O&P Library > Orthotics and Prosthetics > 1974, Vol 28, Num 4 > pp. 49 - 54

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A Proposed Prosthetics Terminology

E. E. Harris, M.R.C.S. *

This report has been prepared for the Task Force on the Standardization of Prosthetic-Orthotic Terminology established by the Committee on Prosthetic-Orthotic Education of the National Academy of Sciences—National Research Council which first met on January 21, 1971, under the chairmanship of Jacquelin Perry, M.D. Many informed members of the various professions concerned with prosthetics from university, government, and private sectors have over the years contributed to the discussions at a number of meetings under the general chairmanship of Dr. Perry. The proposed terminology presented here was mostly formulated at the two meetings at Rancho Los Amigos Hospital, Inc., Downey, California, and the Rehabilitation Institute of Chicago, Illinois, under the acting chairmanship of Robert G. Thompson, M.D., and Paul R. Meyer, Jr., M.D. The participants of these two meetings are listed in the previous article by Hector W. Kay.

The Task Force on Standardization of Prosthetic-Orthotic Terminology (CPRD-CPOE) has agreed that the accepted nomenclature for amputation and prosthetics levels shall be that devised for transverse congenital deficiencies by the Subcommittee on Nomenclature and Classification in Congenital Limb Deficiency, International Society for Prosthetics and Orthotics, as described by Hector Kay in the preceding article. The nomenclature can be used independently of any terminology of systems, components, or materials. It is currently undergoing field trials in selected centers.


A descriptive terminology of systems, components, and materials was devised by the Task Force at its meeting on July 9, 1974, in Chicago, and is described here. This terminology can be used with any required degree of detail for prescription, education, fabrication manuals, fee schedules, information retrievals, or component catalogs. It is intended to be used with the nomenclature described in the preceding article, but could also be used independently. It has been proposed that a field trial be started in the fall of 1974, preferably as an international evaluation project through ISPO.

The following is a description of the proposed terminology of systems, components, and materials. It is proposed that a prosthesis be described in an orderly manner, proceeding from the general to the more detailed as follows:

  1.  General Characteristics
    1.  Prosthetics Level
    2.  Major Structural Feature
    3.  Durability
    4.  Cosmetic Treatment
  2.  Interface Characteristics
    1.  Socket
    2.  Suspension
    3.  Force Distribution
  3.  Systems and Mechanics
    1.  Joints at Each Level from Proximal to Distal
    2.  Joint Controls
    3.  Power Source of Controls
    4.  Alignment Devices
    5.  Terminal Devices - Upper Limb
  4.  Materials


  1.  Prosthetics level should be described according to the description in the preceding article by Kay .
  2.  Major Structural Feature. By international agreement prostheses are endoskeletal or exoskeletal. In some there may be a hybrid element but one or the other will be the "major" feature. Therefore prostheses are:
    • Endoskeletal
    • Exoskeletal
  3.  Durability. Some indication of temporari-ness or permanence of a prosthesis is needed and whether it is robust. Some agreement was reached at Heathrow about the need for different strengths of prostheses. Durability, therefore, needs two descriptors, one from list "a" and one from list "b."
    1.  Immediate Postsurgical Training (Diagnostic) Definitive
    2.  Geriatric Standard Heavy Duty
  4.  Cosmetic Treatment. At Chicago it was agreed that "anthropomorphic" and "nonanthropomorphic" were clumsy words, and since "cosmesis" was an acceptable and used term, "acosmetic" was suggested.

It has been suggested further by Anthony Staros that we do not want to say that a prosthesis is "acosmetic"; that is to say it is ugly. What is intended is to distinguish between special cosmetic treatment and standard procedures.

Cosmesis should therefore refer to special cosmetic treatment and would be: Cosmetic Cover Plastic on Wood or Metal Plastic Foam and Skin None

To say that there is no special cosmetic treatment does not infer that the prosthesis is necessarily ugly.


The reaction of the work load across the interface between prosthesis and patient takes place in the socket and sometimes in the suspension. Where that major reaction occurs must be specified but is recorded in the description of the socket and suspension.

  1.  Sockets. Sockets need three descriptors and may need a fourth for suspension. The first descriptor is the nature of the socket; the second is the nature of the materials constructing the socket; the third is the site of major force distribution. The fourth will be the socket's contribution to suspension. Sockets are therefore:
    1. Total Contact Non-total Contact
    2. Rigid Semirigid (e.g., liner) Compliant Hybrid
    3. Proximal Bearing Distal Bearing Total Bearing
    Materials (see section on Materials) can also be described, for example, the PTB air cushion socket could be "plastic (or even epoxy resin glass fiber) total-contact semirigid distal compliant proximal bearing socket."
  2.  Suspension. Ideally, suspension is from the socket where it may be "pressure differential" or "suction" or it may be body contour as in the complete tarsus, complete leg, complete hip, some partial leg, and some partial forearm prostheses, etc.
    Many prostheses need additional suspension by a harness, belt, etc. This is called auxiliary harness. The Task Force did not consider that distinction need be made between cuffs, bands, corsets, etc.
    The connection between the suspension and the prosthesis is a "joint" and if it is a strap or straps, it is indicated under the joint at the appropriate level as "flexible."
    When the auxiliary suspension also accepts a work load additional to the forces required to suspend, the anatomical site of that load should be indicated. Suspension is therefore:
    Pressure Differential (socket) Body Contour (socket)
    Auxiliary: Thigh Bearing, Ischial Bearing, Arm Bearing Shoulder, Bearing etc.
  3.  Force Distribution. This is a function of the interface but is described in the appropriate place under socket or auxiliary suspension.
    The nature of the distribution will itself determine some of the character of the socket and auxiliary suspension, e.g., in a partial leg prosthesis, the presence of uniaxial joints and the need for thigh and ischial bearing require a full length corset or thigh lacer.


1. Joints. Joints are described by the number of axes and the number of planes in which they move. There was some discussion about the use of "rigid" where no mechanical joint exists, but it was agreed that where there is no prosthetic mechanical joint at an anatomical joint level, this should be so described. Joints are therefore:

No motion at an anatomical joint level

Motion in one plane about one axis about multiple axes Uniaxial Polycentric
Motion in two planes about two axes Dual axis
Motion in three planes about finite axes about infinite axes Multiaxial Flexible

2. Control Mechanisms. In the lower limb, descriptors from a,b,c, and d, below, will have to be given as required for both stance and swing phases. Since stance is usually a greater requirement than swing, this should be stated first.

a. Plane and direction of movement (plane need not be stated)

Internal rotation
External rotation

b. Type of control mechanisms Constant or Intermittent and are:

  • Mechanical linkage
  • Hydraulic
  • Pneumatic
  • Electric
  • Other

The term "constant" is necessary to describe certain types of lower-limb swing phase controls and some upper-limb power actuators, etc. "Intermittent" indicates the reverse.

c. Purpose of control mechanisms at each joint movement

 modified as required by

d. Method of controlling mechanisms
Biomechanical, Direct
Biomechanical Transducer

3. Power Source

  • None (e.g., passive terminal devices)
  • Body
  • Electric
  • Hydraulic
  • Mechanical
  • Hybrid

4. Alignment

Bench Mechanical Single Integral Dual Removed Bench alignment is always present and need not be specified. When an alignment device is used, it should have two descriptors to denote whether it is at a single site or is at both ends of a "body" segment. It must also say whether it remains as an integral part or is removed at completion

of fabrication.

5. Terminal Devices

Hook or Special Tools
They may be:
Voluntary opening
Voluntary closing
Both Neither
They may be:
Powered as above


The need to specify materials depends upon a number of factors. In prescription, it will depend upon the relative knowledge of the physician and prosthetist which varies greatly in the international field. It may also be necessary in some countries to give fabrication details to satisfy governmental specifications. Instructional and fabrication manuals will need far greater detail than are required in ordinary usage.

Terminology for materials can be in general terms or can be specific; it can be a description in general of a whole system or can be applied to a component, e.g., one can refer to a "wooden leg" or "a wooden foot," a "plastic arm" or a "plastic socket." There are three grades of specification: first, general terms; second, semispecific terms; and third, specific terms. The first and sometimes the second grades are usually sufficient for prescription or normal description. The third will be necessary in professional instruction and fabrication manuals. For this third grade of specification, the national or international description and standards should be used.

  1. General
    Plastic etc.
    are often sufficient to distinguish between comparable prostheses or prosthetic components which are made to a known specification once the major grade has been decided.
  2. Semispecific Willow etc.
    Box calf Chamois Block leather etc.
    Aluminum Stainless Steel etc.
    Nylon webbing Coutil etc.
    Silastic Polypropylene Polycarbonate Glass fiber etc.
    These terms are rather more specific and are sometimes desirable in description and prescription.
  3. Specific. When specific materials need to be detailed, there are specific terminologies which are in use either internationally or nationally. Most of these terminologies are also given specific mechanical standards, an exception being leather which has not yet been successfully standardized.
    Each nation should use its own national specification first; if none is available, it should be the international standard; and if neither is available, it should choose from another nation's terminology.
    Forms that have been proposed for use in the field trials are shown in Appendix A and Appendix B.

Appendix A, Appendix B


  1. Department of Health and Social Security, England and Wales, Report of Conference on Physical Testing of Prostheses. Skyway Motel, Heathrow, London, England, March 25-27, 1974 (in press).
  2. Kay, Hector W., A proposed nomenclature for limb prosthetics, Orth. and Pros., 28:4, December 1974.

O&P Library > Orthotics and Prosthetics > 1974, Vol 28, Num 4 > pp. 49 - 54

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