earliest stage
• No bony abnormalities, just soft tissue swelling
 May take 7-14 days before periosteal reaction visible
 Periosteal reaction typically solid and extends along shaft of diaphysis; however, can be lamellar to palisading/columnar
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Bacterial Osteomyelitis
 Lesion location depends on affected area
 May affect multiple bones in the same limb
 Lucencies around surgical implants
 May see draining tract from surgical implant or foreign body
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Metaphyseal due to extensive capillary network
Often multiple limbs affected (polyostotic)
 Healing fracture
 Primary or metastatic bone tumor
 Fungal osteomyelitis
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Bacterial Osteomyelitis
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Primary Bone Tumors
Occurrence
 Mostly large and giant breed dogs; no breed predilection
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Mean age = 7 years
Bimodal distribution  seen in animals as young as
6 months
 Slightly more common in male dogs
 May be associated with a previous fracture or metallic implant
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Primary Bone Tumors
Roentgen signs
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Radiographic appearance is variable
Primarily osteoblastic
Primarily osteolytic
Combination of both
 Lytic and/or productive changes are aggressive in nature
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Typically monostotic
Located often in metaphyseal region of a long bone
 Does not typically cross the joint
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Primary Bone Tumors
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Most common primary bone tumor (>85%)
“Away from the elbow, toward the knee”
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Osteomyelitis
Metastatic neoplasia
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Primary Bone Tumors
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Fracture Evaluation
Initial radiographs
 Two orthogonal views (90 o to one another)
 Include the joint proximal and distal to the fracture
• Determine joint involvement
 Special radiographic views may be necessary to determine the extent of the fracture
• Oblique, etc
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Fracture Recognition
Most are visible as abnormal radiolucent lines
 Some may not be as obvious
 Ex. Compression, non-displaced or pathologic fracture
 Occassionally, compression fractures may result in alteration in size or opacity, creating a summation opacity (more opaque than normal)
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Fracture Recognition
Non-displaced fractures
 May not be seen initially
 Seen days later when resorption of bone at fracture margins has occurred
 Some are recognized by presence of bony callus
 If clinical suspicion of fracture is high but equivocal  Nuclear medicine
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Fracture Description
Fracture types
 Open vs closed
 Incomplete vs complete
 Simple vs complex/comminuted
 Transverse, oblique or spiral
 Extra-articular, articular, compression, avulsion
 Displaced vs. non-displaced
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Bone Healing
Primary bone healing
 Occurs with rigid internal fixation
 Results in bony union through direct growth of haversian system across the fracture
 Minimal to no bony callus
 Cannot occur across a fracture gap
 Usually occurs with compression plate reduction
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Primary Bone Healing
Radiographic signs of primary bone union
 Lack of callus
 Gradual loss in opacity of fracture ends
 Progressive disappearance of fracture line
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Bone Healing
Secondary bone healing
 Lack of rigid internal fixation and excellent anatomic reduction
 Bone heals through initial deposition of fibrous tissue
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Callus formed by series of maturations
Granulation tissue  cartilage  mineralized cartilage  replaced by bone
Most common type of fracture healing in small animals
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Secondary Bone Healing
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Secondary Bone Healing
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Bone Healing
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Factors that affect bone healing
 Fracture location
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Vascular integrity
Degree of immobilization
Fracture type
Degree of anatomic reduction
Degree of soft tissue trauma
Degree of bone loss
Type of bone involved
Presence of infection
Local malignancy
Metabolic factors
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Age, breed, species
Presence of systemic disease
Steroid administration
And on and on and on…
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Evaluate;
 Fracture alignment
 Degree of fracture reduction
• Needs to be at least 50% reduction of fracture margins
 Presence of joint incongruities
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• Step deformities
If fracture is articular
 Rotation of fracture fragments
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Evaluate;
 Placement of fixation devices
• With bone plate, ideally want 6 corticies engaged with cortical screws above and below the fracture site
• Pins of external fixator should be angled 65-70 o to bone
 Not possible with all types of external fixators
• Cerclage wires should be of adequate size, be perpendicular to the long axis of the bone, be a minimum of 1 cm apart, be adequate in number and fit snugly against the cortex
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Growth Plate Injuries
Good prognosis
Poorer prognosis Guarded prognosis
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Growth Plate Injuries
Occurrence
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Etiologies
Trauma
Severe hypertrophic osteodystrophy (HOD)
Retained cartilaginous core
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Skeletally immature animals <1 year
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Prognosis
Salter Harris Type I and II have better prognosis
Type III and IV have poorer prognosis due to disturbance of resting cell layer
Type V have guarded prognosis due to damage of proliferative zone
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Growth Plate Injuries
Roentgen signs
 Unilateral or bilateral
• Radiographs both limbs for comparison
 Affected physis may initially appear normal or may be closed
 Skeletal deformities
 Distal ulnar physis is commonly affected due to shape
• Often type V
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Premature Distal Ulnar Physis Closure
Roentgen signs
 Affected ulna is measurably shorter than contralateral side
(unless bilateral)
 Styloid process of ulna may be separated from carpus
 May have cranial and/or medial bowing of radius
• Cortical thickening of the concave side of the radius (due to stress remodeling)
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Premature Distal Ulnar Physis Closure
Roentgen signs
 Distal radius is subluxated craniomedially from the radiocarpal bone
 Manus deviates laterally
• Carpal valgus
 Humero-ulnar joint space may be widened (subluxation)
 +/- osteoarthrosis
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Premature Distal Ulnar Physis Closure
 Note widening of the humero-ulnar joint
(black arrows)
 Note the UAP that can occur secondarily (green arrow)
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Premature Distal Radial Physis Closure
Roentgen signs
 Shortened length of the radius compared to contralateral side (unless bilateral)
 Increased radiocarpal joint space
 Increased humero-radial joint space (subluxation)
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Growth Plate Injuries
The elbow is key to determine origin of slowed growth
Normal Radial physeal closure
Ulnar physeal closure
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Premature Distal Ulnar Physis Closure
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Premature Distal Radial Physis Closure
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End
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