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Idiopathic Scoliosis

- Discussion:
    - prevalence of scoliosis:
          - 10 deg curve is considered to be the threshold for scoliosis;
          - curves > 10 deg occur in 2.5/100;
          - curves > 20 deg occur in about 1/2500
          - increased prevalence in females for larger, progressive curves.
          - screening (w/ scoliometer):
                - placed over the spinous process at the apex of the curve;
                - measures the angle of trunk rotation (ATR), which correlates with the severity of the scoliosis;
                - patients are generally referred if the ATR is 5° or more;
    - genetics:
          - women with a scoliotic curve greater than 15 deg have a 27 % prevalence of scoliosis among their daughters;
          - 11 % of first-degree relatives are affected, as are 2.4 and 1.4 percent of second and third-degree relatives;
          - references:
                   - Etiology of idiopathic scoliosis: current trends in research
                   - Validation of DNA-based prognostic testing to predict spinal curve progression in adolescent idiopathic scoliosis.
                   - Adolescent idiopathic scoliosis and genetic testing

- Natural History
    - note that most patients will be unaware of their scoliosis even when curves exceed 30 deg.
    - progression is related to size of curve, area of spine involved, & physiologic age of child;
    - size of curve:
           - larger curves progress to > deg than smaller curves,
           - thoracic and double primary curves progress more than single lumbar or thoracolumbar curves.
    - physiologic age (based on menarche & risser status);
           - Risser stage 0-1: curves between 20-29 deg have > 65% risk of progression;
           - Risser grade 2-4: curves between 20-29 deg have > 20% risk of progression;

- Associated Conditions:
    - treatment of the scoliosis without recognition of syringomyelia and Chiari malformation can lead to paraplegia;
    - it is also important to rule out associated spondylolisthesis since this can complicate surgical planning;

- Exam:
    - examine skin for cafe-au-lait spots (see neurofibromatosis)
    - examine feet for cavovarus deformity
    - height of iliac crests while standing (see: growth deformities of limbs)
    - magnitude of curve and rib humb while standing and leaning forward;
    - asymmetrical shoulder levels;
    - asymmetrical superficial abdominal reflexes;
    - when patient leans forward there may be inequality of lengths of the upper limbs from the floor;

- Radiographs:
    - types of curves:
          - left lumbar curve;
          - double major curve;
          - lumbar scoliosis;
          - thoracic scoliosis;
          - thoracolumbar curve;
    - MRI of the Spine:
          - Do T, et al. determined whether MRI is indicated in adolescents with idiopathic scoliosis who require arthrodesis of spine; 
                 - total of 327 consecutive patients with adolescent idiopathic scoliosis were evaluated between December 1991 and March 1999.
                 - MRI of the brain and the spinal cord were performed as part of their preoperative work-up.
                 - 7 patients had an abnormality noted on magnetic resonance imaging;
                 - abnormalities included a spinal cord syrinx in two patients (0.6%) and an Arnold-Chiari type-I malformation in four (1.2%);
                 - 1 patient had an abnormal fatty infiltration of the tenth thoracic vertebral body.
                 - the authors noted that MRI did not detect any important pathology in the large number of patients;
                 - ref: Clinical value of routine preoperative magnetic resonance imaging in adolescent idiopathic scoliosis. A prospective study of three hundred and twenty-seven patients.  
    - lateral fulcrum bending radiograph:
          - this is a modified type of bending stress AP of the spine;
          - involves placing the patient in the lateral position with a bolster placed underneath the curve apex;
          - the diameter of the bolster should be large enough to keep the shoulder off the table;
          - this view is useful since it helps assess the flexibility of the spine, the levels that need to be included in the fusion,
                  and the expected amount of surgical correction;              
    - structural vs nonstructural curves:
          - it is important to distinguish between the structural curve and the nonstructural curves, inorder to select proper fusion levels;
          - the larger curve is usually the structural curve;
          - the less flexible curve is usually the structural curve;
          - structural curves tend to be displaced away from the midline on the convex side of the curve where as non structural curves tend
                  to be displaced away from the midline on the concave side of the curve;
          - non structural curves usually do not show significant malrotation;
    - measurement technique:
          - in the article by Facanha-Filho FA, et al., 69 curves in 50 patients with congenital scoliosis were
                 measured on two separate occasions by 7 different observers with varying experience in curve measurement;
                 - mean intraobserver variance ranged from 1.9° to 5.0°, with an average of 2.8° (95% CI ±3°) for the seven observers.
                 - interobserver variance was 3.35° (95% confidence limit, 7.86°).
    - ref: Prediction of correction of scoliosis with used of fulcrum bending radiograph.   
          - Measurement Accuracy in Congenital Scoliosis.  

- Indications for Treatment: (based on size of curve and phsiologic maturity) 

Curve Risser Therapy
0 - 25 Immature Observe
25 - 30 Immature Brace
30 - 40 Immature Brace
> 40 Immature Surgery
> 50 Mature Surgery

- Indications for Operative Treatment in Idiopathic Scoliosis:
    - progression of curve > 45-50 deg, since these curves are at higher risk for progression even after completion of growth;
    - high thoracic or cervicothoracic curves:
            - may be of congenital origin;
            - may produce severe deformity;
    - double idiopathic curves > 60 deg at completion of growth;
            - double curves frequently balance one another & may not produce major major cosmetic deformity;
    - note posterior fusion in a physiologically young patient may lead to the crankshaft phenomenon;
    - treatment options: (from King, et al.)

- Complications:
    - low back pain:
           - majority of patients who undergo fusion for scoliosis will experience some low back pain during the first 12 years
                   following surgery;
           - it is controversial whether fusion below L3 causes low back pain;
    - retrolisthesis: may occur caudad to the lowest fusion level;
    - pseudo-arthrosis:
           - most common at the L3-L4 level;
    - superior mesenteric artery syndrome:
           - syndrome which refers to extrinsic compression of third part of the duodenum from the superior mesenteric artery and aorta;
           - this complication has followed Harrington instrumentation and casting, but has occured after spica body casting;
           - symptoms are similar to those of small bowel obstruction but generally respond to NG suction and IV fluids

The Effect of the Risser Stage on Bracing Outcome in Adolescent Idiopathic Scoliosis

Prediction of progression of the curve in girls who have adolescent idiopathic scoliosis of moderate severity.

Delayed infections following posterior spinal instrumentation for the treatment of idiopathic scoliosis.

Superior mesenteric artery syndrome after segmental intstrumentation: a biomechanical analysis

Etiology of Idiopathic Scoliosis: Current Trends in Research    

Spine Behavior Caudal to Instrumentation in King II and IV Curves   

Traction versus side-bending radiographs: is the proximal thoracic curve the stiffer curve in double thoracic curves?

Vertebral Body Stapling Procedure for the Treatment of Scoliosis in the Growing Child.

In Brief: The Risser Classification: A Classic Tool for the Clinician Treating Adolescent Idiopathic Scoliosis