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Part VII
Future Directions
Clinical Research in MIS Surgery: Current State and Future Challenges
Christina L. Goldstein and Y. Raja Rampersaud
3 6
36.1 Introduction
Spinal fusion is an accepted method of treatment
for a wide variety of spinal pathologies requiring stabilization, including spinal deformity.
Unfortunately, traditional open techniques are
associated with extensive soft tissue dissection
and retraction required to identify anatomic landmarks for appropriate placement of instrumentation and adequate preparation of the fusion bed.
The morbidity associated with these open surgical exposures may include substantial blood loss
[ 1 ], high complication rates [ 2 ], prolonged hos-
pital stays [ 3 ], increased postoperative low back
pain, and decreased trunk muscle strength [ 4 ].
The demonstration of improved outcomes and
decreased morbidity associated with minimally
invasive techniques in other surgical specialties
[ 5 – 8 ], coupled with technical advances in magni-
fi cation, illumination and access, and surgical
instrumentation, has led to a desire to apply MIS
C. L. Goldstein , M.D., FRCSC
Toronto Western Hospital Spine Program,
Division of Neurosurgery , Toronto Western Hospital,
University of Toronto , 399 Bathurst Street,
WW 4-418 , Toronto , ON M5T 2S8 , Canada
e-mail: drcgoldstein@gmail.com
Y. R. Rampersaud , M.D., FRCSC (*)
Krembil Neuroscience – Spine Program,
Division of Orthopaedics , Toronto Western Hospital,
University of Toronto, University Health Network ,
399 Bathurst Street, EW 1-441 , Toronto , ON
M5T 2S8 , Canada
e-mail: raja.rampersaud@uhn.ca
techniques to spinal fusion surgery. However,
before widespread adoption of these techniques
can occur, the safety and effi cacy of MIS spine
surgery compared to currently accepted and commonly used techniques for open spinal fusion
must be examined. In addition, with the higher
up-front costs typically associated with new
surgical technology, the decision to adopt MIS
techniques must include a consideration of
cost-effectiveness.
Using the current evidence pertaining to posterior MIS lumbar spine fusion as an example,
this chapter aims to outline the current state of
the literature regarding MIS fusion surgery, identify shortcomings of the evidence to date, and
suggest possible directions and challenges to be
addressed as future research is undertaken.
36.2 Current State of the
Literature: Comparative
Effectiveness Research
Prior to adoption of a novel surgical technique,
its relative worth, utility, and importance must be
compared to standard interventions. This need
has been highlighted by the Institute of Medicine
(IOM) and is addressed through the completion
of comparative effectiveness research (CER).
As per the IOM, “comparative effectiveness
research is the generation and synthesis of
evidence that compares the benefi ts and harms of
alternative methods to prevent, diagnose, treat,
and monitor or improve the delivery of care.
M.Y. Wang et al. (eds.), Minimally Invasive Spinal Deformity Surgery,
DOI 10.1007/978-3-7091-1407-0_36, © Springer-Verlag Wien 2014
371
372
C.L. Goldstein and Y.R. Rampersaud
The purpose of CER is to assist consumers,
clinicians, purchasers, and policy makers to make
informed decisions that will improve health care
at both the individual and population levels” [ 9 ].
Surgeons have traditionally understood CER
to mean the demonstration of equivalent or superior safety and effi cacy of one intervention compared to another. According to this basic
understanding of CER, MIS fusion techniques
must be shown to be at least as safe and effective
as traditional open methods of spinal fusion.
Thus, until recently, the evidence in support of
new MIS fusion procedures, conducted primarily
by surgeons, has been limited to case series,
cohort studies, comparative observational studies, and, rarely, randomized controlled trials,
examining outcomes such as surgical time, blood
loss, length of stay, complication rate, and fusion
rate [ 10 ].
36.3 Comparative Effectiveness
of MIS Lumbar Fusion
The number of studies comparing open to MIS
posterior lumbar fusion techniques for degenerative conditions has increased signifi cantly in
recent years. These studies examine techniques
such as direct lateral or extreme lateral interbody
fusion (DLIF/XLIF), axial lumbar interbody
fusion (AxiaLIF), and MIS anterior lumbar interbody fusion (ALIF). A detailed account of the
current evidence pertaining to all these techniques is beyond the scope of this chapter. We
will instead focus on comparative effectiveness
research comparing posterior MIS lumbar fusion
to traditional midline open posterior spinal fusion
for degenerative lumbar conditions. For a summary of the indications and outcomes of the lateral transpsoas approach, we would direct the
reader to an excellent review recently published
by Arnold et al. [ 11 ].
We have recently completed a systematic
review of the literature to determine the comparative effectiveness of MIS versus open posterior
fusion for degenerative lumbar conditions
(Goldstein and Rampersaud – 2012, submitted
for peer review). Medline, EMBASE, Web of
Science, and Cochrane databases were queried.
The MeSH terms used were derivatives of
“Minimally invasive”/“Minimal access” and
“Lumbar spine”/“Lumbar vertebrae” or
“Fusion”/“Surgical Procedures.” PubMed was
searched using the phrase “Minimally invasive
spine surgery,” and a hand search of reference
lists was also performed. Article titles, abstracts,
and full-text versions were reviewed by two independent assessors to identify randomized controlled trials or comparative cohort studies
including ten or more patients in each group
undergoing open or MIS fusion for degenerative
pathology and reporting at least one of (1) clinical outcome measure, (2) perioperative outcome
measure, (3) radiographic outcome, (4) complications, or (5) economic analysis. Study quality
was assessed using the GRADE protocol [ 12 ]. In
cases of disagreement, a third surgeon was
involved to assess suitability for study inclusion
and GRADE rating. A meta-analysis was conducted on outcomes data when appropriate.
We identifi ed 25 comparative cohort studies
[ 13 – 37 ] and one prospective randomized trial
[ 38 ] meeting our inclusion criteria. According to
the GRADE protocol, all studies were rated as
low or very low quality due to multiple factors
including but not limited to, patient and surgical
heterogeneity, small sample size, methodological
fl aws, and/or small treatment effect size. In these
26 studies, 856 patients with a mean age of 54.9
years underwent MIS lumbar fusion and 806
patients with a mean age of 56.7 years underwent
traditional open instrumented fusion. The indications for surgery among the studies were mixed;
in the 14 studies reporting on preoperative diagnosis, more than half of the patients underwent
surgery for degenerative or isthmic spondylolisthesis with the remainder suffering from spinal
stenosis, degenerative disc disease, or other spinal pathology.
36.3.1 Perioperative
Outcome Measures
As demonstrated in Table 36.1 , except for radia-
tion exposure, meta-analysis of perioperative
36 Clinical Research in MIS Surgery: Current State and Future Challenges
Table 36.1 Meta-analysis of results for perioperative outcome measures comparing MIS vs. open TLIF
Mean difference (MIS – open fusion)
Outcome
Operative time [minutes] 15 1,016 −2.49 [−19.66, 14.68] 0.78
Length of stay [days] 13 891 −2.87 [−3.82, −1.91] < 0.0001
Estimated blood loss [mL] 17 1,091 −260.11 [−332.69, −187.54] < 0.0001
X-ray time [s] 6 481 55.93 [36.12, 75.75] < 0.0001
Time to ambulation [days] 4 330 −3.52 [−5.52, −1.51] 0.0006
No. of studies No. of patients
[95 % CI]
p -value
373
outcome measures favors MIS fusion compared
to open surgery. No signifi cant difference was
observed in operative time between the open and
MIS cohorts, though as expected an MIS
approach exposed patients to an average of 56
more seconds of intraoperative radiation (95 %
confi dence interval (CI) 36.12–75.75, p < 0.0001).
In the 17 studies reporting on intraoperative
blood loss, patients undergoing MIS fusion lost
on average 260 mL less blood (95 % CI 187.54–
332.69, p < 0.0001). Patients undergoing MIS
fusion were also able to ambulate an average of
3.5 days faster than patients in the open cohort
(95 % CI 1.51–5.52, p = 0.0006) and were dis-
charged a mean of 2.9 days sooner (95 % CI
1.91–3.82, p < 0.0001).
These results are similar to those demon-
strated in a previous literature review by Karikari
et al. [ 10 ] including seven comparative cohort
studies examining MIS versus open TLIF or
PLIF. As in our review, all comparative studies
reviewed ( n = 7) demonstrated that the MIS
subgroup performed better than the open group
with regard to estimated blood loss and length of
stay. No signifi cant difference was observed in
operative time in these seven studies (MIS
156.2–348.2 min; open 142.8–312.2 min).
36.3.2 Complication Rates
Demonstration of safety of new surgical techniques
is also required prior to widespread implementation of MIS techniques for lumbar spine fusion.
Complications of spinal fusion have been shown to
be more common in the elderly and patients with
multiple comorbidities [ 39 ]. This is particularly
relevant as the percentage of people over the age of
65 increases and the number of patients suffering
from degenerative spinal conditions grows. Thus, a
comparative effectiveness study of MIS vs. open
spinal fusion would not be complete without an
analysis of complication rates.
In 2010 Wu et al. performed a review of the
literature and meta-analysis of fusion rates
reported in cohort and comparative studies,
including a single RCT, examining open and/or
MIS TLIF [ 40 ]. Open TLIF was performed on
716 patients in 16 studies and 312 patients underwent MIS TLIF in 8 studies. Among these
patients no signifi cant difference in fusion rates
was observed (open: 90.9 % [95 % CI: 86.4–
94.0 %]; MIS: 94.8 % [95 %CI: 85.4–98.3 %]).
The authors also noted a trend towards lower
complication rates in the MIS cohort (7.5 %
[95 % CI: 3.0–17.3 %]) compared to the open
cohort (12.6 % [95 % CI: 7.5–20.3 %]). It should
be noted, however, that there was signifi cant variability in the method of reporting and defi ning
what was a complication and that a signifi cantly
higher percentage of patients in the MIS cohort
underwent fusion with BMP (50 % vs. 12.2 % in
the open cohort).
In a more recent publication, Parker et al.
performed a systematic review of the literature
to identify studies in which rates of surgical site
infections (SSIs) were reported to examine the
difference between open and MIS TLIF [ 41 ].
The authors identifi ed 10 MIS studies and 20
open studies enrolling 362 and 1,133 patients,
respectively. Pooled analysis from these 30
studies demonstrated a signifi cantly lower rate
of SSI in the MIS cohort at 0.6 % compared to
4.0 % in the open cohort ( p = 0.0005).
In our systematic review of the literature, 23
of the 26 studies reported on at least one type of
374
C.L. Goldstein and Y.R. Rampersaud
Table 36.2
Meta-analysis
of complications
rates comparing
MIS vs. open TLIF
Outcome
Dural tear 16 1,009 0.71 [0.39, 1.30] 0.27
Infection 13 852 0.66 [0.32, 1.36] 0.26
Surgical complications 15 991 0.72 [0.42, 1.21] 0.21
Medical complications 13 854 0.39 [0.23, 0.69] 0.001
Nonunion 8 455 0.97 [0.35, 2.63] 0.95
Reoperation 9 640 0.99 [0.40, 2.44] 0.97
All complications 23 1,420 0.63 [0.47, 0.85] 0.002
No. of studies No. of patients Risk ratio [95 % CI]
complication including nonunion, with the
meta- analysis of complication rates summarized
in Table 36.2 . As per Wu et al. [ 40 ], no signifi cant
difference was found in fusion rates between the
open and MIS cohorts in the eight studies in
which union was addressed (RR = 0.97 [95 % CI
0.35–2.63]; p = 0.95). Unlike the fi ndings of
Parker et al. [ 41 ], our meta-analysis failed to
identify a difference in deep and superfi cial infection rates between the two surgical treatment
groups (RR = 0.66 [95 % CI = 0.32–1.36];
p = 0.26). However, this difference is possibly
due to variation in defi nitions of surgical site
infection as well as the exclusion of studies without a comparative cohort from our systematic
review. Further analysis revealed no difference in
surgical complication rates between open and
MIS lumbar fusion, including dural tear, implant
malposition, neurologic injury, or postoperative
hematoma (RR = 0.72 [95 % CI 0.42–1.21],
p = 021). However, signifi cantly more patients
undergoing open surgery suffered from a medical
complication including urinary tract infections,
respiratory complications, and cardiac complications (RR = 0.39 [95 % CI 0.23–0.69], p = 0.001).
Transfusion rates were also signifi cantly higher
in open fusion patients (RR = 031 [95 %
CI = 0.10–0.93], p = 0.04).
Although there is currently no comparative
literature meeting our inclusion criteria regarding complications or outcomes following MIS
versus open treatment of multilevel coronal
plane deformity, this growing area warrants specifi c mention. The prevalence of spinal deformity in patients over the age of 60 is almost
70 % [ 42 ] with up to 50 % of patients hospital-
ized with a primary diagnosis of spinal deformity being 65 years of age or older [ 43 ]. Given
the increased burden of comorbid disease in this
p- value
patient population and the association between
preoperative pulmonary, renal, and cardiac testing and perioperative complications involving
these organ systems [ 44 ], increased application
of MIS techniques to adult deformity surgery has
the potential to translate into signifi cant improvement in clinical outcomes in this patient population. Published case series would suggest that
other than specifi c complications associated
with a transpsoas approach, MIS techniques
result in an overall reduction in other (i.e., medical) complications [ 11 ]. Furthermore, with an
estimated cost of $10,000 USD per in-hospital
complication experienced by a spine patient
[ 39 ], the economic impact of decreased compli-
cation rates with MIS surgery would be
substantial.
36.3.3 Patient-Reported Outcome Measures
While perioperative outcome measures and complication rates are an important component of
determining safety and effi cacy of a new surgical
technique, these outcomes tend to have greater
meaning for surgeons than patients and thus may
not accurately refl ect comparative effectiveness
from the patient’s perspective. Instead, administration of patient-centered outcome measures
including parameters most important to the
patient (e.g., pain, function, return to work) is an
important way of documenting the comparative
effectiveness of different treatment strategies for
spinal conditions.
The most common patient-reported outcome
measures used in the study of lumbar disorders
are the Oswestry Disability Index (ODI), the
Medical Outcomes Study 36-item Short-Form
36 Clinical Research in MIS Surgery: Current State and Future Challenges
375
General Health Survey (SF-36), and the EuroQoL
(EQ)-5D. Of the 26 studies identifi ed in our
systematic review, 22 included at least 1 patientreported outcome with 10 employing the ODI
[ 13 , 16 , 22 – 24 , 27 , 28 , 34 – 36 ], 3 utilizing the
SF-36 [ 17 , 22 , 31 ], and only a single study
administering the EQ-5D [ 13 ]. Other patient-
reported outcome measures identifi ed in our
review included a Visual Analogue Scale pain
score for back or leg pain, the McGill pain score,
perceived stress and profi le of mood, the Japanese
Orthopaedic Association (JOA) score, the
Roland-Morris Disability Questionnaire (RMQ),
the North American Spine Society score, the
AAOS score, Short-Form 12 (SF-12), and the
Prolo Scale.
Details of the results of the patient-reported
outcome measures utilized in the 22 studies identifi ed in our systematic review are outlined in
Table 36.3 . Meta-analysis of patient-reported
outcome results was limited to change in ODI
score due to the small number of studies utilizing
the other outcome measures (Fig. 36.1 ). Pooled
analysis of the change in ODI comparing MIS to
open fusion from ten studies resulted in a statistically signifi cant mean difference favoring MIS
surgery (MD = 3.32 [95 % CI 1.33–5.32],
p = 0.001). However, this observed difference
between the groups does not approach the minimal clinically important difference or threshold
for substantial clinical benefi t for the ODI [ 45 ].
Thus, the results from this limited pooled analysis as well as those demonstrated in Table 36.2
qualitatively demonstrate clinical equivalence
between MIS and open fusion for degenerative
lumbar conditions at up to 2 years or more of
follow-up with no study reporting inferior clinical results in an MIS cohort.
36.4 Shortcomings of the Current
Comparative Effectiveness
Literature
While current comparative effectiveness research
for MIS vs. open lumbar fusion suggests compelling evidence for the clinical equivalence of the
two techniques, limitations in study design
prevent strong recommendations from being
made based on these studies. As stated earlier,
only one prospective randomized controlled trial
exists comparing single-level open vs. MIS lumbar fusion in patients with a mixture of lumbar
degenerative disorders [ 38 ]. At a minimum fol-
low- up time of 2 years, clinical equivalence in
patient-reported outcomes (ODI and VAS) was
observed. However, no signifi cant difference in
intraoperative estimated blood loss or length of
stay was seen between the cohorts, likely due to
the study being underpowered with only 79
patients enrolled (MIS n = 41, open n = 38).
Further design limitations including failure to
mention allocation concealment, the number of
patients screened, and lack of blinding of outcome assessors led to a downgrading of this RCT
from an initial GRADE level of evidence rating
of high to one of low. Similarly, the remaining
prospective and retrospective cohort studies
identifi ed in our systematic review were graded
as low or very low quality.
The heterogeneity of diagnoses included in
most of the current studies comparing open and
MIS lumbar fusion also impacts pooled analysis
of results. As opposed to degenerative or isthmic
spondylolisthesis, specifi c criteria by which
patients are diagnosed with degenerative disc
disease or discogenic back pain do not exist. As a
result, heterogeneous populations of patients are
lumped together for the purpose of assessing
treatment effects, with the resultant outcomes
providing little insight into the effi cacy of the
treatment for specifi c spinal pathologies. As has
been previously demonstrated, clinical outcome
of lumbar fusion is dependent on primary diagnosis, with improved 2-year changes in healthrelated quality of life seen in patients with a
diagnosis of spondylolisthesis or scoliosis compared to disc pathology, stenosis, or postdiscectomy revision [ 46 ]. Thus, the clinical
equivalence observed in our systematic review
between MIS and open fusion for lumbar degenerative disorders may be a result of heterogeneity
of diagnoses rather than a true lack of superiority
of MIS fusion.
Finally, a lack of clear defi nitions of adverse
events and absence of standardized methods of
376
Follow-up period
6–12 weeks 6 months 1 year ≥ 2 years
C.L. Goldstein and Y.R. Rampersaud
Outcome Outcome Outcome Outcome
Table 36.3 Summary of results of patient-reported outcomes in comparative studies of MIS vs. open fusion
Study (origin)
Diagnosis Outcome measure
25 ] (Korea) Mixed VAS back MIS MIS
Park and Ha [
Prolo scale Equivalent
28 ] (Switzerland) Mixed RMQ MIS MIS
Scheuffl er et al. [
AAOS score MIS MIS
Perceived stress MIS
31 ] (USA) Instability McGill pain score MIS
15 ] (USA) Mixed Modifi ed Prolo scale Equivalent
Starkweather et al. [
Dhall et al. 2008 [
Profi le of mood MIS
VAS Equivalent Equivalent
NASS score Equivalent Equivalent
SF-36 MIS
spondylolisthesis
53 ] (Singapore) Degenerative
Peng et al. [
ODI Equivalent Equivalent
ODI Equivalent
30 ] (Switzerland) Mixed VAS Equivalent
Schizas et al. [
JOA Equivalent Equivalent Equivalent
spondylolisthesis
32 ] (Japan) Degenerative
Tsutsumimoto et al. [
VAS leg Equivalent
ODI Equivalent Equivalent
17 ] (Australia) Isthmic or degenerative
16 ] (China) Mixed VAS back Equivalent Equivalent
Fan et al. [
Gahreman et al. [
VAS back Equivalent
spondylolisthesis (< 50 %
slip)
VAS MIS Equivalent Equivalent
ODI Equivalent Equivalent Equivalent
SF-36 Equivalent
24 ] (Germany) Degenerative
Ntoukas and Muller [
MacNab’s Criteria Equivalent
spondylolisthesis
33 ] (USA) Mixed VAS Equivalent
Villavicencio et al. [
ODI Equivalent
spondylolisthesis
34 ] (USA) Mixed Prolo scale MIS (1-level)
35 ] (China) Isthmic or degenerative
Wang Zhou et al. [
Wang, Cummock et al. [
36 Clinical Research in MIS Surgery: Current State and Future Challenges
377
VAS leg Equivalent
VAS back Equivalent
ODI Equivalent
EQ-5D Equivalent
spondylolisthesis
Adogwa et al. [ 13 ] (USA) Degenerative
VAS leg Equivalent Equivalent
ODI Equivalent Equivalent
ODI Equivalent Equivalent Equivalent Equivalent
spondylolisthesis
38 ] (China) Mixed VAS Equivalent Equivalent Equivalent Equivalent
18 ] (USA) Degenerative
Harris et al. [
Wang Lu et al. [
JOA MIS MIS MIS MIS
VAS leg Equivalent
36 ] (China) Mixed VAS back Equivalent
Wang Zhou et al. [
ODI MIS MIS MIS MIS
ODI Equivalent
spondylolisthesis
20 ] (Japan) Degenerative
Kotani et al. [
RMQ MIS
ODI MIS
spondylolisthesis
(<50 % slip)
28 ] (Canada) Isthmic or degenerative
22 ] (Singapore) Mixed VAS leg Equivalent Equivalent
Rampersaud et al. [
Lee et al. [
VAS back Equivalent Equivalent
SF-36 Equivalent Equivalent
ODI Equivalent Equivalent
NASS score Equivalent Equivalent
ODI Equivalent
SF-12 Equivalent
23 ] (Australia) Mixed VAS Open
Mobbs et al. [
26 ] (USA) Mixed VAS MIS
Pelton et al. [
VAS leg Equivalent
ODI Equivalent
37 ] (China) Mixed VAS back Equivalent
Wang Zhou et al. [
378
C.L. Goldstein and Y.R. Rampersaud
Study or subgroup
Adogwa 2011
Fan,Hu,zaho 2010
Lww2012
Mobbs 2012
Ntoukas 2010
Peng 2009
Rampersaud 2011
Wang,zhou 2010
Wang,zhou 2011
Wang,zhou 2012
Total (95 % CI) 346 346 100.0 % –3.32 [–5.32, –1.33]
Heterogeneity: Tau
Test for overall effect Z = 3.26 (P = 0.001)
MIS
Mean Mean
SD SD Total Weight IV,Random, 95 % CI IV,Random, 95 % CI
2.82
3.41
3.31
4.25
1.43
0.91
3.84
1.14
2.14
1.83
Total
15
28
72
36
20
29
37
42
25
42
–17.2
–48
–23.7
–24.29
–54
–30.2
–17.65
–26.4
–26.4
–22.8
3.85
3.38
2.88
4.46
1.5
0.92
3.85
1.28
1.77
1.01
15
31
72
29
20
29
41
43
27
30
9.1 %
9.7 %
10.2 %
9.4 %
10.3 %
10.5 %
9.8 %
10.2 %
10.2 %
10.3 %
–21.2
–58.5
–26.7
–31.59
–59
–29
–17.99
–30.4
–27.3
–22.9
2
= 9.87; Chi2 = 426.39, df = 9 (P<0.0000); I2 = 98 %
Mean difference Mean differenceOpen TLIF
–4.00 [–6.42, –1.58]
–10.50 [–12.24, –8.76]
–3.00 [–4.01, –1.99]
–7.30 [–9.44, –5.16]
–5.00 [–5.91, –4.09]
1.20 [0.73, 1.67]
–0.34 [–2.05, – 1.37]
–4.00 [–4.52, –3.48]
–0.90 [–1.97, 0.17]
–0.10 [–0.92, –0.72]
–20 –10
Favours MIS Favours open TLIF
01020
Fig. 36.1 Forest plot demonstrating pooled analysis of change in ODI in patients undergoing MIS vs. open TLIF
diagnosis impact the accuracy of the results
reported in the studies included in our systematic review. A recent report on the rigorous
prospective assessment of minor and major
adverse events in 942 patients undergoing major
spine surgery utilizing standardized defi nitions
and multiple data collection methods identifi ed
a complication rate of 87 %, including a 73.5 %
rate of postoperative complications [ 47 ]. This
rate is signifi cantly higher than the rate of 23 %
that was previously observed at the authors’
institution prior to implementation of the prospective reporting process and is also higher
than the complication rates identifi ed in our systematic review. Thus, the retrospective nature of
the majority of the studies comparing open to
MIS lumbar fusion may underestimate the difference in complication rates observed between
the cohorts and thus the benefi ts of MIS lumbar
fusion.
with no knowledge of the costs associated with
these techniques risks adopting an approach to
health service delivery that will quickly become
unsustainable.
In 2008 Martin et al. identifi ed that the $86
billion dollars spent annually in the USA to treat
back and neck problems had reached levels comparable to diabetes, cancer, and non-spine arthritis [ 48 ]. As the population continues to age, with
more than 50 % of US adults estimated to be over
the age of 65 by 2030 [ 49 ], spine surgeons can no
longer afford to view comparative effectiveness
research and health economic research as mutually exclusive. A comprehensive review of methods of health economic evaluation (HEE) is
outside the scope of this chapter; however a basic
understanding of HEE is required to understand
current HEE pertaining to MIS lumbar spine
fusion and appreciate the shortcomings of this literature and future challenges faced by spine
researchers.
Several types of HEE exist, though they are
36.5 Future Direction
of the Literature: CostEffectiveness Research
not interchangeable or of equal value when
applied to health care decision-making. In order
to balance the priorities of the “payer” as well
as the “patient,” a cost-effectiveness analysis
Despite the identifi ed limitations, current CER
literature suggests improved perioperative outcomes with equivalent 2-year clinical outcomes
comparing MIS and open fusion for the treatment
of degenerative lumbar conditions. However,
widespread adoption of MIS spinal fusion based
solely on procedural quality and health outcomes
(CEA), which simultaneously examines compar-
ative clinical effectiveness and the costs of alter-
native interventions, is the ideal method of HEE
[ 50 ]. The goal of a CEA is to measure the incre-
mental cost and effects resulting from choosing
one intervention over another [ 51 ]. The need to
conduct a CEA can be determined by the nature
36 Clinical Research in MIS Surgery: Current State and Future Challenges
379
Table 36.4 Approach to determination of the need for a
cost-effectiveness analysis (CEA)
Cost of new treatment
Higher Lower
Effectiveness
of new
treatment
More
effective
Less
effective
Perform CEA New
treatment is
superior
– ADOPT
New treatment
is inferior –
ABANDON
Perform CEA
of the relationship between cost and effectiveness
as illustrated in Table 36.4 .
In 1996 recommendations regarding the key
components of study design required for a highquality CEA were put forward [ 52 ]. First, the
CEA should be performed from the societal perspective, incorporating both direct (i.e., procedure and complication related) and indirect (i.e.,
loss of productivity of the patient or caregiver)
costs. Next, measurement of clinical utility
should be performed using validated general and
disease-specifi c health outcome measures. For
lumbar spine conditions, both the ODI and
EuroQoL-5D or SF-6D should be used [ 49 ].
Uncertainties in cost should also be
acknowledged with a sensitivity analysis, in
which statistical analysis is performed using
higher costs and decreased clinical benefi ts. The
CEA should also include discounting of costs
and benefi ts to account for the assumption that
patients place more value on money spent on
health care today than on that spent in the future.
Finally, an appropriate comparison group must
be included to allow for the proper incremental
comparisons to be made across treatment
strategies.
While a CEA informs decision-making
regarding alternative treatment options for a single condition (e.g., operative vs. nonoperative
treatment or open vs. MIS fusion for degenerative spondylolisthesis), the information obtained
cannot be used to aid payers and policy-makers
when comparing cost-effectiveness of interventions for competing pathologies (e.g., spinal
stenosis vs. hip arthritis) such that decisions
regarding health resource allocation can be made.
Determination of the relative value of treatment
of different conditions instead requires a different
type of HEE, a cost utility analysis (CUA) [ 53 ].
In a CUA a generic health utility score is used
to measure treatment outcomes in terms of a
universal unit, the quality-adjusted life-year
(QALY). A QALY is a generic measure of the
impact of disease on life refl ecting both the quality and quantity of life lived and is calculated by
multiplying the utility score of a treatment of
interest by the duration of treatment effect [ 45 ].
The utility score can be derived from a variety of
generic health-related quality of life measures,
including the SF-36, Health Utilities Index, and
EQ-5D, and is expressed as a value in the range
from 0 to 1 with 0 representing death and 1 representing a perfect health state [ 53 ]. Once the cost
of an intervention and its utility score are known,
the incremental cost utility ratio (ICUR), or cost
required to obtain one QALY, can be determined.
It is the ICUR that allows comparison of relative
value of treatment across disease states with values between $50 and $100 K USD being considered a reasonable cost for the utility gained [ 54 ].
36.6 Cost-Effectiveness of MIS
Lumbar Fusion
The increasing importance of value of treatment
options for spinal disorders has been demonstrated by the 70 % increase in articles related to
the lumbar spine including a CEA from 2004 to
2009 compared to 1999 to 2004 [ 45 ]. Despite
this, during the latter time period, less than 1 % of
articles published on the lumbar spine included a
CEA [ 45 ]. More recently, Kepler et al. performed
a systematic review of the Tufts Medical Center
Institute for Clinical Research and Health Policy
CEA Registry Database and the National Health
Service Economic Evaluation Database to identify studies related to the spine that included a
CUA [ 55 ]. Between 1976 and 2010, 33 studies
including a CUA were found with only 4 of the
articles (12 %) meeting all the key recommendations for performance of a high-quality CEA put
forward by the US Panel of Cost-Effectiveness in
Health and Medicine [ 52 ]. None of those four