Table 2. Correlation between S.T.O.N.E score and the operation time (OR), the stone clearance rate (SCR.

S.T.O.N.E score	N	OR	P-value	SCR (%)		P-value
				Stone-free	Residual stone
6	17	44.7±13.3	0.000	17 (100)	0	0.001
7	16	55.6±13.9		15 (93.8)	1(6.2)
8	13	63.5±17.2		11 (84.6)	2 (15.4)
9	8	65.6±27.8		6 (75)	2 (25)
10	9	97.3±43.4		5(55.6)	4(44.4)
11	5	98.0±31.9		3 (60)	2(40)
12	3	141.7±22.5		2 (66.7)	1(33.3)
N	71	67.5±32.8		56(78.9)	15(21.1)