Table 1.

Characteristics of Studies Included in Review.

Author	Study Design	Analysis	Level of Evidence	Group Demographics (Overall)			Group Demographics (Infected)		Group Demographics (Control)—If Applicable		Significant Variables	Non-significant Variables	Spinal levels	Approach	Instrumentation?	Indication for Surgery	Surgical Procedure
				Number of Patients	Mean Age (y)	Special Characteristics	Number of Patients	Mean Age (y)	Number of Patients	Mean Age (y)
Abdul-Jabbar et al4 2012	Retro, Cohort	Uni-/multivariate logistic regression	III	6628	56.5	Administrative claims database	193		6435		Sacral involvement, number of levels fused (>7), bone or connective tissue cancer, approach (A/P combined)	CAD, DM, surgical region, smoking, obesity, IA, diagnosis, transfusion, procedure type	C/T/L	A/P/Comb	Some	Degenerative, deformity, tumor	Decompression, fusion, deformity
Aoude et al5 2016	Retro, Cohort	Multivariate logistic regression	III	13 695	NS	NSQIP database, focused on blood transfusion					Transfusion (lumbar fusion only, not thoracic)	—	T/L	A/P/comb	Y	NS (excluded trauma)	Fusion
Asomugha et al6 2016	Retro, Controlled-Cohort	Multivariate logistic regression	III	238							Epidural steroid paste, renal disease, immunosuppression	Procedure type, preoperative admission to hospital, surgical duration, EBL, durotomy, CHF, age, BMI, HTN, CAD, smoking, asthma, COPD	L	P	N	Degenerative	Decompression
Atkinson et al7 2016	Retro, Cohort	Uni-/bivariate logistic regression	III	152	60.6	Spinal metastases					Number of levels operated, surgical region (thoracic)	Age, gender, emergency surgery, Waterlow score, BMI, EtOH, smoking, ASA, preoperative albumin, preoperative protein, preoperative WBC, preoperative CRP, incision length, interval between admission and surgery, number of staff in operating room	C/T/L	A/P	NS	Metastases	NS
Babu et al8 2012	Retro, Cohort	Uni-/multivariate logistic regression	IV	20	47	Tracheostomy/ACDF for SCI					—	Early tracheostomy	C	A	Y	Trauma, degenerative	Decompression, fusion
Barnes et al9 2012	Retro, Cohort	Multivariate logistic regression	III	90	44.8		15		75		Philadelphia collar, trauma	—	C	P	Y	Trauma, degenerative	Decompression, fusion
Berney et al10 2008	Retro, Cohort	ANOVA	III	71	40.28 ± 19.22	Tracheostomy in SCI (quadriplegia)					—	Early tracheostomy	C	A/P/comb	Y	Trauma	Fusion
Blam et al11 2003	Retro, Cohort	Uni-/multivariate logistic regression	III	256	43	Trauma	24	55	232	37	Delay to surgery (>160 hours), postoperative ICU stay (>1 day), number of surgical teams (orthopedic only vs combined orthopedic/neurosurgery)	Gender, race, BMI, drug use, smoking, open injury/abrasion at surgical site, GCS, ASA, albumin, steroid use, EBL, surgical duration, bone graft use, instrumentation, approach	C/T/L	A/P/comb	Y	Trauma	Decompression, fusion
Bohl et al12 2016	Retro, CCS	Multivariate Poisson regression	III	10 825	NS	NSQIP database, focused on malnutrition					Albumin (<3.5 g/dL)	—	L	P	NS	Degenerative, deformity	Fusion
Boston et al13 2009	Retro, CCS	Multivariate logistic regression	III				55	44	179	45	Surgical duration, presence of comorbidities	Workers’ compensation, method of hair removal, smoking, incontinence	NS	NS	NS	NS	Fusion, laminectomy, other
Browne et al14 2007	Retro, Cohort	Multivariate logistic regression	III	197 461	48.95 ± 18.16	Focused on DM					DM	—	L	?	?	Degenerative, deformity	Fusion
Chaichana et al15 2014	Retro, Cohort	Multivariate logistic regression	III	817	56 ± 14		37		780		Age (>70 y), DM, obesity, prior spine surgery, LOS (>7 days)	Smoker, number of levels operated, number of levels fused, number of levels decompressed, CSF leak, perioperative DVT/PE	L	P	Y	Degenerative	Decompression, fusion
Chen et al16 2009	Retro, Cohort	Multivariate logistic regression	II	244	NS						DM, EBL	Age, gender, BMI, surgical duration, ASA, antibiotic redosing, bone allograft use, drain placement, smoking	L	P	Y	Degenerative, deformity	Fusion
Chen et al17 2011	Retro, Cohort	Uni-/multivariate logistic regression	III	45	49.6	Sacral chordoma	16				Albumin, prior surgery, surgical duration (>6 hours)	Gender, obesity, smoking, alcohol, DM, tumor size, radiation, instrumentation	S	P	Some	Tumor (sacral chordoma)	Tumor resection
Cizik et al3 2012	Retro, Cohort	Multivariate logistic regression	III	1532	49.5		63	53.5	1469	49.4	BMI (>35 kg/m2), HTN, surgical region (thoracic, lumbosacral), SII (>21), renal disease	Revision, primary diagnosis, bleeding disorder, RA, liver disease, cancer, PVD, asthma, COPD, CVA, CHF, MI, smoking	C/T/L	A/P/comb	Some	Degenerative, tumor, trauma	Decompression, fusion, deformity correction
De La Garza Ramos et al18 2015	Retro, Cohort	Student’s t test, chi-square, univariate analysis, log-binomial model	IV	732	NS	Focused on obesity					Obesity	—	L	P	Y	Degenerative	Fusion
De La Garza Ramos et al19 2016	Retro, Cohort	Multivariate logistic regression	III	36 440	NS		264	61.2 ± 11.6	36 176	60.5 ± 11.9	Chronic steroid use, surgical duration, renal disease (lumbar only), hemato-oncological disease (lumbar only), DM (lumbar only), obesity (lumbar only), LOS (lumbar only)	CAD, respiratory disease, hepatobiliary disease, neurologic disease, smoking	C/L	A/P/comb	Some	Degenerative	Decompression or fusion
De La Garza Ramos et al20 2017	Retro, CCS	Multivariate logistic regression	III	293	NS	Three-column osteotomy complex spine deformity	15	57 ± 14	278	61 ± 13	Obesity (class II), multilevel 3-column osteotomy	Bleeding disorder, type of deformity, ASA, anemia	T/L	NS	Y	Deformity	Deformity correction and fusion
Demura et al21 2009	Retro, Cohort	Uni-/multivariate logistic regression	III	113	56	Spinal metastases	8		113		DM, preoperative radiation	Age, gender, nutrition, ASA, chemotherapy, steroid use, neurologic deficit, emergency surgery, procedure type (en bloc vs debulking versus palliative)	C/T/L	NS	NS	Spinal metastases	Decompression, fusion, tumour resection (en bloc, debulking)
Dubory et al22 2015	Pro, Cohort	Uni-/multivariate logistic regression	II	518	47.8 ± 19.1	Acute spinal trauma injury	25		493		Age, DM, surgical duration	BMI, number of levels operated, EBL, approach, neurologic decomp, intraoperative transfusion, bladder catheter, NNIS	C/T/L	A/P	Y	Trauma only	Decompression/fusion
Ee et al23 2014	Retro, CCS	Multivariate logistic regression	III				27	61.6 ± 13.7	162	56.8 ± 14.9	Open surgery (compared with MIS), DM, number of levels operated, BMI	Age, surgical duration, preoperative glucose level, gender, race, number of surgical assistants, allograft use, instrumentation, L5-S1 involvement, EtOH, steroid use, smoking, ASA	L	P	Some	NS	Decompression or fusion
Fang et al24 2005	Retro, CCS	Uni-/multivariate logistic regression	III			Both adult and pediatric patients; only including adult results	21		29		Age (>60 y), prior infection, EtOH	Prior surgery, steroid use, smoking, BMI, gender, instrumentation, allograft use, EBL, staged procedures, surgical duration, number of levels operated	C/T/L/S	A/P/comb	Some	Deformity, degenerative, disc disease	Decompression, fusion, discectomy, deformity correction, ACDF, other
Fehlings et al25 2012	Pro, Cohort	Pearson chi-square, multivariate regression	II	302	57	Cervical spondylotic myelopathy					Approach (posterior)	Procedure type (laminoplasty vs posterior decompression and fusion)	C	A/P/comb	Some	Cervical spondylotic myelopathy	ACDF, corpectomy, decompression and fusion, laminoplasty
Fisahn et al26 2017	Retro, Cohort	Chi-square	III	56	NS	Major deformity surgery (>8 level fusion), focused on allogeneic transfusion					Allogenic transfusion	—	C/T/L	P	Y	Degenerative, deformity	Fusion
Glassman et al27 2016	Retro, Cohort	Binary logistic regression	III	2653	NS	Based on 3 databases (Denmark, Japan, United States)					Gender, LOS, BMI, number of levels fused	Diagnosis, age, smoking, ASA, surgical duration	L	A/P/lateral/? comb	NS	Degenerative	Fusion
Golinvaux et al28 2014	Retro, Cohort	Multivariate logistic regression	III	15 480	NS	NSQIP database, focused on DM (insulin vs non–insulin dependent)					Insulin-dependent DM (vs non–insulin dependent)		L	A/P/lateral/? comb	NS	NS	Fusion
Gruskay et al29 2012	Retro, Cohort	Step-down binary logistic regression	III	6666	NS						Case order (in lumbar decompression only), approach (posterior, in cervical or lumbar fusion only), revision (cervical only), surgical duration (lumbar decompression or fusion), ASA (lumbar fusion only), age (lumbar fusion only)	Surgical duration (cervical only), age (lumbar decompression or cervical only), ASA (lumbar decompression or cervical only), gender, revision (lumbar decompression or fusion only)	C/L	A/P	Some	Degenerative, deformity	Decompression, fusion
Haddad et al30 2016	Retro, Cohort	Multivariate logistic regression	III	1 872 327	NS	NIS database					Age, gender (male), race (African American), hospital size (medium or large), hospital type (rural), approach (posterior or combined), trauma, neurologic injury (SCI or myelopathy)	Payer (self-pay vs Medicare), hospital region, calendar year	C	A/P/comb	Yes	Degenerative, trauma, cervical myelopathy	Decompression, fusion, stabilization
Hayashi et al31 2015	Retro, Cohort	Multivariate logistic regression	III	125	53.8	Total en bloc spondylectomy for vertebral tumor (primary or metastases)	8		117		Instrumentation, approach (A/P combined)	Age, tumor histology, prior surgery, surgical duration	NS	A/P/comb	Y	En bloc spondylectomy	Fusion, en bloc tumor resection
Hijas-Gomez et al32 2017	Retro, Cohort	Uni-/multivariate logistic regression	III	892	55		35	61	857	54	DM, COPD, dirty surgery, surgical duration (>75th percentile)	Gender, obesity, renal disease, cancer, malnutrition, cirrhosis, immunodeficiency, neutropenia, transfusion, emergency surgery, razor shaving, inappropriate antibiotic prophylaxis, drains	C/T/L	A/P/comb	Some	Degenerative, disc disease, cervical myelopathy, deformity, other NS	Decompression, fusion
Hikata et al33 2014	Retro, Cohort	Chi-square, Mann-Whitney, Fisher’s exact tests	III	347	NS						DM, preoperative HbA1c	Age, gender, BMI, obesity, preoperative LOS, insulin use, steroid use, prior surgery, preoperative muscle weakness, preoperative incontinence, number of levels fused, surgical duration, EBL, transfusion	T/L	P	Y	Degenerative, deformity	Fusion
Jalai et al34 2016	Retro, Cohort	Multivariate logistic regression	III	3057	60.71	NSQIP database	35	56.54	3022	60.75	Approach (posterior), surgical duration (>208 min), ASA (>3)	Smoking, steroid use, comorbid conditions, obesity, DM	C	A/P/comb	Y	Cervical spondylotic myelopathy	Decompression, fusion
Kanafani et al35 2009	Retro, Cohort	Chi square, T-test	III	997			27	59	54	47	DM, instrumentation, age	Gender, prior surgery, diagnosis, surgical duration, antibiotic duration	NS	NS	Y	Disc disease and tumor	Decompression, fusion
Keam et al36 2014	Retro, Cohort	Student’s t test, Wilcoxon rank-sum test, chi-square, Fisher’s exact test	III	165	NS	Spinal metastases with preoperative radiation					—	Type of preoperative radiation (conventional XRT versus hypofractionated)	C/T/L/S	A/P/comb	Some	Tumor/metastases	Decompression, fusion, stabilization, tumor resection
Kerwin et al37 2008	Retro, Matched cohort	Student’s t test	III	16 812	NS	Spinal fracture					—	Time to surgery	C/T/L	C/T/L	NS	Trauma	Stabilization
Kim et al38 2014	Retro, Cohort	Multivariate logistic regression	III	4588	NS	NSQIP database, focused on surgical duration					Surgical duration	—	L	A/P/lateral/comb	Y	NS (excluded trauma)	Fusion (single-level)
Kim et al39 2017	Retro, Cohort	Multivariate logistic regression, single variate t test	III	1831	NS		30	63.7	1801	63.6	Surgical duration	Gender, local bone irrigation, intradiscal irrigation	L	P	Y	NS	Fusion (PLIF)
Klekamp et al40 1999	Retro, CCS	Chi-square, Fisher’s exact test	III	2614	NS						Lymphopenia, chronic infection, EtOH, recent hospitalization, steroid use	DM, weight, gender, trauma, inpatient status, smoking, UTI, age, cholesterol, albumin, total protein, ESR, triglycerides	C/T/L	NS	Some	NS	NS
Klemencsics et al41 2016	Pro, Cohort	Multivariate logistic regression	II	1030	50		37		993		Age, BMI, DM, CAD, arrhythmia, chronic liver disease, autoimmune disease	SII, instrumentation	L	P	Y	Degenerative	Decompression, fusion
Koutsoumbelis et al42 2011	Retro, Cohort	Multivariate logistic regression	II	3218	56.9		86	60			Gender (female), DM, osteoporosis, CAD, number of comorbidities, obesity, number of personnel in operating room, dural tear, EBL (>500 cm3)	Age, smoking, HTN, cholesterol, OSA, CHF, RA, number of comorbidities, number of surgeons, number of residents or fellows, surgical duration, number of drains, LOS, revision	L	P	Y	NS (excluded infection)	Fusion (PLIF)
Kudo et al43 2016	Retro, Cohort	Chi-square and Mann-Whitney U	III	105	64.4	Infection based on CRP	35	65.9 ± 16.9	70	63.6 ± 14.2	Surgical duration	Age, gender, BMI, smoking, EtOH, DM, EBL, instrumentation, preoperative total lymphocyte, preoperative transferrin, preoperative prealbumin, preoperative retinol binding protein	C/T/L	NS	NS	NS	NS
Kukreja et al44 2015	Retro, Cohort	Multivariate logistic regression	III	266 439	55.6						Emergency surgery, timing of surgery (after day of incident in emergency cases)	—	L	A/P/comb	Some	Degenerative, deformity, metastases, trauma	Fusion
Kumar et al45 2015	Retro, Cohort	Multivariate logistic regression	III	98	60.1	Spinal metastases	17		81		Number of levels operated (≥7), albumin (low), neurologic disability (trend)	Absorbable skin closure material, age, lymphocyte count, perioperative steroids, MUST	NS	P/comb	NS	Spinal metastases	NS
Kurtz et al46 2012	Retro, Cohort	Kaplan-Meier survival analysis, Cox regression	III	15 069	NS	Medicare database					Age, obesity, Charleston comorbidity index, socioeconomic status, revision, number of levels fused, approach	Gender, race, smoking, DM, allograft use, transfusion	L	A/P/comb	Y	NS	Fusion
Lee et al47 2014	Retro, Cohort	Pearson chi-square, Fisher’s exact test, multivariate logistic regression	III	1532	49.5	Spine End Result Registry (SEER)	66				SII, DM, CHF	Age, gender, RA, trauma, BMI	C/T/L	NS	NS	NS	NS
Lee et al48 2016	Retro, Cohort	Multivariate logistic regression	III	149	53.5 ± 15.8						Maximum fat thickness (T12-L5, operated levels or L4), prior surgery	Age, DM, smoking (within 1 y), preoperative albumin, BMI, obesity, number of levels operated, surgical duration	L	P	Some	NS	Decompression, fusion
Li et al49 2013	Retro, Cohort	Multivariate logistic regression	III	387	46.4	Sacral tumors					Prior radiation, rectum rupture, surgical duration, CSF leak	Age, gender, DM, preoperative albumin, prior sacral tumor resection, tumor size, histopathological diagnosis, blood control method, incision type (Y vs 2-way), proximal sacral segment resected, instrumentation, EBL	S	A/P/comb	Some	Primary tumor	Tumor resection
Lieber et al50 2016	Retro, Cohort	Multivariate logistic regression	III	60 179	57.1	NSQIP database	1110		59 069		Gender (female), inpatient, BMI, preoperative steroid use, anemia, ASA (>2), surgical duration	Instrumentation, bone graft use, transfusion, DM, functional status, COPD, disseminated cancer, weight loss, preoperative transfusion, dialysis, deformity, hematocrit	C/T/L	A/P/lateral/comb	Some	NS (excluded trauma)	NS
Lim et al51 2014	Retro, Cohort	Chi-square	III	3353		NSQIP database	86				Obesity, ASA (>2), surgical duration (>6 hours)	Smoking, DM	L	A/P/lateral/comb	Y	NS (excluded trauma)	Fusion (single-level)
Lonjon et al52 2012	Pro, Cohort	Univariate, Fisher’s exact test/Wilcoxon test	IV	169	50.0 ± 20.1	Spinal trauma					Age, ASA, DM, surgical duration (>3 hours), time from injury to surgery (>3 days), number of levels fused, EBL (>600 cm3), urinary catheter (>5 days)	Gender, BMI, smoking, EtOH, antiplatelet agent/anticoagulant use, spinal region of trauma, neurologic impairment, surgical time of day (day vs night), approach, MIS, intraoperative transfusion, bedrest duration, drain	C/T/L	A/P/comb	Y	Trauma	Decompression, stabilization
Manoso et al53 2014	Retro, Cohort	Multivariate logistic regression	III	1532							SII, CHF, payer (Medicaid), DM	Age, gender, smoking, EtOH, drug use, BMI, medical comorbidity, prior surgery, primary diagnosis, spinal region, approach	C/T/L	A/P/comb	Some	Degenerative, trauma, tumor/metastases, infection, deformity, other	Decompression, fusion, stabilization, deformity correction, tumor resection
Maragakis et al54 2009	Retro, CCS	Multivariate logistic regression	III				104	55.3	104	55.3	Surgical duration, ASA (≥3), surgical region (lumbo-sacral), approach (posterior), instrumentation, obesity, razor shaving before surgery, intraoperative administration of inspired O2 <50%	Age, gender, race, smoking, DM, CAD, Karnofsky score, prior surgery, emergent/urgent surgery, appropriate timing of antibiotic prophylaxis, intraoperative nitrous oxide administration, perioperative glucose, intraoperative temperature, intraoperative infusion rate, dural tear, CSF leak, transfusion	NS (included L/S)	A/P/? comb	Some	NS	Decompression, fusion
Marquez-Lara et al55 2014	Retro, Cohort	Chi-square, Student’s t test	IV	24 196	NS	Focused on BMI					BMI (>24.99 kg/m2)	—	L	A/P/comb	Some	NS	Decompression, fusion
Martin et al56 2016	Retro, Cohort	Multivariate logistic regression	III	35 777		Focused on smoking					Smoking	—	L	A/P	Some	NS	Decompression, fusion, deformity correction
Mehta et al57 2012	Retro, Cohort	Student’s t test, Wilcoxon signed-rank test, chi-square, logistic regression	III	298			24	56	274	60	Number of levels operated, obesity, skin to lamina distance, thickness of subcutaneous fat	BMI, DM	L	P	Y	NS	Decompression, fusion
Murphy et al58 2017	Retro, Cohort	Multivariate logistic regression	III	8744	65	Focused on age					—	Age	L	P	N	Degenerative	Decompression
Northrup et al59 1995	Retro, Case series	None	IV	11	30	Tracheostomy in SCI (quadriplegia)					—	Tracheostomy pre-anterior cervical fusion	C	A	Some	Trauma	Decompression, fusion
Ogihara et al60 2015	Pro, Cohort	Fisher’s exact test, Wilcoxon signed-rank test, multivariate logistic regression	III	2736			24				Steroid use, surgical duration (>3 hours), gender (female)	BMI, ASA, DM, smoking, prior surgery, instrumentation, emergency surgery, intraoperative fluoroscopy, dural tear, iliac crest bone graft, surgical region	T/L	P	Some	Trauma, disc disease, degenerative, tumor/metastases, deformity	NS
Ohya et al61 2017	Retro, Cohort	Multivariate logistic regression	III	47 252	65.4	Japanese Diagnosis Procedure Combination Database, focused on effect of month of surgery	438		46 814		Month of surgery (timing when medical staff rotate, only in academic hospitals)		C/T/L	A/P/comb	Y	NS	Decompression, fusion
Oichi et al62 2017	Retro, Matched-pair cohort	Multivariate logistic regression	III	6921		Focused on Parkinson’s disease					Parkinson’s disease	—	C/T/L	A/P/comb	Some	NS	NS (included fusion)
Ojo et al63 2016	Retro, Cross-section	Fisher’s exact test	IV	62	44.2		10				DM, surgical region (cervical), procedure type (laminectomy and fixation), surgical duration	Obesity, TB, anemia, diagnosis, instrumentation	C/L	P	Some	Trauma, degenerative, tumor	Decompression, instrumentation, tumor resection
Olsen et al64 2003	Retro, CCS	Uni-/multivariate logistic regression	III	219			41	54.3	178	52.9	Postoperative fecal incontinence, approach (posterior), tumor resection, obesity (morbid)	Fusion, timing of prophylactic antibiotics, trauma surgery, intraoperative hypothermia, dural tear, instrumentation	C/T/L	A/P/comb	Y	Degenerative, tumor, trauma	Decompression, fusion, tumor resection
Olsen et al65 2008	Retro, CCS	Multivariate logistic regression	III	273	52.4		46		227		DM, timing of prophylactic antibiotics (>1 hour before surgery), preoperative glucose (>125), postoperative glucose (>200), obesity, number of residents (≥2)	Fusion, instrumentation, bone graft use, irrigation with antibiotic solution, number of levels operated, surgical duration, hemovac, intraoperative steroid, number of levels, BMI, diagnosis, transfusion, approach	NS (included C)	A/P/comb	Y	NS	Decompression, fusion
Omeis et al66 2011	Retro, Cohort	t test, chi-square	III	678		Nonsacral tumor (primary or metastases)	65	52.1	613	47.4	Prior surgery, preoperative radiation, any comorbidity, number of surgical teams involved (>1), complex plastics closure, LOS, hospital acquired infection	Gender, race, age, albumin, steroid use, intra versus extradural, metastatic versus primary, allograft use, instrumentation	C/T/L/S (LS junction, not primary S)	A/P/comb	Some	Tumor/metastases	Tumor resection
Pull ter Gunne et al1 2009	Retro, Cohort	Cochran/Mantel-Haenszels chi-square, multivariate	III	3174	55.6 ± 15.5						Obesity, approach (not anterior), DM, prior SSI, EBL (>1 L), surgical duration (>2 hours)	Gender, HTN, prior surgery, diagnosis, number of levels fused, procedure type	C/T/L/S	A/P/comb	Some	Hardware irritation, trauma, disc herniation, degenerative, deformity, stenosis, tumor/metastases, arthritis, pseudoarthrosis	Discectomy, decompression, fusion, deformity correction, ROH, debridement, soft tissue
Pull ter Gunne et al67 2010 (deformity)	Retro, Cohort	Chi-square, multivariate	III	830	55.4 ± 16.1	Adult spinal deformity					Obesity, history of SSI	Gender, DM, NSAID use, HTN, other cardiovascular pathology, smoking, preoperative protein, preoperative albumin, prior surgery, number of levels fused, approach, procedure type, surgical region, surgical duration, EBL, number of attending surgeons	C/T/L/S	A/P/comb	Y	Deformity	Deformity correction and fusion
Pull ter Gunne et al68 2010 (osteotomy)	Retro, Cohort	Multivariate logistic regression	III	363	55.8	Types of osteotomies	20		343		VCR, obesity	—	C/T/L	A/P/comb	Y	NS (excluded infection)	Fusion/osteotomy
Radcliff et al69 2013	Retro, Cohort	Student’s t test	III	7991	53.7	Focused on anesthesia ready time	276	58.4			Anesthesia ready time (>1 hour)	—	C/T/L	A/P/comb	Some	NS (excluded infection)	Decompression, fusion, tumor resection
Ramos et al70 2016	Retro, Cohort	Unadjusted and adjusted logistic regression analysis	IV	668	63.9	Also included arthroplasty patients; review only looking at spine cohort; Focused on S aureus colonization	10				—	S aureus colonization	C/T/L	NS	NS	NS	NS
Rao et al71 2011	Retro, CCS	Uni-/multivariate logistic regression	III				57	55 ± 15	181	57±15	BMI, gender (male), drain duration	Age, DM, CAD, HTN, COPD, active malignancy, smoking, revision, diagnosis, emergency surgery, timing of antibiotic prophylaxis, number of surgical teams (orthopedic-neurosurgery combined vs either alone), approach, graft type, EBL, intraoperative transfusion, intraoperative temperature, surgical duration	NS	P	NS	Degenerative, deformity, trauma, tumor	Fusion
Rechtine et al72 2001	Retro, Case series	Not listed	IV	117	NS	Thoracolumbar fracture	12				Complete neurologic injury	Incomplete neurologic injury	T/L	A/P	Y	Trauma	Decompression, stabilization
Rodgers et al73 2010	Retro, Cohort	Multivariate logistic regression, Student’s t test, chi-square	III	600	61.4	Focused on XLIF procedure					Open surgery (vs XLIF)	—	L	XLIF	Y	Degenerative	Fusion
Ruggieri et al74 2012	Retro, Case series	Kaplan-Meier survival analysis, log-rank test	IV	82	47	Primary sacral tumors					Procedure type (intralesional vs marginal vs wide resection), surgical duration	Age, level of resection (proximal vs distal), location of prior treatment (same institution vs other institution), tumor volume, neurological status (bowel-bladder continence)	S	A/P/comb	Some	Primary tumor	Tumor debulking or resection
Saeedinia et al75 2015	Retro, Cohort	Chi-square, ANOVA, multivariate regression	III	978	46		27		951		Muscle weakness, sphincter dysfunction, DM, HTN, smoking, bedridden, preoperative glucose, surgical region, instrumentation, allograft use, dural tear, incision length, number of levels operated, surgical time of day, surgical duration, LOS	Age, gender, BMI, myelopathy, IVDU, approach, revision	C/T/L	A/P	Some	Trauma, tumor, degenerative, disc disease, intradural (tumor, tethered cord)	NS
Salvetti et al76 2017	Retro, Case-control cohort	Chi-square, multivariate logistic regression	III				32		74		Prealbumin (low), DM	Age, gender, BMI, surgical duration, comorbidities	C/T/L	P	NS	NS (excluded trauma, infection, tumor)	NS (included fusion)
Satake et al77 2013	Retro, Cohort	Chi-square, Mann-Whitney U	III	110			11				DM, proteinurea	Age, BMI, ASA, smoking, creatinine, BUN, EBL, surgical duration	NS	NS	Y	NS	Instrumentation, not otherwise specified
Schimmel et al2 2010	Retro, Cohort	Uni-/multivariate logistic regression	III	1568			36		135		Prior surgery, number of levels operated, DM, smoking	Gender, age, height, weight, BMI, presence of any comorbidity, CAD, respiratory disease, RA, spinal region, surgical duration, bone graft type, approach, instrumentation	C/T/L	A/P/AP	Y	Degenerative, deformity	Fusion, deformity correction
Schoenfeld et al78 2013	Retro, Cohort	Uni-/multivariate logistic regression	III	5887	55.9	NSQIP database					BMI, resident involvement, ASA (>2), surgical duration	Age, DM, respiratory disease, CAD, HTN, PVD, renal disease, neurologic disease, infection, steroid use, preoperative albumin, spinal region, procedure type, diagnosis	C/T/L	A/P	Y	NS	Fusion
Schwarzkopf et al79 2010	Retro, CCS	Multiple logistic regression	III			Focus on blood transfusion	61	56	71	53	BMI, transfusion	Gender, smoking, EtOH, DM, HTN, steroid use	T/L	?	Some	NS	Discectomy, decompression, fusion
Sciubba et al80 2008	Retro, Cohort	Univariate, Fisher’s exact test	IV	46	46	Sacral tumors					Prior lumbosacral surgery, number of surgeons	Preoperative albumin, EBL, CSF leak, DM, instrumentation, laminectomies, obesity, plastic surgery closure, prior radiation, gender, smoking, age, bowel-bladder dysfunction, complex tissue reconstruction	S	A/P/comb	Some	Primary tumor	Tumor resection
Sebastian et al81 2016	Retro, Cohort	Student’s t test, chi-square/Fisher’s exact test, multivariate	III	5441	59 ± 13.6	NSQIP database	160	56.9 ± 12.2			BMI (>35 kg/m2), chronic opioid use, surgical duration (>197 min)	Type of posterior surgery, DM, smoking, resident involvement, paralysis	C	P	Some	NS	Decompression, fusion, laminoplasty
Shousha et al82 2014	Retro, Cohort	NS	IV	139	53.6	Transoral approach for upper cervical spine					Indication (rheumatologic or tumor cases higher risk)	Age, gender, presence of metal implant	C	Transoral	Some	Infection, trauma, congenital anomaly, rheumatologic, tumor	Odontoidectomy, fusion, stabilization, tumor resection
Singla et al83 2017	Retro, Cohort	Chi-square	III	88 540		Lumbar epidural steroid injection prior to surgery	1411		87 129		Lumbar epidural steroid injection (within 3 mo) prior to surgery	—	L	P	Y	Degenerative	Fusion
Skovrlj et al84 2015	Retro, Cohort	Chi-square	III	5117	51.8	Adult scoliosis, focused on surgeon experience					Less surgeon experience	—	T/L	NS	Y	Deformity	Deformity correction and fusion
Stambough et al85 1992	Retro, Case series	NS	IV				19	44			Malnutrition, trauma, UTI (all based on % of patients with these risk factors, no formal analysis)	No formal analysis	C/T/L	NS	Some	Trauma, degenerative, deformity, tumor, disc disease	Decompression, fusion, deformity correction
Sugita et al86 2016	Retro, Cohort	Mann-Whitney U, chi-square	III	279	63	Spinal metastases with intraoperative radiation	41	62	238	64	Katagiri/Tokuhashi’s prognostic score, postoperative Frankel score, preoperative radiation, and postoperative performance	Surgical duration, EBL	NS	P	Y	Spinal metastases	Decompression/fusion, radiation
Tempel et al87 2015	Retro, Case series	None	IV				83	56			Serum prealbumin below normal range (no formal analysis)	No formal analysis	C/T/L/S	NS	Some	Degenerative, trauma, tumor, deformity, hematoma, syringomyelia	Fusion, decompression, shunt
Tominaga et al88 2016	Retro, Cohort	Mann-Whitney U and Fisher’s, multiple logistic regression	III	825	59		14	57.5	811	59	Surgical duration, ASA (class 3), instrumentation, surgical region (thoracic in non-instrumented cases)	Two stage, revision, DM, smoking, BMI, anemia, preoperative UTI, number of levels, incision length, number of personnel or surgeons		A/P/comb	Y	Degenerative, infection, tumor, scoliosis	Decompression, fusion, deformity
Veeravagu et al89 2009	Retro, Cohort	Uni-/multivariate logistic regression	III	24 774	NS	Veterans Affairs’ NSQIP database	752				DM, ASA (>2), weight loss, dependent functional status, intraoperative transfusion, cancer, fusion/instrumentation, surgical duration (>3 hours)	Age, gender, race, emergency surgery, bleeding disorder, smoking, EtOH, WBC, creatinine	C/T/L	NS	Some	NS (excluded trauma)	Decompression, fusion, instrumentation
Watanabe et al90 2010	Retro, Cohort	Uni-/multivariate logistic regression	III	223	53	Focused on effect of intraoperative irrigation	14	49	209	53	DM, trauma	Surgical duration, EBL, instrumentation, gender, age, smoking, obesity	C/T/L	A/P/comb	Y	Trauma, tumor, degenerative, deformity	Decompression, fusion, deformity
Weinstein et al91 2000	Retro, Case series	None	IV				46	57.2			Type of surgery (based on overall rate of infection, not statistically challenged)	No formal analysis	C/L	A/P	Some	Degenerative, cervical myelopathy, nonunion, metastases, trauma, disc disease	Decompression, discectomy, fusion, instrumentation
Wimmer et al92 1998	Retro, Cohort	F test, paired Wilcoxon	III	850		Included some pediatric patients	22				Preoperative hospitalization (extended), surgical duration, EBL (>1 L), prior surgery, DM, smoking, EtOH, obesity, steroid use	NS	NS	A/P	Some	Deformity, trauma, degenerative	Fusion, instrumentation, not otherwise specified
Woods et al93 2013	Retro, CCS	Conditional logistic regression	III			Focused on perioperative transfusions	56	61 ± 12	91	60 ± 14.8	Perioperative transfusion	—	L	A/P	Some	NS	Decompression, fusion
Yang et al94 2016	Retro, Cohort	Pearson chi-square	III	18 931		Patients >65, lumbar epidural steroid injection prior to surgery	196				Lumbar epidural steroid injection (within 3 months) prior to OR	—	L	P	N	Degenerative	Decompression

Abbreviations: ACDF, anterior cervical discectomy and fusion; ASA, American Society of Anesthesiologists class; BMI, body mass index; CAD, coronary artery disease; CCS, case-controlled study; CHF, congestive heart failure; COPD, chronic obstructive pulmonary disease; CSF, cerebrospinal fluid; CVA, cerebrovascular accident; DM, diabetes mellitus; DVT, deep vein thrombosis; EBL, estimated blood loss; EtOH, alcohol use; GCS, Glasgow Coma Scale; HTN, hypertension; IA, inflammatory arthropathy; IVDU, intravenous drug use; LOS, length of stay; MI, myocardial infarction; MIS, minimally invasive surgery; MUST, Malnutrition Universal Screening Tool score; NNIS, National Nosocomial Infection Surveillance index; NS, not specified; NSAID, nonsteroidal anti-inflammatory drug; NSQIP, National Surgical Quality Improvement Program; OSA, obstructive sleep apnea; PE, pulmonary embolus; Pro, prospective; PVD, peripheral vascular disease; RA, rheumatoid arthritis; Retro, retrospective; SCI, spinal cord injury; SII, surgical invasiveness index; UTI, urinary tract infection; XLIF, extreme lateral interbody fusion. C, cervical; T, thoracic; L, lumbar; A, anterior; P, posterior; Comb, A/P combined.