Shoulder model validation and joint contact forces during wheelchair activities

Area of Science:

• Biomechanics
• Musculoskeletal modeling
• Rehabilitation engineering

Background:

• Chronic shoulder impingement is prevalent in manual wheelchair users due to high-frequency, high-load activities.
• Understanding shoulder joint loading is crucial for identifying injury risks in daily wheelchair use.

Purpose of the Study:

• Validate an upper extremity musculoskeletal model for estimating shoulder joint contact forces.
• Analyze shoulder loading during various manual wheelchair activities.

Main Methods:

• Measured upper extremity kinematics and handrim kinetics during level propulsion, ramp propulsion, and weight relief lifts.
• Utilized a subject-specific musculoskeletal model with optimization to predict shoulder joint contact forces.
• Validated the model using mean absolute error.

Main Results:

• Ramp propulsion and weight relief lifts resulted in significantly higher shoulder joint contact loading compared to level propulsion.
• Elevated superior contact forces were observed during ramp and weight relief activities, indicating impingement risk.
• Level propulsion showed lower relative risk, though frequency of activity warrants further consideration.

Conclusions:

• Ramp propulsion and weight relief lifts pose a significant impingement risk for manual wheelchair users.
• The validated musculoskeletal model effectively estimates shoulder joint contact forces during wheelchair activities.
• Further research is needed to definitively assess the long-term risk of level propulsion given its high frequency.