0
Research Papers

A New Subject-Specific Skin Correction Factor for Three-Dimensional Kinematic Analysis of the Scapula

[+] Author and Article Information
Douglas A. Bourne

Department of Orthopaedics, Division of Orthopaedic Engineering Research, Vancouver Coastal Health Research Institute, University of British Columbia, Vancouver, BC V6T 1Z3, Canada; Department of Physical Therapy, University of British Columbia, Vancouver, BC V6T 1Z3, Canada; Faculty of Kinesiology, University of Calgary, Calgary, AB T2N 1N4, Canada

Anthony M. Choo

Department of Orthopaedics, Division of Orthopaedic Engineering Research, Vancouver Coastal Health Research Institute, University of British Columbia, Vancouver, BC V5Z 4E3, Canada

William D. Regan

Department of Orthopaedics, Division of Upper Extremity Reconstruction, University of British Columbia, Vancouver, BC V5Z 4E3, Canada

Donna L. MacIntyre

Department of Physical Therapy, University of British Columbia, Vancouver, BC V6T 1Z3, Canada

Thomas R. Oxland1

Department of Orthopaedics, Division of Orthopaedic Engineering Research, Vancouver Coastal Health Research Institute, University of British Columbia, Vancouver, BC V5Z 4E3, Canadatoxland@interchange.ubc.ca

1

Corresponding author.

J Biomech Eng 131(12), 121009 (Nov 24, 2009) (9 pages) doi:10.1115/1.4000284 History: Received February 11, 2008; Revised August 28, 2009; Posted September 23, 2009; Published November 24, 2009; Online November 24, 2009

Noninvasive measurement of scapular kinematics using skin surface markers presents technical challenges due to the relative movement between the scapula and the overlying skin. The objectives of this study were to develop a noninvasive subject-specific skin correction factor that would enable a more accurate measurement of scapular kinematics and evaluate this new technique via comparison with a gold standard for scapular movement. Scapular kinematics were directly measured using bone pins instrumented with optoelectronic marker carriers in eight healthy volunteers while skin motion was measured simultaneously with optoelectronic markers attached to the skin surface overlying the scapula. The relative motion between the skin markers and the underlying scapula was estimated over a range of humeral orientations by palpating and digitizing bony landmarks on the scapula and then used to calculate correction factors that were weighted by humeral orientation. The scapular kinematics using these correction factors were compared with the kinematics measured via the bone pins during four arm movements in the volunteers: abduction, forward reaching, hand behind back, and horizontal adduction. The root-mean-square (rms) errors for the kinematics determined from skin markers without the skin correction factors ranged from 5.1 deg to 9.5 deg while the rms errors with the skin correction factors ranged from 1.4 deg to 3.0 deg. This technique appeared to perform well for different movements and could possibly be extended to other applications.

FIGURES IN THIS ARTICLE
<>
Copyright © 2009 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Figure 1

Pictorial representation of how a subject-specific skin correction factor could be determined: in various orientations of the humerus, skin marker positions (i.e., dots) are determined while the underlying scapula is digitized (i.e., arrows). The mathematical relation between the two represents the correction factor.

Grahic Jump Location
Figure 2

A subject with skin markers and bone pins over the left scapula. Note the marker carrier on the bone pins. Bone pins with marker carrier. The picture on the right also shows humeral and trunk markers.

Grahic Jump Location
Figure 3

Coordinate systems used in this study

Grahic Jump Location
Figure 4

Flowchart of the skin correction factor. The white box represents the uncorrected joint angles that are typically calculated while the dark gray box on the right represents the corrected angles.

Grahic Jump Location
Figure 5

Sample data demonstrating the effect of the skin correction factor based on the average of ten repetitions. Reference frame one was taken at time 0 s. Reference frame three was taken at time 3.5 s. The corrected line is a combination of reference frames one and three weighted toward reference frame one at the beginning of motion and reference frame three at the end of the motion. The angles from reference frame one are analogous to the white box in the flowchart.

Grahic Jump Location
Figure 6

Abduction: comparison of pins versus corrected and uncorrected skin markers for posterior tipping, upward rotation, and external rotation in a typical subject based on the average of ten repetitions

Grahic Jump Location
Figure 7

Abduction (based on the average of ten repetitions): mean errors for the corrected (thick lines) and uncorrected (thin lines) are represented with solid lines while the standard deviations are represented with dashed lines

Grahic Jump Location
Figure 8

Reaching (based on the average of ten repetitions): mean errors for the corrected (thick lines) and uncorrected (thin lines) are represented with solid lines while the standard deviations are represented with dashed lines

Grahic Jump Location
Figure 9

Hand behind back (based on the average of ten repetitions): mean errors for the corrected (thick lines) and uncorrected (thin lines) are represented with solid lines while the standard deviations are represented with dashed lines

Grahic Jump Location
Figure 10

Horizontal adduction (based on the average of ten repetitions): mean errors for the corrected (thick lines) and uncorrected (thin lines) are represented with solid lines while the standard deviations are represented with dashed lines. The movement starts from the right of the graph (coronal plane) and proceeds to the left (sagittal plane).

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In