Journal of Orthopaedic & Sports Physical Therapy - Shun-Hwa Wei, PT, PhD

Evaluation of the Metrecom and Its Use in Quantifying Skeletal Landmark Locations

Tue, 09 Sep 2008 00:00:00 EST

Gary L. Smidt, Kevin J. McQuade, Shun-Hwa Wei
Several factors can be involved in evaluating a motion analysis system. The purposes of this study were to evaluate: 1) the accuracy, repeatability, and linearity of the Skeletal Analysis System (Metrecom System) and 2) the reliability of bony landmark identification with a method using the Metrecom Skeletal Analysis System (Metrecom Method) to obtain coordinates for human skeletal landmarks. A calibration control object with 20 known three-dimensional coordinates in a rectangular field was used as the gold standard for evaluating the Metrecom System for measuring X, Y, and Z spatial coordinates. The Metrecom Method was then evaluated using a test-retest approach for 10 bony landmarks on each of 10 normal subjects examined by two different examiners. Relative to the Metrecom System, the results demonstrated that the hysteresis was minimal (1.8 mm), and linearity was excellent. The differences between the true and measured distances for the 20 known points were not statistically significant (p ≥ .05). The variability for any point within the field of measurement was homogeneous (p ≤ .05). The accuracy (average difference between known and measured points) of the Metrecom System was found to be 2.7 mm. Repeatability in terms of the stability of the Metrecom System as indicated by deviations along the X, Y, and Z axes was .22, .57, and .31 mm, respectively. The results involving the Metrecom Method showed that the intraexaminer and interexaminer differences were not statistically significant (p ≥ .05). The mean intrarater reliability (ICC) for identification of coordinates for 10 bony landmarks was .95 for one examiner and .96 for the other examiner. The mean interrater ICC was .87, with all coefficients being above .80. In conclusion, use of the Metrecom System is affected by controllable human factors, in which case valid and reliable measurements for skeletal landmarks can be obtained.

J Orthop Sports Phys Ther 1992;16(4):182-188.

Key Words: skeletal landmarks, evaluation, measurement system

Three-Dimensional Joint Range of Motion Measurements from Skeletal Coordinate Data

Fri, 05 Sep 2008 00:00:00 EST

Shun-Hwa Wei, Kevin L. McQuade, Gary L. Smidt

Frequently, joint range of motion is reported for a single plane (eg, sagittal, coronal, or transverse). However, the arc of joint motion during functional activities and many clinical tests encompasses motion in all 3 planes simultaneously. The purposes of this paper are to discuss a method to obtain relative joint 3-dimensional angular displacement measurements using coordinates from skeletal landmarks and provide an analytical example of the method using 3-dimensional angular displacement of the knee joint as a model.

In order to calculate the 3-dimensional relative motion, an orthogonal reference frame for each bone needs to be established. To establish the local reference frame, 3 noncollinear points are used to define unit vectors that are mutually perpendicular. Three-dimensional angles can be determined to describe the magnitude of the moving body rotation angles about the X, Y, and Z axes. These angles indicate the relative motion of body segments for abduction/adduction, flexion/extension, and internal/external rotation.

The technique provides a more vigorous biomechanical understanding of joint motion and may have implications for measuring patient progress and evaluating joint mobilization treatment. This technique may also serve as a basis for developing new evaluation and treatment techniques.

J Orthop Sports Phys Ther. 1993;18(6):687-691.

Key Words: range of motion, kinematics, biomechanics

Interinnominate Motion and Symmetry: Comparison Between Gymnasts and Nongymnasts

Mon, 05 Feb 2007 09:45:00 EST

Edward Barakatt, Gary L. Smidt, Jeffrey D. Dawson, Shun-Hwa Wei, Deborah L. Givens

Some clinical approaches to the treatment of low back pain evaluate and treat observed asymmetries of pelvic posture and motion. Scientific evidence suggests the motion available between the innominate bones is small and variable in nature. The purposes of this investigation were 1) to determine if interinnominate motion of subjects without low back pain was symmetrical in reciprocal test posture combinations, 2) to assess innominate bone symmetry in standing, and 3) to determine if a difference in the magnitude of interinnominate motion was present between a subject group which performs more frequent flexibility activities compared with a subject group representing the general population. Thirty-four subjects (8 male gymnasts, 9 female gymnasts, 8 male nongymnasts, and 9 female nongymnasts) were evaluated in standing and 3 other reciprocal postures (modified standing, modified sitting, and half-kneeling). In each posture, the Metrecom Skeletal Analysis System was used to obtain coordinates for the anterior and posterior iliac spines. Projection angles were used to determine the relative positions of the right and left innominate bones. Results suggest that stand to right modified standing and stand to left modified standing oblique sagittal interinnominate composite motions were symmetrical; stand to right modified sitting and stand to left modified sitting oblique sagittal interinnominate composite motions were asymmetrical; and stand to right half-kneel and stand to left half-kneel oblique sagittal interinnominate composite motions' symmetrical properties were mixed depending on the group. Gymnasts as a group were found to have asymmetrically positioned innominate bones while nongymnasts as a group had symmetrically positioned innominate bones.

J Orthop Sports Phys Ther. 1996;23(5):309-319.

Key Words: sacroiliac, innominate, joint motion