Shoulder joint kinetics and pathology in manual wheelchair users.

BACKGROUND

Manual wheelchair users rely heavily on their upper limbs for independent mobility which likely leads to a high prevalence of shoulder pain and injury. The goal of this study was to examine the relationship between shoulder forces and moments experienced during wheelchair propulsion and shoulder pathology.

METHODS

Kinetic and kinematic data was recorded from 33 subjects with paraplegia as they propelled their wheelchairs at two speeds (0.9 and 1.8 m/s). Shoulder joint forces and moments were calculated using inverse dynamic methods and shoulder pathology was evaluated using a physical exam and magnetic resonance imaging scan.

FINDINGS

Subjects who experienced higher posterior force (Odds Ratio (OR)=1.29, P=0.03), lateral force (OR=1.35, P=0.047), or extension moment (OR=1.35, P=0.09) during propulsion were more likely to exhibit coracoacromial ligament edema. Individuals who displayed larger lateral forces (OR=4.35, P=0.045) or abduction moments (OR=1.58, P=0.06) were more likely to have coracoacromial ligament thickening. Higher superior forces (OR=1.05, P=0.09) and internal rotation moments (OR=1.61 P=0.02) at the shoulder were associated with increased signs of shoulder pathology during the physical exam.

INTERPRETATION

Specific joint forces and moments were related to measures of shoulder pathology. This may indicate a need to reduce the overall force required to propel a wheelchair in order to preserve upper limb integrity. Potential interventions include changes to wheelchair setup, propulsion training, or alternative means of mobility.