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Surgical Treatment of Patients With Lumbar Spinal Stenosis With Associated Scoliosis
Edward D. Simmons, MD, CM, MSc

Spinal stenosis in combination with scoliosis frequently is seen in elderly patients. Patients typically present with a combination of symptoms attributable to neurogenic claudication and radicular pain, and symptoms of lower back pain. For patients in whom conservative treatment is not sufficient, surgical treatment can be done with careful consideration of the overall patient and his or her medical status. Surgical treatment is twofold; one purpose is to decompress the neural elements, the other purpose is to stabilize and realign the spine to as great a degree as possible. Appropriate balance of the spine at the end of the procedure is more important than the absolute amount of correction obtained. Stabilization and correction of the spine is done with pedicle screw-rod instrumentation and fusion, and the procedure must be done in an efficient and timely manner to involve the least amount of morbidity. There are two types of deformity typically seen, one is a degenerative lumbar scoliosis with no or minimal rotational deformity (Type I), and the other is a degenerative scoliosis often superimposed on a preexisting scoliosis with greater rotational deformity and greater loss of lordosis (Type II). Instrumentation and correction techniques differ for these two types of deformities, with shorter instrumentation procedures usually possible for the Type I deformity and longer instrumentation with sagittal plane reconstitution necessary for Type II deformity.

Lumbar spinal stenosis is a common problem in elderly individuals and in many instances, is associated with various forms of instability, such as degenerative spondylolisthesis or lateral listhesis, and also degenerative scoliosis.^1-4'8-13 In certain instances, an underlying idiopathic scoliosis may have preexisted the onset of degenerative collapse and additional progression. The development of degenerative scoliosis superimposed on the patient with spinal stenosis compounds the problems related to the spinal stenosis, furthering the neural compression, and complicating surgical treatment if indicated. Initial treatment includes assessing the entire patient and always involves nonoperative treatment such as physical therapy, the use of a brace, and chiropractic and other forms of therapy as needed. Indications for surgical treatment include progressive neurologic deficit or severe pain that is refractory to nonoperative treatment. ^5,10 Progression of the scoliosis alone without other symptoms rarely constitutes an indication for surgery in this older age group of patients. Many of these patients have other co-morbid medical problems, and surgical treatment must be done in a safe and effective manner with the least morbidity. The surgery must be done fairly expeditiously with blood loss kept to a minimum. Very good anesthesia is required and use of cell salvage and careful fluid management is very helpful. Intraoperative somatosensory evoked potential monitoring also is helpful. The aim of the surgery is to restore the patient to a functional lifestyle with pain relief using a procedure that will involve the least amount of morbidity and low rate of complications. The absolute amount of correction of deformity in these patients is not as critical as finishing with a balanced spine in the coronal plane and with restored sagittal balance. ^12,13

With careful attention given to detail, good medical treatment and surgical technique, a very gratifying result usually can be obtained for the patient.

Typical Clinical Presentation

A typical patient is an elderly man or woman who presents with increasing problems of lower extremity radicular pain, which becomes worse when the patient stands or walks. The problem may be unilateral or bilateral and often has been progressive for numerous years. Severe neurogenic claudication to the point of marked limitation of ability to stand or walk can be seen. The patients who have associated degenerative scoliosis frequently also have major problems with mechanical lower back pain in addition to the lower extremity radicular pain. It is this author's belief that the lower extremity and the lower back pain problems must be dealt with to provide a satisfactory result for these patients. In the presence of instability such as degenerative scoliosis, a decompression alone without some form of stabilization usually will not yield a long-term satisfactory result for the patient. The ideal treatment for these patients is to perform one surgical procedure that hopefully will be the only surgical procedure that is required. It is also the author's belief and experience that a one-stage posterior decompression and instrumentation and fusion is adequate in the majority of these patients without the need for anterior procedures. The added complexity and morbidity of an anterior procedure is not necessary in most patients unless a major kyphotic deformity exists that cannot be addressed posteriorly. The surgeon always must keep in mind that he or she is treating the entire patient and not just the patient's spine. Nonspinal causes for lower back pain and lower extremity radicular pain also must be excluded carefully. These causes include claudication attributable to arterial insufficiency, viscerogenic causes of lower back pain such as abdominal aortic aneurysm, intraabdominal tumors, rectal tumors, uterine tumors, metastatic disease, and other musculoskeletal causes such as hip osteoarthritis. Many of these disease states can be present in the elderly population, and in some instances may coexist in the same patient. Certainly the coexistence of spinal stenosis in association with hip osteoarthrosis is common, and a careful evaluation of the hip must be done in the preoperative assessment. Peripheral pulses must be evaluated carefully. The typical history of vascular claudication is different than that of neurogenic claudication and must be elicited carefully from the patient. Vascular claudication almost will never arise if the patient is standing still; however, neurogenic claudication frequently will arise with the patient standing still unless the patient assumes a forward flexed posture to get relief. Patients with neurogenic claudication often report that when standing or walking, they must either sit down to get relief or at least flex forward to assume a less lordotic spinal alignment. Patients often will state that they feel relief if they can hold onto a shopping cart and this is a fairly typical "shopping cart" sign.

Examination of the spine includes overall alignment and balance in the coronal and sagittal planes. Range of motion (ROM) and areas of tenderness on palpation are assessed.

The gait pattern is assessed, and whether there is any tendency for spasticity, whether there is a broad-based gait with instability, and whether there is any Trendelenburg lurch or antalgic component also is observed. Any asymmetry of the lower extremities is observed, such as may be present with specific muscle wasting and thigh and calf circumference measurements can be taken. The results of the neurologic evaluation typically are normal in many of these patients because the symptoms arise only with walking or prolonged standing. The stationary bicycle test can be used to differentiate between vascular and neurogenic claudication. When the patient sits on a bicycle, the lumbar spine is in flexion and patients with spinal stenosis will tolerate the position well without symptoms while pedaling; however, the patient with vascular claudication will become symptomatic while pedaling.

Pathogenesis

The pathogenesis of spinal stenosis with decreased volume available for the neural elements has been described in the literature.^{1, 2, 4} There is increasing ischemia of the nerve roots, which is compounded when the patient is in the lordotic position because the neuroforamina and lateral recess canal volume is decreased when the spine is in lordosis. This is seen well on imaging studies such as myelogram with interruption of normal cerebrospinal fluid flow. Evaluation can also be done with a magnetic resonance imaging-myelogram study that does not involve any injection or contrast dye but does provide a very good evaluation similar to a standard myelogram, outlining the flow of cerebrospinal fluid and where it is impeded. (Simmons EH, Craven TG, Markowitz HD, Simmons ED: MRI myelography: Its place in spinal surgery. Presented to the 23rd annual meeting of the International Society for the Study of the Lumbar Spine, Burlington, VT, June 25-29, 1996.) In patients with degenerative scoliosis with spinal stenosis, there is additional aggravation of the underlying spinal stenosis attributable to the degenerative scoliosis. Asymmetric collapse, rotation and frequently associated rotatory and lateral listhesis, and spondylolisthesis or retrolisthesis problems that are present within the degenerative scoliotic curve all compromise the neural elements additionally. Neural impingement can occur centrally, and in the lateral recess and foramina. Facet joint hypertrophy and pedicular kinking caused by collapse of disc space height frequently are present. Decompression of the involved stenotic levels is necessary for treatment of the symptoms of neurogenic claudication and stabilization of the spine. Instrumentation and fusion and correction of the deformity to as great a degree as possible also is required. Pedicle screw instrumentation is necessary in the surgical treatment. There are no posterior elements available after decompression for insertion of hooks, and pedicle screws have the best biomechanical advantage, acting through the three columns of the spine and also providing the best fixation in the bony substrate. These elderly patients often have osteopenia and pedicle screw fixation offers the best fixation point.

Operative Procedure

Most patients who present with degenerative scoliosis and spinal stenosis have significant problems of lower back pain in addition to lower extremity pain. Decompression and stabilization is important in these patients. Correction of the deformity also is done to as maximal a degree as possible. In the decompression, care needs to be taken because the dura often is thinned and atrophic and can tear easily. The dura also can be adherent to overlying bone and careful dural dissection from the bone is necessary. Dural tears can occur during the decompression portion of the surgery. Careful inspection is done using dural dissectors and seekers. Any tear in the dura should be repaired primarily. In difficult areas a fibrin sealant such as Haemacure (Hemaseel) also can be used. Occasionally, disc herniation also is present; however, this is rare in this elderly age group. Fusion without instrumentation can be done; however, the overall fusion rate will be less and correction of deformity cannot be performed.^3,6,12,13

Another important factor to consider is that inherent in decompression of the spine additional destabilization is created.^3,6 Patients with potentially unstable situations such as degenerative scoliosis or spondylolisthesis often will have additional problems and progression of deformity if decompression is clone without some form of stabilization. After the decompression, the instrumentation not only allows for correction of the deformity and stabilization of the spine, but also allows for the chance for additional indirect decompression of the spine through realignment either through a rotational maneuver or through some distraction on the concavity of the curve.

Pedicle screw fixation is necessary because the posterior elements have been removed and also is advantageous because the pedicles are the strongest fixation particularly in these patients who often have osteopenia. The pedicle screw acts anteriorly to the axis of rotation and allows for more correction of coronal and sagittal malalignment than is possible with any other type of fixation. During the procedure standard anteroposterior (AP) and lateral radiographs can be taken to confirm location of pedicle screws and the anatomic techniques and tactile sensation of the pedicle walls must be ascertained carefully when inserting the fixation. Additional confirmation with electromyographic monitoring also can be done.

Techniques for Correction of Deformity

There are two general techniques for correction of deformity and degenerative scoliosis. One is a technique used for patients with short degenerative collapsing curves with reasonably well-maintained lumbar lordosis or minimal loss of lordosis. This involves some distraction on the concave side with the rod carefully contoured to maintain lordosis and a neutralization rod on the convex side (Figs 1, 2). The other technique is a rod derotation maneuver as used for patients with idiopathic curves. This technique is useful for patients with longer degenerative curves and for patients with curves with more significant loss of lumbar lordosis. In these patients, the derotation maneuver will convert the scoliotic curve in the coronal plane into a lordotic curve in the sagittal plane (Figs 3, 4). The overriding principal for both of these techniques is to end up with a spine that is balanced above the sacrum with the areas that have been decompressed well stabilized within the instrumented segments. Another important principle is to avoid ending the instrumentation at an area of junctional kyphosis or at a level of a retrospondylolisthesis or spondylolisthesis. The two types of degenerative lumbar scoliosis are shown in Table 1. In the Type I short degenerative curve, the superior endplate of the most cephalad vertebral body should be made as horizontal as possible to maintain spinal balance. Factors to consider in the choice of end vertebra include evidence of any rotatory or lateral subluxation and the curves in the thoracic spine above the lumbar region that may affect overall spinal balance and as mentioned above, the instrumentation should not be stopped at an area of kyphosis. It also should be recognized that in many elderly people there are concomitant hip flexion contractures and, if the instrumentation and fusion procedure results in any loss of lumbar lordosis, these patients will have a difficult time compensating. They will tend to stand with a forward flexed posture, which will result in fatigability and ongoing problems with pain.

DISCUSSION

Patients with degenerative scoliosis and spinal stenosis are an interesting subgroup of patients. Degenerative scoliosis and spinal stenosis are seen in a predominantly elderly population, and are becoming more prevalent. The surgical treatment of these patients can be challenging and very rewarding. Certain principles should be followed to attain a high success rate in treatment of these patients. Overall attention to the patient's well being must be maintained at all times and a surgeon must not forget that he or she is treating the patient and not just the spine. If the patient's physiology will not withstand large anterior and posterior combined procedures, then these should not be attempted. In most instances, a one-stage posterior procedure can accomplish the major goals of pain relief and correction of spinal balance to improve the patient's quality of life and functional status.⁷ The author has found it rarely indicated to perform anterior and posterior combined procedures in these elderly patients. Exceptions to this would include instances where a fixed kyphosis exists, which is not passively correctable to a satisfactory degree to attain proper sagittal balance through a posterior approach. Preoperative evaluation with extension films over a bolster can be obtained to evaluate this. Extension osteotomies also can be used in these patients to obtain an increased amount of lordosis. With adequate removal of the posterior structures, reasonable reconstitution of lordosis can be done with an extension osteotomy. Posterior lumbar interbody fusion also can be used in combination with the posterolateral instrumentation and fusion in certain patients who may be at high risk for pseudarthrosis such as in patients with long fusions to the sacrum. Autograft is the primary source of bone graft; however, this can be augmented with cancellous allograft or other bone graft substitutes as necessary. The autogenous local bone removed from the decompression also is a useful source of bone graft.

There are essentially two means of correcting deformity in patients with degenerative scoliosis. In patients with a short degenerative curve, usually in the lower lumbar spine and lumbosacral junction, a short construct can be done with some distraction on the concavity of the scoliosis.¹³ This is done to balance the spine and have the superior endplate of the most cranial instrumented vertebra parallel to the floor (Fig 2). A second type of curve is a longer degenerative scoliosis or one superimposed on a preexisting idiopathic scoliosis. These patients often have rotational malalignment and greater loss of lordosis. The means of correction in these patients involves a longer instrumentation and often a derotation maneuver can be done to increase the lordosis in a physiologic fashion12 (Figs 4, 5).

In patients with spinal stenosis associated with degenerative scoliosis, it is important to address the two major aspects of the spine, that is, the neural elements, and the stability and alignment of the vertebral column. Neglect of either of these two components will lead to inadequate results and less than ideal clinical outcomes. Although the correction of the deformity does lead to a certain degree of indirect decompression, this alone usually is not adequate in these patients unless the spinal stenosis is of a very mild degree. Most patients have a more serious level of spinal stenosis with major symptoms of neurogenic claudication. Wide posterior decompression and formal lateral recess decompressions and foraminotomies usually are necessary. After the decompression, attention should be given to the second stage of the procedure, namely the instrumentation and correction of the deformity, and the bilateral posterolateral fusions (Table 2). Careful attention given to detail in preparing the fusion bed also is important because ultimately the instrumentation will not hold if a successful fusion is not attained.

As has been discussed, pedicle screw and rod instrumentation is the preferred method of stabilization and reconstruction of the spine. There are many current systems available that will suffice, all of which allow for a segmental fixation and cross-linking of rod constructs.

With careful management of blood loss and fluid, the surgery usually can be done safely. However, the least aggressive procedure for the maximal amount of gain is preferred. The main goal for these patients is to provide pain relief and improved functional lifestyle. Although some correction of deformity obviously is desirable, this is not the overriding concern for the majority of these patients. Intraoperative spinal cord monitoring and cell-saver blood salvage are used. Postoperatively, the patients are treated with a thoracolumbosacral orthosis or lumbosacral orthosis. They are seen by physical therapists and occupational therapists and usually are ready to be discharged to home or a subacute rehabilitation facility by the fifth postoperative day.

References

1. Dick W, Widmer H: Degenerative lumbar scoliosis and spinal stenosis. Orthopade 22:232-242, 1993.

2. Fellrath Jr RF, Hanley Jr EN: Causes and management of unstable degenerative spinal stenosis. J South Orthop Assoc 5:221-228,1996.

3. Frazier D, Lipson S, Fosse] A, et al: Associations between spinal deformity and outcomes after decompression for spinal stenosis. Spine 22:2025-2029, 1997.

4. Garfin S, Herkowitz H, Mirkovic S: Spinal stenosis. Bone Joint Surg 82A:572-586, 2000.

5. Gelalis ID, Dawson E, Bernbeck .1: The surgical treatment of low back pain. Phys Med Rehabil Clin North Am 9:489-495, 1998.

6. Katz JN, Lipson SJ, Lew RA: Lumbar laminectomy alone or with instrumented or noninstrumented arthrodesis in degenerative lumbar spinal stenosis:

Patient selection, costs, and surgical outcomes. Spine 22:1123-1131, 1997.

7. Liew S, Simmons ED: Thoracic and lumbar deformity. Orthop Clin North Am 29:843-858, 1998.

8. Markwalder TM: Surgical management of neurogenie claudication in 100 patients with lumbar spinal stenosis due to degenerative spondylolisthesis. Acta Neurochir Wien 120:136-142, 1993.

9. Nasca RJ: Surgical management of lumbar spinal stenosis. Spine 12:809-816,1987.

10. Nasca RJ: Rationale for spinal fusion in lumbar spinal stenosis. Spine 14:451-454,1989.

11. Postacchini F: Surgical management of lumbar spinal stenosis. Spine 24:1043-1047,1999.

12. Simmons ED: Surgical management of complicated spinal stenosis associated with degenerative scoliosis. Oper Tech Orthop 7:48-59, 1997.

13. Simmons ED, Simmons EH: Spinal stenosis with scoliosis. Spine 17:S117–S120,1992.

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