Table 5. Impact of patient and surgery factors on grade 3 violation: Open versus percutaneous screws.

Risk Factor	Incidence grade 3
	Open	Percutaneous	P-value
Age greater than 65 (n = 236)	1.1% (n = 1)	1.4% (n = 2)	0.82
Age less than 65 (n = 322)	2.5% (n = 4)	14.6% (n = 24)	0.0019
Sex (male) (n = 266)	2.4% (n = 3)	8.6% (n = 12)	0.068
Sex (female) (n = 292)	1.6% (n = 2)	8.4% (n = 14)	0.040
BMI greater than 30 (n = 248)	2.4% (n = 3)	13.1% (n = 16)	0.011
BMI less than 30 (n = 292)	1.8% (n = 2)	5.6% (n = 10)	0.16
L4 (n = 222)	0.94% (n = 1)	10.3% (n = 12)	0.0056
L5 (n = 62)	14.3% (n = 4)	38.2% (n = 13)	0.14
1 level (n = 256)	4.0% (n = 5)	16.7% (n = 22)	0.0087
Depth of spine	81.8 ± 2.9	90.3 ± 4.1	0.37