Design and test of a MEMS strain-sensing device for monitoring artificial knee implants

W Hasenkamp,N Thevenaz,J Villard,P Renaud,A Bertsch,K Aminian,A Terrier,A Arami

doi:10.1007/s10544-013-9770-z

W Hasenkamp, N Thevenaz + Show 6 more

Open Access

https://doi.org/10.1007/s10544-013-9770-z

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Abstract

This paper describes the development of a polyimide-based MEMS strain-sensing device. Finite element analysis was used to investigate an artificial knee implant and assist on device design and to optimize sensing characteristics. The sensing element of the device was fabricated using polyimide micromachining with embedded thin-metallic wires and placed into a knee prosthesis. The device was evaluated experimentally in a mechanical knee simulator using static and dynamic axial load conditions similar to those encountered in vivo. Results indicates the sensor is capable of measuring the strain associated to the total axial forces in the range of approximately 4 times body weight with a good sensitivity and accuracy for events happening within 1 s time window.

Highlights

Total Knee Arthroplasty (TKA) is a widely used surgical procedure to replace a damaged knee joint by an artificial knee implant (Kirking et al 2006)
Negative strain values, associated with compressive strain in the x-axis direction are visible on the surroundings of the tensile region. From this investigation we could identify a xz-plane with good strain symmetry at nearly 1/3 of the ultra-high-molecular-weight polyethylene (UHMWPE) height, these region is suitable for positioning the sensors
The strain sensors were defined to be located in the compressive strain region with is center located at 13 mm along the UHMWPE insert width, while passive strain sensors will be located in regions of zero strain to compensate for overall temperature variations

Summary

Introduction

Total Knee Arthroplasty (TKA) is a widely used surgical procedure to replace a damaged knee joint by an artificial knee implant (Kirking et al 2006). The age at the time of primary TKA is decreasing it is critical to ensure operation success and to access the status of the artificial knee implant along its lifetime to minimize the possibilities of revision surgery and to maximize the longevity of the implant (Heinlein et al 2009). If FEA contributes to extend the life of the orthopedic implant other factors significantly impact on the prosthesis lifetime. Several different artificial knee implant designs are commercially available but misalignment, leading to knee imbalance, and wearing are still the major reasons for revision. Forces acting directly on the artificial joint affect the knee balance and induce wear of the bearing surface, which is associated to prosthesis loosening, Biomed Microdevices (2013) 15:831–839 impacting on the implant lifetime (D’Lima et al 2006)

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