Summary of Key Points
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Unlike other musculoskeletal disorders, the etiology of back pain is often difficult to determine and lacks clear indications and criteria for surgical or nonsurgical intervention.
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Correlating imaging findings with pain is imprecise, and poor results are clearly associated with improper patient selection or inappropriate treatment.
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A careful history and physical examination, as well as a trial of nonoperative management when appropriate, are crucial to the process of determining whether or not a patient might benefit from surgical intervention.
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The most challenging patients are those who suffer back pain with no neurologic deficit, no radicular pain, no instability, no deformity, and who have not responded to an extensive medical management program.
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Patients with low back pain should be worked up on a case-by-case basis. Provocative testing can be used as an adjunct to diagnostic imaging in selected cases.
From 70% to 85% of North Americans will have back pain at some point in their lives, and as much as 4% of the general population suffers from chronic back pain with a neuropathic component. According to the Centers for Disease Control and Prevention, spinal fusions are among the most costly interventions in medicine, with the total cost reaching $13 billion in 2011 in the United States alone, exceeding the cost of all total knee replacement procedures, which outnumber spine fusions by almost 2 to 1. The cost of nonsurgical modalities such as physical therapy, pain interventions, and alternate therapies must also be taken into account. The steadily increasing number of spine procedures performed yearly places a significant burden on already strained health care resources. Unlike other musculoskeletal disorders, the etiology of back pain is often difficult to determine, while clear indications and criteria for surgical or nonsurgical intervention are lacking. Correlating imaging findings with pain is imprecise, and poor results are often associated with improper patient selection or inappropriate treatment. The majority of patients with lumbar spine problems do not require surgery. However, nonoperative treatment modalities are costly, and the data regarding their efficacy are equivocal at best. Selecting the optimal procedure for patients who might benefit from surgical intervention is crucial in achieving successful outcomes. Based on the best evidence available, this chapter addresses patient selection, clinical management results, and surgical outcomes of surgery for back pain.
Patient Evaluation
Preoperative evaluation consists of the history, physical examination, and imaging when warranted. Occasionally, blood work, electromyographs (EMGs), and bone scans are used in the evaluation as well. A dual-energy x-ray absorptiometry (DEXA) scan to evaluate bone quality is warranted whenever osteoporosis is of concern, especially when major reconstructive surgery is contemplated.
The history is certainly the most important component of the diagnostic process. It also is used to guide treatment. It should include the duration of symptoms, location of pain, any exacerbating and relieving maneuvers, a detailed description of the radiation of pain, and any constitutional symptoms. The past medical history also is important, particularly smoking habits. The history of, and response to, conservative management strategies employed for the current complaint (e.g., physical therapy, acupuncture, chiropractic treatments, injections, weight management) must be documented. The quality, intensity, and quantity of the conservative management should also be determined. The type of, number of, and response to injections should be documented as well. It is important to note any relief achieved with selective nerve root blocks, even if only temporary. Finally, the assessment of the patient’s level of energy, mood, affect, and pain pattern is useful to diagnose problems such as depression, fibromyalgia, and anxiety that may very well manifest as back pain. It is much easier to recommend surgical treatment for the lumbar spine when clear symptoms of radiculopathy or claudicant central stenosis are present, especially with associated loss of sensation or motor strength. Imaging evidence of instability influenced the decision to operate, especially when coupled with neurologic findings. The lack of such findings usually tips the balance in favor of conservative management.
The differential diagnosis of identifiable causes for back pain overlaps with psychosocial diseases and conditions, which can be the source of significant frustration for both surgeon and patient. Medications also should be recorded. Preoperative narcotic medication use is significantly associated with depression and anxiety in addition to decreased postoperative opioid independence, longer hospital stays, and higher complication rates. Every attempt should be made not to place the patient with chronic back pain on narcotic medication. The detoxification process is a difficult and long one, but is paramount for the success of the treatment. The help of a pain management specialist and psychosocial support usually is quite beneficial. The intensity and duration, as well as the disability caused by the pain, also play a major role in the decision-making process.
Use of the visual analogue scale (VAS) to assess the extent and distribution of pain should also be considered. With the VAS, the patient specifies the level of pain by indicating a position along a continuous line between two end points (0 and 10). The VAS obtained preoperatively and postoperatively can be compared to examine the efficacy of treatment.
Individual factors such as work-related injuries and psychosocial support also should be assessed. Low job satisfaction, litigation, and workers’ compensation can be predictive of a poor outcome. Trief and colleagues looked at 160 patients who underwent lumbar spinal fusion. The patients completed preoperative questionnaires regarding their mental health, functional status, workers’ compensation, and job satisfaction. Patients with higher mental component scores reported less back and leg pain. In randomized controlled trials (RCTs) from Fairbank and colleagues and Fritzel and colleagues, patients in litigation did worse after spinal fusion than their counterparts who were not in litigation. Health-related factors such as diabetes, obesity, and smoking significantly affect surgical outcomes and complications. Studies have demonstrated an increase in surgical site infections in morbidly obese patients. Elderly obese patients undergoing lumbar surgery report a high rate of dissatisfaction with the surgery outcome compared with nonobese patients. Smoking is known to be a predictor of poor surgical outcome in lumbar fusion surgery. Habitual nicotine use is thought to decrease the revascularization of the graft, slowing healing rates and increasing the risk of infection and of pseudarthrosis. There are no clear guidelines on preoperative lumbar fusion and cessation of smoking. However, patients should be encouraged to stop smoking as early as possible before undergoing surgery to increase the chance of long-term success. Diabetes with poor glycemic control imparts a higher complication and mortality risk, as well as poorer outcomes in both cervical and lumbar spine surgery.
Chronic low back pain (LBP) may trigger anxiety, depression, and fear, thereby changing the way people perceive pain. The Minnesota Multiphasic Personality Inventory (MMPI) is one of the most widely used personality tests. Patients are asked to answer questions regarding their anxiety and depressive symptoms. The scale attempts to identify patients who are preoccupied with their symptoms, are depressed, or feel a high level of anxiety, because these individuals tend to fare worse. These factors are more predictive of a good outcome than physical findings or radiographic measures. Studies have suggested that fear-avoidance beliefs about physical activity and work might form specific cognitions intervening between LBP and disability. A Fear-Avoidance Beliefs Questionnaire (FABQ) was developed, based on theories of fear and avoidance behavior and focused specifically on patients’ beliefs about how physical activity and work affected their LBP. FABQ screening could be useful in patient evaluation for lumbar surgery because it could accurately identify subjects with elevated levels of fear.
After the history is collected, the physical examination should focus on deficits in sensation, muscular weakness, deep tendon reflexes, and any abnormal reflexes such as a Hoffman or Babinski reflex. The clinician also should be aware of any suspicious symptoms or signs that are consistent with malingering. These physical examination findings include pain at the top of the tailbone, entire leg pain or numbness, giveaway weakness, persistent pain, intolerance to treatment, and multiple emergency admissions to hospitals with simple backache (Waddell signs). Clinicians should also be wary of patients who present with a gross limp, use of physical supports (e.g., corset, crutches, transcutaneous electrical nerve stimulation [TENS] unit), or any continuous or repetitive movement. A well-performed hip examination that includes palpation of the greater trochanter to rule out bursitis as well as rotational maneuvers to rule out primary hip joint pathology is imperative when examining the lumbar spine, as is examination of the shoulder and upper extremity peripheral nerves when examining the neck. It is important to be aware of and not miss the red flags in a patient with pain of spinal origin. The clinician should consider ordering imaging studies after the first encounter in patients with a history of trauma, night pain, weight loss, cancer, persistent weakness, urinary or fecal incontinence, saddle anesthesia, or constitutional symptoms.
In summary, it is difficult to determine whether a surgical intervention will benefit a patient who presents with LBP. Radiographic evidence of instability may support the argument for surgery. A thorough understanding of the psychosocial situation is imperative. The optimal surgical candidate is a patient who is highly motivated to improve, preferably is not involved in litigation, is not on disability, is not depressed, is physically fit, and does not smoke. This patient has undergone extensive medical management and still is not happy with the result, has significant pain or disability, has a concordant physical examination and imaging tests, is familiar with the results of surgery for LBP, trusts his or her surgeon, and is willing to proceed with surgery. Such patients with back pain represent a significant minority of all back pain patients.
Case Presentation 1: The Importance of Standing Films
The patient presented with a chief complaint of L3, L4, and L5 radiculopathy in the right lower extremity. The magnetic resonance imaging (MRI) examination ( Fig. 25-1A ) shows stenosis, predominantly foraminal (not shown in this cut). No deformity or instability is observed. On standing radiographs ( Figs. 25-1B and C ), 12-cm coronal and 17-cm sagittal imbalances are discovered. The imbalances significantly affect the clinical decision-making process.
Low Back Pain: Evidence for Treatment
Certain criteria have been historically accepted in discussing the indications for lumbar fusion. Trauma-related injuries such as unstable fractures, fracture-dislocations, or traumatic spondylolisthesis are all acceptable reasons to perform a lumbar fusion. Scoliosis, infection, and tumor with instability or neurologic deficit also may be indications for surgery. With other pathologies, the indications are not nearly as clear.
Low Back Surgery for Adult Low-Grade Spondylolisthesis
Conservative versus Surgical Treatment
Two RCTs (same population, different follow-up) comparing low-grade spondylolisthesis patients with those who presented with either chronic LBP, radiculopathy, or both, treated either with fusion or conservative treatment, found that the surgical group did statistically and clinically better, as assessed by pain scores and the Disability Rating Index (DRI). Even though the long-term follow-up (5 years) showed that some of the initial improvement (1 to 2 years) had been lost, 76% of the patients in the surgical group still considered their overall outcome as “much better” compared with only 50% in the conservative group. Another prospective RCT found a significant difference when treating patients with low-grade spondylolisthesis with an advanced core strengthening program performed by a specialist physical therapist and a control group that performed simple exercises prescribed by their primary physician at 3, 6, and 30 months. The advanced exercise group had better outcomes. Sinaki and coworkers have shown, in a retrospective analysis, a significant benefit of flexion exercises in comparison with extension exercises to control the symptoms of low-grade spondylolisthesis. Daniel and colleagues reported very poor results with conservative treatment for spondylosis, including the use of a full-time thoracolumbar orthosis. Twenty-nine of 31 patients failed treatment and progressed to surgery.
Low-Grade Spondylolisthesis: To Fuse or Not to Fuse? What is the Role of Instrumentation and the Best Approach?
When assessing the role of fusion in the management of adult low-grade spondylolisthesis, Herkowitz and Kurz performed an RCT comparing decompression alone with decompression and uninstrumented posterolateral fusion (PLF). A mean 3-year follow-up demonstrated better outcomes for leg and back pain for the fusion group ( P = .0001). Other authors in prospective nonrandomized and retrospective series also support decompression and fusion over decompression alone when spondylolisthesis is present.
The role of instrumentation in achieving fusion and improving clinical outcomes in low-grade spondylolisthesis was studied by Fischgrund and colleagues in an RCT. Patients were divided into two groups: (1) decompression and noninstrumented PLF and (2) decompression with instrumented PLF (pedicle screws). The fusion rate was 83% versus 45%, respectively, for the instrumented versus noninstrumented groups. Clinical outcomes, however, were similar for both groups (78% vs. 85%, instrumented versus noninstrumented). Kornblum and associates combined the noninstrumented patients from both the Fischgrund and the Herkowitz studies to compare 47 patients with either a solid fusion or a nonunion. The solid fusion group had a satisfactory result in 86% of patients, whereas patients in the nonunion group had 56% satisfactory results at 5 to 14 years of follow-up.
Two additional RCTs were performed. In these studies, instrumentation was associated with higher fusion rates and better clinical outcomes for low-grade spondylolisthesis. Zdeblick reported a 65% fusion rate and 71% satisfactory clinical outcome in the noninstrumented group, versus a 95% fusion rate and 95% satisfactory clinical outcome in the rigid instrumentation group. Bridwell and colleagues randomized 43 patients into three groups: (1) decompression only, (2) decompression with uninstrumented posterolateral fusion, and (3) decompression with rigid pedicle screw instrumentation posterolateral fusion. The fusion rates were 33% and 87.5% for groups 2 and 3. Clinical improvement was 30%, 33%, and 83.3% for groups 1, 2, and 3, respectively.
Kwon and colleagues reviewed the literature regarding surgical approaches to low-grade spondylolisthesis (ventral/dorsal/360 degrees). In a total of 1100 patients from 34 studies (4 of which were RCTs), the clinical results and fusion rates were better when the combined ventral/dorsal approach was used. When comparing anterior lumbar interbody fusion (ALIF) plus PLF with instrumentation versus ALIF plus instrumentation without PLF, Shofferman and coworkers found that both groups had improvement in function, but no difference in results could be detected.
In 2005, the Scoliosis Research Society released a consensus statement on the treatment of low-grade acquired/isthmic spondylolisthesis, making the following points :
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The achievement of a solid fusion is associated with better clinical outcomes.
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The adjunctive use of pedicle screw instrumentation improves fusion rates.
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While instrumentation does not show significant improvement on patient-scored outcome measures, the positive effect on fusion alone warrants its use.
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There is no consensus regarding the approach for fusion—interbody, dorsolateral, or combined.
Lumbar Fusion for Back Pain without Signs of Instability
Lumbar fusion or surgery to treat low back pain–related symptoms, presumably from intervertebral disc disease (IDD), black disc syndrome, or “discogenic” LBP, is arguably the most controversial surgical indication in spine surgery. One reason is that the natural history of IDD is poorly defined, and the condition often is self-limiting and benign. Several questions must be asked: What specifically causes the pain in IDD? Does selective fusion of a segment lead to pain relief? Is the disc the only source of pain? How important is facet arthritis, inflammation of adjacent tendons, or muscle fatigue in LBP generation? Are other levels involved?
Pain originating in the annular region may be triggered by chemical and mechanical sensitization of dorsal annular nociceptors. In the 1940s and 1950s, the disc itself was thought to have no nerve supply and, therefore, to have no possibility of generating pain. Subsequent studies have proved this theory wrong. In the normal human disc, sensory nerves extend into the outer third of the annulus. In the degenerated disc, the innervation is deeper and more extensive, with some nerve fibers penetrating into the nucleus pulposus. Pain also may be produced by the sensitization and irritation of nerve endings in the end plate. This model of chemical nociception is supported by numerous studies showing disc immunoreactivity to inflammatory mediators such as substance P and calcitonin as well as elevated levels of prostaglandin E2, interleukin (IL)-2, IL-6, IL-8, phospholipase A2, leukotrienes, thromboxane B2, and tumor necrosis in the degenerated intervertebral disc. It is now generally accepted that intervertebral discs can be a significant source of back pain. Normal discs resist pain with stimulation because they lack both the chemical sensitization and the mechanical overloading seen in diseased discs.
Since its advent in the 1960s, the use of discography has been mired in controversy. Discograms are pain-provoking tests that show radiographic abnormalities of the disc. The procedure is performed with the patient awake in order to assess the level of pain he or she experiences upon injection of normal saline or a water-soluble dye into the intervertebral disc at different segments of the lumbar spine suspected of being abnormal. A positive discogram is associated with the elicitation of a concordant pain response coupled with pain-related behavior (e.g., grimacing, guarding, withdrawing, and verbalizing). Provocative discography is no longer used for the routine evaluation of radiculopathy, having been largely replaced by the advent of noninvasive, more sensitive tests such as computed tomography (CT) and MRI. The evidence that these modalities are not only safer but also more accurate than plain discography in detecting herniated nuclear material is irrefutable.
The fact that imaging alone is not sufficient to guide patient selection has led to the consideration of provocative testing as an adjunct to diagnostic imaging. Several authors have attempted to determine the prevalence of discogenic pain in patients suffering from LBP. Schwarzer and associates found the incidence of IDD (defined in his study by positive discography) to be 39% in 92 patients with chronic LBP.
The first study to question the validity of discography was published in 1968 by Holt, who found false-positive results in 37% of 30 asymptomatic subjects. All participants were prisoners.
Some studies have attempted to correlate discography results with surgical findings and outcomes. Colhoun and colleagues evaluated surgical outcomes in 162 patients who underwent preoperative discography for axial LBP. In the 137 patients whose discography provoked pain, 89% had a favorable outcome at a mean follow-up of 3.6 years. In the 25 patients whose discs showed morphologic abnormalities but no provocation of symptoms, only 52% reported significant benefit.
Although Colhoun reported successful data, some other studies have not had such positive conclusions. The predictive value of provocative discography on surgical outcome also was assessed in a study by Madan and coworkers involving 73 patients with chronic LBP. Thirty-two patients underwent spinal fusion based on pain provocation during discography; the remaining 41 patients had surgery without discography. In the discography group, 75.6% of patients had satisfactory outcomes at a minimum 2-year follow-up versus 81.2% in the group of patients who did not have preoperative discography. A review of the literature on discography in an American Association of Neurological Surgeons (AANS) guideline update for fusion for degenerative spinal disorders concluded that there is not enough evidence to conclusively support it as a stand-alone test to determine treatment strategies. Of note, the data are based mainly on retrospective studies due primarily to the lack of RCTs. Discography was recommended as a diagnostic option as long as patients were informed about the possible association between the procedure and the potential progression of degenerative disc disease. In summary, the lack of strong evidence for the use of discography in fusion surgery to treat degenerative disc disease (DDD) and the methodological flaws in the existing studies make interpretation of the data exceedingly difficult. Based on the data available, it could be considered as a diagnostic adjunct on a case-by-case basis.
Extensive studies have been performed regarding the use of temporary external fixation before lumbar fusion surgery to help distinguish the area of disease. The aim of externally fixing a lumbar spinal motion segment is to prevent movement, therefore alleviating pain. This may be predictive of subsequent surgical success. Although some authors have observed improvement in pain and found good prediction for satisfactory fusion surgery outcomes with this technique, others found a high rate of complications such as pin site infection, neurologic compromise, and cerebrospinal leakage, and found that the technique is a poor predictor of successful fusion surgery. Currently, this practice has fallen out of favor.
Classically, when surgery is indicated, patients with spinal stenosis and no spondylolisthesis are treated with decompression only. A study assessing 9501 patients in the Swedish registry concluded that patients with predominant back pain are more satisfied with decompression and fusion than decompression alone. This was not observed in patients with predominant leg pain.
Clinical Results for the Conservative and Surgical Treatment of Mechanical Low Back Pain
The fact that many patients with DDD suffer from other concomitant causes of back pain that may not respond to operative intervention continues to bring significant controversy to the clinical decision-making debate. Although outcome studies for spinal arthrodesis vary widely, it is generally acknowledged to be less beneficial than surgery for radicular pain, with success rates ranging from less than 50% to almost 90%. Fritzell, in a multicenter RCT, compared conservative treatment to spinal fusion for the treatment of chronic LBP. Forty-six percent of the surgical group reported good to excellent results, whereas only 18% of patients in the conservative group achieved similar results. In another RCT comparing conservative treatment with PLF to treat chronic LBP, Brox and associates reported no difference between the two groups.
In the Pro-Disc total disc replacement IDE RCT (2-year follow-up), Zigler and coworkers reported successful outcomes in 54.9% of patients undergoing ALIF plus PLF, compared with a 69% success rate in patients receiving the disc replacement ( P = .03). Guyer and colleagues published the results of the 5-year follow-up of the U.S. Food and Drug Administration’s Investigational Device Exemptions (IDE) trial of the Charité disc. Success results were 57.8% for total disc replacement and 51.2% for the fusion group (ALIF; P = .03). There was no difference between groups in the Oswestry Disability Index (ODI), visual analog scale, or 36-Item Short Form Health Survey (SF-36) scores. The authors concluded that there was no clinical difference between groups, and that these results were consistent with the 2-year Charité outcomes previously published. Greater clinical success (i.e., good results between 70% and 90%) in lumbar fusion surgery for back pain (using different techniques, e.g., uninstrumented and instrumented PLF, ALIF, posterior lumbar interbody fusion, transforaminal lumbar interbody fusion) is found in smaller, less strictly controlled studies. Most of them were case series.
Nonsurgical Options
One review concluded that although lumbar intra-articular facet injections are not recommended for the treatment of chronic lower-back pain, medial branch nerve blocks or ablation are useful to provide short-term relief of facet-mediated chronic lower-back pain without radiculopathy. Diagnostic medial branch nerve blocks with 80% improvement may predict a favorable response to nerve ablation but not lumbar fusion. The evidence regarding trigger point injections for chronic lower back pain without radiculopathy was equivocal. Epidural steroid injections may provide a small surgery-sparing effect in the short term compared with control injections. Although widely used, the long-term effect of epidural, facet, medial branch, or trigger point injections is still to be determined.
Cell-based therapies to treat lumbar disc degeneration offer an attractive solution to current conservative and especially surgical interventions. The success of such intervention relies on the assumption that disc degeneration is the cause of symptoms and that repairing or stopping its progression would lead to pain relief. Numerous basic science studies show us that these assumptions may very well hold true. Clinically, the experience is much smaller, yet equally promising. Coric has shown significant clinical and radiographic improvement after injecting degenerated discs with juvenile chondrocytes.
Case Presentation 2: Each Case Is Unique
A 21-year-old female college student presented with a history of LBP for 6 years despite multiple trials of physical therapy and oral medication. Pain was worsened in extension and better in flexion. There was no radiculopathy. Sagittal MRI ( Fig. 25-2A ) showed degeneration of the L4-5 and L5-S1 discs. Coronal MRI showed L4-5 bilateral facet joint incompetence with an increased amount of synovial fluid and early degenerative changes ( Fig. 25-2B ). Figure 25-2C showed normal L3-4 facets for comparison. The patient enjoyed 100% pain relief (at 1 and 4 months) with bilateral L4-5 facet injections with steroids and bupivacaine.
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