Difference in the volume between the osteonecrosis of the two hips and time before collapse for the 30 hips evaluated as stage I at the beginning of the study. The time is the difference in months between the date of the radiograph showing collapse and the radiograph done at the first evaluation. Patients are ordered by increasing difference in volume between osteonecrosis in the two hips
| Patient No | Difference in volume between osteonecrosis in the two hips (cm3) | Time in months before stage III |
| 7 | −0.9 | 4 |
| 2 | 1.8 | 6 |
| 9 | 3.1 | 6 |
| 14 | 4.2 | 5 |
| 8 | 4.5 | 5 |
| 24 | 5 | No collapse |
| 10 | 7.4 | 10 |
| 30 | 7.9 | |
| 3 | 8.2 | 9 |
| 20 | 8.6 | 9 |
| 21 | 8.6 | 8 |
| 1 | 10.1 | 13 |
| 4 | 10.1 | No collapse |
| 6 | 10.2 | 12 |
| 5 | 11.4 | 15 |
| 19 | 11.5 | 12 |
| 15 | 14.2 | 14 |
| 22 | 15.1 | 17 |
| 12 | 15.4 | No collapse |
| 11 | 16.6 | 12 |
| 23 | 16.7 | 18 |
| 28 | 17.4 | 18 |
| 13 | 18.8 | 20 |
| 18 | 19.6 | 16 |
| 25 | 23.7 | 8 |
| 27 | 26.5 | No collapse |
| 29 | 28 | 23 |
| 26 | 31.2 | No collapse |
| 17 | 36 | No collapse |
| 16 | 37.6 | No collapse |