A novel formulation for scratch-based wear modelling in total hip arthroplasty

Abstract

Damage to the femoral head in total hip arthroplasty often takes the form of discrete scratches, which can lead to dramatic wear acceleration of the polyethylene (PE) liner. Here, a novel formulation is reported for finite element analysis of wear acceleration due to scratch damage. A diffused-light photography technique was used to globally locate areas of damage, providing guidance for usage of high-magnification optical profilometry to determine individual scratch morphology. This multiscale image combination allowed comprehensive input of scratch-based damage patterns to a finite element (FE) Archard wear model, to determine the wear acceleration associated with specific retrieval femoral heads. The wear algorithm imposed correspondingly elevated wear factors on areas of PE incrementally overpassed by individual scratches. Physical validation was provided by agreement with experimental data for custom-ruled scratch patterns. Illustrative wear acceleration results are presented for four retrieval femoral heads.

THA Retrievals: The Need to Mark the Anatomic Orientation of the Femoral Head

“…Computational wear simulation avoids these problems, and the FE wear formulations used in this study have been well-validated against physical wear simulations [8, 10, 11]. For femoral heads that were undamaged, had scratches, or had a roughened area (similar to a scrape), wear calculation errors between the physical and computational models were less than 5% [11], 10% [8], and 10% [10], respectively. These validations were based on conventional PE; similar wear acceleration results, relative to undamaged cases, would be expected for highly crosslinked PE.…”

“…These damage data were then used to simulate femoral head damage in a damage-feature-based FE wear model [8]. Femoral head scratches and scrapes, along with their corresponding lip heights and R a values, were modeled at their respective damage locations.…”

“…Femoral head scratches and scrapes, along with their corresponding lip heights and R a values, were modeled at their respective damage locations. A finite element model for PE liner wear, experimentally validated for conventional polyethylene [8, 10, 11], was then implemented in ABAQUS v6.9.1, using the adaptive meshing capabilities of the UMESHMOTION subroutine. PE liner wear was computed using the Archard wear formula [12], which calculates the spatial distribution of wear depth as a function of local contact pressure, sliding distance, and a wear coefficient based on the tribological properties of the surfaces in contact.…”

“…For example, this knowledge would appear to be essential for accurate calculation of liner wear. Recent advances in damage-feature-based finite element (FE) modeling allow for quick and efficient evaluation of patient-specific femoral head damage [7, 8]. The hypothesis of this study was therefore that rotational orientation of damage on retrieved femoral heads has a marked influence on the volumetric wear rate of the opposing polyethylene liner, as predicted by finite element analysis.…”

Encoding Scratch and Scrape Features for Wear Modeling of Total Joint Replacements

“…For computing damage-induced wear rate acceleration, the Archard wear coefficient for the baseline undamaged surface is elevated for polyethylene areas that are overpassed by the counterface damage features. For scratches, there is an approximately exponential relationship [20] between scratch lip height ( h L ) and the scaling factor ( k inc ) for wear coefficient elevation, the specific parameters being $\begin{array}{c}{k}_{\text{inc}}=\mathrm{58.0985}-\mathrm{58.0985}·e^{-\mathrm{0.2237}\ast h_L}\end{array}$ when lip height is expressed in μ m. For the case of scrapes, the R a values were converted to wear coefficient scaling factors using a power law relationship [16], the specific parameters being $\begin{array}{c}{k}_{\text{inc}}=\mathrm{37.538}·{\left(R_a\right)}^{\mathrm{1.2}}\end{array}$ for R a measurements in μ m.…”