Introduction

Adult scoliosis is a common and sometimes disabling degenerative condition of the spine, with an overall prevalence reported in up to 60% of the elderly population.¹ Adult scoliosis has a marked impact on patients’ general medical health and well-being; it has been shown that scoliotic patients have a significantly depressed perception of their mental and physical health in comparison with the general U.S. population. Even when individuals are compared with those having additional comorbidities, the adult scoliosis patients rate lower in clinical health assessment. In addition to the subjective considerations of this progressive disease, severe pain and disability occur in this population.²

The management of patients with symptomatic spinal deformity and spinal stenosis is controversial. The greatest challenge confronting contemporary spine surgeons in management of the aging patient population is patient selection; the surgeon must balance benefits, risks, complicatios, and the durability of various interventions. Analysis and application of these is difficult because of the limited number of prospective outcome studies and because there is a wide array of different interventions used in this patient population. The spine surgeon is increasingly confronted with the older patient and must decide on a suitable yet realistic treatment plan while considering the social and psychological factors affecting this unique patient population.

Pathoanatomic Changes

Aging of the spine is similar to the degenerative process throughout the body. The physiologic aging cascade affects the anatomic structures and creates progressive changes that are biomechanical, biochemical, and physiologic. Changing pathophysiology affects the structure and function of the spine, which becomes relatively important because of the spine’s role as the central foundation for the human upright posture.

Degenerative adult scoliosis occurs as result of both macroinstability and microinstability. There is segmental instability and translation of adjacent vertebral aligment in the lumbar spine, acquired secondary to years of chronic disc disease and progressive facet incompetence. Disc degeneration leads to disc collapse and bulging of the annulus fibrosus and posterior longitudinal ligament, thus triggering subperiosteal osteophyte formation. Additionally, articulating facets undergo degenerative changes that result in hypertrophy, calcification, and thickening of the ligamentum flavum. These changes eventually result in forward and translational displacement of the posterior elements that, in combination with degenerative disc changes, result in severe narrowing of the spinal canal and neural foramen (spinal stenosis) to cause symptoms of neurogenic claudication and radiculopathy.

Definition of Stenotic Degenerative Disease in Deformity

Lumbar spinal stenosis is defined as a narrowing of the spinal canal that produces compression of the neural elements before their exit from the neural foramen. The narrowing may be limited to a single motion segment (two adjacent vertebrae and the intervening intervertebral disc, facet joints, and supporting ligaments) or it may be more diffuse, spanning two motion segments or more.

Adult deformity of the spine with degenerative disease can be a major contributing factor in the narrowing of the spinal canal. Adult degenerative scoliosis occurs on the right and left sides with equal frequency. Adult degenerative scoliosis develops as a result of asymmetrical narrowing of the disc space and vertebral rotation secondary to the instability caused by degeneration of the disc.

Neural compression associated with adult lumbar scoliosis is commonly manifested as a radicular pain that may be related to physical activity. As the apex of a curve rotates, there is associated hypertrophy and subluxation of the facet joints in the concavity of the curve. Additionally, collapse in the concavity results in narrowing of a neural foramen between adjacent pedicles. As a result, symptoms occur in the anterior portion of the thigh and leg (resulting from compression of the cephalic and middle lumbar nerve roots). Radiating pain in the posterior portion of the lower extremity is more common on the side of the convexity of the lumbar curve; such pain is due to compression of the caudal lumbar nerve roots and the sacral nerve roots, well caudad to the apex, as the spine curves back to meet the pelvis. ²

Clinical Complex of Symptom Presentation

The degenerative aging spine with deformity creates the complex of four major categories of clinical symptom presentation:

Neurologic pain occurs with activity-related claudication caused by diminished blood flow to the nerves. It is incumbent upon the healthcare provider to rule out common causes of leg pain such as peripheral vascular disease, cardiac disease, arteriosclerotic vascular disease, and/or primary neurologic disease. Compressive radicular pain occurs on the concave collapsing side of a degenerative scoliosis, from direct compression of the nerve at the exiting foramen or subarticular space. Nerve stretch radicular pain occurs on the convex nerve roots that are exiting from the stenotic collapsing scoliotic spine. Therefore, a patient may present with either convex radicular pain or concave nerve root pain, or both.

Back pain may be caused by arthrosis and normal aging body changes of the discs, facets, or other structures. Another cause of back pain may occur from abnormal restricted segmental spine motion, as referred to by the term “mechanical pain.” Also, back pain may occur secondary to nerve root compressive pain, which is secondary to decreased circulation and/or nerve compression.

Activity-related complaints from the aging spine patient generally involve lifestyle changes. Often the patient will present to the healthcare provider with statements describing restriction of normal activities of living. The patient may state that she or he cannot participate in dance, golf, normal work, recreational activities of hunting and fishing, or normal walking and exercise.

Deformity-related issues include complaint of a cosmetic changing appearance to the body, with or without a rib producing pressure on the pelvis. The patient may be twisting and leaning more on one side relative to the other side of his or her body. Less often, the patient will describe a shortness of breath secondary to restrictive lung capacity from scoliotic collapse and degenerative changes around the chest. The final and probably the most daunting problem is when the patient presents with complaints of balance and instability that affect normal ambulation. The patient may have a spine deformity that is so significant that he or she is not able to maintain normal balance, and requires orthotic spine supports such as a cane or walker to ambulate through daily activities.

Adult Scoliosis Classification

Adult Scoliosis is classified by Aebi ³ using an AO system based on a pathoanatomic etiology and on a temporal onset of deformity. His classification defines adult scoliosis as spinal deformity in a skeletally mature patient with a Cobb angle of more than 10 degrees in the coronal plane. Aebi separates adult scoliosis into four types:

FIGURE 51-1 A 66-year-old woman with an AO type 1 de novo scoliosis curve pattern. Myelogram and intrathecal CT scan demonstrate typical pathoanatomic changes consistent with severe spinal stenosis at the L4 vertebral level. Note the facet hypertrophy, facet malalignment, ligament flavum hypertrophy, thecal sac compression, disc degeneration, and vertebral olisthesis.

FIGURE 51-2 A 66-year-old woman with an AO type 1 de novo scoliosis curve pattern. Sagittal view shows postoperative fusion from T10 to L5 with maintenance of lumbar lordosis for standing balance.

Schwab et al.⁴ proposed a three-tier classification system for adult scoliosis based on parameters of coronal and sagittal plane. These radiographic criteria include lumbar lordosis, location of coronal curve apex, olisthesis of vertebra segments relative to each other, and sagittal balance on x-ray (Figures 51-3 through 51-6). The classification system has accurately correlated radiographs with clinical significance, in an attempt at suggesting the most appropriate successful treatment in the adult patient. The rate of disease progression is influenced by the magnitude of the curve, the degree of lateral listhesis, the quality of the bone and the severity of associated spondylotic disease. Table 51-1 shows two classification schemes.

FIGURE 51-3 A 66-year-old female with symptoms of back pain and pseudo-radicular leg pain plus neurogenic claudication. She had an AO (Aebi) type 1 de novo scoliosis curve pattern, also categorized as a Schwab type 5, A+ pattern. After work-up and failure of extended nonoperative treatment, she underwent a posterior multilevel spine decompression /laminectomy and stabilization reconstruction / realignment with fusion and segmental pedicle screw implant instrumentation. Follow-up evaluation demonstrated excellent clinical improvement with resolution of symptoms and an excellent radiographic result, similar to that demonstrated in Figure 51-6.

FIGURE 51-4 A 45-year-old female with AO (Aebi) type 2 adult scoliosis curve. She met the Schwab criteria of type II, A0. Therefore, she was treated with a limited thoracic (T3-T12) posterior spine reconstruction fusion with segmental pedicle screw instrumentation; she had an excellent result with improvement of clinical pain and correction of deformity.

FIGURE 51-5 62-year-old female with AO (Aebi) type 3a adult scoliosis curve classification. This patient was also categorized as a type IV, B+ according to the Schwab criteria. She was treated with an anterior spinal release with implant interbody arthrodesis reconstruction followed by a posterior multilevel laminectomy /foraminotomy and long reconstruction / realignment fusion from T4 to sacrum using segmental pedicle screw fixation and implant stabilization. She had an excellent clinical and radiographic outcome.

FIGURE 51-6 55-year-old female with AO (Aebi) type 1 de novo adult scoliosis classified as type IV, B++ by Schwab criteria. Patient was treated with anterior and posterior spine reconstruction and realignment with implant segmental pedicle screw instrumentation from T4 to sacrum. Also, she had multilevel posterior laminectomy /foraminotomy of the lumbar spine to complete the neurologic decompression. She showed excellent clinical and radiographic outcome.

TABLE 51-1 Adult Spine Deformity Classifications

Considerations for Nonsurgical or Surgical Management

Nonoperative treatment should always be the initial form of management. However, attempts to alleviate symptoms, including physical therapy and steroid injections, oral medications, diet and protein supplements, orthotics, and active muscle training, rarely yield satisfactory long-term results because the underlying pathology remains unchanged.

Surgical management of spinal disorders in the elderly poses challenges not faced in younger patients. Poor bone quality, the possibility of extensive spinal degenerative changes, and changes in sagittal alignment with increased thoracic kyphosis and loss of lumbar lordosis all complicate surgical management. The presence of multiple coexisting medical conditions, reduced wound-healing potential, and malnutrition can markedly increase the risk of complications for extensive surgical procedures. Osteoporosis and osteopenia complicate fixation options. The option of harvesting large quantities of autogenous iliac crest bone graft is not practical in patients with poor bone stock and osteopenia. Additionally, complications of fusion procedures in the elderly may lead to adjacent segment degeneration and the development of junctional kyphosis.

Goals of Treatment (See Table 51-2)

The accepted and basic general goals of surgical management of the spine should include:

TABLE 51-2 Surgical Planning Goals

• Decompression of neurologic structures • Stabilization of spinal segmental anatomy Fusion • In situ without implant instrumentation • With implant instrumentation Sagittal balance (imperative) • Deformity correction (as indicated) Realignment/reconstruction • Minimizing complications • Maximizing: Function Quality of life

In essence, surgery for these patients should primarily address improvement of the spinal stenosis that is causing clinical and lifestyle issues. Stabilization, realignment, and/or reconstruction of the deformity is a secondary surgical consideration.

Surgical Procedures

The types of surgical procedures include:

• A decompression and stabilization procedure with arthrodesis

Rarely, an in situ procedure with bone alone, without metal implants

Typically, with metal implant instrumentation

• Realignment and reconstruction

A decompression (either direct or indirect) with implant instrumentation for stabilization and fusion

Outcomes Associated with Spinal Deformity Treated with Surgical Decompression

Frazier, Lipson, Fossel, and Catz⁵ published their report in 1997, of a series of 90 patients with preoperative scoliosis associated with back pain, who were treated surgically and followed at 6 months and 24 months after surgery. These authors show that there was an increase in olisthesis, but this fact was associated with greater improvement in walking capacity at 6 months and at 24 months after surgery. Their data indicated that minor increases in the olisthesis after surgery for spinal stenosis generally were well tolerated by the patients. These authors showed that results support that preoperative scoliosis is associated with less favorable outcomes in patients who undergo decompression alone for spinal stenosis.

Operative Treatment of Degenerative Lumbar Scoliosis Associated with Spinal Stenosis

Patients who present with symptoms of spinal stenosis and who have degenerative scoliosis less than 20 degrees and without instability may be treated with spinal decompression only. Male patients with large vertebral structures and stabilizing osteophytes can tolerate more than two-level laminectomy without fusion. Otherwise, patients with degenerative scoliosis more than 15 to 20 degrees, lateral subluxation, or dynamic instability should be treated with decompression and fusion. Simmons⁶ selects different fusion strategies according to his classification types of degenerative scoliosis; pedicle screws are considered the most appropriate fixation method for the aging osteoporotic bone with absent posterior elements after decompression. It is often imperative to extend the fusion to the sacrum with the addition of multiple fixation points in the sacrum and the pelvis to reduce increased strains to the implants and help healing of the fusion.

In referencing an article published by Poloumis, Transfeldt, and Denis,⁷ a modification of their proposed treatment algorithm for patients can be established (shown in Figure 51-7). An extensive study of their patients was made, for which treatment was determined by using their algorithm, which included statistical significant improvement outcomes measured by SF 36, Oswestry, and VAS scores postoperatively.

FIGURE 51-7 Algorithm for adult spine deformity.

(Adapted from Ploumis A, Transfeldt EE, Denis F: degenerative lumbar scoliosis associated with spinal stenosis, Spine J 7(4):428-36, 2007.)

The important consideration for surgery is whether or not the spinal segments are:

If the initial spine is stable, then a decompressive operation is indicated. The decompression alone would be sufficient unless iatrogenic instability is produced at the time of surgery. If iatrogenic instability is produced, then a selective fusion of the major curve should be performed over the area of decompression. If the spine shows instability of the segments prior to commencing surgery, then a selected fusion of the major curve with decompression should be planned and carried out. In contrast, if the preoperative analysis of the patient shows a coronal or sagittal plane imbalance, then a long fusion from the thoracolumbar area, along with decompression of the lumbar area, is planned and carried out (see Figure 51-7).

Principles for Selecting Fusion Levels in Adult Spinal Deformity with Lumbar Curves

An article by Kuklo⁸ suggested some key points for consideration of surgical levels. Kuklo stated that sagittal imbalance is poorly tolerated in the adult scoliosis patient (Figure 51-8). Surgery should leave the patient with a good sagittal alignment; preoperative workup should include evaluation of adjacent segment disease with discographic evaluation of the degenerated discs as well as pain provocative injection tests of the facet joints in determining fusion levels.

FIGURE 51-8 A 68-year-old woman treated with anterior and posterior four-level spine fusion in 2005. No pain-free interval. She developed kyphotic sagittal imbalance and T12 fracture collapse and vertebral angular instability, with inability to stand and function upright. She was treated with posterior pedicle subtraction osteotomy at T12 and sagittal realignment and extension of fusion with implant instrumentation to T5. She had excellent clinical and radiographic outcome.

Kuklo stated that a fusion should not be stopped adjacent to a degenerated segment. Additionally, he suggested that stopping long fusions at L5 would frequently lead to subsequent degeneration. Lastly, Kuklo stated that fusion to the sacrum was associated with increased complications and pseudoarthrosis at the lumbosacral junction.

Spinal Stenosis with Scoliosis

In 1992, Simmons and Simmons⁶ published in Spine their retrospective review of a series of 40 patients who had lumbar scoliosis associated with spinal stenosis and symptoms of neurogenic claudication and were treated with posterior decompression and pedicle screw fixation techniques. In follow-up at an average of 44 months, 38 patients (93%) reported mild or no pain. These workers reported no deaths and no instrumentation-related failures or pseudoarthrosis in their series.

With regard to correction and stabilization with fusion, they recommended that pedicle screw instrumentation systems offered the most advantageous method of handling the difficult problems after removal of posterior elements. Simmons and Simmons believed that long fusions incorporating the entire scoliotic curve were necessary in most patients, because a fusion from the lower portion of the thoracic spine down to the sacrum would often be required. They felt that it was important to end the fusion at a disc space that appeared level. (Table 51-3 shows the operative treatment guidelines and principles described by Simmons and Kuklo.)

TABLE 51-3 Operative Treatment Guidelines and Principles

Rate of Complications in Scoliosis Surgery

Weiss and Goodall⁹ published a report in Scoliosis in August 2008 that stated that a meta-analysis review of scoliosis surgery checking for complications revealed 2590 titled articles. Although the rates varied, scoliosis surgery had a very high rate of complications, averaging 44% for adults (range 10% to 78%) as published in 11 different studies. (Table 51-4 summarizes surgical complications in treatment of adult scoliosis.)

TABLE 51-4 Surgical Complications: Rate and Categories

Guigui and Blamoutier¹⁰ published a treatise in French in 2005 in the review of orthopedic surgery. Their review of 3311 patients during a 12-month period who underwent surgical treatment of spine deformity found that 704 patients (21.3%) had one or more complications (850 complications) during or shortly after the index operation. The categories of complications were listed as:

Older patients have an overall higher rate of complications. Ocular blindness is a serious complication that requires special note. A review by Myers and Stevens implies a relationship of blindness to operative time, blood loss, and operative hypotension, as well as an association with direct compression of the eye.

Summary

Scoliosis is a progressive disease that is associated with significant back pain and decreased bone mass in most patients. Because both problems complicate the management of the neurogenic claudication, decompression is indicated for the symptoms of spinal stenosis, along with adequate stabilization and fusion. A correction of deformity can also be attempted, but it is technically very difficult and fraught with great hazard. The aim of surgery is to decompress the compromised neural elements, in cases of symptomatic spinal stenosis, and to end with a balanced and stable spine in the coronal and sagittal plane, when there is imbalance. The idea is to proceed with the least aggressive procedure, usually posterior only, that would involve both decompression and stabilization of the spine. The important points are that fusions should not be stopped adjacent to a degenerated level and that sagittal imbalance is not tolerated by the elderly patient. The operative surgeon must make a decision as to whether the fusion should be stopped at L5, which may necessitate future surgery, or carry the fusion to the sacrum, which would in turn lead to greater risk for perioperative complications.