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postoperative articular surface collapse in both groups (n, %).
| Groups | Cases | 3 months after operation | 6 months after operation | 12 months after operation | 24 months after operation |
|---|---|---|---|---|---|
| Control group | 65 | 5(7.69) | 11(16.92) | 15(23.08) | 18(27.69) |
| Observation group | 65 | 7(10.77) | 13(20.00) | 17(26.15) | 20(30.77) |
| χ2 | 0.091 | 0.051 | 0.041 | 0.037 | |
| P | 0.763 | 0.821 | 0.839 | 0.848 |
