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Numbers of CPS with complete perforation and partial perforation in each period
| Period E (92 screws) | Period M (100 screws) | Period L (88 screws) | χ2 test | |
|---|---|---|---|---|
| PP (n) | 6 | 7 | 1 | NS |
| CP (n) | 5* | 0a | 0a | P < 0.01 |
| CP + PP (n) | 11# (12.0%) | 7a (7.0%) | 1# (1.1%) | P < 0.05 |
CPS cervical pedicle screw, PP partial perforation, CP complete perforation, NS not significant in χ2 test
aNot significant in Haberman’s residual analysis
* P < 0.01 in Haberman’s residual analysis
#P < 0.05 in Herberman’s residual analysis
