Rib vertebral angle measurement and its significance were brought in by Dr Mehta. Measurement of this angle has an important implication in infantile idiopathic scoliosis as it differentiates between the progressive and resolving type of scoliosis.
Infantile idiopathic scoliosis 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 nonprogressive or resolving curve in most cases.
How To Measure The Rib Vertebral Angle?
- A line is drawn a perpendicular to the apical vertebral endplate [a]
- Another line is drawn from the mid-neck to the mid head of the corresponding rib [b]
Rib Vertebral Angle Difference
The angle formed by the intersection of these lines is the Rib Vertebral Angle or RVA.
For calculating the rib vertebral 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.