3D real time methodology monitoring cement failures in THA

Abstract

The present work proposed a methodology to monitor cement microcrack formation in the cemented femoral stem construct using the acoustic emission technique. This technique provides a unique means to automatically tally the number of microcracks, to visualize microcrack distribution, and to animate the progress of crack formation in a given time window of a fatigue test. In this work, the formulation of microcrack source location was derived and a computer program was developed specifically for the proposed application. The program was validated using computer simulation and standard pencil lead break tests. It was found that the mathematical errors complied with the acceptable minimal error. Based on the pencil lead break tests, the average technical error used to estimate the resolution of this technique was 4.7 mm at the present stage. The program was then used to monitor the fatigue damage in precoated cemented femoral hip constructs loaded for a total of more than five million cycles. Two types of microcrack activities were observed in the experiments: Type I and Type II microcracks. A Type I microcrack was a crack that was captured by four or more sensors, and therefore its location was defined uniquely by a set of coordinates. A Type II microcrack was a crack that was captured by three or less sensors, therefore it was unlocatable. Both counts of Type I and Type II microcrack were tallied with respect to the day of fatigue tests. Acoustic emission microcrack graphs were used to visualize the distribution of Type I microcracks in the construct. It was found that the Type I microcracks distributed mainly over the proximal third of the stem. The amount of microcrack events decreased significantly as the number of loading cycles increased.

Real time monitoring of progressive damage during loading of a simplified total hip stem construct using embedded acoustic emission sensors

“…Since these pulses originated closer to the bone cement layer than the pencil lead break test performed on the external surface of the Tufnol, it is hypothesised that location calibrations based on the embedded pulses would be more accurate. Qi et al [26] attempted to use AE to monitor damage accumulation within the bone cement layer surrounding a femoral stem implanted within an epoxy femur. Their location algorithm was calibrated using pencil lead-break tests on the external surface of the representative femur.…”

“…Mavrogordato et al [14] also investigated AE during polymerisation of acrylic polymer materials and were able to detect and locate cracking induced during polymerisation which was corroborated visually using micro-CT prior to the application of any load. Qi et al [15] used AE in an attempt to detect and locate micro-cracking from within a complete stem construct with promising results. The authors were able to detect and locate damage occurring within the bone cement layer, although the 3D location accuracy of their results was questioned in view of the fact that some events were located in free space [17].…”

“…In 1995, Kohn [7] identified the technique as possessing 'many of the qualities of an ideal damage-monitoring technique', and the technique has been used successfully in recent years to investigate wear mechanisms of metal-on-metal hip resurfacing components [8] and aid understanding of failure mechanisms and damage accumulation in bone cement during de-bonding of the cement-metal interface [9,10], fatigue loading [11,12], pre-load cracking during polymerisation [13,14] and to describe and locate damage within an entire stem construct [15]. Kohn [7] and Browne et al [16] have compiled comprehensive review papers of the AE technique and its uses within bioengineering materials research.…”

Nondestructive evaluation of bone cement and bone cement/metal interface failure

“…13,14,17,25,26 Few studies have combined acoustic emission and ultrasonics to assess implant integrity. Vaidya and Raju 27 defined a stress wave factor when using an acoustic-ultrasonic technique to differentiate between a loose and wellfixed prosthesis.…”

Principles of Material Structural Change Informatics to Characterize and Evaluate Damage of Materials in Service

“…The performance data can be measured using a multitude of nondestructive techniques. The informatics of material structural changes are invaluable as demonstrated by structural health monitoring of both civil and mechanical infrastructures for evaluation and prediction of its service life [10][11][12][13][14]: to diagnose faulty operations in machine and mechanical components [15][16][17][18][19], to diagnose the integrity of implanted arthroplasties [20][21][22][23], and to characterize material performance [2,[24][25][26][27]. Of particular note is that the success of most of the mentioned applications does not dependent on the knowledge of stress or strain.…”