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Abstract:
Adult scoliosis is defined of spine deformity with a Cobb angle of more than 10° in the coronal plane, which could be sequelae of untreated, non-operative or failed operative adolescent idiopathic scoliosis, or de novo spinal deformity developing in the adult. Surgery is indicated if the non-operative management are not well evident. The possible surgical technique can be divided in posterior, anterior or combined procedures and the problem is that how to choose the vertebrae in the fusion .The most common complications are implant fixation loosing and pseudarthrosis and it is necessary to pay attention to the osteoporotic patients who will be operated .However, most studies suggest a significant improvement in quality of life and a high rate of patient satisfaction with the correct management.
J.Orthopaedics 2011;8(1)e1
Keywords:
adult scoliosis ; etiology ; management; surgery; complication
Adult scoliosis is diagnosed as a spinal skeletal deformity with a Cobb angle of more than 10° in the frontal plane. It could be sequelae of untreated, non-operative or failed operative adolescent idiopathic scoliosis, or de novo spinal deformity developing in the adult .It may be complex to determine the primary cause of the spine deformity though once the deformity has obviously progressed. Generally speaking, adult scoliosis is always characterized not only by the presence of scoliotic deformity but also by the associated degenerative changes including spinal stenosis , spondylolisthesis , rotational or lateral subluxation , lumbar hypolordosis , and relative rigidity of the spinal deformity. Because of the associated degenerative changes, patients with adult scoliosis present not only with back pain but may also present with radicular and/or neurogenic claudication symptoms.1-6
1 Etiology:
Adult degenerative scoliosis can be divided into 2 categories .In one hand ,the patie-nts may manifest with adult scoliosis due to progression of untreated or inadequately treated adolescent idiopathic scoliosis .And on the other hand ,they may present with de novo adult scoliosis.
1.1 De novo scoliosis:
De novo scoliosis can be called senescent lumbar scoliosis
which present no history of idiopathic scoliosis ,but have a deformity in coronal plane .The curves are commonly associated with loss of lumbar lordosis ,ranging 10°-60°(mean 24°) and the degenerative changes of the facet joints and the intervertebral discs always affect the curves .The lumbar curve is often a dual curve with alarger one in the proximal lumbar spine ,generally the apex at L2 or L3. 6
In the degenerative scoliosis patients they often accompany with osteoporosis , degenerative disc disease, osteoarthritis, compression fractures, spinal canal stenosis ,endochondral abnormalities, and facet tropism .But none of them implicated that they have been directly related. 7-9
Vanderpool et al and Bridwel's study showed that the adult-onset curves were secondary to osteomalacia and osteoporosis.10-11But,in a follow-up random population study of Robin et al ,the authors found no direct correlation between osteoporosis and the development of scoliosis; they reported that there was no relation with the degree of osteoporosis, prior scoliosis, or sex of the patient. And they concluded that osteoporosis is not a cause of adult scoliosis. In fact, they hypothesized that adult degenerative scoliosis may have an etiology similar to that of adolescent idiopathic scoliosis.Besides,a recent study showed no correlation between osteoporosis and the prevalence of scoliosis.12-14,34
Degenerative changes of facet joints and intervertebral discs may be leading to asymmetric loading of lumbar spine ,which can be thought of leading to formation of a lateral and rotational deformity. The asymmetric degeneration ,is principally considered of progression of curve ,and other factors such as osteoporosis, osteoarthritis ,can worsen the asymmetric collapse ,causing the deformity in the frontal plane .Although not well researched ,this model seems to explain well the heterogeneous patients who have this condition .In addition ,the sagittal deformity may be associated with focal degenerative changes such as the presence of lateral subluxation , anterolisthesis, retrolisthesis, and/or rotational deformity. As these changes occur, osteophyte formation often develops at both the facet joints and the intervertebral discs .These changes combined with hypertrophy and calcification of the ligamentum flavum and joint capsules lead to development of central lateral recess and foraminal stenosis.15
Furthermore, Another theory for the development of de novo scoliosis is that adult scoliosis may be triggered by nerve root irritation, secondary to foraminalor lateral recess stenosis. This causes sciatic or painful scoliosis, which can be initially flexible, but when longstanding, structural deformity may develop and become selfsustainable and continues to progress. This theory is further supported by the well-described sciatic or painful scoliosis,which may result from nerve root compression from a herniated nucleus pulposus. Although the latter usually resolvesonce the inciting compression is removed, that may not be the case in older individuals with a more degenerative.6
1.2 Progressive idiopathic scoliosis
Many studies demonstrated that adolescent idiopathic scoliosis continue to progress in vary forms, whether they are untreated or conservative,or whether they have fusioned, with or without instrumentation. Weinstein and Ponseti studied a large cohort of patients with adolescent idiopathic scoliosis for over 40 years and found that 68% of patients with adolescent idiopathic scoliosis had progression of the curvature after reaching skeletal maturity.14.There may be a obvious degeneration and imbalance presenting in the sagittal and in the frontal plane of the short lumbar curve. The sagittal deformity is almost always exclusively a flat back syndrome or a loss of physiological lord-osis and in extreme situations a real kyphosis ,developped in the asymmetric manner of degeneration of facet joints.16
2 Management
2.1 Nonsurgical management
The non-operative options are often chosen and they consist of non-steroid anti-inflammatory medication ,muscle relaxants, pain medication, muscle exercises, etc .However ,its efficacy are not well evident in the available literature. Regardless of no effect ,nonsurgical management should be attempted ,and it may strengthen the results of later surgery.14
2.2 Surgical approaches
How to choose the patients to be operated appropriately is complex in terms of decisions making ,but the most common indication is that nerve root symptoms and spinal stenosis. Back pain is one of less common indications. The possible surgical technique can be divided in posterior, anterior or combined procedures. In all these procedures a simple decompression or stabilization can be done, or both can be combined.17 Fusion , should be of-ten instrumented and segmental pedicle screw fixation is the preferred fixation technique .Generally, poly-axial pedicle screw systems are most appropriate. If extension to S1 is needed, it is crucial to incorporate the pelvis or add 2 additional points of fixation in the sacrum. However , the question is that how many vertebrae to be chosen in the fusion .The same principles followed for adult idiopathic scoliosis should be followed here. For degenerative scoliosis, it is not usually possible to stop caudally at L3 or L4, as most of these curves occur at those levels. Often times it is necessary to go down to the sacrum.3, 35
2.3 Complications
2.3.1 Loosing of implant fixation
Kyu-jung Cho et coworkers reported that loosened fixation seemed relatively high in fusion of S1 than that in L5.A loosening of screws was defined as a change in the position and angle of the screws using the following criteria (1) A 3 mm or more change in the position of the screw tips relative to the endplates of L5 or S1; (2) a 5° or greater change in the angle between the screws and the endplate of L5 or S1. The surgical indication is done if loosing fixation is diagnosed appropriately and the patients have symptoms .18-19, 33
2.3.2 Pseudarthrosis
Pseudarthrosis was closely related to the loosening fixation .It is said that there are three main factors demonstrate pseudarthrosis:(1)Loss of correction and the subsequent progression of the deformity,(2) Implant failure such as the breakage of the rod, (3) A 5° or greater range of motion within a segment on flexion/ extension radiograph. Loosening of screws also suggests pseudarthrosis.19 However, if none of the 3 previous conditions occurred, the condition was usually classified as loosening of screws.
Pseudarthrosis at sacral fusion was found to be the most mainly risk factor for sagittal decompensation. Eighty percent of patients with pseudarthrosis resulted in sag-ittal decompensation. Pseudarthrosis may cause a loss of correction and progression of the deformity. If the sacral screws are loosened or pulled out pseudarthrosis develops easily at the lumbosacral junction, even in patients with a normal sagittal balance immediatelyafter surgery.20 It is found that the lowest pseudarthrosis rate at L5–S1 is associated with complete sacropelvic fixation and surgery in patients under the age of 55 years .By complete sacropelvic fixation, it meaned bilateral bicortical S1 screws out through the promontory anteriorly, bilateral iliac screws and anterior column support at L5–S1.21-22 ,33
2.3.3 Perioperative medical complicaitons.
Blood loss,Kyu JC et al encoutered Intraoperative blood loss are 2,754 ml versus 2,938 ml ,hence ,preoperative preparations are considered of importance.23
Post-surgery pain ,which is the primarily indicated for re-operation. 24It is well understood of mechanism for this pain. Islam et al have said that, Among 34 patients with significant post surgical pain, 56% reported reduced pain after additional surgery, while 44% did not; in the same study, 2 patients who did not have pain before surgery reported pain in the follow up .This pain ,perhaps ,is caused by an effect of aging ,or by sagittal deformity not correcting .But answer to surgeons ,seem to be easy ,to re-operate.18
There is a potential risk for nerve root paresis ,partial ou total paraplegia,etc ,Neurological deficits can result from vascular ,metabolic ,or machanical complications .After spine deformity operations ,some of them recover spontaneously.25-27,33
Furthermore ,we can see the others complications such as pulmonary complications ,urinary infections, deep wound infection ,delayed infections ,gastrointestinal bleeding,delirium,etc.28
After operations ,most patients who still professionally active don not to their previous work if it is physically demanding job ,but almost all of those had stopped working before surgery ,because of pains limitations .Therefore ,we have to pay attention to the patients who don not find the jobs after surgery ,it is necessary to support them in time ,spiritually ,psychologically ,socially ,or specially.
2.3.4 Special considerations of complications in osteoporotic patients
2.3.4.1 In the adult deformity patient, osteoporosis is often considering as a major factor involved in the long-term success of surgical intervention . Besides, bone quality can play a important role in success of a long construct fusion .The elderly osteoporotic patients undergoing multilevel fusions with rigid instrumentation are at increased risk for developing complications such as insufficiency fracture, correction loss, and pseudoarthrosis. Constructs must take into account the bone quality and be designed with this in mind.3
2.3.4.1 Implant consideration
A concerning number of titanium rods have been noted to break with loss of correction. If interbody grafts are not present throughout the lumbar spine .A change back to stainless steel has been instituted to take advantage of the lack of notch sensitivity in stainless steel. This leads to a lower rate of fracture propagation and implant failure. Rod failure can occur even with a solid fusion due to implant bending and metal fatigue. Anterior column support is also an important implant concept in increasing fusion rates. The choice of anterior column support is based on the multiple factors and patient comorbidities. Choices of anterior column support include tricortical iliac grafts or patella wedges, pure cortical grafts such as femoral or tibial rings, titanium, or carbon-fiber Although autograft would be ideal, the multilevel approach to anterior work makes this impractical and allografts are typically used. Augmenting allograft with various growth factors such as BMP-2 may improve graft incorporation and decrease the rate of pseudoarthrosis. We have preferred patella wedges due to their more rapid clinical incorporation and modulus of elasticity that matches bone. This decreases the risk of end-plate fracture and subsidence of that structural graft.3
Although the altered mechanical properties of osteoporotic bone and the morphologic vertebral changes seen in osteoporosis, it has been shown that effective spinal instrumentation can be performed in patients with osteoporosis with a relative degree of safety .However, one must realize that in the presence of osteoporosis the decreased mechanical properties of the bone increases the risk of fixation failure at the bone-metal interface. Low bone mineral density has been directly correlated with decreased pedicle screw pullout strength, decreased pedicle screw cutout torque, and decreased pedicle screw insertional torque in biomechanical studies.Thus, in the osteoporotic spine it is important to use a variety of techniques to optimize the strength of each individual fixation site while following surgical and biomechanical principles that allow one to minimize the loading conditions for each fixation point.29-32
3. Conclusion
Adult scoliosis is described deformities in the coronary plane in patients with or without the history of adolescent scoliosis. Careful preoperative assessment for surgical planning should always be done if the operation is indicated. Despite the high risk of complications in patients undergoing reconstructive surgery for scoliosis, most studies suggest a significant improvement in quality of life and a high rate of patient satisfaction. However appropriate patients selection and understanding patient expectations are crucial in achieving a successful outcome.
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