The Cobb angle is a measurement of bending disorders of the vertebral column such as

scoliosis Scoliosis is a condition in which a person's spine has a sideways curve. The curve is usually "S"- or "C"-shaped over three dimensions. In some, the degree of curve is stable, while in others, it increases over time. Mild scoliosis does not t ...

and traumatic deformities.

Definition and method

It is defined as the greatest angle at a particular region of the vertebral column, when measured from the superior

endplate The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic i ...

of a superior vertebra to the inferior endplate of an inferior vertebra. However, the endplates are generally parallel for each vertebra, so not all sources include usage of a superior versus inferior endplate in the definition. Unless otherwise specified it is generally presumed to refer to angles in the coronal plane, such as projectional radiography in posteroanterior view. In contrast, a ''sagittal Cobb angle'' is one measured in the sagittal plane such as on lateral radiographs. Cobb angles are preferably measured while standing, since laying down decreases Cobb angles by around 7–10°.

Uses

It is a common measurement of

. The Cobb angle is also the preferred method of measuring post-traumatic kyphosis in a recent meta-analysis of traumatic spine fracture classifications.

Severity

Those with Cobb angle of more than 60° usually have respiratory complications.

Scoliosis Scoliosis is a condition in which a person's spine has a sideways curve. The curve is usually "S"- or "C"-shaped over three dimensions. In some, the degree of curve is stable, while in others, it increases over time. Mild scoliosis does not t ...

cases with Cobb angles between 40 and 50 degrees at skeletal maturity progress at an average of 10 to 15 degrees during a normal lifetime. Cobb angles of more than 50 degrees at skeletal maturity progress at about 1 to 2 degrees per year.

History

The Cobb angle is named after the American orthopedic surgeon John Robert Cobb (1903–1967), was originally used to measure coronal plane deformity on radiographs with antero- posterior projection for the classification of

.Cobb JR. Outline for the study of scoliosis. The American Academy of Orthopedic Surgeons Instructional Course Lectures. Vol. 5. Ann Arbor, MI: Edwards; 1948. It has subsequently been adapted to classify sagittal plane deformity, especially in the setting of traumatic thoracolumbar spine fractures.

References

{{Reflist Musculoskeletal radiographic signs