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Transforaminal lumbar interbody fusion (TLIF) is a commonly per-formed spine surgery. Incision

length for a single-level TLIF ranges from 7 to 10 cm, depending on the patient’s size and the surgeon’s preference and skills.1-3

Techniques such as percutaneous pedicle screw placement and expandable retractor system have been applied in TLIF pro-cedures in the past decade, with the goal of lessening approach-related morbidity. However, such minimally invasive TLIF procedures require 4 to 7 incisions, and one of these incisions must be approximately 4 cm in length so that an expandable retrac-tor can be inserted.4-9

With advances in navigation technology, navigated TLIF has become an option for spine surgeons. The current study presents a navigated TLIF technique that requires only a 4-cm incision to accomplish a sin-gle-level TLIF. Compared with conven-tional TLIF, navigated TLIF could result in smaller incisions, less intraoperative blood loss, and shorter hospital stay; however, it may increase operative time and incidence of complications. The authors performed the current study to examine the differences between conventional and navigated TLIF.

SEPTEMBER/OCTOBER 2016 | Volume 39 • Number 5

Navigation Makes Transforaminal Lumbar Interbody Fusion Less InvasiveYu Wang, MD, PhD; Yongkai hu, MD; hong Liu, MD; ChunDe Li, MD; hong Li, MD; XiaoDong Yi, MD

The authors are from Peking University First Hospital, Beijing, China.

The authors have no relevant financial rela-tionships to disclose.

Correspondence should be addressed to: Yu Wang, MD, PhD, Peking University First Hospi-tal, Xshiku St 8, Beijing, China 100034 (06340@pkufh.cn).

Received: December 23, 2015; Accepted: March 28, 2016.

doi: 10.3928/01477447-20160517-01

abstract

The current study presents a navigated transforaminal lumbar interbody fu-sion (TLIF) technique that requires only a 4-cm incision to accomplish a single-level TLIF. The authors compared its efficacy and efficiency with those of conventional TLIF. Forty patients who were indicated for single-level lum-bar fusion were included and randomized to either the navigated-TLIF group or the conventional-TLIF group. Intraoperative blood loss, operative time, incision length, complications, bed rest period, and length of hospital stay were recorded. Oswestry Disability Index (ODI) scoring was also performed for each patient preoperatively and 3 months and 2 years postoperatively. In-cision length was significantly shorter in the navigated-TLIF group than in the conventional-TLIF group (4.2 vs 8.3 cm, respectively; P=.001). Accordingly, intraoperative blood loss was also significantly less in the navigated-TLIF group than in the conventional-TLIF group (122.5 vs 220.5 mL, respectively; P=.049). There was no significant difference in total operative time between the 2 groups (134.4 vs 124.5 minutes; P=.226). The navigated-TLIF group had a significantly shorter bed rest period and length of hospital stay com-pared to the conventional-TLIF group. Incision length decreased with time; at final follow-up, average incision length had decreased from 4.2 to 3.7 cm in the navigated-TLIF group and from 8.3 to 7.7 cm in the conventional-TLIF group. Average ODI score improved significantly in both groups immediately postoperatively and was maintained in the following 2 years. Navigation can make single-level TLIF less invasive. Compared with conventional TLIF, navi-gated TLIF proved to be superior with regard to incision length, intraoperative blood loss, bed rest period, and length of hospital stay. [Orthopedics. 2016; 39(5):e857-e862.]

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Materials and MethodsThe indication for navigated and con-

ventional TLIF is the same: symptomatic single-level degenerative disk disease. Navigated TLIF uses 1 incision approxi-mately 4 cm long. Through this incision, pedicle screw placement, decompression, diskectomy, cage insertion, and bone grafting can be performed. Accordingly, because of the incision’s small size, in-traoperative blood loss can be decreased. Another advantage of navigated TLIF is

that the pedicle screws are inserted under the guidance of infrared navigators, which not only make the insertion more accurate but also completely avoids exposure to ra-diation by the operating room personnel.

Surgical Technique for Navigated Transforaminal Lumbar Interbody Fusion

Two senior surgeons (Y.W., H.L.) with more than 20 years of experience in spinal surgery performed all TLIF proce-dures.

Navigated TLIF is performed with the patient under general anesthesia and in the prone position on a carbon-fiber operating table. A 4-cm longitudinal median inci-sion is made. Detachment of the paraver-tebral muscles and exposure of the lami-nae are performed bilaterally.

First, a patient tracker is fixed to the spinal process (Figure 1), followed by scanning using a 3-dimensional (3-D) C-arm (Figure 2). After scanning, the im-age data are transferred within 30 seconds

Figure 1: The pedicles of L4 and L5 are located with fluoroscopy (A). Two transversal lines (arrows) are drawn on the skin to mark the location of the pedicles of L4 and L5 (B). A 4-cm longitudinal median incision is made (C). An expandable retractor and navigated instruments are used in the procedure (D). A patient tracker is fixed to the spinal process after exposure (E).

Figure 2: When the patient tracker has been fixed to the spinal process, scanning is performed with a 3-dimensional C-arm (A). After scanning, the 3-dimensional reconstruction images are available for viewing (B). Both the navigated tactile awl (arrow) and the spine are tracked in real time, and hence the trajectories can be made under the guidance of the navigator (C). A navigated tactile awl (arrow) is used to establish the trajectories for the pedicle screws (D).

Figure 3: When a trajectory has been established, a screw is inserted (A). The operator always has the visual of the screw during the course of screw insertion (B). When all 4 screws have been inserted, another round of 3-dimensional scanning is performed to check the screw positions (C). After scanning, the screws are shown in 3-dimensional reconstruction images and their positions are clearly visualized (D).

Figure 4: A retractor is inserted to give the operator a visual of the laminae (A). De-compression can be performed under direct vision (B). Cage insertion is performed (C). The incision measures 4 cm after closure (D).

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from the 3-D C-arm to the navigation workstation, allowing the lumbar spine of the patient to be tracked by the navigation system in real time. Meanwhile, the navi-gated instruments are also being tracked.

Second, under the guidance of the navigator, 4 pedicle screws (multi-axial, 6.5-mm diameter) are inserted one by one. When a screw is being inserted, the mus-cles are pulled laterally, and the operator always has the visual of the entry point (Figure 3). When all 4 pedicle screws have been inserted, another 3-D scan is performed to check the position of each screw. If all the screws are shown to be well placed, the patient tracker is removed from the spinal process.

Finally, a retractor is inserted to give the operator a visual of the laminae, through which decompression, diskec-tomy, cage insertion, bone grafting, rod instrumentation, and screw nut locking are performed (Figure 4).

Navigated Versus Conventional Transforaminal Lumbar Interbody Fusion

A comparative study was performed between navigated and conventional TLIF. Forty patients who were indicated for single-level fusion were included and randomized to either the navigated-TLIF group or the conventional-TLIF group. Blinded randomization was done us-ing Filemaker Pro (Filemaker Inc, Santa Clara, California), a commercially avail-able database package.10 Exclusion cri-teria included previous lumbar surgery, severe osteoporosis, motor deficit, cauda equina syndrome, or spondylolisthesis greater than grade I. Intraoperative blood loss, operative time, incision length, com-plications, bed rest period, and length of hospital stay were recorded. Oswestry Disability Index (ODI) scoring was also performed for each patient preoperatively and 3 months and 2 years postoperatively.

Statistical AnalysisDistributions of variables were presented

as mean±SD. A t test and chi-square test

were used to detect differences in each pa-rameter between the 2 groups. A P value of less than .05 was considered significant. Statistical analyses were performed using STATA 11.0 software (Stata Corp, College Station, Texas).

resultsAll 40 patients were followed for at

least 24 months. Demographic data were compared between the navigated-TLIF

and conventional-TLIF groups (Table 1). The results showed no significant differ-ences between the 2 groups in terms of patient age, height, and weight.

Operative data were compared between the groups (Table 2). Incision length was significantly shorter in the navigated-TLIF group than in the conventional-TLIF group (4.2 vs 8.3 cm, respectively; P=.001). Ac-cordingly, intraoperative blood loss was significantly less in the navigated-TLIF

Table 1

Patient DemographicsDemographic Navigated-TLIF Group Conventional-TLIF Group Pa

Patients, No. 20 20

Age, mean±SD, y 50.6±12.7 51.5±10.0 .846

Sex, M/F, No. 7/13 10/10 .16

Height, mean±SD, cm 166±8.2 165.4±7.0 .854

Weight, mean±SD, kg 70.3±14.3 69.3±11.4 .851

ODI score, mean±SD 0.52±0.11 0.34±0.10 .08

Fusion level, No.

L4-L5 12 17 .06

L5-S1 8 3

Abbreviations: F, female; M, male; ODI, Oswestry Disability Index; TLIF, transforaminal lumbar interbody fusion. aP<.05 significant; t test or chi-square test.

Table 2

Operative Data

Operative DataNavigated-TLIF

GroupConventional-TLIF

Group P

Incision length, mean±SD, cm 4.2±0.2 8.3±1.5 .001a

Blood loss, mean±SD, mL 122.5±100.0 220.5±191.0 .049a

Operative time, mean±SD, min

Total time 134.4±27.9 124.5±23.0 .226

Exposure 24.4±10.4 26.7±6.2 .399

Screw placement 23.5±7.6 21.4±8.4 .413

3-D scanning 9.7±3.0 0±0 N/A

Decompression 64.2±22.1 53.6±16.6 .095

Closure 12.8±5.2 22.9±4.8 .001a

Abbreviations: 3-D, 3-dimensional; N/A, not applicable; TLIF, transforaminal lumbar interbody fusion. aP<.05 significant; t test.

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group than in the conventional-TLIF group (122.5 vs 220.5 mL, respectively; P=.049). There was no significant difference in total operative time between the 2 groups (134.4 vs 124.5 minutes; P=.226).

Postoperative data were also com-pared between the groups (Table 3). The navigated-TLIF group had a significantly shorter hospital stay and bed rest period compared with the conventional-TLIF group. There was no significant differ-ence in postoperative blood loss between the 2 groups. Incision length decreased with time in both groups (Figure 5); at

final follow-up, average incision length had decreased from 4.2 to 3.7 cm in the navigated-TLIF group and from 8.3 to 7.7 cm in the conventional-TLIF group.

Clinical outcomes were compared be-tween the groups (Figure 6). Average ODI score improved significantly in both groups immediately postoperatively and was main-tained in the following 2 years. The compli-cations that occurred are listed in Table 4.

discussionAccording to this study’s results,

navigated TLIF had several advantages

compared with conventional TLIF. The navigated-TLIF group showed signifi-cantly less intraoperative blood loss and shorter hospital stay. These findings are in accordance with previous studies (Ta-ble 5).2-9 Most of these previous studies showed the superiority of minimally inva-sive TLIF over conventional TLIF. Opera-tive time for navigated and conventional TLIF was comparable, which is also in agreement with previous studies (Table 5).2-9 Regarding clinical outcomes, both groups showed significant ODI score im-provements, which agreed with previous studies.3-9

In the current study, average incision length in conventional TLIF was 2 times that in navigated TLIF (8.3 vs 4.2 cm, respectively; P=.001), which was a ma-jor advantage of navigated TLIF. Inci-sion length decreased with time; at final follow-up, average incision length had decreased from 4.2 to 3.7 cm in the navi-gated-TLIF group and from 8.3 to 7.7 cm in the conventional-TLIF group.

Several minimally invasive TLIF pro-cedures have been developed to lessen ap-proach-related morbidity. Schwender et al1 presented the first clinical series reporting minimally invasive TLIF. A paramedian, muscle-sparing approach was performed through a tubular retractor. Facetectomy, diskectomy, and interbody cage insertion were performed through the tube. Bilater-al percutaneous pedicle screw-rod place-ment was then accomplished with the Sex-tant system (Medtronic Inc, Minneapolis, Minnesota). Scheufler et al3 performed a clinical study on percutaneous TLIF. De-compression, diskectomy, and interbody cage insertion were performed through tu-bular retractors, followed by percutaneous pedicle screw-rod fixation. Isaacs et al2 developed microendoscopic TLIF. Hemi-laminectomy, unilateral facetectomy, and microdiskectomy were performed using microendoscopy-assisted TLIF through a working channel. Bilateral percutaneous pedicle screws were then inserted.

All of these minimally invasive tech-

Table 3

Postoperative Data

Postoperative DataNavigated-TLIF

GroupConventional-

TLIF Group P

Incision length at final follow-up, mean±SD, cm

3.7±0.2 7.7±1.4 .001a

Postoperative blood loss, mean±SD, mL

Day 1 119.5±75.8 135.8±85.9 .530

Day 2 68±31.7 83.5±51.2 .257

Day 3 49.3±22.0 57.8±30.2 .316

Total 236.8±109.5 277±150.1 .339

Time to mobilization, mean±SD, d 2.1±0.4 3.9±0.3 .001a

Length of hospital stay, mean±SD, d 8.8±2.1 12.3±2.3 .018a

3-mo ODI score 0.12±0.02 0.09±0.02 .756

Abbreviations: ODI, Oswestry Disability Index; TLIF, transforaminal lumbar interbody fusion. aP<.05 significant; t test.

Figure 5: Axial (left) and sagittal (right) magnetic resonance images showing disk herniation at L5/S1 (arrows) in a 65-year-old woman (A). Anteroposterior (left) and lateral (right) radiographs taken after navigated TLIF (B). At 2-year follow-up, incision length measured 3.5 cm (C).

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niques require 4 to 7 incisions, one of which must be approximately 4 cm (range, 3.5-4.5 cm) so that an expand-able retractor can be accommodated. The technique reported in the current study requires only a single 4-cm incision, which is one of its advantages over other minimally invasive techniques. However, a small skin incision doesn’t necessarily mean a small muscle injury. Navigated TLIF still involves muscle detachment and ligamentous disruption, which should be improved in the future. A small skin incision may be a problem for navigation because the patient tracker might be mov-ing when the wound is being retracted lat-erally. As such, the patient tracker must be fixed firmly, and care must be taken when retracting the wound.11,12

Incision length could be further de-creased if the pedicle-screw direction is well designed.10 Another important advan-tage of navigated TLIF is that the pedicle screws are inserted under the guidance of infrared navigators, which not only make the procedure safer but also completely avoids exposure to radiation by the oper-ating room personnel.

conclusionNavigation makes single-level TLIF

less invasive. Compared with convention-al TLIF, navigated TLIF proved to be su-

perior with regard to intraoperative blood loss, length of hospital stay, and incision length.

references 1. Schwender JD, Holly LT, Rouben DP, Foley

KT. Minimally invasive transforaminal lum-bar interbody fusion (TLIF): technical feasi-bility and initial results. J Spinal Disord Tech. 2005; 18(suppl):S1-S6.

2. Isaacs RE, Podichetty VK, Santiago P, et al. Minimally invasive microendoscopy-assisted

transforaminal lumbar interbody fusion with instrumentation. J Neurosurg Spine. 2005; 3(2):98-105.

3. Scheufler KM, Dohmen H, Vougioukas VI. Percutaneous transforaminal lumbar inter-body fusion for the treatment of degenerative lumbar instability. Neurosurgery. 2007; 60(4 suppl 2):203-212.

4. Park Y, Ha JW. Comparison of one-level posterior lumbar interbody fusion performed with a minimally invasive approach or a traditional open approach. Spine (Phila Pa 1976). 2007; 32(5):537-543.

5. Dhall SS, Wang MY, Mummaneni PV.

Figure 6: Average Oswestry Disability Index (ODI) score improved significantly in both the navigated–transforaminal lumber interbody fusion (TLIF) group and the conventional-TLIF group immediately post-operatively and was maintained in the following 2 years. There were no significant differences between the 2 groups at any time point recorded. Abbrevia-tion: SD, standard deviation.

Table 4

ComplicationsNo. (%)

Complication Navigated-TLIF Group (n=20) Conventional-TLIF Group (n=20)

Screw malposition 0 1 (5)

Cage migration 0 1 (5)

Dural tear 1 (5) 1 (5)

Hematoma 0 0

Superficial infection 1 (5) 0

Revision surgery 0 0

Abbreviation: TLIF, transforaminal lumbar interbody fusion.

Table 5

Studies Comparing Operative Time, Intraoperative Blood Loss, and Length of Hospital Stay Between Minimally Invasive and

Conventional TLIFMean

Operative Time, minIntraoperative Blood

Loss, mLLength of Hospital

Stay, d

Study MIS Conv MIS Conv MIS Conv

Isaacs et al2 300 276 226 1,147 3.4 5.1

Scheufler et al3 104 132 55 125 N/A N/A

Park and Ha4 192 149 432 737 5.3 10.8

Dhall et al5 199 237 194 505 3 5.5

Fan et al6 204 195 496 887 9.5 15.2

Schizas et al7 348 312 456 961 6.1 8.2

Kotani et al8 174 175 181 453 N/A N/A

Wang et al9 156 145 264 673 10.6 14.6

Current study 134 125 123 221 8.8 12.3

Abbreviations: Conv, conventional; MIS, minimally invasive surgery; N/A, not applicable; TLIF, transforaminal lumbar interbody fusion.

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Clinical and radiographic comparison of mini-open transforaminal lumbar interbody fusion with open transforaminal lumbar interbody fusion in 42 patients with long-term follow-up. J Neurosurg Spine. 2008; 9(6):560-565.

6. Fan S, Hu Z, Zhao F, Zhao X, Huang Y, Fang X. Multifidus muscle changes and clinical ef-fects of one-level posterior lumbar interbody fusion: minimally invasive procedure versus conventional open approach. Eur Spine J. 2010; 19(2):316-324.

7. Schizas C, Tzinieris N, Tsiridis E, Kosmo-poulos V. Minimally invasive versus open transforaminal lumbar interbody fusion:

evaluating initial experience. Int Orthop. 2009; 33(6):1683-1688.

8. Kotani Y, Abumi K, Ito M, Sudo H, Abe Y, Minami A. Mid-term clinical results of minimally invasive decompression and pos-terolateral fusion with percutaneous pedicle screws versus conventional approach for degenerative spondylolisthesis with spinal stenosis. Eur Spine J. 2012; 21(6):1171-1177.

9. Wang J, Zhou Y, Zhang ZF, Li CQ, Zheng WJ, Liu J. Comparison of one-level minimal-ly invasive and open transforaminal lumbar interbody fusion in degenerative and isthmic spondylolisthesis grades 1 and 2. Eur Spine J.

2010; 19(10):1780-1784.

10. Vickers AJ. How to randomize. J Soc Integr Oncol. 2006; 4(4):194-198.

11. Reinshagen C, Ruess D, Walcott BP, Mol-canyi M, Goldbrunner R, Rieger B. A novel minimally invasive technique for lumbar decompression, realignment, and navigated interbody fusion. J Clin Neurosci. 2015; 22(9):1484-1490.

12. Hong X, Liu L, Bao J, Shi R, Fan Y, Wu X. Characterization and risk factor analysis for reoperation after microendoscopic dis-kectomy. Orthopedics. 2015; 38(6):e490-e496.

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