The determination of fusion levels for degenerative adult scoliosis requires a detailed evaluation of the spinal deformity and an analysis of the degenerative changes of the entire spinal pelvic axis.
Choosing the upper instrumented vertebra (UIV) should be based on factors thought to be important to the overall survival of spinal segments adjacent to a spinal fusion.
These factors include: starting with healthy adjacent segments with no degeneration or instability in any plane; stopping adjacent to spinal segments with normal sagittal, coronal, and axial alignment. Additionally, extending instrumentation to T10 or proximal may provide relative protection to the adjacent segment via increased stability afforded by the rib cage.
From a clinical perspective, the postoperative sagittal balance appears to be the most critical factor in the patient's clinical outcome. Long-term follow-up of large, well-matched adult deformity cohorts will be required to determine the impact that each of these factors has on adjacent segment survival.
Case Presentation: Harry Shufflebarger, MD
The patient is a 60-year-old woman who previously led an active life. She enjoyed extensive travel, snow skiing, gardening, and many other activities. She has two children. For the past 2 years, she has noted a change in body shape, increasing lumbar pain, and inability to perform activities of daily living. She most recently developed bilateral posterior thigh pain with activity, occasionally extending to the left foot. Walking is now limited to 1 to 2 blocks, compared to 1 mile 6 months ago.
The patient's symptoms have been refractory to nonsteroidal anti-inflammatory drugs, epidurals, facet blocks, and rest. She does not want to change her lifestyle.
Past medical history is generally unremarkable. She has elevated serum cholesterol, well controlled on medication. There is no history of diabetes, cardiac problems, or other significant medical conditions. She does not smoke.
Her father died at 87 of Alzheimer's disease. Her mother is alive and generally well at 83 years. There is a male sibling who is alive and well at age 62.
Height is 162 cm and weight is 53 kg. On standing, there is mild waist asymmetry and on forward bending there is a right lumbar rotational prominence. Neurologic examination reveals no motor, sensory, or reflex asymmetry. General physical examination reveals no abnormalities.
Her diagnostic evaluation includes standing 36 in. anteroposterior and lateral scoliosis radiographs (Figure 1a), which reveal a 35° left L2–L4 degenerative scoliosis. Small proximal right thoracolumbar curve and right lumbosacral fractional curves with minimal rotation are appreciated. There is a lateral listhesis of L4 on L5. The center sacral line bisects T12, which is the proximal neutral vertebra as well. Coronal plane balance is normal. Standing lateral radiograph (Figure 1b, c) reveals multilevel lumbar disc degeneration extending from L2–L3–L5–S1, with significant loss of segmental lordosis from T12 to L4. Total lumbar lordosis (T12–S1) is decreased to 35°. This patient has normal global sagittal balance thanks in part to thoracic hypokyphosis. Bending radiographs (Figure 2) reveal a stiff primary lumbar curve and flexible secondary thoracolumbar and lumbosacral curves. Neurodiagnostic evaluation consists of MRI of the thoracolumbar spine and reveals advanced disc degeneration from L1–L2–L4–L5, and lateral recess and foraminal stenosis at L3–L4 and L4–L5.
Based on this clinical information, I have asked each debate participant to support stopping at the UIV assigned to them. Dr. Suk was assigned the UIV T10, and Dr. Mardjetko was assigned L1.
Debate: Se-Il Suk, MD
This is a review of the literature and my own personal experience regarding the impact of the proximal extent of fusion on the outcome of the surgical treatment of degenerative lumbar deformity. My goal was to summarize the clinical problems and factors to be considered when selecting the UIV in a patient with degenerative lumbar deformity, identify proximal junctional problems, and evaluate results based on the choice of the UIV. Proximal junctional problems, consisting of proximal adjacent segment degeneration, compression fracture proximal to the UIV, or screw failure in the UIV, occurred more frequently with fusions ending at T11 to L2 as compared with those ending at T10 or above.
Adult degenerative scoliosis is mainly observed in the lumbar spine and typically occurs in patients older than 60 years of age. Because of the increasing average life expectancy, coupled with more active senior lifestyles, degenerative lumbar deformity has become a common and disabling spinal condition.1,2
The literature offers the surgeon little guidance regarding the management of degenerative lumbar deformity. The prevalence of adult lumbar scoliosis had been reported to range from 2.5% to 15%.1,3 In our experience,2 the prevalence was 4.4% in adults in the fifth decade and 8.6% in those over 60 years of age, with a rapid increase after the sixth decade.
Most degenerative lumbar deformities develop as a consequence of long-standing spondylotic disease.4–7 Although the details of the pathophysiology are still unknown, scoliosis, kyphosis, or a combination of these deformities originates from a rapid asymmetrical degeneration of lumbar intervertebral discs, facet joint degeneration, and osteoporosis.8,9 Typical radiographic findings of degenerative lumbar scoliosis are loss of lordosis, asymmetric disc narrowing, spondylosis, facet joint arthrosis, laminar hypertrophy, and marginal osteophyte formation. Degenerative lumbar scoliosis is usually characterized by a short reciprocating curve extending from T11 or T12 to L5 or S1. Usually, there is not significant scoliosis affecting the thoracic spine. Degenerative lumbar kyphosis may occur as the prominent deformity and has similar radiographic characteristics.
In contrast to the asymptomatic adolescent with scoliosis, patients with degenerative deformity4 frequently present with mechanical low back pain, radicular pain, and/or severe neurogenic claudication that result in a limitation in their ability to stand or walk. A forward leaning posture may have its origin in muscle fatigue related to the coronal and sagittal plane imbalance or may be related to coexisting spinal stenosis.1,10 Back pain is more common in patients with lumbar curves who have facet arthropathy and/or degenerative discs.11
Patients with degenerative lumbar deformity often experience symptoms associated with central, lateral recess, or foraminal spinal stenosis. This may be associated with facet joint arthrosis, translational, lateral, or rotatory subluxations. Radiculopathy can occur secondary to compression of the nerve roots in the concavity of the curve or by traction on the nerve roots in the convexity of the curve. Paresis or paraplegia from untreated scoliosis in the absence of true kyphosis has not been reported.12 The psychologic burden of this disorder on these otherwise productive and healthy individuals is significant and should be considered when formulating the treatment plan.
Many patients with degenerative lumbar scoliosis do not need surgical treatment, and their low back pain can be managed by conservative measures.13 However, there is a well-defined group of patients who present with severe intractable low back pain, spinal stenosis with radiculopathy or neurogenic claudication, and progressive spinal deformity in the coronal and sagittal plane. Surgical treatment may be indicated for these patients who do not respond to conservative treatment. Surgical treatment should consist of neural decompression, correction of sagittal and coronal plane deformity, and spinal stabilization via instrumented spinal fusion.5,14
The choice of fixation is extremely important since osteoporosis is commonly identified in patients with degenerative spinal deformity.12 Pedicle screw fixation is the only real option when the posterior elements are removed to decompress spinal stenosis. We have found that the pedicles are strong fixation points in patients who have osteoporosis. Lumbar pedicle screws are superior to hooks in achieving and maintaining lumbar curve correction. Pedicle screws also provide greater correction of compensatory curves above and below the instrumented levels. The pedicle screw acts anterior to the axis of rotation and allows for more correction of coronal and sagittal malalignment compared with any other type of fixation.15
In most instances, a one-stage posterior procedure can accomplish the primary surgical goals of stabilization, decompression, and a balanced correction to improve the patient's quality of life and functional status. This can be usually be achieved by decancellation procedures or osteotomies via a posterior procedure, thus avoiding an anterior procedure with its longer operative time, increased intraoperative blood loss, and negative effect on pulmonary function.16–18
Anteroposterior procedures may be considered in patients with fixed lumbar deformity, which is not passively correctable to a satisfactory degree.
Surgery for degenerative deformity is often associated with high rates of complications. These include pseudarthrosis, instrumentation failure, junctional problems, and higher general medical morbidity. The major concerns in long fusions for degenerative lumbar deformities have been focused on the distal fusion level at L5 or S1 and distal instrumentation failure, but there are few written reports about proximal extent of fusion and its outcomes in degenerative lumbar deformity correction.
Factors to be Considered in Selecting the UIV.
Most patients with degenerative lumbar deformity have spinal stenosis at several levels, causing neurogenic claudication and/or radiculopathy. The extent of the pathology demands stabilization from the thoracolumbar to the lumbosacral junction. Wide posterior decompression with lateral recess and foraminal decompression is necessary to relieve symptoms of spinal stenosis. Spinal stabilization with a long lumbar construct is required to prevent spinal instability and progression of the spinal deformity.19,20 Deformity correction may be achieved by several methods, including rod derotation, cantilever reduction maneuvers, and distraction/compression maneuvers. Distraction in the concavity should be done with caution to avoid loss of lumbar lordosis. Deformity correction achieves an indirect neural decompression as well.
The surgeon should not end the instrumentation at a segment with: 1) posterior column deficiency, 2) listhesis in any direction, 3) a rotated spinal segment, 4) a region of junctional kyphosis, or 5) at the apex of deformity in coronal and sagittal plane.
The importance of restoring lumbar lordosis and sagittal balance has been reported in the literature. Decreased lumbar lordosis and poor sagittal balance have been correlated with pain and functional loss.21–23 Reconstitution of sagittal alignment can be performed by spinal osteotomy. Restoration of the anterior column using structural anterior column support may be achieved by anterior, posterior, or transforaminal lumbar interbody fusion techniques.
The thoracolumbar junction (T10-L2) has unique anatomic characteristics. It serves as the transition from the immobile thoracic spine to the mobile lumbar spine. There is a change in the orientation of the facet joints from the coronal plane proximally, to the sagittal plane distally. The sagittal alignment changes from thoracic kyphosis to lumbar lordosis.
Biomechanically, the true ribs tend to increase the stability of the thoracic spine through the thoracic rib cage. The rib cage effectively lengthens the transverse dimensions of the spine, giving the thoracic spine greater resistance to bending in the sagittal, coronal, and axial planes. The upper 10 thoracic vertebrae (T1–T10) take this mechanical support through the true ribs, but T11 and T12 have floating ribs without costosternal articulation. These levels lack the ligament support provided by the costovertebral articulations, the costocorporeal joint and the costotransverse joint. Stopping at or distal to T11 and T12 puts the adjacent segment at a biomechanical disadvantage.24
Problems Related to the Segment Adjacent to the Upper Instrumented Level.
Problems seen in the proximal segments after long fusion for degenerative lumbar deformity consist of 1) proximal adjacent segment degeneration, 2) compression fracture proximal to the fusion mass, or 3) screw failure at the uppermost instrumented vertebra.
Proximal adjacent segment degeneration can be detected by the presence of the following findings in the proximal adjacent vertebral segment: 1) progressive narrowing of disc height, 2) progressive decrease in lordosis or increase in kyphosis, 3) osteophyte formation and sclerosis of adjacent endplate, or 4) translation in coronal or sagittal planes.
A review of the available literature on this subject provides some insight into the pathoetiology of this condition.25–28 Swank et al29 presented surgical outcomes in long lumbar fusions from L1 or L2 to S1 done for a variety of spinal pathologies, including degenerative spinal stenosis, scoliosis, postlaminectomy syndrome, pseudarthrosis, and spondylolisthesis. Of 20 patients, 7 patients required reoperations for fractures at or above the UIV, adjacent segment degeneration, or infection. Only 2 patients had good or excellent clinical results. They concluded that instrumented lumbosacral fusions with UIV at L1 or L2 have an unacceptably high mechanical failure rate in adult patients and cannot be recommended. In a recent presentation, Simmons et al30 reported adjacent segment problems in 60% of elderly patients who had lumbar fusion extending to L1 or L2.
Bridwell31 stated that choosing the proximal level requires identification of the stable, neutral, and horizontal vertebra in the coronal and sagittal planes. He typically terminates the fusion proximally at T10 or T11 in his adult lumbar scoliosis patients.
We reviewed our experience24 with 35 degenerative lumbar deformity patients who underwent fusion to L5 or S1 with the aim of determining the impact that the choice of the UIV has on the adjacent segment. In Group I (n = 14), fusion extended proximal to L1 or L2. In Group II (n = 14), fusion extended to T11 or T12. In Group III (n = 7), fusion extended to T9 or T10. The apex of their deformity was below L1 on coronal and/or sagittal planes. Of the 35 patients, 20 had scoliosis ≥15°, 23 had local kyphosis ≥10°, and 8 had kyphoscoliosis (scoliosis ≥15° and local kyphosis ≥10°) (Table 1). All patients, whose average age at the operation was 62 years, were treated by a posterior procedure alone using segmental pedicle screw instrumentation1 and had a minimum follow-up of 2 years (range, 2–5.8 years). Their distal fusion terminated at L5 or S1 and patients who had distal instrumentation failure were excluded. Posterior decompression at the stenotic levels was performed in 27 patients (77%). Decancellation or osteotomy was carried out in 8 patients (23%). The operation time was 190 ± 50 minutes with a blood loss of 2,909 ± 999 mL in Group I, 198 ± 26 minutes with 2,717 ± 1715 mL in Group II, and 216 ± 49 minutes with 3,407 ± 2,324 mL in Group III.
Fifty percent of Group I and II patients had proximal adjacent problems in contrast to 14% in Group III (Table 2). Loss of sagittal balance during follow-up occurred in 36% of Group I, 36% of Group II, and none of Group III. Coronal balance and correction were well maintained during follow-up in all groups.
We admit that this report is limited by short follow-up and small sample size. We have recently completed reanalysis of most of these patients (unreported data) with minimal follow-up of 4 years and have similar results. Ultimately longer follow-up of a larger cohort will be necessary to corroborate these preliminary results.
We found that the patient in Figure 3 illustrates the issues related to selection of L1 using the currently accepted criteria for determining the UIV. She developed proximal adjacent degeneration at T12-L1 2 years after the index procedure. Many basic science and clinical studies have shown that increased mobility and increased intradiscal pressure are associated with adjacent segment degeneration. Increased motion and stress concentration at this area can induce instrumentation failure and adjacent segment problems.32–35
Some surgeons prefer to extend the proximal fusion routinely to the upper thoracic spine (T2–T4). This adds substantially more levels of fusion and is accompanied by greater perioperative morbidity and mortality, increased operative time, and intraoperative blood loss, especially elderly patients.14
In conclusion, proximal adjacent segment problems and sagittal imbalance were more common when proximal fusion ended from T11 to L2. Therefore, I recommend extending fusion to T10 or above to achieve a longer survival of the adjacent segments in the surgical treatment of degenerative lumbar deformity.
Debate: Steven Mardjetko, MD
Adult scoliosis is defined by the SRS as the presence of coronal plane deformity in individuals presenting after age 20.12 The consequences of adult scoliosis depend on the age at presentation. In early adulthood, the deformities can be managed using principles and techniques applied to adolescent idiopathic scoliosis.1,5–7,12,36,37
But starting in mid adulthood and extending through the remainder of life, the “typical” adult scoliosis is characterized by the progression of coronal plane deformity that is usually rendered stiff by the multilevel degeneration of facet joints and discs of the lumbar and lumbosacral spinal deformity. The degenerative process contributes to the development of lumbar segmental and regional kyphosis, and the patient's global sagittal balance may be affected by thoracic, thoracolumbar, and lumbar kyphosis, as well as cervical degenerative kyphosis and hip flexion contractures. Asymmetric disc space collapse and facet erosions can result in coronal plane, sagittal plane, and rotational subluxations creating segmental instability. Central, lateral recess, foraminal, and dynamic types of spinal stenosis result in lower extremity radicular and neural claudication syndromes.5,8,12,38,39
The surgical management of adult scoliosis is based on solving the constellation of problems with which the surgeon is presented. The surgical plan needs to be tailored to the patient's individual needs.5–7,40
The surgical treatment will therefore need to address the spinal stenosis with the necessary neural decompression. The rigid lumbar and lumbosacral fractional curves need to be mobilized via wide facet joint excision. Sagittal plane deformity needs to be addressed on a segmental or a regional basis with either anterior release and structural anterior grafting techniques, posterior shortening osteotomies, or both. The goals should be to achieve normalization of the sagittal plane, balance in the coronal plane, and the necessary neural decompression. For long-term success, a solid fusion must be obtained.
This surgical treatment plan should be done with efficiency, limiting stabilization to pathologic segments while addressing sagittal and coronal plane alignment at the segmental, regional, and global levels.1,6,7,11,12
Because of the multisegmental nature of adult spinal deformity, the surgeon must select the upper and lower end vertebrae based on the patient's particular spinal deformity, sagittal profile, and the extent of the degenerative disease process. In most adult lumbar curves, the surgeon must extend distally to the sacro-pelvis, although occasionally stopping at L5 may be considered. This controversial topic is the subject of another debate in this issue.11,12,31
But how far should one extend the fusion proximally? Based on a review of the literature, some guidelines/criteria with regards to determining the proximal level have been advanced by numerous authors.6,7,11,12,31
- The proximal end vertebra should be in the “stable zone,” defined by the coronal vertical axis ±2 cm. If the coronal plane deformity allows, the UIV should be normalized in the coronal plane, aligning the superior endplate and the adjacent disc in the horizontal plane. Theoretically, this should decrease shear forces associated with a coronally angled disc space.
- The upper end vertebra should allow for restoration of the sagittal alignment within the instrumented segments and should serve as the transition to normally aligned proximal segments in the sagittal plane.
- There should be little or no disc or the facet joint degeneration of the adjacent spinal segments.
- The upper end vertebra should have neutral or nearly neutral rotation.
- The adjacent segments should be stable in all directions, and the posterior elements should be intact.
Using these criteria, a chosen upper end vertebra will vary depending on the patient's degenerative pathoanatomy, curve characteristics, and sagittal profile. The upper end vertebra usually ranges from T2 to L2 when considering a standard lumbar curve, based on evaluation of degenerative segments, and sagittal plane alignment. In most patients with primary degenerative lumbar curves and acceptable thoracic and thoracolumbar sagittal alignment, the surgeon can stop the fusion in the lower thoracic or upper lumbar spine from T10 to L2.
While coronal plane correction and balance should be addressed, it has been shown that patient outcome is most strongly associated with sagittal plane indexes and sagittal balance.21,22 It is critical that the surgeon do all in his power to guarantee maintenance or restoration to a normal sagittal balance.
Long-term durability of the patient's spine after scoliosis fusion is an important secondary consideration. Once the immediate surgical needs have been satisfied, we must strive to prolong the “survival” of these spinal reconstruction procedures. Can the choice of the upper and lower instrumented vertebra have an impact on spinal fusion “survival?” The short answer is yes!26–28,34,35,41,42 Through long-term follow-up of the adolescent Harrington rod/fusion population, the choice of lower instrumented vertebra has a profound effect on the “survival” of the adjacent spinal segments, with fusions to L4 resulting in precocious breakdown of the adjacent segments within 10 to 20 years, and fusions to L3 or above generally lasting beyond 30 years.6,11
Dr. Suk raises the possibility that the choice of the UIV in adult degenerative scoliosis may have a similar impact on long-term spinal construct durability, and adjacent segment degeneration in the adult degenerative scoliosis patient.
What are the mechanisms by which an initially successful adult deformity reconstructive procedure may ultimately be compromised? Unfortunately, there are many!
- Adjacent segment degeneration is a predictable mode of failure that will occur at any spinal segment adjacent to an instrumented spinal fusion in time. It has a reported incidence of 26% at 5-year follow-up25–28 Risk factors for this include preexisting sagittal plane abnormalities, preoperative adjacent segment degeneration, sagittal or coronal instability, and facet joint violation.26,27,31 This phenomenon has even been recognized in surgically treated adolescent scoliosis patients, where it is associated with preexisting junctional kyphosis.28Adjacent segment failure, aptly termed “transition syndrome,” may present as precocious adjacent segment degeneration with or without spinal stenosis and segmental instability. The etiology is thought to be due to the natural age-related progression of the degenerative process, coupled with the post surgical effect of spinal stiffening created by fusion/instrumentation procedures. Does this phenomenon apply to the UIV? Yes. I personally have treated adjacent segment degeneration at virtually every spinal level. To my knowledge, no spinal region has proven itself immune to this problem. Figure 4 demonstrates adjacent segment degeneration with translational instability at T11–T12 and T2–T3 in the same patient over a 6-year time course.
- Osseous failure. Fractures of the UIV, or fractures of adjacent or remote unfused vertebra, have been recognized as an early and late complication in the adult deformity population. Osteoporosis and positive sagittal balance appear to be risk factors. Most commonly, these fractures occur in or adjacent to the UIV (Figure 5a), but occasionally fractures may be identified many segments proximal to the UIV (Figure 5b). Fractures of the pedicles or the corpus of the UIV that occur early in the postoperative period can compromise construct integrity, with loss of proximal segment control, increased risk of pseudarthrosis, and loss of correction in sagittal and coronal planes. Additionally, unexplained pain in the lumbopelvic region may be secondary to stress fractures of the sacrum and pelvis that can occur at any time after lumbopelvic reconstructions. This diagnostic possibility should be considered in the appropriate clinical setting.
- Natural age-related progression of thoracic kyphosis (Figure 6) is a gradual increase in thoracic kyphosis that does not appear to be due to a single segment pathology. This may be due to progressive disc degeneration associated with attenuation of spinal extensor strength commonly seen with the aging process.10Figure 6a is an example of a T10 to pelvis fusion in which a gradual increase of kyphosis was noted over 5 years. Extension to T2 restored the sagittal balance (Figure 6b).
- Degeneration/disease in remote spinal segments. Disorders in cervical and thoracic spinal regions may be symptomatic and require management (Figure 7). While usually these are managed independent of the spinal deformity, occasionally splicing spinal constructs may be necessary to address the patient's combined spinal pathology.
- Hip and knee degeneration. The spine surgeon must be cognizant of degenerative disease of the hips and knees that can contribute to sagittal imbalance and compromise the patient's outcome.
Suk has argued that stopping at lower thoracic and upper lumbar segments results in precocious degeneration of the adjacent open segments do to the intrinsic mobility of these segments.24 He has used the argument that it is better to extend fusion routinely to T9 or T10 in all cases. His argument is based on a sound biomechanical principle of terminating instrumentation in an intrinsically “stable” spinal region. But currently, he bases this recommendation on his own experience, a small retrospective case-control study with medium-term (4-year) follow-up.24
Adopting Suk's approach has the disadvantage of greater blood loss and increased surgical time. This is borne out in his own data (Tables 1, 2).24 In addition, there is incremental increased risk associated with application of instrumentation across the thoracolumbar spine, greater risk of pseudarthrosis with the addition of the nonunion prone thoracolumbar junction, and greater cost associated with the need for more implants.23 The adoption of such a policy may result in unnecessary fusion of 3 to 4 additional spinal segments in selected patients.31
While the incidence of transition syndrome may be effected by the choice of the proximal segment, to date there is no well-designed study that can confidently make the recommendation that instrumenting to T10 improves the long-term results while not incurring greater risks. The best way to determine factors that may be operative in transition syndrome would be to track patients for long periods of time in prospective fashion. Using these data, one may perform a “survivorship analysis” of the adjacent segments of adult scoliosis patients. Only in this way will we be definitively able to answer the question of L1 versus T10. To date, the data are not compelling enough for me to institute this change in my own practice.
Summary: Harry Shufflebarger, MD
After extensive preoperative consultation, this patient decided to undergo surgical treatment.
Based on her sagittal profile, it was recommended that a same-day posterior-anterior-posterior procedure be performed. This three-stage procedure was chosen as it is the author's experience that this sequence most reliably restores lumbar lordosis and achieves complete coronal correction.
Stage I includes multiple-level wide posterior releases, bilateral pedicle screw insertion at every level from T12 to sacrum, and bilateral iliac screw insertion in the Galveston position. Iliac crest graft harvesting is performed in Stage I. Decompression is achieved by laminectomy from L3 to L5, and the posterior wound is closed. Accomplishing a wide posterior release permits maximum lordosis by subsequent anterior distraction. In my experience, lumbar facet arthrosis usually limits the amount of anterior distraction possible if the posterior release in not accomplished before the anterior procedure.
Stage II consists of anterior lumbar interbody fusion via a left paramedian approach, with titanium mesh cages, autograft, and BMP from L2–L3–L5–S1. Two small cages were placed at each interspace, each cage containing BMP sponges. Previously harvested autogenous iliac bone graft is packed anterior to the cages. The iliac graft was supplemented with morselized autogenous bone from the laminectomy. The anterior release/fusion procedure assures restoration of lumbar lordosis, maximizes coronal plane correction, and substantially increases the fusion rate.
Stage III involves rod insertion, segmental correction via sequential compression distraction sequences, and posterior lateral fusion from T12 to the sacrum. The goal is to maximize segmental lumbar lordosis and achieve complete coronal plane correction. Autogenous iliac bone and morselized laminectomy local bone constitute the graft material.
The rationale for selecting T12 as the proximal instrumented level is based on several radiographic findings. On the standing anteroposterior radiograph (Figure 1a), the T12 vertebra is bisected by the center sacral line and is neutral in rotation, whereas the L1 vertebra is not. In my experience, stopping on a rotated vertebra appears to accelerate adjacent segment degeneration.
On the standing lateral radiograph (Figure 1b), the T11–T12 segment shows no degeneration, no instability, and no segmental kyphosis. The thoracolumbar junction (T10–L2) alignment is straight, and there is thoracic hypokyphosis extending to the proximal thoracic region. This individual's sagittal balance is normal. Hence, it was not felt that the fusion had to be accomplished proximal to T12. The sagittal MRI reveals little or no disc degeneration in the thoracolumbar junction.
Figure 8 (anteroposterior and lateral standing radiographs at 2 years postsurgery) reveals intact implants, solid circumferential fusion, complete coronal plane correction, and restoration of normal sagittal alignment. The T11–T12 disc appears healthy.
At the 2-year follow-up, this patient is essentially asymptomatic, has resumed most of her presurgery activities, and is most happy with her outcome to date. I concede that 2 years is a relatively short follow-up and that pseudarthrosis and adverse adjacent segment changes may become manifest in the future.
It is recognized that natural age-related changes in the patient's sagittal alignment3,10 and adjacent segment degeneration will uniformly occur with time regardless of which UIV is chosen.25–28,32–35,41,42 The patient and family should be informed of this fact.
Ultimately, the surgeon should tailor the surgical procedure to each patient's particular needs, in keeping with the philosophy that the goal of surgical intervention is to achieve a well-balanced, stable, painless, and durable spine with the fewest number of segments fused.
I would like to thank both debaters for the time and energy they put forth in defending their assigned positions.
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