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Conditions before collapse of the contralateral hip in osteonecrosis of the femoral head.

BACKGROUND
Osteonecrosis of the femoral head is a disease which may cause rapid femoral head collapse in relatively young patients. Clinical results of prosthesis replacement in osteonecrosis patients are generally poorer than in age-matched patients with other diagnoses. The ultimate goal in treating these patients is therefore to preserve not replace the involved femoral head. The purposes of this study were to analyze outcomes by examining osteonecrotic hips before collapse and to justify the role of early surgical intervention for osteonecrosis of the femoral head.


METHODS
Between 1993 and 1997, there were 275 consecutive patients with osteonecrosis of the femoral head who received joint replacement on 1 side. Among these patients, 100 contralateral hips with evidence of osteonecrosis in the stage before collapse were included in this study. Demographic information, laboratory data, and radiographs were reviewed and compared between patients whose collapse time was less than 1 year, between 1 and 2 years, and more than 2 years, and those who had no collapse at the latest follow-up.


RESULTS
At the final follow-up, the overall collapse rate was 78%, and the collapse time was generally within 2 years. Patients with younger age (less than 50 years old), higher activity levels, and higher serum triglyceride levels were at higher risk of rapid collapse.


CONCLUSION
In conclusion, we found that the disease progression rate is high in patients who have bilateral femoral head involvement. Early surgical intervention to preserve the femoral head should be adopted to prevent early femoral head collapse in these patients. In addition, risk factors such as high activity levels and abnormal lipid metabolism should also possibly be addressed in the therapeutic modality.