The Cobb angle is a measurement of bending disorders of the

vertebral column The vertebral column, also known as the backbone or spine, is part of the axial skeleton. The vertebral column is the defining characteristic of a vertebrate in which the notochord (a flexible rod of uniform composition) found in all chordata, ...

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 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 ...

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 The coronal plane (also known as the frontal plane) is an anatomical plane that divides the body into dorsal and ventral sections. It is perpendicular to the sagittal and transverse planes. Details The coronal plane is an example of a longitud ...

, such as

projectional radiography Projectional radiography, also known as conventional radiography, is a form of radiography and medical imaging that produces two-dimensional images by x-ray radiation. The image acquisition is generally performed by radiographers, and the images ...

in posteroanterior view. In contrast, a ''sagittal Cobb angle'' is one measured in the

sagittal plane The sagittal plane (; also known as the longitudinal plane) is an anatomical plane that divides the body into right and left sections. It is perpendicular to the transverse and coronal planes. The plane may be in the center of the body and divid ...

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 Kyphosis is an abnormally excessive convex curvature of the spine as it occurs in the thoracic and sacral regions. Abnormal inward concave ''lordotic'' curving of the cervical and lumbar regions of the spine is called lordosis. It can result fr ...

in a recent

meta-analysis A meta-analysis is a statistical analysis that combines the results of multiple scientific studies. Meta-analyses can be performed when there are multiple scientific studies addressing the same question, with each individual study reporting me ...

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 John Robert Cobb (1903–1967), was an American orthopedic surgeon, best known for inventing the Cobb angle, the preferred method of measuring the degree of scoliosis and post-traumatic kyphosis. Education Born and raised in Brooklyn, New Yor ...

(1903–1967), was originally used to measure

deformity on

radiographs Radiography is an imaging technique using X-rays, gamma rays, or similar ionizing radiation and non-ionizing radiation to view the internal form of an object. Applications of radiography include medical radiography ("diagnostic" and "therapeut ...

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