How Do You Measure All Those Angles?

Patient Presentation
A 14-year-old female came to clinic for her sports physical in August. She said that her friends had noticed her left shoulder being more prominent when she bent over at the pool this summer.
She had no pain, or difficulty moving and no one else had noticed it. She had been screened for scoliosis at school about 18 months earlier.
The past medical history revealed a healthy female with menarche at age 12 and regular periods since age 13.
The family history was negative for musculoskeletal or neurological disorders.
The pertinent physical exam showed a healthy female with growth parameters in the 50-75%. She had full range of motion in her back, shoulders and hips. Her left scapula was slightly more prominent when bending forward and the scoliometer measured 10 degrees.
She was Tanner stage 5 for breast and pubic hair development.
The radiologic evaluation of radiographs of her spine showed a thoracic curve to the right with a Cobb angle of 15 degrees and Risser index of 4. She was referred to orthopaedics because of parental and patient anxiety.
The diagnosis of adolescent idiopathic scoliosis was confirmed and the family was educated that it was less likely that her curve would progress because of the pattern, magnitude, age, menarche status and Risser index.
The patient was to return in 6 months for monitoring.

Alignment of the spine is measured from a plumbline dropped from C7 vertebrae as the line of reference. Lordosis is anterior curving, kyphosis is posterior curving and scoliosis is lateral curving relative to this line.

In 1954 J. James classified idiopathic scoliosis according to the age of the patient at the time of diagnosis: infantile idiopathic scoliosis for patients < 3 years, juvenile idiopathic scoliosis for patients 3-10 years and adolescent idiopathic scoliosis for patients > 10 years.
This system has prognostic significance with juvenile idiopathic scoliosis having a high rate of progression and need for intervention.
The precise etiology of idiopathic scoliosis remains unknown.

Adolescent idiopathic scoliosis is the most common type of idiopathic scoliosis and the most common type of scoliosis overall. By mid- to late- adolescence, 2-3% will have a 10-degree angle or more.
Most patients present because of a perceived deformity usually by the patient or family members. Patients also may be identified through screening by health care providers using the Adams forward bending test. This test has been found to be an effective screening tool when used with a scoliometer. Screening is usually begun in the pre-adolescent age group.

The most common lateral curves are located in the thoracic spine with the curve’s apex to the right. The second most common is a lumbar curve with apex to the left. The third most common is a thoracolumbar curve with the apex to the right. Double curves also happen and the most common is a thoracic curve with apex to the right and lumbar curve with apex to the left.

Risks of progression

  • Curve pattern – double curves progress more than single curves, lumbar curves progress the least
  • Curve magnitude – larger curves are more likely to progress, this is measured by the Cobb angle (see Learning Point below)
  • Age – the younger the patient, the more likely the curve will progress
  • Menarche – curves detected before menarche are more likely to progress
  • Gender – females are more likely to progress
  • Risser sign or index – lower Risser indexes are at greater risk for progression

In general, < 10% of children who screen positively will need intervention. Treatment includes observation, orthosis or bracing and surgical intervention.
Current treatment for adolescent idiopathic scoliosis is based mainly on the curve magnitude. Curves less than 30 degrees are observed, bracing occurs for those 30-40 degrees and surgery for curves that are > 40 degrees.
There are many caveats to these numbers and treatment is individualized particularly if the curve is rapidly progressing or the patient is skeletally immature.

Learning Point
Cobb angle
On the radiograph beginning at the head and moving toward the feet, identify the first vertebral body that is maximally angled or tilted. Draw a line on the top of this vertebral body extending toward the apex of the curve. Again going from the head to the feet, identify the last vertebral body that is maximally angled or tilted and draw a line on the bottom of this vertebral body extending toward the apex of the curve. On each of these two lines, draw a perpendicular line (90 degree line) such that the perpendicular line intersect. The angle between the intersecting perpendicular lines is the Cobb angle.

Figure 42 – Diagram showing the calculation of a Cobb angle in a patient with a thoracic curve with the apex to the right. The Cobb angle measures 43 degrees.

Risser sign or index is the ossification of the epiphysis of the iliac crest. It usually begins on the anterior superior iliac spine and progresses posteriorly. The iliac spine is divided into 4 quarters and the Risser index is designated 1-4 as to where the ossification is occurring and 5 if it is completely fused.

Questions for Further Discussion
1. How is the natural history of congenital scoliosis different than idiopathic scoliosis?
2. How effective are back exercises or electric stimulation for treating idiopathic scoliosis?

Related Cases

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Information prescriptions for patients can be found at MedlinePlus for this topic: Scoliosis
and at Pediatric Common Questions, Quick Answers for this topic: Scoliosis

To view current news articles on this topic check Google News.

James JI: Idiopathic Scoliosis: The Prognosis, Diagnosis, and Operative Indications Related to Curve Patterns and the Age of Onset. J Bone Joint Surg 1954; 36B: 36-49.

Weinstein SL. Adolescent Idiopathic Scoliosis, Prevalence, Natural History and Treatment Indications. Pamphlet from the Scoliosis Research Society and the American Academy of Orthopaedic Surgeons.

Mehlman CT. Idiopathic Scoliosis. eMedicine.
Available from the Internet at (rev. 6/30/2004, cited 11/22/2006).

ACGME Competencies Highlighted by Case

  • Patient Care
    1. When interacting with patients and their families, the health care professional communicates effectively and demonstrates caring and respectful behaviors.
    2. Essential and accurate information about the patients is gathered.
    3. Informed decisions about diagnostic and therapeutic interventions based on patient information and preferences, up-to-date scientific evidence, and clinical judgment is made.
    4. Patient management plans are developed and carried out.
    5. Patients and their families are counseled and educated.
    7. All medical and invasive procedures considered essential for the area of practice are competency performed.
    9. Patient-focused care is provided by working with health care professionals, including those from other disciplines.

  • Medical Knowledge
    10. An investigatory and analytic thinking approach to the clinical situation is demonstrated.
    11. Basic and clinically supportive sciences appropriate to their discipline are known and applied.

  • Practice Based Learning and Improvement
    13. Information about other populations of patients, especially the larger population from which this patient is drawn, is obtained and used.

  • Systems Based Practice
    24. Cost-effective health care and resource allocation that does not compromise quality of care is practiced.

    Donna M. D’Alessandro, MD
    Associate Professor of Pediatrics, Children’s Hospital of Iowa

    December 11, 2006