NATURAL HISTORY OF OSTEONECROSIS OF THE FEMORAL HEAD

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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 precollapse staging in future

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