Kaufman, Kenton R

An ultraminiature micropressure sensor to accurately measure intramuscular pressure has been developed. The MEMS sensor is fabricated through surface micromachining and consists of a capacitive array of eight 150 μm diameter sensing membranes connected in parallel. The membranes have been vacuum-sealed via a subsequent deposition and patterning batch microfabrication step. A deep reactive ion etcher (DRIE) based postfabrication self-release has been utilized to fabricate individual devices. Each device has an outline that incorporates specially designed “anchor” structures that are utilized to attach on the muscle tissue during measurements to minimize the effect of muscle contractions on sensor readings. Electrical isolation of the wire bonds and bonding pads has been accomplished by utilizing glob-topping technique. The fabricated sensor performance has been experimentally validated inside a pressure chamber. The current sensors have 0.2 mm Hg pressure resolution in the ±19 mm Hg dynamic range with negligible hysteresis and show a flat frequency response in the 0–5.5 Hz experimental test range.

While much work has previously been done in the modeling of skeletal muscle, no model has, to date, been developed that describes the mechanical behavior with an explicit strain-energy function associated with the active response of skeletal muscle tissue. A model is presented herein that has been developed to accommodate this design consideration using a robust dynamical approach. The model shows excellent agreement with a previously published model of both the active and passive length-tension properties of skeletal muscle.

This study analyzed forces in the tibiofemoral and pa tellofemoral joints during isokinetic exercise using an analytical biomechanical model. The results show that isokinetic exercise can produce large loads on these joints, especially during extension exercises. The tibio femoral compressive force (4.0 body weight) is approx imately equal to that obtained during walking but it occurs at 55° of knee flexion. Anterior shear forces (resisting force to anterior drawer) exist during exten sion exercise at less than 40° of knee flexion, with a maximum of 0.3 body weight. Posterior shear forces (resisting force to posterior drawer) exist during exten sion exercise at knee joint angles greater than 40° and during the flexion portion of isokinetic exercise. The maximum posterior shear force is 1.7 body weight. The patellofemoral joint can encounter loads as high as 5.1 body weight which are 10 times higher than during straight leg raises. These results suggest that isokinetic exercise should be used cautiously in patients with knee lesions.

Eighteen junior elite figure skaters were filmed while performing axel and double axel jumps. These same skaters were assessed for strength of the shoulders, knees, and hips at multiple angular velocities using a Cybex II system. The height of the jumps was signifi cantly correlated with the strength data. Knee exten sion at 240 deg/sec and shoulder abduction at 300 deg/sec were shown to be the most important strength parameters in determining the height of the jump. This information may be useful for designing strength train ing programs for figure skaters.

Despite the use of wrist guards during skate- and snowboard activities, fractures still occur at the wrist or at further proximal locations of the forearm. The main objectives of this study were to conduct a human subject testing under simulated falling conditions for measurement of the impact force on the hand, to model wrist guards as a shock isolator, to construct a linear mass-spring-damper model for quantification of the impact force attenuation (Q-ratio) and energy absorption (S-ratio), and to determine whether wrist guards play a role of an efficient shock isolator. While the falling direction (forward and backward) significantly influenced the impact responses, use of wrist guards provided minimal improvements in the Q- and S-ratios. It was suggested based on the results under the submaximal loading conditions that protective functions of the common wrist guard design could be enhanced with substantial increase in the damping ratio so as to maximize the energy absorption. This would bring forth minor deterioration in the impact force attenuation but significant increase in the energy absorption by 19%, which would help better protection against fall-related injuries of the upper extremity.

The specific aim of this study was to develop a quantitative method and a kinematic method to evaluate the maximal workspace of the trapeziometacarpal (TM) joint. Six fresh-frozen human cadaver hands were disarticulated 4 cm proximal to the wrist joint and used in this experiment. The three-dimensional motion data of the TM joint was collected by an electromagnetic tracking device at 30 Hz. The workspace was reconstructed according to a complete set of motion data included circumduction, flexion-extension and abduction-adduction. A spherical fitting technique was used to obtain a sphere encompassing all the motion trajectories and estimating the centre of the sphere. The surface area of the maximal TM workspace, located on the one part of the sphere surface, was calculated by surface integration. The interclass correlation coefficient values for the reliability estimation of the repeated measurements of the radius and surface area of all specimens were 0.91 and 0.98 respectively. The mean coefficients of variance of the measured radius and the surface area were 2.04 per cent and 3.65 per cent respectively. The results also showed that using a spherical model to calculate the maximal workspace as an index for assessing TM joint impairment is practical.