Assessing Abnormal Proximal Junctional Angles in Adult Spinal Deformity: A Normative Data Approach to Define Proximal...

Area of Science:

• Spine surgery
• Orthopedics
• Radiographic assessment

Background:

• Current definitions of proximal junctional kyphosis (PJK) do not account for vertebral level.
• Establishing normative values for proximal junctional angles (PJA) is crucial for accurate assessment in adult spinal deformity (ASD).

Purpose of the Study:

• To determine the rate of abnormal proximal junctional angles (PJA) in adult spinal deformity (ASD) surgery patients using normative data from asymptomatic volunteers.
• To compare the rate of abnormal PJA with the rate of proximal junctional kyphosis (PJK) using established definitions.

Main Methods:

• A multicentric retrospective study of prospectively collected data from 721 healthy volunteers and 824 ASD surgery patients.
• Normative PJA values for each thoracic level (T1-T12) were defined in volunteers (mean±2SD).
• Abnormal PJA values in ASD patients were compared to normative data and PJK definitions (Glattes', Lovecchio's) at two-year follow-up.

Main Results:

• Normative PJA values indicate normality above 20° between T3-T12.
• In ASD patients, 22.9% exhibited kyphotic PJA compared to normative values (P<0.001).
• PJK rates were 46.2% (Glattes') vs. 8.7% (Lovecchio's), highlighting discrepancies.

Conclusions:

• This study provides level-specific normative PJA values for the thoracic spine.
• Level-adjusted PJA assessment offers a more precise evaluation of proximal spinal alignment abnormalities.
• The findings challenge existing definitions of PJK and advocate for a more refined diagnostic approach.