Patient Selection for Spine Surgery

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Chapter 27 Patient Selection for Spine Surgery

Between 70% and 85% of all people will have back pain at some time in their lives.¹ Lumbar spine disorders are the most common cause of disability in persons younger than 45 years of age.² More than 500,000 lumbar procedures are performed each year for the treatment of lumbar spine disorders.³ Of those with low back pain (LBP), approximately 151,000 undergo a lumbar fusion each year.⁴ Given the large number of individuals that experience back pain, one can only surmise that the number of surgeries performed on the lumbar spine will continue to increase. The vast majority of patients with lumbar spine problems do not require surgery. Nonoperative treatment, however, is very expensive, and the data regarding its efficacy demonstrate equivocal results, at best. It is important for the physician to truly appreciate the indications for lumbar spine surgery, and also to become adept at determining the optimal surgical procedure when surgery is indeed indicated. Based on the best evidence available, this chapter addresses patient selection, clinical management results, and surgical outcomes of surgery for LBP.

Patient Evaluation

Most commonly, the preoperative evaluation should include the history, physical examination, and any warranted imaging tests, such as radiographs, MRI, and CT. Occasionally, blood work, electromyographs (EMGs), and bone scans are used in the evaluation as well. The bone quality should be evaluated with a dual-energy x-ray absorptiometry (DEXA) scan 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 very detailed description of the radiation of pain, and any constitutional symptoms. The past medical history also is very 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 also should be documented. Selective nerve root blocks, even if the relief given the patient is for only a few days or even hours, provide the surgeon with a great deal of information. Finally, the assessment of the patient’s level of energy, mood, affect, and pain pattern is paramount 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 and/or claudicant central stenosis are present, especially with associated loss of sensation and/or motor strength. Imaging evidence of instability makes the surgeon’s decision a bit easier, especially when coupled with “hard” neurologic findings. Greater difficulty arises when no deficits are present. In such cases, conservative nonoperative treatment should be considered most strongly.

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. 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. A patient who rates the pain as a 1 or 2 on a scale from 1 to 10 and is still working and able to perform daily activities will be managed differently from a person who cannot work, is on disability, and rates the pain 8 out of 10.

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 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.⁵ Trief et al. 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.⁵ In randomized controlled trials (RCTs) from Fairbank et al.⁶ and Fritzel et al.,⁷ patients in litigation did worse after spinal fusion than their counterparts who were not in litigation. With these studies, however, both subgroups that underwent surgery (with and without litigation) did better than the matched patients who underwent conservative management. The group of patients with the worst response overall were the patients in litigation who received conservative treatment. This, however, was not statistically significant. In another RCT by Haag et al.,⁸ several sociologic factors were analyzed 2 years after fusion (workers’ compensation, disability pension, unemployment, sick leave due to back pain, cohabitant/married). Overall, the operative group did better than the conservative treatment group. However, the groups that realized the greatest improvement were patients with a lighter job, not cohabiting/married, and not on sick leave. In a recent literature review, Mroz et al.⁹ demonstrated that people in litigation usually fare poorly. Nevertheless, they do even worse with conservative treatment. They concluded that socioeconomic factors should not be the sole factor to contraindicate surgical treatment for back pain. Health-related factors such as obesity and smoking also play a role. Recent studies have demonstrated an increase in surgical site infections in morbidly obese patients.¹⁰ Elderly obese patients undergoing lumbar surgery report a high rate of dissatisfaction with the surgery outcome compared with nonobese patients.¹⁰ 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.¹¹ 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.

Chronic 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.¹² 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.¹³ 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.¹³

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.¹⁴ 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.¹⁵ 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 are the shoulder and upper extremity peripheral nerves examination when examining the neck. It is very important to be aware of and not miss the “red flag” signs 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.¹⁶

In summary, it is very difficult to determine whether a surgical intervention will be beneficial to 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 MRI examination (Fig. 27-1A) shows stenosis, predominantly foraminal (not shown in this cut). No deformity or instability is observed. On standing radiographs (Figs. 27-1B and C), 12-cm coronal and 17-cm sagittal imbalances are discovered. The imbalances significantly affect the clinical decision-making process.

FIGURE 27-1 Case presentation 1:The importance of standing radiographs in the preoperative evaluation. See text for details.

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^,18 (same population, different follow-up) comparing low-grade spondylolisthesis patients with those who presented with either chronic LBP or 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 (1–2 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 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.¹⁹ Sinaki et al. have shown, in a retrospective analysis, significant benefit of flexion exercises in comparison with extension exercises to control the symptoms of low-grade spondylolisthesis.²⁰ Daniel et al. 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.²¹

Low-Grade Spondylolisthesis: To Fuse or Not to Fuse? Role of Instrumentation? Best Approach?

When assessing the role of fusion in the management of adult low-grade spondylolisthesis, Herkowitz and Kurz ²² performed an RCT comparing decompression alone with decompression and uninstrumented PLF (posterolateral fusion). A mean 3-year follow-up demonstrated better outcomes for leg and back pain for the fusion group (P = .0001). Other authors in prospective nonrandomized²³ and retrospective²⁴^–²⁶ 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 et al.²⁷ 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 vs. noninstrumented). Kornblum et al. ²⁸ combined the noninstrumented patients from both the Fischgrund²⁷ and the Herkowitz²² 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 ²⁹ 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 et al.³⁰ 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 et al.³¹ 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 et al.³² 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,³³ making the following points:

• The achievement of a solid fusion is associated with better clinical outcomes.

• The adjunctive use of pedicle screw instrumentation improves fusion rates.

• While instrumentation does not show significant improvement on patient-scored outcome measures, the positive effect on fusion alone warrants its use.

• 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. Questions that must be asked include: 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 in the anular region may be triggered by chemical and mechanical sensitization of dorsal anular nociceptors.³⁴ 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 anulus. In the degenerated disc, the innervation is deeper and more extensive, with some nerve fibers penetrating into the nucleus pulposus.³⁵ Pain also may be produced by the sensitization and irritation of nerve endings in the end plate.³⁴^–³⁸ 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.³⁹^–⁴¹ 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 more than 50 years ago, 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.⁴² 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 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.⁴²

Several authors have attempted to determine the prevalence of discogenic pain in patients suffering from LBP. In one of the most cited studies, Schwarzer et al. found the incidence of IDD (defined in his study by positive discography) to be 39% in 92 patients with chronic LBP.⁴³

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.⁴⁴

Some studies have attempted to correlate discography results with surgical findings and outcomes. Colhoun et al. 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.⁴⁵

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 et al. 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 who did not have preoperative discography.⁴⁶ In summary, the lack of strong evidence for the use of discography in fusion surgery to treat degenerative disc disease (DDD) and the methodologic flaws in the existing studies make interpretation of the data exceedingly difficult. Based on the data that are available, the results are mixed as to whether or not preoperative discography improves surgical outcomes in patients with discogenic LBP.^47,⁴⁸

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.^49,⁵⁰ Although some authors have observed improvement in pain⁵¹ 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,⁵² and found that the technique is a poor predictor of successful fusion surgery.^52,⁵³ Currently, this practice has fallen out of favor.

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%.⁵⁴ Fritzell et al., 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, while only 18% of patients in the conservative group achieved similar results.⁷ In another RCT comparing conservative treatment with PLF to treat chronic LBP, Brox et al. report no difference between the two groups.⁵⁵

In the Pro-Disc total disc replacement IDE RCT (2-year follow-up), Zigler et al. report 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).⁵⁶ Guyer et al.⁵⁷ recently published the results of the 5-year follow-up of the U.S. Food and Drug Administration’s 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 analogue 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.⁵⁸ 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) are found in smaller, less strictly controlled studies. Most of them were case series.⁵⁹^–⁶³

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. 27-2A) showed degeneration of the L4-5 and L5-S1 discs. Coronal MRI showsed L4-5 bilateral facet joint incompetence with an increased amount of synovial fluid and early degenerative changes (Fig. 27-2B). Fig 27-2C 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.

FIGURE 27-2 Case presentation 2: It is extremely difficult to determine the location of the pain generators in low back pain. Attention to detail in the history, physical examination, and imaging components of the evaluation may be helpful. Each case is unique. See text for details.

Case Presentation 3: Patient Selection Is Paramount

A 42-year-old female physical therapist and runner (Fig. 27-3) had given up running due to a 2-year history of mechanical LBP. She exhibited no radicular symptoms. Pain had become incapacitating and was interfering not only with running but with daily activities. Preoperative radiographs were obtained (see Figs. 27-3A and B). On MRI (see Fig. 27-3C), the only abnormality was degeneration of the L5-S1 disc. After several months of aggressive medical management and after thorough psychosocial evaluation, the patient underwent an L5-S1 ALIF with percutaneous pedicle screw fixation (Figs. 27-3D and E). She is pain free following surgery. She won a 10K race 6 months postoperatively.