Predictors of Operative Duration in Posterior Spinal Fusion for Adolescent Idiopathic Scoliosis: A Retrospective Cohort Study

Article Figures & Data

Table 1

Descriptive statistics of various factors and their correlation with operative duration by bivariate analysis.

Factors	Summary Statistics^{^a}	Operative Duration, min^{^b}, mean ± SD	Association with Operative Duration
Patient-specific factors
Age, y	15.8 ± 3.8	-	0.08 (0.39)^{^c}
Sex			0.83 (0.10)^{^d}
M	42 (32%)	243 ± 68
F	88 (68%)	231 ± 66
BMI	21.1 ± 2.3	-	0.08 (0.39)^{^c}
Cobb angle (of the major structural curve)	64.7° ± 13.6°	-	0.38 (0.0001)^{^c}
Flexibility index (of the major structural curve) (%)	23.9 ± 12.8	-	−0.21 (0.02)^{^c}
C-DAR	8.7 ± 2.1	-	0.13 (0.15)^{^c}
T-DAR	10.3 ± 4.4	-	0.09 (0.32)^{^c}
Thoracic kyphosis	32.3° ± 14.6°	-	0.12 (0.19)^{^c}
Lumbar lordosis	49.2° ± 14.8°	-	0.10 (0.26)^{^c}
Axial rotation (Nash and Moe grade)			3.62 (0.01)^{^d}
1	14 (9.3%)	228 ± 68
2	68 (45.3%)	219 ± 62
3	43 (28.7%)	261 ± 83
4	25 (16.7%)	263 ± 64
Lenke curve type			0.78 (0.50)^{^d}
1	90 (60%)	232 ± 68
2	2 (1.3%)	212 ± 57
3	23 (15.3%)	258 ± 65
4	0	-
5	23 (15.3%)	216 ± 68
6	12 (8%)	248 ± 56
Procedure-specific factors
Number of levels fused	11.8 ± 2.1	-	0.29 (0.003)^{^c}
Number of screws inserted	17.6 ± 3.4	-	0.33 (0.008)^{^c}
Type of osteotomy used			0.14 (0.18)^{^d}
1	118 (78.7%)	235 ± 72
2	25 (16.7%)	229 ± 52
3	5 (3.3%)	254 ± 81
4	2 (1.3%)	264 ± 32
Surgeon-specific factors
Experience of the chief surgeon (y)	6.1 (4.9, 7)	-	−0.36 (0.001)^{^e}
Experience of the first assistant (mo)	39 (26, 58)	-	−0.21 (0.08)^{^e}
Number of assistants	3 (2, 3)	-	−0.12 (0.11)^{^e}

↵a Mean ± SD for continuous variables with normal distribution, median (first quartile, third quartile) for continuous variables with non-normal distribution, frequency/percentage for categorical variables.
↵b Mentioned separately for each group for categorical variables only.
↵c Pearson‘s correlation was used for continuous variables with a normal distribution. Figure in cells denotes the Pearson’s correlation coefficient “r” with P value in brackets.
↵d 1-way analysis of variance used for categorical variables. Figure in cells denotes the ”F” value with P value in brackets.
↵e Spearman’s rank correlation was used for continuous variables with non-normal distribution. Figure in cells denotes the Spearman’s rank correlation coefficient ‘ρ (rho)’ with P value in brackets.
BMI, body mass index; C-DAR, coronal deformity angular ratio; T-DAR, total deformity angular ratio.

Table 2

Significant predictors of operative duration obtained from multivariate regression analysis.

Parameter	Regression Coefficient	Standardized Coefficient (β)	95% CI	P value
Experience of the chief surgeon	−22.3	−0.36	−32.39)−(to −12.23	<0.0001
Cobb angle of the major structural curve	1.5	0.35	0.61–2.52	0.001
Number of screws inserted	6.2	0.28	2.21–10.45	0.002
C-DAR	2.2	0.20	0.24–4.62	0.045
Apical vertebral rotation (Nash and Moe Grade)^{^a}
2	−32.2	−0.21	−78.2 to 12.4	0.10
3	5.3	0.03	−42.9 to 53.2	0.08
4	6.4	0.03	−46.4 to 60.2	0.08