Table 2.

The effect of lumbar level and screw size on three complications

Complication	Size (mm)	L1	L2	L3	L4	L5	p valuea
A (%)	4.5	68.3	53.3	25.5	1.7	0	< 0.001
	5.0	70.5	53.8	26.7	1.7	0	< 0.001
	5.5	71.1	54.4	27.2	1.7	0	< 0.001
	p valueb	0.831	0.971	0.936	1.000	–
B (%)	4.5	16.7	12.7	2.8	1.1	6.7	< 0.001
	5.0	25.5	26.1	12.7	3.3	11.7	< 0.001
	5.5	35.5	34.4	23.8	6.7	16.7	< 0.001
	p valueb	< 0.001	< 0.001	< 0.001	0.019	0.013
C (%)	4.5	3.9	1.1	0	0	0	< 0.001
	5.0	6.7	2.2	0	0	0	< 0.001
	5.5	14.4	7.8	2.8	0	0	< 0.001
	p valueb	0.001	0.002	0.018	–	–

A Spinous process violation, B Screw penetration through the inner wall of pedicle, C Screw penetration through the outer wall of pedicle, L Lumbar

^a Comparison among lumbar levels

^b Comparisons among screw sizes