1. NATURAL HISTORY OF OSTEONECROSIS OF THE FEMORAL HEAD Prediction Based on MRI
Daniel J. Berry, MD
Professor and Chairman
Dept of Orthopedic Surgery
Mayo Clinic
Rochester, MN, USA

2. NATURAL HISTORY OF OSTEONECROSIS Introduction
The natural history of osteonecrosis is important to understand
We cannot evaluate the value of head sparing treatments unless we know what happens in untreated patients

3. NATURAL HISTORY OF OSTEONECROSIS Introduction
We understand the natural history for patients with later stage disease
crescent sign 
head collapse 
arthritis

4. NATURAL HISTORY OF OSTEONECROSIS Introduction
The natural history of pre-collapse disease (ARCO Stage 0-2) has been less certain
Why?

5. NATURAL HISTORY OF OSTEONECROSIS Hypothesis
Intuitively:
The size and location of lesion at presentation (burden of disease) effects the natural history of the disease

6. NATURAL HISTORY OF OSTEONECROSIS Hypothesis
This hypothesis has been tested and demonstrated to be true sometime ago
In fact: 32 years ago

7. NATURAL HISTORY OF OSTEONECROSIS Data
Surface Arc measurements on plain films demonstrate extent of necrosis:
Head involvement by surface arc correlates with prognosis
Kerboul et al, JBJS (B), 1974

8. NATURAL HISTORY OF OSTEONECROSIS Introduction
Limitations of early studies:
-Diagnostic tools limited
-Osteonecrosis patients potentially mixed with other diagnoses
-Extent of disease difficult to measure on plain radiographs

9. NATURAL HISTORY OF OSTEONECROSIS MRI
Clear diagnostic criteria
Clear methods of measuring extent of disease
MRI now available for sufficient time duration to correlate findings with natural history of disease

10. NATURAL HISTORY OF OSTEONECROSIS Data
31 Hips, Treated with Core:
Measured lesion volume
Holman et al, J Rheum, 1995

11. NATURAL HISTORY OF OSTEONECROSIS Data
Outcome of Core (1 yr):
Volume <21%:
- Good: 14/15 (93%)
Volume >21%:
- Good: 0/16 (0%)
Holman et al, J Rheum, 1995

12. NATURAL HISTORY OF OSTEONECROSIS Data
37 Hips, MRI:
Lesion size by arc measurements
Applied Kerboul method to MRI
Koo, Kim, JBJS(B), 78, 1996

13. NATURAL HISTORY OF OSTEONECROSIS Data
Risk of Collapse:
Correlated to lesion size by arc measurement
Koo, Kim, JBJS(B), 78, 1996

14. NATURAL HISTORY OF OSTEONECROSIS Data
Risk of collapse:
Small lesion: 1
Medium lesion: 18.5
Large lesion: 48.5
Koo, Kim, JBJS(B), 78, 1996

15. NATURAL HISTORY OF OSTEONECROSIS Data
MRI, 39 Hips, Pre-collapse:
Measured lesion volume
Index of necrotic extent
Cherian et al, JBJS(A) 85, 2003

16. NATURAL HISTORY OF OSTEONECROSIS Data
Survivorship Analysis: Correlations:
Lesion volume (p<0.05)
Index of necrotic extent (p=0.007)
Cherian et al, JBJS(A) 85, 2003

17. NATURAL HISTORY OF OSTEONECROSIS Data
MRI, 65 Hips, Pre-collapse: 2 yr(+) F/U:
Measured lesion volume
Measured lesion location
Nishi et al, JOR 20(1), 2002

18. NATURAL HISTORY OF OSTEONECROSIS Data
Lesion Volume:
Over 30% of head
collapse in 24/30 (80%)
Less than 30% of head
- collapse in 9/35 (26%)
Nishi et al, JOR 20(1), 2002

19. NATURAL HISTORY OF OSTEONECROSIS Data
Lesion Volume: collapse risk
<15%: 6%
15-30%: 42%
>30%: 80%
Nishi et al, JOR 20(1), 2002

20. NATURAL HISTORY OF OSTEONECROSIS Data
Lesion Location:
Collapsed hips:
- Correlated to anterosuperior head location
Nishi et al, JOR 20(1), 2002

21. NATURAL HISTORY OF OSTEONECROSIS Data
Lesion Location:
Even small to medium sized lesions in antero-superior portion of femoral head exhibited collapse risk
Nishi et al, JOR 20(1), 2002

22. NATURAL HISTORY OF OSTEONECROSIS Remaining Questions
How do patient factors effect the natural history (if at all)?
etiology of osteonecrosis
ongoing stimulus (ETOH, steroids)
patient age, gender, etc

23. NATURAL HISTORY OF OSTEONECROSIS Remaining Questions
How does lesion size/location on MRI predict long-term outcome?
Studies to date are short-term

24. NATURAL HISTORY OF OSTEONECROSIS Conclusions
MRI can be used to quantitate lesion location and size
Lesion location and size are powerful predictors of natural history
Will be the basis of pre-collapse staging in future

25. NATURAL HISTORY OF OSTEONECROSIS Conclusions
Future studies of head sparing procedures will need to be stratified according to amount of head involvement by MRI