Max Aebi The adult scoliosis

Received: 26 October 2005Accepted: 26 October 2005Published online: 18 November 2005� Springer-Verlag 2005

Abstract Adult scoliosis is defined asa spinal deformity in a skeletallymature patient with a Cobb angle ofmore than 10� in the coronal plain.Adult scoliosis can be separated intofour major groups: Type 1: Primarydegenerative scoliosis, mostly on thebasis of a disc and/or facet jointarthritis, affecting those structuresasymmetrically with predominantlyback pain symptoms, often accom-panied either by signs of spinal ste-nosis (central as well as lateralstenosis) or without. These curvesare often classified as ‘‘de novo’’scoliosis. Type 2: Idiopathic adoles-cent scoliosis of the thoracic and/orlumbar spine which progresses inadult life and is usually combinedwith secondary degeneration and/orimbalance. Some patients had eitherno surgical treatment or a surgicalcorrection and fusion in adolescencein either the thoracic or thoracol-umbar spine. Those patients maydevelop secondary degeneration andprogression of the adjacent curve; inthis case those curves belong to thetype 3a.Type 3: Secondary adultcurves: (a) In the context of an ob-lique pelvis, for instance, due to a leglength discrepancy or hip pathologyor as a secondary curve in idio-pathic, neuromuscular and congeni-tal scoliosis, or asymmetricalanomalies at the lumbosacral junc-tion; (b) In the context of a meta-bolic bone disease (mostlyosteoporosis) combined with asym-

metric arthritic disease and/or ver-tebral fractures. Sometimes it isdifficult to decide, what exactly theprimary cause of the curve was, onceit has significantly progressed.However, once an asymmetric loador degeneration occurs, the patho-morphology and pathomechanism inadult scoliosis predominantly lo-cated in the lumbar or thoracolum-bar spine is quite predictable.Asymmetric degeneration leads toincreased asymmetric load andtherefore to a progression of thedegeneration and deformity, as ei-ther scoliosis and/or kyphosis. Theprogression of a curve is furthersupported by osteoporosis, particu-larly in post-menopausal female pa-tients. The destruction of facetjoints, joint capsules, discs and liga-ments may create mono- or multi-segmental instability and finallyspinal stenosis. These patients pres-ent themselves predominantly withback pain, then leg pain and clau-dication symptoms, rarely withneurological deficit, and almostnever with questions related to cos-metics. The diagnostic evaluationincludes static and dynamic imaging,myelo-CT, as well as invasive diag-nostic procedures like discograms,facet blocks, epidural and rootblocks and immobilization tests.These tests may correlate with theclinical and the pathomorphologicalfindings and may also offer the leastinvasive and most rational treatment

Eur Spine J (2005) 14: 925–948DOI 10.1007/s00586-005-1053-9 REVIEW

M. AebiInstitute for Evaluative Research inOrthopaedic Surgery, University of Bern,Bern, Switzerland

M. AebiDepartment of Orthopaedics,Hirslanden-Salem Hospital,Stauffacherstrasse 78, 3014 Bern,SwitzerlandE-mail: max.aebi@MEMcenter.unibe.chTel.: +41-31-6315930Fax: +41-31-6315931

source: https://doi.org/10.7892/boris.118072 | downloaded: 4.1.2020

Introduction

Twenty-five years ago, a book chapter about scoliosiswith special emphasis on the adult and/or degenerativescoliosis was relatively small [5, 11, 20, 43, 53, 62, 64].Most of the pages were devoted to scoliosis in childhoodand adolescence. Only the introduction of spinal instru-mentation, first Harrington rods and Dwyer instrumen-tation, and later Zielke, and finally CD-instrumentationwith all the following third generation pedicle instru-mentations, shifted the focus to the major problem of theadult scoliosis [1, 2, 8, 13, 23, 27, 32, 35, 38, 40, 45, 58, 59,62]. This disorder has been known for some time, but onlya very few surgeons dealt with it. Patients were in an agegroup which was considered to be too risky to undergomajor spine surgery; the surgical technical issues werewidely unsolved due to the lack of powerful instrumen-tation; the bone stockwas considered toopoor for amajorcorrective surgery; and the patients were generally madeto believe that they had to live with this ailment.

Progress in surgical techniques and technology issignificantly supported by progress in anaesthesia forspinal surgery and by more sophisticated and precisediagnostic imaging and differentiated application ofinvasive and functional diagnostic tests. Increased pa-tient awareness, the patient’s unwillingness to accepttheir limitations and pains [54], and the gradual shift inthe demographics towards a ‘‘grey society’’, make adultscoliosis with all of its different forms and clinical pre-sentations, a much more frequent problem in a generalspine practice than the scoliosis of children and adoles-cents. This trend is likely to continue when we considerthe fact that in 25 years from now, a significant part(more than 10%) of the population in the industrializedsocieties will be over 65 years old.

Classification

A scoliosis is diagnosed in adult patients when it occursor becomes relevant after skeletal maturity with a Cobbangle of more than 10� in the frontal plain [1, 55].

Type 1: Primary degenerative scoliosis (‘‘de novo’’ form),mostly located in the thoracolumbar or lumbar spine [6,19, 20 24, 25 27, 33, 43, 48, 52, 53].Type 2: Progressive idiopathic scoliosis in adult life ofthe thoracic, thoracolumbar, and/or lumbar spine [5, 8,36, 42, 46, 61, 71, 72].Type 3: Secondary degenerative scoliosis.

(a) Scoliosis following idiopathic or other forms ofscoliosis or occurring in the context of a pelvicobliquity due to a leg length discrepancy, hippathology or a lumbosacral transitional anomaly,mostly located in the thoracolumbar, lumbar orlumbosacral spine [11, 24, 34, 44, 50, 64].

(b) Scoliosis secondary to metabolic bone disease(mostly osteoporosis) combined with asymmetricarthritic disease and/or vertebral fractures [10, 15,29, 51, 70].

Therefore, scoliosis can be present since childhood oradolescence and become progressive and/or symptomaticin adult life; or scoliosis may appear ‘‘de novo’’ in adultlife without any precedence in earlier life.

Clinically, the most prominent groups are secondary(type 3) and primary (type 1) degenerative adultscoliosis. In elderly patients, both forms of scoliosis maybe aggravated by osteoporosis, which also holds true forthe type 2 scoliosis [24, 29, 70]. All three types ofscoliosis may primarily appear at a certain stage asdegenerative scoliosis, and degenerative scoliosis is

for the patient. The treatment is thentailored to the specific symptom-atology of the patient. Surgicalmanagement consists of eitherdecompression, correction, stabil-ization and fusion procedures or acombination of all of these. Surgicalprocedure is usually complex andhas to deal with a whole array ofspecific problems like the age andthe general medical condition of thepatient, the length of the fusion, thecondition of the adjacent segments,the condition of the lumbosacraljunction, osteoporosis and possiblyprevious scoliosis surgery, and last

but not least, usually with a longhistory of chronified back pain andmuscle imbalance which may be verydifficult to be influenced. Althoughthis surgery is demanding, the mor-bidity cannot be considered signifi-cantly higher than in otherestablished orthopaedic procedures,like hip replacement, in the same agegroup of patients. Overall, a satis-factory outcome can be expected inwell-differentiated indications andproperly tailored surgical proce-dures, although until today pro-spective, controlled studies withoutcome measures and pre- and

post-operative patient’s health statusare lacking. As patients, who presentthemselves with significant clinicalproblems in the context of adultscoliosis, get older, minimal invasiveprocedures to address exactly themost relevant clinical problem maybecome more and more important,basically ignoring the overall defor-mity and degeneration of the spine.

Keywords Adult scoliosis Æ Degen-erative scoliosis Æ Spinal steno-sis Æ Adult deformity Æ Secondaryscoliosis

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therefore the main bulk of adult scoliosis. Beyond theproposed classification, the degenerative adult scoliosiscould also be subdivided into scoliosis which have theiraetiology in the spine itself and those scoliosis with theaetiology beyond the spine (Table 1). Schwab et al.proposed recently a radiographic classification includingtype I–III scoliosis, characterized by the a/p and lateralview in standing position. They correlated the classifi-cation I–III with increasing severity of self-reported painand disability [55]. Boachie-Adjei [8] considers specifi-cally the idiopathic adult scoliosis (our type 2 scoliosis)and uses the age as a classifying criteria combined withdegenerated changes: patients with idiopathic adultscoliosis below and above 40 years of age.

This review will concentrate on the forms of adultscoliosis which present themselves most frequently in aspinal practice and which are considered in the above-presented classification.

Type 1 scoliosis: the primary degenerative scoliosis(‘‘de novo’’ scoliosis) (Fig. 1)

The primary degenerative curve develops mostly on thegrounds of primarily limited disc degeneration in one or

more motion segments. This curve also could be termed‘‘discogenic curve’’ and is basically the result of anasymmetric degenerative change of the disc with theconsecutive development of a frontal deviation andconcomitant rotation with the facet joints on one side asa pivot (Fig. 1). The apex of this curve is usually be-tween L3 and L4 or L2 and L3 or, second most frequent,between L1 and L2. These curves tend to go along with asignificant rotational translation of the apical vertebra.In some cases the primary cause of the degenerativeprocess may be localized in the facet joints where a widevariety of dystrophic formation, malformation, andmisalignment can occur. When this occurs at the lum-bosacral junction, then the curve belongs rather to thetype 3a curves, following lumbosacral anomalies.

It is difficult to state whether some curves in this groupcould be considered as ‘‘resting’’ idiopathic scoliosis.There are obviously curves that only develop in adult lifeand may appear like idiopathic scoliotic curves; however,upon closer look, they rather may have developed on thebasis of a degenerated disc. The primarily degenerativecurves usually are less severe in terms of frontal angulationthan the curves in secondary degenerative idiopathic sco-liosis [24, 25]. The primary degenerative scoliosis istherefore mostly a lumbar or thoracolumbar curve con-sisting of a frontal as well as a sagittal deviation in the

Table 1 Potential of curve progression

Type Description Etiology Problem locatedin the spinebeyond the spine

Type I Primary degenerative scoliosis(‘‘de novo’’ scoliosis)mostly lumbaror thoracolumbar curveapex at L2/3 or L/4 mostfrequently

Asymmetric discdegeneration and facetjoint degeneration

+

Type II Progressive idiopathicscoliosis of thelumbar and/orthoracolumbar spine(e.g. double major curve)

Idiopathic scoliosis presentsince adolescence orchildhood, progressiondue to mechanicalreasons or bony and/ordegenerative changes

+ ?

Type III (a) Secondary adult scoliosismostly thoracolumbar,lumbar-umbosacral

Secondary to an adjacentthoracic or thoracolumbarcurve of idiopathic,neuromuscular orcongenital originObliquity of the pelvis dueto leg length discrepancyor hip pathology withsecondary lumbar/thoracolumbar curveLumbosacral transitional anomaly

+ +

Type III (b) Deformity progressingmostly due to boneweakness with, e.g.,osteoporotic fracture withsecondary deformity

Metabolic bone disease, osteoporosis + +

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form of mostly a flat back or lumbar kyphosis [5, 6, 8, 19,23, 31, 36]. The sagittal malalignment is usually respon-sible for the severe postural back pain of the patients.These curves are shorter than the idiopathic curves an-d—at least in the beginning—the deformity of the indi-vidual vertebral body is less expressed than in idiopathicscoliosis [24, 25]. This only occurs as a consequence oferosion and destruction of the endplates and facet jointsdue to spondylosis and spondylarthritis. Also, there is adifference in the bone density between the primary andsecondary degenerative curves. Spinal stenosis is moreoften seen in primary degenerative scoliosis than in sec-ondary degenerated idiopathic curves [2, 6, 8, 21, 26, 44].The disc degeneration ends up with spondylosis, discbulging, osteophytes, and facet joint arthritis with hyper-trophic capsules, ligamentum flavum, and calcification ofthese structures with osteophytes, all on the costs of thespace in the spinal canal and foramina, thus contributingto the formation of spinal stenosis, be it a foraminal lateralstenosis or a central stenosis or both (Fig. 2).

Type 2 scoliosis: progressive idiopathic scoliosisin adult life (Fig. 3)

The idiopathic curves and curves with other aetiologyof secondary degeneration present themselves in avariety of forms, depending on whether these curveshave been treated non-surgically or not at all orwhether they have had a fusion, with or withoutinstrumentation, of the main thoracic and thoracol-umbar curve [46]. In the latter case the degenerationappears in the adjacent curve and belongs to the type

3a curves (see below) (Figs. 3, 4). In both situations,however, there may be a significant degeneration anddeformity present in the sagittal as well as in thefrontal plain of the short lumbar curve. The sagittaldeformity is almost always exclusively a flat backsyndrome or a loss of physiological lordosis and inextreme situations a real kyphosis. The degeneratedidiopathic scoliosis mostly in the lumbar and/or tho-racolumbar spine is quite frequently combined withspinal stenosis at a relatively young age, specifically inthe adjacent lower segment after Harrington instru-mentation. This adjacent segmental spinal stenosis,mostly below a long fused idiopathic scoliosis, appearsabout 15–20 years post-surgical with Harrington rods(Fig. 5). There are not yet similar long-term resultsavailable for cases which have been treated with oneof the CD-type third generation instrumentation thatallow superior restoration of the sagittal alignment,possibly protecting the spine from developing rapidadjacent segment degeneration [3, 4, 7, 21, 39, 56].

Type 3 scoliosis:

Secondary degenerative scoliosis (Fig. 6)

Adult secondary degenerative scoliosis is mostly locatedin the thoracolumbar and lumbar as well as lumbosacralspine. This scoliosis occurs either with its cause withinthe spine or outside the spine. Those scoliosis with thecause inside of the spine are either secondary to anadjacent curve, be it an idiopathic, neuromuscular orcongenital curve, or it may be the consequence of a

Fig. 1 Type 1 adult scoliosis: denovo scoliosis. a at 33 years(8�), b at 50 years (25�), c at55 years (40�)

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lumbosacral anomaly, specifically with a hemisacraliza-tion (Fig. 6). Scoliosis outside of the spine is due topelvic obliquity in the context of a hip pathology or a leglength discrepancy (Fig. 7). These secondary curves withthe causes outside of the spine primarily do not have arelevant rotation, however are basically deviations in thefrontal plain. Only over time there is a translationaldisplacement of vertebras close to the apex.

Adult scoliosis due to bone weakness (Fig. 8)

These deformities are mostly due to metabolic bone dis-ease or diseases which have a secondary impact on thestrength of the bone (e.g. Morbus Adison) (Fig. 8). Themost frequent cause for a secondary deformity due tometabolic bone disease is osteoporosis. Owing to boneweakness, there may be fractures, which create an asym-metric configuration with expression of either kyphosis orscoliosis or both together. It may also occur when a pre-existing scoliosis, respectively kyphosis, is aggravated byan osteoporotic fracture [29, 65, 70].

Pathomorphology and pathomechanism in adultscoliosis

Degenerative adult scoliosis, specifically in the lumbarspine, is characterized by quite a uniform pathomor-

phology and pathomechanism. The asymmetric degen-eration of the disc and/or the facet joints leads to anasymmetric loading of the spinal segment and conse-quently of a whole spinal area. This again leads to anasymmetric deformity, for example, scoliosis and/orkyphosis. Such a deformity again triggers asymmetricdegeneration and induces asymmetric loading, creatinga vicious circle (Fig. 9) and enhancing curve progres-sion. On the one hand, the curve progression is givenby the pathomechanism of an adult degenerative curve,and on the other hand by the specific bone metabolismof the post-menopause female patients with a certaindegree of osteoporosis, who are most frequently af-fected by the degenerative form of scoliosis. The po-tential of individual asymmetric deformation andcollapse in the weak osteoporotic vertebra is clearlyincreased and contributes further to the curve pro-gression.

The destruction of discs, facet joints and jointcapsules usually ends in some form of uni- or multi-segmental sagittal and/or frontal latent or obviousinstability. There may be not only a spondylolisthesis,meaning a slip in the sagittal plain, but also transla-tional dislocations in the frontal plain or rather three-dimensionally when expressing itself in a rotationaldislocation (Figs. 1, 3, 6, 15). The biological reactionto an unstable joint or, in the case of the spine, anunstable segment, is the formation of osteophytes atthe facet joints (spondylarthritis) and at the vertebralendplates (spondylosis), both contributing to theincreasing narrowing of the spinal canal together with

Fig. 2 Secondary changes in degenerative scoliosis: facet jointhypertrophy, recessal stenosis

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the hypertrophy and calcification of the ligamentumflavum and joint capsules, creating central and recessalspinal stenosis [66] (see also Fig. 2). These patho-morphological and pathomechanical relationships andtheir significance for the clinical presentation of an

adult degenerative scoliosis are expressed schematicallyin Fig. 10. The osteophytes of the facet joints and thespondylotic osteophytes, however, may not sufficientlystabilize a diseased spinal segment; such a conditionleads to a dynamic, mostly foraminal stenosis withradicular pain or claudication type pain (e.g. Fig. 11).

Clinical presentation

Pain

The most frequent clinical problem of adult scoliosis isback pain [3, 6, 19, 31, 56, 73] and presents itself with

Fig. 3 Young female teacher with progressive idiopathic scoliosis.a At 35 years, 62�, b at 38 years progressed to 75�, c left bendingwith some correction, d significant lumbar kyphosis, e partialcorrection by extension, f flexion of thoracic spine, g andh 18 months postoperatively after (1) anterior LISS release andfusion with beta-TCP (Chronos�) autologous bone mixture and(2) posterior correction and stabilization and fusion with USSduring the same anaesthesia. Restoration of the lordosis

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a multiform mosaic of symptoms. Back pain at thesite of the curve can be localized either at the apex orin its concavity, and facet joint pain can be localizedin the countercurve from below the curve to above thecurve. The back pain can be combined with radicularleg pain. It can be the expression of a muscular fati-gue or of a real mechanical instability. Unbalanced,overloaded, and stressed, paravertebral back musclesmay become very sore and in return will not con-tribute to balance the muscle play, consequentlybecoming part of a vicious circle. This is especiallytrue when the lumbar curve is accompanied by theloss of lumbar lordosis [22]. This muscular pain israther diffuse, distributed over the lower back, andoften permanent at the insertion of the muscle tendonsat the iliac crest, sacrum, os coccys, and bony pro-cesses of the spine.

The back pain can be constant and non-specific,which is a bad prognostic sign regarding the treatmentoutcome. The pain, however, can be present only whenthe patient is upright, especially when standing andsitting, presenting as a so-called axial back pain, oronly during certain movements or physical activities,pointing rather to a mechanically unstable segment or awhole spinal region. The patients often indicate thatthey can control their pain well, when lying down flator on their side and when the axial load is taken off thespine.

Claudication

The second important symptom of adult degenerativescoliosis is radicular pain and claudication symptomswhen standing or walking [57, 73]. The patient canhave true radicular pain due to a localized compressionor root traction (root compromise is not necessarily onthe concave side where we may suppose narrowedforamens, but often on the convex side, ratherexpressing a dynamic overstretch of a root). Theremay, however, be a single- or multilevel spinal stenosiswhich can be central or more recessal, creating clau-dication symptoms [19, 24, 27, 53, 56]. Root com-

Fig. 4 a and b Double major idiopathic scoliosis in a 41-year-oldfemale patient with increasing back pain in the last few years andsubjective progression of the curve. c Long fusion to the sacrumwith development of a non-union and loss of balance after a yearpostoperatively. d Osteotomy at L2/3, cut of the rod andcorrection of the malposition by reconnecting the right cut rodand PLIF at the lumbosacral junction. Now with good balanceand almost no pain

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pressions can occur at the bottom of the curve or at thetransition to the sacrum and can be linked to a hy-permobility of an overloaded bottom segment, espe-cially in cases of stiff curves. Short lumbosacral orlumbar curves as countercurves to long fused thora-columbar scoliosis often show a severe spinal stenosisat the transition from the stiff upper spinal area to thelower lumbosacral area (Fig. 11).

Neurological deficit

The third important clinical presentation may manifestitself as a real neurological deficit, including individualroots, several roots, or the whole cauda equina withapparent bladder and rectal sphincter problems. Anobjective neurological deficit, however, is rare and,when present, is due to a significantly compromisedspace in the spinal canal with a relatively acuteaggravation and decompensation (Fig. 12). A sequesterof a severely degenerated and dried out disc within thecurve may be the cause of such an acute neurologicaldeficit (Fig. 13). It can be accentuated or only becomeclinically relevant due to a latent or obvious segmentalinstability.

Curve progression

The fourth relevant symptom or sign is curve progres-sion. Curve progression may be an issue from the mo-ment the curve occurs in younger age. It may, however,only become relevant, when the curve has reached acertain amount of degrees and/or when osteoporoticasymmetric collapse may contribute relevantly to thecurve. Once a curve has reached a certain extent of curvedegrees, the progression will automatically follow due tothe axial mechanical overload of individual facet jointsand/or osteoporotic vertebral bodies. The progression ofthe curve may well be an indication for a surgicaltreatment. The surgeons have to be aware of the amountof aggravation which may occur, when nothing surgi-cally is done. Patients do get older with all the medicalconsequences, which raise automatically the risk for asurgical intervention. Therefore, a surgical interventionmay occasionally be indicated in order to avoid a further

progression and degeneration in a patient with potentialmedical risks [3, 4. 7].

Cosmesis

In contrast to the adolescent idiopathic scoliosis, cos-mesis almost never plays a role; patients see theorthopaedic surgeon because of a simple or morecomplex pain syndrome and/or neurological deficit.Cosmesis may occasionally play a role in youngerpatients below 40 years with an early secondarydegenerated idiopathic thoracolumbar or lumbarscoliosis.

Diagnostic evaluations

In addition to the standard clinical examination, pa-tients with symptomatic adult scoliosis need preciseconventional imaging and often require interventionalradiological procedures, such as sequential discograms,facet blocks, epidural blocks and preferentially, a mye-logram combined with a CT scan [24, 25, 34, 36, 57]. Aspiral CT is very useful in rapid reconstruction of thespine vertically and, in conjunction with the myelogram,obtaining a clear understanding of the pathology. MRimaging of degenerative scoliosis is often very poly-morphic due to the complex pathology, parts of whichmay still be difficult to understand and may leave usuncertain as to the leading pathology. For example,deformity may be interpreted on one of the MR-cuts asspinal stenosis, since the whole deformity is not in thesame plain.

In the context of the evaluation of the pain source,discograms and facet blocks are especially helpful sincetheir findings may change the therapeutic approach. Itis important, e.g., in lumbar curves, to find out whetherthe pain occurs within the curve, below the main curve(usually involving L4/5 and/or L5/S1), or rarely, abovethe curve at the thoracolumbar junction. Since the paincan be generated in one or several segments, it is rec-ommended to perform the discograms sequentially inorder to isolate the really painful segment. In addition,the discogram can be used as a provocative pain test,as well as a form of local anaesthesia in the disc,usually combined with some cortisone injection.Therefore, the discogram serves to provide both directpain provocation and localization and as a double testfor pain evaluation, when the pain disappears after theintradiscal depot of medication. Facet blocks shouldalso be performed sequentially to catch the mostprobable pain generator level.

If, despite all these tests, the pain remains unex-plained, it may be helpful in rare cases to put on a

Fig. 5 a and b A 28-year-old female patient 15 years after Harring-ton correction and fusion to L5. Flat back, spinal stenosis at L5/S1and disconnection of the rod off the hook seating on the arch of L5(arrow). c and d Decompression and attempt to correct in L4/5 andL5/S1, refusion with pedicle screws and anterior cage at L5/S1.Remaining flat back and consecutive back pain. e and f Three yearsafter rebalancing the spine by posterior wedge osteotomy atL3/4 andrestabilization and fusion 4 years after second surgery. Back painalmost entirely disappeared

b

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temporary cast in the form of a thoracolumbar orthosis(TLO) or thoracolumbosacral orthosis (TLSO) to seewhether an overall stabilization and fusion of the wholescoliotic spinal area could be beneficial for the patient,specifically in cases of an overall tendency of the spine tostatically collapse.

In elderly people with degenerative scoliosis display-ing predominant symptoms of claudication, leg pain,and multilevel stenotic segments in the imaging, motorevoked potentials (MEP) may be helpful to identify thelevel responsible for the clinical presentation. A cleartopographic diagnosis would certainly help to minimizethe surgery in these patients.

The selective use of epidural blocks at stenotic levelsor selective nerve root blocks is another helpful tool toidentify the level clinically relevant to the symptom-atology on the one side and as a therapeutic tool on theother side, in case surgery is not feasible or is decided tobe delayed [67].

Therapeutic decision (Fig. 14)

The indication for or against surgery and, morespecifically, the type of surgery to be performed, in-volves complex decision-making. Certainly, surgery isonly an option when the non-surgical measures haveno effect or do not promise any relevant long-termhelp.

The non-surgical treatment options [9, 20, 34, 46, 67]consist basically of non-steroid anti-inflammatory med-ication, muscle relaxants, pain medication, muscleexercises, swimming and occasionally gentle traction,while avoiding manipulations and physical activationthat may increase the pain. Therapeutic epidural andselective nerve root blocks as well as facet joint blocksmay help to control the pain temporarily. Sometimes awell-fitted brace to support the painful spine area maybe necessary.

In order to plan the most promising surgical proce-dure for each patient, a clear understanding of theprominent symptoms or clinical signs is mandatory. Thesymptoms and clinical signs, which can be addressedsurgically, either individually or in concert are repre-sented in Table 2 (see also Fig. 10).

The specific surgical answer to each of these signs orsymptoms may vary depending on whether they occurindividually or in the context of another. The surgicaldecision is also influenced by the patient’s generalhealth, age, condition of bone quality, and the patient’sexpectations [3, 15].

Fig. 6 Type 3a scoliosis in a 25-year-old female patient. Arrows (1)transitional anomaly; (2) spondylolysis L5. *Plomb line from thecentre of the head

b

Fig. 7 Secondary degenerative scoliosis due to a hip arthrodesis fora posttraumatic damage of the left hip: left convex, longthoracolumbar curve with secondary rotational deformity

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The surgical concept involves three basic procedureswhich can be performed separately or together,depending on the patient’s overall symptomatology.

Surgical procedures

A surgical approach to degenerative adult scoliosis isobviously complex in terms of decision making, i.e.,ascertaining the surgical indication and choosing thepatient and the procedure appropriately. The technicaldifficulties, however, are equally elaborated. Theaggravating factors and difficulties for this type of

surgery are manifold. Curve magnitude and age of thepatients are, e.g., significant predictors of curve flexi-bility. The understanding of this association allows tobetter address treatment options over time [14].

The possible surgical technique can be divided inposterior, anterior or combined procedures. In all theseprocedures a simple decompression or stabilization canbe done, or both can be combined [2, 9, 16, 32, 38, 41,56, 68, 69]. In some cases, additional correction may beconsidered, either by clearly defined osteotomies or bysequential segmental correction through instrumenta-tion. This is particularly of interest in combined sagittal–frontal rigid deformities.

Decompression procedures

Decompression may be done as a stand-alone procedurein cases of central or lateral stenosis and symptomatol-

Fig. 8 Adult scoliosis in a 55-year-old male patient with M.Addison: osteoporose, flat back and spinal stenosis. Decompres-sion, stabilization and correction in the frontal plane, distraction,but not reestablishing lordosis. However, 2 years postoperatively,patient had no relevant back pain

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ogy limited to the legs, without relevant back pain, ortogether with instrumentation and fusion in cases ofadditional obvious instability, segmental dysfunction, orprogressive deformity. Stand-alone decompression pro-cedures in deformities are rarely indicated, although itmay be attractive, particularly in elderly frail people. Thedecision exactly when a decompression alone is possible,is difficult to make, since a definite judgement about thedegree of stability or instability is sometimes not possibleon objective, scientific grounds alone. In clinical practiceone learns regularly that the judgement was wrong and

the chosen procedure not sufficient. It is easier sometimesto add a limited fusion and stabilization in the samesession than to go back to do a second surgery in theseoften medically unstable patients (Fig. 11). The outcomeis frequently complicated by either further collapse of thecurve, or by segmental instability, with symptoms ofcontinuous back and/or leg pain, mostly when in anupright position with axial loading of the spine, andasymptomatic when lying down and resting. If decom-pression is performed at the apex of the degenerativecurve, progression of the curve is very likely. This meansthat decompression contributes to destabilization of afragile balance. This procedure can be detrimental andcompletely disable a patient (Fig. 15).

The same may be true when an isolated decompres-sion is done at the bottom of a rigid curve, i.e., at thetransition to the mobile part of the lumbar spine, usuallyL4/5 or L5/S1. The rigid curve above may decompensatethese segments in translation, and the spine may fall offthe balance. In most of these cases, therefore, adecompression should be accompanied by a fusion withor without stabilization in situ (Fig. 11).

In younger patients, in whom a partial correction isplanned, a decompression may be achieved by the cor-rection procedure alone, and a formal decompressionmay not be necessary (Figs. 4, 5, 6).

Correction procedures

If the balance in the frontal plane is achieved and there is aproper sagittal alignment, there is no need to look for acorrection. Stabilization and fusion in situ may be more

Fig. 9 Pathomechanism of adult degenerative scoliosis as a‘‘vicious circle’’

Fig. 10 Pathophysiology ofadult, degenerative scoliosiswith its clinical presentation

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than appropriate in which case overall decompensation ofthe spine can usually then be avoided. Often it is temptingto correct the lumbar curve and/or thoracolumbardeformity since this is almost always possible when arigorous posterior release and pedicular fixation is done.

In cases where the lumbar and/or thoracolumbarcurve is a degenerated countercurve to an idiopathicthoracic curve which is either completely rigid or hasbeen fused in adolescence, a correction needs to becarefully thought about, since the thoracic curve cannotadapt to the corrected curve below, resulting in adecompensation of the thoracic spine, imbalance, and achronic pain syndrome in the lower thoracic or thora-columbar spine (Fig. 16).

In cases of apparent flat back syndrome (primarydegenerative lumbar scoliosis are usually combined witha loss of lumbar lordosis), correction is mostly necessaryif the chronic back pain should be addressed. This needsan extensive release of the posterior elements (facets,facet joint capsules, ligamentous components, andsometimes facet joint osteotomies), and mostly theanterior elements (disc calcified, posterior longitudinalligament calcified). If necessary, the disc can be released

through the same posterior approach at L2 and below.An anterior release is indeed rarely needed, unless thereis a relevantly rigid scoliosis component present withtranslational dislocations, or significant anterior osteo-phytes bridging the segments solidly, where an anteriorrelease may help to balance the frontal and sagittal plane(Fig. 17). Such a combined procedure, however, maynot be well tolerated by more elderly patients over60 years or in reduced general health. Selective seg-mental spinal osteotomies, mostly transpedicularreduction osteotomies, may be necessary to balance thespine.

In addition to the important release in the case of aplanned correction, it may also be necessary to extendthe fixation and fusion beyond the major curve into thethoracic countercurve, to guarantee appropriate sagittalas well as frontal overall balance of the spine. If that isnot considered, the patient may end up with a collapseof the cranial segment adjacent to the fixation, or with asecondary instability both most probably due to anoverloaded segment in an unbalanced correction. It isclear that such a magnitude of surgery is only possible inpatients with a robust general condition, since the sur-gery may take several hours and the blood loss may besignificant. For these reasons, we recommend that sur-gery is considered as early as possible, when unfavour-able developments and progression can be foreseen. Thisis a particularly important consideration in female pa-tients entering menopause who regularly have back and/

Fig. 11 A 79-year-old female patient, known to have scoliosis sincelate twenties. Persistent L5 radiculopathy after selective foraminaldecompression 4 years ago. Now again decompression on the leftwith a local stabilization and fusion in order to prevent progressionof the curve. Disappearance of the radiculopathy

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or leg pain with beginning osteoporosis and significantdegeneration and tendency of flat back.

If an anterior release is necessary, the surgery can bestaged or done in the same surgical session. Anteriorinstrumentation in patients who need a secondary pos-terior procedure is not necessary or even contraindi-cated, since the anterior instrumentation may limitposterior correction. The posterior pedicular systemsnowadays allow a powerful manipulation, correction,and stabilization of the lumbar spine, as long as a properposterior release precedes the corrective and stabiliza-tion procedure. The anteriorly released segments, how-ever, may be prepared for anterior interbody fusion byremoving the disc, freshening the endplates and fillingthe intervertebral space with cancellous bone or even asolid tricortical spacer.

The correction of a deformity is therefore achievedafter an appropriate release either by stepwise correctionthrough segmental instrumentation or by one or moresegmental osteotomies for the frontal or sagittalrealignment of the spine.

In case a lumbar curve is still flexible, which can beassessed by sidebending and flexion/extension views, anda certain compensation of the thoracic countercurve canbe anticipated, a posterior correction, stabilization andfusion with or without decompression are sufficient. Thisis also done when a curve is clearly progressive.

Stabilization and fusion procedures

If back pain is a leading symptom, with or without legpain, a fusion is usually indicated. The levels to beincluded in the fusion can be difficult to determine.Generally speaking, it is unfavourable to stop a fusionat L1 or even L2, i.e., below the thoracolumbar junc-tion, because it may easily lead to decompensationabove the fusion, with localized disc degeneration,segmental collapse, translational instability and sec-ondary kyphosis [28].

The most critical segment to consider whether or notto include in a fusion is the lumbosacral junction. Ittakes all the movement off of the lumbar spine and is themost difficult fusion to be achieved. A high percentagemay remain with a non-union due to the unfavourablemechanical conditions of this junction between the twomajor lever arms of the fused spine and the rigid pelvis[8, 12, 17, 26, 30, 37, 57, 68]. The incidence of the non-union varies quite remarkably in the literature (5–30%)[12, 18]. Various types of instrumentation have beendesigned to enhance the fusion healing to the sacrum [12,30, 37, 60]. They are mostly based on an increasinglymore solid anchorage in the sacrum, or in the sacrumand iliac wings at the same time. None of these instru-mentations have been clinically demonstrated to signif-icantly overcome the problem of non-union in thecomplex pathology of degenerative scoliosis. The mostcertain approach to eliminate the problem of non-unionis a 360� circumferential fusion at the lumbosacraljunction. In order to avoid the anterior approach, unless

Fig. 12 A 75-year-old actress with subacute paraparesis, norelevant back pain: decompression, stabilization, and fusion insitu. Almost complete recovery

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needed for an extensive release, the refinement andstandardization of posterior lumbar interbody fusion(PLIF) technique using specifically designed cages hasbecome a well-controlled procedure (Fig. 18). Con-trolled clinical studies need to show whether the clinicalreality will support the theoretically valid concept ofload sharing at the lumbosacral junction in order toavoid non-unions.

Obviously, it would be preferable to omit the lum-bosacral junction during the surgery for lumbar scoliosiscorrection and stabilization. However, depending on thecause of the curve, the lumbosacral junction usually isdegenerated: disc space narrowing, facet joint arthritis,vertebral obliquity and possibly rotational deformityand sometimes even spontaneous fusion of L5 to S1might be a consequence of a lumbosacral transitionalanomaly or a progressed degeneration. In such cases, if

there is no certainty about the rigidity of L5/S1 it isbetter to include it in the fusion/stabilization since a stopof the fusion at L5 puts a lot of stress on the lumbosacraljunction and is able to ‘‘loosen’’ it up with a secondarypain syndrome. A fusion to L5 even in case of a ‘‘heal-thy’’ L5/S1 segment may overload that and induce asecondary degeneration with loss of disc height, facetjoint incongruency and arthritis and possibly disc her-niation (Fig. 19) [31, 37, 56, 63].

A fusion to the sacrum may not only have an impacton the iliosacral joints but also on the hip joints specif-ically when there is already osteoarthritis of the hip. Thedisease process may be accelerated by the change of theload to the hip joint.

For posterior surgery, pedicular and/or translaminarscrew fixation may be considered [2, 4, 7, 40, 41]. In casecorrection is not the goal of the surgery, but towardsstabilization and immobilization, respectively, of thearthritic, often hypertrophic facet joints, then thetranslaminar screw fixation may be a simple, littletraumatic and minimally invasive procedure to achievesuch a goal (Fig. 20). For a long fixation and correction,a pedicular system is the indication of choice.

Fig. 13 A 79-year-old hard-working male farmer with relativelymild back pain, however, severe left leg pain, corresponding L3 (4)root, with proven root compression: Microsurgical decompressiononly, no attempt to touch the severely degenerated kyphoscolioticspine

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Problems encountered in case of surgical treatment

Length of fusion

It is increasingly understood today that the fusionshould be avoided whenever possible. Unfortunately, upto now, we do not have better established treatmentmodalities available in severely degenerated and de-formed spines. Therefore in severe adult degenerativescoliosis cases, the fusion is an integral part of a treat-ment plan. It is anticipated that within the lumbar spine,every segment should be spared if possible, in order notjust to maintain some lumbar movement but also tospare further segments from degenerating. Discographyand facet joint infiltrations as well as temporary immo-bilization in a body cast may help to determine the ex-tent of the fusion. The radiologically moderatelydegenerated motion segment is not enough to be in-cluded in the fusion, as long as this segment does not

really contribute to the pain suffered by the patient. It is,however, necessary to inform the patient that thisconcept of restricting the extent of the fusion maynecessitate further surgery in case a spared segment maydegenerate further and become symptomatic. The mostproblem segments to be included in a fusion are thosebelow a curve in the lower lumbar spine.

Whether the emerging dynamic fixation devices oreven disc arthroplasty will be an option in the surgicaltreatment of adult degenerated scoliosis remains to beconsidered as more experience is acquired with that kindof implant.

Inclusion of the lumbosacral segment

Patients with a lumbar or thoracolumbar curve have atleast some degree of degeneration at L4/5 and/or L5/S1segments. Although these segments may not be painful

Fig. 14 Treatment options

Table 2 Symptoms and clinicalsigns to be addressed bysurgical measures

1. Back pain: identified as discogenic, facet or instability pain,or pain due to an unbalancedspine in the sagittal(flat back or hypolordosis) and frontal planes

2. Radicular pain: identified by a clear pathomorphological equivalent,providing a compression or tension of one or more roots

3. Claudication symptoms: due to either a central stenosis of one or several levels,or due to a more lateral, recessal stenosis presentingas an individual root claudication

4. Neurologic deficit: ranging from sensory deficits, reflex absence or anomaly,radicular motor deficit, or paraparesis with bladderand sphincter problems

5. Clearly progressive curve

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at the time of the decision-making, they may soon be-come painful after a long-distance fusion has been per-formed above them. A rapid deterioration is thenpossible, which may necessitate a further extension ofthe fusion down to the sacrum. The expert’s opinion isdivided, whether in such cases a lumbosacral fusionshould be included right from the beginning, or whethera wait and see attitude should be taken and only fuse thelumbosacral junction in case there are significant clinicalproblems from this area [8, 10, 12, 15, 30, 37].

Spinal segments adjacent to the fusion/level of fixation

A long fusion, which is often necessary in scoliosis, actsas a lever arm against the adjacent segments above andbelow. If the spine above (in adult lumbar scoliosismostly the thoracic spine or the thoracolumbar junction)is rigid, either physiologically developed over the years,or acquired by a previous fusion of a thoracic curve, itmay not follow the correction executed in the lumbarspine. This may result in a decompensation above thelumbar curve with an unbalanced overall spine, whichmay be the cause of further clinical problems. It istherefore crucial to understand through preoperativeplanning on whole spine X-rays as to how far a cor-rection can be carried out without creating a secondaryproblem in the spine above (see also Fig. 16).

Many mid-lumbar and thoracolumbar curves have ashort and sharp countercurve at the lumbosacral junc-tion either including S1 and L5 only or also L4 with anoblique take off. This short curve is usually seen in the

pelvis and leads to an overload of L3/4 or L4/5 [37].These curves usually do not compensate a correctedcurve above and have a bad prognosis [34, 37]. Theymay even progress and contribute significantly to theclinical syndrome of the patient. In most cases, it istherefore recommended to consider inclusion of thislumbosacral junction into the fusion.

Previous scoliosis surgery

More than 25 years after Harrington instrumentationbecame increasingly popular for idiopathic scoliosissurgery, we see a growing number of patients who hadsuch a surgery in their adolescence. These patients,who are now between their late twenties and earlyforties, are sometimes presenting themselves with se-vere secondary problems below their thoracolumbarfusion and fixation. This problem is particularly severein patients who were left with a flat lumbar spinebecause of the distractive-kyphotic effect of the Har-rington instrumentation in the sagittal plain (Fig. 5).They may have degenerated adjacent segments below,along with spinal stenosis, and chronic low back paindue to the overstressed paraspinal muscles [23, 69].These problems are not unique to patients who hadHarrington instrumentation. They can also be foundin patients who had non-instrumented fusions withlong-term body cast immobilization, or who had notbeen treated at all for a relevant thoracolumbar idio-pathic scoliosis.

In the majority of cases, a simple correction,decompression, and instrumented fusion does not rem-edy the problem. These patients need a complete overallrebalancing of the spine by one or multiple osteotomies.This problem is so complex and multifactorial that itneeds consideration in a separate review and can only bealluded to in this article.

Fig. 15 A 76-year-old female patient with back pain and claudi-cation symptoms in both legs. aWhen patient presented herself to aneurosurgical service, a decompression of the stenosis close to theapex of the curve was done. b 8 months later, progression of thecurve, significant claudication symptoms, severe back pain andpatient practically bedridden

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Age and general medical condition of the patient

The age of the patient—most of the patients withscoliosis and significant, symptomatic degenerativealterations of the curve or counter curve, are older than50 years and often have systemic diseases such as car-diac or vascular disease or diabetes, and are verydemanding for the responsible anaesthesiologist whomust also consider the possible aggravating significantblood loss and surgical time in this procedure. The peri-and post-operative management of such a patient mayneed an interdisciplinary approach among the surgeon,the anaesthesiologist, and an internist who accompanythis patient, until his/her general condition post-opera-tively has stabilized and returned to the pre-operativesituation. Also, the elderly and frail patients need alonger and more intensive rehabilitation time in order torecover optimally [49].

Osteoporosis

Osteoporosis is a major concern in the treatment ofadult scoliosis. The majority of elderly patients withdegenerative scoliosis are female, and osteoporosis maybecome an issue at the time of the menopause. This isthe time when degenerative scoliosis may becomeincreasingly symptomatic because the curve may pro-gress due to the asymptomatic load on weakened ver-tebrae, which get more wedged and deformed. With theprogression of the curve, the patient may get moresymptomatic in terms of back pain as well as of theclaudication pain.

The surgical treatment is complicated by the weakbone where implants are more difficult to be anchoredand fixed, making the instrumented fusion prone toinstrumentation-related complications. The industryhas offered all kinds of instrumentations with bigdiameter screws and adapted threads to improve bonepurchase. Cement reinforcement of the screw anchor-age is another alternative which has been advocated [8,37]. In our experience, instrumentation success is notreally so dependent on the size of the screw. Thewhole construct must respect a principle of balance as

Fig. 16 A 54-year-old female patient who has been fused in lateadolescence for a idiopathic right convex thoracic curve (uninstr-umented fusion); a secondary lumbar curve with degenerativechanges, b instrumented correction and fusion with decompensa-tion of balance because of the rigidity of the thoracic curve due tothe fusion and secondary back pain in the mid- and lower thoracicspinal area

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demonstrated in the Asian world where bamboo isused in the construction of gigantic buildings. Eachanchorage is loaded one against the other in an overall

construct, creating some sort of elastic stability. Thisconcept may be considered in spine stabilization aswell.

Outcome and complications

Complications may result from indication and mis-judgement of the case, non-suitable patients, wrongtechnical performance, implant failure, a lack ofachieving balance in the sagittal and frontal planes, andcomplications which cannot necessarily be explained [3,4, 15, 17, 21, 26, 47].

Fig. 17 a A 71-year-old male physician with severe degenerativescoliosis and with spinal stenosis and flat back. b Decompressionand posterior stabilization, however, correction of the lumbarkyphosis absent, because no anterior release was done and theposterior release was also insufficient. Postoperatively no claudi-cation symptoms anymore, however, persistent back pain

Fig. 18 Type 2 scoliosis (progressive idiopathic scoliosis in adultlife): A 39-year-old female patient with AIS, significant loss oflumbar lordosis preoperatively. Postoperative restoration of lor-dosis and circumferential fusion with PLIF at the lumbosacraljunction in order to avoid non-union

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We have performed more than 250 surgeries in adultscoliosis, and the complication rate has improved sincewe did a retrospective study almost 10 years ago on ourfirst 75 adult scoliosis cases. In the first series, thecomplication rate was comparable to those in otherstudies and the overall results were satisfactory [56, 59,61, 63]. With the present expertise in this field and thereferral of increasingly complex cases, the complicationshave shifted. The most prominent problems weencounter in this surgery are problems of proper balanceand non-union at the lumbosacral junction, as well aslimitations of the surgical options in medically frail pa-tients, resulting in only partial improvement. The non-union problem has lost its significance in the last 3 yearssince we systematically do circumferential fusions at thelumbosacral junction, using either PLIF or ALIF cagesin combination with posterior pedicular instrumenta-tion.

There is a quite substantial risk for mild or severepost-operative nerve root paresis [47]; some of themrecover spontaneously.

The outcome needs to be age matched since the de-mands of daily life, professional performance, and lei-sure activities vary substantially in the different age

groups. Most of the patients who are still professionallyactive do not return to their previous work if it was aphysically demanding job, but almost all of those hadalready stopped working before the surgery, because ofpain limitations. When analyzed, regarding their overalldaily activity by different questionnaires [50], most ofthese patients irrespective of age have improved in al-most all categories of quality of life, and the use ofregular pain medication is reduced substantially in morethan 70% of these patients. The assumption that thissurgery may be too much for elderly patients could notbe substantiated, at least not in our institution, where wehave done a comparative study of general complicationsin an age and comorbidity matched cohort of patientsundergoing hip arthroplasty surgery—an accepted sur-gery in elderly patients—and patients undergoing amajor spine surgery like degenerative lumbar scoliosissurgery [49]. The major problem of these patients aftersurgery, once surgical complications and implant fail-ures have not occurred, is the residual back pain mostlyas an expression of muscular spasms and pain due tounbalanced or chronic contractures of the paravertebralmuscles.

Conclusion

The complexity of the relationship between clinicalsigns, symptoms, pathomorphology, and pathophysi-ology of adult—mostly lumbar, degenerative scolio-

Fig. 19 a A 61-year-old female patient with back pain andclaudication symptoms. b Decompression, stabilization and fusion,while omitting L5/S1; 1 year postoperatively disc space L5/S1 stillquite high, c 28 months postoperatively, collapsed disc space L5/S1with L5 radicular syndrome due to foraminal stenosis

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sis—remains one of the big challenges in spinal sur-gery. The combination of the relatively uniform majorsigns and symptoms, namely instability, stenosis,

unbalanced deformity, and possible curve progressionon one side, and the complex pain pattern, the clau-dication, and possible neurological signs and symp-toms on the other side allow a variety of clinicalpatterns, which need to be analysed both, systemati-cally and individually in order to find concrete solu-tions for each of them, and to tailor a surgicalprocedure which best serves the rational expectationsof the patient and surgeon.

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