Bilateral Asymmetry in Microarchitecture of Trabecular Bone in Male C57bl/6 Mouse Tibia: Implication for Experimental Sample Size Estimations.

Bilateral asymmetry in microarchitecture of trabecular bone in male c57bl/6 mouse tibia: implication for experimental sample size estimations.

Proc Inst Mech Eng H. 2013 Apr 18;
Ko CY, Jung YJ, Seo DH, Kim HS

This study aimed to determine whether there is bilateral asymmetry between the left and right tibiae in the microarchitectural characteristics of the trabecular bone and estimate a moderate sample size for detections of such bilateral differences. The left and right tibiae of 20 C57BL/6 mice (12 weeks old) were scanned by micro-computed tomography, and the structural parameters of the trabecular bone were measured. There were significant differences in the structural parameters between the left and right tibiae (p < 0.05); specifically, the microarchitecture was greater in quantity and quality in the left tibia than in the right tibia. Moreover, the percent of bilateral differences between the left and right tibiae ranged from 2.26% to 22.52%. For most of the structural parameters except for trabecular bone thickness (Tb.Th) and trabecular bone separation (Tb.Sp), the 20 mice involved in this study were enough to detect differences. These results show that the directional left-right asymmetry in the microarchitecture of the trabecular bone may exist despite the samples being from an inbred strain. Furthermore, we estimated a sample size for detections of such differences between the left and right tibiae. HubMed – rehab


Evaluation of cast creep occurring during simulated clubfoot correction.

Proc Inst Mech Eng H. 2013 Apr 26;
Cohen TL, Altiok H, Wang M, McGrady LM, Tarima S, Krzak J, Graf A, Smith PA, Harris GF

The Ponseti method is a widely accepted and highly successful conservative treatment of pediatric clubfoot involving weekly manipulations and cast applications. Qualitative assessments have indicated the potential success of the technique with cast materials other than standard plaster of Paris. However, guidelines for clubfoot correction based on the mechanical response of these materials have yet to be investigated. The current study sought to characterize and compare the ability of three standard cast materials to maintain the Ponseti-corrected foot position by evaluating cast creep response. A dynamic cast testing device, built to model clubfoot correction, was wrapped in plaster of Paris, semi-rigid fiberglass, and rigid fiberglass. Three-dimensional motion responses to two joint stiffnesses were recorded. Rotational creep displacement and linearity of the limb-cast composite were analyzed. Minimal change in position over time was found for all materials. Among cast materials, the rotational creep displacement was significantly different (p < 0.0001). The most creep displacement occurred in the plaster of Paris (2.0°), then the semi-rigid fiberglass (1.0°), and then the rigid fiberglass (0.4°). Torque magnitude did not affect creep displacement response. Analysis of normalized rotation showed quasi-linear viscoelastic behavior. This study provided a mechanical evaluation of cast material performance as used for clubfoot correction. Creep displacement dependence on cast material and insensitivity to torque were discovered. This information may provide a quantitative and mechanical basis for future innovations for clubfoot care. HubMed – rehab


New wearable walking-type continuous passive motion device for postsurgery walking rehabilitation.

Proc Inst Mech Eng H. 2013 Mar 19;
Zhu Y, Nakamura M, Horiuchi T, Kohno H, Takahashi R, Terada H, Haro H

While total knee arthroplasty is useful for treating osteoarthritis of the knee, the success of this treatment depends on effective rehabilitation. The goal of this study was to develop an assistive device for post-total knee arthroplasty patients for walking rehabilitation and for shortening the hospitalization period. We developed a brace electronic assist system termed the knee assistive instrument for walking rehabilitation (KAI-R) to illustrate the need for training during postoperative rehabilitation. Sixteen osteoarthritis patients (1 male and 15 females; average age 68.9 years) who underwent total knee arthroplasty were analyzed before operation and 2-4 weeks after operation, and 25 healthy individuals (14 males and 11 females; average age 26.2 years) formed the control group. Based on the pre- and postoperative data on peak knee flexion angle, foot height, and walking velocity, we developed the KAI-R, which consists of an assistive mechanism for the knee joint, a hip joint support system, and a foot pressure sensor system and is driven by a CPU board that generates the walking pattern. We then tested the walking gait in seven healthy volunteers with and without KAI-R assistance. KAI-R increased the peak flexion angle of the knee and foot height in all seven volunteers; their range of motion of the knee joint was increased. However, KAI-R also decreased the walking velocity of subjects, which was explained by reaction delay and slightly compromised physical balance, which was caused by wearing the KAI-R. KAI-R is useful for gait improvement. In future studies, KAI-R will be investigated in a clinical trial for its ability for walking rehabilitation in post-total knee arthroplasty patients. HubMed – rehab


Simultaneous Characterizations of Reflex and nonreflex, dynamic and static changes in spastic hemiparesis.

J Neurophysiol. 2013 May 1;
Zhang LQ, Chung SG, Ren Y, Liu L, Roth EJ, Rymer WZ

This study characterizes tonic and phasic stretch-reflex and stiffness and viscosity changes associated with spastic hemiparesis. Perturbations were applied to the ankle of 27 hemiparetic and 36 healthy subjects under relaxed or active contracting conditions. A nonlinear delay differential equation model characterized phasic and tonic stretch-reflex gains, elastic stiffness, and viscous damping. Tendon reflex was characterized with reflex gain and threshold. Reflexively, tonic-reflex gain was increased in spastic ankles at rest (P<0.038) and was not regulated with muscle contraction, indicating impaired tonic stretch-reflex. Phasic-reflex gain in spastic plantarflexors was higher and increase faster with plantarflexor contraction (P<0.012) than controls (P<0.023) and higher in dorsi-flexors at lower torques (P<0.038), primarily due to its increase at rest (P=0.045), indicating exaggerated phasic stretch-reflex especially in more spastic plantarflexors which showed higher phasic stretch-reflex gain than dorsi-flexors (P<0.032). Spasticity was associated with increased tendon-reflex gain (P=0.002) and decreased threshold (P<0.001). Mechanically, stiffness in spastic ankles was higher than that in controls across plantar/dorsi-flexion torque levels (P<0.032), and the more spastic plantarflexors were stiffer than dorsi-flexors at comparable torques (P<0.031). Increased stiffness in spastic ankles was mainly due to passive stiffness increase (P<0.001), indicating increased connective tissues/shortened fascicles. Viscous damping in spastic ankles was increased across the plantar flexion torque levels and at lower dorsi-flexion torques, reflecting increased passive viscous damping (P=0.033). The more spastic plantar flexors showed higher viscous damping than dorsi-flexors at comparable torque levels (P<0.047). Simultaneous characterizations of reflex and nonreflex changes in spastic hemiparesis may help evaluate/treat them more effectively. HubMed – rehab