The Lenke paradox: substantial agreement or methodological mirage?

Area of Science:

• Orthopedics
• Spine Surgery
• Radiology

Background:

• The Lenke classification is crucial for surgical planning in adolescent idiopathic scoliosis (AIS).
• Previous studies reported high reproducibility, but recent evidence suggests variability, particularly with lumbar and sagittal modifiers.
• Understanding reliability is key to optimizing AIS treatment strategies.

Purpose of the Study:

• To systematically evaluate the inter- and intra-observer reliability of the Lenke classification for AIS.
• To identify methodological factors influencing the agreement of the Lenke classification.
• To provide evidence-based recommendations for improving classification consistency.

Main Methods:

• A systematic review and meta-analysis adhering to PRISMA guidelines.
• Searched five major databases (PubMed, Embase, Cochrane CENTRAL, Scopus, Web of Science) up to August 2025.
• Extracted data on observer characteristics, imaging, measurement methods, and reliability indices (κ, ICC); assessed study quality using QAREL.

Main Results:

• Eleven studies involving 528 radiographs were included.
• Inter-observer reliability averaged κ=0.76 (lumbar κ=0.75, sagittal κ=0.79); intra-observer reliability was higher (κ≈0.82).
• Reliability was enhanced by pre-measured radiographs, experienced observers, computer assistance, and shorter intervals; lumbar modifiers were robust, while sagittal modifiers showed lower reproducibility.

Conclusions:

• The Lenke classification demonstrates good reliability under controlled conditions but is less consistent in routine clinical practice.
• Methodological factors significantly influence agreement, necessitating careful interpretation of reported reliability.
• Standardized protocols, transparent reporting, and digital tools are recommended to enhance the reproducibility of the Lenke classification.