1. Small Animal Orthopedic Radiology Lecture 3 –
Acquired Bone Diseases
Fracture Healing and Evaluation
VCA 341 Fall 2011
Andrea Matthews, DVM, Dip ACVR
Assistant Professor of Radiology

2. Hypertrophic Osteopathy (HO)
Occurrence
Middle aged to older dogs
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
Increased blood flow to the extremities in affected animals

3. 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

4. Hypertrophic Osteopathy (HO)
Roentgen signs
Begins on the abaxial surface of the 2nd and 5th 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

5. 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

6. Fungal Osteomyelitis Occurrence Usually hematogenous in origin
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
Fever
Lethargy
Anorexia
Lymphadenopathy, etc…

7. Fungal Osteomyelitis Roentgen signs Differential Diagnoses
Variable radiographic appearance
Both lytic and productive changes
Periosteal reaction usually semi-aggressive
Osteolysis may extend through the cortex
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

8. Fungal Osteomyelitis

9. Fungal Osteomyelitis and arthritis

10. 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

11. 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

12. Bacterial Osteomyelitis
Nonhematogenous origin
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
Hematogenous origin
Metaphyseal due to extensive capillary network
Often multiple limbs affected (polyostotic)
Differential Diagnoses
Healing fracture
Primary or metastatic bone tumor
Fungal osteomyelitis

13. Bacterial Osteomyelitis

14. Primary Bone Tumors Occurrence
Mostly large and giant breed dogs; no breed predilection
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

15. Primary Bone Tumors Roentgen signs Radiographic appearance is variable
Primarily osteoblastic
Primarily osteolytic
Combination of both
Lytic and/or productive changes are aggressive in nature
Typically monostotic
Located often in metaphyseal region of a long bone
Does not typically cross the joint

16. Primary Bone Tumors Osteosarcoma Chondrosarcoma Fibrosarcoma
Most common primary bone tumor (>85%)
“Away from the elbow, toward the knee”
Chondrosarcoma
Fibrosarcoma
Hemangiosarcoma
Differential diagnoses
Osteomyelitis
Metastatic neoplasia

17. Primary Bone Tumors

18. Fracture Evaluation and Bone Healing

19. Fracture Evaluation Initial radiographs
Two orthogonal views (90o 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

20. 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)

21. 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

22. 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

23. 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

24. Primary Bone Healing Radiographic signs of primary bone union
Lack of callus
Gradual loss in opacity of fracture ends
Progressive disappearance of fracture line

25. Most common type of fracture healing in small animals
Bone Healing
Secondary bone healing
Lack of rigid internal fixation and excellent anatomic reduction
Bone heals through initial deposition of fibrous tissue
Callus formed by series of maturations
Granulation tissue  cartilage  mineralized cartilage  replaced by bone
Most common type of fracture healing in small animals

26. Secondary Bone Healing

27. Secondary Bone Healing

28. Bone Healing Factors that affect bone healing Fracture location
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
Age, breed, species
Presence of systemic disease
Steroid administration
And on and on and on…

29. Initial Postoperative Evaluation
Evaluate;
Fracture alignment
Degree of fracture reduction
Needs to be at least 50% reduction of fracture margins
Presence of joint incongruities
Step deformities
If fracture is articular
Rotation of fracture fragments

30. Initial Postoperative Evaluation
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 65-70o 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

31. Growth Plate Injuries Good prognosis Poorer prognosis
Guarded prognosis

32. Growth Plate Injuries Occurrence Etiologies
Trauma
Severe hypertrophic osteodystrophy (HOD)
Retained cartilaginous core
Skeletally immature animals <1 year
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

33. 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

34. 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)

35. 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

36. Premature Distal Ulnar Physis Closure
Note widening of the humero-ulnar joint (black arrows)
Note the UAP that can occur secondarily (green arrow)

37. 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)

38. Radial physeal closure
Growth Plate Injuries
The elbow is key to determine origin of slowed growth
Normal
Radial physeal closure
Ulnar physeal closure

39. Premature Distal Ulnar Physis Closure

40. Premature Distal Radial Physis Closure

41. End