1) Description of Measurement

Apical Vertebral Translation (AVT) measures the horizontal distance between the midpoint of the apical vertebral body and the Central Sacral Vertical Line (CSVL). It reflects the magnitude of coronal plane deformity in scoliosis and is widely used to assess curve severity, progression, and surgical correction.

2) Instructions to Measure

Imaging Requirements

• Standing coronal CT or reconstructed coronal plane image including sacrum and lumbar spine.

Step-by-Step

1. Draw the CSVL

• Identify the midpoint of the superior endplate of S1.

• Draw a vertical line upward from this midpoint perpendicular to the sacral base — this is the CSVL.

1. Identify the Apical Vertebra

• Locate the vertebra that is most laterally deviated from the CSVL in the lumbar curve.

1. Mark Vertebral Midpoint

• At the apical vertebra, mark the midpoint of the vertebral body.

1. Measure Translation

• Measure the horizontal distance (mm) from the apical vertebral midpoint to the CSVL.

3) Normal vs. Pathologic Ranges

• Normal: 0 - 5 mm

• Mild coronal translation: 6 - 15 mm

• Moderate translation: 16 - 30 mm

• Severe coronal imbalance/scoliosis: > 30 mm

4) Important References

Lenke LG, Betz RR, Harms J, et al. Adolescent idiopathic scoliosis: a new classification to determine extent of spinal arthrodesis. J Bone Joint Surg Am. 2001 Aug;83(8):1169-81.

King HA, Moe JH, Bradford DS, Winter RB. The selection of fusion levels in thoracic idiopathic scoliosis. J Bone Joint Surg Am. 1983 Dec;65(9):1302-13.

La Maida GA, Peroni DR, Ferraro M, et al. Apical vertebral derotation and translation (AVDT) for adolescent idiopathic scoliosis using screws and sublaminar bands: a safer concept for deformity correction. Eur Spine J. 2018 Jun;27(Suppl 2):157-164. doi: 10.1007/s00586-018-5626-9. Epub 2018 May 30.

5) Other info....

AVT is most accurate on standing coronal imaging.

Often combined with Cobb angle, coronal balance, and vertebral rotation to guide operative planning.

Larger AVT values correlate with increased cosmetic deformity and mechanical imbalance.

AVT is also used postoperatively to assess adequacy of deformity correction.