Abstract
Introduction
Osteonecrosis (ON) is a bone disease characterized by death of osteocytes and loss of associated hematopoietic elements usually occurring as focal lesions in weight bearing joints such as the hip. The pathophysiology of the disease is still unclear and osteonecrosis can be viewed as both a vascular and a bone disease. The number of mesenchymal stem cells (precursors of osteoblastic cells) has been shown to be depressed in patients with osteonecrosis. Also, the proliferation rate of the osteoblastic cells in the proximal femur may be depressed. These findings raised the possibility that osteonecrosis might be a disease of bone cells or bone metabolism. On this basis, we started this study to evaluate bone metabolism status among patients with osteonecrosis.
Methods
In a prospective study, we evaluated 110 patients with osteonecrosis at the time of the diagnosis for vitamin D, parathormone, osteocalcin, and c-telopeptide measurements. DEXA was performed in all patients as well. We excluded from this study patients with sickle cell anemia (n=5), Gaucher disease (n=1), on hemodialysis (n=14), and who were already treated for osteoporosis (n=8).
Results
There were 20 women and 90 men (mean age 47 ± 11 years). Twenty percent of the patients had unilateral osteonecrosis of the femoral head, 61 % of the patients had bilateral osteonecrosis, and 20 % had multifocal disease. Risk factors were corticosteroid and alcohol abuse. Vitamin D deficiency (<15 ng/ml) was found in 60 % of the patients and vitamin D insufficiency (15 to 30 ng/ml) was found in 15% of the patients. Secondary hyperparathyroidism (>55pg/ml) was present in only 7 patients. Patients with alcohol abuse had significantly lower vitamin D concentration than the other patients: 11.9 ± 8.7 vs. 20.8 ± 9.2 ng/ml (p=0.005). Among 90 samples, 45 showed an osteocalcin level below the normal range (<14 ng/ml). Most of the patients had a normal level of C-telopeptide. Patients with corticosteroid-associated osteonecrosis had significantly lower osteocalcin levels than others osteonecrotic patients: 14.1 ± 5.3 vs 22.7 ± 13.0 ng/ml (p=0.015). Bone mineral density measurements were obtained for 60 patients and showed a T-score < -1.5 at the lumbar site and < 1.8 at the hip.
Conclusion
Patients with osteonecrosis have a high prevalence of vitamin D deficiency without secondary hyperparathyroidism. They also display a low bone turnover confirmed by low osteocalcin levels and normal levels of C-telopeptide. Osteonecrosis is also associated with severe osteopenia.
