Table 4.

Basal category variables according to the drain opening time.

Variable		Category		Time of 12 h %		p-valuea
		N	%	n	%
Gender	male	16	37.2	17	37.8
	female	27	62.8	28	62.2	0.95
	gonarthrosis	35	81.4	39	86.7
Etiology	osteonecrosis	7	16.3	4	8.9	0.5
	arthritis	1	2.3	2	4.4
	white	29	67.4	31	68.9
Skin Color
	mulatto/black	14	32.6	14	31.1	0.88
	II	3	7	2	4.4
	III	18	41.9	17	37.8
Ahlback Classification
	IV	14	32.6	12	26.7	0.6
	V	8	18.6	14	31.1
Angle Deviation	valgus varum	19 24	44.2 55.8	10 35	22.2 77.8	0.028

^a χ2 test or Fisher's Exact test.

SD: Standard Deviation; Student's paired t –test or Mann-Whitney test.

Source: Hospital Santa Teresa.