Transforaminal Lumbar Interbody Fusion: Minimally Invasive versus Open

4 Transforaminal Lumbar Interbody Fusion: Minimally Invasive versus Open

MIS: Rory J. Petteys, Anthony Conte, and Faheem A. Sandhu
Open: Jason C. Eck

4.1 Introduction

Lumbar interbody fusion was first described by Cloward1,2 in 1952 via a posterior approach (posterior lumbar interbody fusion [PLIF]), which proved effective in achieving interbody fusion, but required significant nerve root and thecal sac retraction.3 Subsequently, Harms and Rolinger described a less invasive approach in 1982 via transforaminal route (transforaminal lumbar interbody fusion [TLIF]).4 This approach provides a more lateral point of access to the disc space, thus limiting retraction of the neural elements. While clinical outcomes have been favorable with both of these approaches, the amount of muscle dissection and retraction required to expose the spine was thought to adversely affect patient recovery.5,6,7,8,9,10,11 As an alternative to these standard open techniques and with technological advancements in illumination, retractors, and magnification, Foley et al introduced the minimally invasive TLIF (MIS TLIF) in an attempt to reduce muscle damage associated with the subperiosteal exposure.12,13 MIS TLIF has subsequently become a commonly used and effective technique for achieving lumbar interbody fusion.

4.2 Indications of Transforaminal Lumbar Interbody Fusion

Lumbar arthrodesis is generally employed in the treatment of degenerative diseases of the spine including facet arthropathy, spondylolisthesis, degenerative disc disease, and mechanical instability. While lumbar arthrodesis has been shown to be beneficial in degenerative conditions, the benefits of posterolateral versus interbody fusion are less clear. Many advocate inter-body fusion because it permits deformity reduction, indirect decompression, foraminal distraction, and placement of the graft under compression, and is associated with a higher fusion rate among other benefits.12,13,14,15,16,17,18 Therefore, interbody fusion via TLIF or PLIF is indicated when patients present with grade I or II spondylolisthesis with instability and/or foraminal stenosis with radiculopathy, severe degenerative disc disease with back pain, multiple recurrent disc herniation with back pain or radiculopathy, and postlaminectomy kyphosis.19,20 Indications for MIS TLIF do not differ substantially from standard open TLIF, but advantages of MIS TLIF will be discussed below. Higher grades of spondylolisthesis can be treated via an MIS approach, but are associated with technical difficulties. Two-level TLIF is indicated in patients who present with the above conditions at consecutive spinal levels. Contraindications to TLIF include poor bone quality that would make graft subsidence likely, severe spondylolisthesis and scoliosis, and anatomic variations of the foraminal contents, such as conjoined nerve roots or the presence of a foraminal mass.

4.3 Advantages of Minimally Invasive Surgery

Minimally invasive or minimal access techniques offer several advantages over their traditional open counterparts. As mentioned above, the amount of muscle dissection and retraction necessary to expose the spine leads to significant muscle damage and atrophy.5,6,7,8,10,11 MIS techniques do not require the same degree of muscle, fascia, and soft-tissue disruption. In addition, several authors report other advantages, including less intraoperative blood loss, less postoperative pain and narcotic use, earlier ambulation, and decreased length of hospital stay (images Table 4.1).12,13,14,15,16,17,18 As the MIS TLIF procedure becomes more popularized and widespread, numerous studies comparing it to traditional open approaches have been published, most notably over the last several years.

4.4 Surgical Technique in Minimally Invasive Surgery

The patient is brought to the operating room where general endotracheal anesthesia is administered. A Foley catheter is inserted, pneumatic compression devices and neurophysiological monitoring leads placed, and an arterial line may be used if indicated. The patient is then positioned prone on a Jackson flat top table with chest roll(s) to maintain lumbar lordosis. Preoperative antibiotics are then administered. The fluoroscopic arm is then positioned such that the base of the device is on the side opposite the surgeon. The surgeon should stand on the side of the most significant pathology or symptoms.

Using anteroposterior fluoroscopy, the midline is marked on the skin and a parallel line is drawn 4 to 4.5 cm away on the side nearest the surgeon. Then, using lateral fluoroscopy, the correct levels are identified and marked. For two-level TLIF, the incision should span the intervening vertebral body from one disc space to the next along the paramedian line that was previously marked with the incision centered over the pedicle of the middle lumbar level. The patient is then draped after antiseptic is applied and the skin is infiltrated with local anesthetic. The level with the worst pathology or referable symptoms should be addressed first. A small puncture is made with a number 11 blade over the disc space and a Kirschner wire or Steinmann pin is inserted along a slight medial trajectory under fluoroscopic guidance. The goal is to “dock” the wire on the ipsilateral facet joint of the level in question. Once “docked” at the appropriate level, the incision is lengthened to accommodate a 25-mm tubular retractor. Serial dilators are then inserted followed by the tubular retractor, which is secured by a table-mounted arm. Final placement is then confirmed by fluoroscopy.

With the working channel in place, it is important to confirm placement under direct visualization. Ideally, the laminofacet junction should be in the lateral half of the working field and the lateral half of the lamina in the medial field. Electrocautery is then used to clear the field of remaining muscle and soft tissue until the facet and lamina are exposed. The sublaminar plane is defined with curettes and the ligamentum flavum elevated from the underside of the lamina. This will help ensure the ligamentum remains intact during bone removal, thus minimizing the risk of dural injury. A generous hemilaminotomy and facetectomy is then performed with curettes, rongeurs, and high-speed drill, and should extend from the rostral to the caudal pedicle. Bone fragments can be harvested to use later as autograft.


Once bone removal is completed, the remaining ligamentum flavum is removed with curettes and rongeurs. The disc space, traversing nerve root, and thecal sac are now in view and should be carefully identified before proceeding. The thecal sac is gently retracted medially and all epidural veins coagulated so as to further expose the disc space. The disc space is then incised and a thorough discectomy is performed with curettes and rongeurs. The end plates are then prepared with scrapers and rotating rasps to remove all cartilaginous and disc material. Dilators are then employed to distract the disc space, increasing overall disc space height in preparation for the interbody grafting material. The graft may consist of polyether-ether ketone (PEEK), autograft, cadaver allograft, titanium or carbon-fiber cages, or absorbable materials. Graft placement can also be supplemented with recombinant human bone morphogenetic protein.

Once the discectomy is completed, pedicle screws can then be placed under direct visualization. If a two-level TLIF is planned, the retractor is then removed and a Steinmann pin or Kirschner wire is advanced through the skin incision under fluoroscopic guidance toward the facet of the next level to be addressed. Typically, this will require more rostrocaudal angulation than is used for a single-level TLIF. Serial dilators are advanced and the retractor is “docked” at the laminofacet junction in the manner described above. The removal of bone and ligament and discectomy proceeds as described above. A second interbody graft is placed once the discectomy and end-plate preparation is completed. Pedicle screws are then placed at the remaining two levels under direct visualization and a rod is placed. The disc spaces can then be compressed prior to securing the rod. The lumbodorsal fascia and skin are then closed in layers. Percutaneous pedicle screw fixation is then performed on the contralateral side.

4.5 Surgical Technique in Open Surgery

The patient is brought to the operating room and undergoes general anesthesia with endotracheal intubation. The patient is then turned to the prone position on the Jackson table with standard precautions to avoid decubitus ulcers and minimized upper extremity neuropraxia. The patient should be positioned to maintain the normal lordotic lumbar spine curvature. Positioning should allow for intraoperative radiographic imaging to confirm spinal alignment and implant position.

A lateral fluoroscopic image can be obtained to verify the location of the operative levels. A midline posterior incision is made over the operative levels, and the erector spinous muscles subperiosteally elevated to expose the posterior elements of the spine bilaterally. The spinous processes, laminae, facet joints, pars interarticularis, and transverse processes are visible. Self-retaining retractors are placed to maintain exposure and should be released and repositioned at least each hour to maintain adequate soft-tissue perfusion. A lateral image can then be obtained to verify operative levels.

Exposure for the TLIF is achieved by removing the superior and inferior articulating processes of the facet joint and performing a hemilaminotomy and partial resection of the pars interarticularis. This provides a rectangular window through which you can visualize the underlying disc space, lateral edge of the dura, and the exiting nerve root.

The disc space can then be exposed by removing the overlying ligamentum flavum and fatty tissues. With careful nerve root protection, a 15-blade scalpel can then be used to incise the posterolateral annulus. The annulotomy should be large enough to pass the interbody implant after the disc space is final prepared. A lamina spreader can be utilized if needed for further distraction to facilitate passage of instruments into the disc space. A series of curettes and pituitary rongeurs can be used for removal of the disc material. The end plates can be prepared with a variety of curettes and shavers. Meticulous discectomy and end-plate preparation are essential for facilitating interbody fusion. Once the disc space is prepared, trial inter-body spacers are placed to determine the optimal implant size. Implants are available in a wide variety of sizes, shapes, and materials based on surgeon preference. The implant should be selected to maximize the contact of the implant and the prepared end plates. Morselized bone graft is then placed into the periphery of the disc space, followed by placement of the implant. Any previously placed distraction should be removed, and the implant should be assessed for adequate tightness in the interbody space. Any remaining voids in the interbody space can be filled with additional morselized bone graft.

Pedicle screws are then placed bilaterally in the vertebrae above and below the disc to be fused. Placement of the pedicles screws can be performed through a variety of techniques including anatomic placement, fluoroscopically guided placement, or computer navigation–assisted placement. After placement of the pedicles screws, connecting rods are placed, set caps applied, and final tightened to the rods. Anteroposterior and lateral images should be obtained to verify proper placement of the interbody implant and pedicle screws. Decortication of the transverse processes and remaining lamina and placement of additional bone graft allow for a 360° fusion. A standard layered closure is then performed after achieving meticulous hemostasis.

4.6 Discussion of Minimally Invasive Surgery

Low back pain is a common complaint among adults in the United States, and many of these patients require surgical treatment. Lumbar fusion, via TLIF or other techniques, is utilized to treat a variety of conditions, including degenerative disc disease, facet arthropathy, spondylolisthesis, scoliosis, tumors, and fractures. The TLIF approach is a well-established method for achieving circumferential arthrodesis through a single posterior approach, and recent advancements have allowed the procedure to be performed with minimally invasive techniques. However, considerable questions remain as to whether MIS TLIF is superior to standard open TLIF or vice versa.

4.6.1 Level I Evidence in Minimally Invasive Surgery

There are no level I studies available.

4.6.2 Level II Evidence in Minimally Invasive Surgery

Several authors have performed prospective cohort studies comparing MIS and open TLIF, albeit in relatively small cohorts. The largest of these studies by Lee et al21 compared 72 consecutive MIS and 72 consecutive open TLIF patients at a single institution. The authors demonstrated significantly lower blood loss, length of hospital stay, and postoperative narcotic use in patients undergoing MIS TLIF, while operative time and fusion rates were similar. Ghahreman et al,22 Peng et al,23 and Schizas et al24 also demonstrated decreased blood loss and shorter hospital stay in MIS patients, also with similar clinical and radiographic outcomes compared with patients treated with standard open techniques. Ghahreman et al also reported earlier independent ambulation in patients who had MIS TLIF than in patients who had open fusion.22 Shunwu et al25 and Wang et al26 both demonstrated modest improvements in short-term clinical outcomes, that is, visual analog scale (VAS) scores and Oswestry Disability Index (ODI) scores, in patients treated with MIS TLIF over open TLIF. Early experience appeared to show some modest benefits for MIS TLIF in the short term, but overall clinical outcome was essentially unchanged.

More recent studies point to equivalent, with even potential trends toward benefits in long-term clinical outcomes when compared to traditional open TLIF. In the only randomized, nonblinded, control study investigating MIS versus open TLIFs, Wang et al27 showed less sacrospinalis muscle injury with significantly better 3- to 6-month ODI scores in patients undergoing MIS TLIF. Gu et al28 compared 44 patients treated with two-level MIS TLIF versus 38 patients treated with an open two-level procedure, observing similar back and leg VAS scores and ODI scores at an average of 20-month follow-up. Parker et al29 examined a cohort of 100 patients undergoing TLIF, half via a minimally invasive approach. Results at 2 years showed similar pain and quality-of-life scores, with shorter hospital stays and earlier return-to-work periods for patients in the MIS cohort. A prospective study by Rodríguez-Vela et al,30 comparing 3- to 4-year postoperative results of MIS versus open TLIF patients, showed similar North American Spine Society (NASS) lumbar spine and VAS back pain scores, with a trend toward lower ODI scores in the MIS group. Wong et al31 compared 4-year postoperative results in 144 patients undergoing MIS TLIF versus 54 patients undergoing open TLIF. Both groups showed similar fusion rates, with the MIS group exhibiting improvements in estimated blood loss (EBL), shorter operative times, and lower infection and complication rates. The MIS group showed a significant improvement in VAS back pain scores at the 4-year mark when compared to the open group, with a 15% better ODI score at that time. In a meta-analysis by Khan et al32 comparing surgical outcomes for MIS versus open TLIF procedures, the authors found improvements in length of hospital stay, average blood loss, complication rates, and long-term VAS back scores (minimum > 1 year postoperatively).

4.6.3 Level III and IV Evidence in Minimally Invasive Surgery

To date, there has been no level I study comparing MIS and open TLIF, although a number of level III/IV retrospective studies have been performed. Several studies since the initial report by Foley et al have also demonstrated benefits of MIS TLIF over standard open techniques in head-to-head comparison.

Several retrospective cohort studies appear in the literature comparing MIS and standard open TLIF. Scheufler et al33 compared percutaneous TLIF in 43 patients with mini-open TLIF in 51 patients. They demonstrated similar operative times and fusion rates, but statistically significant reductions in blood loss and postoperative pain in patients who had MIS TLIF procedures.33 There were no differences in clinical outcomes at 8 and 16 months as measured by standard questionnaires.

In a study of mini-open TLIF versus open TLIF with 21 patients in each group, Dhall et al34 also showed significantly less blood loss and hospital stay in mini-open patients, while fusion rates and overall clinical outcomes were similar. However, there were two cases of neurologic injury and two cases of instrumentation malpositioning requiring revision in the mini-open group. Isaacs et al15 performed a comparative analysis of 20 patients treated with endoscopically assisted MIS TLIF and 24 with standard open techniques. The authors demonstrated significant reductions in operative blood loss (226 vs. 1,147 mL), postoperative blood transfusion, length of hospital stay (3.4 vs. 5.1 days), and postoperative analgesia use in patients treated with MIS TLIF; clinical and radiographic outcomes were similar. In a 2010 meta-analysis, Wu et al35 reviewed fusion rates of MIS versus open TLIF patients and found comparable results (MIS: 94.8%; open: 90.9%). Furthermore, a multicenter retrospective study by McGirt et al36 of 5,170 patients treated with either MIS or open TLIF showed that surgical site infections were less common in patients treated with MIS techniques, especially for multilevel procedures. A recent review by Habib et al,37 which included seven articles directly comparing MIS and open TLIF, found operative time to be 220 minutes for MIS TLIF and 218 minutes for open TLIF. Furthermore, blood loss was found to be 282 and 693 mL, and hospital stay 5.6 and 8.1 days, for MIS TLIF and open TLIF, respectively.

Several retrospective cohort studies have displayed the improvement in pain reduction and functional status in the short-term postoperative period for patients undergoing MIS TLIF. Cheng et al38

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Jan 15, 2020 | Posted by in ORTHOPEDIC | Comments Off on Transforaminal Lumbar Interbody Fusion: Minimally Invasive versus Open

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