Devices, systems and methods for monitoring knee replacements

Abstract

Knee replacement prosthesis are provided, comprising a plurality of sensors and at least one of a femoral component, a patellar prosthesis and a tibial component.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application No. 61 / 838,317 filed Jun. 23, 2013, which application is incorporated herein by reference in its entirety.BACKGROUND[0002]1. Field of the Invention[0003]The present invention relates generally to knee replacements, and more specifically, to devices and methods for monitoring the performance of total and partial knee replacements[0004]2. Description of the Related Art[0005]Knee replacement is one of the most common reconstructive orthopedic surgical procedures. It may be carried out when the patient loses sufficient use of the knee, typically as a result of osteoarthritis, rheumatoid arthritis and other forms of arthritis (lupus, psoriatic and others), a previous knee injury (knee ligament tears (anterior cruciate, posterior cruciate, medial collateral and / or lateral collateral ligaments) and meniscus tears) and the sequellae of previous recon...

AI Technical Summary

Benefits of technology

[0019]According to one embodiment, the sensors provide evaluation data on the range of motion (ROM) of the knee. Currently, ROM is usually measured clinically by the physician passively moving the knee joint through a full range of motion during physical examination and recording the results (degrees of flexion, extension, anterior / posterior stability and medial / lateral stability; see, e.g., FIG. 4). Motion sensors and accelerometers can be used to accurately determine the full ROM of the prosthetic knee joint both during physical examination and during normal daily activities between visits. Similarly, motion sensors and accelerometers can be used to accurately measure any anterior / posterior or medial / lateral instability (including full, partial or subclinical dislocation) of the prosthetic knee joint both during physical examination and during normal daily activities between visits. Additionally, motion sensors and accelerometers can be used to accurately measure any improper tracking of the patella and / or patellar instability (including full, partial or subclinical subluxation) during physical examination and during normal daily activities between visits.

[0028]Within further embodiments, each of the sensors contains a signal-receiving circuit and a signal output circuit. The signal-receiving circuit receives an interrogation signal that includes both power and data collection request components. Using the power from the interrogation signal, the sensor powers up the parts of the circuitry needed to conduct the sensing, carries out the sensing, and then outputs the data to the interrogation module. The interrogation module acts under control of a control unit which contains the appropriate I / O circuitry, memory, a controller in the form of a microprocessor, and other circuitry in order to drive the interrogation module. Within yet other embodiments the sensor (e.g., an acceleration sensor, a tilt sensor, a vibration sensor, a shock sensor, a rotation sensor, a pressure sensor, a contact sensor, a position sensor, a chemical microsensor, a tissue metabolic sensor, or a mechanical stress sensor) are constructed such that they may readily be incorporated into or otherwise mechanically attached to the knee prosthesis (e.g., by way of a an opening or other appendage that provides permanent attachment of the sensor to the knee prosthesis) and / or readily incorporated into the bone cement or the tissues that surround the knee prosthesis.

Problems solved by technology

Unfortunately, when a total knee is inserted, various complications may arise intra-operatively, in the post-operative period and over time.

Post-operatively, the patient may experience inflammation and pain if there is slight movement, partial (subluxation) or full dislocation of any of the components of the knee prosthesis.

Longer term, there may be progressive wear between the femoral surface and the tibial surface, which leads to improper operation of the knee joint.

Depending on the types of materials used for the tibial surface and the femoral surface, prolonged wear can result in the generation of small debris particles which lead to inflammation and bone erosion surrounding the implant.

A related common complication occurs when, over a period of time (for example 8-12 years), bone loss occurs in the tissues surrounding the implant (due to a process known as osteolysis) that leads to loosening and ultimately failure of the prosthesis.

All of the above acute and chronic complications may degrade the performance of the knee, result in difficulty in movement and ambulation, and may cause pain and inflammation for the patient.

As mentioned, one of the most common and serious complications of TKR is erosion of the bone around the implant (osteolysis) which may be caused by material debris (metal, ceramic, and / or polyurethane fragments) generated by friction, and causing inflammation and bone loss.

Other potential causes of inflammation and osteolysis are implant vibration and motion, improper patient usage / activities, improper alignment (including improper tracking of the patella), subclinical dislocation (subluxation) of the tibial-femoral joint and the patellar-femoral joint, mechanical wear and tear, material failure or breakage, loosening of the bond between the bone and the cement, lack of biocompatibility between the implant materials and the surrounding bone, metal allergy, and lack of biocompatibility between the bone cement and the surrounding bone.

Unfortunately, most of the patient's recuperative period occurs between hospital and / or office visits.

It can, therefore, be very difficult to accurately measure and follow full joint range of motion (ROM can change depending on pain control, degree of anti-inflammatory medication, time of day, recent activities, and / or how the patient is feeling at the time of the examination), “real life” prosthesis performance, patient activity levels, exercise tolerance, and the effectiveness of rehabilitation efforts (physiotherapy, medications, etc.) from the day of surgery through to full recovery.

For much of this information, the physician is dependent upon patient self-reporting or third party observation to obtain insight into post-operative treatment effectiveness and recovery and rehabilitation progress; in many cases this is further complicated by a patient who is uncertain what to look for, has no knowledge of what “normal / expected” post-operative recovery should be, is non-compliant, or is unable to effectively communicate their symptoms.

Sudden increases in strain may indicate that too much stress is being placed on the replacement prosthesis, which may increase damage to the body.

For example, a gradual, long-term decrease in strain may cause bone reabsorption around the implant, leading to loosening of the prosthesis or fractures in the bone surrounding the prosthesis, while a gradual, long-term increase in strain may lead to microfractures of the prosthesis materials themselves.

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