An evaluation of bimodality on quantitative measurement system for lachman test using force sensor

The anterior cruciate ligament (ACL) is one of the most important ligaments in the knee. The ACL injury often occurs while doing sports. Lachman test is one of the manual tests for examining the ACL. Examiners discriminates an injured degree of the ACL by feeling their finger stress. Measurement devices for Lachman test have been reported, however, these devices aim to analyze not the stress but a motion of the knee joint. Therefore, we focused on a development of a measurement system for the finger stress during Lachman test. The developed system could record the finger stress with force sensor. This study aims to propose an evaluation method of the stress data for bimodality which can be a criterion of injured degree. In a basic experiment, we examined a string which can be considered as normal knee. The result indicated obviously bimodality in the stress data. This study applied this system to three subjects with healthy knees. In the result, bimodality was observed in one or more finger(s) for each trial. Average of discrimination rate of bimodality for each wave was 90%. Therefore, the criterion of the bimodality can contribute to diagnose the injured knee. Future work is to apply the developed system to injured knees.