Table 3. Estimated blood loss (mL) by type of procedure and number of levels treated.

Levels	Stand-alone				Pseudoarthrosis				Circumferential (360°)
	N	Mean	SD		N	Mean	SD		N	Mean	SD
All levels	64	74.8	76.1		25	31.5	35.9		84	58.1	70.1
1 level	23	87.5	82.7		12	28.3	40.3		29	41.9	44.6
2 levels	23	62.6	85.5		9	28.8	30.6		21	69.3	114.9
3 levels	16	78.0	54.0		3	46.7	46.2		31	64.4	48.9
4 levels	2	42.5	10.6		1	50.0	–		3	74.5	34.6