1. Small Animal Orthopedic Radiology Lecture 2 – Developmental Bone Disease
VCA 341 Fall 2011
Andrea Matthews, DVM, Dip ACVR
Assistant Professor of Radiology

2. Osteochondrosis Failure of endochondral ossification
Leads to increased thickness of articular cartilage
Appears as subchondral defect
Osteochondrosis = OC
Osteochondritis dissecans = OCD
When a flap is formed and separates from subchondral bone
Only seen radiographically when……
mineralized
or… with arthrography

3. Osteochondrosis Occurrence
Young, rapidly growing, large to giant breed dogs
Usually develop signs between 6-9 months of age
Occurs in specific anatomic locations
Caudal aspect of humeral head
Medial aspect of the humeral condyle
Lateral femoral condyle
Trochlear ridges of the talus (medial most commonly)
Can occur in other locations
Frequently bilateral

4. Shoulder Osteochondrosis
Roentgen signs
Subchondral defect and scelosis of the caudal or caudolateral aspect of the humeral head

5. Shoulder Osteochondrosis
Roentgen signs
Secondary osteoarthrosis
Osteophytes may form in the intertubecular groove
Calcified flap of articular cartilage  OCD

6. Elbow Osteochondrosis
Roentgen signs
Subchondral defect and sclerosis of the medial aspect of the humeral condyle, best seen on DLPMO view
Secondary osteoarthrosis

7. Stifle Osteochondrosis
Roentgen signs
Subchondral defect and sclerosis of the distal aspect of the lateral femoral condyle
May also affect medial condyle but less common
Joint effusion and osteoarthrosis

8. Stifle Osteochondrosis

9. Stifle Osteochondrosis
Normal anatomy
The extensor fossa of the long digital extensor muscle can be confused with an OC lesion

10. Stifle Osteochondrosis
OC lesion
Extensor fossa

11. Tarsal Osteochondrosis
Roentgen signs
Flattening of the medial trochlear ridge of the talus
Widening of the joint space
Associated with intracapsular ST swelling and DJD
Normal OC

12. Tarsal Osteochondrosis

13. Tarsal Osteochondrosis
Roentgen signs
On the lateral view, the plantar aspect of the tibiotarsal joint will appear wide
A mineral fragment may be seen  OCD

14. Elbow Dysplasia
Fragmented medial coronoid process (FCP) Ununited anconeal process (UAP) Osteochondrosis of the medial humeral condyle (OC) Asynchronous growth of the radius and ulna (?) Proximal ulnar dysplasia (?)

15. Fragmented Medial Coronoid Process
Occurrence
Most common developmental abnormality of the elbow
Medium and large breed dogs
Retrievers, GSD, Bernese Mountain Dog
Clinical signs develop usually at 5-12 months of age
Higher incidence in males

16. Fragmented Medial Coronoid Process
Roentgen signs
Earliest signs are sclerosis of the trochlear notch of the ulna and osteophytes on the anconeal process and radial head
Osteophytes on the medial coronoid seen on the craniocaudal view

17. Fragmented Medial Coronoid Process
Roentgen signs
Medial coronoid appears blunted on the lateral views
May see fragment; however, no fragment is visualized in the majority of cases

18. Fragmented Medial Coronoid Process

19. Ununited Anconeal Process
Occurrence
Anconeal process forms from separate center of ossification
Normally fuses to proximal ulna at 5 months of age
Failure to fuse (likely due to joint incongruity)  UAP
GSD predisposed; also seen in other large breeds and Bassett hounds

20. Ununited Anconeal Process
Roentgen signs
Irregular, lucent line crossing the anconeal process with adjacent sclerosis
Best seen on flexed lateral view
Secondary osteoarthrosis

21. Ununited Anconeal Process

22. Ununited Anconeal Process

23. Panosteitis Occurrence
5-18 months of age; reports in mature animals (out to 7 years)
Large to giant breed dogs
GSD, Dobermans, Retrievers, Bassett hounds
Self limiting disease with unknown etiology
Shifting leg lameness with pain on palpation of long bones
Histologically no evidence of inflammation

24. Panosteitis Roentgen signs Early Increased medullary opacity
Usually in diaphysis near nutrient foramen
Blurring of trabecular pattern

25. Panosteitis Roentgen signs Late
Medullary opacities become better delineated  patchy appearance of medullary cavity
Adjacent opacities may coalesce
Rough endosteal surface
Solid periosteal reaction may be noted

26. Panosteitis

27. Hypertrophic Osteodystrophy (HOD)
Occurrence
2-7 months of age
Large to giant breeds of dog
Unknown etiology
Usually systemically ill
Usually reluctant to move, painful walking
Swollen, painful distal radius/ulna and distal tibia
Pyrexia

28. Hypertrophic Osteodystrophy (HOD)
Roentgen signs
Lesions usually bilaterally symmetric and involve the metaphysis of long bones, especially the distal radius, ulna and tibia
Early
Thin, radiolucent band in the metaphysis just proximal to the physis  “double physis sign”
Sclerosis adjacent to the radiolucent line in the metaphysis

29. Hypertrophic Osteodystrophy (HOD)
Roentgen signs
Late
Formation of a cuff or sleeve of periosteal new bone adjacent to the metaphysis, which is separated from cortex by thin, lucent zone
Represents subperiosteal hemorrhage

30. Hypertrophic Osteodystrophy (HOD)
Roentgen signs
Late
Periosteal reaction becomes more solid and confluent with the cortex later on
Results in marked bony enlargement of the metaphysis

31. Hypertrophic Osteodystrophy (HOD)

32. Hypertrophic Osteodystrophy (HOD)

33. Hypertrophic Osteodystrophy (HOD)
Images show progression of disease…
Early
Late

34. Retained Cartilaginous Core
Occurrence
Unknown etiology
Form of OC of the distal ulnar metaphysis/physis
Failure of endochondral ossification resulting in formation of core of cartilage in the metaphysis
Large to giant breeds
Saint Bernard
Usually develop clinical signs around months of age
Often bilateral

35. Retained Cartilaginous Core
Roentgen signs
Conical, radiolucent zone extending from the distal ulnar physis proximally into the distal ulnar metaphysis
Smoothly marginated or irregular

36. Retained Cartilaginous Core

37. Retained Cartilaginous Core
Roentgen signs
Can cause asynchronous growth of the radius and ulna and angular limb deformity

38. Hip Dysplasia Normal hip joint
At least ½ of the femoral head should be covered by the dorsal acetabular rim
The femoral neck should be narrower than the head and have a smooth margin

39. Hip Dysplasia Roentgen signs Shallow, flattened acetabulum
Inadequate femoral head coverage or even subluxation
Normal

40. Hip Dysplasia Roentgen signs
Periarticular osteophytes form along the acetabular rim, resulting in an irregular edge

41. Hip Dysplasia Roentgen signs Morgan line
Osteophyte formation along caudal femoral neck usually secondary to joint laxity
These osteophytes are actually enthesiophytes at the attachment of the joint capsule

42. Hip Dysplasia Standard VD view of Pelvis
Pull legs straight back and rotate inward
Open collimation to include entire pelvis and both femora through to the stifles
Called “straight or extended leg view”
Used for OFA evaluation

43. Hip Dysplasia Orthopedic Foundation for Animals (OFA)
Uses extended leg view
24 months of age or older
Evaluate for subluxation, degenerative changes
Hips graded based on following categories
Excellent
Good
Fair
Borderline
Mild dysplasia
Moderate dysplasia
Severe dysplasia

44. Hip Dysplasia
PennHIP
The University of Pennsylvania Hip Improvement Program
Allows evaluation of joint laxity prior to degenerative changes
Examiners have to be certified
Three sets of radiographs
Extended leg
Distraction view with distraction apparatus
Compression view with distraction apparatus
Calculation of distraction index (DI)

45. Hip Dysplasia Distraction index (DI) 0 = tightest hip
1 = completely luxated hip
0.4 = cut off index which identifies dogs that have the highest probability of developing osteoarthrosis secondary to hip dysplasia
Index corrected for breed

46. Hip Dysplasia
Distraction
Compression
Extended leg

47. Hip Dysplasia Other methods Half-axial view Distraction method
Distance between the femoral heads compared on extended leg view and distraction view
Norberg angle
Used in Europe
Normal angle is >105 degress

48. Aseptic Necrosis of the Femoral Head (Legg-Calve-Perthes)
Occurrence and Pathogenesis
Young (8-18 months of age) toy and small breed dogs
Poodles, miniature pinscher, terriers
Bilateral <15% of the time
Compromised blood supply to proximal femoral epiphysis  necrosis of subchondral bone
Normal blood supply to femoral head in adult dogs
Synovial membrane (sole supply in puppies)
Arteries in round ligament of the head of the femur
Nutrient vessels through metaphysis (after physeal closure)

49. Aseptic Necrosis of the Femoral Head (Legg-Calve-Perthes)
Roentgen signs
Increased width of joint space
Articular cartilage thickens as ischemia causes necrosis of subchondral bone

50. Aseptic Necrosis of the Femoral Head (Legg-Calve-Perthes)
Roentgen signs
Irregular opacities in the femoral head
Fragmentation of trabeculae
Patchy regions of osteolysis in femoral head
Invasion of vascular granulation tissue absorbing and replacing dead bone

51. Aseptic Necrosis of the Femoral Head (Legg-Calve-Perthes)
Roentgen signs
Deformity and flattening of the femoral head

52. Aseptic Necrosis of the Femoral Head (Legg-Calve-Perthes)
Roentgen signs
Remodeling of the acetabulum = osteoarthrosis
Due to abnormal articulation and osteophyte formation on the acetabulum, femoral head and neck

53. Patellar Luxation (PL)
Occurrence
Young, small breed dogs; also seen in large breeds
Medial luxation in small breeds
Lateral in large breeds
Most commonly congenital/developmental
Can be traumatic
Associated with malalignment of the quadriceps due to rotation and/or deformity of the femur and/or tibia

54. Medial Patellar Luxation (MPL)
Roentgen signs
Patella medial to trochlear groove
Coxa vara
Lateral bowing of distal femur
Medial bowing of the proximal tibia
Medially located tibial tuberosity and quadriceps
Shallow trochlear groove
Requires skyline view to evaluate
Secondary osteoarthrosis usually mild

55. Medial Patellar Luxation (MPL)
Arrow is pointing to cranial margin of the patella

56. End