Can Postoperative Distal Adding-On be Predicted in Lenke Type 1B and 1C Curves with Intraoperative Radiographs?

Area of Science:

• Orthopedic Surgery
• Spinal Deformity
• Radiographic Analysis

Background:

• Distal adding-on (DA) is a radiographic complication in adolescent idiopathic scoliosis (AIS) that can impact clinical outcomes.
• Assessing risk factors for DA using intraoperative radiographs is crucial but understudied.

Purpose of the Study:

• To identify risk factors for postoperative distal adding-on (DA) in Lenke Type 1B and 1C adolescent idiopathic scoliosis (AIS) curves.
• To utilize intraoperative radiographs to evaluate these risk factors.

Main Methods:

• A retrospective study of 69 AIS patients with Lenke Type 1B or 1C curves undergoing posterior selective thoracic fusion.
• Patients were categorized into DA and non-DA groups based on 2-year follow-up radiographs.
• Comparison of coronal and intraoperative radiographic parameters, including vertebra-to-lowest instrumented vertebra (LIV) relationships.

Main Results:

• Distal adding-on (DA) was observed in 18.8% of patients at 2-year follow-up.
• Smaller relative positions of the end vertebra (EV), neutral vertebra (NV), stable vertebra (SV), and last touching vertebra (LTV) to the LIV were associated with DA.
• Multivariate analysis identified LIV-LTV position and intraoperative angulation of the first disc below the LIV (>3°) as significant risk factors for DA.

Conclusions:

• Selecting the LIV more cranially to the LTV is a potential risk factor for postoperative DA in Lenke Type 1B and 1C curves.
• Consideration of LIV extension may be warranted when intraoperative radiographs show angulation >3° below the LIV.