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Worldwide Survey on the Use of Navigation in Spine Surgery
PEER-REVIEW REPORTS
Worldwide Survey on the Use of Navigation in Spine Surgery Roger Härtl1, Khai Sing Lam 2, Jeffrey Wang 3, Andreas Korge 4, Frank Kandziora5, Laurent Audigé6
SPINE Key words 䡲 Expert opinion 䡲 Internet-based opinion survey 䡲 Spine surgery 䡲 Surgery, computer-assisted Abbreviations and Acronyms AP: Asia Pacific CAS: Computer-assisted surgery CI: Confidence interval EU: Europe LA: Latin America ME: Middle East (including Africa) MIS: Minimally invasive spinal surgery NA: North America OR: Operating room From the 1 Brain and Spine Center, Weill Cornell Medical College, New York, 2 New York, USA; London Spine Center, Guy’s and St. Thomas’ NHS Foundation Hospitals, London, United Kingdom; 3UCLA Comprehensive Spine Center, Santa Monica, California, USA; 4Schön Klinik München Harlaching, Munich, Germany; 5BG Trauma Clinic Frankfurt am Main, Center for Spinal Surgery and Neurotraumatology, Frankfurt, Germany; and 6AO Clinical Investigation and Documentation, AO Foundation, Duebendorf, Switzerland To whom correspondence should be addressed: Roger Härtl, M.D. [E-mail: [email protected]] Citation: World Neurosurg. (2013) 79, 1:162-172. http://dx.doi.org/10.1016/j.wneu.2012.03.011
䡲 OBJECTIVE: Computer-assisted surgery (CAS) can improve the accuracy of screw placement and decrease radiation exposure, yet this is not widely accepted among spine surgeons. The current viewpoint of spine surgeons on navigation in their everyday practice is an important issue that has not been studied. A survey-based study assessed opinions on CAS to describe the current global attitudes of surgeons on the use of navigation in spine surgery. 䡲 METHODS: A 12-item questionnaire focusing on the number and type of surgical cases, the type of equipment available, and general opinions toward CAS was distributed to 3348 AOSpine surgeons (a specialty group within the AO [Arbeitsgemeinschaft für Osteosynthesefragen] Foundation). Latent class analysis was used to investigate the existence of specific groups based on the respondent opinion profiles. 䡲 RESULTS: A response rate of 20% was recorded. Despite a widespread distribution of navigation systems in North America and Europe, only 11% of surgeons use it routinely. High-volume procedure surgeons, neurological surgeons, and surgeons with a busy minimal invasive surgery practice are more likely to use CAS. “Routine users” consider the accuracy, potential of facilitating complex surgery, and reduction in radiation exposure as the main advantages. The lack of equipment, inadequate training, and high costs are the main reasons that “nonusers” do not use CAS. 䡲 CONCLUSIONS: Spine surgeons acknowledge the value of CAS, yet current systems do not meet their expectations in terms of ease of use and integration into the surgical work flow. To increase its use, CAS has to become more cost efficient and scientific data are needed to clarify its potential benefits.
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INTRODUCTION Spine surgery inherently carries the potential of injury to the spinal cord, nerves, and important vascular structures. Incorrectly positioned implants and screws, which significantly breach the pedicle, can cause spinal, nerve root, or vascular injury, as well as dural tears and cerebrospinal fluid leaks (5, 17). Intuitively, it makes sense that implants placed with greater accuracy are preferred. There is general agreement among surgeons that imaging techniques are essential for safe and accurate placement of spinal instrumentation regardless of the complexity of the operation, the anatomic region,
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and the level of training and comfort level of the individual surgeon. Traditionally, this has involved the use of radiograph or image intensification guidance, either as a control at the end of a procedure or for active guidance throughout surgery. More recently, stereotactic two- or threedimensional imaging techniques have been developed and gained acceptance in disciplines such as cranial neurosurgery and certain orthopedic trauma procedures. The use of stereotactic computer-assisted surgery (CAS) was first described for spinal instrumentation placement in the mid-1990s (6, 9, 14, 15) and the different types of CAS have been reviewed (11). Computer three-dimensional navigation techniques in spinal instrumentation can improve screw place-
ment accuracy, potentiate the ability to maximize the screw diameter relative to the pedicle, and reduce potential injury to critical neurovascular structures (1, 2, 7, 12, 16, 18, 19). Despite further reports suggesting that CAS can improve accuracy of screw placement and decrease radiation exposure (3, 10, 13–15, 17, 20), it has not been generally accepted among spine surgeons and there is no clinical evidence that CAS in spinal surgery leads to improved patient outcomes. The reasons for this lack of acceptance are probably complex and may involve factors related to availability, training, individual experience and preference, and cost-effectiveness, among others. A better understanding of these reasons is essential in determining the
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current deficits of navigation and how these can be addressed. The present study was conducted to evaluate the current attitudes toward spine navigation, the perceived problems, and further issues that could potentially be addressed to increase acceptance of navigation among international orthopedic, trauma, and neurological spine surgeons.
MATERIALS AND METHODS A 12-item questionnaire was developed to assess the experiences of AOSpine surgeons with computer navigation and their current attitudes toward its use in spine surgery (Appendix 1). (AOSpine [a speciality within the AO Foundation] is an international community of spine surgeons, orthopedic surgeons, neurosurgeons, academics, researchers, and other spine care professionals dedicated to delivering knowledge, experience,
and evidence to improve patient care and outcomes. The AO Foundation is a medically guided, non-profit organization led by an international group of surgeons specialized in the treatment of trauma and disorders of the musculoskeletal system.) The questionnaire contained three parts: (1) demographics (i.e., region, subspecialty) and basic information regarding the number and type of surgical cases performed; (2) targeted information about the type of navigation equipment available to the surgeon, their level of training, and the number of cases performed with or without navigation; and (3) general opinions toward navigation and its potential benefits. All questions were closed-ended with predesigned answer options from which the respondent could choose one answer. In May 2009, the Web-based questionnaire was distributed to 3348 members of AOSpine Asia Pacific (AP), Europe (EU), Latin America (LA), Middle East (including Africa) (ME) and North America (NA) by
means of an invitation e-mail. This e-mail contained a link directing the respondents to SurveyMonkey where the questionnaire could be completed online. A reminder email was sent out to members who had not initially responded, and the Web site was closed in August 2009.
Statistical Analysis Survey data were formatted and analyzed using Intercooled Stata Version 11 (StataCorp LP; College Point, Texas, USA). Categorical variables were described using absolute and relative frequencies and responses to questions 1–8 were stratified by region and type of surgeon.
Latent Class Analysis and Surgeons’ Opinion Profile on Navigation Survey participants provided their views using rating scales concerning seven claimed benefits of computer-assisted navigation (question 9) including: (1) speed, (2) accuracy, (3)
Figure 1. Distribution of the survey respondents based on their geographic region and surgeon subspecialty.
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Table 1. Summary of the Survey Responses to Questions 1– 8 Number of Responses
%
Asia Pacific (n ⫽ 822)
139
17
Europe (n ⫽ 1086)
252
23
Latin America (n ⫽ 660)
145
22
Middle East (n ⫽ 272)
52
19
North America (n ⫽ 508)
60
12
139
21
Europe
252
39
Latin America
145
22
Middle East
52
8
North America
60
9
Not known
29
Region (response rate)*
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Regional distribution of respondents Asia Pacific
Spine surgeon Neurological spine surgeon
210
32
Orthopedic surgeon
401
60
Trauma spine surgeon
55
8
Not known
11
Number of fusions per year 0–50
249
39
51–100
193
30
101–200
127
20
⬎200
69
11
Not known
39
Percentage of fusions performed with MIS ⬍10%
441
70
10%–25%
113
18
26%–50%
43
7
⬎50%
37
6
Not known
43
CAN available? Yes
237
38
No
386
62
Not known
54
Participated in a CAN course? Yes
217
35
No
408
65
Not known
52
makes complex surgeries safer, (4) preoperative planning, (5) less radiation, (6) avoids wrong level surgery, and (7) enables less invasive surgery. To investigate the existence of groups of surgeons sharing similar opinion profiles, we applied the technique of latent class modeling (8) using the software Latent Gold Version 4.0.3 (Statistical Corporation; Belmont, Massachusetts, USA). Latent class modeling is a technique based on the principle that surgeons truly belong to distinguishable opinion groups (e.g., those strongly believing in the benefit of navigation vs. those not believing in its benefit) that cannot be directly observed (hence the term latent), but are only indirectly documented using the sevenanswer item set. The analysis aims at identifying the most probable opinion groups for further investigation on the relationship between having a specific opinion profile and the use of navigation.
Factors Influencing the Use (or nonuse) of Navigation in Spine Fusion We investigated factors (independent variables) influencing the routine use of navigation (yes) versus never (no) (dichotomous-dependent variables). These factors included the surgeon’s profile; the annual number of spine fusions performed; the percentage of fusions performed using a minimal invasive technique; the availability of computer-assisted navigation for spine surgery at the respondent’s hospital; previous participation in a course on computer-assisted navigation; and the surgeon’s belief about the benefit of navigation (i.e., opinion groups). This analysis was exploratory. In multivariable logistic regression analyses, factors that were not significant at the 0.05 level were excluded manually from the model in a backward procedure. A final multivariable binomial regression model was fitted to derive adjusted relative risks (4).
RESULTS
Routine use of CAN for spinal fusions Yes, routinely
58
9
No, only in selected cases
151
25
Never
411
66
Not known MIS, minimal invasive surgery; CAN, computer-assisted navigation. *Based on total number of AOSpine members invited to respond.
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57
Respondent Demographics (questions 1– 8) Surgeon Characteristics. From a total of 3348 spine surgeons, 677 surgeons (20%) submitted complete or incomplete responses. The majority of the respondents were from EU, LA, and AP (39%, 22%, and 21%, respectively) (Figure 1 and Table 1). Only 60
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use fluoroscopy. Similar proportions of orthopedic (73%) and neurological (87%) surgeons use fluoroscopy. However, more orthopedists (18%) use this guidance technique only as a control at the end of the procedure than their neurosurgeon colleagues (4%).
Figure 2. Proportion of spine fusions performed annually.
respondents were from NA (9%) and most (60%) were orthopedic spine surgeons. Number of Fusions per Year. Half (50%) of the responding surgeons perform between 51 and 200 spinal fusions per year, with only 11% performing more than 200 procedures yearly (Table 1). NA respondents perform the highest proportion of spinal fusions with 50% undertaking more than 100 fusions per year (Figure 2). The lowest number of fusions is performed in LA, where the majority (84%) of respondents perform less than 100 procedures annually. There was no significant difference between the numbers of fusions (⬎100) performed per year for neurological (27%) and orthopedic (32%) surgeons.
Minimally Invasive Spinal Surgery. The majority (70%) of surgeons use minimally invasive spinal surgery (MIS) for less than 10% of the total fusion procedures performed (Table 1). The highest proportion of MIS fusions is performed in NA and EU where 18%–20% of surgeons use this technique for more than 25% of their spinal fusions (Figure 3). Neurological (9%) and trauma (8%) surgeons use MIS fusion techniques more frequently (i.e., ⬎50% of all fusions performed) than orthopedists (4%). Use of Regular Anteroposterior/Lateral Fluoroscopy. Seventy-eight percent of the surgeons use routine fluoroscopy during spine surgery. Interestingly, almost 9% of all respondents and 21% of the NA surgeons do not
Figure 3. Proportion of fusions performed annually using minimal invasive surgery.
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Availability, Training Level, and Use of Spinal Navigation. Overall, 38% of the surgeons indicated that they have access to computerassisted navigation facilities (Table 1). Seventy percent of NA surgeons have CAS available at their hospitals compared with about 42% in EU and AP, and only 14% in LA (Figure 4). Neurological (45%) and trauma (47%) surgeons had slightly more access to CAS compared with orthopedists (33%). Thirty-five percent of the surgeon population has participated in a CAS training course (Table 1). Surgeons from NA have the greatest exposure to training courses (57%) compared with those from other regions (27%–36%). Trauma surgeons have participated in training courses most frequently (50%), followed by neurological (39%) and orthopedic surgeons (31%). Based on question 8a, surgeons were divided into “nonusers,” “routine users,” and “selective users.” Overall, 66% of surgeons never use CAS (nonusers) for spinal fusion surgery, 9% are routine users, and the remaining (25%) are selective users (Table 1). In NA, more than half of the surgeons (52%) use CAS routinely or in selected cases (Figure 5). More than 40% for both the neurological and trauma surgeon groups use CAS routinely or in selected cases compared with only 28% orthopedic surgeons. Within the group of 58 routine CAS users comprising 26 neurological, 23 orthopedic, and 9 trauma surgeons, 10% use CAS in 26%– 50% of their spinal fusion cases and 53% use it in more than 50% of cases. Surgeons with a higher volume of spinal fusions per year use CAS more than surgeons doing less fusion surgery (Figure 6). Up to 59% of surgeons doing more than 200 spinal fusions per year use spinal navigation routinely or in selected cases compared with only 21% of surgeons performing less than 50 fusions yearly.
Attitudes Toward Navigation (questions 9 –12) Perceived Benefits of CAS. Various factors considered as benefits of CAS by more than
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SPINE Figure 4. Availability of computer-assisted navigation systems.
75% of the survey population included its accuracy, the potential of rendering complex surgery safer, and the possible reduction of radiation. The use of CAS in MIS, for preoperative planning, and the avoidance of wrong level surgery were also considered beneficial for 60%–70% of the respondents. However, about 60% indicated that CAS did not provide any benefit in terms of operative speed. The routine users of CAS (n ⫽ 58) pointed out the same advantages but believed more strongly about the benefits of its accuracy, the potential of making complex surgery safer, and the possible reduction of radiation exposure (i.e., ⬎90% assigned great or some benefit to CAS in making complex surgery safer and more ac-
curate). Almost 50% agreed that speed was not a benefit or that it needed improvement. The majority of respondents who were nonusers (n ⫽ 411) had a less well-defined understanding of the potential benefits of CAS. Between 65% and 83% indicated great or some benefit for all answer options except for speed. Reasons for Not Using CAS. High costs, the lack of CAS equipment, increase in operating room (OR) time, and no or inadequate training were quoted as the important/most important reasons for not using CAS at all or more often by 52%–73% of all surgeons. The lack of proven benefit, disturbance of the OR work flow, and concerns about accuracy were believed to be less important.
Figure 5. Routine use of computer-assisted navigation for spine fusion surgery.
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For the routine users, almost 80% indicated the increased OR time associated with CAS as the main reason for not using it more frequently. Problems with the OR work flow and cost reimbursements were only believed to be important/most important by less than 50% of these surgeons. The lack of proven benefit was the least important concern. Similar responses were documented by the selective users of CAS (n ⫽ 151). Of the nonusers, 80% indicated a lack of equipment and high costs as the important/ most important reasons for not using CAS, followed by 62% quoting inadequate training, and 50%–55% rating the increase in OR time and lack of reimbursement as important/most important reasons for not using CAS. Requirements for CAS to be Used More. All respondents indicated that more data supporting the precision (88%), reduced radiation exposure, and cost-effectiveness of CAS (both 79%), as well as more scientific evidence supporting its use (75%) and a positive impact on operative times (74%) are important/most important factors required to convince them to use it at all or more frequently. Data supporting better precision and reduced radiation exposure (both 87%) were important/most important factors, followed by the ability of CAS to save time in the OR (68%) for the routine users. Cost-effectiveness, scientific evidence supporting its use, clarification of reimbursement issues, and the avoidance of wrong level surgery were also quoted by 50%– 65% of this group as important/ most important factors. In addition to data on precision, costeffectiveness, radiation exposure, and operative times (73%– 88%), 73% of the 411 nonusers indicated that they would use CAS if it was available at their hospital and 65% indicated they would use it if training was available. Greatest Potential Benefit of CAS. More than 75% of all surgeons considered MIS, revision cases, deformity surgery, and thoracic spine surgery as areas that would most likely benefit from CAS. Surgery of the cervical spine and preoperative/intraoperative planning for instrumentation were also considered important areas for CAS by most surgeons. In contrast, less than 50% of the survey population considered simple
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NA (Fisher’s exact test; P ⬍ 0.001), but did not belong to a particular surgeon type (P ⫽ 0.38). Only 25% and 48% of the surgeons with very strong and strong expectations, respectively, have CAS available at their institution compared with 41% of those with poor views on navigation (Table 3). Even 5% of the routine users have poor beliefs and surgeons with a high volume of fusions (26%) were less likely to be strong believers in CAS. Factors Influencing the Routine Use of Navigation. The final multivariable binomial model outlined in Table 4 included the following factors:
Figure 6. Comparison of the routine use of computer-assisted navigation with the proportion of fusions performed annually.
decompression surgery, disc arthroplasty, pain treatment, vertebral augmentation procedures, and intraoperative confirmation of the correct level as relatively unimportant areas for CAS. Respondent Opinion Profiles and Demographics. Latent class analysis of the opinion ratings identified four classes of surgeons according to their belief on the current benefit of navigation. The classes are described by the mean scale responses for each of the seven rating scales (Table 2). One class included 22% of all surgeons with poor opinion about the benefit of navigation with mean scale responses ranging
y Orthopedic spine surgeons were 0.6
from 1.67–2.95. Forty-two percent showed a more positive view of navigation with mean scale responses higher by almost one point on each scale, in particular for “accuracy” and “makes complex surgeries safer.” The last two respondent classes demonstrated strong to very strong views about the benefit of navigation with mean scores ranging from 2.54 for “speed” to more than 4.80 for other items. Each respondent was allocated to one of these four belief classes according to their response profile (Table 3). The distribution of the classes per region and type of surgeon showed that more very strong believers of navigation originated from LA than EU and
Table 2. Mean Response Data for the Surgeon Classes Characterized by Their Belief on the Current Benefit of Navigation in Spine Fusion
1
2
3
4
Potential benefits
Poor
Moderate
Strong
Very Strong
Class size (n ⫽ 574)
22%
19%
18%
Speed
1.67
1.98
2.54
3.96
Accuracy
2.71
4.14*
4.98*
4.89*
Makes complex surgeries safer
2.53
4.24*
4.91*
4.90*
Preoperative planning
2.66
3.62
3.54
4.82*
Less radiation
2.95
3.95
4.17*
4.90*
Avoids wrong level surgery
2.44
3.20
3.44
4.88*
Enables less invasive surgery
2.70
3.67
3.97
4.89*
*These numbers represent the mean scale responses of ⬎4.00 –5.00.
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y Surgeons performing ⱖ10% of their fusions with MIS were 1.7 times more likely to routinely use navigation compared with those performing less than 10% (95% CI 1.1–2.5; P ⫽ 0.019).
y When computer-assisted navigation for spinal surgery was available at the surgeon’s hospital, he or she was 14 times more likely to use it routinely (95% CI 5.0 –38.4; P ⬍ 0.001).
y Surgeons who participated in a course on computer-assisted navigation were 2.2 times more likely to use navigation routinely compared with those who did not (95% CI 1.3–3.6; P ⫽ 0.003).
y Surgeons belonging to the group of
Identified Surgeons’ Belief Classes
42%
times more likely to routinely use navigation compared with neurological or trauma spine surgeons (95% confidence interval (CI) 0.39 – 0.90; P ⫽ 0.015).
strong/very strong believers in the current benefit of navigation were 2.5 times more likely to use this technique routinely compared with other surgeons (95% CI 1.6 –3.9; P ⬍ 0.001).
DISCUSSION This survey addressed spine surgeons from five geographic regions with highly diverse cultural and professional backgrounds, training levels, and attitudes toward navigation. It is surprising that despite the widespread availability of CAS systems and training courses in NA, EU, and AP, the
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Table 3. Distribution of Surgeons According to Their Belief Classes and Clinical Profile in Relation to Spine Fusions and ComputerAssisted Surgery Surgeons’ Belief in Navigation
SPINE
1
2
3
4
Poor
Moderate
Strong
Very Strong
n Number of surgeons
%
114
n
%
248
n
%
110
N
%
102
Region North America
19
17
33
13
4
4
3
3
Latin America
22
19
39
16
23
21
41
41
Europe
46
40
103
42
45
41
26
26
Middle East
9
8
21
8
5
5
10
10
Asia Pacific
19
17
52
21
34
31
21
21
Neurosurgical
29
25
83
33
33
30
29
28
Orthopedic
77
68
149
60
63
57
66
65
8
7
16
6
14
13
7
7
44
38
82
33
39
35
51
50
Type of spine surgeon
Trauma Number of fusions per year 0–50 51–100
30
26
80
32
46
41
27
27
101–200
23
20
61
25
18
16
17
17
⬎ 200
18
16
25
10
9
8
6
6
Percentage surgery performed with MIS ⬍ 10%
83
72
164
66
78
70
76
75
10%-25%
19
17
48
19
23
21
14
14
26%-50%
5
4
21
8
7
6
5
5
⬎ 50%
8
7
16
6
4
4
6
6
Yes
47
41
105
42
53
48
26
25
No
68
59
144
58
57
52
76
75
CAN available?
Participated in course? Yes
37
32
88
35
45
40
39
38
No
78
68
162
65
67
60
63
62
6
5
17
7
22
20
13
13
Routine use of CAN Yes, routinely No, only in selected cases
26
23
72
29
26
23
19
19
Never
82
72
161
64
64
57
70
69
MIS, minimal invasive surgery; CAN, computer-assisted navigation.
number of routine users, as well as its popularity as gauged by the belief classes, is relatively low. Our survey data indicate that CAS is currently used primarily by expert surgeons
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with a higher volume of fusion surgery. The initial assumption that CAS would become a tool for less experienced surgeons to facilitate complex procedures is not supported by our results. This coincides with the find-
ing that CAS is thought of as providing the greatest benefit in more complex surgeries, such as MIS fusions, revision cases, deformity surgery and thoracic fusions; these procedures are most likely performed by
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Never or Only for Selected Cases, n (%)
Routinely, n (%)
Relative Risk (95% CI)
P Value
Neurosurgical/trauma
230 (38)
35 (60)
1
—
Orthopedic
378 (62)
23 (40)
0.59 (0.39–0.90)
Influencing Factor Type of spine surgeon
0.015
Percentage of fusions performed minimally invasive ⬍10%
61 (28)
188 (85)
1
160 (72)
33 (15)
1.70 (1.10–2.50)
No
382 (68)
4 (7)
1
—
Yes
183 (32)
54 (93)
13.9 (5.00–38.40)
⬍ 0.001 —
10%–100%
— 0.019
CAN capabilities for spinal surgery available at your hospital
Participated in a course on CAN No
382 (68)
4 (7)
1
Yes
183 (32)
54 (93)
2.2 (1.30–3.60)
Poor/moderate
342 (66)
23 (40)
1
—
Strong/very strong
179 (34)
35 (60)
2.50 (1.60–3.90)
⬍ 0.001
0.003
Surgeons’ belief about the benefit of navigation*
95% CI, 95% confidence interval; CAN, computer-assisted navigation. *Surgeons’ belief based on the Latent Class Analysis groups.
more specialized surgeons with high output.
Four Classes of Surgeons Based on Their Beliefs Regarding CAS Based on the four classes of surgeons categorized with poor, moderate, strongly positive, and very strongly positive opinions about CAS, there was interestingly no strong relationship between surgeon opinion on CAS and actual experience in its use. For example, we observed a large proportion of strong believers from LA where CAS equipment is scarcely available. This suggests that most surgeons see a role and need for CAS regardless of their previous experience. Furthermore, the moderate proportions of surgeons with a poor opinion in combination with access and training to use CAS found from our data demonstrate that actual experience with CAS can have negative effects on physician attitudes.
Why Do Surgeons Not Use CAS (more frequently)? Spinal navigation currently requires a significant investment into capital equipment. The lack of navigation systems, the high associ-
ated costs, and the lack of specific training in navigation clearly are important factors in support for CAS not being used, especially in resource-poorer regions of the world. The survey showed that the presence of CAS equipment and participation in training was clearly associated with increased use of CAS. The most common concern with CAS, however, is the perceived increase in OR time regardless of the level of exposure to CAS. The results from the survey, as well as the open comments to the survey, clearly demonstrate that surgeons are frustrated with the increase in time and the disruption of surgical work flow associated with the use of current CAS systems. In addition, surgeons ask for valid scientific data supporting the benefit of CAS in terms of precision, radiation exposure, and cost-effectiveness. Studies have shown that CAS can be used without significant increase in OR time and sometimes even with shorter operating times when compared with conventional surgery (17). Nevertheless, this depends on the level of experience and integration of CAS into the work flow. Training courses in CAS should focus not only on technical details of the procedure but also on how to best integrate CAS into the existing work flow in the OR. The
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learning curve associated with CAS must be considered not only for the individual surgeon but also the OR team as a whole.
Limitations First, a closed-ended survey with predesigned answer options may fail to capture the variety of opinions prevalent among surgeons. Open comments, however, were possible at the end of the survey and carefully reviewed. This analysis showed that the survey had captured all relevant opinions without missing important points. Second, surgeon responses depended on the correct understanding of the term CAS. It is possible, for example, that surgeons who indicated they had access to CAS but did not use it were referring to CAS for cerebral or orthopedic procedures, or to incomplete systems considered unsuitable for use in spine surgery. Third, surgeon experience may be biased due to initial negative experiences with first generation CAS systems. The quality of navigation hardware and software as well as imaging technologies has evolved, and it is possible that many surgeons would have responded differently if they had the latest technology available (e.g., intraoperative computed tomography scanner). This possibility
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Table 4. Multivariable Analysis of Factors Influencing the Routine Use of Navigation
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was also mentioned by several surgeons in the open comments at the end of the survey. Fourth, although AOSpine is the largest global spine care community, we realize that not every spine surgeon is a member and therefore did not have the opportunity to participate in the survey. Last, the response rate was 20% and we cannot exclude the possibility that surgeons with a particularly strong opinion for or against CAS may have been more likely to respond. Overall, we appreciate that this survey and previously published, mostly retrospective case series (1, 2, 7, 12, 16, 18, 19) are not substitutes for a large prospective trial, which would be necessary to assess the potential clinical benefit of CAS in spinal surgery.
NAVIGATION IN SPINE SURGERY
CONCLUSIONS These data send strong messages to the spine surgeon community and their industrial partners. 1. Surgeons generally see value in CAS and almost80%holdpositiveopinionsaboutCAS. 2. Current CAS systems do not meet surgeons’ expectations in terms of time efficiency, ease of use, and integration into the surgical work flow. 3. CAS systems have to be affordable and cost efficient to increase their availability. 4. Training has to be more readily available to overcome the demanding learning curve for CAS. This training should not only address individual surgeons but
ideally should also include the surgical team to improve integration of CAS into the existing work flow. 5. Valid scientific data are needed to clarify the precision of CAS, radiation exposure levels, and cost-effectiveness. This will require well-designed, prospective clinical trials.
ACKNOWLEDGMENTS The authors thank AOSpine for their assistance with the handling of the questionnaire, its distribution, and final data collection and Melissa Wilhelmi, Ph.D., for the preparation and copy-editing of this manuscript.
Appendix: 1. The 12-Item Questionnaire Sent Out to Aospine Members 1. Are you a(n):
7. Have you participated in a course on computer-assisted navigation?
a) orthopedic surgeon
a) yes
b) neurosurgical spine surgeon
b) no
c) trauma spine surgeon 2. Where is your hospital/practice located? Please state country
8a. Do you routinely use computer-assisted navigation for spinal fusion procedures? a) yes b) never c) no, only in selected cases
3. How many spinal fusions do you do per year?
8b. If yes, how many percent of all cases?
a) 0–50
a) ⬍10%
b) 51–100
b) 10%–25%
c) 101–200
c) 26%–50%
d) ⬎200
d) ⬎50%
4. In percent, how many of these fusions do you perform minimally invasive? a) ⬍10% b) 10%–25% c) 26%–50% d) ⬎50%
9. In your view, what are the current benefits of computer-assisted navigation? Please rate the level of benefit for each answer option provided below using the following ordered scale: “great benefit,” “some benefit,” “no benefit,” “undecided,” “possibly in the future/needs improvement” a) speed
5. Do you routinely use 2D fluoroscopy (AP/Lat) for your spinal surgeries? a) yes
b) accuracy c) makes complex surgeries safer
b) no
d) preoperative planning
c) only as a control at the end of the procedure
e) less radiation
d) only in selected cases; please specify
f) avoids wrong level surgery
6. Do you have computer-assisted navigation capabilities for spinal surgery available at your hospital?
g) enables less invasive surgery h) other benefits you consider important; please specify
a) yes b) no
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12. In your opinion, where would computer-assisted navigation have the most important benefit? Please rate the level of importance for each answer option provided below using the following ordered scale: “most important,” “important,” “neutral,” “not important,” “not applicable”
a) it is not available
a) simple intraoperative planning (e.g., screw trajectories)
b) I am not trained/my staff is not trained
b) dedicated preoperative planning (e.g., cages, AD, 3D, recons)
c) it disturbs the work flow in the operating room (OR)
c) instruments and implant integration
d) increase of OR time
d) minimally invasive surgery
e) it does not reduce radiation exposure
e) deformity surgery
f) it is not accurate enough
f) revision cases
g) it is expensive
g) simple decompression cases
h) the reimbursement has not been figured out properly
h) artificial disc surgery
i) it has no proven benefit
i) pain treatment
j) other factors you consider important; please specify
j) vertebral augmentation procedures
11. What are the most important requirements computer-assisted navigation would have to fulfill for you to use it? Please rate the level of importance for each answer option provided below using the following ordered scale: “most important,” “important,” “neutral,” “not important,” “not applicable”
k) correct operative level confirmation l) cervical surgery m) thoracic n) lumbar
a) save time in OR
o) sacral spine/iliac crest
b) be cost effective/save costs
p) other factors you consider important; please specify
c) be more precise
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10. Why do you NOT use computer-assisted navigation (. . . more often/always)? Please rate the level of importance for each answer option provided below using the following ordered scale: “most important,” “important,” “neutral,” “not important,” “not applicable”
13. Comments
d) availability of scientific data/evidence supporting its use e) I would use it but it is not available in my hospital f) decrease the exposure of radiation g) clarification of reimbursement issues h) I would use it if training would be available for me/my staff i) hospital policy change j) avoid wrong level surgery k) other factors you consider important; please specify
REFERENCES 1. Assaker R, Reyns N, Vinchon M, Demondion X, Louis E: Transpedicular screw placement: imageguided versus lateral-view fluoroscopy: in vitro simulation. Spine (Phila Pa 1976) 26:2160-2164, 2001.
2. Austin MS, Vaccaro AR, Brislin B, Nachwalter R, Hilibrand AS, Albert TJ: Image-guided spine surgery: a cadaver study comparing conventional open laminoforaminotomy and two image-guided techniques for pedicle screw placement in posterolateral fusion and nonfusion models. Spine (Phila Pa 1976) 27:2503-2508, 2002.
3. Berlemann U, Monin D, Arm E, Nolte LP, Ozdoba C: Planning and insertion of pedicle screws with computer assistance. J Spinal Disord 10:117-124, 1997.
4. Cummings P: Methods for estimating adjusted risk ratios. Stata J 9:175-196, 2009. 5. Davne SH, Myers DL: Complications of lumbar spinal fusion with transpedicular instrumentation. Spine (Phila Pa 1976) 17(6 Suppl):S184-S189, 1992. 6. Foley KT, Smith MM: Image-guided spine surgery. Neurosurg Clin N Am 7:171-186, 1996.
9. Kalfas IH, Kormos DW, Murphy MA, McKenzie RL, Barnett GH, Bell GR, Steiner CP, Trimble MB, Weisenberger JP: Application of frameless stereotaxy to pedicle screw fixation of the spine. J Neurosurg 83:641-647, 1995. 10. Laine T, Schlenzka D, Mäkitalo K, Tallroth K, Nolte LP, Visarius H: Improved accuracy of pedicle screw insertion with computer-assisted surgery. A prospective clinical trial of 30 patients. Spine (Phila Pa 1976) 22:1254-1258, 1997.
7. Fraser J, Gebhard H, Irie D, Parikh K, Härtl R: IsoC/3-dimensional neuronavigation versus conventional fluoroscopy for minimally invasive pedicle screw placement in lumbar fusion. Minim Invasive Neurosurg 53:184-190, 2010.
11. Langoltz F, Nolte LP: Computer-assisted surgery. In: Aebi M, Arlet V, Webb JK, eds: AOSpine Manual, Principles and Techniques. Vol. 1. New York: Thieme; 2007:571-587.
8. Hagenaars JA, McCutcheon AL: Applied Latent Class Analysis. Cambridge, UK: Cambridge University Press; 2002.
12. Laufer I, Greenfield JP, Anand VK, Härtl R, Schwartz TH: Endonasal endoscopic resection of the odontoid process in a nonachondroplastic dwarf with
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juvenile rheumatoid arthritis: feasibility of the approach and utility of the intraoperative Iso-C three-dimensional navigation. Case report. J Neurosurg Spine 8:376-380, 2008.
16. Nottmeier EW, Seemer W, Young PM: Placement of thoracolumbar pedicle screws using three-dimensional image guidance: experience in a large patient cohort. J Neurosurg Spine 10:33-39, 2009.
13. Merloz P, Tonetti J, Pittet L, Coulomb M, Lavalleé S, Sautot P: Pedicle screw placement using image guided techniques. Clin Orthop Relat Res 354:39-48, 1998.
17. Rajasekaran S, Vidyadhara S, Ramesh P, Shetty AP: Randomized clinical study to compare the accuracy of navigated and non-navigated thoracic pedicle screws in deformity correction surgeries. Spine (Phila Pa 1976) 32:E56-E64, 2007.
14. Nolte LP, Zamorano L, Arm E, Visarius H, Jiang Z, Berlemann U, Schwarzenbach O: Image-guided computer-assisted spine surgery: a pilot study on pedicle screw fixation. Stereotact Funct Neurosurg 66:108-117, 1996.
15. Nolte LP, Zamorano L, Visarius H, Berlemann U, LanglotzF,ArmE,SchwarzenbachO:Clinicalevaluationofa system for precision enhancement in spine surgery. Clin Biomech (Bristol, Avon) 10:293-303, 1995.
18. Sagi HC, Manos R, Benz R, Ordway NR, Connolly PJ: Electromagnetic field-based image guided spine surgery part one: results of a cadaveric study evaluating lumbar pedicle screw placement. Spine (Phila Pa 1976) 28:2013-2018, 2003. 19. Sagi HC, Manos R, Park SC, Von Jako R, Ordway NR, Connolly PJ: Electromagnetic field-based imageguided spine surgery part two: results of a cadaveric
study evaluating thoracic pedicle screw placement. Spine (Phila Pa 1976) 28:E351-E354, 2003. 20. Schwarzenbach O, Berlemann U, Jost B, Visarius H, Arm E, Langlotz F, Nolte LP, Ozdoba C: Accuracy of computer-assisted pedicle screw placement. An in vivo computed tomography analysis. Spine (Phila Pa 1976) 22:452-458, 1997.
Conflict of interest statement: Dr. Härtl is a consultant for Brainlab. Received 08 November 2011; accepted 28 March 2012 Citation: World Neurosurg. (2013) 79, 1:162-172. http://dx.doi.org/10.1016/j.wneu.2012.03.011 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter © 2013 Elsevier Inc. All rights reserved.
Spinous Process Morphometry for Interspinous Device Implantation in Korean Patients Eun Hyun Ihm1, In Bo Han 2, Dong Ah Shin 2, Tae Gon Kim 2, Ryoong Huh 2, Sang Sup Chung 2
Key words 䡲 Interspinous implant 䡲 Lumbar vertebrae 䡲 Morphometry 䡲 Spine 䡲 Spinous process 䡲 Spinal stenosis Abbreviations and Acronyms PACS: Picture archiving and communication system From the 1Department of Neurosurgery, Yonsei University, Seoul; and 2Department of Neurosurgery, CHA University, Pochon, Republic of Korea To whom correspondence should be addressed: Dong Ah Shin, M.D. [E-mail: [email protected]] Citation: World Neurosurg. (2013) 79, 1:172-176. DOI: 10.1016/j.wneu.2011.04.027 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter © 2013 Elsevier Inc. All rights reserved.
INTRODUCTION Lumbar spinal stenosis is a medical condition in which the spinal canal or neural foramen narrows and compresses the spinal cord or nerve roots (11, 36). This condition occurs as a result of age-related spinal degeneration, particularly in the intervertebral disc and ligamentum flavum (11, 36). Until more recently, surgical decompression was the treatment of choice after failure of conservative treatment
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䡲 OBJECTIVE: To analyze the interspinous distance and the height, length, and thickness of the lumbar spinous process for interspinous device implantation in Korean patients. 䡲 METHODS: Morphometric data obtained from plain radiographs of the lumbar and sacral spine were analyzed. The study included 60 matched subjects who visited an outpatient clinic for back pain. Exclusion criteria included collapsed intervertebral disc, lumbarization, and sacralization. There were 34 men and 26 women; age range was the 20s to 70s, with 10 subjects in each decade. The interspinous distance and height, length, and thickness of the lumbar spinous process were obtained on lateral radiographs using an image analysis program (M-view 5.4; Marotech). 䡲 RESULTS: The largest interspinous distance was at L2-3, with a mean of 12 mm (range 6–22 mm), and the smallest distance was at L5-S1, with a mean of 8 mm (range 3–16 mm). The interspinous distance became shorter from L1-2 to L5-S1. A negative correlation was noted between age and interspinous distance in the L1-5 levels (L1-2, y ⴝ ⴚ0.11x ⴙ 17.27, r 2 ⴝ 0.34, P < 0.0001; L2-3, y ⴝ ⴚ0.07x ⴙ 15.68, r 2 ⴝ 0.12, P ⴝ 0.0058; L3-4, y ⴝ ⴚ0.08x ⴙ 14.39, r 2 ⴝ 0.27, P < 0.0001; L4-5, y ⴝ ⴚ0.05x ⴙ 11.65,r 2 ⴝ 0.096, P ⴝ 0.0158; L5-S1, y ⴝ ⴚ0.02x ⴙ 9.25, r 2 ⴝ 0.028, P ⴝ 0.1982). 䡲 CONCLUSIONS: There is a decreasing trend in the interspinous distance in the L1-5 levels with advancing years. Taking progressive collapse of the interspinous distance with the aging process into consideration, interspinous implants should be carefully selected in younger patients.
(11, 36). Although laminectomy without fusion may be less invasive, wide decompression may cause secondary instability and back
pain (16, 28). Instrumented fusion can provide immediate stability even after total removal of bilateral facet joints. However, rigid
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Worldwide Survey on the Use of Navigation in Spine Surgery Roger Härtl1, Khai Sing Lam 2, Jeffrey Wang 3, Andreas Korge 4, Frank Kandziora5, Laurent Audigé6
SPINE Key words 䡲 Expert opinion 䡲 Internet-based opinion survey 䡲 Spine surgery 䡲 Surgery, computer-assisted Abbreviations and Acronyms AP: Asia Pacific CAS: Computer-assisted surgery CI: Confidence interval EU: Europe LA: Latin America ME: Middle East (including Africa) MIS: Minimally invasive spinal surgery NA: North America OR: Operating room From the 1 Brain and Spine Center, Weill Cornell Medical College, New York, 2 New York, USA; London Spine Center, Guy’s and St. Thomas’ NHS Foundation Hospitals, London, United Kingdom; 3UCLA Comprehensive Spine Center, Santa Monica, California, USA; 4Schön Klinik München Harlaching, Munich, Germany; 5BG Trauma Clinic Frankfurt am Main, Center for Spinal Surgery and Neurotraumatology, Frankfurt, Germany; and 6AO Clinical Investigation and Documentation, AO Foundation, Duebendorf, Switzerland To whom correspondence should be addressed: Roger Härtl, M.D. [E-mail: [email protected]] Citation: World Neurosurg. (2013) 79, 1:162-172. http://dx.doi.org/10.1016/j.wneu.2012.03.011
䡲 OBJECTIVE: Computer-assisted surgery (CAS) can improve the accuracy of screw placement and decrease radiation exposure, yet this is not widely accepted among spine surgeons. The current viewpoint of spine surgeons on navigation in their everyday practice is an important issue that has not been studied. A survey-based study assessed opinions on CAS to describe the current global attitudes of surgeons on the use of navigation in spine surgery. 䡲 METHODS: A 12-item questionnaire focusing on the number and type of surgical cases, the type of equipment available, and general opinions toward CAS was distributed to 3348 AOSpine surgeons (a specialty group within the AO [Arbeitsgemeinschaft für Osteosynthesefragen] Foundation). Latent class analysis was used to investigate the existence of specific groups based on the respondent opinion profiles. 䡲 RESULTS: A response rate of 20% was recorded. Despite a widespread distribution of navigation systems in North America and Europe, only 11% of surgeons use it routinely. High-volume procedure surgeons, neurological surgeons, and surgeons with a busy minimal invasive surgery practice are more likely to use CAS. “Routine users” consider the accuracy, potential of facilitating complex surgery, and reduction in radiation exposure as the main advantages. The lack of equipment, inadequate training, and high costs are the main reasons that “nonusers” do not use CAS. 䡲 CONCLUSIONS: Spine surgeons acknowledge the value of CAS, yet current systems do not meet their expectations in terms of ease of use and integration into the surgical work flow. To increase its use, CAS has to become more cost efficient and scientific data are needed to clarify its potential benefits.
Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter © 2013 Elsevier Inc. All rights reserved.
INTRODUCTION Spine surgery inherently carries the potential of injury to the spinal cord, nerves, and important vascular structures. Incorrectly positioned implants and screws, which significantly breach the pedicle, can cause spinal, nerve root, or vascular injury, as well as dural tears and cerebrospinal fluid leaks (5, 17). Intuitively, it makes sense that implants placed with greater accuracy are preferred. There is general agreement among surgeons that imaging techniques are essential for safe and accurate placement of spinal instrumentation regardless of the complexity of the operation, the anatomic region,
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and the level of training and comfort level of the individual surgeon. Traditionally, this has involved the use of radiograph or image intensification guidance, either as a control at the end of a procedure or for active guidance throughout surgery. More recently, stereotactic two- or threedimensional imaging techniques have been developed and gained acceptance in disciplines such as cranial neurosurgery and certain orthopedic trauma procedures. The use of stereotactic computer-assisted surgery (CAS) was first described for spinal instrumentation placement in the mid-1990s (6, 9, 14, 15) and the different types of CAS have been reviewed (11). Computer three-dimensional navigation techniques in spinal instrumentation can improve screw place-
ment accuracy, potentiate the ability to maximize the screw diameter relative to the pedicle, and reduce potential injury to critical neurovascular structures (1, 2, 7, 12, 16, 18, 19). Despite further reports suggesting that CAS can improve accuracy of screw placement and decrease radiation exposure (3, 10, 13–15, 17, 20), it has not been generally accepted among spine surgeons and there is no clinical evidence that CAS in spinal surgery leads to improved patient outcomes. The reasons for this lack of acceptance are probably complex and may involve factors related to availability, training, individual experience and preference, and cost-effectiveness, among others. A better understanding of these reasons is essential in determining the
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current deficits of navigation and how these can be addressed. The present study was conducted to evaluate the current attitudes toward spine navigation, the perceived problems, and further issues that could potentially be addressed to increase acceptance of navigation among international orthopedic, trauma, and neurological spine surgeons.
MATERIALS AND METHODS A 12-item questionnaire was developed to assess the experiences of AOSpine surgeons with computer navigation and their current attitudes toward its use in spine surgery (Appendix 1). (AOSpine [a speciality within the AO Foundation] is an international community of spine surgeons, orthopedic surgeons, neurosurgeons, academics, researchers, and other spine care professionals dedicated to delivering knowledge, experience,
and evidence to improve patient care and outcomes. The AO Foundation is a medically guided, non-profit organization led by an international group of surgeons specialized in the treatment of trauma and disorders of the musculoskeletal system.) The questionnaire contained three parts: (1) demographics (i.e., region, subspecialty) and basic information regarding the number and type of surgical cases performed; (2) targeted information about the type of navigation equipment available to the surgeon, their level of training, and the number of cases performed with or without navigation; and (3) general opinions toward navigation and its potential benefits. All questions were closed-ended with predesigned answer options from which the respondent could choose one answer. In May 2009, the Web-based questionnaire was distributed to 3348 members of AOSpine Asia Pacific (AP), Europe (EU), Latin America (LA), Middle East (including Africa) (ME) and North America (NA) by
means of an invitation e-mail. This e-mail contained a link directing the respondents to SurveyMonkey where the questionnaire could be completed online. A reminder email was sent out to members who had not initially responded, and the Web site was closed in August 2009.
Statistical Analysis Survey data were formatted and analyzed using Intercooled Stata Version 11 (StataCorp LP; College Point, Texas, USA). Categorical variables were described using absolute and relative frequencies and responses to questions 1–8 were stratified by region and type of surgeon.
Latent Class Analysis and Surgeons’ Opinion Profile on Navigation Survey participants provided their views using rating scales concerning seven claimed benefits of computer-assisted navigation (question 9) including: (1) speed, (2) accuracy, (3)
Figure 1. Distribution of the survey respondents based on their geographic region and surgeon subspecialty.
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Table 1. Summary of the Survey Responses to Questions 1– 8 Number of Responses
%
Asia Pacific (n ⫽ 822)
139
17
Europe (n ⫽ 1086)
252
23
Latin America (n ⫽ 660)
145
22
Middle East (n ⫽ 272)
52
19
North America (n ⫽ 508)
60
12
139
21
Europe
252
39
Latin America
145
22
Middle East
52
8
North America
60
9
Not known
29
Region (response rate)*
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Regional distribution of respondents Asia Pacific
Spine surgeon Neurological spine surgeon
210
32
Orthopedic surgeon
401
60
Trauma spine surgeon
55
8
Not known
11
Number of fusions per year 0–50
249
39
51–100
193
30
101–200
127
20
⬎200
69
11
Not known
39
Percentage of fusions performed with MIS ⬍10%
441
70
10%–25%
113
18
26%–50%
43
7
⬎50%
37
6
Not known
43
CAN available? Yes
237
38
No
386
62
Not known
54
Participated in a CAN course? Yes
217
35
No
408
65
Not known
52
makes complex surgeries safer, (4) preoperative planning, (5) less radiation, (6) avoids wrong level surgery, and (7) enables less invasive surgery. To investigate the existence of groups of surgeons sharing similar opinion profiles, we applied the technique of latent class modeling (8) using the software Latent Gold Version 4.0.3 (Statistical Corporation; Belmont, Massachusetts, USA). Latent class modeling is a technique based on the principle that surgeons truly belong to distinguishable opinion groups (e.g., those strongly believing in the benefit of navigation vs. those not believing in its benefit) that cannot be directly observed (hence the term latent), but are only indirectly documented using the sevenanswer item set. The analysis aims at identifying the most probable opinion groups for further investigation on the relationship between having a specific opinion profile and the use of navigation.
Factors Influencing the Use (or nonuse) of Navigation in Spine Fusion We investigated factors (independent variables) influencing the routine use of navigation (yes) versus never (no) (dichotomous-dependent variables). These factors included the surgeon’s profile; the annual number of spine fusions performed; the percentage of fusions performed using a minimal invasive technique; the availability of computer-assisted navigation for spine surgery at the respondent’s hospital; previous participation in a course on computer-assisted navigation; and the surgeon’s belief about the benefit of navigation (i.e., opinion groups). This analysis was exploratory. In multivariable logistic regression analyses, factors that were not significant at the 0.05 level were excluded manually from the model in a backward procedure. A final multivariable binomial regression model was fitted to derive adjusted relative risks (4).
RESULTS
Routine use of CAN for spinal fusions Yes, routinely
58
9
No, only in selected cases
151
25
Never
411
66
Not known MIS, minimal invasive surgery; CAN, computer-assisted navigation. *Based on total number of AOSpine members invited to respond.
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Respondent Demographics (questions 1– 8) Surgeon Characteristics. From a total of 3348 spine surgeons, 677 surgeons (20%) submitted complete or incomplete responses. The majority of the respondents were from EU, LA, and AP (39%, 22%, and 21%, respectively) (Figure 1 and Table 1). Only 60
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use fluoroscopy. Similar proportions of orthopedic (73%) and neurological (87%) surgeons use fluoroscopy. However, more orthopedists (18%) use this guidance technique only as a control at the end of the procedure than their neurosurgeon colleagues (4%).
Figure 2. Proportion of spine fusions performed annually.
respondents were from NA (9%) and most (60%) were orthopedic spine surgeons. Number of Fusions per Year. Half (50%) of the responding surgeons perform between 51 and 200 spinal fusions per year, with only 11% performing more than 200 procedures yearly (Table 1). NA respondents perform the highest proportion of spinal fusions with 50% undertaking more than 100 fusions per year (Figure 2). The lowest number of fusions is performed in LA, where the majority (84%) of respondents perform less than 100 procedures annually. There was no significant difference between the numbers of fusions (⬎100) performed per year for neurological (27%) and orthopedic (32%) surgeons.
Minimally Invasive Spinal Surgery. The majority (70%) of surgeons use minimally invasive spinal surgery (MIS) for less than 10% of the total fusion procedures performed (Table 1). The highest proportion of MIS fusions is performed in NA and EU where 18%–20% of surgeons use this technique for more than 25% of their spinal fusions (Figure 3). Neurological (9%) and trauma (8%) surgeons use MIS fusion techniques more frequently (i.e., ⬎50% of all fusions performed) than orthopedists (4%). Use of Regular Anteroposterior/Lateral Fluoroscopy. Seventy-eight percent of the surgeons use routine fluoroscopy during spine surgery. Interestingly, almost 9% of all respondents and 21% of the NA surgeons do not
Figure 3. Proportion of fusions performed annually using minimal invasive surgery.
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Availability, Training Level, and Use of Spinal Navigation. Overall, 38% of the surgeons indicated that they have access to computerassisted navigation facilities (Table 1). Seventy percent of NA surgeons have CAS available at their hospitals compared with about 42% in EU and AP, and only 14% in LA (Figure 4). Neurological (45%) and trauma (47%) surgeons had slightly more access to CAS compared with orthopedists (33%). Thirty-five percent of the surgeon population has participated in a CAS training course (Table 1). Surgeons from NA have the greatest exposure to training courses (57%) compared with those from other regions (27%–36%). Trauma surgeons have participated in training courses most frequently (50%), followed by neurological (39%) and orthopedic surgeons (31%). Based on question 8a, surgeons were divided into “nonusers,” “routine users,” and “selective users.” Overall, 66% of surgeons never use CAS (nonusers) for spinal fusion surgery, 9% are routine users, and the remaining (25%) are selective users (Table 1). In NA, more than half of the surgeons (52%) use CAS routinely or in selected cases (Figure 5). More than 40% for both the neurological and trauma surgeon groups use CAS routinely or in selected cases compared with only 28% orthopedic surgeons. Within the group of 58 routine CAS users comprising 26 neurological, 23 orthopedic, and 9 trauma surgeons, 10% use CAS in 26%– 50% of their spinal fusion cases and 53% use it in more than 50% of cases. Surgeons with a higher volume of spinal fusions per year use CAS more than surgeons doing less fusion surgery (Figure 6). Up to 59% of surgeons doing more than 200 spinal fusions per year use spinal navigation routinely or in selected cases compared with only 21% of surgeons performing less than 50 fusions yearly.
Attitudes Toward Navigation (questions 9 –12) Perceived Benefits of CAS. Various factors considered as benefits of CAS by more than
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75% of the survey population included its accuracy, the potential of rendering complex surgery safer, and the possible reduction of radiation. The use of CAS in MIS, for preoperative planning, and the avoidance of wrong level surgery were also considered beneficial for 60%–70% of the respondents. However, about 60% indicated that CAS did not provide any benefit in terms of operative speed. The routine users of CAS (n ⫽ 58) pointed out the same advantages but believed more strongly about the benefits of its accuracy, the potential of making complex surgery safer, and the possible reduction of radiation exposure (i.e., ⬎90% assigned great or some benefit to CAS in making complex surgery safer and more ac-
curate). Almost 50% agreed that speed was not a benefit or that it needed improvement. The majority of respondents who were nonusers (n ⫽ 411) had a less well-defined understanding of the potential benefits of CAS. Between 65% and 83% indicated great or some benefit for all answer options except for speed. Reasons for Not Using CAS. High costs, the lack of CAS equipment, increase in operating room (OR) time, and no or inadequate training were quoted as the important/most important reasons for not using CAS at all or more often by 52%–73% of all surgeons. The lack of proven benefit, disturbance of the OR work flow, and concerns about accuracy were believed to be less important.
Figure 5. Routine use of computer-assisted navigation for spine fusion surgery.
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For the routine users, almost 80% indicated the increased OR time associated with CAS as the main reason for not using it more frequently. Problems with the OR work flow and cost reimbursements were only believed to be important/most important by less than 50% of these surgeons. The lack of proven benefit was the least important concern. Similar responses were documented by the selective users of CAS (n ⫽ 151). Of the nonusers, 80% indicated a lack of equipment and high costs as the important/ most important reasons for not using CAS, followed by 62% quoting inadequate training, and 50%–55% rating the increase in OR time and lack of reimbursement as important/most important reasons for not using CAS. Requirements for CAS to be Used More. All respondents indicated that more data supporting the precision (88%), reduced radiation exposure, and cost-effectiveness of CAS (both 79%), as well as more scientific evidence supporting its use (75%) and a positive impact on operative times (74%) are important/most important factors required to convince them to use it at all or more frequently. Data supporting better precision and reduced radiation exposure (both 87%) were important/most important factors, followed by the ability of CAS to save time in the OR (68%) for the routine users. Cost-effectiveness, scientific evidence supporting its use, clarification of reimbursement issues, and the avoidance of wrong level surgery were also quoted by 50%– 65% of this group as important/ most important factors. In addition to data on precision, costeffectiveness, radiation exposure, and operative times (73%– 88%), 73% of the 411 nonusers indicated that they would use CAS if it was available at their hospital and 65% indicated they would use it if training was available. Greatest Potential Benefit of CAS. More than 75% of all surgeons considered MIS, revision cases, deformity surgery, and thoracic spine surgery as areas that would most likely benefit from CAS. Surgery of the cervical spine and preoperative/intraoperative planning for instrumentation were also considered important areas for CAS by most surgeons. In contrast, less than 50% of the survey population considered simple
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NA (Fisher’s exact test; P ⬍ 0.001), but did not belong to a particular surgeon type (P ⫽ 0.38). Only 25% and 48% of the surgeons with very strong and strong expectations, respectively, have CAS available at their institution compared with 41% of those with poor views on navigation (Table 3). Even 5% of the routine users have poor beliefs and surgeons with a high volume of fusions (26%) were less likely to be strong believers in CAS. Factors Influencing the Routine Use of Navigation. The final multivariable binomial model outlined in Table 4 included the following factors:
Figure 6. Comparison of the routine use of computer-assisted navigation with the proportion of fusions performed annually.
decompression surgery, disc arthroplasty, pain treatment, vertebral augmentation procedures, and intraoperative confirmation of the correct level as relatively unimportant areas for CAS. Respondent Opinion Profiles and Demographics. Latent class analysis of the opinion ratings identified four classes of surgeons according to their belief on the current benefit of navigation. The classes are described by the mean scale responses for each of the seven rating scales (Table 2). One class included 22% of all surgeons with poor opinion about the benefit of navigation with mean scale responses ranging
y Orthopedic spine surgeons were 0.6
from 1.67–2.95. Forty-two percent showed a more positive view of navigation with mean scale responses higher by almost one point on each scale, in particular for “accuracy” and “makes complex surgeries safer.” The last two respondent classes demonstrated strong to very strong views about the benefit of navigation with mean scores ranging from 2.54 for “speed” to more than 4.80 for other items. Each respondent was allocated to one of these four belief classes according to their response profile (Table 3). The distribution of the classes per region and type of surgeon showed that more very strong believers of navigation originated from LA than EU and
Table 2. Mean Response Data for the Surgeon Classes Characterized by Their Belief on the Current Benefit of Navigation in Spine Fusion
1
2
3
4
Potential benefits
Poor
Moderate
Strong
Very Strong
Class size (n ⫽ 574)
22%
19%
18%
Speed
1.67
1.98
2.54
3.96
Accuracy
2.71
4.14*
4.98*
4.89*
Makes complex surgeries safer
2.53
4.24*
4.91*
4.90*
Preoperative planning
2.66
3.62
3.54
4.82*
Less radiation
2.95
3.95
4.17*
4.90*
Avoids wrong level surgery
2.44
3.20
3.44
4.88*
Enables less invasive surgery
2.70
3.67
3.97
4.89*
*These numbers represent the mean scale responses of ⬎4.00 –5.00.
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y Surgeons performing ⱖ10% of their fusions with MIS were 1.7 times more likely to routinely use navigation compared with those performing less than 10% (95% CI 1.1–2.5; P ⫽ 0.019).
y When computer-assisted navigation for spinal surgery was available at the surgeon’s hospital, he or she was 14 times more likely to use it routinely (95% CI 5.0 –38.4; P ⬍ 0.001).
y Surgeons who participated in a course on computer-assisted navigation were 2.2 times more likely to use navigation routinely compared with those who did not (95% CI 1.3–3.6; P ⫽ 0.003).
y Surgeons belonging to the group of
Identified Surgeons’ Belief Classes
42%
times more likely to routinely use navigation compared with neurological or trauma spine surgeons (95% confidence interval (CI) 0.39 – 0.90; P ⫽ 0.015).
strong/very strong believers in the current benefit of navigation were 2.5 times more likely to use this technique routinely compared with other surgeons (95% CI 1.6 –3.9; P ⬍ 0.001).
DISCUSSION This survey addressed spine surgeons from five geographic regions with highly diverse cultural and professional backgrounds, training levels, and attitudes toward navigation. It is surprising that despite the widespread availability of CAS systems and training courses in NA, EU, and AP, the
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Table 3. Distribution of Surgeons According to Their Belief Classes and Clinical Profile in Relation to Spine Fusions and ComputerAssisted Surgery Surgeons’ Belief in Navigation
SPINE
1
2
3
4
Poor
Moderate
Strong
Very Strong
n Number of surgeons
%
114
n
%
248
n
%
110
N
%
102
Region North America
19
17
33
13
4
4
3
3
Latin America
22
19
39
16
23
21
41
41
Europe
46
40
103
42
45
41
26
26
Middle East
9
8
21
8
5
5
10
10
Asia Pacific
19
17
52
21
34
31
21
21
Neurosurgical
29
25
83
33
33
30
29
28
Orthopedic
77
68
149
60
63
57
66
65
8
7
16
6
14
13
7
7
44
38
82
33
39
35
51
50
Type of spine surgeon
Trauma Number of fusions per year 0–50 51–100
30
26
80
32
46
41
27
27
101–200
23
20
61
25
18
16
17
17
⬎ 200
18
16
25
10
9
8
6
6
Percentage surgery performed with MIS ⬍ 10%
83
72
164
66
78
70
76
75
10%-25%
19
17
48
19
23
21
14
14
26%-50%
5
4
21
8
7
6
5
5
⬎ 50%
8
7
16
6
4
4
6
6
Yes
47
41
105
42
53
48
26
25
No
68
59
144
58
57
52
76
75
CAN available?
Participated in course? Yes
37
32
88
35
45
40
39
38
No
78
68
162
65
67
60
63
62
6
5
17
7
22
20
13
13
Routine use of CAN Yes, routinely No, only in selected cases
26
23
72
29
26
23
19
19
Never
82
72
161
64
64
57
70
69
MIS, minimal invasive surgery; CAN, computer-assisted navigation.
number of routine users, as well as its popularity as gauged by the belief classes, is relatively low. Our survey data indicate that CAS is currently used primarily by expert surgeons
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with a higher volume of fusion surgery. The initial assumption that CAS would become a tool for less experienced surgeons to facilitate complex procedures is not supported by our results. This coincides with the find-
ing that CAS is thought of as providing the greatest benefit in more complex surgeries, such as MIS fusions, revision cases, deformity surgery and thoracic fusions; these procedures are most likely performed by
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Never or Only for Selected Cases, n (%)
Routinely, n (%)
Relative Risk (95% CI)
P Value
Neurosurgical/trauma
230 (38)
35 (60)
1
—
Orthopedic
378 (62)
23 (40)
0.59 (0.39–0.90)
Influencing Factor Type of spine surgeon
0.015
Percentage of fusions performed minimally invasive ⬍10%
61 (28)
188 (85)
1
160 (72)
33 (15)
1.70 (1.10–2.50)
No
382 (68)
4 (7)
1
—
Yes
183 (32)
54 (93)
13.9 (5.00–38.40)
⬍ 0.001 —
10%–100%
— 0.019
CAN capabilities for spinal surgery available at your hospital
Participated in a course on CAN No
382 (68)
4 (7)
1
Yes
183 (32)
54 (93)
2.2 (1.30–3.60)
Poor/moderate
342 (66)
23 (40)
1
—
Strong/very strong
179 (34)
35 (60)
2.50 (1.60–3.90)
⬍ 0.001
0.003
Surgeons’ belief about the benefit of navigation*
95% CI, 95% confidence interval; CAN, computer-assisted navigation. *Surgeons’ belief based on the Latent Class Analysis groups.
more specialized surgeons with high output.
Four Classes of Surgeons Based on Their Beliefs Regarding CAS Based on the four classes of surgeons categorized with poor, moderate, strongly positive, and very strongly positive opinions about CAS, there was interestingly no strong relationship between surgeon opinion on CAS and actual experience in its use. For example, we observed a large proportion of strong believers from LA where CAS equipment is scarcely available. This suggests that most surgeons see a role and need for CAS regardless of their previous experience. Furthermore, the moderate proportions of surgeons with a poor opinion in combination with access and training to use CAS found from our data demonstrate that actual experience with CAS can have negative effects on physician attitudes.
Why Do Surgeons Not Use CAS (more frequently)? Spinal navigation currently requires a significant investment into capital equipment. The lack of navigation systems, the high associ-
ated costs, and the lack of specific training in navigation clearly are important factors in support for CAS not being used, especially in resource-poorer regions of the world. The survey showed that the presence of CAS equipment and participation in training was clearly associated with increased use of CAS. The most common concern with CAS, however, is the perceived increase in OR time regardless of the level of exposure to CAS. The results from the survey, as well as the open comments to the survey, clearly demonstrate that surgeons are frustrated with the increase in time and the disruption of surgical work flow associated with the use of current CAS systems. In addition, surgeons ask for valid scientific data supporting the benefit of CAS in terms of precision, radiation exposure, and cost-effectiveness. Studies have shown that CAS can be used without significant increase in OR time and sometimes even with shorter operating times when compared with conventional surgery (17). Nevertheless, this depends on the level of experience and integration of CAS into the work flow. Training courses in CAS should focus not only on technical details of the procedure but also on how to best integrate CAS into the existing work flow in the OR. The
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learning curve associated with CAS must be considered not only for the individual surgeon but also the OR team as a whole.
Limitations First, a closed-ended survey with predesigned answer options may fail to capture the variety of opinions prevalent among surgeons. Open comments, however, were possible at the end of the survey and carefully reviewed. This analysis showed that the survey had captured all relevant opinions without missing important points. Second, surgeon responses depended on the correct understanding of the term CAS. It is possible, for example, that surgeons who indicated they had access to CAS but did not use it were referring to CAS for cerebral or orthopedic procedures, or to incomplete systems considered unsuitable for use in spine surgery. Third, surgeon experience may be biased due to initial negative experiences with first generation CAS systems. The quality of navigation hardware and software as well as imaging technologies has evolved, and it is possible that many surgeons would have responded differently if they had the latest technology available (e.g., intraoperative computed tomography scanner). This possibility
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Table 4. Multivariable Analysis of Factors Influencing the Routine Use of Navigation
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was also mentioned by several surgeons in the open comments at the end of the survey. Fourth, although AOSpine is the largest global spine care community, we realize that not every spine surgeon is a member and therefore did not have the opportunity to participate in the survey. Last, the response rate was 20% and we cannot exclude the possibility that surgeons with a particularly strong opinion for or against CAS may have been more likely to respond. Overall, we appreciate that this survey and previously published, mostly retrospective case series (1, 2, 7, 12, 16, 18, 19) are not substitutes for a large prospective trial, which would be necessary to assess the potential clinical benefit of CAS in spinal surgery.
NAVIGATION IN SPINE SURGERY
CONCLUSIONS These data send strong messages to the spine surgeon community and their industrial partners. 1. Surgeons generally see value in CAS and almost80%holdpositiveopinionsaboutCAS. 2. Current CAS systems do not meet surgeons’ expectations in terms of time efficiency, ease of use, and integration into the surgical work flow. 3. CAS systems have to be affordable and cost efficient to increase their availability. 4. Training has to be more readily available to overcome the demanding learning curve for CAS. This training should not only address individual surgeons but
ideally should also include the surgical team to improve integration of CAS into the existing work flow. 5. Valid scientific data are needed to clarify the precision of CAS, radiation exposure levels, and cost-effectiveness. This will require well-designed, prospective clinical trials.
ACKNOWLEDGMENTS The authors thank AOSpine for their assistance with the handling of the questionnaire, its distribution, and final data collection and Melissa Wilhelmi, Ph.D., for the preparation and copy-editing of this manuscript.
Appendix: 1. The 12-Item Questionnaire Sent Out to Aospine Members 1. Are you a(n):
7. Have you participated in a course on computer-assisted navigation?
a) orthopedic surgeon
a) yes
b) neurosurgical spine surgeon
b) no
c) trauma spine surgeon 2. Where is your hospital/practice located? Please state country
8a. Do you routinely use computer-assisted navigation for spinal fusion procedures? a) yes b) never c) no, only in selected cases
3. How many spinal fusions do you do per year?
8b. If yes, how many percent of all cases?
a) 0–50
a) ⬍10%
b) 51–100
b) 10%–25%
c) 101–200
c) 26%–50%
d) ⬎200
d) ⬎50%
4. In percent, how many of these fusions do you perform minimally invasive? a) ⬍10% b) 10%–25% c) 26%–50% d) ⬎50%
9. In your view, what are the current benefits of computer-assisted navigation? Please rate the level of benefit for each answer option provided below using the following ordered scale: “great benefit,” “some benefit,” “no benefit,” “undecided,” “possibly in the future/needs improvement” a) speed
5. Do you routinely use 2D fluoroscopy (AP/Lat) for your spinal surgeries? a) yes
b) accuracy c) makes complex surgeries safer
b) no
d) preoperative planning
c) only as a control at the end of the procedure
e) less radiation
d) only in selected cases; please specify
f) avoids wrong level surgery
6. Do you have computer-assisted navigation capabilities for spinal surgery available at your hospital?
g) enables less invasive surgery h) other benefits you consider important; please specify
a) yes b) no
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12. In your opinion, where would computer-assisted navigation have the most important benefit? Please rate the level of importance for each answer option provided below using the following ordered scale: “most important,” “important,” “neutral,” “not important,” “not applicable”
a) it is not available
a) simple intraoperative planning (e.g., screw trajectories)
b) I am not trained/my staff is not trained
b) dedicated preoperative planning (e.g., cages, AD, 3D, recons)
c) it disturbs the work flow in the operating room (OR)
c) instruments and implant integration
d) increase of OR time
d) minimally invasive surgery
e) it does not reduce radiation exposure
e) deformity surgery
f) it is not accurate enough
f) revision cases
g) it is expensive
g) simple decompression cases
h) the reimbursement has not been figured out properly
h) artificial disc surgery
i) it has no proven benefit
i) pain treatment
j) other factors you consider important; please specify
j) vertebral augmentation procedures
11. What are the most important requirements computer-assisted navigation would have to fulfill for you to use it? Please rate the level of importance for each answer option provided below using the following ordered scale: “most important,” “important,” “neutral,” “not important,” “not applicable”
k) correct operative level confirmation l) cervical surgery m) thoracic n) lumbar
a) save time in OR
o) sacral spine/iliac crest
b) be cost effective/save costs
p) other factors you consider important; please specify
c) be more precise
SPINE
10. Why do you NOT use computer-assisted navigation (. . . more often/always)? Please rate the level of importance for each answer option provided below using the following ordered scale: “most important,” “important,” “neutral,” “not important,” “not applicable”
13. Comments
d) availability of scientific data/evidence supporting its use e) I would use it but it is not available in my hospital f) decrease the exposure of radiation g) clarification of reimbursement issues h) I would use it if training would be available for me/my staff i) hospital policy change j) avoid wrong level surgery k) other factors you consider important; please specify
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9. Kalfas IH, Kormos DW, Murphy MA, McKenzie RL, Barnett GH, Bell GR, Steiner CP, Trimble MB, Weisenberger JP: Application of frameless stereotaxy to pedicle screw fixation of the spine. J Neurosurg 83:641-647, 1995. 10. Laine T, Schlenzka D, Mäkitalo K, Tallroth K, Nolte LP, Visarius H: Improved accuracy of pedicle screw insertion with computer-assisted surgery. A prospective clinical trial of 30 patients. Spine (Phila Pa 1976) 22:1254-1258, 1997.
7. Fraser J, Gebhard H, Irie D, Parikh K, Härtl R: IsoC/3-dimensional neuronavigation versus conventional fluoroscopy for minimally invasive pedicle screw placement in lumbar fusion. Minim Invasive Neurosurg 53:184-190, 2010.
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8. Hagenaars JA, McCutcheon AL: Applied Latent Class Analysis. Cambridge, UK: Cambridge University Press; 2002.
12. Laufer I, Greenfield JP, Anand VK, Härtl R, Schwartz TH: Endonasal endoscopic resection of the odontoid process in a nonachondroplastic dwarf with
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13. Merloz P, Tonetti J, Pittet L, Coulomb M, Lavalleé S, Sautot P: Pedicle screw placement using image guided techniques. Clin Orthop Relat Res 354:39-48, 1998.
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study evaluating thoracic pedicle screw placement. Spine (Phila Pa 1976) 28:E351-E354, 2003. 20. Schwarzenbach O, Berlemann U, Jost B, Visarius H, Arm E, Langlotz F, Nolte LP, Ozdoba C: Accuracy of computer-assisted pedicle screw placement. An in vivo computed tomography analysis. Spine (Phila Pa 1976) 22:452-458, 1997.
Conflict of interest statement: Dr. Härtl is a consultant for Brainlab. Received 08 November 2011; accepted 28 March 2012 Citation: World Neurosurg. (2013) 79, 1:162-172. http://dx.doi.org/10.1016/j.wneu.2012.03.011 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter © 2013 Elsevier Inc. All rights reserved.
Spinous Process Morphometry for Interspinous Device Implantation in Korean Patients Eun Hyun Ihm1, In Bo Han 2, Dong Ah Shin 2, Tae Gon Kim 2, Ryoong Huh 2, Sang Sup Chung 2
Key words 䡲 Interspinous implant 䡲 Lumbar vertebrae 䡲 Morphometry 䡲 Spine 䡲 Spinous process 䡲 Spinal stenosis Abbreviations and Acronyms PACS: Picture archiving and communication system From the 1Department of Neurosurgery, Yonsei University, Seoul; and 2Department of Neurosurgery, CHA University, Pochon, Republic of Korea To whom correspondence should be addressed: Dong Ah Shin, M.D. [E-mail: [email protected]] Citation: World Neurosurg. (2013) 79, 1:172-176. DOI: 10.1016/j.wneu.2011.04.027 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter © 2013 Elsevier Inc. All rights reserved.
INTRODUCTION Lumbar spinal stenosis is a medical condition in which the spinal canal or neural foramen narrows and compresses the spinal cord or nerve roots (11, 36). This condition occurs as a result of age-related spinal degeneration, particularly in the intervertebral disc and ligamentum flavum (11, 36). Until more recently, surgical decompression was the treatment of choice after failure of conservative treatment
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䡲 OBJECTIVE: To analyze the interspinous distance and the height, length, and thickness of the lumbar spinous process for interspinous device implantation in Korean patients. 䡲 METHODS: Morphometric data obtained from plain radiographs of the lumbar and sacral spine were analyzed. The study included 60 matched subjects who visited an outpatient clinic for back pain. Exclusion criteria included collapsed intervertebral disc, lumbarization, and sacralization. There were 34 men and 26 women; age range was the 20s to 70s, with 10 subjects in each decade. The interspinous distance and height, length, and thickness of the lumbar spinous process were obtained on lateral radiographs using an image analysis program (M-view 5.4; Marotech). 䡲 RESULTS: The largest interspinous distance was at L2-3, with a mean of 12 mm (range 6–22 mm), and the smallest distance was at L5-S1, with a mean of 8 mm (range 3–16 mm). The interspinous distance became shorter from L1-2 to L5-S1. A negative correlation was noted between age and interspinous distance in the L1-5 levels (L1-2, y ⴝ ⴚ0.11x ⴙ 17.27, r 2 ⴝ 0.34, P < 0.0001; L2-3, y ⴝ ⴚ0.07x ⴙ 15.68, r 2 ⴝ 0.12, P ⴝ 0.0058; L3-4, y ⴝ ⴚ0.08x ⴙ 14.39, r 2 ⴝ 0.27, P < 0.0001; L4-5, y ⴝ ⴚ0.05x ⴙ 11.65,r 2 ⴝ 0.096, P ⴝ 0.0158; L5-S1, y ⴝ ⴚ0.02x ⴙ 9.25, r 2 ⴝ 0.028, P ⴝ 0.1982). 䡲 CONCLUSIONS: There is a decreasing trend in the interspinous distance in the L1-5 levels with advancing years. Taking progressive collapse of the interspinous distance with the aging process into consideration, interspinous implants should be carefully selected in younger patients.
(11, 36). Although laminectomy without fusion may be less invasive, wide decompression may cause secondary instability and back
pain (16, 28). Instrumented fusion can provide immediate stability even after total removal of bilateral facet joints. However, rigid
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