Fig. 18.1
Classification of high-grade spondylolisthesis as proposed by SDSG for spino-pelvic posture in high-grade spondylolisthesis. [Reprinted from Labelle H, Mac-Thiong JM, Roussouly P. Spino-pelvic sagittal balance of spondylolisthesis: a review and classification. Eur Spine J. 2011;20 Suppl 5:641-646. With permission from Wolters Kluwer Health]
Treatment Algorithm: High-Grade Spondylolisthesis
Patients with high-grade slips are usually symptomatic, and their deformities are well established; therefore, surgical management is generally the preferred method of treatment for high-grade slips. The primary endpoints of treatment in these patients are satisfactory reduction of the slip and fusion of the lumbosacral junction to prevent any further slippage, with the overall goals of surgery being to restore lumbosacral lordosis while minimizing neurological complications and improving neurologic function for those patients who have deficits [7]. Restoration of the ability to withstand shear forces at the lumbosacral junction is crucial to successful surgical management, and it is only accomplished with establishment of the posterior tension band (normally provided by the pars interarticularis) and the anterior column support [3]. Standing lateral radiographs of the lumbar spine and pelvis are requirements for appropriate classification, as patients with unbalanced deformities may necessitate reduction of sagittal misalignment [6, 8]. Figure 18.2 is the proposed SDSG classification algorithm, with suggestion that reduction may be indicated for some type 5 deformities, and mandatory for all type 6 deformities [6]. In addition, inclusion of full length lateral 36″ scoliosis radiographs are imperative to further classify overall sagittal balance. However, while many techniques for reduction and fusion have been described, the ideal treatment remains an area of ongoing debate [9].
Fig. 18.2
Classification algorithm of spondylolisthesis based on spino-pelvic posture. [Reprinted from Labelle H, Mac-Thiong JM, Roussouly P. Spino-pelvic sagittal balance of spondylolisthesis: a review and classification. Eur Spine J. 2011;20 Suppl 5:641-646. With permission from Wolters Kluwer Health]
Controversies
Significant controversy exists regarding the necessity of reduction of the slip, as well as the timing and most effective means of achieving reduction. Even maintaining the reduction while the fusion mass heals is an area of contention. While low-grade spondylolistheses treated with in situ fusion have shown relatively good outcomes, high-grade slips treated without reduction were thought to be prone to high rates of nonunion or slip progression [10–13]. A 6 % incidence of cauda equina syndrome has also been reported with in situ fusion without reduction [14], and pseudarthrosis, progression of the deformity and persistent symptoms have all be described without reduction [15, 16]. One study comparing in situ fusion with reduction and arthrodesis found better functional results at 15-year follow-up for the in situ group, but reductions were not anatomic, and the patient population was relatively small [17]. It has been theorized that when fusion is performed without reduction, the graft remains in tension, which is not conducive to formation of a fusion mass [18]. However, some recent studies have suggested that only patients with an unbalanced pelvis require reduction, while patients with high-grade slips but balanced deformities may benefit from in situ fusion without reduction [8]. A separate controversy exists regarding open versus minimally invasive surgical techniques for reduction and fusion, though the literature has recently shown favorable outcomes—lower estimated blood loss, shorter surgical time, and shorter hospital stay—utilizing minimally invasive techniques [19–21].
Described Surgical Techniques
The literature is replete with various techniques for the surgical management of high-grade spondylolisthesis, including open, minimally invasive, and “mini-open” procedures, as well as various techniques for reduction of the slip. These principles apply primarily to high-grade isthmic spondylolisthesis at the L5-S1 junction. As previously mentioned, the primary goal of surgical treatment is the restoration of both the posterior tension band and anterior structural support, which prevents the conversion of axial load to shear forces through the lumbosacral junction [3].
Open Procedure
Positioning and Approach
Positioning of the patient is one of the most important steps in the surgical procedure. A modified Jackson table is ideal. The patient is placed prone with the hips in maximal extension, which allows for partial reduction of pelvic retroversion in patients with a mobile L5-S1 segment, and may require elevation of the patient’s lower extremities above the table [22].
Open Reduction
Reduction of the slip, in patients with an appropriate indication, is technically demanding with a relatively high rate of neurologic injury. Various open techniques have been described, including casting [25], Harrington rod distraction [26], staged reduction and fixation using an external fixator [27], and translation through posterior instrumentation [28].
It is essential that the involved nerve roots are decompressed bilaterally, while it is often beneficial to maintain the upper section of the L5 lamina to preserve the attachment of the ligamentum flavum when performing a reduction [23]. Removing the posterior elements and far lateral exposure allow for direct visualization of the nerve roots, and it is important to completely decompress these nerve roots before reduction is attempted to minimize these risks [14, 23].
Subsequent preparation of the involved disc space and/or removal of the dome of the sacrum is advisable to facilitate reduction. Poly-axial screws (or reduction screws which are preferable) are then placed in the pedicles of the upper and lower vertebrae, though use of Schanz pins in L5 has been reported instead of pedicle screws [22]; the pedicle screw insertion points for the sacrum are superior and lateral to the superior articular process. The insertion points for L5 are often unreliable and deformed in these patients, but the screws can be placed under direct visualization after removal of the posterior elements [24].
Distraction is then performed at the involved level using any flat instrument such as a Cobb elevator as a lever to open the intervertebral space; Harrington rods have been described for use in reduction as well [24]. Many techniques have been described including using either a rod or plate, which has been contoured to appropriate lumbar lordosis, or by utilization of a reduction tool. The sacral screw is first used as an anchor; by reducing the L5 screws to the rod or plate, a posteriorly directed force is generated that pulls the vertebral body back into alignment [23, 24].
Minimally Invasive Procedure
Positioning and Approach
The minimally invasive technique has been previously described [29, 30], though is primarily reserved for surgical patients with grade III (or lower) spondylolisthesis [31]. Positioning also involves a hyperextended, prone positioning on a radiolucent table. Three-centimeter paramedian incisions are made approximately 4–5 cm from the midline over the affected level, and blunt dissection is performed to the appropriate facets with fluoroscopic confirmation [31]. MIS retractors are placed, and either loupes with fiberoptic lights or a surgical microscope may be utilized for visualization. Standard MIS facetectomies and transforaminal lumbar interbody fusion (TLIF) are performed bilaterally, with sequential distraction of the interbody space to allow passage of the implant; concomitant discectomy is performed to open the space completely [31].
Reduction
After the MIS approach has been completed and there is adequate exposure, spondylolisthesis reduction screws are placed under fluoroscopic guidance in the cephalad vertebral pedicles, and standard poly-axial pedicle screws in the caudad vertebra [31]. The paramedian approach allows improved access to the L5 pedicles with improved trajectory as compared to the open, midline approach. Reduction of the slipped vertebral element is performed with a rod clamped to the reduction screws, with the reduction blades facilitating posterior translation of the superior vertebra in relation to the fixed, inferior vertebral body [31].
Interbody Fusion
After adequate reduction has been achieved, whether open or MIS, it is mandatory to supplement the reduction with an adequate supporting implant and bone grafting. Without an interbody implant and appropriate grafting, the slip will be prone to loss of correction, nonunion, and long-term failure [32–34]. Interbody fusion may be achieved with either an anterior or posterior lumbar interbody fusion (PLIF) technique [12, 35, 36]. Structural interbody cages are placed bilaterally in the disc space. The pedicle screws are compressed to restore lordosis, and if the L5 nerve roots are noted to be in tension, an anterior lumbar interbody fusion (ALIF) may also be performed. Posterior fusion is completed with grafting of the transverse processes and sacrum [22].
Authors’ Preferred Management
Preoperative Planning
Adequate preoperative planning is essential in the management of patients with high-grade spondylolistheses. We prefer the sagittal balance classification of Labelle et al. [4, 6] in assessing overall global sagittal alignment. If the patient is a Type 5 with compensated sagittal balance, then a reduction maneuver is not necessary. The proposed operation needs to take into account the patient’s preoperative symptoms: if the patient presents with radiculopathy, a thorough nerve root decompression is warranted even if no reduction of the spondylolisthesis is to be performed.
Surgical Technique
It is the opinion of the authors that in order to best facilitate restoration of the biomechanics of the lumbosacral junction, anatomic reduction of the deformity is recommended [3, 36, 37]. Doing so reestablishes normal biomechanics and neutralizes shear forces. Restoring sagittal spino-pelvic alignment favors union and does, in theory, decrease the risk for adjacent level degeneration. Given the potential tension this maneuver will place on the L5 nerve roots, therefore, monitoring of the L5 nerve roots throughout the procedure is recommended [3].
The patient is positioned prone on a radiolucent surgical table such as a Jackson table (OSI, Union City, CA). L4 through the caudal edge of the sacrum is exposed via a low lumbar skin incision. Exposure is carried out laterally enough to expose the transverse processes of the lumbar vertebrae as well as the sacral alae. It is important to note that because there is frequent anatomic aberration in this region, care must be taken to avoid iatrogenic durotomy. For all reductions of Meyerding Grade III spondylolistheses, our preferred method is to perform a Gill laminectomy to allow access to the cauda equina and nerve roots [37]. Additionally, it allows for the use of this bone for bone graft in preparation for the fusion bed. Following Gill laminectomy, we thoroughly perform wide and extensile decompression of the L5 nerve roots. When the deformity is Grade IV or V, the nerve root often is dysmorphic in its appearance. In these settings we use free running EMGs to stimulate the nerve to ensure we are adequately identifying it.
Related posts:
Intraoperative Neuro-Monitoring During Spondylolisthesis Surgery
Management of Traumatic Spondylolisthesis: Cervical and Lumbar
Results of Surgical Treatment of Pediatric Spondylolysis and Spondylolisthesis
Clinical Evaluation of Pediatric Patient with Spondylolisthesis
Spondylolisthesis Associated with Scoliosis
Management of Spondyloptosis
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
