Thoracolumbar Conditions
Srikanth N. Divi, MD
Kamil T. Okroj, MD
Alpesh A. Patel, MD, MBA, FAAOS
Dr. Patel or an immediate family member has received royalties from Alphatec Spine, Amedica, and NuVasive; serves as a paid consultant to or is an employee of Alphatec Spine, Amedica, DePuy, a Johnson & Johnson Company, Kuros Biosciences, NuVasive, and Zimmer; has stock or stock options held in Amedica, Cytonics, EndoLuxe, NociMed, nView Medical Inc., Spine BioPharma, and Tissue Differentiation Intelligence; and serves as a board member, owner, officer, or committee member of American Orthopaedic Association, Cervical Spine Research Society, and North American Spine Society. Neither of the following authors nor any immediate family member has received anything of value from or has stock or stock options held in a commercial company or institution related directly or indirectly to the subject of this chapter: Dr. Divi and Dr. Okroj.
ABSTRACT
Degenerative thoracolumbar conditions are among the most common presenting musculoskeletal complaints. Low back pain affects many people with pain and disability. The structural causes of low back pain can be varied but are generally managed without surgery because surgical treatment for isolated low back pain has limited high-quality data. Common degenerative conditions of the thoracolumbar spine include disk herniations, spinal stenosis, spondylolisthesis, and scoliosis. Each of these conditions can result in back pain, radiating lower extremity pain, or neurologic symptoms including a loss of motor strength or sensation. Evaluation includes a consistent and complete neurologic examination paired with appropriate diagnostic imaging (radiographs, MRI, etc). Nonsurgical management including medications, physical therapy, and injections often leads to successful relief of symptoms. Surgery is reserved for patients with persisting or progressive symptoms. Surgical treatment focuses on decompression of areas of neurologic compression concordant with patient symptoms. Open and minimally invasive techniques have demonstrated successful relief of pain and improvement in physical function. Conditions with spinal instability (spondylolisthesis, scoliosis) often necessitate surgical arthrodesis to stabilize or improve spinal alignment with successful pain relief and functional improvement demonstrated in high-quality comparative studies. The optimal surgical arthrodesis technique is controversial and requires matching patient needs and risk/benefit analysis and also considers surgeon experience.
Keywords: degenerative scoliosis; disk herniation; spinal stenosis; spondylolisthesis
Introduction
Degenerative thoracolumbar conditions are among the most common spine disorders encountered in the clinical setting. They encompass a wide range of disease, from disk herniations, subtle instability between vertebral segments causing nerve root compression to severe spinal stenosis, high-grade instability, and thoracolumbar spinal deformity. Low back pain is a highly prevalent condition and is among the most common causes of presentation to the doctor’s office. A recent systematic analysis of the Global Burden of Disease showed that low back pain is the fourth leading cause of disability among those aged 25 to 49 years.1 Over the past 30 years, low back pain increased from the 13th highest percentage of disability-adjusted life-years to the ninth highest, irrespective of age.1 Although most cases of back pain are self-resolving, underlying degenerative disease can cause persistent symptoms. The prevalence of lumbar spondylosis is approximately 3.6% globally and up to 4.5% in North America.2
This shift in global prevalence has put increased strain on health care systems with ever-increasing costs. In a 2021 study, the authors noted that only 1.2% of patients with back pain undergo a surgical intervention, but patients with persistent back pain account for approximately 30% of total US health care cost.3 One potential avenue for mitigating the economic effect of degenerative spine conditions is through increased scrutiny on timely and effective treatment and a shift toward
value-based care. Accurate diagnosis and treatment can rely on many technologic modalities including CT, MRI, and electromyography. However, practice heterogeneity exists with the use of these modalities between primary care physicians, pain management physicians, and spine specialists, further contributing to increased costs and inconsistent outcomes.
value-based care. Accurate diagnosis and treatment can rely on many technologic modalities including CT, MRI, and electromyography. However, practice heterogeneity exists with the use of these modalities between primary care physicians, pain management physicians, and spine specialists, further contributing to increased costs and inconsistent outcomes.
Common Clinical Presentations
Patients with thoracolumbar disease generally present with a combination of axial back pain and radicular symptoms. Axial back pain can have multiple etiologies including muscular, discogenic, and mechanical. Muscular back pain is the most common cause of back pain and commonly presents as stiffness and difficulty with bending. Discogenic back pain is directly related to intervertebral disk degeneration and tears within the anulus fibrosus. Mechanical pain is related to instability within a vertebral segment, which includes micromotion within the facet joints and can eventually lead to macroinstability in the form of a spondylolisthesis. Patients commonly complain of pain with lifting and prolonged standing. Although thoracolumbar decompressions and fusions have been shown to improve back pain in some patients, the results of surgery on axial low back pain are less reliable than surgery for radicular symptoms. These symptoms are therefore generally managed with nonsurgical measures.4
Radicular symptoms are caused by nerve root compression and include a combination of neurogenic pain, numbness/paresthesias, and weakness. These symptoms are localized within a dermatomal distribution correlating with the nerve roots being compressed. In patients with severe central canal stenosis, they can present with neurogenic claudication, which includes heaviness and cramping in the buttock and thighs, general fatigue in the lower extremities, and bilateral radicular pain in the legs that is worse with prolonged standing and improved with sitting or forward flexion. The etiology of radicular symptoms is easier to discern given their dermatomal distributions, which allows surgeons to correlate findings on advanced imaging with the patient’s symptoms.
In more severe thoracolumbar disease, patients can present with myelopathy or cauda equina syndrome. Myelopathy is caused by direct compression of the spinal cord and presents with gait instability as well as lower extremity pain, numbness, or weakness. Cauda equina syndrome is caused by severe compression of the nerve roots and presents as a combination of severe low back pain, lower extremity radiculopathy, weakness, bowel and/or bladder incontinence, loss of rectal tone, and saddle anesthesia.
Lumbar Disk Herniation
Lumbar disk herniations occur when there is a weakening or disruption in the outer anulus fibrosus, allowing the inner nucleus pulposus to herniate. Disk herniations are more common in men than women, with the peak incidence of lumbar disk herniations around the fourth and fifth decades of life, with a lifetime prevalence of 10%.5 The most common location of herniation is paracentral because of the absence of the posterior longitudinal ligament in that area. Paracentral disk herniations tend to compress the traversing nerve root in the lateral recess. Less common locations for herniation are central and lateral herniations. Central herniations do not always affect exiting nerve roots but may cause cauda equina syndrome when they are very large. Lateral herniations exit directly into the foramen or just lateral to it and affect the exiting nerve root at that level. The most common level for herniations to occur is at L5-S1, followed by L4-5, because of the high biomechanical strain at those levels.
Clinical Presentation and Workup
Lumbar disk herniations present with acute back pain and unilateral radicular symptoms, often after some strenuous activity or heavy lifting. In more severe, central herniations, patients can also present with cauda equina syndrome.
Initial workup of patients presenting with lumbar disk herniations is an accurate history and physical examination, carefully assessing for radicular symptoms. If there is concern for cauda equina syndrome, a rectal examination should be performed to assess for rectal tone and sensation. Patients with lumbar disk herniations may exhibit a positive straight-leg raise test and their radicular symptoms can be made worse with a Valsalva maneuver.
Radiographic evaluation begins with a standard set of weight-bearing lumbar spine radiographs. In the absence of red flags or significant neurologic deficit, further advanced imaging can be delayed to permit a trial of nonsurgical treatment. Further advanced imaging should be obtained if symptoms persist despite nonsurgical treatment or if a substantial neurologic deficit is present. The gold standard for diagnosing disk
herniations is MRI without contrast. This will show a disk fragment (hypointense on T2-weighted imaging) extruded into the spinal canal, foramen, or less frequently, lateral to the foramen (Figure 1). In cases where a patient is unable to undergo MRI, a CT myelogram should be obtained. In the scenario where there is concern for a recurrent disk herniation after a prior diskectomy, MRI with and without contrast should be ordered to help differentiate between a recurrent disk herniation versus postoperative scarring. Postoperative scar will fill with contrast, whereas disk material will not.
herniations is MRI without contrast. This will show a disk fragment (hypointense on T2-weighted imaging) extruded into the spinal canal, foramen, or less frequently, lateral to the foramen (Figure 1). In cases where a patient is unable to undergo MRI, a CT myelogram should be obtained. In the scenario where there is concern for a recurrent disk herniation after a prior diskectomy, MRI with and without contrast should be ordered to help differentiate between a recurrent disk herniation versus postoperative scarring. Postoperative scar will fill with contrast, whereas disk material will not.
Nonsurgical Management
An overwhelming majority of disk herniations (approximately 90%) will resolve spontaneously and do not require surgical intervention.6 The mainstay of treatment is management of symptoms with medications and physical therapy. The primary medications used are NSAIDs, muscle relaxants, and steroids. Physical therapy focuses primarily on lumbar extension exercises. Epidural corticosteroid injections can be considered as well. A systematic review showed that epidural injections are efficacious in treating patient pain and improving function in the setting of a lumbar disk herniation.7
 Figure 1 Sagittal and axial T2-weighted magnetic resonance images showing a large left-side lumbar disk herniation causing severe compression of the traversing left S1 nerve root. The patient presented with left-side posterior buttock, thigh, and calf pain with calf atrophy and weakness. |
Surgical Management
Indications for surgery in the setting of a lumbar disk herniation are persistent symptoms for greater than 6 weeks despite nonsurgical treatment or a severe or progressively worsening neurologic deficits. Acute cauda equina syndrome or signs and symptoms of myelopathy from conus medullaris compression also indicate surgical treatment. The primary surgical intervention for lumbar disk herniations is a diskectomy. These can be performed through either an open or minimally invasive approach.
The landmark Spine Patient Outcomes Research Trial (SPORT) compared patient-reported outcomes between nonsurgical and surgical management of patients with lumbar disk herniations. Overall, 1,244
patients were enrolled in the trial, which included both randomized and observational cohorts. Primary outcomes included the Oswestry Disability Index (ODI) and Medical Outcomes Study 36-Item Short Form (SF-36) bodily pain and physical function scores. Because of significant crossover between groups in the randomized cohort, the intent-to-treat analysis did not demonstrate any statistically significant differences between groups when looking at the primary outcome measures. However, an as-treated analysis combining both cohorts demonstrated significant improvement in pain, function, satisfaction, and self-rated progress in the patients who underwent surgery compared with the nonsurgical group. Although both groups showed overall improvement, the surgical group had a larger treatment effect early on, which narrowed by 2 years. In subsequent as-treated analyses at 4 and 8 years, both groups maintained their improvement, but the surgical group still demonstrated a slightly superior treatment effect over the nonsurgical group.8,9,10
patients were enrolled in the trial, which included both randomized and observational cohorts. Primary outcomes included the Oswestry Disability Index (ODI) and Medical Outcomes Study 36-Item Short Form (SF-36) bodily pain and physical function scores. Because of significant crossover between groups in the randomized cohort, the intent-to-treat analysis did not demonstrate any statistically significant differences between groups when looking at the primary outcome measures. However, an as-treated analysis combining both cohorts demonstrated significant improvement in pain, function, satisfaction, and self-rated progress in the patients who underwent surgery compared with the nonsurgical group. Although both groups showed overall improvement, the surgical group had a larger treatment effect early on, which narrowed by 2 years. In subsequent as-treated analyses at 4 and 8 years, both groups maintained their improvement, but the surgical group still demonstrated a slightly superior treatment effect over the nonsurgical group.8,9,10
In regard to outcomes between minimally invasive and open approaches for lumbar diskectomies, a systematic review and meta-analysis reported similar outcomes between both groups. However, patients undergoing minimally invasive diskectomies had an overall shorter length of hospital stay and earlier return to work than the open diskectomy cohorts.11
Thoracic Disk Herniation
Symptomatic thoracic disk herniations are much less common than lumbar disk herniations, with a reported incidence of approximately 0.5%.12 Thoracic disk herniations most commonly occur in the lower thoracic spine given the increased mobility and mechanical stresses in that area. Patients generally present with back pain and/or radicular symptoms localized to the chest wall/flank. In cases that involve spinal cord compression, patients can present with myelopathy.
Similar to lumbar disk herniation, a set of weight-bearing radiographs and MRI are the primary imaging modalities of choice. CT scans have greater utility in thoracic disk herniations to identify calcifications within the disk, which might alter the approach if surgery is required.
Surgical intervention is indicated in patients experiencing refractory pain despite at least 6 weeks of nonsurgical management or in the setting of severe or progressively worsening neurologic deficits or myelopathy. Given the presence of the spinal cord within the thoracic spine, a standard posterior approach for diskectomy as seen in the lumbar spine is not feasible because of the high risk of neurologic complications. Therefore, thoracic diskectomies are performed either through a posterolateral (transpedicular), lateral (costotransversectomy), or anterior (transthoracic) approach. An anterior approach is recommended for central calcified herniated disks but can introduce significant pulmonary morbidity. A posterolateral approach is often suitable for noncalcified lateralized thoracic disk herniations. Because of the high morbidity associated with transthoracic approaches, minimally invasive thoracoscopic techniques have gained popularity. However, there is currently no high-level comparative evidence to establish a clear benefit of minimally invasive techniques over open techniques for the management of thoracic disk herniations.
Lumbar Spinal Stenosis
Lumbar stenosis is a degenerative condition characterized by narrowing of the spinal canal. Given it is a degenerative disease, its incidence increases with age. It is estimated that approximately 20% of the population demonstrates radiographic findings of stenosis by the age of 40 years, which jumps to almost 50% by the age of 60 years.13 The narrowing is caused by a combination of multiple factors, most notably facet hypertrophy, hypertrophic ligamentum flavum, and bulging intervertebral disks, which are accelerated in areas of higher biomechanical stress such as the lower lumbar spine. The location of stenosis within the vertebral segment (central, lateral recess, foraminal) can vary based on each patient’s pathology. Eventually, as the spinal canal continues to narrow, it can cause compression of nerve roots, resulting in radiculopathy, neurogenic claudication, or rarely cauda equina syndrome.14
Clinical Presentation and Workup
Patients with symptomatic lumbar stenosis generally present with a combination of radiculopathy and/or neurogenic claudication. Patients should also be evaluated for claudication originating from vascular disease.
Workup should consist of weight-bearing lumbar spine radiographs, as well as flexion-extension views. These will generally show degenerative changes including decreased intervertebral disk heights and spurring of the end plates. It is important to evaluate for the presence of instability. In the presence of neurologic symptoms, MRI without contrast should be obtained.
This will often show evidence of ligamentum flavum hypertrophy, bulging disks, and facet hypertrophy leading to central canal, lateral recess, and/or foraminal stenosis.14
This will often show evidence of ligamentum flavum hypertrophy, bulging disks, and facet hypertrophy leading to central canal, lateral recess, and/or foraminal stenosis.14
Nonsurgical Management
The first line of treatment for spinal stenosis is a combination of medications, physical therapy, and corticosteroid injections. Medications primarily include NSAIDs and neuromodulators (eg, gabapentin, pregabalin). When patients have significant nerve root irritation, an oral steroid taper can be used. Narcotics should be avoided given their depressive and addictive qualities. Although corticosteroid injections can provide temporary symptomatic relief, one study found in a subgroup analysis of the SPORT trial that patients who received injections before surgery showed less improvement in patient-reported outcomes postoperatively (SF-36).15 A Cochrane systematic review from 2016 investigated surgical versus nonsurgical treatment for spinal stenosis and did not find strong evidence to support one over the other. However, as expected, complications were significantly higher in the surgical groups (ranging from 10% to 24%) and no complications were reported in the nonsurgical groups.16
Surgical Management
Surgical management for lumbar stenosis is indicated in patients with lumbar spinal stenosis who have persistent neurologic symptoms despite nonsurgical treatment efforts. The primary surgical intervention for lumbar stenosis is a facet-sparing laminectomy. These can be performed through either an open or minimally invasive approach. In instances where iatrogenic instability has been introduced, either through a pars fracture or disruption of the facet joint at a given level, patients should undergo an arthrodesis at that level. Certain patterns of foraminal lumbar stenosis might necessite a fusion despite no evidence of instability. In the case of front-back foraminal stenosis due to facet hypertrophy, direct decompression with a Kerrison rongeur might be difficult and/or innefective. Therefore, a facetectomy with subsequent instrumented fusion will decompress the foramen more reliably. Additionally, in patients with significant top-down stenosis due to disk degeneration, some type of interbody fusion that helps restore foraminal height is the most appropriate treatment option.
The SPORT trial also compared patient-reported outcomes between nonsurgical and surgical management of patients with lumbar stenosis. The study enrolled 654 patients in total and included both randomized and observational cohorts. By 8 years, 52% of patients were randomized to nonsurgical care and underwent surgery. Again, an intent-to-treat analysis found no difference in primary outcomes between these patients. The as-treated analysis of the randomized cohort found that the treatment effect of surgery diminished after the fourth year and became insignificant after the fifth year.17,18 In contrast, the as-treated analysis of the observational cohort found that the treatment effect remained statistically significant for all three primary outcomes at 8 years.19 A combined as-treated analysis also demonstrated continued benefit from surgery.
Regarding open versus minimally invasive techniques, a 2019 prospective randomized controlled trial (RCT) demonstrated similar outcomes between open and minimally invasive techniques for improvements in pain, function, and disability at 3 years. However, the minimally invasive group had, on average, shorter length of hospital stay and a lower complication rate.20 When looking at different minimally invasive techniques, another recent RCT showed that the use of a biportal technique/endoscopy had favorable clinical outcomes, less pain, and shorter length of hospital stay compared with microscopic surgery with tubular retractors for the treatment of lumbar stenosis.21
Lumbar Spondylolisthesis
Spondylolisthesis is defined as the anterior translation of one vertebral segment relative to an adjacent vertebral segment. Although it can be seen in the cervical spine and more rarely in the thoracic spine, it is most commonly encountered in the lumbar spine. Several different etiologies have been identified and were initially organized into the following broad categories according to the Wiltse classification: type I, congenital dysplasia with sacral doming; type II, isthmic; type III, degenerative; type IV, traumatic; and type V, pathologic.22 An additional sixth subtype, postsurgical, can be added to the original five to describe instability in or adjacent to the prior surgical bed. Degenerative spondylolisthesis is the most common subtype and differs from the other conditions in that the neural arch is still intact, whereas in the other conditions, the bony architecture connecting adjacent vertebral segments is disrupted. This can be a result of fracture or a disrupted pars interarticularis because of chronic stress fracture, tumor, or a developmental defect. The pathophysiology and management of degenerative spondylolisthesis
and isthmic spondylolisthesis are covered as these are the most commonly encountered pathologies in the general population.
and isthmic spondylolisthesis are covered as these are the most commonly encountered pathologies in the general population.
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