Weight bearing through flexed upper limbs in quadriplegics with paralyzed triceps brachii muscles

Study design: A biomechanical analysis of lifting through flexed and extend ed elbows in C5 and C6 quadriplegics. Objective: To determine the mechanisms used by C5 and C6 quadriplegics to p revent elbow collapse when bearing weight through flexed upper limbs. Setting: A biomechanics laboratory. Methods: Six motor complete C5 and C6 quadriplegic subjects with paralysis of their triceps brachii muscles were recruited. A three dimensional kinema tic and kinetic analysis of the upper limbs was performed whilst subjects a ttempted to lift their body weight through their upper limbs under four dif ferent conditions. In one condition subjects lifted with their hands placed at the same height as the seat upon which they were sitting, whilst in the other three conditions subjects lifted with their bands placed on blocks o f various heights. The four different conditions required subjects to bear weight through their upper limbs with their elbows initially flexed between 15 and 40 degrees, Main outcome measures: Angular displacements and corresponding moments abou t the shoulder, elbow and wrist joints. In addition, EMG data were collecte d from the upper pectoralis, anterior deltoid and biceps brachii muscles du ring all lifts and expressed as a percentage of maximal isometric voluntary contractions. Results: As block height and initial elbow flexion increased, subjects lift ed progressively less weight. However, even under the high block conditions when subjects' elbows were initially flexed up to 40 degrees, subjects lif ted a mean+/-SD of 43% +/-20.4 of their seated body weight with one subject lifting 76% of his seated body weight,Subjects lifted by generating should er and wrist flexor moments, Conclusion: Quadriplegics with paralyzed triceps brachii muscles can bear m oderate and sometimes substantial weight through flexed elbows. This is lar gely achieved by the generation of shoulder flexor moments.