Risk of Complications in Spine Surgery: A Prospective Study

Abstract

Complications are the chief concern of patients and physicians when considering spine surgery. The authors seek to assess the incidence of complications in patients undergoing spine surgery and identify risk factors for their occurrence.
Prospective study of patients undergoing spine surgery from 1 February 2013 to 1 February 2014. Epidemiological characteristics and complications during the surgical hospitalization were recorded and analyzed.
The sample comprised 95 patients (mean age, 59 years). Overall, 23% of patients were obese (BMI =30). The mean BMI was 25.9. Approximately 53% of patients had comorbidities. Complications occurred in 23% of cases; surgical site infections were the most common (9%). There were no significant differences between patients who did and did not develop complications in terms of age (60.6 vs 59.9 years, p = 0.71), sex (56% female vs 54% female, p = 0.59), BMI (26.6 vs 27.2, p = 0.40), or presence of comorbidities (52% vs 52.8%, p = 0.87). The risk of complications was higher among patients submitted to spine instrumentation than those submitted to non-instrumented surgery (33% vs 22%), p=0.8.
Just over one-quarter of patients in the sample developed complications. In this study, age, BMI, comorbidities were not associated with increased risk of complications after spine surgery. The use of instrumentation increased the absolute risk of complications.

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20 The Open Orthopaedics Journal, 2015, 9, 20-25
1874-3250/15 2015 Bentham Open
Open Access
Risk of Complications in Spine Surgery: A Prospective Study
Rodolfo Casimiro Reis*, Matheus Fernandes de Oliveira, José Marcus Rotta and
Ricardo Vieira Botelho
Spine Surgery Section, Hospital do Servidor Puúblico Estadual de São Paulo, São Paulo-SP, Brazil
Abstract: Purpose: Complications are the chief concern of patients and physicians when considering spine surgery. The
authors seek to assess the incidence of complications in patients undergoing spine surgery and identify risk factors for
their occurrence.
Methods: Prospective study of patients undergoing spine surgery from 1 February 2013 to 1 February 2014.
Epidemiological characteristics and complications during the surgical hospitalization were recorded and analyzed.
Results: The sample comprised 95 patients (mean age, 59 years). Overall, 23% of patients were obese (BMI ≥30). The
mean BMI was 25.9. Approximately 53% of patients had comorbidities. Complications occurred in 23% of cases; surgical
site infections were the most common (9%). There were no significant differences between patients who did and did not
develop complications in terms of age (60.6 vs 59.9 years, p = 0.71), sex (56% female vs 54% female, p = 0.59), BMI
(26.6 vs 27.2, p = 0.40), or presence of comorbidities (52% vs 52.8%, p = 0.87). The risk of complications was higher
among patients submitted to spine instrumentation than those submitted to non-instrumented surgery (33% vs 22%),
p=0.8.
Conclusion: Just over one-quarter of patients in the sample developed complications. In this study, age, BMI,
comorbidities were not associated with increased risk of complications after spine surgery. The use of instrumentation
increased the absolute risk of complications.
Keywords: Complication, outcome, risk, spine surgery.
INTRODUCTION
Complications are the main concern of patients and
physicians at the time of spine surgery indication, and when
they occur, may have personal and economic consequences,
affecting the quality of life and future independence of
patients [1]. Studies have shown that surgeons and
gynecologists have a lower life expectancy than clinicians,
and emotional stress may be a cause of this difference [2].
Surgical complications are a relevant cause of stress in
surgeons.
Reducing the incidence of these complications is a
constant concern of physicians and health managers.
Reimbursement practices incorporating pay-for-performance
measures seek to link patient outcomes to practitioner
reimbursement. These financial incentives are part of a
policy that aims to reduce hospital-acquired conditions and,
therefore, hospitalization costs [3, 4].
The incidence and prevalence of complications in spine
surgery have varied widely in literature, due to differences in
methodology and patient samples among studies. Few
prospective studies have assessed complications [3-5].
Furthermore, there is no consensus on potential risk factors
for the development of complications in spine surgery [3-9].
*Address correspondence to this author at the Spine Surgery Section,
Hospital do Servidor Puúblico Estadual de São Paulo, Avenida Pedro de
Toledo 1800; 04039-004; São Paulo SP, Brazil; Tel: +55-11-986897473;
E-mail: rodolfocr84@yahoo.com.br
A clear definition of risk of complications in spinal
surgeries, in the setting of different demographics and
comorbidities, is required for adequate therapeutic decision
making, once it can help patients to decide weather submit to
an invasive procedure with provided numeric information.
Therefore, this study sought to assess the incidence of
complications in spine surgery and identify patient-related
risk factors and those related to the use of instrumentation.
METHODS
This study used a prospective observational design
whereby all patients undergoing spine surgery at a tertiary
referral center between 1 February 2013 and 1 February
2014 were observed from surgery to discharge and in
hospital complications were recorded. Hospital do Servidor
Público Estadual de São Paulo, SP, Brazil, covers about 3
million state servers and their relatives throughout São Paulo
state. The Neurosurgery Department provides a 25-bed unit
and offers residency program. Surgeries were indicated in
the Spine clinic (elective cases) and in the emergency
department of the hospital and included a wide range of
procedures (ICD-9CM:01.2, 03.09, 03.32, 03.71, 80.51,
81.00-81.08, 81.30, 81.65, 81.66, 84.51, 84.60, 84.61, 84.62,
84.80, 84.84). No inclusion or exclusion criteria were
applied; all patients undergoing any spine surgery procedure
during the study period were eligible for admission. All
patients received cefuroxime IV 60 minutes before incision
and q 8h post-op, 6 doses total. Regarding deep-vein
thrombosis prophylaxis, graduated compression stockings

Risk of Complications in Spine Surgery The Open Orthopaedics Journal, 2015, Volume 9 21
were used for all patients, and low molecular weight heparin
was prescribed from day 3 post-op for those who could not
walk.
For the purposes of this study, a complication in spinal
surgery was defined as “any untoward event occurring to a
patient while on the neurosurgical service” [10].
Complications were classified as general, specific, or
technical (Table 1), as described by Fritzell, Hagg, and
Nordwall [11], and further divided into two categories:
major (adverse events with sequelae in discharge or
requiring revision surgery during hospitalization) and minor
complications (adverse events with no sequelae in discharge
and not requiring revision surgery), a modified classification
from Lebude B et al. [12].
Table 1. Classification of complications in spine surgery.
General
Specific
Technical
Mortality
Hematoma
Screw placement
Thrombosis
Infection superficial
Instrument-related
Hepatitis
Infection deep
Dislocation of transplant
Gastrointestinal
Nerve root injury/pain
Urinary tract infection
Dural tear
Pulmonary complication
Caudaequine syndrome
Skin problem
Injury to sympathetics
Psychological problems
Sex-related problems
Coping problems
Retrograde ejaculation
Donor site pain
Miscellaneous
Fritzell P, Hagg O, Nordwall A. Complications in lumbar fusion surgery for chronic
low back pain: comparison of three surgical techniques used in a prospective
randomized study. A report from the Swedish Lumbar Spine Study Group. Eur Spine J
2003; 12: 178-189.
The anthropometric variables of interest were age,
gender, and body mass index (BMI), which was stratified in
accordance with WHO guidelines as follows: BMI <18.5,
underweight; 18.5–24.9, normal range; 25.0–29.9, over-
weight; ≥30, obesity [13].
During admission, patients were asked to fill up a
questionnaire with possible comorbidities and ongoing
medications. If any patient had two measures higher than
140x90mmHg (blood pressure) or 126mg/dl (fasting blood
glucose) during hospitalization, he was considered
hypertensive or diabetic, respectively, despite no previous
diagnosis.
Primary spinal diseases were classified etiologically as
degenerative, traumatic, neoplastic, congenital, infectious, or
inflammatory. The operated spinal segment was classified as
cervical, thoracic, or lumbar.
The following variables were tested for correlation with
complications: age, gender, BMI, comorbidities, and
instrumentation.
This study was approved by the institutional Research
Ethics Committee with protocol number 405320.
Statistical Analysis
Numerical variables were expressed by descriptive
statistics (mean, standard deviation, range, and relative
frequency). Student’s t-test was used to compare differences
in age distribution between affected and unaffected patients,
whereas the chi-square method was used to test for
association between the presence of complications and age,
gender, BMI, comorbidities, and instrumentation. The
frequency of complications in relation to the variables
comorbidities and instrumentation was assessed as a
percentage (risk). Absolute risk difference and number
needed to avoid complication related to instrumentation was
calculated.
The significance level was set at p<0.05. All analyses
were carried out in the SPSS for Windows 13.0 software
environment.
RESULTS
Demographic and Surgical Data
Demographic data are shown in Table 2. Ninety-five
patients underwent spine surgery during the study period and
all patients were followed until hospital discharge. The mean
age was 59 ±12.31years, and 46% of patients were >60 years
old. Forty-three patients (45%) were male. The mean BMI
was 25.9;overall, 41 patients were overweight (43.1%) and
22were obese (23.1%).
Table 2. Summary of demographic data.
Variable
N (%)
No. of patients
95
Age (years)
Mean±SD
Range
59 ±12
31–88
Sex
Male
Female
43 (45)
52 (55)
BMI
<18.5
18.5-24.9
25-29.9
≥30
1 (1)
31 (33)
41 (43)
22 (23)
Fifty patients (52.6%) had comorbidities. The most
common comorbid conditions were hypertension, present in
36 patients, and diabetes mellitus, present in 7 (Table 3).
The most common etiology of spinal disease was
degenerative(n=64), followed by neoplastic (n=19) and
trauma (n=11) (Fig. 1). Regarding the affected spinal
segment, 29.4% of procedures were performed on the
cervical spine, 24.3% on the thoracic spine, and 46.3% on
the lumbar spine.
Thirty-six patients (38%) received instrumentation,
whereas 59 (62%) did not.

22 The Open Orthopaedics Journal, 2015, Volume 9 Reis et al.
Table 3. Summary of comorbidities.
Comorbidity
N
Hypertension
36
Diabetes mellitus
7
Depression
4
Osteoporosis
3
Smoking
3
Gout
2
Alcoholism
2
Cancer
2
Stroke
1
Congestive heart failure
1
Benign prostatic hypertrophy
1
Complications
Overall, 25 patients (26%) had 34 complications. Risk of
complication after a cervical procedure was 25% (7 patients
of 28), 17% in thoracic and 32% in lumbar procedures.
Eleven patients (11.6%of the sample) had major
complications, and 14 patients had minor complications (risk
= 15%) (Fig. 2).
Of the 34 complications recorded, 11 (32%) were
general, 18 (53%) were specific, and five (15%) were
technical, as shown in Fig. (3). There were no neurological
complications.
Seven patients (7.3%) underwent revision surgery: five
due to infection, one due to CSF leak, and one due to screw
displacement. Three patients (3.1%) died, all of septic shock
(two secondary to surgical site infection and one due to
underlying spondylodiscitis).
Fig. (1). Etiology of spine diseases.
Fig. (2). Frequency and classification of complications.
2% 2%
7%
12%
20% 67%
Degenerative
Neoplasm
Trauma
Infection
Inflammation
Congenital
None
Minor
Major
74%
15%
11%

Risk of Complications in Spine Surgery The Open Orthopaedics Journal, 2015, Volume 9 23
Association Between Anthropometric Variables and
Complications
There were no significant differences in age (60.6 vs 59.9
years, p= 0.71), sex (56%female vs 54%female, p = 0.59), or
mean BMI (26.6 vs 27.2, p=0.40) between patients who
developed complications and those who did not, respectively
(Table 4).
Table 4. Comparison of demographic data between patients
with and without complications.
Data
Complications
P Value
Present
Absent
Age (years)
59.94
60.64
0.71
Female gender
54.2%
56%
0.59
BMI
27.28
26.62
0.40
Association Between Comorbidities and Complications
Of the 25 patients who developed complications, 52%
had comorbidities; of the 70 patients who did not develop
complications, 52.8% had comorbidities (p = 0.87).
The risk of complications was 24% among patients with
comorbidities (12 of 50) and 26.6% in patients without
comorbidities (12 of 45) (p= 0.31).
The risk of complications between hypertensive and non-
hypertensive patients was the same (40%), p= 1.
Association Between Instrumentation and Complications
The risk of complications among patients who received
instrumentation was 33%(12 of 36), versus 22% (13 of 59)
among those who did not receive instrumentation
(X2;p=0.87). The absolute difference of risk was 11%. At
each 9 patients treated without instrumentation, 1 related
complication could be avoided.
Multivariate Analysis
Since all associations between variables (age, sex, BMI,
comorbidities and instrumentation) and complications did
not reach statistical significance, multivariate analysis could
not be concluded.
DISCUSSION
The postoperative complications of spine surgery have
recently been an object of study due to growing concerns
with reduction of hospital costs and improvement of
healthcare services [3]. From a humanitarian standpoint,
complications are also a major issue, due to their potential to
cause suffering and stress to patients themselves, to their
families, and to their surgeons. Stress has been implicated as
a cause of decreased survival among surgeons as compared
with clinicians [2].
The sample of the present study was similar to those of
previous investigations: demographic characteristics, the
percentage of overweight patients, the higher proportion of
lumbar spine surgeries, and the percentage of patients who
*"Septic"shock"originally"from"preexisting"spondylodiscitis"
Fig. (3). Summary of complications.
Complications
General (11)
Specific (18)
Technical (5)
9
211
31111111113
Wound infection
CSF fistula
Wound dehiscence
Wound serosanguineous
Pneumonia
Heart arrhytmia
Myocardial infarction
Dysautonomia
Syncope
Lung congestion
Pulmonary thromboembolism
Hypertensive Crisis
Septic shock*
Instrument loosening
Urethral bleeding
Burn
6

24 The Open Orthopaedics Journal, 2015, Volume 9 Reis et al.
underwent instrumentation were similar to those of previous
studies on complications in spine surgery [3, 5-7, 14].
The rate of postoperative complications in spine surgery
varies widely in the literature. Campbell et al. recently
reported an incidence of 52%, with a predominance of minor
complications (approximately twice as frequent as major
complications), as seen in the present sample [3]. A
systematic review of the literature revealed that retrospective
studies report a lower incidence of complications than
prospective studies (16% vs 19.9%) [5]. The present study,
which used a prospective design, found an incidence of 26%,
with a predominance of specific complications (53%), which
is also consistent with previous studies [3].
Advanced age and obesity have been associated with
complications, but many of the studies that found this
association reported inconsistent and divergent results, and
most were retrospective [6, 9, 15-19]. Lee et al.
demonstrated an increased incidence of complications
among patients aged >65 years on multivariate analysis of a
prospective database of spine surgery cases [9]. Regarding
obesity, a few retrospective studies have found it to be
associated with an increased complication rate in spine
surgery, but most prospective studies – and one nationwide
database study – failed to demonstrate such association [6,
20, 21]. In the present study, advanced age and obesity were
not associated with an increased complication rate.
Overall, 52% of patients in the present sample had
presented comorbidities, with a predominance of
cardiovascular diseases. The presence of comorbidities did
not affect the incidence of complications in this sample.
The correlation between comorbidities and complications
in spine surgery is poorly defined in the literature. Most
studies are retrospective or based on population data. Li
et al. and Deyo et al. reported an association between
presence of comorbidities and increased complication rate
[7, 22]. Only one prospective study has assessed the impact
of comorbidities on complications, finding that an increase
in the number of comorbidities was correlated with an
increase in the incidence of complications [3]. The present
study – which, as noted above, was prospective in nature –
did not find any association between comorbidities and
complications. We did not use any specific comorbidity
score in the analyses, due to the disproportional
predominance of cardiovascular diseases seen in our sample.
In the present sample, the rate of complications was
higher in patients who underwent instrumentation than in
patients who were not instrumented (33% vs 22%
respectively), but the difference did not reach statistical
significance (p=0.8). In the other hand, evaluating the
absolute risk differenceof complication, instrumentation
increased it by 11%. Thus at each 9 patients treated with
instrumentation, one will develop a complication. Several
studies have demonstrated an association between
instrumentation and complications [3, 14, 22].
Although multivariate analysis would be important to
identify independent risk factors for complications, it could
not be concluded, since association between variables and
complications did not reach statistical significance.
Nasser et al. published a systematic review of 105 studies
on complications in spine surgery, most of which were
retrospective [5]. The majority of studies that evaluated
associations between complications and variables studied
only one potential risk factor, such as age, obesity,
comorbidities, or instrumentation. Conversely, our
prospective study evaluated all of these potential
associations. We did not evaluate complications in specific
surgical procedures because this would demand a greater
number of patients.
Some factors may explain the divergence between the
present study and previous investigations regarding the
association between comorbidities, instrumentation and
complications. These elements act as limitations of our study
and should be addressed. Since a consistent definition of
operative complications lacks in literature, we used a wide-
ranging concept of complications herein; our sample was
originated from a high-complexity tertiary referral center,
which for sure does not represent general population
submitted to spine surgery; we presented a small sample
size; we included a broad range of etiologies of spinal
diseases (whereas the literature has largely focused on
degenerative diseases) and a wide range of comorbidities in
this study, such as lifestyle habits (smoking and alcoholism).
As previous mentioned, the study was conducted in a
hospital with residency program; since operator experience
may be a risk factor for complication, residents assistance
may have increased our incidence of complications. Until
large, multicenter studies are conducted, clustered data from
multiple prospective investigations may reveal the true
incidence of complications in spine surgery.
CONCLUSION
Just over one-quarter of patients in the sample developed
complications. Most of these were specific and minor, but
11% of patients experienced major complications, which
caused prolonged hospital stay and increased suffering. The
sample-wide risk of death was 3%.
In the present study, age, BMI and comorbidities were
not associated with an increased risk of complications.
However, the use of instrumentation increases the absolute
risk of complications in 11%.
CONFLICT OF INTEREST
The authors confirm that this article content has no
conflict of interest.
ACKNOWLEDGEMENTS
Declared none.
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Received: August 23, 2014 Revised: December 4, 2014 Accepted: December 11, 2014
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