A Pilot Study Comparing Intentional Shoulder Kinematics of Patients With Symptomatic Small-Size Supraspinatus...

The prevailing view is that painful shoulders exhibit abnormal kinematics. This study explores the impact of symptomatic small-size supraspinatus tendon full-thickness tears on the three-dimensional (3D) kinematics of intentional, effortless shoulder movements. The hypothesis suggests that mechanical force buildup patterns, as indicated by motion jerk, will differ between healthy individuals and patients with symptomatic rotator cuff tendinopathy.

A comparative analysis was conducted on two groups: 10 patients with painful shoulders due to a Grade 1 small-size full-thickness tear of the supraspinatus tendon (Group A) and 10 healthy volunteers (Group B). Participants performed a standardized effortless shoulder movement task involving arm elevation and depression without external resistance, while an arm-attached accelerometer recorded movement data. The primary outcome was jerk (a derivative of acceleration), normalized to lean body mass (LBM), with comparisons made both within and between groups.

Vertical angular velocity was consistent across the study groups and in both arms of healthy volunteers, with mean values ranging from 70 to 86 degrees per second (deg/sec) (p = 0.79). No significant differences in jerk values were observed between groups or between dominant and non-dominant limbs in Group B (mean values: 0.001 to 0.004 m/sec³/kg LBM; p > 0.05).

This pilot study suggests that small supraspinatus tendon full-thickness tears, when pain is the primary symptom, do not significantly affect the 3D kinematics of effortless shoulder movements. These findings challenge the notion that pain from rotator cuff tears leads to altered shoulder kinematics, with potential implications for clinical decision-making and assessing functional disability. Larger studies are needed to confirm these results.