The Implications of Sacralized Transitional Vertebra on Spinal Alignment

Area of Science:

• Spine biomechanics
• Radiographic analysis
• Orthopedic surgery

Background:

• Limited data exists on spinopelvic alignment in patients with lumbo-sacral transitional vertebra (LSTV).
• Understanding LSTV's impact on spinal alignment is crucial for accurate radiographic assessment.

Purpose of the Study:

• To evaluate the effect of sacralized lumbo-sacral transitional vertebra (LSTV) on spinal alignment in healthy volunteers.
• To determine how LSTV grade influences lumbar lordosis and spinopelvic parameters.
• To provide guidance on appropriate measurement points for spinopelvic parameters based on LSTV presence and grade.

Main Methods:

• Retrospective analysis of a multicentric prospective database of healthy volunteers over 18.
• Full-body stereoradiographs in a free-standing position were used for assessment.
• Parameters analyzed included Castellvi grade, pelvic incidence, lumbar lordosis (L1-S1), thoracic kyphosis, cervical lordosis, and global alignment.

Main Results:

• Low-grade LSTV (Castellvi I-II) demonstrated similar spinal alignment to non-LSTV subjects when pelvic incidence was matched.
• High-grade LSTV (Castellvi III-IV) showed altered lumbar lordosis distribution with a higher apex and inflexion point.
• The LSTV segment in high-grade cases was kyphotic, compensated by increased lordosis above L5.

Conclusions:

• Low-grade LSTV subjects exhibit alignment comparable to non-LSTV individuals, supporting S1 as the reference for spinopelvic measurements.
• High-grade LSTV is associated with a kyphotic L5-S1 segment and a more cranial lumbar apex.
• For high-grade LSTV, spinopelvic parameters should be measured using L5 as the reference point.