American Society of Hand Therapists Splint/Orthosis Classification System and Expanded ASHT Splint/Orthosis Classification System

In 1986 the ASHT conducted a survey of splint/orthosis nomenclature usage among its members and found that considerable differences existed, even in this highly specialized group. To address this problem, a special splint/orthosis Nomenclature Task Force of nationally and internationally recognized hand and upper extremity orthotic fabrication experts was established by the ASHT Board in 1989. This task force was given the charge “to conclusively settle the problems of existing splinting nomenclature.” The result of their work, the ASHT Splint/Orthosis Classification System, was published in 1992. Later, in what became known as the Expanded ASHT Splint/Orthosis Classification System, an additional purpose category (torque transmission) and two new descriptors for prostheses and orthosis-prosthesis were identified by Fess, Gettle, Philips, and Janson as they applied the classification system to over 1100 orthosis illustrations included in the 3rd edition of their splinting/orthotic fabrication book that subsequently was published in 2005.

Both the SCS and ESCS categorize orthoses according to a series of six descriptive criteria: (1) articular or nonarticular, (2) anatomic focus, (3) kinematic direction, (4) primary purpose, (5) type or number of secondary joint levels, and (6) total number of joints included in an orthosis ( Fig. 124-5 ). These six criteria combine to form a “sentence” that clearly and definitively describes an orthosis. Paralleling grammatical sentence structure, each element of the orthosis “sentence” defines a distinctly separate orthosis element.

An extension of the original ASHT Splint/Orthosis Classification System, the Expanded ASHT Splint/Orthosis Classification System adds an additional purpose category (torque transmission) and allows descriptives for prostheses and splint-prostheses.

For the first criterion, orthoses are considered to be either articular or nonarticular , depending on whether or not they affect joint motion. With the exception of a few specialized, two-point pressure, coaptation orthoses (e.g., fracture braces, pulley orthoses), the majority of orthoses operate as three-point pressure systems, directly influencing joint motion. Since most orthoses are articular in nature, the designation of articular is assumed for all orthoses in this category. Therefore, the word articular is not included in the SCS/ESCS sentence. In contrast, nonarticular orthoses are always designated as such in an SCS/ESCS sentence (e.g., nonarticular humeral orthosis). All of the orthoses discussed in this chapter fall into the articular category. Articular is assumed rather than specified in their respective SCS/ESCS names.

Anatomy : The primary joints affected by an orthosis are defined by the second of the six descriptors (e.g., shoulder, elbow, forearm; wrist, index, long, ring, small, thumb carpometacarpal [CMC] joint, metacarpophalangeal [MCP] joint, interphalangeal [IP] joint). If all the joints of a segment are considered primary joints, then the segment is named instead of the individual joints involved (e.g., finger, thumb). An example, if all four PIP joints are included as primary joints in an orthosis, the anatomy sentence descriptor would be: Index-small finger PIP joint .

The third criterion, direction , delineates the kinematic course into which the primary joints or segments are moved or positioned (e.g., flexion, extension, radial deviation). Continuing with the above example, if the desired direction is flexion, the SCS/ESCS sentence becomes Index–small finger PIP joint flexion .

Purpose , the fourth criterion, designates whether an orthosis is intended to immobilize, mobilize, or restrict motion, or transmit torque to primary joints/segments. If the purpose of the above example orthosis is mobilization, then the sentence is expanded to become, Index–small finger PIP joint flexion mobilization orthosis .

The fifth descriptor, type , identifies the number of secondary joint levels included in an orthosis. While the first four criteria are intuitive, type addresses the mechanical function of an orthosis. It is less obvious but no less critical than are the first four criteria. Without type, the classification system falls apart. In defining type, it is important to understand that secondary joints are not named per se, nor are they counted individually. Only the number of secondary-joint longitudinal levels is counted in the orthosis “sentence.” This is in direct contrast to primary joints that are specifically named. Secondary joints often are included to anchor orthoses and/or to control or eliminate undesirable motion of joints other than the primary-focus joints or segments. Secondary joints are not the joints to which corrective forces of an orthosis are aimed. For example, in the previously utilized orthosis example, the wrist and MCP joints may be included to eliminate the wrist tenodesis effect and to stabilize the MCP joints. This allows corrective forces to be directed to the primary PIP joints and eliminates unwanted dissipation of force at the two proximal-joint levels, the wrist level, and MCP joint level. In this example, two secondary joint levels, wrist and MCP joint, are included; therefore the orthosis would be considered a type 2 orthosis. The example orthosis sentence is further expanded to: Index–small finger PIP joint flexion mobilization orthosis, type 2 . If no secondary joint levels are included in an orthosis, it is classified as type 0; one secondary joint level is a type 1; three secondary joint levels are type 3, and so on.

The final descriptor, total joint count , is included at the end of the SCS/ESCS sentence in parentheses. This last criterion of the orthosis sentence explicitly counts the number of joints affected by the orthosis. Contrary to type where only the joint levels are counted, all primary and secondary joints are tallied individually in the total joint count number. In the above orthosis example, there are four primary joints, the PIP joints; and there are five secondary joints, the wrist and four MCP joints, for a total count of nine joints. The number 9 is included at the end of the sentence in parentheses. The finished orthosis sentence reads: Index–small finger PIP joint flexion mobilization orthosis, type 2 (9) .

While many orthosis designs and configurations may fit the orthosis sentence mentioned above, all will function in the same manner. Note that it makes no difference in the SCS/ESCS if an orthosis is applied volarly, dorsally, or laterally, or from what material it is constructed, because design options such as surface of application or material do not influence the intent/function of the orthosis. If it is absolutely critical to convey design options, these specifications may be added at the end of the sentence following a colon. The above example might then read, Index–small finger PIP joint flexion mobilization orthosis, type 2 (9): elastic traction , or if surface of application is vital to communication, the sentence may be written as Index–small finger PIP joint flexion mobilization orthosis, type 2 (9): volar application.

Another example, if the colloquial term “wrist cock-up” is used in a referral, confusion may ensue. Is the orthosis’s purpose to immobilize, to mobilize, or to restrict wrist motion or is it intended to transmit torque to digital joints? One can only guess. In contrast, using the SCS/ESCS, a “wrist cock-up” may be more scientifically described as:

• (A)
  

  Wrist extension immobilization orthosis, type 0 (1);

  
  
• (B)
  

  Wrist extension mobilization orthosis, type 0 (1);

  
  
• (C)
  

  Wrist flexion restriction orthosis, type 0 (1);

  
  
• (D)
  

  If its purpose is to transmit torque to the fingers as in an “exercise” orthosis, it is an Index–small finger extension and flexion torque transmission orthosis, type 1 (13).

In A through C above, the wrist is the primary joint and no secondary joint levels (type) are included in the orthosis. However, in D, the wrist is the secondary joint and the finger joints are primary joints, although they (finger joints) are not included within the physical boundaries of the orthosis. Compare the total joint count for orthoses A through D. It immediately becomes apparent that D is a very different functioning orthosis from A through C; further, A through C differ in function from each other. Note, not one design option is included in A–D, and yet the essential facts about these orthoses are known. It is even possible to speculate associated diagnoses for these orthoses, an impossibility when confronted with the ubiquitous “wrist cock-up” moniker.

A final example, the extension portion of an MCP joint arthroplasty orthosis, is classified as an Index–small MCP joint extension and radial deviation mobilization orthosis, type 1. The wrist is included as a secondary joint, while the MCP joints are primary joints. Although many different orthosis designs fit into this classification, they all function in the same manner.

As noted at the beginning of this section, many earlier classification methods broke down when required to describe “static” orthoses that were applied serially to correct joint deformity. With the SCS/ESCS method of grouping, orthoses are not categorized according to properties of their components but rather according to intent of application. A serial cast applied to extend the ring finger PIP joint is classified as a Ring finger PIP joint extension mobilization orthosis, type 0 (1) . The archaic and limited descriptors “static,” “dynamic,” and “static-progressive” are not used in the SCS/ESCS.

While the ramifications of using an accurate orthosis classification are readily apparent in the above examples, the positive consequences of exactingly describing orthoses are not restricted to clinical applications. In research, the SCS/ESCS allows orthoses with identical functions but different designs to be compared in clinical trials. For example, elastic and inelastic traction design options may be compared in orthoses with the same classification. Language is the key to professional evolution. The more defined splint/orthotic language is, the better the potential becomes for advancing knowledge and improving patient outcomes.

The power of the SCS/ESCS lies in the fact that communication among medical personnel is vastly improved through definition of the important functional aspects of orthoses and through elimination of the confusion caused by colloquial or regional orthosis jargon. Design options such as type of traction (elastic, inelastic), surface of application, material, and outrigger configuration are deemphasized and left to the expert judgment and creativity of those who fabricate orthoses. Use of the SCS/ESCS is an important element to firmly elevating the art of orthotic intervention to a solid science foundation by requiring those who fabricate orthoses to fully understand the intricacies of orthosis function and by discouraging cookbook approaches. Through its inherent characteristics that require in-depth knowledge of anatomy, kinesiology, physiology, and pathology, the SCS/ESCS transitions those who use the system from a technical to a professional echelon.