Rib vertebral angle measurement and its significance was brought in by Dr Mehta. Measurement of this angle has an important implication in infantile idiopathic scoliosis as it differentiates between progressive and resolving type of scoliosis.
Infantile idiopathic scoliosis is is first diagnosed between birth and 3 years of age. This category comprises about 1% of all idiopathic scoliosis in children and 60% of patients are males. The diagnosis of idiopathic infantile scoliosis is based on the age of onset, the absence of any other spinal cord problems, the location of the curve, findings on physical examination, and x-rays. T
Mehta rib vertebral angle degree difference has greater prognostic value. The Mehta angle is determined by identifying the vertebra in the apex or middle of the curve and measuring the difference in the angle of each rib attaching to the vertebra
A Rib vertebral angle difference of 20 degrees or less is associated with a non progressive or resolving curve in most cases.
How To Measure The Rib Vertebral Angle?
- A line is drawn perpendicular to the apical vertebral end plate [a]
- Another line is drawn from the midneck to the midhead of the corresponding rib [b]
The angle formed by the intersection of these lines is the Rib Vertebral Angle or RVA.
For calculating the rib vertbral angle difference (RVAD), the angle on the other side is calculated as well.
The difference between the values of the rib vertebral angles on the concave and convex sides of the curve is rib vertebral angle difference or RVAD.
Significance of Rib Vertebral Angle Difference
If the convex apical rib head does not overlap the apical vertebral body, a curve with an initial RVAD of 20 degrees or more is considered progressive.
If the convex apical rib head overlaps the apical vertebral body on the anteroposterior radiograph, progression is highly likely.
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