PSM: Pivot Shift Meter Cellphone Application for Classifying ACL Injuries
Carlos Alejandro Vega Nájera, Joel Cabral Guzmán, Luis Raúl Sigala González, Avril Pérez Fontes, Jesús Javier Tonche Ramos, Iván René Ramos Moctezuma, Fátima Norely Quintana Trejo, Carlos Leal Contreras, Edmundo Berumen Nafarrate
Christus Muguerza del Parque Hospital, Chihuahua, México
Anterior Cruciate Ligament (ACL) lesions are frequent in knee rotational and sports injuries, and rotational instability is the most important factor to determine long term outcomes and failures. An accurate endorsement of the pivot shift test is key to define therapeutic paths. But this test cannot be numerically measured, and the gold standard KT-1000 test can only measure the anterior translation of the tibia over the femur. A precise measurement of pivot shift could give an advantage in determining the rotational instability of both ACL bundles.
The rotational stability of the knee can be accurately measured using a mobile phone application.
Materials And Methods
A technological application named Pivot Shift Meter (PSM) was designed to provide a dynamic evaluation of rotational stability of the knee, measured in rad/s (angular velocity) through the gyroscope integrated in a mobile phone. The evaluation of 52 young, healthy subjects was obtained by 5 different medical practitioners. The time and maximum velocity reached of each maneuver was then used in intraclass correlation coefficient (ICC) study to find the differences between the practitioner’s maneuvers. The correlation study variables were maneuver time and amplitude of maximum speed. Then the data obtained with the PSM was analyzed to create a classification of injury degree, using an already established classification named as the “Del Parque'' Classification obtained through the KT1000.
The ICC study results in terms of time and maximum velocity reached give an average result of 94% and of 66%, respectively, from an interobserver correlation. These results demonstrated that a quantitative analysis of the maneuver can be carried out through the application. From these correlation results, the samples were grouped into classes determined by the speed of the maneuver reached and then analyzing each sample to determine the degree of injury. These analysis results were compared against the KT1000 classification, and it was found that 95% of the cases were classifiable, with 7 extra cases detected by the PSM.
In the present study PSM was able to precisely measure rotational instability, providing quantitative dynamic diagnostic information that the gold standard arthrometer cannot offer.
Digital arthrometry seems to be the way to develop methods for the precise and numerical evaluation of rotational instability, with all the advantages that an early diagnosis and classification prior to any surgical treatment can provide.
Level of Evidence: Case - Control Study