Kinesthetically guided reaching accuracy in individuals with a history of traumatic anterior shoulder dislocation

You-jou Hung,¹ Warren G Darling<sup>2

1</sup>Doctor of Physical Therapy Program, Department of Nursing and Rehabilitation Sciences, Angelo State University, San Angelo, TX, USA; ²Department of Health and Human Physiology, The University of Iowa, Iowa City, IA, USA

Background: The purpose of the study was to investigate whether individuals with a history of traumatic anterior shoulder dislocation show larger reaching errors than those with healthy shoulders and to determine if they implement different reaching strategies to protect the injured shoulder.
Methods: Ten people with a history of traumatic anterior shoulder dislocation and 15 with healthy shoulders volunteered for this study. After viewing targets in space, participants pointed with the unconstrained arm to remembered target locations in space without visual guidance. Nine different targets were located in various planes and heights. Endpoint reaching errors were determined by comparing the finger endpoint position without visual guidance to the target location. Shoulder rotation angle at the endpoint was also compared between groups.
Results: Participants with injured shoulders were able to point voluntarily to visually specified targets as accurately as participants with healthy shoulders (1 cm difference). However, participants with injured shoulders showed less shoulder external rotation (average 12° difference) at the target location when compared with healthy shoulders. This difference was consistent over a large range of target locations.
Conclusion: Individuals with a history of traumatic anterior shoulder dislocation have sufficient kinesthetic information about their upper limb orientation to point accurately to visually specified targets in space. However, individuals with injured shoulders acquired a new motor strategy to reach with less shoulder external rotation, presumably to protect the injured shoulder from recurrent injuries.

Keywords: shoulder injuries, physiotherapy, shoulder instability, motor control