Investigating the Effect of Elevation and Sex-Based Differences on Shoulder Proprioceptive Accuracy.

Abstract

Background: Evaluating shoulder proprioception provides functional data that supplement imaging for the diagnosis/rehabilitation of rotator cuff injuries. There is a need for a system capable of establishing normal ranges for proprioceptive accuracy in healthy shoulders during unrestricted 3-dimensional motion.

Purpose: To conduct passive joint position sense (JPS) testing in men and women with no history of shoulder injury using a novel testing system, identifying differences in proprioceptive accuracy based on sex, shoulder elevation, and crossbody position.

Study design: Controlled laboratory study.

Methods: We recruited 20 (10 male and 10 female) healthy participants aged between 18 and 25 years for JPS testing. Participants used a single wrist-worn sensor, and our primary outcome was errors in position matching (first guiding a participant's dominant arm from a neutral starting position to a target position and then having participants independently return from the start position to the same target) across 12 targets comprised of all possible combinations of shoulder elevation angles (EAs) (30°, 60°, 90°, and 120°) and crossbody angles (CAs) (0°, 45°, and 90°). A linear mixed model was employed to evaluate sex- and position-based differences in JPS accuracy.

Results: Position-matching accuracy increased in both males and females as target EAs increased from 30° to 120° (P < .001). The greatest EA position-matching accuracy in both sexes was observed at EAs of 90° and 120° (P < .0001). A change in the direction of error was observed in both males and females as target EAs increased from 90° to 120°, transitioning from positive (overshooting) to negative (undershooting) error (P < .005). A sex-based difference was observed at EAs of 60°, 90°, and 120° in the 90° CA plane, where females exhibited more negative CA matching error compared with males (P < .01).

Conclusion: Proprioceptive accuracy increased in both sexes at higher shoulder elevations. In the 90° CA plane, females demonstrated greater CA undershoot than males.

Clinical relevance: While magnetic resonance imaging and ultrasound are effective tools for determining the size/age of rotator cuff tears, they do not provide functional prognostic insight for pain or mobility. Proprioceptive testing, as a functional metric based on free shoulder motion, may assist in clinically characterizing a patient's shoulder injury and rehabilitative success at multiple time points.