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Minimally invasive options for surgical management of adjacent segment disease of the lumbar spine
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.232335
Keywords: Adjacent segment disease, anterior lumbar interbody fusion, lateral lumbar interbody fusion, low back pain, minimally invasive spine surgery, transforaminal lumbar interbody fusion
As an increasing number of lumbar spine operations are being performed, the incidence of adjacent segment disease (ASD) continues to become more relevant and concerning, resulting in higher reoperation rates, longer fusion constructs, and increased morbidity with open surgery.[1] The prevalence of symptomatic ASD requiring surgery varies and ranges from 5 to 16% at 5 years and from 10 to 36% at 10 years.[2],[3],[4] Reoperation rates for laminectomy alone and laminectomy with non-instrumented fusion vary from 1.3 to 5.6%, whereas reoperation rates for ASD after instrumented posterior lumbar interbody fusion have been reported to be as high as 80% at 5 postoperative years.[5] A recent meta-analysis concluded that patients undergoing minimally invasive spine surgery (MIS) may have a lower incidence of ASD than patients undergoing open surgery.[6] The evidence supporting the efficacy of motion-sparing techniques in reducing adjacent level pathology remains inconclusive.[7],[8] The potential risk factors include age >60 years, body mass index >25 kg/m 2, preexisting disc and facet degeneration, and number of levels fused for ASD in the lumbar spine.[3],[9],[10] The treatment strategy for the management of ASD of the lumbar spine often involves open revision surgery with replacement, revision, or extension of existing hardware. These procedures are associated with a longer operative duration, an increase in blood loss, a longer hospital stay, and a higher incidence of postoperative complications.[11],[12] The operative morbidity of revision surgery and the increasing health-care costs related to their management further burden society.[13] To mitigate the complexity of open revision lumbar spine surgery for ASD, various instrumented and noninstrumented MIS techniques can be performed. We present a comprehensive literature review of MIS treatment strategies, as well as a concise description and illustrative cases of several MIS techniques used to treat ASD and its complications.
We conducted a retrospective chart review of patients who underwent a lumbar MIS for symptomatic ASD. Four representative cases were selected to illustrate potential MIS techniques for the management of ASD of the lumbar spine [Table 1] and [Table 2].
Case #1: MIS foraminotomy and laminectomy A 48-year old man presented with recurrent right lower extremity pain and posterior thigh and calf pain. He had suffered a spinal cord injury years earlier and had an extensive syringomyelia extending the entire length of his spinal cord. He had a history of an L1-S1 posterior fusion performed 6 years ago, followed by a L5/S1 ALIF for pseudoarthrosis. The neurologic examination was normal. Lumbar radiographs revealed a robust fusion from L1-S1 levels. The CT myelogram demonstrated severe lumbar stenosis at the L1/2 level and foraminal stenosis at the right L5/S1 foramina [Figure 1]. After 6 months of conservative treatment, which included an epidural steroid injection and physical therapy, he underwent a right L5/S1 MIS foraminotomy and L1/2 MIS laminectomy via a 22 × 7 mm docking tube. His pain was almost resolved on follow-up (preoperative Oswestry disability index [ODI] 62, visual analogue scale [VAS] back/leg 8/10; 3 years postoperative ODI 28, VAS back/leg 4/4).
Case #2: Stand-alone anterior lumbar interbody fusion A 74-year old female patient with a history of fibromyalgia and a prior history of L4/5 TLIF over 15 years ago, presented with lower back and right lower extremity pain. Two years after her initial surgery, she had a right L5/S1 MIS foraminotomy and removal of prior hardware. She did well for over 10 years and presented again for back and right lower extremity pain. On physical examination, she had grade 4/5 strength in her right tibialis anterior and gastrocnemius. She had an absent Achilles reflex on the right side. Her lumbar radiographs revealed successful fusion at the L4/5 level and a collapsed disc space at the L5/S1 level. MRI of the lumbar spine revealed bilateral L5/S1 foraminal stenosis [Figure 2]. She underwent a stand-alone ALIF at L5/S1. This procedure was done with the assistance of a general surgeon during the approach through a mini-laparotomy with specialized retractors. A 12 mm × 10 mm-degree cage was inserted into the disc space and provided adequate restoration of disc height. On her most recent follow-up, she had substantial resolution of her symptoms (preoperative ODI 64, VAS back/leg 10/9; 3 months followng her surgery, she showed a gradual improvement in her ODI to 48).
Case # 3: Transforaminal lumbar interbody fusion A 75-year old male patient with a prior history of L3-5 laminectomy and posterior fusion, presented with new-onset worsening low back and right lower extremity pain. His leg pain was temporarily relieved by a targeted nerve block. His X-rays revealed degenerative scoliosis with convexity to the left, centered at the L2-3 level. The MRI showed stenosis at the L2-3 level and a right-sided disc herniation at the L5-S1 level, suggestive of adjacent segment disease both above and below the previous fusion. Surgery was recommended because conservative measures were unable to manage his pain and disability. He underwent a minimally invasive left LLIF at the L2-3 level, followed by an MIS TLIF at the L5-S1level, and percutaneous screw fixation from the L1-S1 levels. The previous screws from L3-5 were replaced, and scoliosis was corrected with percutaneous passage of the rods [Figure 3]. He did very well postoperatively (preoperative ODI 34, VAS back/leg 5/5; 3 months postoperative ODI 38, VAS back/leg 1/3).
Case #4: Lateral lumbar interbody fusion A 65-year old male patient with a prior history of L3 laminectomy and L3-5 posterior fusion, who did well for 1 year, presented with worsening back pain. His neurologic examination was normal. Conservative management including physical therapy was attempted with no subsequent pain relief. Lumbar radiographs revealed an adequate fusion at the L3/4 and L4/5 levels and adjacent L2/3 level disc collapse with rotatory subluxation [Figure 4]. He underwent an L1/2 and L2/3 level left-sided LLIF, with removal of the prior instrumentation, and placement of percutaneous L1-L4 level instrumentation. His pain resolved at the most recent follow up (preoperative ODI 26, VAS back/leg 7/0; 3 months postoperative ODI 30, VAS back/leg 3/0).
In another patient with a prior L3-S1 fusion and new symptomatic L2/3 level disc degeneration, we performed an L2/3 LLIF and backed it up with facet screws instead of reconnecting to the previous construct [Figure 5] (preoperative ODI 48, VAS back/leg 9/8; 6 months postoperative ODI 28, VAS back/leg 4/0).
Pathophysiology of adjacent segment disease The pathophysiology of adjacent segment disease is multifactorial. Literature is still nebulous about whether or not this is indeed related to the previous fusion surgery rather than to the progressive natural history of the underlying degenerative disease.[14] Disc degeneration at the adjacent segment is the most common abnormal finding. Biomechanical changes consisting of increased intradiscal pressure, increased facet loading, and increased mobility, occur after fusion and have additionally been implicated.[15] Several risk factors contribute to ASD following the application of instrumentation; fusion length (especially three or more levels), preoperative sagittal misalignment, facet breach, advanced age, increased body mass index (BMI), and preoperative documentation of cephalad degenerative disease (e.g., disc disease, stenosis).[7] Hence, potentially modifiable risk factors for the development of adjacent segment disease include fusion without instrumentation, protecting the facet joint of the adjacent segment during the placement of pedicle screws, the fusion length, and the sagittal balance. The rate of symptomatic ASD in the lumbar spine after decompression and stabilization is approximately 2–3% per year. This can be addressed by utilizing a number of different surgical techniques while providing long-term improvement in low-back pain, disability, and quality of life.[16],[17] It is important to subdivide ASD into adjacent segment stenosis and adjacent level instability to determine if decompression alone versus an extension of fusion is necessary.[18] The minimally invasive surgical techniques for decompression, stabilization, and fusion of the spinal column have become increasingly popular over the past decade.[19] MIS techniques limit the disruption of the paraspinal muscles and ligamentous structures; this disruption may potentially compromise lumbar stability and lead to further ASD.[20] Other advantages include diminished blood loss, shorter hospital stays, and decreased postoperative pain.[21] The utility of MIS techniques continues to expand, and surgical indications now include a wider spectrum of pathologies. With increasing familiarity and experience, these techniques can be used for the management of ASD. Noninstrumented minimally invasive surgery techniques Although the standard surgical paradigm involves extending a prior fusion, in patients who are symptomatic from unilateral foraminal disease or stenosis secondary to foraminal narrowing or disc encroachment, an MIS discectomy or foraminotomy may suffice even in the presence of a prior fusion [Table 3].[22] This should be done in select patients in whom decompression can be achieved without significant violation of the facet joint, which may eventually result in instability.[23] Phillips et al.,[24] reported a 57.7% improvement in back and leg pain after MIS tubular decompression alone, while Schlegel et al.,[25] showed a 64.2% improvement in a similar cohort.
Percutaneous microendoscopic discectomy (PED) or foraminotomy offers an advantage by providing direct visualization of the compression and adequate decompression at the desired level.[26] Indistinct anatomic alterations and perineural scarring make revision spine surgery more challenging than the primary one, not only at the initial level but also at adjacent levels. However, the endoscope provides an excellent visualization in delineating these structures to accomplish the goals of surgery. This procedure can also be performed under local anesthesia with sedation. The incidence of an intraoperative dural tear was reported to be lower in endoscopic discectomy alone when compared to the fusion procedures.[27] Telfian et al.,[28] reported their experience in performing a PED adjacent to the level of fusion and found that while all patients had significant improvement in back and leg pain scores postoperatively, 3 of their 9 patients (33%) eventually required a fusion by their 2 year follow-up. This technique may be a useful procedure in elderly patients who do not wish to undergo an instrumented fusion. Anterior lumbar interbody fusion The ALIF procedure, either with a stand-alone cage or with an integrated screw and/or plate system, serves as an excellent MIS option in patients with lumbosacral ASD.[29],[30] This clearly avoids all the complications of a posterior approach such as a durotomy, nerve root injury, and secondary damage to posterior muscular and ligamentous structures. ALIF offers direct anterior column support, restores lordosis, increases fusion rates (because of a large surface area for grafting and placement of a graft under direct compression), shortens operative time, and expedites patient recovery. It can be performed on up to 3 levels with the same incision, with a short operative time and minimal blood loss. The addition of percutaneous posterior fixation, either with or without facet fusions, can be done if there is instability or significant deformity. Rao et al.,[31] performed this procedure in five patients with ASD with a fusion rate of 80%. Mamuti et al.,[32] successfully used this approach in 35 patients with recurrent disc herniation who had undergone prior discectomy and posterior instrumentation. All patients showed clinical improvement; postoperative CT scans at 1 and 2 years demonstrated bony fusion, with a normal position and morphology of the fusion cage in all the included patients. In cases of disc herniation, resection of the extruded disc fragments can be accomplished by opening the posterior longitudinal ligament by performing a direct decompression rather than an indirect decompression, as is often the case with an ALIF.[33] The most commonly reported complications are retrograde ejaculation, vascular injury, superficial infection, urological injury, and abdominal muscle damage.[29] Transforaminal lumbar interbody fusion TLIF is a very versatile operation and is the workhorse of posterior lumbar fusion.[34],[35],[36] Using MIS techniques, it is easy to perform at a level adjacent to a previous fusion. Rods can be removed, connected, or extended. In patients with a prior TLIF, Lee et al.,[37] reported that the cost effective procedure of revision extension surgery for ASD, reusing the pedicle screws extracted from the fused segments, resulted in excellent clinical and radiological outcomes. The fusion rates, too, were comparable to those patients in whom new screws were used. The perioperative complication rate is approximately 15%, with the most common complication being a durotomy.[38] TLIF can be considered an effective, reliable, and safe alternative procedure for the treatment of recurrent lumbar disc herniation, either at the same or adjacent level.[39] The posterior instrumentation can be done either using unilateral or bilateral pedicle screws, translaminar facet screws, or a combination of these.[40] Whether an interbody fusion is required or just a posterolateral extension of fusion would suffice to treat the adjacent segment continues to be a matter of debate. One has to be extremely vigilant while placing percutaneous screws adjacent to a previous fusion. Park et al.,[41] retrospectively reviewed their series of 184 pedicle screws placed using a MIS fluoroscopic technique in 92 patients with ASD and found a surprisingly high and unexpected incidence of cranial facet joint violation (in 50% of all patients and in 32% of all screws inserted). The clinical implication of this has yet to be determined. Some authors have described the use of navigation-guided, mini-open cortical bone trajectory screws in cases with ASD, which allows for the placement of pedicle screws in a previously instrumented pedicle.[42] As the entry point is at the lateral aspect of the pars interarticularis, this procedure avoids an extensive tissue dissection by limiting the surgical corridor to the levels adjacent to the existing hardware, thus eliminating the need to expose, remove, or extend the hardware with the anticipated benefits of reduced operative time, blood loss, and dissection. In certain cases of multilevel ASD, a TLIF can be combined with an interspinous or hybrid stabilization device at the cranial segment (topping off technique) to further reduce the incidence of future ASD.[43],[44] Other dynamic stabilization devices have also been used in isolation to connect to a previous fusion.[45] Posterior dynamic stabilization, in which pedicle screw fixation is coupled with a flexible longitudinal connecting system, presumably allows for the normalization of intersegmental motion. This stands in contrast to the traditional fusion surgery, in which the goal is the complete and immediate elimination of motion and, ultimately, arthrodesis. These devices theoretically avoid an abrupt transfer of stress from a rigid construct to the neighboring segments, thereby potentially diminishing ASD.[46] Lateral lumbar interbody fusion LLIF is also an effective surgical treatment option for ASD with good clinical and radiographic outcomes.[19],[47],[48] Given the widespread use of electrophysiology and the tubular retractor technology, the lateral approach has gained further popularity. Although a stand-alone LLIF is associated with a narrower spectrum of adverse effects compared to circumferential fusion, posterior instrumentation, either in the form of pedicle screws and rods (unilateral or bilateral) or facet screws alone, may be necessary to increase segmental stability in certain cases.[47] Biomechanical studies have shown that the addition of a lateral interbody device super-adjacent to a 2-level fusion significantly reduces motion in flexion, extension, and lateral bending. Supplementing with a lateral plate further reduces the motion during lateral bending and torsion. The addition of posterior cortical screws provided the most stable LLIF construct, demonstrating the range of motion comparable to a traditional 3-level TLIF.[49] LLIF has the advantage of providing an indirect decompression while using a large footprint interbody device. It provides an alternate route for decompression and may be helpful by avoiding a dissection through a prior laminectomy defect or scar tissue. It also provides the added benefit of avoiding ligamentous disruption, which has been hypothesized to exacerbate ASD.[50] In patients with ASD, LLIF results in an improvement in back and leg pain because of an increase in disc height, increase in segmental lordosis, and decrease in coronal segmental angulation.[47] However, Aichmair et al.,[47] showed that the reoperation rate after LLIF for ASD was 21.2%, with a trend toward a higher fusion rate in patients who underwent circumferential fusion compared to the stand-alone subgroup (87.5% vs. 53.8%; P= 0.173). On the other hand, in their series of 21 patients, Wang et al.,[19] described only 1 patient who developed further ASD, requiring posterior revision surgery. Cage subsidence rates were also lower when LLIF was used in patients with ASD, probably because of the presence of pedicle screws in the caudal vertebral body.[19] In addition, if one desires not to handle the previous fusion caudally, posterior fixation can be achieved with facet screws alone that achieve comparable results to pedicle screw fixation [51] [Figure 5]. The frequent development of transient thigh pain, weakness, numbness, or dysesthesias is a limiting factor of this method but can be minimized with the increased familiarity with this approach. These complications seem to be lower when an oblique trajectory is used as opposed to a direct lateral one.
MIS techniques to address ASD after a prior lumbar fusion provide decompression of the neural elements, as well as spinal stabilization, and fusion. As familiarity and comfort with MIS increases, this surgical technique can treat ASD, while limiting posterior soft tissue disruption and surgical morbidity from open surgery, with excellent clinical and radiological outcomes. Disclosures Dr. Fessler received royalties from DePuy, Stryker, and Medtronic. He has an ownership interest in In Queue Innovations. Other authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.[56] Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
[Table 1], [Table 2], [Table 3]
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