LaxyKneTer: Low-cost prototype system for measuring knee laxity and detecting anterior cruciate ligament rupture

The ligaments that join the bone structures of the knee guide its mobility according to the tension in each of them, while also protecting it against certain abnormal movements. Of the four most important ligaments of the knee, the anterior cruciate ligament (ACL) is the one most frequently injured, whether through direct trauma or through a torsional force associated with braking or an abrupt change of direction while running.

The objectively reliable techniques then available for diagnosing an ACL injury or rupture, such as arthroscopy, were costly and dependent on highly specialized equipment in great demand in hospitals and health services. Diagnosing the injury without resorting to a CT or a scanner, using low-cost methods, required knowing the degree of displacement of the tibia over the femur, that is, the laxity of the knee, a process that in many cases depended largely on the person carrying out the examination, which made it difficult to obtain objective and repeatable measurements at low cost, especially in partial injuries.

In the absence of a single device meeting these requirements, LaxyKneTer proposed research into new measurement methods and computational algorithms for detecting ACL rupture, under the supervision of medical staff qualified in the field. The research took the form of a proof of concept based on a prototype knee laxity measurement system, with the general aim of generating the knowledge needed for a new type of low-cost laxity meter, including the design and construction of a functional prototype to assess its feasibility.

Two technical objectives were set for this: to generate a computational algorithm enabling data processing and visualization to detect anterior cruciate ligament rupture; and to build a laboratory prototype for the proof of concept, consisting of a knee laxity measurement system based on that algorithm, also designed so that the future product derived from the project results would be easy to use and transport, and capable of measuring laxity with sufficient precision (in millimeters) in the most automatic way possible.