Introduction

Scoliosis — defined as a curvature of the spine in the coronal plane measuring over 10 degrees — can be found in the adult population and can be a significant source of disability, especially in the elderly.^1,2 There are three principal forms of scoliotic spinal deformity that can be described: idiopathic, i.e., that whose development can be found during the juvenile or adolescent growing years of life and which persists into adulthood; de novo, which involves the development of a new scoliosis later in life as a result of degenerative changes in the lumbar spine; and osteoporotic scoliosis, a less common form of spine curvature secondary to osteopenic collapse of vertebral bodies.

In the adolescent with scoliosis, the primary focus of treatment is the deformity and concerns of curve progression. In the older patient, it is much more common that pain is the primary complaint.^3,4 In the later decades of life, curve progression becomes less and less of a concern, primarily because of the restraint provided by the degenerating and ossifying disc spaces and the arthritic facet joints. Being out of balance, especially in the sagittal plane, adds an element of posturally related fatiguing pain that limits patients’ ability to perform upright activities.⁵ Older adults are most commonly symptomatic in the lower thoracolumbar or lumbar region, due to the age-related disc degeneration and osteoarthritis associated with the deformity.

Patient Evaluation

Clinically, the evaluation of the elderly patient with scoliosis begins with an appreciation of the overall coronal and sagittal balance. There are many reasons other than spinal deformity for the patient to have difficulty standing upright: hip and knee degeneration, spinal stenosis, lumbosacral or thoracolumbar kyphosis, trunk muscle weakness, or flatback pathology. The last entity — flatback syndrome — typically due to some form of loss of the normal lumbar lordosis, can result in a loss of trunk strength and difficulty fully extending the hips. All patients should thus have a careful examination of the hip range of motion, including assessment of their ability to extend completely when in the supine examining position. Hips that have become locked into contracture may well require some form of release before considering any corrective surgery on the spine. On occasion, degenerative arthritis of the hips can be treated with arthroplasty first before proceeding with spinal surgery.

Routine radiographs are obtained in the upright position and should include standing, full-length, anterior-posterior, and lateral films to assess not only the dimensions of the curve, but the overall alignment in both the coronal and sagittal planes. It is important to obtain the images with the patient’s hips and knees as extended as possible in order to appreciate the true sagittal profile. In addition, side-bending or hyperextension lateral films are quite helpful in determining the flexibility of the curve, and, if considering surgery, whether some form of anterior release or posterior osteotomy is necessary.

Because the majority of patients present with pain, magnetic resonance imaging is often obtained. MRI can assess the quality of the distal intervertebral discs, and as many patients will complain of varying degrees of leg pain from stenosis, axial MRI imaging is useful to study the spinal canal and foramen and determine levels of decompression if necessary. MRI can also be used to study the most caudal intervertebral discs of the spine, as a fusion may on occasion stop short of the sacrum if distal painful pathology does not appear to exist, although this is somewhat less common in the elderly compared with younger patients. MRI is also very helpful in ruling out malignancies or infections.

Computerized tomography is helpful during the planning stages for studying the bony anatomy; in the setting of previous fusions, the quality and extent of the previous arthrodesis can be best obtained with CT imaging. CT is also quite helpful in analyzing the size of the pedicles, the width of the ilium, and the morphology of the vertebrae themselves.

Treatment

Elderly patients with painful scoliosis can be considered candidates for nonoperative treatment modalities, just as their younger counterparts are. As the majority of the patients present with symptomatic curves in the lumbar or thoracolumbar region, simple education and an understanding that the curvature does not present an immediate threat to their cardiac or pulmonary systems (as did primary thoracic curves left untreated) may be reassuring enough to many. Combinations of the judicious use of nonsteroidal antiinflammatory medications, activity modifications, and physical therapy are often helpful. Physical therapy will tend to be more successful when it is low-impact and focused on aerobic conditioning rather than vigorous activity. Water-based conditioning is also quite helpful in many. Use of orthotics is not typically well tolerated by the elderly, but an occasional patient may find the use of a brace supportive and helpful in his or her daily activities.

Surgery

Patients are considered candidates for surgical intervention if their symptoms have remained significant despite attempts at nonoperative care or, less commonly, if there is problematic curve progression.

Elderly patients undergoing surgery for scoliosis face the prospect of increased morbidity and mortality compared with their younger counterparts, primarily because they enter into the surgery much more disabled and with worse health status.^6–8 In the preoperative assessment, careful attention should be paid to their cardiac and pulmonary systems, as many patients have become quite sedentary and the stress of surgery may thus become problematic. If patients smoke, they should be encouraged to quit at least a number of weeks before the operation, not only to improve the chances of bone healing but to lessen the likelihood of pulmonary and wound complications, which are already elevated in the elderly population. If there is a suspicion of respiratory compromise, a history of smoking, or planned procedures about the diaphragm, preoperative pulmonary function should be assessed.

Similarly, if elderly patients have a history of cardiac or ischemic disease, they should undergo preoperative stress testing and formal cardiac evaluation. It is recommended that the elderly who have concomitant diagnoses of either hypertension, hypercholesterolemia, or diabetes be considered for perioperative beta-blockers.⁹

Elderly patients may have become relatively malnourished and the associated risks of sepsis, wound breakdown, etc., are well established.⁹ Total parenteral nutrition should be considered in staged surgical treatments, as it has been shown to diminish the rate of nutritional depletion and postoperative infections.

Surgical Techniques

A multitude of issues need to be assessed in each elderly surgical patient, including sagittal balance, coronal alignment, any complicating spinal or nerve root stenosis, disc degeneration, listhesis either anterior or lateral, osteoporosis, and any complicating medical comorbidities.

Unlike in the adolescent, where maximal safe correction of the coronal plane curvature is sought, in the elderly, aside from obtaining a solid arthrodesis, much more critical than Cobb angle correction is the obtaining and maintenance of appropriate balance in both the coronal and sagittal planes. A stable and balanced spine is the principal goal of deformity surgery in the elderly, and this often involves accepting less curvature correction. Numerous studies have emphasized that the component of postoperative radiography most closely tied to overall clinical success is the achievement of adequate balance, especially in the sagittal plane. Glassman and other members of the Spine Deformity Study Group, in a review of nearly 300 patients, have suggested that restoration of the normal sagittal balance is the most critical goal for any reconstructive spine surgery.⁵ A plumbline dropped from C7 should fall in the middle of the sacrum in the coronal plane and within the disc space of the lumbosacral articulation in the lateral view. Older adults have typically developed pronounced disc degeneration and narrowing, which leads to a loss of the normal lumbar lordosis and a forward drift of the sagittal plumbline. Osteopenic compression-type fractures can worsen the sagittal alignment, as can any thoracolumbar kyphosis.¹⁰ For these reasons, fusions of primarily lumbar pathology may well need to be extended proximally into the upper thoracic spine.

With the increased use of pedicle-screw fixation and advancing techniques such as vertebral resections, the majority of surgery in the elderly is performed through the posterior approach.¹¹ This would even include access to the anterior column, e.g., the intervertebral discs via posterior or transforaminal lumbar interbody fusion (PLIF or TLIF, respectively). Interbody support at the lumbosacral junction within at least the lower two spaces, L4-5 and L5-S1, is biomechanically mandatory for successful fusion rates.^12–14 Support here lessens the strain seen on the posterior instrumentation and protects to a certain degree against pull-out failure. As a general rule, but especially in the elderly, instrumentation should be used to maintain correction, not obtain correction.

In the case of previous decompressive surgery, scarring within the spinal canal may, however, make these PLIF and TLIF approaches somewhat more difficult. Direct anterior access to the lumbosacral junction can be successfully accomplished via a midline or paramedian incision, retraction of the peritoneal contents, and direct visualization via the retroperitoneum of the disc spaces from L3 to the sacrum with little morbidity and low risk of complications. Through this approach, more extensive removal of disc material and direct placement of femoral rings or specialized cages packed with bone fusion material can be realized.

Osteotomies have become increasingly popular and have become a part of the armamentarium of most adult deformity spine surgeons for effecting corrective change in the sagittal balance. Especially in the elderly, they have become vehicles for avoiding the time and morbidity of separate anterior approaches. Smith-Peterson osteotomy, a V-shaped resection of the posterior arch through the facets bilaterally, can effect moderate corrections per level; however, if multiple resections are combined, the overall effect on sagittal balance can be significant. The success for Smith-Peterson osteotomy, however, depends on the integrity of the anterior intervertebral disc, which must retain a certain degree of flexibility, as the correction hinges posteriorly. In other words, a disc space that is severely narrowed or even ankylosed, as can be seen in many older individuals, may not have enough residual motion and the ability to correct may be lost.

Pedicle subtraction osteotomies (PSOs) are very powerful tools for obtaining sagittal plane correction at single levels — up to 35 or more degrees per level. However, as the procedure involves a wedge-shaped resection of the laminae, the pedicles, and the posterior vertebral body itself, the blood loss can be significant, and may not be well tolerated by the aged patient . PSOs are also most efficient when performed in a previously fused spine, especially anteriorly, as the hinge is at the anterior vertebral body wall. It may be difficult to obtain the same degree of correction in spines without previous fusions. Also, as the success of maintaining the correction depends on a rigid anterior aspect of the vertebral body, significant osteoporosis, as seen in many elderly patients, can be a potential contraindication, for if the remaining vertebral body is not sufficiently strong, the bone may collapse, lessening the degree of correction.

Adequate fixation of the thoracolumbar spine with surgical implants can be problematic in the elderly patient for a number of reasons. Obviously, the quality of the bone of the spine is less than that in a younger age group, and the spine itself is typically much stiffer. In addition, many patients have had prior surgery including fusions and decompressions, which can obscure the typical landmarks for fixation and actually limit the number of possibilities for obtaining purchase, especially in the setting of previous decompressions. Use of fluoroscopy can aid in finding the pedicles, especially in the thoracic spine.

Pedicle screws have become the primary method of fixation in deformity surgery, including the elderly, although their bone quality still remains a concern. Pull-out strength of pedicle screws in patients with normal bone density is typically about 1400 N; however, in patients with osteoporosis, the strength can be as low as 200 N.¹⁵ Fixation strength of pedicle screws has been correlated with insertional torque. Hence, it is recommended that, in order to obtain some purchase with the inner cortical wall of the osteopenic pedicle, the largest-sized screw that can comfortably be placed be chosen. This is another reason for careful assessment of preoperative computed tomography with measurement of the inner diameters of the pedicles. In settings of reduced purchase quality, many surgeons treating the elderly may reinforce pedicle screws with adjacent laminar hooks or sublaminar wires. Of note, in the elderly spine, compared with younger adolescent patients treated for scoliosis, the transverse processes are typically quite brittle, and, with few exceptions, are not commonly recommended as points of principal fixation for instrumentation such as hooks.

In some setting of robust previous fusions, however, especially when extending down the ilium or sacrum, hooks can still be used when pedicle screws are not possible or practical. Hook site placement can be performed with small power burrs into the fusion mass — typically in multiple claw formations — and connected to the rods extending down to the more distal spine.

Fixation into the sacrum is a particular problem as the quality of the bone is probably the poorest here, and the risk of fusion failure (pseudarthrosis) may be one of the highest.^16,17 This is another reason why combined anterior and posterior surgery is recommended for long fusions down to the sacrum or the ilium: at a minimum, L4-5 and L5-S1 require strong structural support. In addition, because of the risk of osteopenic fracture of the sacrum when long fusions extend distally, supplemental iliac fixation is highly recommended (Figure 53-1).¹⁸

FIGURE 53-1 A 73-year-old woman with painful scoliosis, osteoporosis, and both coronal and sagittal imbalance. A, B, Preoperative anterior-posterior and lateral radiographs. C, D, Postoperative radiographs showing restoration of normal sagittal and coronal alignment. C, Anterior-posterior view shows bilateral fixation to support distal fixation. D, Lateral radiographs show normal lumbar lordosis. Interbody structural fusions can be seen at the lower two levels

Screws fixed into the sacrum can be directed down the S1 pedicle to the anterior cortex or the sacral promontory where the bone is most dense. Alternatively, they can be directed 30 degrees laterally out into the thickest part of the sacral ala. Either way, it is important to try to perforate and actually gain purchase into the anterior cortex with the screw threads, which will increase the holding power of the screw significantly.¹⁹ Cancellous screws are preferred over cortical ones as the strength of purchase correlates directly with the amount of bone found between the screw threads.

Osteoporosis and Scoliosis

There exists a known association between scoliosis and osteoporosis.^20,21 Two studies of osteoporotic women have described an incidence of scoliosis between 35% and 45%.^9,22,23 The majority of these curves will progress somewhat because of a combination of disc degeneration and facet overloading as well as compression of the osteopenic bones within the apices of the curves.^20,22

It is important to have an appreciation for the quality of the elderly patient’s bone before planning deformity correction that involves the implantation of instrumentation; it is difficult to accurately quantify the degree of osteopenia with plain radiographs before significant quantities of bone are lost.²⁴ Accurate assessment of bone mineral content includes quantitative computerd tomography (QCT), dual-photon absorptiometry (DPA), or dual-energy radiography (DXA).

Multiple surgical techniques have been suggested to improve fixation strength in the elderly osteopenic spine including supplemental sublaminar wiring, increasing fixation points, cement augmentation of pedicle screws, cement kyphoplasty of adjacent uninstrumented vertebrae, hydroxyapatite-coated screws, and expandable screws. Instrumentation-related complications still remain a principal concern in the elderly, however. In a review of 47 deformity procedures in 38 patients over the age of 65, DeWald and Stanley²⁰ reported a 13% early and 11% late instrumentation-related complication rate. Early complications included compression fractures of the most cephalic instrumented vertebrae as well as the superior adjacent body, and fractures of the pedicle. Late complications included loose or painful pedicle or iliac screws. Ten of 38 patients (26%) developed junctional kyphosis at the superior end of the construct, including late compression fractures.

Complications

Elderly patients who undergo surgery for spinal deformity are at a much greater risk for complications than adolescents and even younger adults.^18,25,26 A wide range of complication rates have been reported, from 30% to 80%.

The risk of pseudarthrosis has been detailed above; it is mildly elevated from that of younger age groups, largely due to issues with fixation adequacy. Vascular injury can take place during anterior exposures of the thoracolumbar spine; however, again, A specific age-related difference has not been shown. What has been shown to be statistically age-related is the development of nutritional depletion perioperatively and hence an increased risk for infection following major reconstructive spine surgery. Patients at risk should be screened preoperatively with serum albumin and prealbumin values and supplemented as necessary before embarking on a surgical course. For patients undergoing staged procedures, again, at-risk patients should be considered for nutritional supplementation between and after the two stages, either with total parenteral nutrition, or the more frequently recommended gastric tube feedings.

Another complication of correction of sagittal imbalance or kyphotic deformities is the development of junctional kyphosis just proximal to the cephalic ends of the instrumentation. This is a known problem with overcorrection of kyphotic thoracic spines, even in the younger age groups, but it can be especially worrisome in the elderly with long instrumented fusions and correction of sagittal imbalance. Overcorrection of kyphosis or dramatic improvement of a longstanding sagittal malalignment can impart a large kyphosing force to the adjacent uninstrumented proximal levels — as the spine attempts to return to its longstanding alignment — with the development of a painful angulation, instrumentation failure, or vertebral fracture. Care in contouring the proximal instrumentation and sparing the adjacent level ligaments and facet joints can also reduce the incidence of this complication.

Outcomes

Because of improved medical screening, advanced surgical techniques, and specialized anesthesia training, patient-related outcomes following extensive reconstructive surgery for scoliosis in the elderly have dramatically improved from a generation ago. Li et al, ² using SRS-22, SF-12, and ODI instruments, reported that adults over the age of 65 treated operatively had significantly less pain; better health-related quality of life, self-image, and mental health; and were overall more satisfied than age-related counterparts treated nonoperatively or simply observed. In fact, compared with younger age groups undergoing similar surgeries, it is the elderly who typically report similar, and in many cases, statistically superior improvements in pain and function, often because of extensive preoperative disability.^3,7, ⁸ Radiographically, however, despite such significant functional and pain-related improvements, maintaining correction remains challenging in an age-dependent manner.