Adolescent Idiopathic Assessment

DefinitionScoliosis Thoracic Major


Lateral curvature of the spine with vertebral rotation

- defined as > 10o coronal plane deformity

- occurs at or near the onset of puberty 

- no cause is established


Planes of Deformity



- coronal / scoliosis

- sagittal / thoracic lordosis

- transverse / rotational


General Categories




Fixed lateral curvature with rotational deformity

- intrinsic anatomical change


1.  Idiopathic 75%

2.  Neuromuscular 10%

3.  Congenital 10%

4.  Other 5%


Non structural


Reversible, non rotational and disappears with sitting

- nil intrinsic anatomical change


Compensatory / Hysterical / Irritative / Postural / Sciatic




< 10o - 2.5 %

> 30o 4 / 1000 

> 40o 1/1000



- little difference overall

- females more likely to have larger curves

- females more likely to progress




Scoliosis Research Society (SRS)


Infantile: 0-3 years onset 


Juvenile: 3-10 (Puberty)


Adolescent: 10 - Cessation of Growth (20 years)




Early Onset - < 5 years 

- rare and severe

- male 2:1

- left sided

- if less than 1, 90% resolve

- >1, 20% resolve

- many other congenital anomalies


Late Onset  - > 5 years

- Adolescent Idiopathic

- females 6:1

- right thoracic

- nil associations

- FHx common




Structural Differences


Intervertebral Disc

- decreased GAG in Nucleus and increased collagen content 


Paravertebral Muscles 

- differences in muscle fibres on either side of curve 

- more type I fibres on the convex side of curve 


Ligaments and Tendons 

- PLL thickened 



- patients with idiopathic scoliosis often taller 

- normal GH but altered Somatomedin levels - ? significance 


Vertebral Body

- structures on concave side hypoplastic 

- structures on convex side hyperplastic

- due to persistent asymmetrical loading


Postural Equilibrium

- abnormality in vestibular system in brainstem 

- scoliosis induced in bipedal rats with destruction of brainstem 

- not conclusive - ? effect rather than cause 




Scoliosis produced when the pineal gland removed from chickens 

-  transmitter found to date - ? melatonin




Increased incidence in affected relatives 


Mother with scoliosis

- 10% chance for female child


Sister with scoliosis

- 20% chance for female child


Mother and father with scoliosis

- 80% chance for female child




Biomechanical initiator of the deformity

- thoracic lordosis normally lies in front of the normal axis of rotation

- causes the lumbar lordotic section to rotate in flexion 

- the tethering of the posterior elements (thickened PLL) also contributes to rotation in flexion

- explains the Crank Shaft Phenomena 


Adolescent Idiopathic Scoliosis 




Prevalence dependant on the size of the curve 


As the curve increases in magnitude the female preponderance increases as well 


Overall is 3.6:1  F:M


Curve Patterns


There are five major curve patterns in decreasing order they are


Right Thoracic

Double major (Thoracic dominant)


Double major (Lumbar dominant)

Left Lumbar 






Absolute increase in Cobb angle of 10o

- or 5o over two consecutive visits 


Remember the interobserver error of Cobb angles is +/- 4o

- can vary with the time of day (increases in the pm)


Factors related to progression




Magnitude:  curve > 20o

Risser:  0 or 1

Sex:  Female

Menarche: premenarche

Age: < 12

Pattern:  Thoracic & double curves most


Growth Remaining



- 66% prior to and 33% after menarche 

- most growth is 1 year before and 1 year after menarche

- have on average 2 years growth left

- have passed PHV



- peak height velocity / most important factor

- adolescent growth spurt

- girls 8 cm / year

- boys 9.5 cm / year

- before menarche / at Risser 0 / open triradiate cartilage

- PHV generally over 2 years


Tanner sign 

I - Pre-pubertal 

II - Breast buds  - related to adolescent growth spurt

III- Pubic hair 

IV- Menarche 


Triradiate cartilage

- may be more sensitive in judging the maturity 

- Risser 0 + open triradiate cartilage indicates a lot of growth to go

- closes in the middle of the PHV


Risser sign 


Risser grade relies on ossification of the iliac apophysis from lateral to medial and is completed with maturity

- Grade 0 to 5 

- Grade 0 means no ossified apophysis present

- Grade 1 means appearance of apophysis laterally / after menarche

- Grade 5 is fusion of the apophyseal cap to ilium / little growth remaining / 14-16 Boys and 11-13 Girls

- can be difficult to distinguish between 0 and 5


Curve Pattern 


Double curves have higher incidence of progression than single curves

- single thoracic > single lumbar

- lumbar the least


Curve Progression Studies


1.  Lowenstein Study of Curve Progression


Looked at Risser sign + intial curve in regards to curve progression


Risser   0 - 1 2 - 5
Initial curve 0 - 19o 22% 2%
Initial curve 19 - 290 66% 22%


2.  Weinstein and Ponsetti 


Looked at the progression after maturity  / 30 year study

- curves less than 30o as rule DO NOT progress after maturity 

- 50 - 75o progressed most ( 1o/ year ) 

- this is the basis for surgery for curves 450 plus


Slowed over 100o with costopelvic impingement 



- mortality 2x expected

- high percentage disability pension

- none in heavy work

- nil increase incidence LBP


Natural History of Untreated Scoliosis


Back Pain 


Most studies suggest that the incidence of back pain is no higher than in general population 


Back pain seen in thoracolumbar or lumbar curves of > 45o

- particularly if large apical rotation or imbalance 


Pulmonary Function 


Affect on pulmonary function not seen until curves of 80o reached  

- restrictive pattern

- linear relationship between FVC and PaO2 and curve size 

- nil effect with curve < 60o

- 1/3 with curve 60-100o

- 1/2 with curve > 100o




Nachemson 1968

- not increased until curve of 100o noted


Cor Pulmonale 


Seen at 40 and 50 years of age if curve > 80o






How detected 

Presence of progression 

Associated complaints 

- pain 

- neurological symptoms 

- respiratory symptoms 


Status of growth 

- growth spurt

- menarche

- changes in puberty 


Want to ensure is idiopathic

- normal delivery / normal milestones

- bladder troubles (NM)

- Marfinoid / OI / NF




See the section on examination for detail


AP Film


Standing AP or PA films of whole spine including the iliac crests 

- PA has less radiation to ovaries and breasts 

- AP has less magnification 


1.  Neutral / end vertebrae


End vertebra is the last vertebra that tilts into the concavity of the curve

- when the end plates are parallel, the one furthest from the apex of the curve is the end vertebra


Scoliosis End Vertebrae


2.  Cobb Angle 


Detect the end vertebrae where the end plates are last to converge 

- line drawn along upper plate of the upper end vertebrae and lower plate of the lower end vertebrae 

- perpendiculars to these lines 

- intersection angle measured 


If double curve

- one vertebrae is upper end vertebrae for the lower curve 

- lower end vertebrae foe the upper curve 


Measurements all taken from same vertebrae in future 


Scoliosis Cobb Angle


3.  Identify Apical Vertebrae


In centre of curve

- furtherest from central sacral line

- not tilted / most horizontal

- maximum rotation


T10 above apical - Thoracic

T11 - L1 apical - Thoracolumbar

L2 down - Lumbar


4.  Stable Vertebrae


Central sacral line

- lowest vertebrae this bisects or

- line between 2 pedicles

- lowest vertebrae instrumented in surgery


Scoliosis Central Sacral Line


5.  Look at shoulders


Important in double thoracic major

- high structural thoracic curve

- if left shoulder high in right thoracic curve

- need to instrument to T2 to correct this


Lateral Films 



- measure the kyphosis and lordosis via Cobb method

- important presurgery

- want to correct this intra-operatively

- usually need to recreate thoracic kyphosis


Lateral Bend Films 


Push prone

- supine with maximal voluntary bend 

- differentiates structural from compensatory curves 




If suspect intraspinal pathology 

- Brain + 3 level spine / neurocentral


Indications for MRI


Scoliosis Left Lumbar Curve


Left sided 



Rapidly progressive 

Neurological abnormality present 




Right sided curve: 20% have pathology 

Left sided curve: 80% have pathology 


Assessment of Rotation 


Rib Hump / Scoliometer 


Adams forward bend test

< 5o tilt = < 30o rotation

> 7o tilt = > 30o rotation


Rotation of Pedicles

- indicates the structural curve






3 areas of curve

- main thoracic: MT

- proximal thoracic: PT

- thoracolumbar / lumbar: TL/L



- curve location

- lumbar modifier

- thoracic sagittal profile


Type 1 Main Thoracic

- MT structural

- PT non structural

- TL/L non structural


Scoliosis Main Thoracic


Type 2 Double Thoracic

- MT and PT structural

- TL/L non structural


Type 3 Double Major

- MT and TL/L structural

- PT non structural


Type 4 Triple Major

- all 3 structural


Type 5 Thoracolumbar / Lumbar

- only TL/L


Scoliosis Lumbar


Type 6

- TL/L and MT structural

- TL > MT by more than 10o


King-Moe  Classification

Very poor inter observer reproducibility


Type I -  Lumbar Dominant Double T + L

- both the thoracic and lumbar curves cross the midline 

- lumbar curve larger and more rigid 


Type II - Thoracic  Dominant Double

- both the thoracic and lumbar curves cross the midline 

- thoracic curve larger and more rigid 


Type III -  Short Thoracic 

- thoracic curve 

- lumbar curve doesn't cross the midline 

- lumbar curve not structural


Type IV - Long thoracic 

- long thoracic curve extends to lumbar spine 

- L5 over the sacrum 

- L4 tilted into the curve (stable vertebrae)


Type V -  Double structural thoracic 

- double thoracic curve with L upper, R lower

- tilting of T1 into the upper curve / elevation of L first rib

- cervical extension

- compensatory lumbar curve with upper curve structural