Abstract
A knee replacement surgery (arthroplasty) has become prevalent worldwide and has a high success rate over the short to medium term. In some cases, especially over the longer term, implant degradation can develop due to the deterioration of the ultra-high molecular weight polyethylene (UHMWPE) tibial insert. Unfortunately, there are no satisfactory techniques currently available for assessing implant integrity and predicting failure. This paper describes a possible solution to this problem by using a non-invasive, electromagnetic method for monitoring implant integrity. This approach utilizes the magnetoelastic property of amorphous ribbon, which when stressed causes an inductance change in a nearby magnetizing winding. Amorphous ribbons encased in UHMWPE disks, to simulate a knee insert, were subjected to varying tensile stresses under an applied ac magnetic field. A correlation between total circuit impedance and applied stress was observed. The results obtained demonstrate that the proposed sensor has sufficient sensitivity for measuring typical stress levels associated with the axial forces in tibial inserts.
Highlights
T ECHNOLOGICAL advancements in knee arthroplasty have made it prevalent around the world, with over half a million primary procedures performed in England and Wales alone during the last decade [1]
The most probable cause of premature implant failure is aseptic loosening, which is a severe physiological response to foreign debris in the joint. This debris is generated from abrasive wear in the ultra-high molecular weight polyethylene (UHMWPE) of the tibial insert, due to malpositioning of the articular surfaces and the high forces acting in the joint [3], [4]
Effective monitoring of the active stresses within the UHMWPE insert can provide a clearer perception of knee biomechanics, and provide real-time observation on the condition of the knee implant
Summary
T ECHNOLOGICAL advancements in knee arthroplasty have made it prevalent around the world, with over half a million primary procedures performed in England and Wales alone during the last decade [1] It is a complex surgical procedure, which requires the proper alignment of the new and existing articular surfaces, in combination with the accurate repositioning of the associated tissues. The most probable cause of premature implant failure is aseptic loosening, which is a severe physiological response to foreign debris in the joint. This debris is generated from abrasive wear in the ultra-high molecular weight polyethylene (UHMWPE) of the tibial insert, due to malpositioning of the articular surfaces and the high forces acting in the joint [3], [4]. Effective monitoring of the active stresses within the UHMWPE insert can provide a clearer perception of knee biomechanics, and provide real-time observation on the condition of the knee implant
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