ab c Case Introduction Female patient with a 22-year history of low back pain and a de novo scoliosis (primary degenerative scoliosis) exemplify- ing the natural history of this scoliosis type. The patient first sought medical help for low back pain at the age of 33 years. The radiograph exhibited a short left-convex lumbar scoliosis (8°), which in retrospect can be attributed to a disc degen- eration of L3/4 (disc space narrowing) and an asymmetry at the L2/3 level (a). At that time, the patient was treated with NSAIDs and physiotherapy with some improvement. However, she was never really pain-free. When she was 50 years old, she had increasing back pain with radiating pain mostly into the right anterior thigh. In the meantime, the patient entered menopause, and the curve now measured a Cobb angle of 25° with a lateral translation and rotation of L3 toward the left side ( b). Five years later the curve measured 40°, an average 3° curve increase per year. The curve was now clearly identifiable as a short, left-convex curve from L2–L4 (end vertebrae) ( c). The overall frontal balance was still more or less in equilibrium. However, the sagittal profile converted toward a lumbar kyphosis. The patient now complained not only about difficulty of controlling back pain, but also about classical claudication symptoms when walking 400–500 m. The pain disappeared when resting. The back pain was much less when resting in bed, but increased when standing up in the vertical position. The translation/rotation of the apical vertebra L3 had also increased compared to 5 years previously. This curve demonstrates a truly progressive degenerative de novo adult scoliosis, which ended with the complete set of symptoms and signs which finally necessitate surgery. This process involves a mechanical deteriora- tion of the lumbar spine, which expresses itself in clinical signs and symptoms related to instability, mostly axial-vertical instability with some translational component, central canal and/or foraminal neurocompression, fatigue of unbalanced paravertebral muscles and finally curve progression. The understanding of the natural history and behavior of such a pri- mary degenerative scoliotic curve may help to make a decision for or against relatively early surgery. In the case of early surgery, the intervention may be more limited and simple, both for the patient and the surgeon. The prevalence of degenerative scoliosis is increasing Degenerative scoliosis seems to be becoming more frequent in an increasingly aging society for several reasons, which may include the more aggressive and pre- cise diagnosis than was possible 20 years ago, a different perception of pain in a modern urbanized society, and the desire of a large component of our society to be active in sports and to pursue leisure activities also after retirement. It seems, how- 714 Section Spinal Deformities and Malformations ever, that degenerative scoliosis is not a characteristic disease of industrialized society, since the same pathology can be observed in other, less developed socie- ties [7]. Pathogenesis Primary (de novo) degenerative scoliosis results from segmental degeneration Primary degenerative adult scoliosis, specifically in the lumbar spine, is charac- terized by a quite uniform pathomorphology and pathomechanism [1]. The asymmetric degeneration of the disc and/or the facet joint leads to an asymmet- ric loading of the spinal segment and consequently of a whole spinal area. This again leads to an asymmetric deformity, for example scoliosis and/or kyphosis [6, 14]. Such a deformity again triggers asymmetric degeneration and induces asymmet ric loading, creating a vicious circle ( Fig. 1a).Thedestructionofdiscs, facet joints and joint capsules usually ends in some form of uni- or multisegmen- tal sagittal and/or frontal latent or obvious instability. There may not only be a spondylolisthesis, meaning a slip in the sagittal plane, but also translational dis- locations in the frontal plane or rather three-dimensionally when the instability expresses itself in a rotational dislocation [15]. The biological reaction to an unstable joint or, in the case of the spine, an unstable segment, is the formation of osteophytes at the facet joint (spondylart- hritis), and at the vertebral endplates (spondylosis), both contributing to the increasing narrowing of the spinal canal together with the hypertrophy and calci- fication of the ligamentum flavum and joint capsules, creating central and reces- sal spinal stenosis ( Fig. 2). The pathomorphological and pathomechanical rela- tionship directly relates to the clinical presentation of an adult degenerative scoli- The progressive degenera- tion and deformity often leads to central and foraminal stenosis osis (Fig. 1b). The osteophytes of the facet joints and the spondylotic osteophytes, however, may not sufficiently stabilize a diseased spinal segment. Such a condi- tion leads to a dynamic,mostlyforaminal stenosis withradicularpainorclaudi- cation type pain, specifically when the spine is loaded vertically. ab Figure 1. Pathogenesis of degenerative scoliosis a Degenerative scoliosis results from a close interaction of asymmetric loading, degeneration and deformity. b The clini- cal symptoms are closely related to the pathomorphology. Degenerative Scoliosis Chapter 26 715 Figure 2. Degenerative changes Deformity and spinal imbalance lead to secondary degeneration, i.e., facet joint arthrosis (hypertrophy), disc degenera- tion, spondylosis spurs and osteophytes, and calcified ligaments as a biological reaction with the goal of stabilizing the spine. As a consequence spinal stenosis develops. When decompression is performed destabilization results. Classification Degenerative scoliosis forms a major part of the adult scoliosis group. This group comprises a wide spectrum of different pathologies, which may look very similar at the end-stage, when many patients are seeking help from a spine surgeon for the first time [15]. These patients usually have a long history of back pain and spi- nal discomfort and have undergone all the possible symptomatic treatment modalities such as exercise, acupuncture, braces and other complementary med- ical measures as well as pain medication. There is no established classification system for degenerative scoliosis [1, 7]. However, the most important distinction is between primary degenerative scoli- osis and secondary degenerative scoliosis ( Table 1). Table 1. Classification of degenerative scoliosis Primary (de novo) degenerative scoliosis Secondary degenerative scoliosis develops de novo after skeletal maturity results from degenerative alterations of curves existing prior to skeletal maturity Classification systems or degenerative idiopathic scoliosis is inadequate to describe de novo scoliosis Several attempts have been made to elucidate some systematic structure in this kind of pathology. A classification on the basis of the curve type, very much as in the idiopathic scoliosis classification by Lenke [21], has been proposed. This clas- sification may be able to cover the adult idiopathic scoliosis group with second- ary degeneration but is not necessarily adequate for the primary degenerative scoliosis type. Another attempt at classification has recently been presented by Schwab et al. [13, 27], who distinguished three groups based on measurements of the endplate obliquity of L3 in the frontal plane, and of the lumbar lordosis mea- sured between the L1 and S1 superior endplates in the sagittal plane of a standard X-ray. 716 Section Spinal Deformities and Malformations This is obviously a classification which can be applied solely to primary degener- ative lumbar scoliosis. The three distinct types with increasing severity from Type1toType3are: Type 1 – lordosis >55°, L3 obliquity <15° Type 2 – lordosis 35–55°, L3 obliquity 15–25° Type 3 – lordosis <35°, L3 obliquity >25° The interesting characteristic of this classification is the attempt to correlate the objective radiological findings with the self-reported pain and disability. We have recently proposed an etiological classification which basically distin- guishes three types, Type 3 being subdivided into two subtypes [1]: Type 1 – primary degenerative scoliosis (“de novo” form), mostly located in the lumbar or thoracolumbar spine. Type 2 – progressive idiopathic scoliosis in adult life of the thoracic, thora- columbar and/or lumbar spine. A rough distinction can be made between adult idiopathic scoliosis in patients less than 40 years of age and those aged over40years. Type 3 – secondary degenerative scoliosis comprising: Subtype 3a: degeneration of secondary curves following idiopathic or other forms of scoliosis or occurring in the context of a pelvic obliq- uity due to a leg length discrepancy, hip pathology or a lumbo- sacral transitional anomaly, mostly located in the thoracolum- bar, lumbar or lumbosacral spine. Subtype 3b: scoliosis secondary to metabolic disease (mostly osteoporosis) [18] combined with asymmetric arthritic disease and/or verte- bral fractures. There is no classification gold standard The clinical entity of an adult degenerative scoliosis can indeed be present since childhood or adolescence and can become progressive and/or symptomatic only in adult life [5, 24], or a scoliosis may appear de novo in adult life only without any precedence in early life. In this chapter we deal predominantly with Type 1 scoliosis, partially with Type 3a and only marginally with Type 2. The chapter is not closed over the classification issue, since an ideal classification must be sim- ple, easy to apply and imply treatment options that are designed to correlate well with the clinical picture and outcome. Clinical Presentation History Patients with adult degenerative scoliosis seek medical help for four major rea- sons[1,6,7,16,23],whichalsopresentascardinal symptoms: back pain claudication symptoms and/or radicular pain neurological deficits increasing deformity (curve progression) Cosmesis does not have the same significance as in adolescent scoliosis; neverthe- less recent studies show that the self-perception of scoliotic adult patients plays an important role in a health assessment analysis [13]. The clinical picture as out- lined above can be substantially aggravated by concomitant osteoporosis [18]. Patients have a long history of back pain before they complain of claudication symptoms Usually these patients have a long history of back pain and only in a second stage do they complain about leg pain, claudication symptoms and difficulty, for instance, climbing or descending stairs. Most of these patients experience pain Degenerative Scoliosis Chapter 26 717 when in an upright position under an axial load and are more or less pain free when lying down. Most of them report loss of height over time and some patients have increased pain when turning in bed or twisting during physical activity, which relates to a certain instability of the deformed and mechanically weakened spine. Back Pain Back pain is often related to instability Back pain is the most frequent clinical problem of adult scoliosis, and presents itself with a multiform mosaic of symptoms. Back pain at the site of the curve can be localized either at the apex or in its concavity, and facet joint pain can be local- izedinthecountercurvefrombelowthecurvetoabovethecurve[32,33].Back pain can be combined with radicular leg pain, and can be the expression of mus- cular fatigue or of a real mechanical instability. Unbalanced, overloaded and stressed paravertebral back muscles may become very sore and in return will not contribute to balance the muscle play, consequently becoming part of a vicious circle.Thisisespeciallytruewhenthelumbarcurveisaccompaniedbytheloss of lumbar lordosis [10, 15, 20]. This muscular pain is rather diffuse, is distributed over the lower back and is often permanent at the insertion of the muscle tendons at the iliac crest, sacrum, os coccyx and bony process of the spine. The back pain can be constant and non-specific, which is a bad prognostic sign regarding the treatment outcome. The pain, however, can be present only when the patient is upright, especially when standing and sitting, presenting itself as a so-called Patients often complain of axial back pain due to segmental instability axial pain or only during certain movements or physical activities, pointing rather to a mechanical unstable segment or a whole spinal region. Patients often indicate that they can control their pain well when lying down flat or on their side and when the axial load is taken off the spine. Spinal Claudication Claudication is the second most important symptom of adult degenerative scoli- osis and may express itself as: radicular claudication central claudication Central, lateral and recess stenosis are frequent The symptoms become worse when standing or walking. The patient can have a true radicular pain due to a localized compression or root traction. The roots are compressed not necessarily on the concave side due to a narrow foramen, but oftenontheconvexside, rather expressing a dynamic overstretch of the root [20, 32, 33]. There may, however, be a single or multilevel spinal stenosis which can be central or more in the lateral recess creating claudication symptoms. Root com- pressions can occur at the bottom of the curve or at the transition to the sacrum and can be linked to a hypermobility of an overloaded bottom segment, espe- cially in cases of stiff curves. Short lumbosacral or lumbar curves as counter curves to long fused thoracolumbar scoliosis often show a severe spinal stenosis at the transition from the stiff upper spinal area to the lower lumbosacral area. Neurological Compromise Neurological deficits occur late Neurological deficit is the third most important clinical presentation and may include individual roots, several roots or the whole cauda equina with apparent bladder and rectal sphincter problems. An objective neurological deficit, how- ever, is rare and when present is due to a significantly compressed space in the spinal canal with a relatively acute aggravation and decompensation. A seques- 718 Section Spinal Deformities and Malformations Figure 3. Neurological compromise Sequestrated disc with neurological radicular deficit in a severely degenerated lumbar scoliosis in a 79-year-old frail female patient at the concave side of level L4/5. Since the decompression needed to be done within the curve close to the apex, an additional stabilization of the L4/5 joint has been done in order to avoid a possible progression of the curve and the deterioration of the neurological findings. teredorcalcifieddiscwithinthecurvemaybethecauseofsuchanacuteneuro- logical deficit. It can be accentuated or only become clinically relevant due to a latent or obvious segmental instability ( Fig. 3). Increasing Deformity Osteoporosis accelerates curve progression Finally, increasing deformity due to curve progression is a relevant sign of degen- erative scoliosis [23, 24]. Curve progression may be an issue from the moment the curve occurs in younger age. It may, however, only become relevant when the curve has reached a certain size and/or when osteoporotic asymmetric collapse may contribute significantly to the curve [18]. Once a curve has reached a certain extent of curve degrees, the progression will automatically follow due to the axial Larger curves tend to progress faster than small curves for biomechanical reasons mechanical overload of individual facet joints and/or osteoporotic vertebral bodies. The progression of the curve may well be an indication for surgical treat- ment.Surgeonsneedtobeawareoftheamountofaggravationwhichmayoccur when no surgery is done. The increasing age of patients should be borne in mind along with all the medical consequences which automatically increase the risk of a surgical intervention [25, 26, 29, 31]. Therefore, a surgical intervention may occasionally be indicated in order to avoid further progression and degeneration in a patient with potential medical risks. Physical Findings The clinical examination usually easily demonstrates a patient with a deformed backortrunkoncethecurvehasprogressedbeyondabout35°.Examination with the patient in the standing position may reveal: an oblique pelvis alumbarorthoracichump an unequal shoulder level an asymmetric lumbar triangle loss of lordosis (flatback) lossofsagittalandcoronalbalance The hump is often already visible in the standing position but more so when the patient is bending forward. A counter rib hump is an expression of a primary or compensatory thoracic or thoracolumbar scoliosis. Severely deformed patients may stand with flexed knees to shift their anterior trunk in balance back into a Note sagittal and coronal imbalance position over the center of the pelvis. This out-of-balance position in the sagittal Degenerative Scoliosis Chapter 26 719 plane is due to the lumbar flat back or kyphosis. Usually, patients are still quite mobile in spite of a radiologically relatively stiff curve. The lumbar triangle is usually accentuated on the concave side and flat on the convex side. The side bending as well as flexion and extension of the lumbar curve is usually very lim- ited in progressed curves. Neurological deficits are rare and can vary from some sensory radicular signs to paraparesis due to a complete stenosis of the spinal canal or rarely a multilevel radicular syndrome. Reflex anomalies may occur in isolation or in combination with other neurological deficits. Sometimes the dis- tinct neurological deficit has to be correlated with the target muscles of the spe- cific lumbar roots. Diagnostic Work-up The relevant diagnostic measures in patients with degenerative scoliosis consist of both imaging studies and interventional radiological studies. Laboratory tests are only necessary as a preoperative evaluation for patients planned to undergo surgery. Imaging Studies Very often the whole armentarium of imaging studies is necessary to understand the complexity of a curve and specifically, if present, the concomitant neurologi- cal signs or deficits. Standard Radiographs Full body standing radiographs are indispensable Whole spine X-rays wherethecenteroftheskullandthepelvisarevisibleare necessary in both the frontal and the lateral planes. Spot views predominantly of the lumbar spine are necessary to analyze the affection by the scoliosis in the dif- ferent segments. Oblique radiographs are helpful in exploring facet joint alter- ations and foramina. Functional views including side bending as well as flexion/ extension films are necessary. Functional radiographs are better performed with the patient in the supine position than under axial load. If performed with the patient in the supine position, there is a need for the physician to attend the X-ray capture of the patient. On standard radiographs there may be clues [14, 15] as to whether a scoliosis is truly a primary degenerative scoliosis or rather a secondary Radiographs sometimes exhibit clues to the etiology of the curve (primary vs. secondary) degenerative scoliosis (Fig. 4). It is important to look at earlier radiographs to understand the natural history and therefore the etiology of the curve. The sagit- tal contour of the lumbar spine is important in terms of pain and outcome since curves with a loss of lordosis <25° are usually painful and have a more complex treatment requirement [13]. Magnetic Resonance Imaging Magnetic resonance imaging is the imaging modality of choice to explore neural compromise and disc degeneration. Coronal views are very helpful in assessing neural compromise in relation to the curve. However, degenerative scoliosis is often very polymorphic with MRI due to the complex pathology, parts of which may still be difficult to understand and may leave us uncertain as to what the leading pathology is. For example, deformity may be interpreted on one of the MRI cuts as spinal stenosis since the whole deformity is not in the same plane; however, the patient has no signs of spinal stenosis at all. 720 Section Spinal Deformities and Malformations abcd Figure 4. Primary and secondary degenerative scoliosis a, b Secondary degenerative scoliosis on the basis of an idiopathic scoliosis is usually more strongly expressed, c, d less osteoporotic and longer than a primary degenerative scoliosis . In both end stages there are translational and rotational dislocations of individual vertebrae. Computed Tomography Computed tomogr aphy with or without a myelogram is the diagnostic imaging method of choice in the case of diagnostic uncertainties related to the three- dimensional curve pattern, precise localization of root compressions and their correlation with clinical findings. Interventional Radiological Procedure In the context of the evaluation of the pain source, spinal injection studies (see Chapter 10 ) are especially helpful since their findings may change the therapeu- tic approach [1, 20, 33]. Helpful interventional studies are: provocative discography facet joint blocks nerve root blocks epidural blocks Injection studies are sometimes helpful in identifying the pain source It is important, for instance in lumbar curves, to find out whether the pain occurs within the curve or below the main curve, or whether it usually involves L4/5 and L5/S1, or rarely whether it is above the curve at the thoracolumbar junction. Since the pain can be generated in one or several segments, it is recommended to perform the discograms or the facet blocks sequentially in order to isolate the really painful segment. In addition, discography can be used as a pain provoca- tion test as well as a pain elimination test (i.e., injecting local anesthestic possibly withsomesteroids).Thetestisdoublepositivewhenpainisfirstelicitedduring injection and disappears shortly after the injection. The selective use of epidural blocks at stenotic levels or selective nerve root blocks is another helpful tool to identify the level clinically relevant to the symptomatology on the one hand and as a therapeutic tool on the other hand in case surgery is not feasible or is decided to be delayed. Degenerative Scoliosis Chapter 26 721 Additional Diagnostic Tools A temporary immobilization cast can reveal mechanical back pain If, despite all of these tests, the pain remains unexplained, it may in rare cases be helpful to put on a temporary immobilization cast in the form of a thoracolum- bar orthosis (TLO) or thoracolumbosacral orthosis (TLSO) to see whether an overall stabilization and fusion of the whole scoliotic spinal area could be benefi- cial for the patient, specifically in cases of an overall tendency of the spine to stat- ically collapse. In elderly people with degenerative scoliosis, with plain predominant symp- toms of claudication, leg pain and multilevel stenotic segments in the imaging studies, neurophysiologic studies (see Chapter 12 )maybehelpfultoidentify the level responsible for the clinical presentation. A clear topographic diagnosis would certainly help to minimize the surgery in these patients. Osteodensitometry (DEXA) is indicated whenever there is a suspicion of oste- oporosis because of the implications with regard to curve progression and poten- tial spinal fixation. Non-operative Treatment The indication for or against surgery and, more specifically, the type of surgery to be performed involves complex decision-making [1]. Certainly, surgery is only anoptionwhenthenon-surgicalmeasureshavenoeffectordonothavethepros- pect of any relevant long-term help. The general objectives of treatment derive from the cardinal symptoms of degenerative scoliosis ( Table 2): Table 2. General objectives of treatment relieve pain reverse neurological deficit eliminate spinal claudication prevent curve progression The non-surgical treatment options basically consist of: non-steroid anti-inflammatory drugs (NSAIDs) muscular relaxation pain medication muscle exercises Figure 5. Therapeutic options 722 Section Spinal Deformities and Malformations gentle traction (in selected cases) spinal injection studies orthosis Manipulations should be avoided Manipulations and physical activation should be avoided because they may increase the pain. Therapeutic epidural and selective nerve root blocks as well as facet joint blocks may help to control the pain temporarily. Sometimes, a well-fit- ted brace to support the painful spine area may be necessary [23]. In order to plan the most promising therapeutic approach for each patient, a clear understanding of the prominent symptoms or clinical signs is mandatory. The symptoms and clinical signs can be addressed by various therapeutic treat- ment modalities ( Fig. 5). Operative Tr eatment The decision about treatment approach and type of surgery is complex A surgical approach to degenerative adult scoliosis is obviously complex in terms of decision-making, e.g., ascertaining the surgical indication and choosing the patient and the procedure appropriately. The technical difficulties, however, are equally relevant. The aggravating factors and difficulties with this type of surgery are manifold. Curve magnitude and age of the patient are, for instance, significant predictors of curve flexibility [2, 4, 29, 31]. The understanding of this association allows the treatment options over time to be better addressed. The possible surgical technique can be divided into: posterior procedures anterior procedures combined procedures In all these procedures, a simple decompression or stabilization with pedicle screws [2, 4, 8, 22, 28] can be done alone or in combination. In some cases, addi- tional correction may be considered, either by clearly defined osteotomies or by sequential segmental corrections through instrumentation. This is particularly of interest in combined sagittal/frontal rigid deformities. The goals of the various treatments depending on curve type are summarized in Table 3. Table 3. Surgical treatment options Scoliosis type Decompression Correction Posterior stabilization and fusion Anterior stabiliza- tion and fusion Primary (de novo) degenerative scoli- osis (lumbar, thora- columbar) rarely laminectomy, often necessary by laminotomy, en- largement of lateral recess and foramen not a primary objec- tive (depends on pain pattern and spinal balance) usually posterior stabili- zation and posterolat- eral fusion sufficient. Occasionally selectively combined with PLIF in younger patients. usually not neces- sary Secondary lumbar or thoracolumbar degenerative sco- liosis (idiopathic curves) often necessary in elderly patients with a long-lasting his- tory, not so much in younger patients in younger patients correction possible usually posterior stabili- zation and posterolat- eral fusion sufficient. Occasionally PLIF in younger patients usually not neces- sary. As stand alone procedure possible in youn- ger patients cave thoracic curve: overall balance man- datory Progressing idio- pathic curve in patients younger than 40 years (tho- racolumbar curves) rarely necessary younger patients: cor- rection and balanced spine desired. Com- bined anterior/poste- rior release often nec- essary posterior pedicle fixa- tion posterolateral fusion, pedicle based anterior stand alone surgery at the thoracolum- bar junction pos- sible Degenerative Scoliosis Chapter 26 723 . pathomorphology and pathomechanism [1]. The asymmetric degeneration of the disc and/ or the facet joint leads to an asymmet- ric loading of the spinal segment and consequently of a whole spinal area measurements of the endplate obliquity of L3 in the frontal plane, and of the lumbar lordosis mea- sured between the L1 and S1 superior endplates in the sagittal plane of a standard X-ray. 716 Section Spinal. the increasing narrowing of the spinal canal together with the hypertrophy and calci- fication of the ligamentum flavum and joint capsules, creating central and reces- sal spinal stenosis ( Fig.