Design of an Electro-Mechanical Device for Knee Loading Applications

Abstract

Mechanical loading of the knee is an innovative modality developed for rehabilitation of the knee joint as well as the femur and tibia that are subjected to bone fractures, osteoarthritis and osteoporosis. Loading essentially applies a lateral and periodic force to the knee joint [1]. In this paper, we propose the design of an electro-mechanical device that is capable of applying such dynamic loads. The key variable attributes of this device are the magnitude of the loading force, together with displacement and frequency. A DC motor with a controller actuates the device to produce the necessary force. The loading force is applied to the knee by a set of pads in a restricted linear motion. The operation of the device is approximated using the software package, SimMechanics of MATLAB. The simulations show that the device is capable of producing a suitable loading force with desired frequency. This simulation helps in constructing the device and performing experiments with appropriate frequencies. The device is expected to stimulate the fluids in porous skeletal matrix, resulting in strengthening the knee and bones. It can be employed for clinical trials for necessary evaluations and improvements.

A Mechatronic Loading Device to Stimulate Bone Growth via a Human Knee

“…The lengths of the linkage bars are mathematically calculated and then modelled to produce a maximum range of motion of 0.012 m. They are calculated using geometric representations of the mechanism, and, through that, trigonometric equations were deduced to calculate various lengths and angles in the mechanism [10]. Some of them are initially assumed, whereas others are calculated.…”

“…The linkage arm was designed using geometrical quantities [10]. Since the range of motion is constrained, the variable quantities can be varied such that the slider gives the required displacement.…”

“…Other mechanical structures were designed, keeping this mechanism as a reference so that the system has overall symmetry like the fixable support pad. The dimensions of the pad are chosen based on an average sized human knee cross-sectional area [10]. …”

“…Using this software platform, the device’s CAD model is successfully analyzed and the amount of torque needed to produce the required force from this model was obtained [11]. The SimMechanics environment model is shown in Figure 5 [10]. …”

“…The results from the dynamic simulation from the force sensor blocks in the Simulink toolbox (MATLAB R 2014, MathWorks, Natick, MA, USA ) are shown in Figure 6 and Figure 7 [10]. These results show that the device was capable of producing required loading force and torque at prescribed frequencies.…”