eXtreme Lateral Interbody Fusion

40 eXtreme Lateral Interbody Fusion


Luiz Pimenta, Rodrigo Amaral, Luis Marchi, and Leonardo Oliveira


Abstract


eXtreme lateral interbody fusion (XLIF) is a less invasive alternative for the treatment of different pathologies of the spine above L5. Minimally invasive surgery provides the opportunity to reduce surgical duration and patient length of stay, minimize damage to adjacent tissue, and improve patient satisfaction and quality of life. This is particularly relevant to spinal conditions like low back pain, sciatica, and other intervertebral disc degenerations, as they are currently associated with severe morbidity and elevated costs to the society. The lateral approach allows the access of the intervertebral disc laterally through the psoas muscle. Proper patient positioning and concomitant lumbar plexus monitoring are mandatory for the success of the procedure. The technique preserves primary segmental stabilizing structures of the spine while also permitting a wide discectomy with bilateral annular release. Thus, the approach allows the placement of a large implant that reaches the ring apophysis bilaterally, promoting a more rigid construction without the need of posterior supplementation in some cases. Disc height restoration and ligamentotaxis also generate an indirect decompression of the neural elements, which help recover coronal and sagittal balance. Spinal fusion and improvement in self-assessment questionnaires have been described in the literature. Intraoperative bleeding and damage of adjacent structures are minimal and patients are encouraged to walk on the same day, being discharged after an overnight hospital stay, on average. Transient plexopathies and hip flexor weakness are the most commonly reported complication associated with lateral access surgery, but the majority are resolved within 6 months. Lateral transpsoas approach has been shown to be a safe and effective surgical option in the treatment of spinal pathologies.


Keywords: low back pain, sciatica, intervertebral disc degenerations, spinal fusion, minimally invasive surgery


40.1 Definition of Problem


Chronic low back pain has been described as a complex disorder that is also associated with high morbidity rates.1,2 However, patients who suffer from a painful lumbar motion segment that is not resolved with conservative management can benefit from lumbar fusion.3 Minimally invasive surgical techniques have been demonstrated to provide a range of benefits including less tissue trauma, preservation of anatomical structures, and faster recovery.4,5 As a less invasive alternative, lateral access surgery strongly avoids the vascular, visceral, and sympathetic risks associated with traditional direct anterior approaches, and the morbidity associated with bone removal, muscle damage, and ligamentous dissection of traditional posterior approaches. This technique has been utilized in a variable number of indications, varying from single-level degenerative conditions to multilevel complex deformity corrections, also including the treatment of traumatic fractures, infections, tumor removal, revisions of prior surgeries, and total disc replacement.


40.2 Evolution of Technique


The first description of the technique was presented in Brazil in 2001 on what was then called the LETRA (Lateral Endoscopic Transpsoas Retroperitoneal Approach).6 The procedure involved the use of blunt finger dissection of the retroperitoneal space using tubular portals with endoscopic visualization, but without electromyographic (EMG) monitoring. The first report presented the results of 85 patients and showed a 14% incidence of postoperative psoas weakness and 3.5% incidence of slight thigh atrophy.7


Thereafter, the MaXcess Retractor System (Nuvasive, Inc. San Diego, CA. USA) was developed to overcome the disadvantages of working through tubular portals, generating a direct visualization of the anatomical structures. Also, the EMG nerve monitoring prevented inadvertent pressure on nerves to protect their integrity. Presently, the lateral access surgery is defined as a 90-degree true lateral, retroperitoneal approach to access the anterior column with minimal muscular disruption or trauma to adjacent structures. By using a blunt finger for dissection of the retroperitoneal space and tactile guidance of an initial dilator to the psoas muscle, with subsequent EMG-guidance of the coming dilators through the psoas, it is possible to insert an expandable split-blade retractor system that provides a customizable working channel that provides direct visualization of disc space and placement of a large interbody implant that spans the ring apophysis for maximized correction and greatest biomechanical construction.


40.3 Advantages and Disadvantages


Minimally invasive lateral surgery offers an adequate access to the disc space, with the added benefit of reduced iatrogenic injury to abdominal vascular structures (aorta and vena cava), sympathetic plexus (reducing the incidence of retrograde ejaculation), and neural structures (such as the spinal nerves that cross the posterior aspect of the psoas muscle). The technique utilizes tissue dilation through the divulsion of the psoas muscle fibers in an area of approximately 3 cm in diameter. Thus, the procedure realigns the end plates to a horizontal position through bilateral annular release, placement of a large implant across the disc space spanning the ring apophysis, and by ligamentotaxis. The cage insertion also restores disc and foraminal heights, indirectly decompressing the neural elements, and promotes stabilization through an anterior intervertebral fusion.8 In contrast, approaching the L5–S1 level is disadvantageous due to the elevated risk of iliac vessels damage as well as the position of iliac crest in the access pathway that prevents direct approach to this specific disc level.


40.4 Indications and Contraindications


The lateral approach was first indicated for the treatment of low back pain associated with degenerative changes above the L5 level.9 Recently, new indications have emerged, demonstrating that indirect decompression of the neural structures can be achieved by disc height restoration,8 while derotation of the vertebral body and coronal alignment are obtained by ligamentotaxis.10


40.4.1 Patient Selection


The lateral approach, with or without posterior supplementation, can be applied to patients who have failed prior decompressive surgery (as in discectomy and/or laminectomy) and require interbody fusion, or in cases of adjacent-level disease after prior fusion surgery, as the scar tissue must limit the ability to safely perform a traditional fusion surgery by the same approach. Other applications of the technique are adjacent-level disease, pseudoarthrosis, trauma, infection, sagittal alignment, and spondylolisthesis.11,12,13,14,15 Revisions of failed interbody fusions or failed lumbar total disc replacements have also been treated using the eXtreme lateral interbody fusion (XLIF) approach for retrieval and revision surgeries.16,17


40.5 Patient Profiles


This approach has been used successfully for levels spanning T4–T5 through L4–L5. Approaching the L5–S1 level by means of this technique is not recommended because of the risk of damage to the iliac blood vessels as well as the difficulty of accessing the disc space due to the iliac crest. For the L5–S1 level, patients may benefit from a posterior lumbar interbody fusion (PLIF) or a transforaminal lumbar interbody fusion (TLIF) combined with subsequent posterior decompression and pedicle screw supplementation.18,19


40.6 Preoperative Planning


40.6.1 Physical Examination


Physical examination is not different from that performed for all patients with spinal disorders. Spine assessment must include a three-dimensional evaluation of the coronal, sagittal, and spinopelvic parameters, as well as the neurological status.


40.6.2 Radiographic Workup and Preoperative Imaging


The initial X-ray workup begins with long-standing posteroanterior and lateral views. A focused lumbar or thoracic view might be helpful to evaluate disc height, disc asymmetry, and lateral listhesis, which are very common in degenerative scoliosis, for example. Also, lateral bending radiographs are used to evaluate the flexibility of the curve. Flexion and extension films can be used, if necessary, to determine the amount of sagittal instability or kyphosis flexibility. A CT myelogram is utilized to evaluate central and foraminal stenosis, while MRI is useful to evaluate disc degeneration and foraminal stenosis, as well as soft tissues. Other ancillary tests such as discography and facet blocks are done to elucidate the pain source.


40.6.3 Instrumentation Notes


The instruments necessary for performing the XLIF procedure are as follows:


MaXcess System of dilators and split-blade retractors (NuVasive, Inc.), which include a bifurcated light cable, articulating arm, retractor system with blades of various lengths, and blade-extension shims.


NeuroVision System for MaXcess-compatible stimulated and continuous EMG monitoring of nearby nerves (NuVasive, Inc.).


Set of interbody instruments such as curettes, rongeurs, and dissectors of different sizes (NuVasive, Inc.)


Xenon light source for attachment to MaXcess bifurcated light cable.


Radiolucent surgical table with a flexible middle section and rail for articulating arm attachment.


C-arm fluoroscope and image intensifier.


40.7 Surgical Approach


Lateral spine approaches lead to maintenance of the anterior and posterior longitudinal ligaments, which can help correct vertebral rotation and coronal and sagittal deformities, without the risks, comorbidities, and complications related to standard open surgeries.13 For example, in spondylolisthesis, the in-depth discectomy itself partially reduces vertebral slippage. The maintenance of the anterior and posterior portions of the disc, keeping intact the longitudinal ligaments, allows ligamentotaxis, which is partly responsible for slippage reduction.20 Disc height restoration has been proven to indirectly decompress the neural structures, without the need of posterior laminectomy or pedicle screw supplementation, minimizing muscle splitting, blood loss, hospital stay, and operative time, and improving patient’s recovery and satisfaction with the procedure.8,21 Moreover, several clinical reports have emerged demonstrating the safety and effectiveness of the technique in comparison to other conventional surgical approaches, with the same or better clinical and radiological results.14,22,23,24,25,26,27,28,29,30


40.7.1 Surgical Technique


Patient Preparation

In the preoperative room, the patient is linked to the EMG monitoring, which is mandatory in safely traversing the psoas muscle, avoiding the lumbar plexus that passes within it. Four muscle groups per side are monitored using the EMG system. These four muscles are easily palpated and represent spinal nerve distributions from L2 to S2: the vastus medialis, the anterior tibialis, the biceps femoris, and the medial gastrocnemius (image Fig. 40.1). A reference electrode is also placed on the upper lateral thigh, and an anode return electrode is placed superior to the operative site, for example, on the latissimus dorsi muscle. Proper skin preparation must be performed to ensure good electrical conductivity. This entails cleaning the electrode site and applying a light abrasive to remove dead skin cells. Electrodes are placed in pairs by simply removing the adhesive backing and applying to the skin. Electrical conductivity can be measured with a handheld impedance meter. These surface electrodes are connected to the system by snap-on cables that can be threaded under or through small holes in compression stockings.


Oct 17, 2019 | Posted by in NEUROSURGERY | Comments Off on eXtreme Lateral Interbody Fusion
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