Influence of end-effector on the risk of shoulder pathologies after forearm amputation: Use of the active shoulder abduction measurement

Abstract

After upper limb amputation, the use of prosthesis usually causes compensation movements for trunk and stump. These compensations can lead to musculoskeletal pain or overuse syndromes. In the context of occupational pathologies, stress levels were defined as at risk for shoulder concerning abduction amplitude (60°) and duration of exposure (2/24 h or 8.5% of the time beyond 60°). The objective of this study is to evaluate the risk of shoulder complications in a population of below-elbow amputees when using different myoelectric prosthetic end-effectors. Eight below-elbow amputees fitted with tridigital myoelectric prosthetic hand potential users of non-morphometric end-effectors in professional or leisure time are evaluated. Shoulder abduction (mean abduction and percentage of time spent beyond 60° of abduction) is measured during a Box and Block Test in a sitting position with a VICON optoelectronic system. The measurements are performed for amputated limb in 2 or 3 conditions: non-morphometric end-effector with or without wrist flexion-extension ± with tridigital myoelectric prosthetic hand (for 3 amputees) and for healthy limb. There is no significant difference in dexterity between end-effectors but significant difference between all end-effectors and healthy limb. The mean shoulder abduction is greater than 60° and the median percentage of time beyond 60° abduction is greater than 8.5% only when using a non-morphometric end-effector without wrist flexion-extension. Moreover, there is a significant difference between the 2 limbs for the mean abduction only with the non-morphometric effector without wrist flexion-extension. There are no differences between the other end-effectors and healthy limb, nor between the end-effectors between them. Prosthetic grip and mobility capacity of prosthetic wrist also influence shoulder kinematics. For some amputees, shoulder abduction is not at risk for musculoskeletal disorders but other compensation movements (internal shoulder rotation, trunk torso…) remain to be studied. The quantification of stresses on residual limb and trunk related to these compensations could allow to detect risk of musculoskeletal complications. A personalized analysis of compensations during common task could guide the choice of prosthetic end-effector and its adjustment and allow to quantify the influence of rehabilitation techniques on these compensations.