Academic journal article Human Factors

Practical Operation of a Biaxial Goniometer at the Wrist Joint

Academic journal article Human Factors

Practical Operation of a Biaxial Goniometer at the Wrist Joint

Article excerpt

INTRODUCTION

Awkward wrist postures have been found to be a major contributing Ask factor for occupational cumulative trauma disorders (CTDs) of the hand and wrist, such as tendinitis, tenosynovitis, and carpal tunnel syndrome (Armstrong, 1986). Although awkward wrist posture has often been cited as a risk factor for CTDs, few researchers have quantitatively investigated how wrist posture and motion increase the risk of CTDs (Marras & Schoenmarklin, 1993). Checklists and other observational techniques are commonly employed to qualitatively assess exposure to awkward wrist posture (Putz-Anderson, 1988).

Prior to the introduction of electrogoniometers, collection of continuous postural data could be obtained only through detailed analysis of videotape. One of the more common methods that has been employed for postural studies of the wrist was developed by Armstrong, Foulke, Joseph, and Goldstein (1982). This method employs a frame-by-frame analysis of videotape that, besides being extremely time intensive, records wrist flexion/extension in only one of five categories and radial/ulnar deviation in only one of three categories. This gives an absolute resolution of approximately 30 [degrees] for flexion/extension and 20 [degrees] for radial/ulnar deviation. In addition, dynamic components of wrist motion, such as velocity and acceleration, are lost with this type of analysis.

A commercially available biaxial flexible wire electrogoniometer (Penny and Giles Blackwood Ltd., Gwent, UK) has been developed to record a continuum of postural motions in real time (Nicol, 1987). The device consists of two lightweight plastic end blocks that are separated by a flexible spring that protects a wire. The angle of one block with respect to the other is determined using sets of strain gauges fitted to orthogonal surfaces of the wire. One set of strain gauges measures angles in one plane, and the orthogonal set measures angles in an orthogonal plane. The flexible spring slides in and out of the distal end block to accommodate length changes that are required during angular movements. It has widespread application throughout the biomedical, biomechanical, and ergonomics fields because of its small size, light weight, simple application, unobtrusiveness, and high sampling rate.

A number of studies have already been performed using the system in clinical, laboratory, and field settings (e.g., Ball & Johnson, 1993; Boocock, Jackson, Burton, & Tillotson, 1994; Rowe, Nicol, & Kelly, 1989). Additional studies have examined application of the goniometer to the wrist joint. For instance, Smutz, Serina, and Rempel (1994) employed the goniometer for wrist posture measurement in their ergonomic assessment of keyboard designs; Moore, Wells, and Ranney (1991) and Wells, Moore, Potvin, and Norman (1994) used the goniometer to quantify wrist motion and posture in their field assessments of ergonomic risk factors; and Ojima, Miyake, Kumashiro, Togami, and Suzuki (1991) performed a dynamic analysis of wrist circumduction using the goniometer in clinical trials.

Although the Penny and Giles goniometer is an effective device for quantifying postures and joint motions, errors in the goniometric measurements attributable to twist in the wire from practical application on the human body should be recognized and corrected for (Armstrong, Dunnigan, Ulin, & Foulke, 1993). Casolo and Legnani (1990) have developed a theoretical model that mathematically describes the effect that wire twist has on the output of the Penny and Giles goniometer. In order to apply their model to goniometer use at the wrist joint, one must understand the effect of forearm rotation on wire twist.

The objectives of this study were (a) to determine errors in wrist angle measurements caused by forearm rotation using the Penny and Giles electrogoniometer and (b) to develop a correction routine in order to adjust for these errors. Hand length was included in this study as an independent variable because we felt that hand length would affect placement of the proximal end block on the forearm and that this would affect the relationship between twist and forearm rotation. …

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