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Classification of perioperative complications in spine surgery
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Classification of Perioperative Complications in Spine Surgery M. Farshad MD, MPH , A. Aichmair MD, MPH , C. Gerber MD , D.E. Bauer MD PII: DOI: Reference:
S1529-9430(19)31151-9 https://doi.org/10.1016/j.spinee.2019.12.013 SPINEE 58084
To appear in:
The Spine Journal
Received date: Revised date: Accepted date:
17 September 2019 17 December 2019 17 December 2019
Please cite this article as: M. Farshad MD, MPH , A. Aichmair MD, MPH , C. Gerber MD , D.E. Bauer MD , Classification of Perioperative Complications in Spine Surgery, The Spine Journal (2019), doi: https://doi.org/10.1016/j.spinee.2019.12.013
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier Inc.
1
Classification of Perioperative Complications in Spine Surgery
2
Farshad M. MD MPH1*, Aichmair A. MD MPH1, Gerber C. MD1, Bauer D.E. MD1
3 4
1
Department of Orthopaedics, Balgrist University Hospital, University of Zurich, Forchstrasse
5
340, 8008 Zurich, Switzerland
6 7
*Corresponding author:
8
Prof. Mazda Farshad MD MPH
9
Email: [email protected]
10
Phone: +41 44 386 3004
11 12 13
The authors have no financial interest to disclose
14
Abstract
15
Background Context: Perioperative complications affect surgical outcomes. Classification
16
systems of perioperative complications are well established and widely applied in many
17
surgical fields other than spine surgery.
18
Purpose: The aim of this study was to construct and validate a comprehensive classification
19
system for perioperative complications in spine surgery.
20
Study Design: Retrospective case series
21
Methods: A comprehensive classification system was constructed to stratify complications in
22
spinal surgery and consequently applied to 934 patients who consecutively underwent spine
23
surgery in a university hospital setting. A complication was defined as any kind of deviation
24
from the normal perioperative course, ranging from a postoperative anemia to death. The
25
comprehensive classifications system stratifies complications according to (1) complexity of 1
26
index procedure (2) immediate cause of complication (surgical vs medical) (3) the required
27
treatment and (4) potentially associated long-term functional deficits resulting from neural
28
injury. Subsequently, the proposed classification system was validated by applying the
29
duration of cumulative hospital stay as the primary outcome.
30
Results: Perioperative complications were recorded in 135 (14.3%) out of 934 cases. There
31
was a significant difference in the hospital stay between complications stratified according
32
to therapeutic consequences, grade A: 5.6±1.6 (range: 3-8) days, grade B: 7.9±3.8 (range: 3-
33
21) days, grade C: 13.1±8.1 (range: 4-59) days and grade D: 55.2±56.6 (range: 14-198) days,
34
respectively (p = <0.001). Also, there was a significant difference in hospital stay between
35
groups of increasing point difference of neurologic deficit, 0 vs. -1 and -1 vs. -2, respectively.
36
Conclusion: A comprehensive classification system for perioperative complications in spine
37
surgery (considering 4 categories) is presented and validated. The categories therapeutic
38
consequence (A to E) and decrease in neurological function correlate strongly with hospital
39
stay.
40
Key words: Spine surgery, Complications, Classification, Hospital stay, Complexity, Risk
41
factor;
2
42
Introduction
43
An objective and comparable quantification of complications in medical practice is
44
paramount to assess treatment quality and effectiveness.[1] Classification systems
45
stratifying the severity of complications are widely used in other medical fields such as
46
general surgery.[1-4] However, a similar comprehensive classification system focusing on
47
complications in spine surgery is not available yet.[5] Apart from its medical and economic
48
implications, a uniform definition and quantification of complications is necessary to
49
perform valid comparisons between clinical studies, quality of clinical care and performance
50
of surgical teams. Such a system is required to incorporate varying patient cohort
51
characteristics of the hospitals and the complexity of the procedures. It has been suggested
52
that the complexity of the surgical procedure plays a major role in risk estimation for
53
complications and that it is more predictive for assessment of health-care costs compared to
54
postoperative complications.[6] Recently, this study group proposed a classification system
55
to categorize the complexity of surgical procedures specifically for spine surgery.[7]
56
Complementing the established grading for complexity of surgical procedures we propose a
57
system to classify complications in spine surgery incorporating the previously established
58
findings. Therefore, the aim of this study was to construct and validate a comprehensive
59
classification system for complications in spine surgery, respecting the complexity of the
60
surgical procedure, the type of complications (medical vs surgical) and their therapeutic
61
consequences, as well as potential neurological decline.
62
3
63
Materials & Methods
64
After approval of the state ethical committee, patients who consecutively underwent spine
65
surgery between 05/2014 and 12/2015 at a single Swiss university clinic were included in the
66
present study if the following criteria were met: available data set, age at surgery > 18 years,
67
and informed consent. As previously proposed, any deviation from a regular postoperative
68
course not including sequela or failure to cure was defined as complication and therefore
69
included for final analysis.[1]
70
Data were collected on age, gender, body mass index (BMI), medication, smoking status,
71
preoperative American Society of Anesthesiologists (ASA) classification, laboratory values as
72
well as surgical details such as clinical/radiographic surgical indication, blood loss, duration
73
of surgery, revision surgery, and type of surgery. Furthermore, postoperative length of
74
intermediate care unit (IMC) and hospital stay were documented. In cases where patients
75
were readmitted for the treatment of a postoperative complication, the days of hospital stay
76
of subsequent readmissions were added up and consequently termed “cumulative hospital
77
stay”. The cumulative hospital stay was chosen as the most relevant surrogate for
78
perioperative outcome.[1] Therefore, validation of the proposed classification system was
79
performed by correlating increasing grades of complications to this parameter.[1] Also, the
80
complexity[7] of surgical intervention and the occurrence and sequelae of intra- and
81
perioperative complications were documented. This database has been used in another
82
study analyzing predictive risk factors for perioperative complications and morbidities in
83
spine surgery.[7] A subset of these variables was ultimately used in this study.
84 85 86
4
87
Stratification of Complication Severity
88
Complications were defined as any kind of deviation from a standard perioperative course
89
ranging from a symptomatic anemia to death.
90
A consensus statement was reached to comprehensively classify the severity of
91
complications based on: (1) the previously proposed complexity of the performed surgical
92
procedure[7] (table 2) (2) whether the complication was directly or indirectly related to the
93
surgical procedure, consequently termed “surgical” (s) or “medical” (m) (3) the treatment
94
required to manage the complication (graded from A-E) similar to the modified approached
95
described by Sink et al.[8] and the grading of complications according to Common
96
Terminology Criteria for Adverse Events (CTCAE)[9] (4) and associated long-term functional
97
deficits resulting from nerve injury in accordance with the American Spinal Injury Association
98
(ASIA) Score[10]. Intraoperative injuries resulting in myelopathy were graded as ASIA E to A,
99
injuries resulting in radiculopathy as either “no loss of motor function” (sensory deficits only)
100
or “motor useful” (key muscle strength > M3) and “motor useless” (key muscle strength <
101
M3).[10] To account for preoperatively existing neurologic deficits, only the point-difference
102
between pre- and postoperative deficits was incorporated into the final score (table 1).
103
(e.g. a lesion of the spinal cord during an anterior cervical discectomy and fusion causing
104
paraplegia with remaining sensory function would be classified as: IISC -3)
105
5
106
Statistical Analysis
107
Continuous variables are reported as mean ± standard deviation (SD), whereas categorical
108
variables are reported as frequencies and proportions. The Kolmogorov Smirnov test was
109
used to test for normal distribution of data. The Mann-Whitney U test was used for the
110
comparison of continuous variables for non-normal distributed data. The Pearson’s chi
111
squared test was used for the comparison of proportions between groups. Comparison of
112
continuous variables between the different groups of surgical complications was performed
113
via analysis of variance (ANOVA). The Bonferroni method of multiple comparisons was used
114
for post-hoc analysis. Statistical analysis was performed using IBM SPSS Statistics, Version
115
24.0 (IBM Corp., Armonk, NY).
6
116
Results
117
A total number of 1067 of patients consecutively underwent spine surgery at a single center,
118
out of whom 934 (female: 448, male: 486) met the defined criteria to be included in the
119
present study (87.5%). One hundred and thirty-five deviations from unremarkable
120
perioperative course (defined here as complications) (14.30%) were recorded (female: 59,
121
male: 76) and were included for final analysis. The average age at surgery in the group of
122
patients sustaining a postoperative complication was 61.45±16.21 (range: 23-87) years, and
123
the average BMI 27.91±5.59 (range: 15.62-55.78) kg/m2. An active smoking status was
124
recorded in 53 (37.30%). Preoperative assessment revealed an ASA class I in 14.8% (n=20),
125
class II in 46.7% (n=63), class III in 34.8% (n=47), and class IV in 3.7% (n=5). None of the
126
patients was classified as ASA class V or VI. Further surgical details describing the index
127
procedure are illustrated in table 3.
128 129
Complexity of Intervention
130
The 3 grades of complexity of spinal surgical procedures have previously been described in
131
detail.[7] (table 2) Surgical interventions with complexity grade I (e.g. midline
132
decompression, etc) were recorded in 58.5% (n=79), complexity grade II (e.g. anterior
133
cervical discectomy and fusion, etc) in 37.0% (n=50) and complexity grade III (e.g. anterior
134
scoliosis correction, etc) 4.4% (n=6) of cases with a complication, respectively. Higher grades
135
of complications were not significantly associated with increasing complexity of the
136
intervention. (table 5)
137 138
Stratification of Complication Severity
7
139
Stratification of complications was performed according to the above-mentioned consensus
140
statement. Complications regarded as directly related to the index procedure (surgical) were
141
recorded in 72.6% (n=98) and regarded as indirectly related to the index procedure (medical)
142
in 27.4% (n=37). (table 4) Three cases sustained both, a medical and a surgical complication.
143
In those three cases the therapeutic consequence, and hence complication grade of the
144
surgical complication was regarded higher than the medical complication. For further
145
analysis these cases were treated as surgical complications. The most frequent surgical
146
complications were recurrent disc herniation (30.19% of all surgical complications) and
147
superficial wound complications (12.26% of all surgical complications). The most common
148
medical complications were postoperative symptomatic anemia (40% of all medical
149
complications) and postoperative electrolyte disturbances (31.43% of all medical
150
complications). Further details on surgical and medical complications are illustrated in
151
figures 1 and 2, respectively.
152
Considering therapeutic consequence, 9.6% (n=13) of complications were stratified as grade
153
A (mild), 39.3% (n=53) as grade B (moderate), 43.7% (n=59) as grade C (severe) and 7.4%
154
(n=10) as grade D (life threatening), respectively. Death (grade E) was recorded in none of
155
the cases. In terms of permanent neurologic deficit, a point difference of 0 was noted in
156
89.6% (n=121), a point difference of 1 in 7.4% (n=10) and a point difference of 2 in 3.0%
157
(n=4). A point difference of greater than 2 was recorded in none of the cases.
158 159
Validation of the classification system
160
The mean length of cumulative hospital stay for patients sustaining a postoperative
161
complication was 13.5±19.9 (range: 3-198) days.
8
162
There was no significant difference in the length of hospital stay between cases sustaining
163
medical or surgical complications with 10.1±4.2 (range: 4-17) vs. 14.8±23.2 (range: 3-198)
164
days, respectively (p 0.224).
165
There was a significant difference in the length of hospital stay between complications
166
stratified according to therapeutic consequences, grade A: 5.6±1.6 (range: 3-8) days, grade
167
B: 7.9±3.8 (range: 3-21) days, grade C: 13.1±8.1 (range: 4-59) days and grade D: 55.2±56.6
168
(range: 14-198) days, respectively (p = <0.001). A post hoc analysis revealed a significant
169
difference for complications graded A vs. D, B vs. D and C vs. D, (p = < 0.001). There was no
170
significant difference in length of hospital stay between groups A vs. B (p = 1.00), A vs. C (p =
171
0.779) and B vs. C (p = 0.553).
172
There was a significant difference in the length of hospital stay between groups of increasing
173
point difference of neurologic deficit, 0 vs. -1 and -1 vs. -2, respectively. A summary of the
174
difference in length of hospital stay between increasing grades of complication is illustrated
175
in table 5.
9
176
Discussion
177
The aim of this study was to construct and validate a comprehensive classification system for
178
complications in spine surgery, respecting the complexity of the surgical procedure, the type
179
of complications (medical vs surgical) and their therapeutic consequences, as well as
180
permanent neurological deficits. Others (Clavien PA and Dindo D)1 pioneered in the field of
181
grading and defining complications for surgical procedures in general/visceral surgery by
182
proposing a therapy-oriented classification system in 1992 and its subsequent modification
183
in 2004.[1, 11] However, as opposed to this now widely applied classification system
184
specifically developed for complications in general surgery and its subsequent adaptation for
185
orthopedic surgery[8], no comparable instrument has been made available respecting the
186
peculiarity of spine surgery where localized injury to nervous tissue of lesser extent may lead
187
to distant loss of function of far greater implication. Also, as a result of the paucity of
188
treatment options, complications including postoperative paraplegia might not be followed
189
by further surgical intervention. Furthermore, we believe that a comprehensive classification
190
system for complications should incorporate the complexity of the surgical procedure. The
191
validity of stratifying surgical interventions into three grades of increasing complexity (table
192
2) was previously demonstrated by this study group as a first step to lay the basis for a
193
comprehensive classification system. In detail, it was shown that the risk for an IMC stay
194
longer than 24h is increased for procedures of complexity grades II and III compared to
195
complexity grade I by 3.5-fold and 5.4-fold, respectively.[7] A subgroup analysis of the same
196
database confirming these findings was performed in this study including patients sustaining
197
a perioperative complication only.
198
It is the authors' experience that surgeons might frequently not fully consider adverse events
199
not directly related to the surgical treatment as complication. However, based on the
10
200
definition proposed by Clavien and Dindo, a complications is “any negative outcome not
201
including failure to treat or sequalae.”[1] Standardized definitions for the most frequent
202
complications not directly related to a surgical treatment have been defined by CTCAE.[9]
203
These were incorporated into the proposed classification system and subsequently termed
204
“medical” and amongst other include urinary tract infection, symptomatic postoperative
205
anemia or electrolyte disturbances. (figure 2)
206
For the third modifier of the classification system, we used the already established and
207
reproducible outcome parameters for stratification of complications into grades A to E
208
depending on the required treatment of the complication according to the Common
209
Terminology Criteria for Adverse Events (CTCAE).[9] The CTCAE is a well-established and
210
validated classification that allows the grading of adverse events throughout multiple organ
211
systems and corresponds widely with the more specific classification system described by
212
Clavien and Dindo[1].
213
therapeutic intervention graded highest as “D”, therefore confirming this notion with some
214
limitations.
215
A similar approach was pursued to grade persistent neurologic impairment as a result of
216
intraoperative complications. For loss of function after injury to neuronal tissue the
217
American Spinal Injury Association (ASIA) score for injury of the spinal cord, and muscle
218
strength (strength > grade M3: “motor useful” or strength < grade M3: “motor useless”) as
219
defined by the ASIA for nerve root injury alone were utilized.[10]
220
As a result of the small sample size, the available data did not permit for validation of
221
stratification of complications according to permanent neurologic deficit utilizing the length
222
of hospital stay. However, due to the implications of spinal cord injury or nerve root it seems
In this study, patients sustaining a complication requiring a
11
223
rational to include a modifier reflecting these complications into a classifications system in
224
spine surgery.
225
This study has limitations that need to be considered and addressed in further steps of
226
validation of the classification system. A retrospective data analysis was performed, with the
227
potential for introducing bias including underreporting of complications. Further, although
228
utilized in other studies [12], the duration of hospital stay remains only a surrogate
229
parameter for validation of this classification systems. As a result of its complexity, the
230
proposed classification system has limited applicability for daily clinical practice.
231
However, despite its limitations, the authors are confident to have constructed a valuable
232
classification tool for grading of perioperative complications, specifically designed for spine
233
surgery incorporating the complexity of the surgical intervention (table 1 and 2). This should
234
help for better quality control processes by facilitating valid comparisons of outcomes in
235
spine surgery between cases and institutions.
236
12
237
References
238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273
1. Clavien PA, Barkun J, de Oliveira ML, et al. The Clavien-Dindo classification of surgical complications: five-year experience. Ann Surg. 2009;250(2):187-96. 2. DeOliveira ML, Winter JM, Schafer M, et al. Assessment of complications after pancreatic surgery: A novel grading system applied to 633 patients undergoing pancreaticoduodenectomy. Ann Surg. 2006;244(6):931-7; discussion 7-9. 3. Chun YS, Vauthey JN, Ribero D, et al. Systemic chemotherapy and two-stage hepatectomy for extensive bilateral colorectal liver metastases: perioperative safety and survival. J Gastrointest Surg. 2007;11(11):1498-504; discussion 504-5. 4. de Santibanes E, Ardiles V, Gadano A, Palavecino M, Pekolj J, Ciardullo M. Liver transplantation: the last measure in the treatment of bile duct injuries. World J Surg. 2008;32(8):1714-21. 5. Goldhahn S, Sawaguchi T, Audige L, et al. Complication reporting in orthopaedic trials. A systematic review of randomized controlled trials. J Bone Joint Surg Am. 2009;91(8):1847-53. 6. Aust JB, Henderson W, Khuri S, Page CP. The impact of operative complexity on patient risk factors. Ann Surg. 2005;241(6):1024-7; discussion 7-8. 7. Farshad M, Bauer DE, Wechsler C, Gerber C, Aichmair A. Risk factors for perioperative morbidity in spine surgeries of different complexities: a multivariate analysis of 1,009 consecutive patients. Spine J. 2018. 8. Sink EL, Leunig M, Zaltz I, Gilbert JC, Clohisy J, Academic Network for Conservational Hip Outcomes Research G. Reliability of a complication classification system for orthopaedic surgery. Clin Orthop Relat Res. 2012;470(8):2220-6. 9. U.S. Department of Health and Human Services NIoH, National Cancer, Institute. Common Terminology Criteria for Adverse Events (CTCAE). 2017 [updated November 27thJanuary 9th 2019]; 5th:[Available from: https://ctep.cancer.gov/protocoldevelopment/electronic_applications/docs/CTCAE_v5_Quic k_Reference_5x7.pdf. 10. Kirshblum SC, Biering-Sorensen F, Betz R, et al. International standards for neurological classification of spinal cord injury: cases with classification challenges. Top Spinal Cord Inj Rehabil. 2014;20(2):81-9. 11. Clavien PA, Sanabria JR, Strasberg SM. Proposed classification of complications of surgery with examples of utility in cholecystectomy. Surgery. 1992;111(5):518-26. 12. Dindo D, Demartines N, Clavien PA. Classification of surgical complications: a new proposal with evaluation in a cohort of 6336 patients and results of a survey. Ann Surg. 2004;240(2):205-13.
13
274
Figures
Figure 1: Details of types of surgical complications
14
Figure 2: Details of types of medical complications 275 276
Tables Table 1: Classification of perioperative complications in spine surgery Complexity of
Cause of
Therapeutic
Functional
Surgical Procedure*
Complication
Consequence. /
Deficit**
Sequelae I
A (mild)
0
M5/ASIA E
B (moderate)
-1
Motor deficit
Surgical Medical > M3/ASIA D II
C (severe)
-2
Motor deficit
15
< M3/ASIA C III
D (life-
-3
ASIA B
-4
ASIA A
threatening) E (death)
*According to Farshad et al. [7], ASIA: American Spinal Injury Association; ** Point difference; e.g.: a lesion of the spinal cord during an anterior cervical discectomy and fusion causing paraplegia with remaining sensory function: IISC -3 277 278 Table 2: Classification of complexity in spine surgery[7] Complexity I Lumbar microdiscectomy Lumbar posterior decompression Lumbar posterior instrumentation (pedicle screws) Lumbar kyphoplasty Lumbar vertebroplasty Complexity II Cervical posterior decompression Cervical posterior instrumentation Cervical posterior foraminotomy (Frykholm) Anterior cervical discectomy and fusion (ACDF) Cervical disc prosthesis Thoracic posterior decompression Thoracic posterior Instrumentation (pedicle screws) 16
Thoracic kyphoplasty Thoracic vertebroplasty Posterior/transforaminal lumbar interbody fusion Complexity III Occipitocervical instrumentation Atlantoaxial instrumentation Transthoracic decompression/instrumentation Lateral lumbar interbody fusion (LLIF) Anterior lumbar interbody fusion (ALIF) Lumbar disc prosthesis Hemi-/corpectomy
279 Table 3: Surgical details of index surgery of cases with a complication Localisation
n
Percent
Cervical
4
3.0%
Cervico-thoracal
2
1.5%
Thoracal
9
6.7%
Thoraco-lumbar
5
3.7%
Lumbar
61
45.2%
Lumbo-sacral
53
39.3%
Sacral
1
0,7
Intervention
17
Decompression
69
51,1
Instrumentation
66
48,9
280 Table 4: Complexity of surgical procedures I
II
III
Cause of
p-Value 0.389
Complication Surgical
60 (61.2%)
33 (33.7%)
5 (5.1%)
Medical
19 (51.4%)
17 (45.9%)
1(2.7%)
Therapeutic
0.441
Consequence/ Sequelae A
7 (53.8%)
5 (38.5%)
1 (7.7%)
B
34 (64.2%)
19 (35.8%)
0
C
32 (54.2%)
22 (37.3%)
5 (8.5%)
D
6 (60%)
4 (40%)
0
E
0
0
0
0
73 (60.3%)
43 (35.5%)
5 (4.1%)
-1
5 (50.0%)
4 (40.0%)
1 (10.0%)
-2
1 (-)
3 (-)
0
Functional Deficit** 0.476
*According to Farshad et al. [7],**Difference in pre- and post-surgery ASIA scale; 281 18
282 Table 5: Summary of Length of Hospital Stay Complexity of
n
Hospital Stay (days)
p-Value
I
79
13.68±23.97 (3-198)
0.730
II
50
12.42±12.70 (3-79)
III
6
19.17±6.79 (6-26)
Surgical
98
14.75±23.15 (3-198)
Medical
37
10.05±4.16 (4-17)
A
13 (9.6%)
5.62±1.61 (3-8)
B
53 (39.3%)
7.94±3.84 (3-21)
C
59 (43.7%)
13.07±8.07 (4-59)
D
10 (7.4%)
55.20±56.57 (14-198)
E
0
-
0
121 (89.6%)
10.42±6.71 (3-44)
-1
10 (7.4%)
32.00±58.68 (5-198)
-2
4 (3.0%)
59.00±36.34 (8-90)
Surgical Procedure*
Cause of Complication 0.224
Therapeutic Consequence/ Sequelae <0.001
Functional Deficit** <0.001
*According to Farshad et al. [7], ASIA: American Spinal Injury Association;
19
**Difference in pre- and post-surgery ASIA scale; 283
20
Classification of Perioperative Complications in Spine Surgery M. Farshad MD, MPH , A. Aichmair MD, MPH , C. Gerber MD , D.E. Bauer MD PII: DOI: Reference:
S1529-9430(19)31151-9 https://doi.org/10.1016/j.spinee.2019.12.013 SPINEE 58084
To appear in:
The Spine Journal
Received date: Revised date: Accepted date:
17 September 2019 17 December 2019 17 December 2019
Please cite this article as: M. Farshad MD, MPH , A. Aichmair MD, MPH , C. Gerber MD , D.E. Bauer MD , Classification of Perioperative Complications in Spine Surgery, The Spine Journal (2019), doi: https://doi.org/10.1016/j.spinee.2019.12.013
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier Inc.
1
Classification of Perioperative Complications in Spine Surgery
2
Farshad M. MD MPH1*, Aichmair A. MD MPH1, Gerber C. MD1, Bauer D.E. MD1
3 4
1
Department of Orthopaedics, Balgrist University Hospital, University of Zurich, Forchstrasse
5
340, 8008 Zurich, Switzerland
6 7
*Corresponding author:
8
Prof. Mazda Farshad MD MPH
9
Email: [email protected]
10
Phone: +41 44 386 3004
11 12 13
The authors have no financial interest to disclose
14
Abstract
15
Background Context: Perioperative complications affect surgical outcomes. Classification
16
systems of perioperative complications are well established and widely applied in many
17
surgical fields other than spine surgery.
18
Purpose: The aim of this study was to construct and validate a comprehensive classification
19
system for perioperative complications in spine surgery.
20
Study Design: Retrospective case series
21
Methods: A comprehensive classification system was constructed to stratify complications in
22
spinal surgery and consequently applied to 934 patients who consecutively underwent spine
23
surgery in a university hospital setting. A complication was defined as any kind of deviation
24
from the normal perioperative course, ranging from a postoperative anemia to death. The
25
comprehensive classifications system stratifies complications according to (1) complexity of 1
26
index procedure (2) immediate cause of complication (surgical vs medical) (3) the required
27
treatment and (4) potentially associated long-term functional deficits resulting from neural
28
injury. Subsequently, the proposed classification system was validated by applying the
29
duration of cumulative hospital stay as the primary outcome.
30
Results: Perioperative complications were recorded in 135 (14.3%) out of 934 cases. There
31
was a significant difference in the hospital stay between complications stratified according
32
to therapeutic consequences, grade A: 5.6±1.6 (range: 3-8) days, grade B: 7.9±3.8 (range: 3-
33
21) days, grade C: 13.1±8.1 (range: 4-59) days and grade D: 55.2±56.6 (range: 14-198) days,
34
respectively (p = <0.001). Also, there was a significant difference in hospital stay between
35
groups of increasing point difference of neurologic deficit, 0 vs. -1 and -1 vs. -2, respectively.
36
Conclusion: A comprehensive classification system for perioperative complications in spine
37
surgery (considering 4 categories) is presented and validated. The categories therapeutic
38
consequence (A to E) and decrease in neurological function correlate strongly with hospital
39
stay.
40
Key words: Spine surgery, Complications, Classification, Hospital stay, Complexity, Risk
41
factor;
2
42
Introduction
43
An objective and comparable quantification of complications in medical practice is
44
paramount to assess treatment quality and effectiveness.[1] Classification systems
45
stratifying the severity of complications are widely used in other medical fields such as
46
general surgery.[1-4] However, a similar comprehensive classification system focusing on
47
complications in spine surgery is not available yet.[5] Apart from its medical and economic
48
implications, a uniform definition and quantification of complications is necessary to
49
perform valid comparisons between clinical studies, quality of clinical care and performance
50
of surgical teams. Such a system is required to incorporate varying patient cohort
51
characteristics of the hospitals and the complexity of the procedures. It has been suggested
52
that the complexity of the surgical procedure plays a major role in risk estimation for
53
complications and that it is more predictive for assessment of health-care costs compared to
54
postoperative complications.[6] Recently, this study group proposed a classification system
55
to categorize the complexity of surgical procedures specifically for spine surgery.[7]
56
Complementing the established grading for complexity of surgical procedures we propose a
57
system to classify complications in spine surgery incorporating the previously established
58
findings. Therefore, the aim of this study was to construct and validate a comprehensive
59
classification system for complications in spine surgery, respecting the complexity of the
60
surgical procedure, the type of complications (medical vs surgical) and their therapeutic
61
consequences, as well as potential neurological decline.
62
3
63
Materials & Methods
64
After approval of the state ethical committee, patients who consecutively underwent spine
65
surgery between 05/2014 and 12/2015 at a single Swiss university clinic were included in the
66
present study if the following criteria were met: available data set, age at surgery > 18 years,
67
and informed consent. As previously proposed, any deviation from a regular postoperative
68
course not including sequela or failure to cure was defined as complication and therefore
69
included for final analysis.[1]
70
Data were collected on age, gender, body mass index (BMI), medication, smoking status,
71
preoperative American Society of Anesthesiologists (ASA) classification, laboratory values as
72
well as surgical details such as clinical/radiographic surgical indication, blood loss, duration
73
of surgery, revision surgery, and type of surgery. Furthermore, postoperative length of
74
intermediate care unit (IMC) and hospital stay were documented. In cases where patients
75
were readmitted for the treatment of a postoperative complication, the days of hospital stay
76
of subsequent readmissions were added up and consequently termed “cumulative hospital
77
stay”. The cumulative hospital stay was chosen as the most relevant surrogate for
78
perioperative outcome.[1] Therefore, validation of the proposed classification system was
79
performed by correlating increasing grades of complications to this parameter.[1] Also, the
80
complexity[7] of surgical intervention and the occurrence and sequelae of intra- and
81
perioperative complications were documented. This database has been used in another
82
study analyzing predictive risk factors for perioperative complications and morbidities in
83
spine surgery.[7] A subset of these variables was ultimately used in this study.
84 85 86
4
87
Stratification of Complication Severity
88
Complications were defined as any kind of deviation from a standard perioperative course
89
ranging from a symptomatic anemia to death.
90
A consensus statement was reached to comprehensively classify the severity of
91
complications based on: (1) the previously proposed complexity of the performed surgical
92
procedure[7] (table 2) (2) whether the complication was directly or indirectly related to the
93
surgical procedure, consequently termed “surgical” (s) or “medical” (m) (3) the treatment
94
required to manage the complication (graded from A-E) similar to the modified approached
95
described by Sink et al.[8] and the grading of complications according to Common
96
Terminology Criteria for Adverse Events (CTCAE)[9] (4) and associated long-term functional
97
deficits resulting from nerve injury in accordance with the American Spinal Injury Association
98
(ASIA) Score[10]. Intraoperative injuries resulting in myelopathy were graded as ASIA E to A,
99
injuries resulting in radiculopathy as either “no loss of motor function” (sensory deficits only)
100
or “motor useful” (key muscle strength > M3) and “motor useless” (key muscle strength <
101
M3).[10] To account for preoperatively existing neurologic deficits, only the point-difference
102
between pre- and postoperative deficits was incorporated into the final score (table 1).
103
(e.g. a lesion of the spinal cord during an anterior cervical discectomy and fusion causing
104
paraplegia with remaining sensory function would be classified as: IISC -3)
105
5
106
Statistical Analysis
107
Continuous variables are reported as mean ± standard deviation (SD), whereas categorical
108
variables are reported as frequencies and proportions. The Kolmogorov Smirnov test was
109
used to test for normal distribution of data. The Mann-Whitney U test was used for the
110
comparison of continuous variables for non-normal distributed data. The Pearson’s chi
111
squared test was used for the comparison of proportions between groups. Comparison of
112
continuous variables between the different groups of surgical complications was performed
113
via analysis of variance (ANOVA). The Bonferroni method of multiple comparisons was used
114
for post-hoc analysis. Statistical analysis was performed using IBM SPSS Statistics, Version
115
24.0 (IBM Corp., Armonk, NY).
6
116
Results
117
A total number of 1067 of patients consecutively underwent spine surgery at a single center,
118
out of whom 934 (female: 448, male: 486) met the defined criteria to be included in the
119
present study (87.5%). One hundred and thirty-five deviations from unremarkable
120
perioperative course (defined here as complications) (14.30%) were recorded (female: 59,
121
male: 76) and were included for final analysis. The average age at surgery in the group of
122
patients sustaining a postoperative complication was 61.45±16.21 (range: 23-87) years, and
123
the average BMI 27.91±5.59 (range: 15.62-55.78) kg/m2. An active smoking status was
124
recorded in 53 (37.30%). Preoperative assessment revealed an ASA class I in 14.8% (n=20),
125
class II in 46.7% (n=63), class III in 34.8% (n=47), and class IV in 3.7% (n=5). None of the
126
patients was classified as ASA class V or VI. Further surgical details describing the index
127
procedure are illustrated in table 3.
128 129
Complexity of Intervention
130
The 3 grades of complexity of spinal surgical procedures have previously been described in
131
detail.[7] (table 2) Surgical interventions with complexity grade I (e.g. midline
132
decompression, etc) were recorded in 58.5% (n=79), complexity grade II (e.g. anterior
133
cervical discectomy and fusion, etc) in 37.0% (n=50) and complexity grade III (e.g. anterior
134
scoliosis correction, etc) 4.4% (n=6) of cases with a complication, respectively. Higher grades
135
of complications were not significantly associated with increasing complexity of the
136
intervention. (table 5)
137 138
Stratification of Complication Severity
7
139
Stratification of complications was performed according to the above-mentioned consensus
140
statement. Complications regarded as directly related to the index procedure (surgical) were
141
recorded in 72.6% (n=98) and regarded as indirectly related to the index procedure (medical)
142
in 27.4% (n=37). (table 4) Three cases sustained both, a medical and a surgical complication.
143
In those three cases the therapeutic consequence, and hence complication grade of the
144
surgical complication was regarded higher than the medical complication. For further
145
analysis these cases were treated as surgical complications. The most frequent surgical
146
complications were recurrent disc herniation (30.19% of all surgical complications) and
147
superficial wound complications (12.26% of all surgical complications). The most common
148
medical complications were postoperative symptomatic anemia (40% of all medical
149
complications) and postoperative electrolyte disturbances (31.43% of all medical
150
complications). Further details on surgical and medical complications are illustrated in
151
figures 1 and 2, respectively.
152
Considering therapeutic consequence, 9.6% (n=13) of complications were stratified as grade
153
A (mild), 39.3% (n=53) as grade B (moderate), 43.7% (n=59) as grade C (severe) and 7.4%
154
(n=10) as grade D (life threatening), respectively. Death (grade E) was recorded in none of
155
the cases. In terms of permanent neurologic deficit, a point difference of 0 was noted in
156
89.6% (n=121), a point difference of 1 in 7.4% (n=10) and a point difference of 2 in 3.0%
157
(n=4). A point difference of greater than 2 was recorded in none of the cases.
158 159
Validation of the classification system
160
The mean length of cumulative hospital stay for patients sustaining a postoperative
161
complication was 13.5±19.9 (range: 3-198) days.
8
162
There was no significant difference in the length of hospital stay between cases sustaining
163
medical or surgical complications with 10.1±4.2 (range: 4-17) vs. 14.8±23.2 (range: 3-198)
164
days, respectively (p 0.224).
165
There was a significant difference in the length of hospital stay between complications
166
stratified according to therapeutic consequences, grade A: 5.6±1.6 (range: 3-8) days, grade
167
B: 7.9±3.8 (range: 3-21) days, grade C: 13.1±8.1 (range: 4-59) days and grade D: 55.2±56.6
168
(range: 14-198) days, respectively (p = <0.001). A post hoc analysis revealed a significant
169
difference for complications graded A vs. D, B vs. D and C vs. D, (p = < 0.001). There was no
170
significant difference in length of hospital stay between groups A vs. B (p = 1.00), A vs. C (p =
171
0.779) and B vs. C (p = 0.553).
172
There was a significant difference in the length of hospital stay between groups of increasing
173
point difference of neurologic deficit, 0 vs. -1 and -1 vs. -2, respectively. A summary of the
174
difference in length of hospital stay between increasing grades of complication is illustrated
175
in table 5.
9
176
Discussion
177
The aim of this study was to construct and validate a comprehensive classification system for
178
complications in spine surgery, respecting the complexity of the surgical procedure, the type
179
of complications (medical vs surgical) and their therapeutic consequences, as well as
180
permanent neurological deficits. Others (Clavien PA and Dindo D)1 pioneered in the field of
181
grading and defining complications for surgical procedures in general/visceral surgery by
182
proposing a therapy-oriented classification system in 1992 and its subsequent modification
183
in 2004.[1, 11] However, as opposed to this now widely applied classification system
184
specifically developed for complications in general surgery and its subsequent adaptation for
185
orthopedic surgery[8], no comparable instrument has been made available respecting the
186
peculiarity of spine surgery where localized injury to nervous tissue of lesser extent may lead
187
to distant loss of function of far greater implication. Also, as a result of the paucity of
188
treatment options, complications including postoperative paraplegia might not be followed
189
by further surgical intervention. Furthermore, we believe that a comprehensive classification
190
system for complications should incorporate the complexity of the surgical procedure. The
191
validity of stratifying surgical interventions into three grades of increasing complexity (table
192
2) was previously demonstrated by this study group as a first step to lay the basis for a
193
comprehensive classification system. In detail, it was shown that the risk for an IMC stay
194
longer than 24h is increased for procedures of complexity grades II and III compared to
195
complexity grade I by 3.5-fold and 5.4-fold, respectively.[7] A subgroup analysis of the same
196
database confirming these findings was performed in this study including patients sustaining
197
a perioperative complication only.
198
It is the authors' experience that surgeons might frequently not fully consider adverse events
199
not directly related to the surgical treatment as complication. However, based on the
10
200
definition proposed by Clavien and Dindo, a complications is “any negative outcome not
201
including failure to treat or sequalae.”[1] Standardized definitions for the most frequent
202
complications not directly related to a surgical treatment have been defined by CTCAE.[9]
203
These were incorporated into the proposed classification system and subsequently termed
204
“medical” and amongst other include urinary tract infection, symptomatic postoperative
205
anemia or electrolyte disturbances. (figure 2)
206
For the third modifier of the classification system, we used the already established and
207
reproducible outcome parameters for stratification of complications into grades A to E
208
depending on the required treatment of the complication according to the Common
209
Terminology Criteria for Adverse Events (CTCAE).[9] The CTCAE is a well-established and
210
validated classification that allows the grading of adverse events throughout multiple organ
211
systems and corresponds widely with the more specific classification system described by
212
Clavien and Dindo[1].
213
therapeutic intervention graded highest as “D”, therefore confirming this notion with some
214
limitations.
215
A similar approach was pursued to grade persistent neurologic impairment as a result of
216
intraoperative complications. For loss of function after injury to neuronal tissue the
217
American Spinal Injury Association (ASIA) score for injury of the spinal cord, and muscle
218
strength (strength > grade M3: “motor useful” or strength < grade M3: “motor useless”) as
219
defined by the ASIA for nerve root injury alone were utilized.[10]
220
As a result of the small sample size, the available data did not permit for validation of
221
stratification of complications according to permanent neurologic deficit utilizing the length
222
of hospital stay. However, due to the implications of spinal cord injury or nerve root it seems
In this study, patients sustaining a complication requiring a
11
223
rational to include a modifier reflecting these complications into a classifications system in
224
spine surgery.
225
This study has limitations that need to be considered and addressed in further steps of
226
validation of the classification system. A retrospective data analysis was performed, with the
227
potential for introducing bias including underreporting of complications. Further, although
228
utilized in other studies [12], the duration of hospital stay remains only a surrogate
229
parameter for validation of this classification systems. As a result of its complexity, the
230
proposed classification system has limited applicability for daily clinical practice.
231
However, despite its limitations, the authors are confident to have constructed a valuable
232
classification tool for grading of perioperative complications, specifically designed for spine
233
surgery incorporating the complexity of the surgical intervention (table 1 and 2). This should
234
help for better quality control processes by facilitating valid comparisons of outcomes in
235
spine surgery between cases and institutions.
236
12
237
References
238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273
1. Clavien PA, Barkun J, de Oliveira ML, et al. The Clavien-Dindo classification of surgical complications: five-year experience. Ann Surg. 2009;250(2):187-96. 2. DeOliveira ML, Winter JM, Schafer M, et al. Assessment of complications after pancreatic surgery: A novel grading system applied to 633 patients undergoing pancreaticoduodenectomy. Ann Surg. 2006;244(6):931-7; discussion 7-9. 3. Chun YS, Vauthey JN, Ribero D, et al. Systemic chemotherapy and two-stage hepatectomy for extensive bilateral colorectal liver metastases: perioperative safety and survival. J Gastrointest Surg. 2007;11(11):1498-504; discussion 504-5. 4. de Santibanes E, Ardiles V, Gadano A, Palavecino M, Pekolj J, Ciardullo M. Liver transplantation: the last measure in the treatment of bile duct injuries. World J Surg. 2008;32(8):1714-21. 5. Goldhahn S, Sawaguchi T, Audige L, et al. Complication reporting in orthopaedic trials. A systematic review of randomized controlled trials. J Bone Joint Surg Am. 2009;91(8):1847-53. 6. Aust JB, Henderson W, Khuri S, Page CP. The impact of operative complexity on patient risk factors. Ann Surg. 2005;241(6):1024-7; discussion 7-8. 7. Farshad M, Bauer DE, Wechsler C, Gerber C, Aichmair A. Risk factors for perioperative morbidity in spine surgeries of different complexities: a multivariate analysis of 1,009 consecutive patients. Spine J. 2018. 8. Sink EL, Leunig M, Zaltz I, Gilbert JC, Clohisy J, Academic Network for Conservational Hip Outcomes Research G. Reliability of a complication classification system for orthopaedic surgery. Clin Orthop Relat Res. 2012;470(8):2220-6. 9. U.S. Department of Health and Human Services NIoH, National Cancer, Institute. Common Terminology Criteria for Adverse Events (CTCAE). 2017 [updated November 27thJanuary 9th 2019]; 5th:[Available from: https://ctep.cancer.gov/protocoldevelopment/electronic_applications/docs/CTCAE_v5_Quic k_Reference_5x7.pdf. 10. Kirshblum SC, Biering-Sorensen F, Betz R, et al. International standards for neurological classification of spinal cord injury: cases with classification challenges. Top Spinal Cord Inj Rehabil. 2014;20(2):81-9. 11. Clavien PA, Sanabria JR, Strasberg SM. Proposed classification of complications of surgery with examples of utility in cholecystectomy. Surgery. 1992;111(5):518-26. 12. Dindo D, Demartines N, Clavien PA. Classification of surgical complications: a new proposal with evaluation in a cohort of 6336 patients and results of a survey. Ann Surg. 2004;240(2):205-13.
13
274
Figures
Figure 1: Details of types of surgical complications
14
Figure 2: Details of types of medical complications 275 276
Tables Table 1: Classification of perioperative complications in spine surgery Complexity of
Cause of
Therapeutic
Functional
Surgical Procedure*
Complication
Consequence. /
Deficit**
Sequelae I
A (mild)
0
M5/ASIA E
B (moderate)
-1
Motor deficit
Surgical Medical > M3/ASIA D II
C (severe)
-2
Motor deficit
15
< M3/ASIA C III
D (life-
-3
ASIA B
-4
ASIA A
threatening) E (death)
*According to Farshad et al. [7], ASIA: American Spinal Injury Association; ** Point difference; e.g.: a lesion of the spinal cord during an anterior cervical discectomy and fusion causing paraplegia with remaining sensory function: IISC -3 277 278 Table 2: Classification of complexity in spine surgery[7] Complexity I Lumbar microdiscectomy Lumbar posterior decompression Lumbar posterior instrumentation (pedicle screws) Lumbar kyphoplasty Lumbar vertebroplasty Complexity II Cervical posterior decompression Cervical posterior instrumentation Cervical posterior foraminotomy (Frykholm) Anterior cervical discectomy and fusion (ACDF) Cervical disc prosthesis Thoracic posterior decompression Thoracic posterior Instrumentation (pedicle screws) 16
Thoracic kyphoplasty Thoracic vertebroplasty Posterior/transforaminal lumbar interbody fusion Complexity III Occipitocervical instrumentation Atlantoaxial instrumentation Transthoracic decompression/instrumentation Lateral lumbar interbody fusion (LLIF) Anterior lumbar interbody fusion (ALIF) Lumbar disc prosthesis Hemi-/corpectomy
279 Table 3: Surgical details of index surgery of cases with a complication Localisation
n
Percent
Cervical
4
3.0%
Cervico-thoracal
2
1.5%
Thoracal
9
6.7%
Thoraco-lumbar
5
3.7%
Lumbar
61
45.2%
Lumbo-sacral
53
39.3%
Sacral
1
0,7
Intervention
17
Decompression
69
51,1
Instrumentation
66
48,9
280 Table 4: Complexity of surgical procedures I
II
III
Cause of
p-Value 0.389
Complication Surgical
60 (61.2%)
33 (33.7%)
5 (5.1%)
Medical
19 (51.4%)
17 (45.9%)
1(2.7%)
Therapeutic
0.441
Consequence/ Sequelae A
7 (53.8%)
5 (38.5%)
1 (7.7%)
B
34 (64.2%)
19 (35.8%)
0
C
32 (54.2%)
22 (37.3%)
5 (8.5%)
D
6 (60%)
4 (40%)
0
E
0
0
0
0
73 (60.3%)
43 (35.5%)
5 (4.1%)
-1
5 (50.0%)
4 (40.0%)
1 (10.0%)
-2
1 (-)
3 (-)
0
Functional Deficit** 0.476
*According to Farshad et al. [7],**Difference in pre- and post-surgery ASIA scale; 281 18
282 Table 5: Summary of Length of Hospital Stay Complexity of
n
Hospital Stay (days)
p-Value
I
79
13.68±23.97 (3-198)
0.730
II
50
12.42±12.70 (3-79)
III
6
19.17±6.79 (6-26)
Surgical
98
14.75±23.15 (3-198)
Medical
37
10.05±4.16 (4-17)
A
13 (9.6%)
5.62±1.61 (3-8)
B
53 (39.3%)
7.94±3.84 (3-21)
C
59 (43.7%)
13.07±8.07 (4-59)
D
10 (7.4%)
55.20±56.57 (14-198)
E
0
-
0
121 (89.6%)
10.42±6.71 (3-44)
-1
10 (7.4%)
32.00±58.68 (5-198)
-2
4 (3.0%)
59.00±36.34 (8-90)
Surgical Procedure*
Cause of Complication 0.224
Therapeutic Consequence/ Sequelae <0.001
Functional Deficit** <0.001
*According to Farshad et al. [7], ASIA: American Spinal Injury Association;
19
**Difference in pre- and post-surgery ASIA scale; 283
20