| Risk factors | Frequencies (%) |
| Sickle cell disease | 12 (23.5) |
| Trauma | 10 (19.6) |
| Alcoholism | 3 (5.9) |
| Athletism | 3 (5.9) |
| Steroids | 2 (3.9) |
| HIV infection | 2 (3.9) |
| Dyslipidemia | 1 (1.9) |
| Hyperuricemia | 1 (1.9) |
| Systemic lupus erythematosous | 1 (1.9) |