A simple clinical method of recording knee kinematics during functional activity using flexible electrogoniometry and the Strathclyde University Data Logging System (SUDALS) for use in multi-centre RCTs of TKA

Padmanaabhan Indra Mohan, V. and Rowe, P.J. (2009) A simple clinical method of recording knee kinematics during functional activity using flexible electrogoniometry and the Strathclyde University Data Logging System (SUDALS) for use in multi-centre RCTs of TKA. In: Clinical Movement Analysis Society UK 8th Annual Meeting, 2009-03-30 - 2009-03-31.

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Abstract

Among the various commercially available data collecting systems for use with a flexible electrogoniometer, there is currently a paucity of a user friendly system. What is required is a system where by clicking a single button a user can remotely record and transmit the information pertaining to the flexion/extension of the knee during activities of daily living (ADL) via Bluetooth wireless connection. Such a device could be used to quantify the knee joint motion outside the gait laboratory, efficiently, by clinical staff at low cost and hence would be suitable for use in multi-centre RCT's of TKA. The aim of this project was to develop such a system which we have called the Strathclyde University Data Logging System (SUDALS.) SUDALS is a 6 channel, battery operated, remote control, microprocessor based system that has the potential to collect kinematic joint data such as flexion/extension of the knee and also mark movement events such as foot falls during various ADL. Flexible electrogoniometers are used to measure the kinematics and force sensing resistors can be used as foot switches or other event markers. The data logger can be pre-programmed so that all the user needs to do is attach the instruments, turn on the logger and then initiate data collection by pressing an infra red key fob. During functional activities, the user-friendly system stores the data from these transducers and transfers the same to a PC at the end of the recording period via a Bluetooth connection. The logger can be started and stopped at will using the key fob and hence multiple tests can be recorded and only the data of interest stored. Software on the PC then displays the angular displacement and allow visual inspection of the entire sequence of recordings or particular events of interest. Prior to releasing the system for general use, it was necessary to validate the newly developed system against a gold standard and test its accuracy, reliability and reproducibility. The pattern of flexion/extension of the knee from 10 normal subjects was collected during a range of activities of daily living (ADL) such as: walking, ascending and descending stairs, in and out of a chair and deep squatting. The accuracy, reliability and reproducibility of the data from SUDALS were verified by comparing against the data simultaneously collected from the VICON system during walking from three normal subjects. In addition to this, a series of controlled experiments were carried out to investigate the properties of electrogoniometer when used with SUDALS. The results of these studies indicate that the SUDALS together with flexible electrogoniometers is able to produce stable, precise, accurate and repeatable knee flexion/extension angles with little variation existing between the electrogoniometers and producing data similar to those reported in the literature. A cross correlation coefficient of 0.97 shows that there is a good similarity between the two sets of data obtained from 8 camera motion analysis system and the SUDALS system. Further, a Pearson correlation coefficient of 0.9 among the data obtained during three repeat trial sessions shows that there is a high degree of correlation and repeatability between the trials. We have concluded that the SUDALS system together with flexible electrogoniometers appear to be a useful clinical tool, capable of recording knee flexion/extension angles accurately during ADL and suitable for use by clinical research staff in multi centre RCT's of TKA.

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