scoliosis , newly developed in a skeletally mature patient , is termed degenerative scoliosis or de novo scoliosis . prevalence and incidence of degenerative scoliosis increase with age .
an overall increase is seen due to the demographic shift towards an aging society [ 17 , 33 , 39 ] .
generally it is assumed that degenerative scoliosis is caused by asymmetric disc degeneration and facet joint degeneration [ 1 , 3 , 4 , 7 , 27 , 30 , 36 ] and that the onset is marked by disc degeneration [ 17 , 25 ] .
this etiology sets degenerative scoliosis apart from other types of scoliosis , such as adolescent idiopathic scoliosis and scoliosis secondary to neuromuscular disease .
in addition , degenerative scoliosis develops most frequently in the lumbar spine , where degenerative changes are most prevalent , whereas in neuromuscular and idiopathic scoliosis the major curve is usually in the thoracic or thoracolumbar spine .
.   showed that the normal spine has a specific pattern of vertebral rotation , with a predominant rotation to the right at the mid - thoracic level .
most prevalent curve types of adolescent idiopathic scoliosis were found to demonstrate comparable patterns [ 8 , 11 , 12 , 14 , 21 , 23 , 32 , 35 , 40 ] , which correspond to the predominant rotational pattern in the normal spine .
this implies that once the spine starts to decompensate , due to a still unknown cause , it follows this already built - in rotational tendency . in degenerative scoliosis factors causing asymmetrical degeneration and the eventual disruption of the spinal equilibrium
whether a pre - existing rotational pattern also plays a role in degenerative scoliosis is unknown .
an argument against this is that the normal lumbar spine does not show an obvious rotation deviating from the midline .
we hypothesize that spinal decompensation based on degenerative changes is purely coincidental and that left and right curves in lumbar degenerative scoliosis are equally distributed .
however , if the distribution of curve direction is unequal , this may point to a pre - existing rotational tendency that has so far not been demonstrated .
symptoms of degenerative scoliosis are most frequently progressive back pain , radiculopathy and neurogenic claudication [ 1 , 3 , 7 , 9 , 13 , 15 ] . aging progressively affects all structures of the spinal units , eventually leading to degenerative instabilities such as spondylolisthesis , spinal stenosis and scoliosis .
relationships between scoliotic pattern and patient symptoms are unclear , although speculations on such relationships are frequently made [ 1 , 3 , 7 , 30 , 42 ] . some authors suggest that pain at the convexity is caused by muscle fatigue of the paraspinal muscles [ 3 , 30 , 42 ] .
other authors claim that pain at the convexity can also be caused by facet joints .
pain at the concavity of the scoliotic curve is thought to be caused by destruction of facet joints   and degenerative changes in disc spaces .
radicular pain at the concavity can arise from narrowed foramen [ 1 , 3 , 42 ] or ruptured discs causing radiculopathy [ 1 , 3 ] .
dynamic overstretch of a nerve root could also cause radicular pain at the convex side of the scoliosis .
the first objective of this study is to assess whether a dominant direction of compensation exists in degenerative scoliosis .
our second objective is to investigate whether asymmetric symptoms are related to the curve direction , i.e. whether pain and radicular symptoms in degenerative lumbar scoliosis are predominantly present at one side relative to the curve direction .
in this retrospective study we filtered the outpatient records of our institution for patients who presented between 1996 and 2007 and were diagnosed with degenerative scoliosis .
patients aged 50 and over at the initial presentation of degenerative scoliosis and had a scoliosis of at least 10 in the coronal plain were included .
patients were excluded if they had a previous history of idiopathic scoliosis , neuromuscular scoliosis , or scoliosis secondary to an underlying pathology .
the patient records were reviewed in order to obtain patient data about age , gender , length , height , weight , symptoms , physical examination and history .
for each patient , curve direction , apical level , apical vertebra , cobb angle in the coronal plane , and length of the curve were determined .
the apex of the curve was determined in the coronal plane and the apical level was determined .
the apical vertebra was defined according to the scoliosis research society ( srs ) as the vertebra with the greatest distance from the midline with the most rotation . according to the srs classification curves with an apex at the 12th thoracic vertebral body or the first lumbar vertebral body are thoracolumbar curves .
curves with an apex between the first lumbar disc and the fourth lumbar vertebral body are lumbar curves .
the cobb angle is the angle between the two most tilted vertebrae within a scoliotic curve .
the length of the curves was taken as the number of vertebrae between these two most tilted vertebrae .
patient symptoms recorded were low back pain , pain in the buttocks , leg pain , hypo- or hyperesthesia and weakness affecting the legs .
all statistical analyses were performed with spss 15.0 for windows ( spss , inc , chicago , il ) .
the binominal test was used to compare the observed frequencies of right and left curves to an equal distribution .
in addition , it was tested whether curve direction depended on apex level using the chi - square test . whether the observed frequencies of ipsilateral and contralateral pain and/or radicular symptoms relative to the scoliotic curve direction differs from an equal distribution was tested using a binominal test .
all statistical analyses were performed with spss 15.0 for windows ( spss , inc , chicago , il ) . the binominal test was used to compare the observed frequencies of right and left curves to an equal distribution .
the tests were performed for all curves combined and also separately per apical level . in addition , it was tested whether curve direction depended on apex level using the chi - square test . whether the observed frequencies of ipsilateral and contralateral pain and/or radicular symptoms relative to the scoliotic curve direction differs from an equal distribution
the group consisted of 71 women and 17 men with a mean age of 70 ( 70.1    10.3 ; range 5093 ) . of these patients 50
all patients had a single curve in the thoracolumbar range , except one patient who had a double curve .
for this double curve , the curve with the largest cobb angle was considered in the analyses . of the total group , 39 curves ( 44% )
were to the right and 49 ( 56% ) were to the left ( p  =  0.337 ) .
apical levels ranged from the 12th thoracic disc to the 4th lumbar vertebra ( median apex , 2nd lumbar disc ) .
the mean cobb angle was 25 ( 25.4    13.0 ; range 1083 ) .
eighty - three patients had lumbar curves and five patients had thoracolumbar curves according to the srs classification .
fifty - eight percent ( 49 ) of the lumbar curves were convex to the left ( p  =  0.156 ) .
eighty - three percent ( 5 ) of the thoracolumbar curves were convex to the right ( p  =  0.375 ) .
the apical vertebrae of the curves varied from l1 to l4 ( table  1 ) , with l3 the median apical vertebra.table  1the distribution of curve direction for each apical vertebraapical vertebra of curvennumber of curves convex to the rightnumber of curves convex to the leftp ( binominal test)l165 ( 83%)1 ( 17%)0.219l23520 ( 57%)15 ( 43%)0.500l33912 ( 31%)27 ( 69%)0.024*l482 ( 25%)6 ( 75%)0.289the p level indicates whether the distribution deviates significantly from an equal left 
right distribution*statistically significant ( p  <  0.05 ) the distribution of curve direction for each apical vertebra the p level indicates whether the distribution deviates significantly from an equal left 
right distribution * statistically significant ( p  <  0.05 ) left and right distributions were also tested per apical vertebra ( table  1 ) . for apical level l1 an inclination for convexity to the right
eighty percent ( 4 ) of patients with the apex of the curve at l1 had a convexity to the right ( p  =  0.219 ) . in 35
a small majority , 57% ( 20 ) of curves were convex to the right ( p  =  0.500 ) .
curves with an apex at l3 ( n  =  39 ) , however , showed a significant inclination to the left . in this group
69% ( 27 ) had a curve convexity to the left ( p  =  0.024 ) .
also most ( 75% , n  =  6 ) of the curves with the apex at l4 were convex to the left ( p  =  0.289 ) . the curve direction depended significantly on the apical level ( p  =  0.011 ) and on the level of the apical vertebra ( p  =  0.017 ) ( fig .  1 ) .
the direction of the curve depends significantly on the apical vertebra ( chi - square , p  =  0.017 ) . when tested separately per level , the left 
right distribution for curves with an apex at l3 differed significantly from a random distribution ( binominal , p  =  0.024 ) distribution of left and right convex curves per apical vertebra .
the direction of the curve depends significantly on the apical vertebra ( chi - square , p  =  0.017 ) . when tested separately per level , the left 
right distribution for curves with an apex at l3 differed significantly from a random distribution ( binominal , p  =  0.024 ) all patients had low back pain . only four patients ( 5% ) had unilateral back pain .
this was not related to the curve direction , since two patients had pain at the same , and two at the contralateral side of curve convexity .
of these patients 57% ( 41 ) had unilateral leg pain , the others had pain in both legs .
the side at which unilateral radicular leg pain occurred was unrelated to the curve direction ; 21 patients ( 51% ) had symptoms ipsilateral to the curve convexity and 20 ( 49% ) patients contralateral to the scoliotic curve ( p  =  1.000 ) .
seventy - two patients had symptoms of the lower extremities of which 22 had weakness , 1 hyperesthesia , 6 hypoesthesia and 11 showed neurological symptoms during physical examination .
the group consisted of 71 women and 17 men with a mean age of 70 ( 70.1    10.3 ; range 5093 ) . of these patients 50
all patients had a single curve in the thoracolumbar range , except one patient who had a double curve .
for this double curve , the curve with the largest cobb angle was considered in the analyses . of the total group , 39 curves ( 44% )
were to the right and 49 ( 56% ) were to the left ( p  =  0.337 ) .
apical levels ranged from the 12th thoracic disc to the 4th lumbar vertebra ( median apex , 2nd lumbar disc ) .
the mean cobb angle was 25 ( 25.4    13.0 ; range 1083 ) .
eighty - three patients had lumbar curves and five patients had thoracolumbar curves according to the srs classification .
fifty - eight percent ( 49 ) of the lumbar curves were convex to the left ( p  =  0.156 ) .
eighty - three percent ( 5 ) of the thoracolumbar curves were convex to the right ( p  =  0.375 ) .
the apical vertebrae of the curves varied from l1 to l4 ( table  1 ) , with l3 the median apical vertebra.table  1the distribution of curve direction for each apical vertebraapical vertebra of curvennumber of curves convex to the rightnumber of curves convex to the leftp ( binominal test)l165 ( 83%)1 ( 17%)0.219l23520 ( 57%)15 ( 43%)0.500l33912 ( 31%)27 ( 69%)0.024*l482 ( 25%)6 ( 75%)0.289the p level indicates whether the distribution deviates significantly from an equal left 
right distribution*statistically significant ( p  <  0.05 ) the distribution of curve direction for each apical vertebra the p level indicates whether the distribution deviates significantly from an equal left 
right distribution * statistically significant ( p  <  0.05 ) left and right distributions were also tested per apical vertebra ( table  1 ) . for apical level l1 an inclination for convexity to the right
eighty percent ( 4 ) of patients with the apex of the curve at l1 had a convexity to the right ( p  =  0.219 ) . in 35
a small majority , 57% ( 20 ) of curves were convex to the right ( p  =  0.500 ) .
curves with an apex at l3 ( n  =  39 ) , however , showed a significant inclination to the left . in this group
69% ( 27 ) had a curve convexity to the left ( p  =  0.024 ) .
also most ( 75% , n  =  6 ) of the curves with the apex at l4 were convex to the left ( p  =  0.289 ) . the curve direction depended significantly on the apical level ( p  =  0.011 ) and on the level of the apical vertebra ( p  =  0.017 ) ( fig .  1 ) .
the direction of the curve depends significantly on the apical vertebra ( chi - square , p  =  0.017 ) . when tested separately per level , the left 
right distribution for curves with an apex at l3 differed significantly from a random distribution ( binominal , p  =  0.024 ) distribution of left and right convex curves per apical vertebra .
the direction of the curve depends significantly on the apical vertebra ( chi - square , p  =  0.017 ) . when tested separately per level , the left 
right distribution for curves with an apex at l3 differed significantly from a random distribution ( binominal , p  =  0.024 )
all patients had low back pain . only four patients ( 5% ) had unilateral back pain .
this was not related to the curve direction , since two patients had pain at the same , and two at the contralateral side of curve convexity .
of these patients 57% ( 41 ) had unilateral leg pain , the others had pain in both legs .
the side at which unilateral radicular leg pain occurred was unrelated to the curve direction ; 21 patients ( 51% ) had symptoms ipsilateral to the curve convexity and 20 ( 49% ) patients contralateral to the scoliotic curve ( p  =  1.000 ) .
seventy - two patients had symptoms of the lower extremities of which 22 had weakness , 1 hyperesthesia , 6 hypoesthesia and 11 showed neurological symptoms during physical examination .
in this retrospective radiographic study we have assessed the direction of curve decompensation in a group of 88 patients with degenerative lumbar scoliosis .
it was found that curve direction depended significantly on the apical level of the curve .
interestingly , the majority of curves with an apex above l2 were convex to the right , whereas curves with an apex below l2 were more frequently convex to the left . the srs classification does not differentiate in this respect , since the transition from left to right - sided curves falls within the class of lumbar curves .
hence , when looking at all lumbar curves combined , no predominant curve direction is found .
vertebral rotation and lateral deviation of the spine are coupled phenomena , with the rotation of vertebral bodies directed into the convexity of the curve .
it was previously demonstrated that in the normal non - scoliotic spine a predominant left - sided rotation exists in the high thoracic vertebrae , whereas the mid- and lower thoracic vertebrae are predominantly rotated to the right .
this prevalent rotational pattern in the normal spine corresponds with the predominance of right - sided thoracic and thoracolumbar curves in idiopathic and neuromuscular scoliosis [ 19 , 38 ] .
however , in idiopathic and neuromuscular scoliosis often a left - sided compensatory curve is seen at the lumbar level [ 19 , 38 ] .
although in lumbar degenerative scoliosis , the scoliotic curve is essentially at the lumbar level , it apparently does show the same predominant direction as the compensatory lumbar curve in idiopathic or neuromuscular scoliosis .
the strong relationship between apical level and curve direction does indicate that also in degenerative scoliosis the innate curvature of the spine plays a role in the direction of the curve . in this study
we have analyzed curve directions in the coronal plane , although scoliosis is essentially a complex 3d deformation .
nevertheless , a good impression can be obtained from 2d images because lateral deviation is coupled to rotational deviation [ 20 , 38 ] .
in idiopathic scoliosis , it is assumed that biomechanical factors play a role in the development and progression of the curvature .
it is thought that a spine with scoliosis experiences greater loading on the concave side and that this asymmetrical loading causes asymmetrical growth and progression of deformity .
similar processes may play a role in degenerative scoliosis , only in this case , the greater loads at the concave side may induce degenerative changes which could result in a further progression of the scoliosis .
these degenerative changes , however , can be diverse , ranging from degenerative changes in the intervertebral discs to spondylolysis or spondylolisthesis , rotatory dislocations and destruction of facet joints , depending on the  weakest link  .
it is known that disc degeneration temporarily induces segmental instability [ 16 , 24 ] , making the spinal construct more vulnerable to forces that can increase a slight pre - existing rotatory pattern , such as dorsally directed shear loads ( ddsl s ) [ 5 , 18 ] .
the fact that degenerative scoliosis occurs most often in the lumbar spine , where most vertebrae are subject to these ddsl s supports this assumption . in our patient population
, we found that all patients presented with back pain and most patients experienced radicular leg pain .
several possible mechanisms have been put forward to explain the causes of radicular pain in degenerative scoliosis .
radicular pain may result from impingement of the nerve root due to decreased foraminal width or overstretching of the neural elements .
it decreases during extension , ipsilateral lateral side bending , and ipsilateral axial rotation and increases during flexion , contralateral lateral side bending and contralateral axial rotation .
based on this , in scoliosis a decreased foraminal width can be expected at the concavity of the curve .
although this was corroborated in an mri study of ploumis et al . , they found that the foraminal width at the concave side was still within the normal range .
they concluded that ligamentum flavum hypertrophy , posterior disc bulging , and bony overgrowth are more likely to contribute to stenosis irrespective of scoliosis .
this would also explain why in our study radicular leg pain is not related to the direction of the curve .
hence , for a better understanding of the symptoms related to degenerative scoliosis the underlying local deformations should be studied in more detail .
one of the potential effects of severe degeneration is scoliosis . in 88 patients with degenerative lumbar scoliosis we found a significant relationship between curve direction and the apex of the curve .
curves with an apex above l2 were mostly convex to the right , whereas curves with an apex below l2 were more frequently convex to the left .
this indicates that in degenerative scoliosis the innate curvature or rotatory pattern of the spine is an important factor for the direction of spinal decompensation .
although the normal spine does not show a pre - existing rotation at the lumbar level , the asymmetry of the whole spine is presumably directive for the decompensatory changes .
this supports the concept that symptoms are the result of specific degenerative changes irrespective of the scoliotic curve .
 due to the aging population , degenerative scoliosis is a growing clinical problem . 
 it is associated with back pain and radicular symptoms . 
 the pathogenesis of degenerative scoliosis lies in degenerative changes of the spinal structures , such as the intervertebral disc , the facet joints and the vertebrae itself . 
 possibly muscle weakness also plays a role . 
 however , it is not clear what exactly causes the decompensation to occur and what determines the direction of the curve . 
 it is known that in the normal spine a pre - existing rotation exists at the thoracic level , but not at the lumbar level . in this retrospective study 
 we have investigated if a predominant curve pattern can be found in degenerative scoliosis and whether symptoms are predominantly present at one side relative to the curve direction . 
 the lumbar curves of 88 patients with degenerative scoliosis were analyzed and symptoms were recorded . 
 it was found that curve direction depended significantly on the apical level of the curve . 
 the majority of curves with an apex above l2 were convex to the right , whereas curves with an apex below l2 were more frequently convex to the left . 
 this would indicate that also in degenerative scoliosis the innate curvature and rotational pattern of the spine plays a role in the direction of the curve . 
 unilateral symptoms were not coupled to the curve direction . 
 it is believed that the symptoms are related to local and more specific degenerative changes besides the scoliotic curve itself . 
Introduction
Materials and methods
Statistical analysis
Results
Curve patterns
Symptoms
Discussion
Conclusion