Computational Parametric Studies for Preclinical Evaluation of Total Knee Replacements

Mell, Steven P.; Fullam, Spencer; Wimmer, Markus A.

doi:10.1007/978-3-030-43195-2_6

Cited by 4 publications

(7 citation statements)

References 48 publications

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“…2,3 Progress has been made to understand material and design factors, as well as important patient factors such as age and activity. 2,4 Although, there have been computational biomechanics models that demonstrated the influence of surgical alignment on tibiofemoral kinematics, kinetics, and wear, 5,6 with the exception of grossly malpositioned components, there is little knowledge about the impact of implant positioning on wear. Part of the reason for this paucity is the difficulty to reliably measure tibial liner wear.…”

Section: Introductionmentioning

confidence: 99%

Joint line elevation and tibial slope are associated with increased polyethylene wear in cruciate‐retaining total knee replacement

Pourzal

Cip²,

Rad

et al. 2020

Journal Orthopaedic Research

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The purpose of this retrieval study was to determine the effect of implant positioning on wear, taking patient‐related factors into account. Therefore, the volumetric material loss of 59 retrieved tibial liners was quantitatively determined using a coordinate measuring‐machine. All retrievals were made of the same polyethylene and design by a single manufacturer. Using time in‐situ and linear regression, a wear rate for each liner was determined and corrected for bedding‐in. Backside damage was qualitatively scored. The following implant positioning parameters were obtained from radiographs: anatomical lateral‐distal femoral angle, anatomical medial‐proximal tibial angle, femoral tilt angle, and posterior tibial slope. The patella position was assessed by the Blackburne‐Peel index and the Insall‐Salvati ratio. Unlike the Insall‐Salvati ratio, the Blackburne‐Peel index is known to detect surgical joint line elevation. Using general linear modeling the most impactful factors on wear rate and backside damage was determined, thereby taking patient demographic factors into account. The mean volumetric wear rate was 11.6 mm3/y. Wear decreased with older age (P = .021) and female sex (P = .001). The wear rate increased with joint line elevation as indicated from a decreased Blackburne‐Peel index (P = .019), and increased with increased posterior tibial slope (P = .026). The backside damage score also increased with joint line elevation (P = .036). A Blackburne‐Peel index decrease of 0.1, signifying joint line elevation, was found to increase the wear rate by 1.8 mm3/y and increase back‐sided wear. A high tibial slope (>7°) led to a 9.3 mm3/y increase in wear rate compared with a low tibial slope (<3°). The results of this study demonstrate that tibial liner positioning has a significant impact on polyethylene wear with potential implications on osteolysis over time.

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Section: Introductionmentioning

confidence: 99%

Joint line elevation and tibial slope are associated with increased polyethylene wear in cruciate‐retaining total knee replacement

Pourzal

Cip²,

Rad

et al. 2020

Journal Orthopaedic Research

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“…There was a significant difference in wear rates between the lubricants, F(3, 24) = 46.72, p < 0.001. The estimated wear rate was 11.27 mg/MC (95% CI [9.21, 13.3 [26] wear tests run on the same machine with the same loading and motion profiles, but using a standard calf serum-based solution, had a higher wear rate than Low FA/BSA but a lower rate than pure BSA. This data and the calculated specific wear rates are shown in Table 2.…”

Section: Resultsmentioning

confidence: 99%

“…The wear rates and mechanisms of this study agree well with simulator studies. Using POD wear tests with the same load and kinematic input as used here, Mell et al [26] were able to predict knee simulator wear rates computationally. In addition, the observed wear features (particularly the protrusions) have been observed during hip simulator wear testing, as well as on in vivo components after retrieval [31].…”

Section: Resultsmentioning

confidence: 99%

Competitive Binding of Bilirubin and Fatty Acid on Serum Albumin Affects Wear of UHMWPE

Fullam

Scholl

et al. 2020

Lubricants

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Total Joint Replacement (TJR) devices undergo standardized wear testing in mechanical simulators while submerged in a proteinaceous testing solution to mimic the environmental conditions of artificial joints in the human body. Typically, bovine calf serum is used to provide the required protein content. However, due to lot-to-lot variability, an undesirable variance in testing outcome is observed. Based on an earlier finding that yellowish-orange serum color saturation is associated with wear rate, we examined potential sources of this variability, by running a comparative wear test with bilirubin; hemin; and a fatty acid, oleic acid, in the lubricant. All these compounds readily bind to albumin, the most abundant protein in bovine serum. Ultrahigh molecular weight polyethylene (UHMWPE) pins were articulated against CoCrMo discs in a pin-on-disc tribometer, and the UHMWPE wear rates were compared between lubricants. We found that the addition of bilirubin increased wear by 121%, while hemin had a much weaker, insignificant effect. When added at the same molar ratio as bilirubin, the fatty acid tended to reduce wear. Additionally, there was a significant interaction with respect to bilirubin and hemin in that UHMWPE wear rate decreased with increasing fatty acid concentration. We believe the conformational change in albumin by binding bilirubin makes it more likely to form molecular bridges between UHMWPE and the metal counterface, thus increasing adhesive wear. However, fatty acids compete for binding sites on albumin, and can prevent this conformational change. Hence, the protein is stabilized, and the chance for albumin to form bridges is lowered. Ultimately, UHMWPE wear rate is driven by the competitive binding of bilirubin and fatty acid to albumin.

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“…A previously published computational framework 16,17,35 was used to perform a parametric study to investigate the influence of variability in kinematic and kinetic input waveforms on wear variability. The framework leverages a finite element analysis (FEA) model of TKR wear and contact and has been previously validated against several independent experimental tests.…”

Section: Methodsmentioning

confidence: 99%

“…The framework leverages a finite element analysis (FEA) model of TKR wear and contact and has been previously validated against several independent experimental tests. 16,17,35 The FEA model used is of a NexGen CR TKR (Zimmer-Biomet, Warsaw, IN) with the femoral component modeled as a rigid body using 4627 quadratic surface elements. The polyethylene tibial insert is modeled as a deformable body using the J2 plasticity model with an elastic modulus of 1051 MPa and a Poisson's ratio of 0.46 36 and is comprised of 78,108 linear hexahedral elements.…”

Section: Methodsmentioning

confidence: 99%

Sensitivity of total knee replacement wear to variability in motion and load input: A parametric finite element analysis study

Mell

Wimmer

2020

Journal Orthopaedic Research

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Polyethylene wear remains a contributor to long term failure in total knee replacements (TKRs). Advances in materials have improved polyethylene wear rates, therefore further wear reductions require a better understanding of patient‐specific factors that lead to wear. Variability of gait within patients is considerable and could lead to significant variability in wear rates that cannot be predicted by standard testing methods. An in‐silico study was performed to investigate the influence of gait variability on TKR polyethylene wear. Nine characteristic peaks within the load and motion profiles used for TKR wear testing were varied 75% to 125% from baseline (ISO‐14243‐3:2014) to generate 310 unique waveforms. Wear was calculated for 1‐million cycles using a finite element TKR wear model. From the results, a surrogate model was developed using multiple linear regression, and used to predict how wear changes due to dispersion of motion and force peaks within a) ±5%, the maximum allowable input tolerance of ISO, and b) ±25%, more reflective of patient gait inter‐variability. The range of wear within the ±5% tolerance was 0.65 mm3/million cycles and was 3.24 mm3/million cycles within the ±25% variability more in line with the dispersion observed within patients. Although no one kinematic or kinetic peak dominated variability in TKR volumetric wear, variability within flexion/extension peaks were the largest contributor to wear rate variability. Interaction between the peaks of different waveforms was also important. This study, and future studies incorporating patient‐specific data, could help to explain the connection between patient‐specific gait factors and wear rates.

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Computational Parametric Studies for Preclinical Evaluation of Total Knee Replacements

Cited by 4 publications

References 48 publications

Joint line elevation and tibial slope are associated with increased polyethylene wear in cruciate‐retaining total knee replacement

Joint line elevation and tibial slope are associated with increased polyethylene wear in cruciate‐retaining total knee replacement

Competitive Binding of Bilirubin and Fatty Acid on Serum Albumin Affects Wear of UHMWPE

Sensitivity of total knee replacement wear to variability in motion and load input: A parametric finite element analysis study

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