The Value of Preoperative Systemic Immune-Inflammation Index as a Predictor of Prolonged Hospital Stay in Orthopedic Surgery: A Retrospective Study

Figures & data

Figure 1 Flowchart of the study population.

Abbreviations: LOHS, length of hospital stay; SII, systemic immune-inflammation index.

Table 1 Baseline Demographic and Clinical Characteristics of the Studied Population Grouped According to LOHS

Parameters	All Cohort (n= 196)	Group A (< 21 Days) (n= 134)	Group B (>21 Days) (n= 62)	P value
Age, years	60.00 (45.00)	66.00 (43.50)	59.00 (42.50)	0.07
Male, n (%)	117 (59.7%)	76 (56.7)	41 (66.1)	0.27^a
BMI, kg/m^2	27.92 (8.14)	26.38 (6.14)	28.34 (9.53)	0.14
ASA classification, n (%)
ASA I	6 (3.1%)	3 (2.2)	3 (4.8)	0.041*
ASA II	68 (34.7%)	55 (41.0)	13 (21.0)
ASA III	92 (46.9%)	59 (44.0)	33 (53.2)
ASA IV	28 (14.3%)	16 (11.9)	12 (19.4)
Type of surgery, n (%)
Spinal decompression	54 (27.6)	36 (26.9)	18 (29.0)	0.48
Closed reduction and internal fixation	43 (21.9)	29 (21.6)	14 (22.6)
Arthroplasty	33 (16.8)	25 (18.7)	8 (12.9)
ORIF	29 (14.8)	15 (11.2)	14 (22.6)
Segmental fixation of spine	11 (5.6)	9 (6.7)	2 (3.2)
Correction of spinal deformity	8 (4.1)	6 (4.5)	2 (3.2)
Spinal fusion	6 (3.1)	5 (3.7)	1 (1.6)
Arthroscopy	5 (2.6)	3 (2.2)	2 (3.2)
Others	7 (3.6)	6 (4.5)	1 (1.6)
Laboratory values
Neutrophils, (x10^9/L)	5.89 (5.24)	5.50 (3.91)	6.41 (6.28)	0.14
Platelets, (x10^9/L)	239.00 (164.00)	233.00 (144.25)	274.00 (229.00)	0.21
Lymphocytes, (x10^9/L)	1.52 (1.45)	1.51 (1.26)	1.58 (1.73)	0.38
WBC, (x10^9/L)	8.75 (5.50)	8.58 (4.32)	9.80 (6.15)	0.19
Hemoglobin	116.00 (34.00)	113.00 (38.25)	104.00 (25.50)	<0.001*
Postoperative outcomes
Duration of surgery, minutes	199.00 (179.00)	172.00 (136.75)	225.00 (180.50)	0.015*
ICU admission, n (%)	87 (44.4%)	46 (34.3%)	41 (66.1%)	<0.001*
LOS in ICU, days	2.00 (5.00)	2.00 (4.00)	5.00 (12.00)	0.003*

Notes: *Statistically significant results. Categorical variables are presented as n (%) and compared using Chi-square test or Fisher’s Exact test. Continuous variables are presented as median (IQR) and compared using Mann–Whitney U-test. ^aFisher’s Exact test.

Abbreviations: LOHS, length of hospital stay; BMI, body mass index; ASA, American Society of Anesthesiologists classification system; ORIF, open reduction and internal fixation; WBC, white blood cell; ICU, intensive care unit; LOS, length of stay.

Table 2 Baseline Demographic and Clinical Characteristics of the Studied Population Grouped According to SII Cut-Off Value

Parameters	SII<799.86 (n= 99)	SII≥799.86 (n= 97)	P value
Age, years	58.00 (51.00)	60.00 (40.25)	0.21
Male, n (%)	54 (54.5)	63 (64.9)	0.14^a
BMI, kg/m^2	27.94 (7.38)	27.77 (9.53)	0.93
ASA classification, n (%)
ASA I	2 (2.0)	4 (4.1)	0.21
ASA II	39 (39.4)	29 (29.9)
ASA III	46 (46.5)	46 (47.4)
ASA IV	10 (10.1)	18 (18.6)
Type of surgery, n (%)
Spinal decompression	38 (38.4)	16 (16.5)	0.002*
Closed reduction and internal fixation	17 (17.2)	26 (26.8)
Arthroplasty	17 (17.2)	16 (16.5)
ORIF	9 (9.1)	20 (20.6)
Segmental fixation of spine	2 (2.0)	9 (9.3)
Correction of spinal deformity	7 (7.1)	1 (1.0)
Spinal fusion	4 (4.0)	2 (2.1)
Arthroscopy	2 (2.0)	3 (3.1)
Others	3 (3.0)	4 (4.1)
Laboratory values
Neutrophils (x10^9/L)	3.93 (2.88)	7.77 (5.59)	<0.001*
Platelets (x10^9/L)	226.00 (130.00)	287.00 (209.25)	<0.001*
Lymphocytes (x10^9/L)	1.92 (1.41)	1.25 (1.10)	<0.001*
SII	406.00 (277.93)	1463.55 (1687.42)	<0.001*
WBC (x10^9/L)	6.80 (3.96)	10.45 (6.26)	<0.001*
Hemoglobin	123.00 (35.00)	110.00 (31.00)	<0.001*
Postoperative outcomes
Duration of surgery, minutes	200.00 (133.00)	197.50 (196.50)	0.14
ICU admission, n (%)	39 (39.4)	48 (49.5)	0.19^a
LOS in ICU, days	2.00 (5.00)	2.50 (4.75)	0.91
LOHS, days	17.00 (37.00)	22.00 (25.75)	0.006*

Notes: *Statistically significant results. Categorical variables are presented as n (%) and compared using chi-square test or Fisher’s Exact test. Continuous variables are presented as median (IQR) and compared using Mann–Whitney U-test. ^aFisher’s Exact test.

Abbreviations: SII, systemic immune-inflammation index; BMI, body mass index; ASA, American Society of Anesthesiologists classification system; ORIF, open reduction and internal fixation; WBC, white blood cell; ICU, intensive care unit; LOS, length of stay; LOHS, length of hospital stay.

Table 3 Univariate Linear Regression Analysis of Factors Associated with LOHS

Variable	Standardized β [95% CI]	P value
Age	−0.131 [−0.278 to 0.009]	0.06
Gender	−0.094 [−11.139 to 2.216]	0.19
BMI	0.138 [−0.003 to 0.355]	0.05
ASA	0.210 [2.229 to 11.011]	0.003*
Type of surgery	−0.061 [−1.979 to 0.781]	0.39
Platelets	0.185 [0.009 to 0.061]	0.009*
Neutrophils count	0.081 [−0.371 to 1.361]	0.26
Lymphocytes count	−0.025 [−3.375 to 2.371]	0.73
SII	0.246 [0.002 to 0.006]	<0.001*
WBC	0.044 [−0.560 to 1.064]	0.54
Hemoglobin	−0.324 [−0.494 to −0.205]	<0.001*
Duration of surgery	0.220 [0.016 to 0.070]	0.002*

Note: * Statistically significant results.

Abbreviations: LOHS, length of hospital stay; CI, confidence interval; BMI, body mass index; ASA, American Society of Anesthesiologists classification system; SII, systemic immune-inflammation index; WBC, white blood cell.

Table 4 Multivariate Linear Regression Analysis of Factors Associated with LOHS

Variable	Standardized β [95% CI]	P value
Age	−0.134 [−0.286 to 0.011]	0.07
Gender	−0.057 [−8.752 to 3.302]	0.37
ASA	0.262 [3.882 to 12.672]	<0.001*
SII	0.143 [0.000 to 0.005]	0.031*
Hemoglobin	−0.285 [−0.448 to −0.166]	<0.001*
Duration of surgery	0.260 [0.024 to 0.078]	<0.001*

Note: *Statistically significant results.

Abbreviations: LOHS, length of hospital stay; CI, confidence interval; ASA, American Society of Anesthesiologists classification system; SII, systemic immune-inflammation index.