Revisit to scapular dyskinesis: three-dimensional wing computed tomography in prone position

Area of Science:

• Orthopedics
• Radiology
• Biomechanics

Background:

• Scapular dyskinesis is a common issue in shoulder pathologies.
• Assessing scapular dyskinesis traditionally relies on observational methods with variable reliability.
• Three-dimensional (3D) wing computed tomography (CT) presents a promising imaging modality for objective assessment.

Purpose of the Study:

• To evaluate the inter-rater reliability (IRR) of 3D wing CT in assessing scapular dyskinesis.
• To classify scapular movements into distinct types using 3D CT measurements.
• To determine cutoff values for key scapular angles and correlate them with clinical shoulder conditions.

Main Methods:

• 165 patients' 330 scapular movements were classified into 4 types by 7 blinded observers.
• 4 blinded observers measured 5 angles (upward rotation, superior translation, anterior tilting, protraction, internal rotation) using 3D wing CT in the prone position.
• Inter-rater reliability was calculated, and cutoff values for the angles were established.

Main Results:

• 3D wing CT demonstrated a high IRR (0.981) compared to observational methods (0.783).
• Specific angles (UR, ST, AT, PRO, IR) showed significant differences across the 4 identified scapular movement types.
• Cutoff values were determined: UR 117°, ST 90°, AT 8°, PRO 99°, IR 51°. UR and IR angles correlated with glenohumeral internal rotation deficit and multidirectional instability (MDI), respectively.

Conclusions:

• 3D wing CT is a reliable tool for quantifying scapular dyskinesis.
• Established cutoff values for specific angles can aid in diagnosing and classifying scapular movement abnormalities.
• High UR angles may indicate a low risk of internal rotation deficit, while high IR angles are associated with a higher rate of MDI.