A Handheld Computer as Part of a Portable In Vivo Knee Joint Load-Monitoring System

In vivo measurement of loads and pressures acting on articular cartilage in the knee joint during various activities and rehabilitative therapies following focal defect repair will provide a means of designing activities that encourage faster and more complete healing of focal defects. It was the goal of this study to develop a totally portable monitoring system that could be used during various activities and allow continuous monitoring of forces acting on the knee. In order to make the monitoring system portable, a handheld computer with custom software, a USB powered miniature wireless receiver, and a battery-powered coil were developed to replace a currently used computer, ac powered benchtop receiver, and power supply. A Dell handheld running Windows Mobile operating system programed using LABVIEW was used to collect strain measurements. Measurements collected by the handheld-based system connected to the miniature wireless receiver were compared with the measurements collected by a hardwired system and a computer based system during benchtop testing and in vivo testing. The newly developed handheld-based system had a maximum accuracy of 99% when compared to the computer based system.