Eur Spine J (2015) 24:1017–1030 DOI 10.1007/s00586-015-3903-4
REVIEW ARTICLE
Minimally invasive versus open transforaminal lumbar interbody fusion for treatment of degenerative lumbar disease: systematic review and meta-analysis Kevin Phan1,2 • Prashanth J. Rao1,2 • Andrew C. Kam2 • Ralph J. Mobbs1
Received: 22 January 2015 / Revised: 21 March 2015 / Accepted: 22 March 2015 / Published online: 27 March 2015 Ó Springer-Verlag Berlin Heidelberg 2015
Abstract Purpose While open TLIF (O-TLIF) remains the mainstay approach, minimally invasive TLIF (MI-TLIF) may offer potential advantages of reduced trauma to paraspinal muscles, minimized perioperative blood loss, quicker recovery and reduced risk of infection at surgical sites. This meta-analysis was conducted to provide an updated assessment of the relative benefits and risks of MI-TLIF versus O-TLIF. Methods Electronic searches were performed using six databases from their inception to December 2014. Relevant studies comparing MI-TLIF and O-TLIF were included. Data were extracted and analysed according to predefined clinical end points. Results There was no significant difference in operation time noted between MI-TLIF and O-TLIF cohorts. The median intraoperative blood loss for MI-TLIF was significantly lower than O-TLIF (median: 177 vs 461 mL; (weighted mean difference) WMD, -256.23; 95 % CI -351.35, -161.1; P \ 0.00001). Infection rates were significantly lower in the minimally invasive cohort (1.2 vs
Electronic supplementary material The online version of this article (doi:10.1007/s00586-015-3903-4) contains supplementary material, which is available to authorized users. & Kevin Phan [email protected] Ralph J. Mobbs [email protected] 1
Neurospine Clinic and Neurospine Surgery Research Group (NSURG), Prince of Wales Private Hospital, Randwick, Sydney, NSW 2031, Australia
2
Department of Neurosurgery, Westmead Hospital, Sydney, Australia
4.6 %; relative risk (RR), 0.27; 95 %, 0.14, 0.53; I2 = 0 %; P = 0.0001). VAS back pain scores were significantly lower in the MI-TLIF group compared to O-TLIF (WMD, -0.41; 95 % CI -0.76, -0.06; I2 = 96 %; P \ 0.00001). Postoperative ODI scores were also significantly lower in the minimally invasive cohort (WMD, -2.21; 95 % CI -4.26, -0.15; I2 = 93 %; P = 0.04). Conclusions In summary, the present systematic review and meta-analysis demonstrated that MI-TLIF appears to be a safe and efficacious approach compared to O-TLIF. MI-TLIF is associated with lower blood loss and infection rates in patients, albeit at the risk of higher radiation exposure for the surgical team. The long-term relative merits require further validation in prospective, randomized studies. Keywords Minimally invasive Transforaminal lumbar interbody fusion TLIF Lumbar Spine Degenerative
Introduction Degenerative spinal diseases are one of the most common comorbidities in elderly patients, leading to discogenic back pain and spinal instability [1, 2]. Transforaminal lumbar interbody fusion (TLIF) is one of the surgical options used for the stabilization and treatment of degenerative lumbar disease such as disc degeneration and spondylolisthesis which has failed conservative management. TLIF was initially developed as a modification of the posterior lumbar interbody fusion (PLIF) approach [3, 4], with added advantages of direct, unilateral access to the intervertebral foraminal area whilst reducing interruption to the spinal muscles and structural integrity [5–9]. While open TLIF (O-TLIF) is an established approach for
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1018
degenerative lumbar disease, there are still concerns surrounding the associated long hospital stays, excessive blood loss and postoperative complications associated with an open procedure [10–12]. The advent of minimally invasive procedures in the surgical realm led to the logical progression of O-TLIF to minimally invasive TLIF (MI-TLIF) over the past decade. MI-TLIF offers potential advantages of reduced trauma to paraspinal muscles, minimized perioperative blood loss, quicker recovery and reduced risk of infection at surgical sites [13–15]. There is still a lack of robust clinical evidence for the safety and efficacy of MI-TLIF compared with conventional O-TLIF. Earlier systematic reviews and meta-analyses have attempted to evaluate the safety and complications of MI-TLIF compared to O-TLIF [16, 17]. However, these were limited by smaller patient numbers and studies, as well as analysis of overlapping patient populations [18]. In the last 2 years alone, over double the number of studies have been reported in the literature and have been published [11, 12, 19–30] from unique centres, reflecting the rapid popularity of the minimally invasive approach worldwide. Therefore, the present meta-analysis was conducted to provide an updated assessment of the relative benefits and risks of MI-TLIF versus O-TLIF.
Methods Literature search strategy The study was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) [31]. Electronic searches were performed using Ovid Medline, PubMed, Cochrane Central Register of Controlled Trials (CCTR), Cochrane Database of Systematic Reviews (CDSR), ACP Journal Club, and Database of Abstracts of Review of Effectiveness (DARE) from their date of inception to December 2014. To achieve the maximum sensitivity of the search strategy, we combined the terms: ‘‘minimally invasive’’, ‘‘open’’, ‘‘transforaminal lumbar interbody fusion’’, ‘‘TLIF’’, as either key words or MeSH terms. A full search strategy is presented in Supplementary Table 1. The reference lists of all retrieved articles were reviewed for further identification of potentially relevant studies and assessed using the inclusion and exclusion criteria. Selection criteria For the purposes of this review, ‘‘minimally invasive surgery’’ was defined as surgery conducted through a tube, cylindrical retractor blades or sleeves via a muscle-dilating
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or muscle-splitting approach. Conventional or open surgery was defined as surgery via an approach which includes elevating or stripping the paraspinal muscles to gain access to the spine, even if by a limited midline incision. Eligible studies for the present systematic review and meta-analysis included studies comparing MI-TLIF versus O-TLIF for the treatment of degenerative lumbar disease. End points included average operation times, intraoperative blood loss, hospital stay, total complications, reoperations, dural tears, infections, postoperative VAS scores for back and leg pain and postoperative ODI scores. Studies that did not include operation parameters or complications as end points were excluded. When institutions published duplicate studies with accumulating numbers of patients or increased lengths of follow-up, only the most complete reports were included for quantitative assessment at each time interval. Reference lists were also hand searched for further relevant studies. All publications were limited to those involving human subjects and in the English language. Abstracts, case reports, conference presentations, editorials, reviews and expert opinions were excluded. Data extraction and criteria appraisal All data were extracted from article texts, tables and figures. Discrepancies between the two reviewers were resolved by discussion and consensus. Because quality scoring is controversial in meta-analyses of observational studies, two reviewers independently appraised each article included in our analysis according to a critical review checklist of the Dutch Cochrane Centre proposed by MOOSE [32, 33]. The final results were reviewed by senior investigators (R.J.M.). Statistical analysis For comparative studies, relative risk (RR) was used as a summary statistic for dichotomous variables, and weighted mean different (WMD) was used for continuous variables. In the present study, both fixed- and random-effect models were tested. In the fixed-effects model, it was assumed that treatment effect in each study was the same, whereas in a random-effects model, it was assumed that there were variations between studies. v2 tests were used to study heterogeneity between trials. I2 statistic was used to estimate the percentage of total variation across studies, owing to heterogeneity rather than chance, with values greater than 50 % considered as substantial heterogeneity. In the present meta-analysis, the results using the random-effects model were presented to take into account the possible clinical diversity and methodological variation between studies. Specific analyses considering confounding factors were not possible because raw data were not available. In
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an alternative way to account for heterogeneity, subgroup analysis was performed based on follow-up duration (B24 months, [24 months) and procedure technique (unilateral versus bilateral screw fixation). All P values were two sided. All statistical analysis was conducted with Review Manager Version 5.2.2 (Cochrane Collaboration, Software Update, Oxford, UK). Publication bias Evidence of publication bias was sought using Begg and Egger methods. Contour-enhanced funnel plot was performed to aid in interpretation of the funnel plot. Possible asymmetry was investigated using trim-and-fill analysis.
Results Included studies A total of 358 references were identified through six electronic database searches (Fig. 1). After exclusion of
1019
duplicate or irrelevant references, 324 potentially relevant articles were retrieved. After detailed evaluation of these articles, 42 studies remained for assessment. After applying the selection criteria, 21 articles [11, 12, 14, 15, 19–30, 34– 38] were selected for qualitative and quantitative analysis. The study characteristics are summarized in Table 1. Of the 21 included articles, 966 patients undergoing MI-TLIF were compared with 863 patients undergoing O-TLIF. The included studies comprised 11 prospective studies and 10 retrospective observational studies (Table 1). Of the prospective studies, two studies [26, 38] were randomized whilst nine studies were observational by design. There were 6 studies which investigated 100 or more patients in total [12, 22, 23, 25, 27, 36], with the remaining 15 studies investigating fewer than 100 patients in total. The inclusion criteria for patients in each study are summarized in Table 1, with the majority involving patients with degenerative disc disease or spondylolisthesis. The quality of the included studies was appraised using a checklist proposed by the Dutch Cochrane Centre by MOOSE. From this assessment, the majority of studies had clear definitions for study populations, clear definitions of
Fig. 1 PRISMA flowchart of systematic review and metaanalysis comparing minimally invasive (MI-TLIF) versus open transforaminal lumbar interbody fusion (O-TLIF)
123
123 2010–2011
China
USA
USA
Tian et al. [19]
Sulaiman et al. [20]
Singh et al. [21]
USA Italy
Germany
Australia
China
China
USA
China
Switzerland
Germany
Cheng et al. [28] Brodano et al. [29]
Archavlis et al. [30]
Mobbs et al. [14]
Wang et al. [38]
Wang et al. [37]
Villavicencio et al. [36]
Shunwu et al. [35]
Schizas et al. [15]
Schuefler et al. [34]
2004
NR
2005–2006
2002–2004
2006–2008
2006–2008
NR
2009–2010
2006–2011 2006–2010
2006–2012
2007–2008
2004–2007
R, OS
R, OS
P, OS
R, OS
R, OS
P, RCT
P, OS
R, OS
R, OS R, OS
R, OS
P, RCT
P, OS
R, OS
P, OS
P, OS
P, OS
R, OS
P, OS
P, OS
P, OS
Design
43
18
32
76
42
41
37
24
50 30
78
21
40
40
44
36
50
33
57
30
144
MI-TLIF
51
18
30
63
43
38
30
25
25 34
49
20
40
60
38
120
50
33
11
31
54
O-TLIF
Bi- or multilevel lumbar discopathy or degenerative pseudolisthesis
Grade I spondylolisthesis, foraminal stenosis
Single-level lumbar degeneration
Symptomatic degenerative disc disease
Degenerative and isthmic spondylolisthesis
Single-level degenerative lumbar spine disease
Degenerative lumbar spine pathologies
Severe stenotic degenerative spondylolisthesis, high-grade facet joint osteoarthritis
Spondylosis, spondylolisthesis, foraminal stenosis Disc degenerative disease or grade I degenerative spondylolisthesis
Spondylolisthesis, degenerative disc disease
Degenerative disc disease
Grade 1 or 2 spondylolisthesis or degenerative disc disease with mechanical lower back pain and radicular symptoms
Low-grade spondylolisthesis or degenerative disc disease
Two-level lumbar degenerative disease
Single-level lumbar degeneration
Lumbar spondylolisthesis
Lumbar degenerative disc disease (DDD), degenerative spondylolisthesis, or spinal stenosis
Degenerative spondylolisthesis
Symptomatic degenerative disease of the lumbosacral spine (L2-S1)
Degenerative lumbar disease
Pathology
NR not reported, P prospective, R retrospective, OS observational study, RCT randomized controlled trial
Spain
USA
Singapore
Rodriguez-Vela et al. [26]
2005–2008
France
Zairi et al. [25]
Seng et al. [11]
Lau et al. [27]
2010–2011
China
Gu et al. [24]
NR
Lo et al. [23]
2009–2012
USA
Taiwan
Parker et al. [22]
2008–2010
2009–2012
2006–2008
USA, China
Wong et al. [12]
Study period
Country
References
Table 1 Study characteristics
16
24
24
37.5
26.3
24
15.1
24
60.6 23
NR
36–54
60
24
20.3
12
24
24
24
25.6
45
Follow-up (months)
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outcomes and outcome assessment, and independent assessment of outcome parameters. Eight studies also did not effectively discuss important confounders and prognostic factors which further undermine the validity of their data. The quality appraisal is presented in Supplementary Table 2. Baseline characteristics Baseline characteristics of the included patients are summarized in Table 2. For the MI-TLIF cohort, the mean age ranged from 41.8 to 68.6 years, compared to 43.1–68 years for the O-TLIF cohort. The proportion of males ranged from 17.5 to 69.4 % and 17.5 to 74.2 % for MI-TLIF and O-TLIF, respectively. The proportions of MI-TLIF versus O-TLIF patients undergoing surgery for L5/S1, L4/5, L3/4 and L2/3 segments were not significantly different between the cohorts. Assessment of operation parameters The operation parameters are summarized in Fig. 2. The median operation duration for the minimally invasive approach was 185 min (range: 104–456 min), compared to 186 min (range: 113–375 min) for the conventional open approach. There was no significant difference in operation time noted between MI-TLIF and O-TLIF cohorts (WMD, 4.74; 95 % CI -58.55, 68.03; I2 = 100 %; P = 0.88). However, significant heterogeneity was detected amongst the included studies. The median intraoperative blood loss for MI-TLIF was 177 mL (range: 55–456 mL) compared with 461 mL (range: 125–961 mL) for the O-TLIF approach. This difference was significantly different (WMD, -256.23; 95 % CI -351.35, -161.1; P \ 0.00001) and was maintained upon subgroup analysis regardless of whether the procedure used bilateral or unilateral pedicle screw fixation. Significant heterogeneity (I2 = 98 %) was detected amongst studies reporting intraoperative blood loss. The hospital duration for MI-TLIF was also significantly shorter than that of the O-TLIF cohort (WMD, -1.86; 95 %, -2.69, -1.04; I2 = 96 %; P \ 0.00001). The median hospital stay for MI-TLIF and O-TLIF was 4.7 days (range: 2.3–10.6 days) and 8.0 days (range: 2.9–14.6 days), respectively. X-ray exposure time was significantly higher in the MI-TLIF group compared to O-TLIF by 37 s (WMD, 37.27; 95 % CI 13.78, 60.77; I2 = 98 %; P = 0.002). Assessment of major end points The total complications outcome was reported by 11 studies (Fig. 3). No significant difference in total complications was found between the MI-TLIF and O-TLIF cohorts (14.9
1021
vs 20 %; RR, 0.77; 95 %, 0.52, 1.15; I2 = 32 %; P = 0.20), with no significant heterogeneity detected. There were also no differences between minimally invasive and open cohorts in terms of reoperations required (5.5 vs 6.4 %; RR, 0.71; 95 % CI 0.44, 1.13; I2 = 0 %; P = 0.15). No significant heterogeneity amongst the studies was detected for reoperations. No significant differences in major outcomes were also noted in studies reporting follow-up B24 months and [24 months. Furthermore, the use of bilateral screw versus unilateral screws did not show any significant differences upon subgroup analysis; however, there were fewer studies to analyse and this may be a function of inadequate statistical power. Assessment of safety and complications Specific complication outcomes are reported in Fig. 4 and Table 3. No difference was found between MI-TLIF and O-TLIF cohorts in terms of dural tears (2.6 vs 4.7 %; RR, 0.59; 95 % CI 0.28, 1.22; I2 = 9 %; P = 0.15). However, the infection rates were significantly lower in the minimally invasive cohort (1.2 vs 4.6 %; RR, 0.27; 95 %, 0.14, 0.53; I2 = 0 %; P = 0.0001), with no significant heterogeneity detected. A similar trend was seen for bilateral screw fixation in MI-TLIF vs open TLIF and also for unilateral screw fixation in MI-TLIF vs open TLIF. Surgical procedure-related complications are summarized in Table 3. There was no significant difference between the MI-TLIF and O-TLIF cohorts for graft malposition (P = 0.66), screw malposition (P = 0.97), neurological deficit (P = 0.55), haematomas (P = 0.45), non-union (P = 0.94) and cerebrospinal fluid (CSF) leak (P = 0.39). The lack of statistically significant differences was also observed when subgroup analysis was performed, in both the bilateral screw TLIF analysis and unilateral screw TLIF analysis. Assessment of pain scores VAS back pain and leg pain scores as well as ODI scores were the most commonly used measures amongst the included studies for assessment of clinical outcomes. Summary changes of VAS and ODI scores are portrayed in Table 4, whilst the comparison between the MI-TLIF and O-TLIF cohorts in terms of postoperative VAS and ODI scores is summarized in Fig. 5. A descriptive method was used to extract mean changes, given that the standard deviations were poorly reported by the included studies. From Fig. 5, postoperative VAS back pain scores were significantly lower in the MI-TLIF group compared to O-TLIF (WMD, -0.41; 95 % CI -0.76, -0.06; I2 = 96 %; P \ 0.00001), with significant heterogeneity detected. Postoperative ODI scores were also significantly lower in
123
123 58
47.9 ± 8.5
50.5(19-91)
51.4 ± 7.2
45.5
56.8
Wang et al. [37]
Villavicencio et al. [36]
Shunwu et al. [35]
Schizas et al. [15]
Schuefler et al. [34]
53.3
48.1
52 ± 6.4
58.9(30-86)
53.2 ± 10.6
57.3 ± 12.1
67.48 ± 13.19
68 ± 7
54.3 ± 11.1 51
54.1 ± 14.1
43.15 ± 7.3
56.8 ± 1.67
42.4
44.2
NR
56.3
44.7
31.0
58.5
51.4
41.7
54.0 60.0
48.7
66.7
17.5
50
43.2
NR
32.0
69.7
29.8
53.3
47.1
NR
46.7
38.1
37.2
60.5
53.3
32.0
56.0 58.8
46.9
65.0
17.5
46.7
39.5
NR
36.0
63.6
36.4
74.2
46.3
O-TLIF
NR
NR
34.4
NR
42.9
36.6
16.2
25.0
20.0 23.3
46.2
NR
10.0
NR
NR
NR
28.0
NR
21.1
46.7
31.3
MI-TLIF
L5/S1 (%)
NR
NR
40.0
NR
39.5
44.7
30.0
28.0
20.0 29.4
30.6
NR
10.0
NR
NR
NR
34.0
NR
81.8
41.9
72.2
O-TLIF
NR
NR
62.5
NR
50.0
53.7
54.1
66.7
66.0 46.7
47.4
NR
85.0
NR
NR
NR
64.0
NR
64.9
46.7
29.9
MI-TLIF
L4/5 (%)
NR
NR
50.0
NR
53.5
47.4
50.0
54.0
48.0 70.6
40.8
NR
85.0
NR
NR
NR
60.0
NR
72.7
54.8
96.3
O-TLIF
NR not reported, MI-TLIF minimally invasive transforaminal lumbar interbody fusion, O-TLIF open transforaminal lumbar interbody fusion
68.56 ± 12.99
51.4 ± 15.3
67 ± 8
Archavlis et al. [30]
Mobbs et al. [14]
53.7 ± 11.5 46
Cheng et al. [28] Brodano et al. [29]
Wang et al. [38]
41.81 ± 8.7
52.5 ± 12.8
56.6 ± 1.63
Rodriguez-Vela et al. [26]
48
48
Zairi et al. [25]
Seng et al. [11]
Lau et al. [27]
64.1 ± 7.8
66.4 ± 6.7
Gu et al. [24]
52.6 ± 11.6 57.2
53.5 ± 12.5
53.5
Parker et al. [22]
49.85 ± 10.72
56.4
48.9 ± 8.89
Lo et al. [23]
61.1
51.67 ± 11.12
Singh et al. [21]
48.21 ± 9.1
Sulaiman et al. [20]
61
Tian et al. [19]
MI-TLIF
MI-TLIF
O-TLIF
Male (%)
Age (years)
Wong et al. [12]
References
Table 2 Baseline characteristics of included studies
NR
NR
3.1
NR
7.1
7.3
5.4
8.3
10.0 0
3.8
NR
5.0
NR
NR
NR
8.0
NR
3.5
6.7
6.3
MI-TLIF
L3/4 (%)
NR
NR
6.7
NR
7.0
2.6
0
4.0
6.0 0
22.4
NR
5.0
NR
NR
NR
6.0
NR
36.4
3.2
13.0
O-TLIF
NR
NR
0
NR
0
2.4
2.7
0
2.0 0
2.6
NR
0
NR
NR
NR
0
NR
0
0
2.1
MI-TLIF
L2/3 (%)
NR
NR
0
NR
0
5.3
0
0
0 0
4.1
NR
0
NR
NR
NR
0
NR
0
0
3.7
O-TLIF
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Fig. 2 Forest plots comparing MI-TLIF and O-TLIF in terms of a operation time; b intraoperative blood loss; c hospital stay
the minimally invasive cohort (WMD, -2.21; 95 % CI -4.26, -0.15; I2 = 93 %; P = 0.04). Significant heterogeneity was also detected. Upon subgroup analysis in
bilateral versus unilateral screw groups, differences in postoperative ODI and VAS back pain scores were mitigated and no longer significant.
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Fig. 3 Forest plots comparing MI-TLIF and O-TLIF in terms of a total complications; b reoperations
Publication bias Inspection of the funnel plot (Fig. 6) showed no apparent asymmetry for total complications. Trim-and-fill analysis indicated that no studies were missing. The effect size was unchanged by trim-and-fill analysis, 0.779 (95 % CI 0.576–1.055). Publication bias was assessed with Egger’s score (t value 0.694, P = 0.507) which was not significant, and Begg’s score (z value 0.894, P = 0.371) was nonsignificant. These results suggest that publication bias was likely not a limiting factor.
Discussion The clinical application of the MI-TLIF has not been matched with clinical evidence, as there is still a lack of adequately powered, multicentre randomized trials which
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directly compares the minimally invasive and open fusion approaches. From the current available evidence, the present systematic review and meta-analysis demonstrated that: (1) no difference in operation duration was found between MI-TLIF and O-TLIF; (2) MI-TLIF was associated with less intraoperative blood loss; (3) MI-TLIF was associated with increased X-ray exposure; (4) O-TLIF approach was associated with significantly higher rates of infection; and (5) patients who underwent MI-TLIF had significantly lower VAS and ODI pain scores compared to patients undergoing O-TLIF. Given the limited working space and surgical vision, MI-TLIF has often been reported to have a complex learning curve and thus associated with longer operative times. To assess and define the learning curve for MI-TLIF, Lee and colleagues [39] reported a prospective case series of 86 patients with degenerative lumbar disease who underwent unilateral transforaminal approach with
Eur Spine J (2015) 24:1017–1030
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Fig. 4 Forest plots comparing MI-TLIF and O-TLIF in terms of a dural tears; b infections
Table 3 Summary effect of surgical complications in metaanalysis comparing MI-TLIF with O-TLIF
Surgical complications
n/N MI-TLIF
N/N O-TLIF
RR (95 % CI)
I2 (%)
P value
Graft malposition
4/463
4/358
0.74 (0.19–2.84)
0
0.66
Screw malposition
12/571
6/391
0.98 (0.39–2.49)
0
0.97
Neurological deficit
20/400
7/244
1.28 (0.57–2.86)
0
0.55
Haematoma
7/330
7/229
0.63 (0.19–2.10)
21
0.45
Non-union
4/253
3/235
1.08 (0.14–8.65)
36
0.94
CSF leak
9/459
14/417
0.61 (0.20–1.88)
23
0.39
n number of affected patients, N number of total patients, RR relative risk, CI confidence interval
percutaneous pedicle screws. The operative time decreased as the series progressed and an asymptote was reached after 30 cases. The surgeons’ experience significantly correlated
with reduced operation time and intraoperative blood loss, suggesting that the minimally invasive approach may be a safe and effective treatment operation once the initial
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Table 4 Improvement of functional outcomes References
Mean back pain VAS improvement
Mean leg pain VAS improvement
Mean ODI improvement
MI-TLIF
MI-TLIF
MI-TLIF
O-TLIF
O-TLIF
O-TLIF
Wong et al. [12]
-4.12
-2.77
-7.47
-6.6
-26.8
-18.2
Tian et al. [19]
-3.56
-3.71
-5.3
-5.34
-26.33
-26.47
Sulaiman et al. [20]
-4.2
-2.1
NR
NR
-28
-12
Singh et al. [21]
NR
NR
NR
NR
NR
NR
Parker et al. [22]
-4.8
-4.9
-3.5
-4.2
-21.3
-18.7
Lo et al. [23]
NR
NR
NR
NR
NR
NR
Gu et al. [24] Zairi et al. [25]
-5.4 NR
-5.6 NR
-5.9 NR
-5.9 NR
-27.2 NR
-28.4 NR
Seng et al. [11]
-4.3
-5.9
-5.1
-4.7
-27.7
-29.8
Rodriguez-Vela et al. [26]
-3.7
-2.57
-4.93
-4.39
-16.76
-9.09
Lau et al. [27]
NR
NR
NR
NR
NR
NR
Cheng et al. [28]
-4.1
-4.3
NR
NR
NR
NR
Brodano et al. [29]
-5.5
-5.5
NR
NR
-32
-34
Archavlis et al. [30]
-4.4
-3.8
-4
-3.8
-23
-24
Mobbs et al. [14]
-5.5
-4.9
NR
NR
-32
-24
Wang et al. [38]
-5.8
-5.3
NR
NR
-27.3
-26.4
Wang et al. [37]
-6.3
-6.3
NR
NR
-30.4
-26.3
Villavicencio et al. [36]
-4
-4.8
NR
NR
NR
NR
Shunwu et al. [35]
-4.5
-3.6
NR
NR
-25
-24.8
Schizas et al. [15]
-4.2
-2.2
NR
NR
-22
-27
Schuefler et al. [34]
NR
NR
NR
NR
NR
NR
NR not reported, MI-TLIF minimally invasive transforaminal lumbar interbody fusion, O-TLIF open transforaminal lumbar interbody fusion, n number of affected patients, N number of total patients, RR relative risk, CI confidence interval
learning curve is traversed. These results are corroborated by other studies [40, 41], which show significant reduced complication rates and operation durations in the later phase of their MI-TLIF series. Additionally, the increased use of navigation imaging during pedicle screw placement may also increase operation durations while increasing the surgeon’s exposure to potentially harmful ionizing radiation [42, 43]. In the present meta-analysis, no significant difference was found between MI-TLIF and O-TLIF cohorts in terms of operation duration, which is likely attributed to the varying surgical expertise and experience amongst the included studies. In comparison to other minimally invasive PLIF, MI-TLIF tends to have reduced operation duration since the decompression and cage is inserted unilaterally. Proponents of the minimally invasive fusion procedure emphasize its potential advantages of reduced iatrogenic tissue injury and complication rates. In the present, there is a significant reduction in blood loss and infection rates in the MI-TLIF group. These trends are not surprising, given that MI-TLIF employs a tubular retraction which preserves the contralateral ligament and bony attachments of paraspinal muscles, thereby reducing potential bleeding. The minimal muscle dissection and bone removal also will
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reduce complications attributed to blood clot accumulation and tissue fluid accumulation [23]. The need for smaller incisions and minimal open exposure of MI-TLIF also significantly reduced the opportunity for bacteria entry and hence infection of the surgical sites. In contrast, O-TLIF involves a large midline incision and extensive dissection. This is often performed using high-force retraction of paraspinal muscles, increasing blood loss, surgical trauma and increased risk of infection. Other surgical complications, including dural tear, graft and screw malposition, and haematomas were similar between the groups. Total complications and reoperation rates were also comparable between MI-TLIF and O-TLIF. Minimized surgical trauma and complications also justify the significantly shorter hospitalization for the MI-TLIF cohort observed. However, hospital stay results should be interpreted with caution, given the different health-care systems and reimbursement schemes in different countries, factors which could not be accounted for in this analysis. Some groups have also reported an increased incidence of adjacent-level revision surgery at long-term follow-up in the O-TLIF cohort, potentially due to the less destabilizing nature of MI-TLIF [12]. However, there have been few reports of this phenomenon and it thus requires further validation in
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Fig. 5 Forest plots comparing MI-TLIF and O-TLIF in terms of a postoperative VAS back pain scores; b postoperative ODI
Fig. 6 Funnel plot for total complications in MI-TLIF versus O-TLIF
adequately powered prospective trials. Overall, results from the present meta-analysis suggest that MI-TLIF can be performed safely with reduced intraoperative blood loss and infection rates compared to conventional open approaches. However, it must be noted that any advantages of MI-TLIF is offset by the increased radiation exposure to the surgical team. Minimized surgical trauma via the use of tubular retractors and reduced paraspinal muscle dissection is likely
responsible for the significant reduction in postoperative VAS and ODI pain scores in the MI-TLIF cohort versus O-TLIF. From the present meta-analysis, the mean difference in VAS back pain scores was 0.4 points lower for MITLIF, and 2.2 points lower for ODI score in MI-TLIF compared to O-TLIF. However, these differences in pain outcomes are inconsistently reported in the literature, with studies by Seng et al. [11] demonstrating significantly worse pain outcomes in the MI-TLIF group. To alternatively assess pain outcomes, Mobbs et al. [14] looked at opioid analgesia as a surrogate marker for pain outcomes following fusion surgery, with no difference in usage or dosage between MI-TLIF and O-TLIF cohorts, which is a contradictory significant difference in VAS and ODI scores. Other problems with the use of pain scores are the heterogeneity in the follow-up protocols among the included studies, making it difficult to ascertain the temporal extent of the improvement in pain scores. Prior studies have suggested that improvements in pain and disability outcomes are significant for 12 months, after which little further improvement occurs [44, 45]. Investigations by Datta et al. [46] have also suggested that score improvement is directly associated with shorter durations of intramuscular pressures. Thus, for operations performed during
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the early phase of the learning curve, longer operation durations may be associated with poorer VAS and ODI pain score outcomes. Overall, the current results suggest that MI-TLIF is an effective alternative to O-TLIF with at least equivalent pain score outcomes and potentially reduced pain scores in some cases. Strengths and limitations The present systematic review and meta-analysis has several strengths. Firstly, PRISMA guidelines for systematic reviews were strictly followed, with the PRISMA checklist shown in Supplementary Table 3. The systematic review was performed according to a ‘‘priori’’ design question and inclusion criteria. A comprehensive literature search strategy was used, and in contrast to earlier reviews on this topic, the scientific quality of the included studies was assessed using a well-known quality appraisal tool [32]. Furthermore, publication bias was assessed using funnel plots. Quality assessment highlighted the poorer quality of studies in terms of duration of follow-up and prognostic indicators, therefore, providing tangible evidence that the literature requires upgrade of evidence in terms of adequately powered, randomized studies with long-term follow-up. Prior meta-analyses based on fewer number of studies suggest that there are no differences in VAS or ODI functional outcomes between minimally invasive versus open TLIF [17], or only described the differences without statistical methods [16]. In contrast, our meta-analysis is based on 21 studies and a total of 1829 patients, more than twice the number of total patients, and thus was adequately powered to detect a significant difference in functional VAS and ODI outcomes. While infection rates were intuitively thought to be less in the minimally invasive approach, to our knowledge, our meta-analysis is the first to show that pooled infection rates were lower in the minimally invasive group. The present study is also limited by several constraints. Firstly, there is a lack of an official definition or consensus on what procedures actually constitute ‘‘minimally invasive surgery’’ compared to ‘‘standard open’’ surgery. The transition between these two is not clearly defined, dependent on individual surgical technique. Reduced skin incisions likely have a more cosmetic effect, whilst the damage to the musculature, fascia and insertion points, facet joints and their capsules, as well as ligaments, is likely to have reduced surgical trauma. Unfortunately, these aspects were not well reported in the included studies and thus a significant limitation not only of the present study, but of the literature in general. Furthermore, the majority of included studies were observational cohort studies, with a similar ratio of retrospective and prospective studies. There is a lack of clinically robust randomized
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controlled trials. Therefore, the validity of the data available for meta-analysis may be undermined by selection bias. Second, there is heterogeneity among the included studies with regard to difference in surgical experience and expertise, different inclusion and exclusion criteria, as well as slight variations between centres in terms of MI-TLIF and O-TLIF surgical techniques. To address the effect of unilateral vs bilateral screw fixation on outcomes, we performed subgroup analysis on our results. Similar trends were seen for blood loss outcomes, infections and complications for both unilateral and bilateral screw fixation MI-TLIF techniques compared with open TLIF. Variations in follow-up durations as well as inconsistent and unstandardized reporting of pain score outcomes are also additional limitations of the present studies. To address this, subgroup analysis was performed according to follow-up duration (B24 months, [24 months), but similar trends were observed. Future multi-center prospective registry or randomized studies with long-term follow-up are required to validate the trends observed.
Conclusion In summary, the present systematic review and meta-analysis demonstrated that MI-TLIF was associated with reduced intraoperative blood loss, infection rates and postoperative VAS and ODI pain scores compared to O-TLIF, albeit with higher radiation exposure and risk for the surgical team. No difference in operation duration and total complications was detected. MI-TLIF appears to be a safe and efficacious approach, but the long-term relative merits require further validation in prospective, randomized studies. Conflict of interest The authors have no conflict of interest whatsoever in the conduct of the study or its results.
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REVIEW ARTICLE
Minimally invasive versus open transforaminal lumbar interbody fusion for treatment of degenerative lumbar disease: systematic review and meta-analysis Kevin Phan1,2 • Prashanth J. Rao1,2 • Andrew C. Kam2 • Ralph J. Mobbs1
Received: 22 January 2015 / Revised: 21 March 2015 / Accepted: 22 March 2015 / Published online: 27 March 2015 Ó Springer-Verlag Berlin Heidelberg 2015
Abstract Purpose While open TLIF (O-TLIF) remains the mainstay approach, minimally invasive TLIF (MI-TLIF) may offer potential advantages of reduced trauma to paraspinal muscles, minimized perioperative blood loss, quicker recovery and reduced risk of infection at surgical sites. This meta-analysis was conducted to provide an updated assessment of the relative benefits and risks of MI-TLIF versus O-TLIF. Methods Electronic searches were performed using six databases from their inception to December 2014. Relevant studies comparing MI-TLIF and O-TLIF were included. Data were extracted and analysed according to predefined clinical end points. Results There was no significant difference in operation time noted between MI-TLIF and O-TLIF cohorts. The median intraoperative blood loss for MI-TLIF was significantly lower than O-TLIF (median: 177 vs 461 mL; (weighted mean difference) WMD, -256.23; 95 % CI -351.35, -161.1; P \ 0.00001). Infection rates were significantly lower in the minimally invasive cohort (1.2 vs
Electronic supplementary material The online version of this article (doi:10.1007/s00586-015-3903-4) contains supplementary material, which is available to authorized users. & Kevin Phan [email protected] Ralph J. Mobbs [email protected] 1
Neurospine Clinic and Neurospine Surgery Research Group (NSURG), Prince of Wales Private Hospital, Randwick, Sydney, NSW 2031, Australia
2
Department of Neurosurgery, Westmead Hospital, Sydney, Australia
4.6 %; relative risk (RR), 0.27; 95 %, 0.14, 0.53; I2 = 0 %; P = 0.0001). VAS back pain scores were significantly lower in the MI-TLIF group compared to O-TLIF (WMD, -0.41; 95 % CI -0.76, -0.06; I2 = 96 %; P \ 0.00001). Postoperative ODI scores were also significantly lower in the minimally invasive cohort (WMD, -2.21; 95 % CI -4.26, -0.15; I2 = 93 %; P = 0.04). Conclusions In summary, the present systematic review and meta-analysis demonstrated that MI-TLIF appears to be a safe and efficacious approach compared to O-TLIF. MI-TLIF is associated with lower blood loss and infection rates in patients, albeit at the risk of higher radiation exposure for the surgical team. The long-term relative merits require further validation in prospective, randomized studies. Keywords Minimally invasive Transforaminal lumbar interbody fusion TLIF Lumbar Spine Degenerative
Introduction Degenerative spinal diseases are one of the most common comorbidities in elderly patients, leading to discogenic back pain and spinal instability [1, 2]. Transforaminal lumbar interbody fusion (TLIF) is one of the surgical options used for the stabilization and treatment of degenerative lumbar disease such as disc degeneration and spondylolisthesis which has failed conservative management. TLIF was initially developed as a modification of the posterior lumbar interbody fusion (PLIF) approach [3, 4], with added advantages of direct, unilateral access to the intervertebral foraminal area whilst reducing interruption to the spinal muscles and structural integrity [5–9]. While open TLIF (O-TLIF) is an established approach for
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degenerative lumbar disease, there are still concerns surrounding the associated long hospital stays, excessive blood loss and postoperative complications associated with an open procedure [10–12]. The advent of minimally invasive procedures in the surgical realm led to the logical progression of O-TLIF to minimally invasive TLIF (MI-TLIF) over the past decade. MI-TLIF offers potential advantages of reduced trauma to paraspinal muscles, minimized perioperative blood loss, quicker recovery and reduced risk of infection at surgical sites [13–15]. There is still a lack of robust clinical evidence for the safety and efficacy of MI-TLIF compared with conventional O-TLIF. Earlier systematic reviews and meta-analyses have attempted to evaluate the safety and complications of MI-TLIF compared to O-TLIF [16, 17]. However, these were limited by smaller patient numbers and studies, as well as analysis of overlapping patient populations [18]. In the last 2 years alone, over double the number of studies have been reported in the literature and have been published [11, 12, 19–30] from unique centres, reflecting the rapid popularity of the minimally invasive approach worldwide. Therefore, the present meta-analysis was conducted to provide an updated assessment of the relative benefits and risks of MI-TLIF versus O-TLIF.
Methods Literature search strategy The study was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) [31]. Electronic searches were performed using Ovid Medline, PubMed, Cochrane Central Register of Controlled Trials (CCTR), Cochrane Database of Systematic Reviews (CDSR), ACP Journal Club, and Database of Abstracts of Review of Effectiveness (DARE) from their date of inception to December 2014. To achieve the maximum sensitivity of the search strategy, we combined the terms: ‘‘minimally invasive’’, ‘‘open’’, ‘‘transforaminal lumbar interbody fusion’’, ‘‘TLIF’’, as either key words or MeSH terms. A full search strategy is presented in Supplementary Table 1. The reference lists of all retrieved articles were reviewed for further identification of potentially relevant studies and assessed using the inclusion and exclusion criteria. Selection criteria For the purposes of this review, ‘‘minimally invasive surgery’’ was defined as surgery conducted through a tube, cylindrical retractor blades or sleeves via a muscle-dilating
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or muscle-splitting approach. Conventional or open surgery was defined as surgery via an approach which includes elevating or stripping the paraspinal muscles to gain access to the spine, even if by a limited midline incision. Eligible studies for the present systematic review and meta-analysis included studies comparing MI-TLIF versus O-TLIF for the treatment of degenerative lumbar disease. End points included average operation times, intraoperative blood loss, hospital stay, total complications, reoperations, dural tears, infections, postoperative VAS scores for back and leg pain and postoperative ODI scores. Studies that did not include operation parameters or complications as end points were excluded. When institutions published duplicate studies with accumulating numbers of patients or increased lengths of follow-up, only the most complete reports were included for quantitative assessment at each time interval. Reference lists were also hand searched for further relevant studies. All publications were limited to those involving human subjects and in the English language. Abstracts, case reports, conference presentations, editorials, reviews and expert opinions were excluded. Data extraction and criteria appraisal All data were extracted from article texts, tables and figures. Discrepancies between the two reviewers were resolved by discussion and consensus. Because quality scoring is controversial in meta-analyses of observational studies, two reviewers independently appraised each article included in our analysis according to a critical review checklist of the Dutch Cochrane Centre proposed by MOOSE [32, 33]. The final results were reviewed by senior investigators (R.J.M.). Statistical analysis For comparative studies, relative risk (RR) was used as a summary statistic for dichotomous variables, and weighted mean different (WMD) was used for continuous variables. In the present study, both fixed- and random-effect models were tested. In the fixed-effects model, it was assumed that treatment effect in each study was the same, whereas in a random-effects model, it was assumed that there were variations between studies. v2 tests were used to study heterogeneity between trials. I2 statistic was used to estimate the percentage of total variation across studies, owing to heterogeneity rather than chance, with values greater than 50 % considered as substantial heterogeneity. In the present meta-analysis, the results using the random-effects model were presented to take into account the possible clinical diversity and methodological variation between studies. Specific analyses considering confounding factors were not possible because raw data were not available. In
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an alternative way to account for heterogeneity, subgroup analysis was performed based on follow-up duration (B24 months, [24 months) and procedure technique (unilateral versus bilateral screw fixation). All P values were two sided. All statistical analysis was conducted with Review Manager Version 5.2.2 (Cochrane Collaboration, Software Update, Oxford, UK). Publication bias Evidence of publication bias was sought using Begg and Egger methods. Contour-enhanced funnel plot was performed to aid in interpretation of the funnel plot. Possible asymmetry was investigated using trim-and-fill analysis.
Results Included studies A total of 358 references were identified through six electronic database searches (Fig. 1). After exclusion of
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duplicate or irrelevant references, 324 potentially relevant articles were retrieved. After detailed evaluation of these articles, 42 studies remained for assessment. After applying the selection criteria, 21 articles [11, 12, 14, 15, 19–30, 34– 38] were selected for qualitative and quantitative analysis. The study characteristics are summarized in Table 1. Of the 21 included articles, 966 patients undergoing MI-TLIF were compared with 863 patients undergoing O-TLIF. The included studies comprised 11 prospective studies and 10 retrospective observational studies (Table 1). Of the prospective studies, two studies [26, 38] were randomized whilst nine studies were observational by design. There were 6 studies which investigated 100 or more patients in total [12, 22, 23, 25, 27, 36], with the remaining 15 studies investigating fewer than 100 patients in total. The inclusion criteria for patients in each study are summarized in Table 1, with the majority involving patients with degenerative disc disease or spondylolisthesis. The quality of the included studies was appraised using a checklist proposed by the Dutch Cochrane Centre by MOOSE. From this assessment, the majority of studies had clear definitions for study populations, clear definitions of
Fig. 1 PRISMA flowchart of systematic review and metaanalysis comparing minimally invasive (MI-TLIF) versus open transforaminal lumbar interbody fusion (O-TLIF)
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123 2010–2011
China
USA
USA
Tian et al. [19]
Sulaiman et al. [20]
Singh et al. [21]
USA Italy
Germany
Australia
China
China
USA
China
Switzerland
Germany
Cheng et al. [28] Brodano et al. [29]
Archavlis et al. [30]
Mobbs et al. [14]
Wang et al. [38]
Wang et al. [37]
Villavicencio et al. [36]
Shunwu et al. [35]
Schizas et al. [15]
Schuefler et al. [34]
2004
NR
2005–2006
2002–2004
2006–2008
2006–2008
NR
2009–2010
2006–2011 2006–2010
2006–2012
2007–2008
2004–2007
R, OS
R, OS
P, OS
R, OS
R, OS
P, RCT
P, OS
R, OS
R, OS R, OS
R, OS
P, RCT
P, OS
R, OS
P, OS
P, OS
P, OS
R, OS
P, OS
P, OS
P, OS
Design
43
18
32
76
42
41
37
24
50 30
78
21
40
40
44
36
50
33
57
30
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MI-TLIF
51
18
30
63
43
38
30
25
25 34
49
20
40
60
38
120
50
33
11
31
54
O-TLIF
Bi- or multilevel lumbar discopathy or degenerative pseudolisthesis
Grade I spondylolisthesis, foraminal stenosis
Single-level lumbar degeneration
Symptomatic degenerative disc disease
Degenerative and isthmic spondylolisthesis
Single-level degenerative lumbar spine disease
Degenerative lumbar spine pathologies
Severe stenotic degenerative spondylolisthesis, high-grade facet joint osteoarthritis
Spondylosis, spondylolisthesis, foraminal stenosis Disc degenerative disease or grade I degenerative spondylolisthesis
Spondylolisthesis, degenerative disc disease
Degenerative disc disease
Grade 1 or 2 spondylolisthesis or degenerative disc disease with mechanical lower back pain and radicular symptoms
Low-grade spondylolisthesis or degenerative disc disease
Two-level lumbar degenerative disease
Single-level lumbar degeneration
Lumbar spondylolisthesis
Lumbar degenerative disc disease (DDD), degenerative spondylolisthesis, or spinal stenosis
Degenerative spondylolisthesis
Symptomatic degenerative disease of the lumbosacral spine (L2-S1)
Degenerative lumbar disease
Pathology
NR not reported, P prospective, R retrospective, OS observational study, RCT randomized controlled trial
Spain
USA
Singapore
Rodriguez-Vela et al. [26]
2005–2008
France
Zairi et al. [25]
Seng et al. [11]
Lau et al. [27]
2010–2011
China
Gu et al. [24]
NR
Lo et al. [23]
2009–2012
USA
Taiwan
Parker et al. [22]
2008–2010
2009–2012
2006–2008
USA, China
Wong et al. [12]
Study period
Country
References
Table 1 Study characteristics
16
24
24
37.5
26.3
24
15.1
24
60.6 23
NR
36–54
60
24
20.3
12
24
24
24
25.6
45
Follow-up (months)
1020 Eur Spine J (2015) 24:1017–1030
Eur Spine J (2015) 24:1017–1030
outcomes and outcome assessment, and independent assessment of outcome parameters. Eight studies also did not effectively discuss important confounders and prognostic factors which further undermine the validity of their data. The quality appraisal is presented in Supplementary Table 2. Baseline characteristics Baseline characteristics of the included patients are summarized in Table 2. For the MI-TLIF cohort, the mean age ranged from 41.8 to 68.6 years, compared to 43.1–68 years for the O-TLIF cohort. The proportion of males ranged from 17.5 to 69.4 % and 17.5 to 74.2 % for MI-TLIF and O-TLIF, respectively. The proportions of MI-TLIF versus O-TLIF patients undergoing surgery for L5/S1, L4/5, L3/4 and L2/3 segments were not significantly different between the cohorts. Assessment of operation parameters The operation parameters are summarized in Fig. 2. The median operation duration for the minimally invasive approach was 185 min (range: 104–456 min), compared to 186 min (range: 113–375 min) for the conventional open approach. There was no significant difference in operation time noted between MI-TLIF and O-TLIF cohorts (WMD, 4.74; 95 % CI -58.55, 68.03; I2 = 100 %; P = 0.88). However, significant heterogeneity was detected amongst the included studies. The median intraoperative blood loss for MI-TLIF was 177 mL (range: 55–456 mL) compared with 461 mL (range: 125–961 mL) for the O-TLIF approach. This difference was significantly different (WMD, -256.23; 95 % CI -351.35, -161.1; P \ 0.00001) and was maintained upon subgroup analysis regardless of whether the procedure used bilateral or unilateral pedicle screw fixation. Significant heterogeneity (I2 = 98 %) was detected amongst studies reporting intraoperative blood loss. The hospital duration for MI-TLIF was also significantly shorter than that of the O-TLIF cohort (WMD, -1.86; 95 %, -2.69, -1.04; I2 = 96 %; P \ 0.00001). The median hospital stay for MI-TLIF and O-TLIF was 4.7 days (range: 2.3–10.6 days) and 8.0 days (range: 2.9–14.6 days), respectively. X-ray exposure time was significantly higher in the MI-TLIF group compared to O-TLIF by 37 s (WMD, 37.27; 95 % CI 13.78, 60.77; I2 = 98 %; P = 0.002). Assessment of major end points The total complications outcome was reported by 11 studies (Fig. 3). No significant difference in total complications was found between the MI-TLIF and O-TLIF cohorts (14.9
1021
vs 20 %; RR, 0.77; 95 %, 0.52, 1.15; I2 = 32 %; P = 0.20), with no significant heterogeneity detected. There were also no differences between minimally invasive and open cohorts in terms of reoperations required (5.5 vs 6.4 %; RR, 0.71; 95 % CI 0.44, 1.13; I2 = 0 %; P = 0.15). No significant heterogeneity amongst the studies was detected for reoperations. No significant differences in major outcomes were also noted in studies reporting follow-up B24 months and [24 months. Furthermore, the use of bilateral screw versus unilateral screws did not show any significant differences upon subgroup analysis; however, there were fewer studies to analyse and this may be a function of inadequate statistical power. Assessment of safety and complications Specific complication outcomes are reported in Fig. 4 and Table 3. No difference was found between MI-TLIF and O-TLIF cohorts in terms of dural tears (2.6 vs 4.7 %; RR, 0.59; 95 % CI 0.28, 1.22; I2 = 9 %; P = 0.15). However, the infection rates were significantly lower in the minimally invasive cohort (1.2 vs 4.6 %; RR, 0.27; 95 %, 0.14, 0.53; I2 = 0 %; P = 0.0001), with no significant heterogeneity detected. A similar trend was seen for bilateral screw fixation in MI-TLIF vs open TLIF and also for unilateral screw fixation in MI-TLIF vs open TLIF. Surgical procedure-related complications are summarized in Table 3. There was no significant difference between the MI-TLIF and O-TLIF cohorts for graft malposition (P = 0.66), screw malposition (P = 0.97), neurological deficit (P = 0.55), haematomas (P = 0.45), non-union (P = 0.94) and cerebrospinal fluid (CSF) leak (P = 0.39). The lack of statistically significant differences was also observed when subgroup analysis was performed, in both the bilateral screw TLIF analysis and unilateral screw TLIF analysis. Assessment of pain scores VAS back pain and leg pain scores as well as ODI scores were the most commonly used measures amongst the included studies for assessment of clinical outcomes. Summary changes of VAS and ODI scores are portrayed in Table 4, whilst the comparison between the MI-TLIF and O-TLIF cohorts in terms of postoperative VAS and ODI scores is summarized in Fig. 5. A descriptive method was used to extract mean changes, given that the standard deviations were poorly reported by the included studies. From Fig. 5, postoperative VAS back pain scores were significantly lower in the MI-TLIF group compared to O-TLIF (WMD, -0.41; 95 % CI -0.76, -0.06; I2 = 96 %; P \ 0.00001), with significant heterogeneity detected. Postoperative ODI scores were also significantly lower in
123
123 58
47.9 ± 8.5
50.5(19-91)
51.4 ± 7.2
45.5
56.8
Wang et al. [37]
Villavicencio et al. [36]
Shunwu et al. [35]
Schizas et al. [15]
Schuefler et al. [34]
53.3
48.1
52 ± 6.4
58.9(30-86)
53.2 ± 10.6
57.3 ± 12.1
67.48 ± 13.19
68 ± 7
54.3 ± 11.1 51
54.1 ± 14.1
43.15 ± 7.3
56.8 ± 1.67
42.4
44.2
NR
56.3
44.7
31.0
58.5
51.4
41.7
54.0 60.0
48.7
66.7
17.5
50
43.2
NR
32.0
69.7
29.8
53.3
47.1
NR
46.7
38.1
37.2
60.5
53.3
32.0
56.0 58.8
46.9
65.0
17.5
46.7
39.5
NR
36.0
63.6
36.4
74.2
46.3
O-TLIF
NR
NR
34.4
NR
42.9
36.6
16.2
25.0
20.0 23.3
46.2
NR
10.0
NR
NR
NR
28.0
NR
21.1
46.7
31.3
MI-TLIF
L5/S1 (%)
NR
NR
40.0
NR
39.5
44.7
30.0
28.0
20.0 29.4
30.6
NR
10.0
NR
NR
NR
34.0
NR
81.8
41.9
72.2
O-TLIF
NR
NR
62.5
NR
50.0
53.7
54.1
66.7
66.0 46.7
47.4
NR
85.0
NR
NR
NR
64.0
NR
64.9
46.7
29.9
MI-TLIF
L4/5 (%)
NR
NR
50.0
NR
53.5
47.4
50.0
54.0
48.0 70.6
40.8
NR
85.0
NR
NR
NR
60.0
NR
72.7
54.8
96.3
O-TLIF
NR not reported, MI-TLIF minimally invasive transforaminal lumbar interbody fusion, O-TLIF open transforaminal lumbar interbody fusion
68.56 ± 12.99
51.4 ± 15.3
67 ± 8
Archavlis et al. [30]
Mobbs et al. [14]
53.7 ± 11.5 46
Cheng et al. [28] Brodano et al. [29]
Wang et al. [38]
41.81 ± 8.7
52.5 ± 12.8
56.6 ± 1.63
Rodriguez-Vela et al. [26]
48
48
Zairi et al. [25]
Seng et al. [11]
Lau et al. [27]
64.1 ± 7.8
66.4 ± 6.7
Gu et al. [24]
52.6 ± 11.6 57.2
53.5 ± 12.5
53.5
Parker et al. [22]
49.85 ± 10.72
56.4
48.9 ± 8.89
Lo et al. [23]
61.1
51.67 ± 11.12
Singh et al. [21]
48.21 ± 9.1
Sulaiman et al. [20]
61
Tian et al. [19]
MI-TLIF
MI-TLIF
O-TLIF
Male (%)
Age (years)
Wong et al. [12]
References
Table 2 Baseline characteristics of included studies
NR
NR
3.1
NR
7.1
7.3
5.4
8.3
10.0 0
3.8
NR
5.0
NR
NR
NR
8.0
NR
3.5
6.7
6.3
MI-TLIF
L3/4 (%)
NR
NR
6.7
NR
7.0
2.6
0
4.0
6.0 0
22.4
NR
5.0
NR
NR
NR
6.0
NR
36.4
3.2
13.0
O-TLIF
NR
NR
0
NR
0
2.4
2.7
0
2.0 0
2.6
NR
0
NR
NR
NR
0
NR
0
0
2.1
MI-TLIF
L2/3 (%)
NR
NR
0
NR
0
5.3
0
0
0 0
4.1
NR
0
NR
NR
NR
0
NR
0
0
3.7
O-TLIF
1022 Eur Spine J (2015) 24:1017–1030
Eur Spine J (2015) 24:1017–1030
1023
Fig. 2 Forest plots comparing MI-TLIF and O-TLIF in terms of a operation time; b intraoperative blood loss; c hospital stay
the minimally invasive cohort (WMD, -2.21; 95 % CI -4.26, -0.15; I2 = 93 %; P = 0.04). Significant heterogeneity was also detected. Upon subgroup analysis in
bilateral versus unilateral screw groups, differences in postoperative ODI and VAS back pain scores were mitigated and no longer significant.
123
1024
Eur Spine J (2015) 24:1017–1030
Fig. 3 Forest plots comparing MI-TLIF and O-TLIF in terms of a total complications; b reoperations
Publication bias Inspection of the funnel plot (Fig. 6) showed no apparent asymmetry for total complications. Trim-and-fill analysis indicated that no studies were missing. The effect size was unchanged by trim-and-fill analysis, 0.779 (95 % CI 0.576–1.055). Publication bias was assessed with Egger’s score (t value 0.694, P = 0.507) which was not significant, and Begg’s score (z value 0.894, P = 0.371) was nonsignificant. These results suggest that publication bias was likely not a limiting factor.
Discussion The clinical application of the MI-TLIF has not been matched with clinical evidence, as there is still a lack of adequately powered, multicentre randomized trials which
123
directly compares the minimally invasive and open fusion approaches. From the current available evidence, the present systematic review and meta-analysis demonstrated that: (1) no difference in operation duration was found between MI-TLIF and O-TLIF; (2) MI-TLIF was associated with less intraoperative blood loss; (3) MI-TLIF was associated with increased X-ray exposure; (4) O-TLIF approach was associated with significantly higher rates of infection; and (5) patients who underwent MI-TLIF had significantly lower VAS and ODI pain scores compared to patients undergoing O-TLIF. Given the limited working space and surgical vision, MI-TLIF has often been reported to have a complex learning curve and thus associated with longer operative times. To assess and define the learning curve for MI-TLIF, Lee and colleagues [39] reported a prospective case series of 86 patients with degenerative lumbar disease who underwent unilateral transforaminal approach with
Eur Spine J (2015) 24:1017–1030
1025
Fig. 4 Forest plots comparing MI-TLIF and O-TLIF in terms of a dural tears; b infections
Table 3 Summary effect of surgical complications in metaanalysis comparing MI-TLIF with O-TLIF
Surgical complications
n/N MI-TLIF
N/N O-TLIF
RR (95 % CI)
I2 (%)
P value
Graft malposition
4/463
4/358
0.74 (0.19–2.84)
0
0.66
Screw malposition
12/571
6/391
0.98 (0.39–2.49)
0
0.97
Neurological deficit
20/400
7/244
1.28 (0.57–2.86)
0
0.55
Haematoma
7/330
7/229
0.63 (0.19–2.10)
21
0.45
Non-union
4/253
3/235
1.08 (0.14–8.65)
36
0.94
CSF leak
9/459
14/417
0.61 (0.20–1.88)
23
0.39
n number of affected patients, N number of total patients, RR relative risk, CI confidence interval
percutaneous pedicle screws. The operative time decreased as the series progressed and an asymptote was reached after 30 cases. The surgeons’ experience significantly correlated
with reduced operation time and intraoperative blood loss, suggesting that the minimally invasive approach may be a safe and effective treatment operation once the initial
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Eur Spine J (2015) 24:1017–1030
Table 4 Improvement of functional outcomes References
Mean back pain VAS improvement
Mean leg pain VAS improvement
Mean ODI improvement
MI-TLIF
MI-TLIF
MI-TLIF
O-TLIF
O-TLIF
O-TLIF
Wong et al. [12]
-4.12
-2.77
-7.47
-6.6
-26.8
-18.2
Tian et al. [19]
-3.56
-3.71
-5.3
-5.34
-26.33
-26.47
Sulaiman et al. [20]
-4.2
-2.1
NR
NR
-28
-12
Singh et al. [21]
NR
NR
NR
NR
NR
NR
Parker et al. [22]
-4.8
-4.9
-3.5
-4.2
-21.3
-18.7
Lo et al. [23]
NR
NR
NR
NR
NR
NR
Gu et al. [24] Zairi et al. [25]
-5.4 NR
-5.6 NR
-5.9 NR
-5.9 NR
-27.2 NR
-28.4 NR
Seng et al. [11]
-4.3
-5.9
-5.1
-4.7
-27.7
-29.8
Rodriguez-Vela et al. [26]
-3.7
-2.57
-4.93
-4.39
-16.76
-9.09
Lau et al. [27]
NR
NR
NR
NR
NR
NR
Cheng et al. [28]
-4.1
-4.3
NR
NR
NR
NR
Brodano et al. [29]
-5.5
-5.5
NR
NR
-32
-34
Archavlis et al. [30]
-4.4
-3.8
-4
-3.8
-23
-24
Mobbs et al. [14]
-5.5
-4.9
NR
NR
-32
-24
Wang et al. [38]
-5.8
-5.3
NR
NR
-27.3
-26.4
Wang et al. [37]
-6.3
-6.3
NR
NR
-30.4
-26.3
Villavicencio et al. [36]
-4
-4.8
NR
NR
NR
NR
Shunwu et al. [35]
-4.5
-3.6
NR
NR
-25
-24.8
Schizas et al. [15]
-4.2
-2.2
NR
NR
-22
-27
Schuefler et al. [34]
NR
NR
NR
NR
NR
NR
NR not reported, MI-TLIF minimally invasive transforaminal lumbar interbody fusion, O-TLIF open transforaminal lumbar interbody fusion, n number of affected patients, N number of total patients, RR relative risk, CI confidence interval
learning curve is traversed. These results are corroborated by other studies [40, 41], which show significant reduced complication rates and operation durations in the later phase of their MI-TLIF series. Additionally, the increased use of navigation imaging during pedicle screw placement may also increase operation durations while increasing the surgeon’s exposure to potentially harmful ionizing radiation [42, 43]. In the present meta-analysis, no significant difference was found between MI-TLIF and O-TLIF cohorts in terms of operation duration, which is likely attributed to the varying surgical expertise and experience amongst the included studies. In comparison to other minimally invasive PLIF, MI-TLIF tends to have reduced operation duration since the decompression and cage is inserted unilaterally. Proponents of the minimally invasive fusion procedure emphasize its potential advantages of reduced iatrogenic tissue injury and complication rates. In the present, there is a significant reduction in blood loss and infection rates in the MI-TLIF group. These trends are not surprising, given that MI-TLIF employs a tubular retraction which preserves the contralateral ligament and bony attachments of paraspinal muscles, thereby reducing potential bleeding. The minimal muscle dissection and bone removal also will
123
reduce complications attributed to blood clot accumulation and tissue fluid accumulation [23]. The need for smaller incisions and minimal open exposure of MI-TLIF also significantly reduced the opportunity for bacteria entry and hence infection of the surgical sites. In contrast, O-TLIF involves a large midline incision and extensive dissection. This is often performed using high-force retraction of paraspinal muscles, increasing blood loss, surgical trauma and increased risk of infection. Other surgical complications, including dural tear, graft and screw malposition, and haematomas were similar between the groups. Total complications and reoperation rates were also comparable between MI-TLIF and O-TLIF. Minimized surgical trauma and complications also justify the significantly shorter hospitalization for the MI-TLIF cohort observed. However, hospital stay results should be interpreted with caution, given the different health-care systems and reimbursement schemes in different countries, factors which could not be accounted for in this analysis. Some groups have also reported an increased incidence of adjacent-level revision surgery at long-term follow-up in the O-TLIF cohort, potentially due to the less destabilizing nature of MI-TLIF [12]. However, there have been few reports of this phenomenon and it thus requires further validation in
Eur Spine J (2015) 24:1017–1030
1027
Fig. 5 Forest plots comparing MI-TLIF and O-TLIF in terms of a postoperative VAS back pain scores; b postoperative ODI
Fig. 6 Funnel plot for total complications in MI-TLIF versus O-TLIF
adequately powered prospective trials. Overall, results from the present meta-analysis suggest that MI-TLIF can be performed safely with reduced intraoperative blood loss and infection rates compared to conventional open approaches. However, it must be noted that any advantages of MI-TLIF is offset by the increased radiation exposure to the surgical team. Minimized surgical trauma via the use of tubular retractors and reduced paraspinal muscle dissection is likely
responsible for the significant reduction in postoperative VAS and ODI pain scores in the MI-TLIF cohort versus O-TLIF. From the present meta-analysis, the mean difference in VAS back pain scores was 0.4 points lower for MITLIF, and 2.2 points lower for ODI score in MI-TLIF compared to O-TLIF. However, these differences in pain outcomes are inconsistently reported in the literature, with studies by Seng et al. [11] demonstrating significantly worse pain outcomes in the MI-TLIF group. To alternatively assess pain outcomes, Mobbs et al. [14] looked at opioid analgesia as a surrogate marker for pain outcomes following fusion surgery, with no difference in usage or dosage between MI-TLIF and O-TLIF cohorts, which is a contradictory significant difference in VAS and ODI scores. Other problems with the use of pain scores are the heterogeneity in the follow-up protocols among the included studies, making it difficult to ascertain the temporal extent of the improvement in pain scores. Prior studies have suggested that improvements in pain and disability outcomes are significant for 12 months, after which little further improvement occurs [44, 45]. Investigations by Datta et al. [46] have also suggested that score improvement is directly associated with shorter durations of intramuscular pressures. Thus, for operations performed during
123
1028
the early phase of the learning curve, longer operation durations may be associated with poorer VAS and ODI pain score outcomes. Overall, the current results suggest that MI-TLIF is an effective alternative to O-TLIF with at least equivalent pain score outcomes and potentially reduced pain scores in some cases. Strengths and limitations The present systematic review and meta-analysis has several strengths. Firstly, PRISMA guidelines for systematic reviews were strictly followed, with the PRISMA checklist shown in Supplementary Table 3. The systematic review was performed according to a ‘‘priori’’ design question and inclusion criteria. A comprehensive literature search strategy was used, and in contrast to earlier reviews on this topic, the scientific quality of the included studies was assessed using a well-known quality appraisal tool [32]. Furthermore, publication bias was assessed using funnel plots. Quality assessment highlighted the poorer quality of studies in terms of duration of follow-up and prognostic indicators, therefore, providing tangible evidence that the literature requires upgrade of evidence in terms of adequately powered, randomized studies with long-term follow-up. Prior meta-analyses based on fewer number of studies suggest that there are no differences in VAS or ODI functional outcomes between minimally invasive versus open TLIF [17], or only described the differences without statistical methods [16]. In contrast, our meta-analysis is based on 21 studies and a total of 1829 patients, more than twice the number of total patients, and thus was adequately powered to detect a significant difference in functional VAS and ODI outcomes. While infection rates were intuitively thought to be less in the minimally invasive approach, to our knowledge, our meta-analysis is the first to show that pooled infection rates were lower in the minimally invasive group. The present study is also limited by several constraints. Firstly, there is a lack of an official definition or consensus on what procedures actually constitute ‘‘minimally invasive surgery’’ compared to ‘‘standard open’’ surgery. The transition between these two is not clearly defined, dependent on individual surgical technique. Reduced skin incisions likely have a more cosmetic effect, whilst the damage to the musculature, fascia and insertion points, facet joints and their capsules, as well as ligaments, is likely to have reduced surgical trauma. Unfortunately, these aspects were not well reported in the included studies and thus a significant limitation not only of the present study, but of the literature in general. Furthermore, the majority of included studies were observational cohort studies, with a similar ratio of retrospective and prospective studies. There is a lack of clinically robust randomized
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Eur Spine J (2015) 24:1017–1030
controlled trials. Therefore, the validity of the data available for meta-analysis may be undermined by selection bias. Second, there is heterogeneity among the included studies with regard to difference in surgical experience and expertise, different inclusion and exclusion criteria, as well as slight variations between centres in terms of MI-TLIF and O-TLIF surgical techniques. To address the effect of unilateral vs bilateral screw fixation on outcomes, we performed subgroup analysis on our results. Similar trends were seen for blood loss outcomes, infections and complications for both unilateral and bilateral screw fixation MI-TLIF techniques compared with open TLIF. Variations in follow-up durations as well as inconsistent and unstandardized reporting of pain score outcomes are also additional limitations of the present studies. To address this, subgroup analysis was performed according to follow-up duration (B24 months, [24 months), but similar trends were observed. Future multi-center prospective registry or randomized studies with long-term follow-up are required to validate the trends observed.
Conclusion In summary, the present systematic review and meta-analysis demonstrated that MI-TLIF was associated with reduced intraoperative blood loss, infection rates and postoperative VAS and ODI pain scores compared to O-TLIF, albeit with higher radiation exposure and risk for the surgical team. No difference in operation duration and total complications was detected. MI-TLIF appears to be a safe and efficacious approach, but the long-term relative merits require further validation in prospective, randomized studies. Conflict of interest The authors have no conflict of interest whatsoever in the conduct of the study or its results.
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1029
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
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