General
- Aka: Adolescent idiopathic scoliosis
Numbers
- Most common type of scoliosis
- Incidence of
- 3% for curves between 10 to 20°
- 0.3% for curves > 30°
- Demographics
- most commonly presents in children 10 to 18 yrs
- 10:1 female to male ratio for curves > 30°
- 1:1 male to female ratio for small curves
- Overall, only 6 in 10 000 children will require treatment for LOIS.
- Mortality rate of untreated adult patients with adolescent idiopathic scoliosis is comparable with that of the general population,
Curve direction
- Left thoracic curve most common
- Right thoracic curves are rare and indicate an MRI to rule out cyst or syrinx
- Syrinx
- 25-85% pt with Syrinx has scoliosis
- Surgical treatment (spinal distraction and instrumentation) of scoliosis without recognition of syringomyelia can result in increased neurological complications.
- Small curves are more common than large curves.
Clinical features
- Small curves do not present clinically.
- School screening programmes
- Abandoned
- As there is no reliable treatment that we can offer to children with small curves that would alter the natural history of the curve.
- Patients often referred from school screening where a 7° curve on scoliometer during Adams forward bending test is considered abnormal.
- 7° correlates with 20° coronal plane curve.
- The development of a late onset curve is an insidious process.
- It is unsurprising that small curves go unnoticed by parents.
- Back pain
- The incidence of back pain is no higher than the general population,
- But when painful episodes do occur, they may be a little more severe and last a little longer than the average.
- Unexplained back pain in this group should prompt a search for other possible causes, especially pathologies that cause painful scoliosis such as osteoid osteoma or spondylolysis.
- Cosmesis
- Psychological
- Body image issues → psychological
- Girls with LOIS have a higher incidence of
- Eating disorders
- Lower BMI
- Cardiopulmonary compromise
- LOIS does not cause significant problems unless the curve is very large.
- A curve size of 90° is often quoted as a threshold for such compromise,
- In contrast, severe pulmonary dysfunction is much more common in EOIS.
- The important distinction is where pulmonary dysfunction becomes clinically significant.
- Some degree of measurable pulmonary dysfunction may be seen across all curve sizes.
- A curve of >50° may have symptoms of exertional dyspnoea.
Aetiology of late onset idiopathic scoliosis
- Unknown Pathophysiology
- The deformity is lordosis with scoliosis, or lordo-scoliosis.
- The rotation of the curve as the spine deforms may give the appearance of kyphosis on the standard lateral radiograph, but a de-rotated view will give a more accurate assessment.
- Theories
- One theory is that excess anterior spinal growth relative to posterior growth reduces the stability of the thoracic kyphosis, which then buckles, to produce a scoliosis.
- Potential causes (Multifactorial)
- Hormonal (melatonin)
- Brain stem
- Proprioception disorder
- Platelet
- Calmodulin
- Abnormal development of neurocentral synchondrosis (NCS)
- Cartilaginous plate that forms between the centrum and posterior neural arches
- Closure occurs in characteristic order
- Cervical NCS by 5-6 years old
- Lumbar NCS by 11-12 years old
- Thoracic NCS by 14-17 years old
- Most have a positive family history
- Between 8% and 20% of patients with LOIS will have a first degree relative with the condition.
- No identified gene yet
- More common in tall and slim (exomorphic) females.
Curve progression
Curve Progression in Idiopathic Scoliosis
- General:
- Overall Progression:
- 68 per cent of all curves progressed
- Definition of Progression: More than 5 degrees increase in the Cobb angle
- The average curve increased by 13.4 degrees (from 50.3 to 63.7 degrees) for all types of curves over a 40 year period
- Prognosticating curve progression
- By skeletal maturity
- Indicators of remaining spinal growth (Lonstein 1984)
- Chronological age
- Age alone is a crude guide
- Endocrine
- Age of menarche adds further information.
- Girls grow rapidly for 18 months before and 18 months after menarche.
- Skeletal markers of maturity
- For LOIS before skeletal maturity
- Grade 5 patients will have no open growth plates in the long bones
- > 25° before skeletal maturity will continue to progress
- After skeletal maturity
- > 50° thoracic curve will progress 1-2° / year
- > 40° lumbar curve will progress 1-2° / year
- By curve magnitude
- Curves < 30 Degrees
- at skeletal maturity:
- Tended not to progress, regardless of curve pattern.
- Exceptions included one lumbar curve with an unseated L5 and significant apical vertebral rotation, which progressed.
- L5 was considered "well seated" if the intercrest line passed through the L4/5 disc space or lay above that level
- Before skeletal maturity
- Even with significant remaining growth, small curves are unlikely to progress.
- Data for curves of 5– 19° shows that (Note that a curve of 5° is below the current accepted threshold (10°) for a diagnosis of scoliosis.)
- 22% progress if the child is Risser grade 0–1
- 1.6% progress if the child is Risser grade 2–4
- Curves between 50 and 75 degrees
- At skeletal maturity
- Showed the most significant progression.
- Thoracic curves in this range progressed an average of 29.4 degrees, nearly 1 degree per year.
- There is long term data to suggest that all curves progress a little, even after skeletal maturity.
- This progression is approximately 0.5° per year on average.
- Progression is more rapid in larger curves (>50°).
- A number of LOIS patients will again present to spinal surgeons as adults with progression and degeneration in the curve, with symptoms of pain and possibly nerve root compression. (See Adult scoliosis )
- By Curve Type:
- Thoracic Curves:
- Cobb angle, apical vertebral rotation, and Mehta angle were important prognostic factors.
- Non progressive curves
- Curves less than 30 degrees
- minimal rotation (<20%)
- Minimal Mehta angle (<20 degrees).
- Progressive curves (1 degree per year over the 40 year period) had the following characteristics
- Curves greater than 50 degrees
- Significant apical rotation (>30%)
- Significant Mehta angle (>20 degrees, often 30-60 degrees).
- Lumbar Curves:
- Progressive curves
- Right lumbar curves progressed
- twice as much as left lumbar curves (22.3 degrees vs. 11.6 degrees).
- All lumbar curves greater than 30 degrees had apical vertebral rotation exceeding 33 per cent progressed
- Except
- If lumbar curves (>30 degrees) but with either a sacralized or a well-seated L5, and did not exhibit translatory shifts.
- Translatory shifts (aka lateral slippage)
- particularly at L3-L4 or L4-L5, often accompanied by lateral tilting if L5 was not well seated.
- Non-progressing curves
- Thoracolumbar Curves:
- Marked apical vertebral rotation (40-65%) + translatory shifts led to significant progression.
- Combined (Double Primary) Curves:
- Lumbar components progressed slightly more than thoracic components (average 23.1 degrees vs. 18.3 degrees).
- The ratio of thoracic to lumbar components decreased over time, reflecting greater progression in the lumbar component.
- Apical vertebral rotation, Mehta angle, and the relationship of L5 to the intercrest line did not correlate with progression in combined curves.
- Translatory shifts were often observed at the transition between the two components.
- Double curves more likely to progress than single curve.
Risk Factor | Risk of Progression (> 5°) |
Age <10 | 88% |
Age >15 | 29% |
Premenarche | 53% |
Postmenarche | 11% |
Risser grade 0 | 68% |
Risser grade 3–4 | 18% |
- Biochemical changes in the intervertebral disc
- Changes include decreased proteoglycan aggregates and monomers in end-plates, decreased proteoglycan/glycoprotein and increased collagen content in the nucleus pulposus.
- These alterations, similar to those seen in osteoarthritic joints, may compromise the structural stability of the spine, making it more susceptible to biomechanical influences that lead to curve progression.
Radiological assessment
Scoliosis is a curve in the coronal plane of >10 degrees.
- Intra-interobserver error of 3-5°
- In EOIS if Cobb angle > 20 degrees associated with progression
Measurements specific for EOIS
- Fulcrum Bending Radiograph (FBR)
- Purpose:
- The FBR was developed to assess the flexibility of the thoracic spine,
- identify any structural changes,
- Determine the selection of fusion levels in AIS patients.
- Fulcrum-Bending flexibility (%) = (Preoperative Angle – Fulcrum Bending Angle) / Preoperative Angle × 100
- Fulcrum Bending Correction Index (FBCI)
- Purpose:
- A preferred method to assess the correction rate because it takes into account the curve’s flexibility.
- It helps compare curve correction and instrumentation systems between different patient series.
- Fulcrum Bending Correction Index (%) (FBCI) = Correction Rate / Fulcrum-Bending Flexibility × 100
- Correction rate (%) = (Preoperative Angle – Postoperative Angle) / Preoperative Angle × 100
- An FBCI close to 100% suggests that the instrumentation has fully utilised the flexibility revealed by the FBR.
- Rib phase
- technique
- convex rib head position with respect to the apical vertebrae
- findings
- phase 1 - no rib overlap
- is associated with resolution in 84– 98% of cases.
- phase 2 - rib overlap with the apical vertebrae
- Associated with progression in 84– 97% of cases.
- high risk for curve progression
- RVAD (rib vertebrae angle difference, Mehta angle)
- Technique
- measure angle between the endplate and rib (line between midpoint of rib head and neck)
- RVAD = difference of 2 rib-vertebral angles
- Findings
- > 20° is linked to high rate of progression
- < 20° is associated with spontaneous recovery
Lenke classification
Treatment
Major Curve | Management |
<20° | Observation |
20-29° | - If Risser 0-1, premenarchal: Immediate bracing - If Risser 2: brace if progresses by 5° during observation |
30-40° | Brace if skeletally immature |
>40° | - If skeletally immature and failed bracing, offer surgery - If skeletally mature, wait till >50° before surgery |
Conservative
- In the long term, LOIS patients have a normal life expectancy.
- Physiotherapy
- can be helpful for those children who develop back pain.
- No good evidence that physiotherapy can alter the curve progression.
- Bracing
- Indication
- Cobb angle from 25° to 45°
- only effective for flexible deformity in skeletally immature patient (Risser 0, 1, 2)
- Aim
- Goal is to stop progression, not to correct deformity
- Cons
- Has potentially significant physical and psychological morbidity.
- Types
- CTLSO (Milwaukee brace, most efficacious for curve apex above T8)
- TLSO (e.g. Boston brace; curves with an apex at T8 or below; better tolerated)
- bending brace and flexible brace.
- Contraindications
- Skeletal maturity
- Curves > 40°
- Thoracic lordosis (worsens cardiopulmonary restriction)
- not tolerating bracing
- Outcomes
- 50% reduction in need for surgery with compliant brace wear of at least 13 hours a day
- poor prognosis with brace treatment associated with
- Poor in-brace correction
- Hypokyphosis (relative contraindication)
- Male
- Obese
- Noncompliant (effectiveness is dose-related)
- NNT is 4 in highly compliant patients
- Sanders staging system
- Predicts the risk of curve progression despite bracing to >50 degrees in Lenke type I and III curves
- Uses anteroposterior hand radiograph and curve magnitude to assess risk of progression despite bracing
- Technique
- Recommended for 16-23 hours/day until skeletal maturity or surgical intervention deemed necessary (actual wear minimum 12 hours required to slow progression)
- Brace types
- Curves with apex above T7
- Milwaukee brace (cervicothoracolumbosacral orthosis)
- Extends to neck for apex above T7
- Apex at T7 or below
- TLSO
- Boston-style brace (under arm)
- Charleston Bending brace is a curved night brace
- Bracing success is defined as <5° curve progression
- Bracing failure is defined
- 6° or more curve progression at orthotic discontinuation (skeletal maturity)
- Absolute progression to >45° either before or at skeletal maturity, or discontinuation in favour of surgery
Made with Bullet