Surgical Approach and Complications of Stand-alone Lateral Trans-Psoas Interbody Fusion

Podsumowanie

Interbody fusion of the lumbar spine can be achieved surgically using different techniques. Minimally invasive techniques, including lateral interbody fusion, have been developed within recent decades to reduce rates of complications and allow for quicker patient recovery. We provide insight into stand-alone lateral trans-psoas interbody fusion, highlighting potential complications and pitfalls.

Streszczenie

Interbody fusion of the lumbar spine is a standard procedure for symptomatic degenerative lumbar spine disease if conservative treatment fails. Surgical decompression and fusion of the segment can be achieved using several different techniques. Over the last decades, minimally invasive techniques, such as lateral interbody fusion (LLIF), have been developed to reduce tissue damage and complications and allow quicker patient recovery. With growing popularity, indications for LLIF have expanded to treat spinal deformities and foraminal/central stenosis. Mechanically, it allows for an unsurpassed fixation through the left-to-right apophyseal ring placement of the cage. LLIF utilizes a minimally disruptive retroperitoneal corridor and includes both trans-psoas and pre-psoas approaches. For the pre-psoas approach, the risk of damage from manipulation of the intramuscular lumbar plexus is reduced compared to a trans-psoas approach. However, increased risks of major vascular, ureteral, bowel injury and sympathetic plexus damage are reported.

This article aims to provide a detailed and comprehensive guide on stand-alone lateral trans-psoas interbody fusion, including its indications, surgical procedure, potential complications, and outcomes based on a decade of experience from a single center.

Wprowadzenie

Lower back pain, an important symptom of degenerative lumbar disease (DLD), is common in patients over 65 years¹. Other symptoms of DLD include radiculopathy and claudication. When non-surgical treatment fails, surgical decompression or, if indicated, interbody fusion of the spine may be a viable treatment option². Several techniques and approaches have been developed to achieve interbody fusion or decompression of the segment. Traditional approaches include posterior lumbar interbody fusion (PLIF), transforaminal lumbar interbody fusion (TLIF), and anterior lumbar interbody fusion (ALIF). Approaches to the lumbar spine are illustrated in Figure 1.

Figure 1: Different approaches to the lumbar spine for interbody fusion¹². Overview of the different approaches used for lumbar interbody fusion. LLIF is a trans-psoas approach, and OLIF is a pre-psoas approach. Please click here to view a larger version of this figure.

Over the last decades, minimally invasive techniques for interbody fusion of the lumbar spine have been developed to reduce tissue damage and complications, allowing for quicker patient recovery, reducing complications, and surpassing the technical limitations of traditional approaches to the spine. In 2001, Pimenta et al. introduced a minimally invasive retroperitoneal approach to the lumbar spine by splitting the psoas, providing direct disc exposure by expanding the retroperitoneal space. This has been introduced as the lateral trans-psoas approach^3,4. This technique was modified with the use of special retractors and popularized by Ozgur et al.⁵. In recent years, extreme lateral interbody fusion in a prone patient position has been developed. This technique offers efficiency with combined posterior procedures and improved lumbar lordosis^6,7.

Lateral interbody fusion (LLIF) can be achieved utilizing various approaches. These include trans-psoas approaches (extreme lateral interbody fusion (XLIF⁸), direct lateral interbody fusion (DLIF⁹) using different instruments), and a pre-psoas approach (oblique lateral interbody fusion (OLIF¹⁰). The approach used for the procedure depends on the patient and the surgeon's training, among others. Anatomical studies showed notable benefits for trans-psoas approaches (minimal blood loss, preservation of the posterior musculature and ligamentous chain, the ability to perform an extensive discectomy, and placement of a large intervertebral graft) but also disadvantages (post-operative nerve palsies, visceral abdominal injuries)¹¹. Reported major but rare complications include intestinal perforation, common iliac vein injury, cage subsidence, vertebral body fractures around the interbody device, retroperitoneal hematoma, and pneumoretroperitoneum with an associated pneumoscrotum¹². Overall, pre-psoas approaches are associated with a slightly lower complication rate and fewer postoperative neurological deficits¹³. To allow optimal outcome, the indication for a lateral interbody fusion needs to be done carefully. We advise obtaining a computed tomography (CT) and magnetic resonance (MR)-scan of the lumbar spine. To assess the segment hypermobility or instability, obtain flexion-extension X-ray images besides regular anteroposterior (AP) and lateral. Common indications are patients with segmental instability and concurrent radiculopathy who have failed non-surgical treatment. In the case of segmental instability or deformity surgery, additional internal fixation may be necessary. LLIF may be limited in the lower lumbar spine, depending on the height of the iliac crest. Supplemental posterior fixation may add valuable construct stiffness and deformity reduction for patients with high-grade instability, deformity, or questionable bone stability. Contraindications for this procedure are typically malignancy, high-grade deformities, or bifurcation abnormalities. A history of retroperitoneal infection or disease and previous retroperitoneal surgery or injury are important considerations. Risk factors for poor outcomes include osteoporosis, smoking, long-term steroid use, severe deformities, and segment hypermobility due to facet effusion or previous laminectomy^14,15,16. Also, patients with very low body mass index and anterior psoas location are potentially adverse patients for increased complexity of access. In revision surgery, a pre-psoas approach may be favorable to avoid scar tissue.

The aim of this article is to provide step-by-step guidance to surgeons on a stand-alone lateral trans-psoas interbody fusion, including pitfalls and complication rates after 10 years of single-center experience.

Protokół

The retrospective study was approved by our institutional review board (STUDY2021000113), and an informed consent waiver was granted because of the nature of the study. The procedure demonstrated in the video was performed on a human specimen that was obtained and utilized following the ethical guidelines and protocols established by our institution. The specimen was handled respectfully and in compliance with all relevant ethical standards.

1. Patient selection

1. Select patients with degenerative lumbar disease and failed non-surgical treatment.
2. Assess segment hypermobility or instability with flexion-extension X-ray images in addition to regular anteroposterior (AP) and lateral views (Figure 2). In cases of segment instability, perform an additional posterior fixation.
3. Obtain a computed tomography (CT) and magnetic resonance (MR)-scan of the lumbar spine.

Figure 2: Pre-operative and follow-up X-ray images in A.P and lateral view. (A-B) Multilevel degenerative lumbar spine disease with collapsed disc space L3/4 as well as L4/5 and neuroforaminal stenosis. No signs of instability or hyperflexible were observed. (C-D) One-year post-operative follow up. Correct position of PEEK cages in L3/4 and L4/5 disc space without subsidence. Both disc and neuroforaminal height are restored. Please click here to view a larger version of this figure.

2. Positioning

1. Position the patient, under general anesthesia, in a right-sided decubitus position with partially flexed hips and knees on a radiolucent operating table. Pad bony prominences to avoid soft tissue damage due to pressure.
2. Secure the patient with surgical tape and belts/pads to prevent movement and ensure safety.
3. Flex the operating table to generate more space if needed.

3. Preoperative phase

1. Confirm the desired surgical level with AP/lateral fluoroscopy images.
2. Use skin markers to visualize the disc space and vertebral bodies of the desired level on the skin surface (Figure 3).
3. Place electrodes for electromyography (EMG) on reference muscles for nerves that could be at risk during surgery¹⁷.

4. Approach

1. After disinfecting the skin and covering the area with the surgical drape, according to institutional standards, make a 3-5 cm long skin incision using a sterile scalpel over the disc space in a single-level surgery.
2. Use electrocautery to dissect the fascia abdominalis.
3. Open the fascia and use clamps/retractors to bluntly split the three layers of the obliques until the retroperitoneal space is reached.
4. Identify the psoas and split it in the longitudinal direction (for example, using retractors).

5. Neuromonitoring

1. Look out for any changes in somatosensory evoked potentials (SSEP), motor evoked potentials (MEP), and spontaneous electromyography (EMG) during approach and when dissecting the psoas¹⁷.
2. Using a handheld EMG probe, identify the exiting nerve root at the desired level.

6. Retractors

1. After fluoroscopically confirming the desired level, place a self-retaining retractor system (Figure 4).

7. Preparation of intradiscal space

1. Use a scalpel to perform an annulotomy and resect all discal material using a rongeur.
   NOTE: In severe degeneration, the disc space may be obscured by osteophytes. These may need resection before evacuation of the discal space.
2. Place a spreader to open the collapsed intervertebral space.
   NOTE: In cases of severe degeneration, only partial restoration of the intervertebral space may be possible.
3. Carefully remove disc material and cartilage from both endplates using Curettes or Cobb elevators (Figure 4).

8. Placement of trail cage

1. Use different trial components to restore normal disc height and to relieve any pressure on nerve roots.
   NOTE: The trial position is verified using fluoroscopy from both the AP and lateral views. The endplates should be symmetrically elevated (Figure 4).

9. Cage implantation

1. After identifying the correct size, implant the cage under fluoroscopic guidance (Figure 5).
2. Obtain final fluoroscopic images in A.P. and lateral view.

10. Closure

1. Use irrigation and perform a final hemostasis check.
2. Carefully remove all retractors and spreaders.
3. Close the wound in a multilayered fashion.

Figure 3: Identification of disc level. (A-B): Marking the desired level in anteroposterior (AP) and lateral view. (C) Identification of the desired level in the lateral view fluoroscopy. Please click here to view a larger version of this figure.

Figure 4: Interoperative view during LLIF. (A) Position of Retractors on AP view. (B) Intraoperative verification of the correct level using fluoroscopy lateral view with retractors in place. (C) View on disc-level through Retractors. The disc was removed, with some cartilage left. (D) Intraoperative fluoroscopy AP view, with a trial cage in place. Please click here to view a larger version of this figure.

Figure 5: Intraoperative view with implanted cage. (A) Intraoperative view through retractors. Visualization of the implanted cage. (B-C) Fluoroscopy with the cage in place. Correct positioning of the cage with restoration of disc height. Please click here to view a larger version of this figure.

11. In-hospital postoperative phase

1. Encourage patients to mobilize without a brace within hours by providing adequate pain medication or other pain management techniques.
2. Provide the patient with a clear diet until the patient has passed flatus, then advance to a regular diet.
3. Perform a recommended inspection and manual palpation of the flanks and a formal dressing check before discharge.

12. Outpatient postoperative phase

1. After two weeks, perform a formal wound check.
2. Advise the patients not to perform bending/lifting/twisting movements greater than 15 lbs.

13. Follow up

1. At six weeks obtain postoperative X-rays and initiate 6 weeks of formalized physical therapy and education in trunk mechanics (Figure 2).
2. At 3 months perform a formal evaluation. If concern for pseudoarthrosis arise obtain a CT with MPR (multiplanar reformatting) or MIP (maximum intensity projection) post-processing tools to assess for continuity of the fusion.
3. At six months, perform a neurological evaluation and obtain standard radiographs.
4. Release patient from care after a last clinical and radiological follow-up one-year post-surgery.

Wyniki

In our recent study, we investigated the complication rates following a stand-alone lateral interbody fusion¹². We retrospectively investigated 158 patients (145 trans-psoas, 13 pre-psoas) who received an LLIF between 2016 and 2020, with a mean follow-up of 14 months (Table 1).

Patient characteristics

All (n=158)

Trans-psoas (n=145)

Dyskusje

Lateral Lumbar Interbody Fusion (LLIF) has become a popular minimally invasive technique for achieving arthrodesis. Since its introduction, indications have expanded for the treatment of various lumbar conditions such as degenerative diseases, deformity, and lumbar spinal pathologies. It allows implantation of larger interbody cages than TLIF or PLIF across the apophysis leading to effective correction of coronal deformities and indirect decompression of the neuroforamina by restoring disc height¹⁸

Materiały

Name	Company	Catalog Number	Comments
100mm Aluminum Center Blade	Nuvasive	3244100
100mm Electrode Center Blade	Nuvasive	3243100
100mm Left Blade	Nuvasive	3241100
100mm Right Blade	Nuvasive	3242100
110mm Aluminum Center Blade	Nuvasive	3244110
110mm Electrode Center Blade	Nuvasive	3243110
110mm Left Blade	Nuvasive	3241110
110mm Right Blade	Nuvasive	3242110
120mm Aluminum Center Blade	Nuvasive	3244120
120mm Electrode Center Blade	Nuvasive	3243120
120mm Left Blade	Nuvasive	3241120
120mm Right Blade	Nuvasive	3242120
130mm Aluminum Center Blade	Nuvasive	3244130
130mm Electrode Center Blade	Nuvasive	3243130
130mm Left Blade	Nuvasive	3241130
130mm Right Blade	Nuvasive	3242130
140mm Aluminum Center Blade	Nuvasive	3244140
140mm Electrode Center Blade	Nuvasive	3243140
140mm Left Blade	Nuvasive	3241140
140mm Right Blade	Nuvasive	3242140
150mm Aluminum Center Blade	Nuvasive	3244150
150mm Electrode Center Blade	Nuvasive	3243150
150mm Left Blade	Nuvasive	3241150
150mm Right Blade	Nuvasive	3242150
160mm Aluminum Center Blade	Nuvasive	3244160
160mm Electrode Center Blade	Nuvasive	3243160
160mm Left Blade	Nuvasive	3241160
160mm Right Blade	Nuvasive	3242160
50mm Aluminum Center Blade	Nuvasive	3244050
50mm Left Blade	Nuvasive	3241050
50mm Right Blade	Nuvasive	3242050
60mm Aluminum Center Blade	Nuvasive	3244060
60mm Left Blade	Nuvasive	3241060
60mm Right Blade	Nuvasive	3242060
70mm Aluminum Center Blade	Nuvasive	3244070
70mm Left Blade	Nuvasive	3241070
70mm Right Blade	Nuvasive	3242070
80mm Aluminum Center Blade	Nuvasive	3244080
80mm Left Blade	Nuvasive	3241080
80mm Right Blade	Nuvasive	3242080
90mm Aluminum Center Blade	Nuvasive	3244090
90mm Electrode Center Blade	Nuvasive	3243090
90mm Left Blade	Nuvasive	3241090
90mm Right Blade	Nuvasive	3242090
ALGI Penfield, Long Push	Nuvasive	3300118
Anterior Crossbar	Nuvasive	3240003
Bayonetted Shim Inserter	Nuvasive	3200215
Blade Rotation Driver	Nuvasive	3240005
Dilator - 12mm	Nuvasive	1010968
Dilator - 6mm	Nuvasive	1010966
Dilator - 9mm	Nuvasive	1010967
Fixation Shim Screw Driver	Nuvasive	3200052
Fluoro Modulator	Nuvasive	3220131
Hex Driver (3/32”)	Nuvasive	1011691
Hex Key (3/32”)	Nuvasive	1011748
Initial Dilator Holder	Nuvasive	3230140
K-wire (13.5”)	Nuvasive	3230101
Light Cable Adapter, Storz	Nuvasive	1011811
Lock Shim Inserter/Repositioning Tool	Nuvasive	3240001
Lock Shim Inserter/Repositioning Tool,	Nuvasive
Low-Profile Shim	Nuvasive	3240002
MaXcess 4 4th Blade Attachment	Nuvasive	3240004
Maxcess 4 Access System	Nuvasive		Tray with XLIF Dilator and Retractors in different seizes
MaXcess 4 Articulating Arm	Nuvasive	3240121
MaXcess 4 Blade, 180mm Electrode Ctr	Nuvasive	3243180
Needle Electrodes	Nuvasive	8050029	NVM5 System
Surface Electrodes	Nuvasive	8020029	NVM5 System
Targeting Instrument	Nuvasive	3240000
XL (18mm wide)	Nuvasive	1000-00-0716	Implant
XL-F (18mm wide)	Nuvasive	1000-00-0719	Implant
XL-F Wide (22mm wide)	Nuvasive	1000-00-0720	Implant
XLIF Annulus Cutter, 4x14mm	Nuvasive	6942414
XLIF Annulus Cutter, 4x16mm	Nuvasive	6942416
XLIF Cobb, 12mm Straight	Nuvasive	6940012
XLIF Cobb, 18mm Down	Nuvasive	6940118
XLIF Cobb, 18mm Straight	Nuvasive	6940018
XLIF Cobb, 22mm Straight	Nuvasive	6940022
XLIF Cobb, Serrated	Nuvasive	6940001
XLIF Cutter, 8mm Disc	Nuvasive	6940151
XLIF Forceps, Bipolar Str Extra Long	Nuvasive	3200322
XLIF Handle, Slide	Nuvasive	6940004
XLIF Inserter, Angled XL	Nuvasive	D6904485
XLIF Kerrison, 2mm	Nuvasive	6940132
XLIF Kerrison, 5mm	Nuvasive	6940135
XLIF Nerve Retractor, Extra Long	Nuvasive	3300319
XLIF Paddle Sizer, 4x16mm	Nuvasive	6940416
XLIF Paddle Sizer, 6x18mm	Nuvasive	6940618
XLIF Paddle Sizer, 6x22mm	Nuvasive	6940622
XLIF Penfield, Pull Extra Long	Nuvasive	3300318
XLIF Pituitary, Large	Nuvasive	6940431
XLIF Pituitary, Medium	Nuvasive	6940430
XLIF Pituitary, Small	Nuvasive	6940429
XLIF Rasp	Nuvasive	6940340
XLIF Scraper, Endplate	Nuvasive	6940020
XLIF Slide, Bayonetted	Nuvasive	6940063
XLIF Slide, XW Bayonetted	Nuvasive	6940064
XLIF Suction, 12FR Extra Long	Nuvasive	3300320
XLIF Suction, 15FR Extra Long	Nuvasive	3300321
XL-W (22mm wide)	Nuvasive	1000-00-0717	Implant
XL-XW (26mm wide)	Nuvasive	1000-00-0718	Implant