Three-dimensional kinematic features in large and massive rotator cuff tears with pseudoparesis

Area of Science:

• Orthopedics
• Biomechanics
• Musculoskeletal Research

Background:

• Massive rotator cuff tears can impair shoulder function, but the precise criteria for loss of arm elevation ability remain unclear.
• Understanding the relationship between tear characteristics and shoulder kinematics is crucial for diagnosing and managing these debilitating injuries.

Purpose of the Study:

• To analyze the specific tear features and three-dimensional (3D) shoulder kinematics associated with the loss of arm elevation in patients with large and massive rotator cuff tears.
• To identify kinematic indicators of pseudoparesis in patients with significant rotator cuff pathology.

Main Methods:

• Prospective enrollment of 13 patients (15 shoulders) with large/massive rotator cuff tears, divided into pseudoparesis (P) and non-pseudoparesis (NP) groups.
• Collection of fluoroscopic images during active arm elevation and analysis of 3D shoulder kinematics using 2D-3D registration.
• Comparison of radiographic findings and kinematic results between groups, with correlation analysis between tear size and kinematics.

Main Results:

• The pseudoparesis group exhibited significantly higher superior humeral head positioning (P = .0321) and more frequent superior migration (>5 mm) (P = .0201).
• Thoracohumeral external rotation was significantly reduced in the pseudoparesis group (P < .0001).
• Tear size, particularly of the posterior rotator cuff, significantly correlated with superior and anteroposterior humeral head translations and tended to correlate with reduced glenohumeral external rotation.

Conclusions:

• Anterior and posterior rotator cuff tears cause significant humeral head translation, with posterior tears potentially leading to loss of external rotation.
• Superior humeral head migration and reduced thoracohumeral external rotation are key kinematic features indicative of pseudoparesis in massive rotator cuff tears.