Clinical Orthopaedics and Related Research®
Clin Orthop Relat Res (2014) 472:1792–1799 DOI 10.1007/s11999-014-3619-5
A Publication of The Association of Bone and Joint Surgeons®
SYMPOSIUM: MINIMALLY INVASIVE SPINE SURGERY
Minimally Invasive versus Open Posterior Lumbar Interbody Fusion: A Systematic Review Gursukhman S. Sidhu MBBS, Erik Henkelman BSE, Alexander R. Vaccaro MD, PhD, Todd J. Albert MD, Alan Hilibrand MD, D. Greg Anderson MD, Jeffrey A. Rihn MD
Published online: 19 April 2014 Ó The Association of Bone and Joint Surgeons1 2014
Abstract Background Although conventional open posterior lumbar interbody fusion (open PLIF) is efficacious in management of lumbar spinal instability, concerns exist regarding lengthy hospital stays, blood loss, and postoperative complications. Minimally invasive posterior lumbar interbody fusion (MIS PLIF) may be able to address these concerns, but the research on this topic has not been systematically reviewed. Questions/purposes We performed a systematic review to determine whether MIS PLIF or open PLIF results in (1) better perioperative parameters, including blood loss, operative times, and length of hospital stay; (2) improved patient-reported outcome scores; and (3) improved disc distraction and (4) frequency of reoperation and complications when compared with open PLIF procedures. Methods A literature search of the MEDLINE database identified seven studies that met our inclusion criteria. A total of seven articles were included; quality was assessed using the Methodological Index for Non-Randomised Studies (MINORS) scale. Descriptive statistics were used to describe the included articles. Each author certifies that he or she, or a member of his or her immediate family, has no funding or commercial associations (eg, consultancies, stock ownership, equity interest, patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article. All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research editors and board members are on file with the publication and can be viewed on request. G. S. Sidhu, E. Henkelman, A. R. Vaccaro, T. J. Albert, A. Hilibrand, D. Greg Anderson, J. A. Rihn (&) Rothman Institute & Thomas Jefferson University Hospital, 925 Chestnut Street, Philadelphia, PA 19107, USA e-mail: [email protected]
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Results In most studies, MIS PLIF was associated with decreased blood loss and shorter hospital stay but longer operative times. MIS PLIF resulted in better patient-related outcomes when compared with open PLIF in two studies in the short term, but most of the studies in this review found no short-term differences, and there was no difference at long-term followup in any studies. There was no significant difference in disc distraction. Both techniques appeared to have similar complication rates and reoperation rates. Conclusions Based on the available evidence, which we restricted to prospective and retrospective studies with control groups, but did not include any well-designed randomized trials, MIS PLIF might lead to better perioperative parameters, but there was little evidence for improved patient-reported outcomes in the MIS groups. Randomized controlled trials are needed to compare these two surgical techniques.
Introduction Posterior lumbar interbody fusion (PLIF) is a widely accepted surgical technique for the management of a variety of spinal conditions requiring spinal stabilization and fusion [15, 17, 19, 22]. Compared with posterolateral and lateral approaches, PLIF may be advantageous, providing a wider area of intervertebral interbody graft bone contact surface, improved load-sharing, adequate access for complete decompression of the neural elements, restoration of neural foraminal height, and the ability to restore segmental lordosis at the involved level [1–3, 5, 10]. Multiple studies report a high fusion rate ranging between 89% and 97% with this technique [4, 7, 11, 18, 26, 30, 32]. Although studies have demonstrated the success of conventional, open PLIF, concerns exist regarding the
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morbidity of the procedure, a high procedural blood loss, postoperative complications, and lengthy hospital stays [12–14]. To address such concerns related to posteriorbased, open spinal surgery, Foley et al. [8] developed a tubular retractor system for microdiscectomy in 1994. Later on, the tubular retractor system was modified, which, along with the development of advanced surgical instrumentation and optical systems, led to the development of minimally invasive posterior lumbar interbody fusion (MIS PLIF) technique. Preliminary evidence in the literature demonstrates the MIS PLIF approach to be associated with decreased iatrogenic muscle injury, less blood loss, and less postoperative pain compared with the traditional approach. These benefits could potentially yield earlier mobilization, shorter hospital stay, and shorter functional recovery. However, MIS approaches are themselves associated with some problems. MIS PLIF may be associated with an increased operative time and hence increased radiation [24, 27]. The learning curve for all MIS is steep, which coupled with limited visibility makes it a technically demanding procedure [18, 27]. Multiple studies report a high complication rate during the learning stage [6, 16, 23]. Recently, a number of comparative studies have compared the effectiveness of open PLIF and MIS PLIF for degenerative spinal conditions [4, 7, 11, 18, 20, 26, 28]. However, consensus regarding superiority of either approach is lacking as a result of inconsistent conclusions in the various studies. We therefore performed a systematic review to evaluate whether MIS PLIF was associated with (1) better perioperative parameters, including operative time, intraoperative blood loss, and postoperative drainage; (2) improved clinical outcomes (Oswestry Disability Index [ODI], visual analog scale [VAS], and Prolo score [21]); (3) improved disc distraction; and (4) lower frequency of reoperation and complications.
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articles with the longest followup were included. The following inclusion criteria were applied: (1) the study included a comparative design (MIS PLIF versus open PLIF). As a result of variability in MIS techniques used among multiple studies, only studies that used a tubular retractor for pedicle screw insertion were considered true MIS approaches. In brief, the PLIF technique defined involved decompression of the affected nerve root, reduction of the listhesis, and posterior interbody fusion and was distinctively stated to be performed differently from a transforaminal lumbar interbody fusion procedure; (2) the study population consisted of adult patients with degenerative lumbar conditions (spondylolisthesis [degenerative and isthmic] and spinal stenosis); (3) at least one of the outcomes needed to be reported: perioperative results (operative time, blood loss, hospital stay, etc), pain or disability improvement, complications, or reoperations; and (4) the study had a minimum recorded followup of 6 months. Articles were excluded for any of the following characteristics: (1) article included less than five patients in any of the two groups; (2) patients with reported spinal deformity, trauma, or spinal tumors; and (3) case reports, case series that did not include a comparator or historical control group, editorials, and commentary and case reports. The search yielded a total of 101 articles (Fig. 1). Of these, 24 articles were screened after excluding 77 articles based on the titles and the abstracts. Of the stated articles,
Materials and Methods Search Strategy and Criteria Two independent reviewers (GSS, JAR) performed a review of the literature on May 24, 2013, using Medline, Scopus, and the Cochrane Register of Controlled Trials database. Studies were limited to those published in the English language. The following keywords were searched for by combining the term ‘‘posterior lumbar interbody fusion’’ or ‘‘PLIF’’ with ‘‘MIS’’, ‘‘minimally invasive’’, or ‘‘minimally invasive spine surgery’’. No randomized controlled trials currently exist in the literature; therefore, nonrandomized comparative prospective and retrospective studies with historical control groups were included. Additionally, bibliographies of retrieved articles were also searched. For articles from the same institution, only the
Fig. 1 Flowchart for study selection is shown.
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Table 1. Details of included studies Study or subgroup
Year
Country
Number of patients
Design
Mean followup (months)
MINORS scale
Park and Ha [20]
2007
South Korea
62
PCT
12 (minimum)
18
Fan et al. [7]
2010
China
59
PCT
12
19
Tsutsumimoto et al. [26]
2009
Japan
20
PCT
24 (minimum)
15
Ntoukas and Muller [18]
2010
Germany
40
RCT
12
13
Wang et al. [28]
2010
USA
74
RCT
14
12
Jang et al. [11]
2011
South Korea
20
PCT
6
16
Cheung et al. [4]
2013
Australia
52
PCT
36
17
MINORS = Methodological Index for Non-Randomised Studies; the global ideal score is 24 for comparative studies; PCT = prospective comparative study; RCT = retrospective comparative study.
13 articles were included after full-text review and bibliographic search. Four studies were not included because the data were unseparable from other operative approaches (for example, transforaminal lumbar interbody fusion, extreme lateral interbody fusion) in terms of differentiating individual approach-related patient data. Two studies were later excluded because they used a minimally invasive open approach in which the pedicle screw insertion site was openly visualized. This left a total of seven studies (Table 1).
exposure time, and hospital stay; (6) patient-reported outcome score improvement at last followup including VAS, ODI, and SF-36; (7) disc height; and (8) complication types and complication frequencies. Both total and specified complication rates were extracted. We referred to the previous published review to categorize specified complication types [25]. Data were extracted from each of the selected papers independently by two evaluators (JAR, GSS); there was complete agreement regarding inclusion or exclusion in all cases. Given the lack of prospective randomized trials, a meta-analysis was not attempted. Our systematic review was performed in accordance with the PRISMA guidelines.
Study Quality Quality of level of evidence rating was assigned to each article independently by two reviewers (GSS, JAR) using standard criteria for therapeutic studies as defined for orthopaedic surgical literature [31]. Methodological quality was estimated using the Methodological Index for NonRandomised Studies (MINORS), which is a validated instrument designed for assessment of the methodologic quality of nonrandomized studies in surgery (Table 1). The global ideal score is 24 for comparative studies on a MINORS scale.
Data Extraction We extracted data based on the following categories: (1) study year, country, and study design; (2) basic study characteristics including patients’ inclusion/exclusion criteria, enrolled number, age, and sex proportion; (3) baseline comparison information of confounding factors such as sex, age, height, weight, body mass index, diagnosis, surgical level, insurance, education, smoking status, alcohol use, workers compensation, and concomitant diseases; (4) surgical information, instrumentation, and bone graft; (5) perioperative parameters such as operative time, intraoperative and postoperative blood loss, intraoperative radiograph
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Results Perioperative Parameters Five studies reported operative time; four of the five provided the mean and SD (Table 2). In four studies, MIS PLIF required a longer operative time, whereas in one study, open PLIF required more time. Six studies provided information about length of hospital stay (Table 3). In all studies, MIS PLIF cases reportedly had a shorter length of stay compared with open PLIF procedures. Five studies assessed intraoperative blood loss with a quantifiable mean and SD (Table 4). All studies reported lower intraoperative blood loss in the MIS PLIF group. Postoperative drainage was documented in two studies, which reported lower postoperative drainage for the MIS PLIF group (Table 5).
Clinical Outcomes All seven studies had certain clinical outcome parameters by which they assessed improvement in function and decrease in disability. In all studies, there was a reduction in overall VAS, ODI, and Prolo outcome scores at final followup compared with baseline, demonstrating
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Table 2. Average surgical time (minutes) Study or subgroup
MIS PLIF
Open PLIF
Mean
SD
Total (number)
Mean
SD
Total (number) 31
Fan et al. 2010 [7]
203.6
36.6
28
194.5
47.2
Cheung et al. 2013 [4]
220*
202–288*
21
203*
175–260*
23
Ntoukas and Muller, 2010 [18]
275
73
20
152
38
20
Park and Ha, 2007 [20]
191.7
37.7
32
148.8
24.2
29
Tsutsumimoto et al. 2009 [26]
148.3
48.4
10
155.8
33.5
10
*
Study reported median and interquartile range; statistical significance (p\0.05); MIS = minimally invasive surgery; PLIF = posterior lumbar interbody fusion.
Table 3. Average length of hospital stay (days) Study or subgroup
MIS PLIF
Open PLIF
Mean
SD
Total
Mean
SD
Total
Fan et al. 2010 [7]
9.5
2
28
15.2
3.4
31
Cheung et al. 2013 [4]
4*
3–5*
23
7*
5–8*
24 20
Ntoukas and Muller, 2010 [18]
5
2.2
20
10
3.1
Park and Ha, 2007 [20]
5.3
2.6
32
10.8
2.5
29
Wang et al. 2010 [28]
3.9
1.06
44
4.8
1.42
15
Study reported median and interquartile range; statistical significance (p\0.05); MIS = minimally invasive surgery; PLIF = posterior lumbar interbody fusion.
*
Table 4. Average intraoperative blood loss (mLs) Study or subgroup
MIS PLIF
Open PLIF
Mean
SD
Total
Mean
SD
Total
Fan et al. 2010 [7]*
496.4
217.2
28
887.7
555.3
31
Ntoukas and Muller, 2010 [18]*
135
98
20
432
151
20
Park and Ha, 2007 [20]*
432.8
294.8
32
737.9
224.3
29
Tsutsumimoto et al. 2009 [26]
282
259.8
10
352.6
304.6
10
Wang et al. 2010 [28]*
145
73
44
400
116
15
*
Statistical significance (p \ 0.05: MIS = minimally invasive surgery; PLIF = posterior lumbar interbody fusion.
Table 5. Average postoperative drainage (mLs) Study or subgroup
Fan et al. 2010 [7]*
MIS PLIF
Open PLIF
Mean SD
Total Mean SD
Total
146.7 61.9
28
31
Park and Ha, 2007 [20]* 175
162.2 32
344.3 114
482.9 165.3 29
*
Statistical significance (p \ 0.05); MIS = minimally invasive surgery; PLIF = posterior lumbar interbody fusion.
significant improvement in function as a result of PLIF with both the MIS and open approaches. To provide an overall assessment of clinical improvement, a descriptive analysis was used (Table 6). Descriptively, two studies reported better outcome for the MIS PLIF group versus the
open PLIF group based on back pain VAS, ODI, and low back pain score parameters. Two studies documented better VAS/ODI score for MIS PLIF versus open PLIF at 1 and 3 months followup, respectively. In both studies, no difference in outcome scores between groups was observed at long-term followup. However, five studies did not find a benefit to MIS PLIF over open PLIF in terms of validated outcomes scores, including the VAS (Table 7).
Radiological Outcome Three studies compared for a possible difference in disc distraction between the MIS PLIF and the open PLIF
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123 Percent slip reduction rate greater in open PLIF versus MIS PLIF group (p = 0.01); both groups exhibited solid fusion at 1 year No difference in disc distraction between groups at 1-year followup
MIS PLIF group with less postoperative back pain (p \ 0.001) and lower postoperative ODI score (p = 0.001) versus open PLIF
Both groups significantly improved JOA score compared with baseline; no significant difference in improvement between the two groups at 2-year followup
VAS and ODI scores lower (p \ 0.05) at 3 months for MIS PLIF versus open PLIF; no significant difference between groups at 1-year followup
Mean change in modified PROLO score showed no difference between groups for one-level procedures; mean improvement in modified PROLO score for two-level MIS PLIF versus open PLIF (p \ 0.007)
MIS PLIF group at 1 month had lower back pain VAS score (p = 0.037) compared with open PLIF; no significant difference between groups for back pain VAS, leg pain VAS, and mean low back outcome score at long-term followup
No difference in VAS back and leg pain SF-36 scores at long-term followup; both groups demonstrated improved score compared with base line (p \ 0.05)
Fan et al. 2010 [7]
Tsutsumimoto et al. 2009 [26]
Ntoukas and Muller, 2010 [18]
Wang et al. 2010 [28]
Jang et al. 2011 [11]
Cheung et al. 2013 [4]
VAS = visual analog scale; MIS = minimally invasive surgery; PLIF = posterior lumbar interbody fusion; ODI = Oswestry disability index; JOA = Japanese Orthopaedic Society; NA = not applicable.
NA
NA
NA
NA
Postoperative multifidus atrophy was significantly less in MIS PLIF versus open PLIF at final followup
Multifidus atrophy less in MIS PLIF group (p \ 0.001); VAS and ODI score at final followup correlated with percent change in cross-sectional area of all measured multifidus muscles
NA
Multifidus changes at long-term followup
Sidhu et al.
Postoperative disc height difference was not statistically significant at long-term followup between open PLIF and MIS PLIF groups
NA
NA
NA
No difference (p = 0.398) in disc distraction at 1-year followup; average subsidence of disc space similar (p = 0.852) in both groups; solid fusion was achieved (p = 1) in both groups at 1 year
Mean VAS for postoperative back pain was lower (p \ 0.05) for MIS PLIF versus open PLIF at 1 year; PROLO outcomes were similar (p = 1) between groups
Park and Ha, 2007 [20]
Fusion outcome
MIS group versus open group change in outcome
Study or subgroup
Table 6. Descriptive clinical and radiographic outcomes
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MIS PLIF versus OPEN PLIF: A Systematic Review
Table 7. Average VAS score at final followup Study or subgroup
MIS PLIF
Open PLIF
Mean SD
Total Mean SD
Total
Fan et al. 2010 [7]
1.8
0.6
28
3.4
0.5
31
Ghahreman et al. 2010 [9]
2*
1–5* 25
2*
0–4* 27
Ntoukas and Muller, 2010 [18] Park and Ha, 2007 [20]
2
1.1
20
2.5
2.5
20
2.1
1.4
32
3.8
1.8
29
*
Study reported median and interquartile range; statistical significance (p \ 0.05); VAS = visual analog scale; MIS = minimally invasive surgery; PLIF = posterior lumbar interbody fusion.
groups (Table 6). There was no difference in disc distraction between the groups in the three studies that assessed this endpoint. Fusion rate was inadequately assessed in the studies and could not be compared.
Reoperation and Complication Frequencies Four main complication types including instrumentation failure, dural tear, infection, and reoperation rate were observed in the eligible studies. No differences were detected between open and MIS PLIF in terms of complication types or frequencies.
Discussion PLIF has been documented in multiple studies to achieve a satisfactory fusion rate, restore disc height, and achieve satisfactory clinical outcomes on long-term followup [9]. However, the procedure has drawbacks with a long midline incision and wider exposure perhaps increasing intraoperative blood loss and resulting in injury to the supporting paraspinal musculature. MIS PLIF, a relatively newer approach, may reduce approach-related morbidity and early results in terms of pain and function. However, the data in support of this contention derive mainly from case series with the kinds of biases in study design usually associated with that sort of retrospective analysis. We therefore sought to perform a systematic review of comparative studies (prospective and retrospective) to evaluate MIS and open PLIF in terms of perioperative parameters, validated outcomes scores, key radiological endpoints, and complications. Our systematic review has multiple weaknesses. First, because the roster of prospective studies is small, retrospective comparative studies had to be included. Most studies had methodological defects, including but not limited to nonconsecutive enrollment of patients,
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inadequate baseline comparisons, inadequate measurement of clinical outcomes, and reported complications. Some studies did not use contemporary validated outcome measures [7, 11]. Considerable heterogeneity was present in the data. This could have been because of incomplete data recording in individual studies, variable patient characteristics, and the diverse technical specification of each study in question. Despite this, our systematic review still provides some value to the clinician in light of the absence of high-quality randomized controlled trials. Second, the minimally invasive and open surgical techniques used in these studies were quite variable, introducing limitation in making general conclusions because each approach may have had unique issues related to clinical outcomes and complications. Third, the description of disease characteristics (isthmic versus degenerative spondylolisthesis versus spinal stenosis) was very nonuniform. In addition, a detailed description of bone graft and substitutes was not consistently documented. Lastly, the documentation and reporting of complications related to surgery were extremely variable. There is no consensus or standard system of documenting complications and, therefore, these data may not provide comprehensive information regarding the potential risks of MIS PLIF surgery. Overall, MIS PLIF was reported to result in decreased intraoperative blood loss, decreased postoperative drainage, and a decreased length of stay, but operative time was higher in MIS PLIF. This represents a major issue with MIS surgery overall. Although studies report it to decrease intraoperative blood loss and length of stay, higher operative time increases the time the patient is under anesthesia as well as higher radiation exposure from multiple fluoroscopic images required for adequate screw placement. This is complicated by the high learning curve required for performing MIS techniques overall. Another open question that remains is the actual costs associated with each procedure. Wang et al. [29] reported lower costs by evaluating hospital charges using an MIS PLIF approach for one-level and two-level procedures. Although MIS procedures may reduce costs by reducing inpatient stay, the increased operative time may influence the number of procedures per day, especially in high-volume surgical centers. All studies in our systematic review demonstrated decreased pain and improved function from baseline after PLIF surgery in a majority of the patients with both approaches, but superiority of MIS PLIF in terms of patient-reported outcomes scores compared with open PLIF was not proven here. Two studies in our systematic review did demonstrate improved early outcome scores in MIS PLIF over open PLIF; however, this effect was noticed during the early timeframe postoperatively and became negligible at [ 1-year followup. However, five studies did not find a benefit to MIS PLIF over open PLIF
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in terms of validated outcomes scores [4, 11, 20, 26, 28]. This suggests MIS may result in a quicker decrease in postoperative pain and functional recovery, but no studies in our review evaluated return to work status for patients. Cheung et al. [4] followed patients for a timeframe between 3 and 7 years and reported no difference in all clinical parameters between both groups. The reoperation rate for both MIS PLIF and open PLIF techniques was very low but quite variable across the studies we identified. The definition of ‘‘complication’’ was different in each study and hence may account for its variability. It should be noted that for a specific complication type, the data revealed no apparent differences between MIS PLIF and open PLIF techniques. This may have been because all our studies were done at single spine centers that are well established in MIS procedures. A larger multicenter study with a uniform complication recording tool could have better elicited the difference in the rate of complications between MIS PLIF and open PLIF techniques. The low rate of complications does suggest all PLIF procedures are relatively safe with minimal risk for major perioperative complications. In conclusion, our systematic review suggests MIS PLIF is associated with less operative blood loss and shorter hospital stay. However, we found no apparent differences between the approaches in terms of patient-reported outcome scores, the frequency of complications, and the efficacy in terms of disc distraction. A number of unresolved issues require answers. Uniform validated instruments of documenting clinical outcomes and reporting perioperative complications are needed to assist more refined clinical investigation. Large patient populations must be evaluated to better answer clinically relevant questions. Lastly, clinical randomized trials are needed to determine the relative efficacy of MIS and open PLIF techniques.
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Clinical Orthopaedics and Related Research1 6. Eck JC, Hodges S, Humphreys SC. Minimally invasive lumbar spinal fusion. J Am Acad Orthop Surg. 2007;15:321–329. 7. Fan S, Hu Z, Zhao F, Zhao X, Huang Y, Fang X. Multifidus muscle changes and clinical effects of one-level posterior lumbar interbody fusion: minimally invasive procedure versus conventional open approach. Eur Spine J. 2010;19:316–324. 8. Foley KT, Gupta SK, Justis JR, Sherman MC. Percutaneous pedicle screw fixation of the lumbar spine. Neurosurg Focus. 2001;10:E10. 9. Ghahreman A, Ferch RD, Rao PJ, Bogduk N. Minimal access versus open posterior lumbar interbody fusion in the treatment of spondylolisthesis. Neurosurgery. 2010;66:296–304; discussion 304. 10. Groth AT, Kuklo TR, Klemme WR, Polly DW, Schroeder TM. Comparison of sagittal contour and posterior disc height following interbody fusion: threaded cylindrical cages versus structural allograft versus vertical cages. J Spinal Disord Tech. 2005;18:332–336. 11. Jang KS, Kim HS, Ju CI, Kim SW, Lee SM, Shin H. Paraspinal muscle sparing versus percutaneous screw fixation: a prospective and comparative study for the treatment of L5-S1 spondylolisthesis. J Korean Neurosurg Soc. 2011;49:163–166. 12. Kawaguchi Y, Matsui H, Tsuji H. Back muscle injury after posterior lumbar spine surgery. Part 1: histologic and histochemical analyses in rats. Spine. 1994;19:2590–2597. 13. Kawaguchi Y, Matsui H, Tsuji H. Back muscle injury after posterior lumbar spine surgery. Part 2: histologic and histochemical analyses in humans. Spine. 1994;19:2598–2602. 14. Kawaguchi Y, Yabuki S, Styf J, Olmarker K, Rydevik B, Matsui H, Tsuji H. Back muscle injury after posterior lumbar spine surgery. Topographic evaluation of intramuscular pressure and blood flow in the porcine back muscle during surgery. Spine. 1996;21:2683–2688. 15. Kim DH, Jeong ST, Lee SS. Posterior lumbar interbody fusion using a unilateral single cage and a local morselized bone graft in the degenerative lumbar spine. Clin Orthop Surg. 2009;1:214–221. 16. Lau D, Lee JG, Han SJ, Lu DC, Chou D. Complications and perioperative factors associated with learning the technique of minimally invasive transforaminal lumbar interbody fusion (TLIF). J Clin Neurosci. 2011;18:624–627. 17. McLaughlin MR, Haid RW Jr, Rodts GE Jr, Subach BR. Posterior lumbar interbody fusion: indications, techniques, and results. Clin Neurosurg. 2000;47:514–527. 18. Ntoukas V, Muller A. Minimally invasive approach versus traditional open approach for one level posterior lumbar interbody fusion. Minim Invasive Neurosurg. 2010;53:21–24. 19. Ono A, Suetsuna F, Irie T, Yokoyama T, Numasawa T, Wada K, Toh S. Clinical significance of the redundant nerve roots of the cauda equina documented on magnetic resonance imaging. J Neurosurg Spine. 2007;7:27–32. 20. Park Y, Ha JW. Comparison of one-level posterior lumbar interbody fusion performed with a minimally invasive approach or a traditional open approach. Spine. 2007;32:537–543. 21. Prolo DJ, Oklund SA, Butcher M. Toward uniformity in evaluating results of lumbar spine operations. A paradigm applied to posterior lumbar interbody fusions. Spine. 1986;11:601–606. 22. Rousseau MA, Lazennec JY, Bass EC, Saillant G. Predictors of outcomes after posterior decompression and fusion in degenerative spondylolisthesis. Eur Spine J. 2005;14:55–60. 23. Schizas C, Tzinieris N, Tsiridis E, Kosmopoulos V. Minimally invasive versus open transforaminal lumbar interbody fusion: evaluating initial experience. Int Orthop. 2009;33:1683–1688. 24. Teng H, Wang L, Guo Z, Fan L, Zhang D, Zhang W, Wang S. [Research of single incision via MAST Quadrant retractor in management of lumbar spondylolisthesis] [in Chinese]. Zhongguo Xiu Fu Chong Jian Wai Ke Za Zhi. 2010;24:517–520.
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Clin Orthop Relat Res (2014) 472:1792–1799 DOI 10.1007/s11999-014-3619-5
A Publication of The Association of Bone and Joint Surgeons®
SYMPOSIUM: MINIMALLY INVASIVE SPINE SURGERY
Minimally Invasive versus Open Posterior Lumbar Interbody Fusion: A Systematic Review Gursukhman S. Sidhu MBBS, Erik Henkelman BSE, Alexander R. Vaccaro MD, PhD, Todd J. Albert MD, Alan Hilibrand MD, D. Greg Anderson MD, Jeffrey A. Rihn MD
Published online: 19 April 2014 Ó The Association of Bone and Joint Surgeons1 2014
Abstract Background Although conventional open posterior lumbar interbody fusion (open PLIF) is efficacious in management of lumbar spinal instability, concerns exist regarding lengthy hospital stays, blood loss, and postoperative complications. Minimally invasive posterior lumbar interbody fusion (MIS PLIF) may be able to address these concerns, but the research on this topic has not been systematically reviewed. Questions/purposes We performed a systematic review to determine whether MIS PLIF or open PLIF results in (1) better perioperative parameters, including blood loss, operative times, and length of hospital stay; (2) improved patient-reported outcome scores; and (3) improved disc distraction and (4) frequency of reoperation and complications when compared with open PLIF procedures. Methods A literature search of the MEDLINE database identified seven studies that met our inclusion criteria. A total of seven articles were included; quality was assessed using the Methodological Index for Non-Randomised Studies (MINORS) scale. Descriptive statistics were used to describe the included articles. Each author certifies that he or she, or a member of his or her immediate family, has no funding or commercial associations (eg, consultancies, stock ownership, equity interest, patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article. All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research editors and board members are on file with the publication and can be viewed on request. G. S. Sidhu, E. Henkelman, A. R. Vaccaro, T. J. Albert, A. Hilibrand, D. Greg Anderson, J. A. Rihn (&) Rothman Institute & Thomas Jefferson University Hospital, 925 Chestnut Street, Philadelphia, PA 19107, USA e-mail: [email protected]
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Results In most studies, MIS PLIF was associated with decreased blood loss and shorter hospital stay but longer operative times. MIS PLIF resulted in better patient-related outcomes when compared with open PLIF in two studies in the short term, but most of the studies in this review found no short-term differences, and there was no difference at long-term followup in any studies. There was no significant difference in disc distraction. Both techniques appeared to have similar complication rates and reoperation rates. Conclusions Based on the available evidence, which we restricted to prospective and retrospective studies with control groups, but did not include any well-designed randomized trials, MIS PLIF might lead to better perioperative parameters, but there was little evidence for improved patient-reported outcomes in the MIS groups. Randomized controlled trials are needed to compare these two surgical techniques.
Introduction Posterior lumbar interbody fusion (PLIF) is a widely accepted surgical technique for the management of a variety of spinal conditions requiring spinal stabilization and fusion [15, 17, 19, 22]. Compared with posterolateral and lateral approaches, PLIF may be advantageous, providing a wider area of intervertebral interbody graft bone contact surface, improved load-sharing, adequate access for complete decompression of the neural elements, restoration of neural foraminal height, and the ability to restore segmental lordosis at the involved level [1–3, 5, 10]. Multiple studies report a high fusion rate ranging between 89% and 97% with this technique [4, 7, 11, 18, 26, 30, 32]. Although studies have demonstrated the success of conventional, open PLIF, concerns exist regarding the
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morbidity of the procedure, a high procedural blood loss, postoperative complications, and lengthy hospital stays [12–14]. To address such concerns related to posteriorbased, open spinal surgery, Foley et al. [8] developed a tubular retractor system for microdiscectomy in 1994. Later on, the tubular retractor system was modified, which, along with the development of advanced surgical instrumentation and optical systems, led to the development of minimally invasive posterior lumbar interbody fusion (MIS PLIF) technique. Preliminary evidence in the literature demonstrates the MIS PLIF approach to be associated with decreased iatrogenic muscle injury, less blood loss, and less postoperative pain compared with the traditional approach. These benefits could potentially yield earlier mobilization, shorter hospital stay, and shorter functional recovery. However, MIS approaches are themselves associated with some problems. MIS PLIF may be associated with an increased operative time and hence increased radiation [24, 27]. The learning curve for all MIS is steep, which coupled with limited visibility makes it a technically demanding procedure [18, 27]. Multiple studies report a high complication rate during the learning stage [6, 16, 23]. Recently, a number of comparative studies have compared the effectiveness of open PLIF and MIS PLIF for degenerative spinal conditions [4, 7, 11, 18, 20, 26, 28]. However, consensus regarding superiority of either approach is lacking as a result of inconsistent conclusions in the various studies. We therefore performed a systematic review to evaluate whether MIS PLIF was associated with (1) better perioperative parameters, including operative time, intraoperative blood loss, and postoperative drainage; (2) improved clinical outcomes (Oswestry Disability Index [ODI], visual analog scale [VAS], and Prolo score [21]); (3) improved disc distraction; and (4) lower frequency of reoperation and complications.
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articles with the longest followup were included. The following inclusion criteria were applied: (1) the study included a comparative design (MIS PLIF versus open PLIF). As a result of variability in MIS techniques used among multiple studies, only studies that used a tubular retractor for pedicle screw insertion were considered true MIS approaches. In brief, the PLIF technique defined involved decompression of the affected nerve root, reduction of the listhesis, and posterior interbody fusion and was distinctively stated to be performed differently from a transforaminal lumbar interbody fusion procedure; (2) the study population consisted of adult patients with degenerative lumbar conditions (spondylolisthesis [degenerative and isthmic] and spinal stenosis); (3) at least one of the outcomes needed to be reported: perioperative results (operative time, blood loss, hospital stay, etc), pain or disability improvement, complications, or reoperations; and (4) the study had a minimum recorded followup of 6 months. Articles were excluded for any of the following characteristics: (1) article included less than five patients in any of the two groups; (2) patients with reported spinal deformity, trauma, or spinal tumors; and (3) case reports, case series that did not include a comparator or historical control group, editorials, and commentary and case reports. The search yielded a total of 101 articles (Fig. 1). Of these, 24 articles were screened after excluding 77 articles based on the titles and the abstracts. Of the stated articles,
Materials and Methods Search Strategy and Criteria Two independent reviewers (GSS, JAR) performed a review of the literature on May 24, 2013, using Medline, Scopus, and the Cochrane Register of Controlled Trials database. Studies were limited to those published in the English language. The following keywords were searched for by combining the term ‘‘posterior lumbar interbody fusion’’ or ‘‘PLIF’’ with ‘‘MIS’’, ‘‘minimally invasive’’, or ‘‘minimally invasive spine surgery’’. No randomized controlled trials currently exist in the literature; therefore, nonrandomized comparative prospective and retrospective studies with historical control groups were included. Additionally, bibliographies of retrieved articles were also searched. For articles from the same institution, only the
Fig. 1 Flowchart for study selection is shown.
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Table 1. Details of included studies Study or subgroup
Year
Country
Number of patients
Design
Mean followup (months)
MINORS scale
Park and Ha [20]
2007
South Korea
62
PCT
12 (minimum)
18
Fan et al. [7]
2010
China
59
PCT
12
19
Tsutsumimoto et al. [26]
2009
Japan
20
PCT
24 (minimum)
15
Ntoukas and Muller [18]
2010
Germany
40
RCT
12
13
Wang et al. [28]
2010
USA
74
RCT
14
12
Jang et al. [11]
2011
South Korea
20
PCT
6
16
Cheung et al. [4]
2013
Australia
52
PCT
36
17
MINORS = Methodological Index for Non-Randomised Studies; the global ideal score is 24 for comparative studies; PCT = prospective comparative study; RCT = retrospective comparative study.
13 articles were included after full-text review and bibliographic search. Four studies were not included because the data were unseparable from other operative approaches (for example, transforaminal lumbar interbody fusion, extreme lateral interbody fusion) in terms of differentiating individual approach-related patient data. Two studies were later excluded because they used a minimally invasive open approach in which the pedicle screw insertion site was openly visualized. This left a total of seven studies (Table 1).
exposure time, and hospital stay; (6) patient-reported outcome score improvement at last followup including VAS, ODI, and SF-36; (7) disc height; and (8) complication types and complication frequencies. Both total and specified complication rates were extracted. We referred to the previous published review to categorize specified complication types [25]. Data were extracted from each of the selected papers independently by two evaluators (JAR, GSS); there was complete agreement regarding inclusion or exclusion in all cases. Given the lack of prospective randomized trials, a meta-analysis was not attempted. Our systematic review was performed in accordance with the PRISMA guidelines.
Study Quality Quality of level of evidence rating was assigned to each article independently by two reviewers (GSS, JAR) using standard criteria for therapeutic studies as defined for orthopaedic surgical literature [31]. Methodological quality was estimated using the Methodological Index for NonRandomised Studies (MINORS), which is a validated instrument designed for assessment of the methodologic quality of nonrandomized studies in surgery (Table 1). The global ideal score is 24 for comparative studies on a MINORS scale.
Data Extraction We extracted data based on the following categories: (1) study year, country, and study design; (2) basic study characteristics including patients’ inclusion/exclusion criteria, enrolled number, age, and sex proportion; (3) baseline comparison information of confounding factors such as sex, age, height, weight, body mass index, diagnosis, surgical level, insurance, education, smoking status, alcohol use, workers compensation, and concomitant diseases; (4) surgical information, instrumentation, and bone graft; (5) perioperative parameters such as operative time, intraoperative and postoperative blood loss, intraoperative radiograph
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Results Perioperative Parameters Five studies reported operative time; four of the five provided the mean and SD (Table 2). In four studies, MIS PLIF required a longer operative time, whereas in one study, open PLIF required more time. Six studies provided information about length of hospital stay (Table 3). In all studies, MIS PLIF cases reportedly had a shorter length of stay compared with open PLIF procedures. Five studies assessed intraoperative blood loss with a quantifiable mean and SD (Table 4). All studies reported lower intraoperative blood loss in the MIS PLIF group. Postoperative drainage was documented in two studies, which reported lower postoperative drainage for the MIS PLIF group (Table 5).
Clinical Outcomes All seven studies had certain clinical outcome parameters by which they assessed improvement in function and decrease in disability. In all studies, there was a reduction in overall VAS, ODI, and Prolo outcome scores at final followup compared with baseline, demonstrating
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Table 2. Average surgical time (minutes) Study or subgroup
MIS PLIF
Open PLIF
Mean
SD
Total (number)
Mean
SD
Total (number) 31
Fan et al. 2010 [7]
203.6
36.6
28
194.5
47.2
Cheung et al. 2013 [4]
220*
202–288*
21
203*
175–260*
23
Ntoukas and Muller, 2010 [18]
275
73
20
152
38
20
Park and Ha, 2007 [20]
191.7
37.7
32
148.8
24.2
29
Tsutsumimoto et al. 2009 [26]
148.3
48.4
10
155.8
33.5
10
*
Study reported median and interquartile range; statistical significance (p\0.05); MIS = minimally invasive surgery; PLIF = posterior lumbar interbody fusion.
Table 3. Average length of hospital stay (days) Study or subgroup
MIS PLIF
Open PLIF
Mean
SD
Total
Mean
SD
Total
Fan et al. 2010 [7]
9.5
2
28
15.2
3.4
31
Cheung et al. 2013 [4]
4*
3–5*
23
7*
5–8*
24 20
Ntoukas and Muller, 2010 [18]
5
2.2
20
10
3.1
Park and Ha, 2007 [20]
5.3
2.6
32
10.8
2.5
29
Wang et al. 2010 [28]
3.9
1.06
44
4.8
1.42
15
Study reported median and interquartile range; statistical significance (p\0.05); MIS = minimally invasive surgery; PLIF = posterior lumbar interbody fusion.
*
Table 4. Average intraoperative blood loss (mLs) Study or subgroup
MIS PLIF
Open PLIF
Mean
SD
Total
Mean
SD
Total
Fan et al. 2010 [7]*
496.4
217.2
28
887.7
555.3
31
Ntoukas and Muller, 2010 [18]*
135
98
20
432
151
20
Park and Ha, 2007 [20]*
432.8
294.8
32
737.9
224.3
29
Tsutsumimoto et al. 2009 [26]
282
259.8
10
352.6
304.6
10
Wang et al. 2010 [28]*
145
73
44
400
116
15
*
Statistical significance (p \ 0.05: MIS = minimally invasive surgery; PLIF = posterior lumbar interbody fusion.
Table 5. Average postoperative drainage (mLs) Study or subgroup
Fan et al. 2010 [7]*
MIS PLIF
Open PLIF
Mean SD
Total Mean SD
Total
146.7 61.9
28
31
Park and Ha, 2007 [20]* 175
162.2 32
344.3 114
482.9 165.3 29
*
Statistical significance (p \ 0.05); MIS = minimally invasive surgery; PLIF = posterior lumbar interbody fusion.
significant improvement in function as a result of PLIF with both the MIS and open approaches. To provide an overall assessment of clinical improvement, a descriptive analysis was used (Table 6). Descriptively, two studies reported better outcome for the MIS PLIF group versus the
open PLIF group based on back pain VAS, ODI, and low back pain score parameters. Two studies documented better VAS/ODI score for MIS PLIF versus open PLIF at 1 and 3 months followup, respectively. In both studies, no difference in outcome scores between groups was observed at long-term followup. However, five studies did not find a benefit to MIS PLIF over open PLIF in terms of validated outcomes scores, including the VAS (Table 7).
Radiological Outcome Three studies compared for a possible difference in disc distraction between the MIS PLIF and the open PLIF
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123 Percent slip reduction rate greater in open PLIF versus MIS PLIF group (p = 0.01); both groups exhibited solid fusion at 1 year No difference in disc distraction between groups at 1-year followup
MIS PLIF group with less postoperative back pain (p \ 0.001) and lower postoperative ODI score (p = 0.001) versus open PLIF
Both groups significantly improved JOA score compared with baseline; no significant difference in improvement between the two groups at 2-year followup
VAS and ODI scores lower (p \ 0.05) at 3 months for MIS PLIF versus open PLIF; no significant difference between groups at 1-year followup
Mean change in modified PROLO score showed no difference between groups for one-level procedures; mean improvement in modified PROLO score for two-level MIS PLIF versus open PLIF (p \ 0.007)
MIS PLIF group at 1 month had lower back pain VAS score (p = 0.037) compared with open PLIF; no significant difference between groups for back pain VAS, leg pain VAS, and mean low back outcome score at long-term followup
No difference in VAS back and leg pain SF-36 scores at long-term followup; both groups demonstrated improved score compared with base line (p \ 0.05)
Fan et al. 2010 [7]
Tsutsumimoto et al. 2009 [26]
Ntoukas and Muller, 2010 [18]
Wang et al. 2010 [28]
Jang et al. 2011 [11]
Cheung et al. 2013 [4]
VAS = visual analog scale; MIS = minimally invasive surgery; PLIF = posterior lumbar interbody fusion; ODI = Oswestry disability index; JOA = Japanese Orthopaedic Society; NA = not applicable.
NA
NA
NA
NA
Postoperative multifidus atrophy was significantly less in MIS PLIF versus open PLIF at final followup
Multifidus atrophy less in MIS PLIF group (p \ 0.001); VAS and ODI score at final followup correlated with percent change in cross-sectional area of all measured multifidus muscles
NA
Multifidus changes at long-term followup
Sidhu et al.
Postoperative disc height difference was not statistically significant at long-term followup between open PLIF and MIS PLIF groups
NA
NA
NA
No difference (p = 0.398) in disc distraction at 1-year followup; average subsidence of disc space similar (p = 0.852) in both groups; solid fusion was achieved (p = 1) in both groups at 1 year
Mean VAS for postoperative back pain was lower (p \ 0.05) for MIS PLIF versus open PLIF at 1 year; PROLO outcomes were similar (p = 1) between groups
Park and Ha, 2007 [20]
Fusion outcome
MIS group versus open group change in outcome
Study or subgroup
Table 6. Descriptive clinical and radiographic outcomes
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Table 7. Average VAS score at final followup Study or subgroup
MIS PLIF
Open PLIF
Mean SD
Total Mean SD
Total
Fan et al. 2010 [7]
1.8
0.6
28
3.4
0.5
31
Ghahreman et al. 2010 [9]
2*
1–5* 25
2*
0–4* 27
Ntoukas and Muller, 2010 [18] Park and Ha, 2007 [20]
2
1.1
20
2.5
2.5
20
2.1
1.4
32
3.8
1.8
29
*
Study reported median and interquartile range; statistical significance (p \ 0.05); VAS = visual analog scale; MIS = minimally invasive surgery; PLIF = posterior lumbar interbody fusion.
groups (Table 6). There was no difference in disc distraction between the groups in the three studies that assessed this endpoint. Fusion rate was inadequately assessed in the studies and could not be compared.
Reoperation and Complication Frequencies Four main complication types including instrumentation failure, dural tear, infection, and reoperation rate were observed in the eligible studies. No differences were detected between open and MIS PLIF in terms of complication types or frequencies.
Discussion PLIF has been documented in multiple studies to achieve a satisfactory fusion rate, restore disc height, and achieve satisfactory clinical outcomes on long-term followup [9]. However, the procedure has drawbacks with a long midline incision and wider exposure perhaps increasing intraoperative blood loss and resulting in injury to the supporting paraspinal musculature. MIS PLIF, a relatively newer approach, may reduce approach-related morbidity and early results in terms of pain and function. However, the data in support of this contention derive mainly from case series with the kinds of biases in study design usually associated with that sort of retrospective analysis. We therefore sought to perform a systematic review of comparative studies (prospective and retrospective) to evaluate MIS and open PLIF in terms of perioperative parameters, validated outcomes scores, key radiological endpoints, and complications. Our systematic review has multiple weaknesses. First, because the roster of prospective studies is small, retrospective comparative studies had to be included. Most studies had methodological defects, including but not limited to nonconsecutive enrollment of patients,
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inadequate baseline comparisons, inadequate measurement of clinical outcomes, and reported complications. Some studies did not use contemporary validated outcome measures [7, 11]. Considerable heterogeneity was present in the data. This could have been because of incomplete data recording in individual studies, variable patient characteristics, and the diverse technical specification of each study in question. Despite this, our systematic review still provides some value to the clinician in light of the absence of high-quality randomized controlled trials. Second, the minimally invasive and open surgical techniques used in these studies were quite variable, introducing limitation in making general conclusions because each approach may have had unique issues related to clinical outcomes and complications. Third, the description of disease characteristics (isthmic versus degenerative spondylolisthesis versus spinal stenosis) was very nonuniform. In addition, a detailed description of bone graft and substitutes was not consistently documented. Lastly, the documentation and reporting of complications related to surgery were extremely variable. There is no consensus or standard system of documenting complications and, therefore, these data may not provide comprehensive information regarding the potential risks of MIS PLIF surgery. Overall, MIS PLIF was reported to result in decreased intraoperative blood loss, decreased postoperative drainage, and a decreased length of stay, but operative time was higher in MIS PLIF. This represents a major issue with MIS surgery overall. Although studies report it to decrease intraoperative blood loss and length of stay, higher operative time increases the time the patient is under anesthesia as well as higher radiation exposure from multiple fluoroscopic images required for adequate screw placement. This is complicated by the high learning curve required for performing MIS techniques overall. Another open question that remains is the actual costs associated with each procedure. Wang et al. [29] reported lower costs by evaluating hospital charges using an MIS PLIF approach for one-level and two-level procedures. Although MIS procedures may reduce costs by reducing inpatient stay, the increased operative time may influence the number of procedures per day, especially in high-volume surgical centers. All studies in our systematic review demonstrated decreased pain and improved function from baseline after PLIF surgery in a majority of the patients with both approaches, but superiority of MIS PLIF in terms of patient-reported outcomes scores compared with open PLIF was not proven here. Two studies in our systematic review did demonstrate improved early outcome scores in MIS PLIF over open PLIF; however, this effect was noticed during the early timeframe postoperatively and became negligible at [ 1-year followup. However, five studies did not find a benefit to MIS PLIF over open PLIF
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in terms of validated outcomes scores [4, 11, 20, 26, 28]. This suggests MIS may result in a quicker decrease in postoperative pain and functional recovery, but no studies in our review evaluated return to work status for patients. Cheung et al. [4] followed patients for a timeframe between 3 and 7 years and reported no difference in all clinical parameters between both groups. The reoperation rate for both MIS PLIF and open PLIF techniques was very low but quite variable across the studies we identified. The definition of ‘‘complication’’ was different in each study and hence may account for its variability. It should be noted that for a specific complication type, the data revealed no apparent differences between MIS PLIF and open PLIF techniques. This may have been because all our studies were done at single spine centers that are well established in MIS procedures. A larger multicenter study with a uniform complication recording tool could have better elicited the difference in the rate of complications between MIS PLIF and open PLIF techniques. The low rate of complications does suggest all PLIF procedures are relatively safe with minimal risk for major perioperative complications. In conclusion, our systematic review suggests MIS PLIF is associated with less operative blood loss and shorter hospital stay. However, we found no apparent differences between the approaches in terms of patient-reported outcome scores, the frequency of complications, and the efficacy in terms of disc distraction. A number of unresolved issues require answers. Uniform validated instruments of documenting clinical outcomes and reporting perioperative complications are needed to assist more refined clinical investigation. Large patient populations must be evaluated to better answer clinically relevant questions. Lastly, clinical randomized trials are needed to determine the relative efficacy of MIS and open PLIF techniques.
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