Percent Change in Model Predicted Muscle Moment Arms.

<p>Average percent change in (A) flexion-extension and (B) radial-ulnar deviation moment arms for the SE4CF (blue) versus the PRC (red) models relative to the nonimpaired model. Note that the y-axis scales are different between the two panels.</p

Wrist Muscle Moment Arms Predicted by the Models^#.

<p>Wrist Muscle Moment Arms Predicted by the Models<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0157346#t001fn001" target="_blank">^#</a>.</p

Muscle-Tendon Path Assumptions for the PRC Model.

<p>Illustration of a wrapping surface in (A) the nonimpaired and (B) the PRC models. In the nonimpaired model, the location of the wrapping surfaces is defined relative to the proximal row. In the PRC models, the location of the wrapping surfaces was redefined relative to the capitate by either maintaining the distance between the wrapping surface and capitate or maintaining the distance between the wrapping surface and radius. Shading of the capitate (black) and radius (gray) provides a visual reference to compare the location of the wrapping surface between the nonimpaired and PRC models. The torus shaped wrapping surface (shown for the ECRL) is representative of the wrapping surfaces implemented for each wrist muscle.</p

Study Design.

<p>Flowchart describing (A) predictive simulations to formulate a hypothesis regarding how muscle moment arms change following surgical salvage procedures and (B) the cadaveric experiment used to validate the simulation-based hypothesis.</p

Significant Differences in Experimentally Measured Muscle Moment Arms.

<p>Depicted muscles indicate statistically significant differences (p<0.05) between the nonimpaired and surgically salvaged moment arm versus joint angle curves, as measured experimentally. (A) Wrist and (B) thumb muscles are displayed separately to illustrate similar trends in how PRC (red) and SE4CF (blue) influence flexion-extension moment arms (left) and radial-ulnar deviation moment arms (right) across the two distinct muscle groups.</p

Axes of Rotation Assumption for the SE4CF Model.

<p>Illustration of the axes of rotation in the (A) nonimpaired and (B) SE4CF models. In the nonimpaired model, flexion-extension and radial-ulnar deviation axes of rotation separately define the motion of the proximal row relative to the radius (green axes) and the distal row relative to the proximal row (blue axes). In the SE4CF models, the motion of the fused carpal bones was defined using either the proximal row or distal row axes of rotation.</p

Model Predicted and Experimentally Measured Moment Arm Comparison.

<p>Comparison of moment arms predicted by the models (non-circular shapes) to moment arms measured in the experiment (filled circles) for the (A) nonimpaired, (B) SE4CF, and (C) PRC wrists. In each graph, flexion-extension moment arms are plotted as a function of radial-ulnar deviation moment arms. Error bars represent one standard deviation. In (B) and (C), the model data (triangles) represent the centroid of the moment arms predicted by the surgical models, and the shaded regions are the minimum area ellipses that enclose the predicted values, thereby representing the spread of the model predictions. All values are moment arms at a neutral wrist posture.</p

Extrinsic Thumb Muscles: Experimentally Measured Wrist Muscle Moment Arms^#.

<p>Extrinsic Thumb Muscles: Experimentally Measured Wrist Muscle Moment Arms<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0157346#t003fn001" target="_blank">^#</a>.</p

Wrist Models.

<p>(A) Bone geometry and (B) muscle paths implemented in the nonimpaired, SE4CF, and PRC models. Only the five primary wrist muscles were included: <i>extensor carpi radialis longus</i> (ECRL), <i>extensor carpi radiali brevis</i> (ECRB), <i>extensor carpi ulnaris</i> (ECU), <i>flexor carpi radialis</i> (FCR), and <i>flexor carpi ulnaris</i> (FCU). Muscle paths were constrained to anatomically realistic lines of action using via points and wrapping surfaces.</p