Small Animal Orthopedic Radiology Lecture 2 – Developmental Bone Disease

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) Early Late Images show progression of disease…

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 6-12 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