Overview

Adult degenerative scoliosis remains a challenging problem for patients and spine surgeons. Treatment decisions can be complicated by social, psychologic, and medical factors. Patient outcomes can be optimized by understanding the natural history of degenerative scoliosis as well as the various nonoperative and operative treatment options.

Adult degenerative scoliosis can develop de novo as a result of asymmetric disk and facet degeneration in a spine with relatively normal alignment, or it can occur as a result of asymmetric disk and facet degeneration associated with adolescent idiopathic scoliosis (AIS). The natural progression of adult scoliosis varies from individual to individual. Glassman and colleagues showed that patients with degenerative scoliosis have significantly lower SF-36 scores in 7 of 8 categories than age-matched controls. These patients also scored lower in 7 of 8 categories compared with patients who had back pain, sciatica, and hypertension. The decision to continue with nonoperative treatment or to pursue operative intervention remains complex and difficult, despite the fact that these patients have lower health-related quality of life scores. These patients must balance issues of progressive deformity, pain, cosmesis, overall medical condition, and the extent of potential intervention in their decision making.

Natural History

The true natural history of degenerative scoliosis, either from previously existing AIS or de novo scoliosis, is not fully understood. The recommendation for fusion of AIS curves during adolescence comes in large part from the hope that the surgery will prevent curve progression. Forty-year follow-up data out of Iowa suggest that thoracic curves measuring more than 50 degrees and lumbar curves measuring more than 30 degrees will progress at a rate of approximately 1 degree per year. However, these data represent an average of all subjects, thus not every patient will demonstrate curve progression. In fact, many patients’ curves remain stable throughout their entire life. Scoliosis has been associated with psychosocial consequences, slightly higher rates of back pain, and decreased cardiac and pulmonary function in curves measuring over 100 degrees. In adults with de novo scoliosis, the natural history is even more poorly understood. The constellation of symptoms varies greatly among patients and cannot be determined based on the size of the curve. However, with aging, the natural tendency is for progressive loss of disk height through dessication, decreased lumbar lordosis, increased sagittal imbalance, and decreased motion. This process is further complicated with coronal and sagittal changes related to osteoarthritis and osteoporosis, which lead to compression fractures and hypertrophy of the facet joints and ligamentum flavum in some patients. The combination of facet and ligamentum flavum hypertrophy, coupled with disk protrusions commonly seen anteriorly, can lead to central and lateral recess stenosis with resultant radiculopathy. However, even with these changes, some patients remain remarkably asymptomatic, whereas others with seemingly mild radiologic changes may complain of debilitating pain. Regardless of the patient’s symptoms, frank paralysis from compression and worsening alignment is rare, therefore surgical treatment of the disorder is almost never an emergency. It is thus prudent to spend adequate time on the patient’s workup to fully understand the source of the complaints, to exhaust nonoperative measures prior to pursuing surgery, and to have an extensive preoperative discussion to fully address the risks and benefits of proceeding with any sort of operative correction.

History and Physical Examination

The assessment of these patients begins with a detailed history and physical exam. Clarification of the patient’s primary complaint should be elucidated, and it should be determined whether these symptoms are worsening. Patients who come to medical attention with worsening, intractable pain or neurogenic claudication may require different intervention than someone concerned with cosmesis alone. A history of vascular claudication can mimic neurogenic claudication; however, patients with vascular claudication often have improvement of their symptoms while standing still or sitting, whereas patients with neurogenic claudication show improvement while leaning forward.

Patients with adult scoliosis can come to medical attention with multiple medical problems. A patient with a history of cardiopulmonary disease may not tolerate a prolonged operation and anesthesia, similarly, diabetes will adversely affect the cardiovascular system and wound healing, which in turn can increase the incidence of postoperative complications such as infection, deep venous thrombosis (DVT) and/or pulmonary embolism (PE), and pneumonia. Similarly, a history of smoking should be addressed, and every attempt should be made to institute a smoking cessation program at least 1 month prior to surgery that continues 6 months after surgery, because tobacco use correlates with a higher risk of pseudarthrosis and pulmonary complications, poor wound healing, slower rate of recovery, and overall poorer outcome of the procedure. A personal or family history of bleeding problems or blood clots is extremely important and may warrant a preoperative hematologic evaluation. A history of susceptibility to infection should also be obtained to determine whether the patient may be more prone to developing perioperative wound complications. Rheumatologic disorders are not uncommon in this population, and the current disease-modifying antirheumatic drugs (DMARDs) need to be altered if any surgery is being planned. Medications that inhibit coagulation, such as nonsteroidal antiinflammatory drugs (NSAIDs), acetylsalicylic acid, clopidogrel, anticoagulants, vitamin E, and fish oil should be stopped prior to surgery to decrease intraoperative bleeding and decrease the likelihood of developing postoperative wound and epidural hematomas.

Assessing patients’ social support structure is invaluable in determining their ability to tolerate the postoperative demands during recovery. Patients without an extensive family support system may not be ideal surgical candidates. Elicit any history of previous treatments, such as physical therapy and injections; although these may have been previously tried, patient compliance and the quality of the injections vary greatly, so a history of either does not automatically mean that nonoperative treatment has failed.

The physical exam begins with observation of the patient. Facial expressions are noted, because patients may occasionally grimace and appear uncomfortable while sitting, standing, or walking. Standing coronal and sagittal alignment, shoulder height, waist asymmetry, and pelvic obliquity are evaluated. Paraspinous rib and lumbar humps are evaluated with the Adam’s forward bend test. Significant loss of lumbar lordosis may present with a forward pitch of the trunk, which impairs forward gaze of the eyes, and patients compensate by flexing the hips and knees to maintain forward gaze. Asking the patient to stand sideways with straight legs further accentuates the severity of the sagittal imbalance. Observation of the gait is used to identify any limitations and signs of weakness or myelopathy. A thorough neurologic exam is necessary, including an assessment of strength, sensation, and the reflexes. Assessment of the distal pulses evaluates for evidence of vascular insufficiency, and examination of the hips and knees can assess for signs of symptomatic osteoarthritis, which can alter treatment recommendations.

Radiologic Evaluation

The radiologic evaluation begins with full-length 36-inch anteroposterior (AP) and lateral scoliosis films. The patient’s position during these films must be standardized to negate any compensatory positioning. Patients should stand with their feet together and their hips and knees fully straightened; arms should be in 30 to 45 degrees of forward flexion with elbows flexed and hands resting on the clavicles. Standardizing this positioning prevents inaccurate representation of the sagittal vertical axis.

In the AP projection, the coronal curves are measured using the Cobb technique, and the coronal alignment is measured using the C7 plumb line. Any deviation of the C7 plumb line from the central sacral vertical line (CSVL) suggests coronal imbalance. Shoulder asymmetry, waist asymmetry, pelvic obliquity, and vertebral body lateral listhesis may also be present. The appearance of an outlet view of the pelvis suggests that the patient has decreased lumbar lordosis and retroversion of the pelvis.

In the lateral view, the overall sagittal alignment is examined by drawing the C7 plumb line and then determining the distance from this line to the lateral sacral vertical line (LSVL), a vertical line drawn from the posterosuperior corner of S1. This line ideally overlaps the C7 plumb line and transects the T12–L1 disk space as well as the C7–T1 disk space.

The regional sagittal alignment of the thoracic, thoracolumbar, and lumbar spine is also measured. An oversimplified method to remember the normal sagittal alignment of these regions is the 0/30/60 rule, which states that the thoracolumbar alignment should be around 0 degrees, the thoracic kyphosis should be around 30 degrees, and the lumbar lordosis should be around 60 degrees. The pelvic incidence (PI) and pelvic tilt (PT) are also measured ( Fig. 63-1 ). The PI is an angle made by the intersection between a line drawn perpendicular to the S1 end plate at its midpoint and a line from this point to the center point of a line drawn between the centers of the femoral heads.

Pelvic parameters measured on lateral radiograph. Sacral slope (SS) is the angle from horizontal made by the superior end plate of S1. Pelvic tilt (PT) is defined as the angle formed by a line drawn vertically from the center of the femoral head and one drawn from this point to the center of the S1 end plate; PT is a measure of the relative amount of pelvic retroversion. Pelvic incidence is the angle formed by drawing a line perpendicular to the S1 end plate at its center and one from that point to the center of the femoral heads. In most cases, the femoral heads do not perfectly overlap. In that case, find the center of each femoral head, draw a line between these points, and measure to the midpoint of this line.

Schwab and Lafage discussed the importance of the relationship between PI and the ideal degree of lumbar lordosis (LL; Fig. 63-2 ). They suggested that the ideal LL can be estimated with the following formula:

Ideal measurements for various pelvic parameters.

Whereas PI remains fairly constant as pelvic retroversion increases, PT increases ( Fig. 63-3 ). PT is an angle formed by the intersection of a vertical line drawn from the center point of a line drawn between the centers of the femoral heads and the line drawn from the midpoint of the S1 end plate to the center point of the line between the centers of the femoral heads (see Figs. 63-1 and 63-2 ). Lafage and Schwab showed that with increasing PT, pain and disability increase as measured by the Oswestry Disability Index, Short-Form 12 questionnaire, and Scoliosis Research Society 22 questionnaire scores. Similarly, Schwab and colleagues showed the disability caused by adult scoliosis in general. If surgery is planned, full-length supine AP bending and supine lateral radiographs can help assess curve flexibity in the coronal and sagittal planes.

As pelvic retroversion increases to compensate for sagittal imbalance from no retroversion ( A ) to moderate retroversion ( B ) to severe retroversion ( C ), the pelvic tilt ( grey lines ) also increases; however, pelvic incidence ( red lines ) remains fairly constant regardless of compensatory retroversion.

Patients with degenerative scoliosis can come to medical attention with symptoms suggestive of spinal stenosis and radiculopathy. Other pathologies, such as tumor and infection, may also be affecting the alignment of the spine; therefore further imaging may be indicated. Magnetic resonance imaging (MRI) can be useful in assessing the degree of spinal stenosis, disk desiccation and protrusion, ligamentum flavum hypertrophy, and facet pathology, and it may help identify signs of osteomyelitis, diskitis, and neoplasm. The MRI should be performed with gadolinium in patients who have had previous surgery to help differentiate scar tissue from disk material. However, MRI can be difficult to interpret in patients with a coronal deformity greater than 40 degrees or retained metallic implants. In these cases, a CT myelogram may be more useful. Both of these studies can be used for more advanced preoperative planning, such as vascular mapping, bone quality assessment, planning of screw lengths and trajectory, and identification of levels for decompression.

Nonoperative Management

In the absence of progressive neurologic deficit, nonoperative measures should be pursued first. This treatment consists of NSAIDs, physical therapy for strengthening and stretching exercises, cardiovascular conditioning, avoidance of painful activities, corticosteroid injections, and modalities such as heat and ice for symptom relief. Bracing is poorly tolerated in the degenerative population and can lead to unnecessary expenses. Therapy should focus on strengthening the abdominal and paraspinal musculature, increasing hip and knee range of motion, and improving cardiovascular endurance. The patient must be diligent about doing exercises at least once per day 5 to 7 days per week. In addition, patients should increase their activity level and endurance, with the goal of walking a mile each day, even if it has to be broken up into several smaller sessions. Even if the patient fails to improve with nonoperative therapy, the increased activity will hopefully allow them to better tolerate the demands of postoperative therapy. Patients are also encouraged to pursue alternative measures that have helped them in the past, such as chiropractic care, acupuncture, and Eastern medicine.

Developing a professional relationship with a rehabilitation physician and pain medicine specialist will allow the surgeon to develop a thorough rehabilitation protocol for their patients. It also ensures that the patient is receiving the most effective and comprehensive nonoperative therapy program. Epidural and selective nerve root injections can provide symptomatic relief for many patients. Serum 25-hydroxy vitamin D levels are checked, and supplementation with vitamin D3 is prescribed for patients with low vitamin D3 levels. Bone mineral density studies are ordered, and appropriate treatment with bisphosphonates or teriparatide is administered whenever indicated.

In patients with neurologic symptoms, such as radiculopathy and claudication, gabapentin and pregabalin can be helpful. The use of antidepressant medications has also been described. Long-term narcotic pain medications and muscle relaxants should be prescribed by the pain management specialist.

A rigorous nonoperative protocol that has been carefully coordinated with a rehabilitation physician and pain management specialist can benefit the majority of patients. These patients usually demonstrate enough improvement that they do not pursue operative intervention. However, some patients do not benefit as much as others from nonoperative treatment, and these patients may be more appropriate surgical candidates.