Primary Stability Recognition of the Newly Designed Cementless Femoral Stem Using Digital Signal Processing

Abstract

Stress shielding and micromotion are two major issues which determine the success of newly designed cementless femoral stems. The correlation of experimental validation with finite element analysis (FEA) is commonly used to evaluate the stress distribution and fixation stability of the stem within the femoral canal. This paper focused on the applications of feature extraction and pattern recognition using support vector machine (SVM) to determine the primary stability of the implant. We measured strain with triaxial rosette at the metaphyseal region and micromotion with linear variable direct transducer proximally and distally using composite femora. The root mean squares technique is used to feed the classifier which provides maximum likelihood estimation of amplitude, and radial basis function is used as the kernel parameter which mapped the datasets into separable hyperplanes. The results showed 100% pattern recognition accuracy using SVM for both strain and micromotion. This indicates that DSP could be applied in determining the femoral stem primary stability with high pattern recognition accuracy in biomechanical testing.

Characterization of Femoral Component Initial Stability and Cortical Strain in a Reduced Stem-Length Design

“…Investigations in the primary stability of THA femoral components have utilized bench 246 testing in cadaveric [23,24,25,31,32] and composite [18,[33][34][35][36][37][38] femur specimens, as 247 well as finite element analysis [23,24,34,39,40] in reporting a wide range of stability 248 data, dependent on measurement techniques, loading profiles, and setup design. Prior in 249 vitro THA micromotion studies have primarily used linear variable differential 250 transformer (LVDT) or differential variable reluctance transducer (DVRT) sensors to 251 quantify implant stability: instrumentation which typically require complex 252 instrumentation to be rigidly fixed to the specimens and allow for displacement 253 measurements at a single point in space [31, 33-37, 40-43, 48].…”

Finite element analysis of a hybrid corrugated hip implant for stability and loading during gait phases

“…These observations can be attributed to the corrugated implant design, which provides a greater surface area, and transfers higher concentrated strains to the femoral head at higher loads. The maximum and minimum micro-motions recorded on the implant for the gait cycle were 7.73 μm and 1.25 μm, respectively, which were much less than the 40 μm thresholds [20].…”

“…Jiang et al [43] performed the computational study of the acetabular cup of the hip implant with different material properties during the gait cycle. In dynamic analysis maximum deformation was observed to be 100 μm which was 150% more than the stability of THR [20]. These observations can be attributed to the corrugated implant design, which provides a greater surface area, and transfers higher concentrated strains to the femoral head at higher loads.…”

“…Common issues that arise with the femoral stem include stress shielding (i.e., negative effect of implants where stress is absorbed by the implant rather than the existing bone), instability or micro-motion between implant and femur, and bone resorption, which consequently lead to discomfort and pain [18,19]. Years of surgical observations have reported that the interfacial micromotion between the stem of the implant and the enclosing femoral cavity should be below 40 μm to avoid wear and promote primary bone ingrowth while preventing fibrous tissue formation [20]. However, to date, none of the THR based implants can produce such minimal interfacial micro-motions (i.e., high stability), which is one of the leading causes of THR based surgical failures [21].…”

Comparison of periprosthetic femoral fracture torque and strain pattern of three types of femoral components in experimental model

“…We measured surface strain distribution using triaxial rosettes (UFRA-5-350-17, Tokyo Sokki Kenkyujo, Japan) medially and laterally at the metaphyseal region according to a previous report. 11 The strain gauge positions on the femur surface were determined as in Figure 3a. The strain signal is measured from nine sections around the metaphyseal-diaphyseal region defined as follows: greater trochanter (Figure 3b: sections 1, 2, and 3), proximal medial calcar (Figure 3c: sections 4 and 5), anterior (Figure 3d: sections 6 and 7), and posterior (Figure 3e: sections 8 and 9).…”