Biomechanics of Upper Limb Orthoses

INTRODUCTION Functional impairment of [parts of] the upper limb has many different expressions. Sound biomechanical analysis is at the basis of the management of the physical challenges involved. An outline of the basics of a mechanical systems approach is presented below. Orthoses are among the many treatment options for upper limb impairments. An orthosis can be defined as a mechanical construction intended to improve a functioning part of the human body where the anatomical structures are still present. Orthoses fulfill their task by the exertion of forces onto the anatomical structures. Depending on the upper limb segments involved, and depending on the functional requirements [i.e. static support only, or dynamical assistance of muscle functions] a specific pattern of forces between the orthosis and the body is needed. Therefore, no universal upper limb orthosis exists. Each functional loss, in combination with personal wishes and demands, results in a different orthotic design. However, every orthosis needs to fulfill some basic requirements concerning cosmesis, comfort, and control. Some examples of orthotic management of the upper limb are elucidated below.