Avascular necrosis of Hip Xray

radiological changes in Avascular necrosis of Hip
grading of AVN

1. Radiographic appearance in Avascular Necrosis of head of femur Dr. Gaurav Singh Central institute of orthopaedics VMMC & Safdarjung Hospital

2. Definition Avascular necrosis of femoral head refers to the death of the osteocytes with subsequent structural changes leading to femoral head collapse and secondary osteoarthritis of hip joint

3. Diagnostic modalities Routine radiographs MRI CT scan SPECT Perfusion scanning Bone scan Digital subtraction angiography

4. Radiography Routine radiographs first step towards diagnosis High quality films taken at least two views 90 degrees apart Helpful in assessing flattening of the femoral head and associated degenerative changes Limitations: Sensitivity for detecting early stages of the disease 41% Does not detect ficat arlet stage 0 and 1

5. radiological changes on plain x-ray Osteoporosis Mottled trabecular pattern Sclerosis Subchondral fractures (Crescent sign) Fragmentation Subchondral cysts Loss of spherical weight bearing dome Partial collapse of head Secondary osteoarthritis

6. Sclerosis and subchondral cysts~

7. Conventional radiograph of the right femur in the frog-leg position obtained with the patient’s thigh abducted and flexed shows subchondral area of hyperlucency (arrows) in the anterolateral aspect of the proximal femoral head

8. AP radiograph with the lucent crescent sign (white arrow) and the discontinuity where the subchondral bone has collapsed (black arrowhead)

9. Fragmentation Radiolucent clefts seen traversing bone

10. Alternating regions of the sclerosis and lucency within the superior aspect of the left femoral head ( arrows ), representing the reparative stage (stage 2). The lucent areas represent the site of resorption of necrotic marrow and trabecular . The sclerosis represents apposition of new bone on dead trabeculae .

11. There is a crescent-shaped density ( arrow ) representing the femoral head surface on an underlying zone of decreased density underneath the crescent-shaped bone representing demineralization.

12. Sclerosis Subchondral cysts

13. Asymmetric joint-space narrowing ( arrow ), juxta-articular sclerosis , and subchondral cyst formation

14. Anteroposterior radiographyc view of the pelvis shows flattening of the outer portion of the right femoral head from avascular necrosis, with adjacent joint space narrowing, juxta-articular sclerosis , and osteophytes representing degenerative joint disease (stage IV)

15. Modified Ficat and Arlet Radiographic Staging Stage Phases Interpretation Preclinical and preradiologic Only suggestive 1 Preradiologic Minimal osteoporosis, blurring of bony trabeculae 2a Reparative Diffuse osteoporosis, sclerosis and cysts A linear subcortical lucency beneath the articular cortex-the crescent sign, Subarticular cortex may remain attached to the cartilage and is separated from the underlying femur by soft tissue-the eggshell sign, joint-space widening. 2b 3 Early collapse of femoral head Sequential collapse and loss of sphericity of head 4 Progressive degenerative disease Degenerative joint disease with joint-space narrowing, marginal osteophyte formation, and subchondral cyst formation.

16. University of pennsylvania classification of osteonecrosis Stage Interpretation Normal/ non diagnostic x ray, bone scan or MRI 1 Normal X ray; abnormal bone scan and/ or MRI Mild (15% of femoral head affected) Moderate (15-30%) Severe (>30%) 2 Cystic and sclerotic changes in femoral head Mild (15% of femoral head affected) Moderate (15-30%) Severe (>30%) 3 Subchondral collapse (crescent sign) without flattening Mild (15% of articular surface) Moderate (15-30%) Severe (>30%)

17. …… contd. Stage Interpretation 4 Flattening of femoral head Mild (15% of surface) Moderate (15-30%) Severe (>30%) 5 Joint narrowing and/ or acetabular changes Mild (average of femoral head involvement as determined by stage 4 and estimated acetabular involvement) Moderate (average of femoral head involvement as determined by stage 4 and estimated acetabular involvement) Severe (average of femoral head involvement as determined by stage 4 and estimated acetabular involvement) 6 Advanced degenerative changes

18. Marcus radiographic staging of AVN Stages Interpretation Stage 1 Normal or equivalent radiograph, MR imaging or bone scan Stage 2 Sclerotic or cystic leison Stage 3 Crescent sign Stage 4 Sequential collapse, step off in outline of subchondral bone Stage 5 Narrowing of cartilage space with degenerative changes

19. CT scan Evaluate the extent of involvement, such as subchondral lucencies and sclerosis during the reparative stage Osteoporosis is first visible CT scan sign Later, the central bony asterisk is distorted, appearing as clumping and fusion of the peripheral asterisk rays Limitation: Insensitive in detecting stage 0 and 1 AVN

20. Axial computed tomograph scan of a patient with avascular necrosis of the femoral head shows clumping and distortion of the central trabeculae representing the asterisk sign ( arrowhead ) and an adjacent low-density region ( arrow ) representing the reparative zone.

21. Joint space narrowing, juxta-articular sclerosis, and osteophyte formation (degenerative joint disease)

22. MRI Most sensitive means of diagnosing avascular necrosis (AVN) It helps in accurate staging because images clearly depict the size of the lesion, and gross estimates of the stage of disease can be made

23. MRI Advantages of MRI: Allows sequential evaluation of asymptomatic lesions that are undetectable on plain radiographs Facilitates better response to treatment because AVN is diagnosed at an earlier stage, and therapeutic measures are more successful the earlier they are begun. May help guide interventional procedures such as core decompression, May demonstrate response of the femoral head to treatment May detect the joint effusions and bone edema It demonstrates superior soft-tissue resolution, and has high spatial and contrast resolution, allowing evaluation of morphologic features

24. …….MRI MRI of both hips (> 50% - bilateral) Earliest – band form ( low-signal T1 representing separation of normal and ischemic bone) Pathognomonic – double line sign (combination of band form & high-signal-intensity line T2 representing hypervascular tissue) AS quadrant usually affected, although changes seen in all areas of head

25. A Coronal T2-weighted fat suppressed image demonstrates a small focus of avascular necrosis with the double-line sign. The linear high signal intensity inner line (arrow) and dark peripheral line (arrowhead) is typical

26. MRI Coronal plane is the most important imaging plane Sagittal images eliminate partial-volume averaging, which is especially present on axial image When the lesion is located anterosuperiorly , off-coronal images, angled toward the axial plane are preferred T1WIs and T2WIs are obtained in the coronal plane, 4-mm thick, with a 1-mm gap Short tau inversion recovery (STIR) images provide excellent fat suppression and demonstrate areas of bone marrow edema

27. AVN Classification based on MRI Class A Central osteonecrotic focus signal analogous to fat Increased signal on T1WIs intermediate to high signal on T2WIs

28. Class B The presence of central osteonecrotic focus signal analogous to that of blood is observed Increased signal is demonstrated on both T1WIs and T2WIs

29. Class C Coronal fat-saturated T2WI - increased signal within the femoral head and neck ( arrow ), representing edema

30. Coronal T1WI shows decreased signal within the femoral head ( arrow ), representing edema

31. Class D The presence of central osteonecrotic focus signal analogous to that of fibrous tissue Decreased signal is demonstrated on both T1WIs and T2WIs .

32. A T2-weighted coronal image reveals subtle subchondral signal changes within the right femoral head (arrow) compatible with AVN. An associated stress fracture (arrowhead) is noted within the femoral neck

33. T1-weighted coronal image demonstrates a ring-like subchondral area (arrow) present in the anterior-superior femoral head. T1-weighted sagittal image confirms the crescentic subchondral area (arrow) present at the anterior-superior femoral head.

34. Mitchell’s MRI staging Class T1 T2 Definition A Bright Intermediate Fat signal B Bright Bright Blood signal C Intermediate Bright Fluid and edema signal D Dark Dark Fibrosis signal

35. SPECT Cold spot (photon-deficient region) within the femoral head is highly specific for avascular necrosis (AVN) and is the earliest scintigraphic evidence of this disease Increased uptake represent revascularization and repair The central region of photopenia with surrounding zone of increased uptake is termed the doughnut sign

36. A small area of intense uptake at the level of RFH.

37. Perfusion and static planar radionuclide imaging Uptake is decreased in the perfusion and static phases, which represents the early ischemic event Uptake is decreased within the femoral head in the perfusion phase and increased around the cold region in the static phase which represents the reactive zone

38. Bone scan Bone scan of a patient with avascular necrosis of the femoral head shows increased uptake in the superolateral aspect of the right femoral head, indicative of avascular necrosis but providing little information concerning the structural integrity of the hip

39. Bone scan Planar bone scan of the pelvis in a patient with bilateral avascular necrosis of the femoral head shows marked increased uptake of radiopharmaceutical agent in both hips

40. Digital subtraction angiography Detects vessel abnormality Predict head at risk due to abnormal circulation

41. ARCO 1991, committee of nomenclature and staging of the Association Research Circulation Osseous (ARCO) endorsed the staging system developed by the University of Pennsylvania in the 1980s 1992, location of leison as described by Japanese system added 1993, stages 3 and 4 combined as well as stages 5 and 6

42. Thank you