Rapid Detection of Common Failure Modes for Knee Prosthetics

Abstract The number of knee joint replacement procedures has increased exponentially over the last decade with no indications of slowing downWhile sustaining highly successful outcomesimplant failures still occur and the annual incidence of knee revision surgeries remain steady aroundof primary surgeriesImplant loosening has been cited as the dominant cause of long term failureLooseninghoweveris only detectable when the bone loss is so great that gaps between the implant and the bone are visible in an x ray imageby which time the loosening may be quite severe with an immediate risk of fracture of the remaining thickness of the bone around the implantWhen a patient has pain in or around their knee implantsurgeons are generally reluctant to perform revision surgery in the absence of a clear diagnosis of the cause of the painA tool with high sensitivity and specificity and the ability to detect loosening better than current diagnostics would provide a surgeon with the ability to confirmor rule outloosening of the implant during the diagnostic assessment of a patient in painBruin Biometrics LLC proposes to develop a non invasive device that could detect loosening of an artificial knee implant with greater accuracy than the current diagnostics standardThe final product is envisioned as a strap on device resembling a knee brace which uses sensors to capture acoustic emission and joint angle information while the test subject performs a series of flexion extension movementsMultiple passive acoustic sensors are in contact with the skin to pick up naturally occurring acoustic emissions from within the bodySignals from the sensors are filteredanalyzedand categorized to determine if any of the signals are caused by a loosened implant and the degree of looseningDuring the related Phaseprojectwe verified a loose implant will produce distinctive acoustic events relative to well functioning or otherwise worn implantsMore recentlywe established the additional uniqueness of these signals against naturally occurring native knee signals using a porcine knee modelEvidentlythe characteristics of acoustic signals generated by native tissuessuch as ligamenttendonsand musclesare readily distinguishable from artificial joint signals through frequency domain feature filteringThe work proposed for the phaseresearch will build on this base knowledge and develop and optimize a diagnostic tool capable of capturinglocatingand classifying signals indicative of implant looseningThis work will start with further in vitro testing of knees and implant and progress through cadaveric tests andfinallytesting of the device in conjunction with clinical evaluation of live post op human patients who are experiencing pain Project NarrativeRelevance to Public Health Knee replacement procedures will continue to increase dramatically over the next twenty years and the rate of revision surgery is expected to remain stable aroundThis will increase the burden on orthopaedic surgeonsoperating room capacityand healthcare costIndollarsthis volume of total joint replacement would generate costs exceeding $billionorof the gross domestic productGDPIf successfulthe new monitoring device object of this proposal namedOrthoSonoswill have an immediate impact on managing joint degradationreducing complicated revision surgeriesallowing more effective patient and implant manufacturer surveillance avoiding catastrophic failureand introduce an opportunity to improve therapeutics of problematic implantsthis in turn will increase patient confidence in regulatory agencies and industry while improving patient outcomes