Lowest instrumented vertebra selection in AIS

Area of Science:

• Orthopedic Surgery
• Spinal Deformity Correction
• Pediatric Orthopedics

Background:

• Adolescent idiopathic scoliosis (AIS) requires careful surgical planning for optimal outcomes.
• Incorrect selection of the lowest instrumented vertebra (LIV) can lead to significant complications such as curve decompensation and "adding on."
• Preoperative assessment of spinal alignment and curve characteristics is critical in AIS management.

Purpose of the Study:

• To emphasize the critical role of lowest instrumented vertebra (LIV) selection in adolescent idiopathic scoliosis (AIS) surgical management.
• To outline key preoperative planning considerations for accurate LIV identification.
• To discuss methods for predicting postoperative outcomes and potential complications related to LIV choice.

Main Methods:

• Preoperative identification of stable, end, and neutral vertebrae.
• Classification of structural and nonstructural curves.
• Evaluation of curve flexibility using techniques like fulcrum bending, side bending, push-prone, and traction.
• Consideration of intraoperative techniques (e.g., derotation, release, contouring) and instrumentation type.

Main Results:

• Accurate LIV selection is essential for preventing postoperative curve decompensation and "adding on."
• Flexibility tests predict postoperative correction, residual LIV tilt, and disc wedging.
• Intraoperative techniques directly influence LIV selection and must be preoperatively considered.

Conclusions:

• Meticulous preoperative planning, including precise LIV identification, is paramount for successful AIS surgical correction.
• Understanding curve characteristics and flexibility aids in predicting and mitigating postoperative complications.
• Achieving spinal balance while preserving motion segments is the primary goal in AIS surgical management.