Orthoses are externally applied devices used to modify the structural and functional characteristics of the neuromusculoskeletal systems; prostheses are externally applied devices used to replace, wholly or in part, an absent or deficient body segment. Included are, e.g. body-powered and externally powered external orthoses, prostheses, orthopaedic footwear. Excluded are endo-prostheses, which are not part of this document.

Devices designed to compensate a loss of motor function by electrical stimulation (FES). Included are, e.g. functional electrical stimulators, hybrid orthotic systems used in combination with mechanical orthoses in hybrid orthotic systems. Stimulators for treatment on cellular and tissue level, see 04 27.