scholarly journals Biomechanical Effect of UHMWPE and CFR-PEEK Insert on Tibial Component in Unicompartmental Knee Replacement in Different Varus and Valgus Alignments

Materials ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3345
Author(s):  
Yong-Gon Koh ◽  
Hyoung-Taek Hong ◽  
Kyoung-Tak Kang
Keyword(s):  
Knee Replacement ◽  
Contact Stress ◽  
Tibial Component ◽  
Element Model ◽  
Von Mises Stress ◽  
Unicompartmental Knee Replacement ◽  
Neutral Position ◽  
Unicompartmental Knee ◽  
Von Mises ◽  
Valgus Alignment

The current study aims to analyze the biomechanical effects of ultra-high molecular weight polyethylene (UHMWPE) and carbon-fiber-reinforced polyetheretherketone (CFR-PEEK) inserts, in varus/valgus alignment, for a tibial component, from 9° varus to 9° valgus, in unicompartmental knee replacement (UKR). The effects on bone stress, collateral ligament force, and contact stress on other compartments were evaluated under gait cycle conditions, by using a validated finite element model. In the UHMWPE model, the von Mises’ stress on the cortical bone region significantly increased as the tibial tray was in valgus >6°, which might increase the risk of residual pain, and when in valgus >3° for CFR-PEEK. The contact stress on other UHMWPE compartments decreased in valgus and increased in varus, as compared to the neutral position. In CFR-PEEK, it increased in valgus and decreased in varus. The forces on medial collateral ligaments increased in valgus, when compared to the neutral position in UHMWPE and CFR-PEEK. The results indicate that UKR with UHMWPE showed positive biomechanical outputs under neutral and 3° varus conditions. UKR with CFR-PEEK showed positive biomechanical outputs for up to 6° varus alignments. The valgus alignment should be avoided.

Tibial component overhang following unicompartmental knee replacement—Does it matter?

The Knee ◽  
2009 ◽  
Vol 16 (5) ◽  
pp. 310-313 ◽  
Author(s):  
R. Chau ◽  
A. Gulati ◽  
H. Pandit ◽  
D.J. Beard ◽  
A.J. Price ◽  
...  
Keyword(s):  
Knee Replacement ◽  
Tibial Component ◽  
Unicompartmental Knee Replacement ◽  
Unicompartmental Knee

Mobile-bearing lateral unicompartmental knee replacement with the Oxford domed tibial component

2012 ◽  
Vol 94-B (10) ◽  
pp. 1356-1361 ◽  
Author(s):  
M. R. Streit ◽  
T. Walker ◽  
T. Bruckner ◽  
C. Merle ◽  
J. P. Kretzer ◽  
...  
Keyword(s):  
Knee Replacement ◽  
Tibial Component ◽  
Mobile Bearing ◽  
Unicompartmental Knee Replacement ◽  
Unicompartmental Knee

scholarly journals Valgus subsidence of the tibial component in cementless Oxford unicompartmental knee replacement

2014 ◽  
Vol 96-B (3) ◽  
pp. 345-349 ◽  
Author(s):  
A. D. Liddle ◽  
H. G. Pandit ◽  
C. Jenkins ◽  
P. Lobenhoffer ◽  
W. F. M. Jackson ◽  
...  
Keyword(s):  
Knee Replacement ◽  
Tibial Component ◽  
Unicompartmental Knee Replacement ◽  
Unicompartmental Knee

Midterm results after unicompartmental knee replacement with all-polyethylene tibial component: a single surgeon experience

2016 ◽  
Vol 136 (9) ◽  
pp. 1303-1307 ◽  
Author(s):  
Nael Hawi ◽  
Jochen Plutat ◽  
Daniel Kendoff ◽  
Eduardo M. Suero ◽  
Michael B. Cross ◽  
...  
Keyword(s):  
Knee Replacement ◽  
Tibial Component ◽  
Unicompartmental Knee Replacement ◽  
Midterm Results ◽  
Unicompartmental Knee ◽  
Surgeon Experience

scholarly journals Optimal interference of the tibial component of the cementless Oxford Unicompartmental Knee Replacement

2018 ◽  
Vol 7 (3) ◽  
pp. 226-231 ◽  
Author(s):  
S. Campi ◽  
S. J. Mellon ◽  
D. Ridley ◽  
B. Foulke ◽  
C. A. F. Dodd ◽  
...  
Keyword(s):  
Polyurethane Foam ◽  
Knee Replacement ◽  
Tibial Component ◽  
Testing Machine ◽  
Unicompartmental Knee Replacement ◽  
Materials Testing ◽  
Interference Fit ◽  
Pull Out ◽  
Damage And Fracture ◽  
Unicompartmental Knee

Objectives The primary stability of the cementless Oxford Unicompartmental Knee Replacement (OUKR) relies on interference fit (or press fit). Insufficient interference may cause implant loosening, whilst excessive interference could cause bone damage and fracture. The aim of this study was to identify the optimal interference fit by measuring the force required to seat the tibial component of the cementless OUKR (push-in force) and the force required to remove the component (pull-out force). Materials and Methods Six cementless OUKR tibial components were implanted in 12 new slots prepared on blocks of solid polyurethane foam (20 pounds per cubic foot (PCF), Sawbones, Malmo, Sweden) with a range of interference of 0.1 mm to 1.9 mm using a Dartec materials testing machine HC10 (Zwick Ltd, Herefordshire, United Kingdom) . The experiment was repeated with cellular polyurethane foam (15 PCF), which is a more porous analogue for trabecular bone. Results The push-in force progressively increased with increasing interference. The pull-out force was related in a non-linear fashion to interference, decreasing with higher interference. Compared with the current nominal interference, a lower interference would reduce the push-in forces by up to 45% (p < 0.001 One way ANOVA) ensuring comparable (or improved) pull-out forces (p > 0.05 Bonferroni post hoc test). With the more porous bone analogue, although the forces were lower, the relationship between interference and push-in and pull-out force were similar. Conclusions This study suggests that decreasing the interference fit of the tibial component of the cementless OUKR reduces the push-in force and can increase the pull-out force. An optimal interference fit may both improve primary fixation and decrease the risk of fracture. Cite this article: S. Campi, S. J. Mellon, D. Ridley, B. Foulke, C. A. F. Dodd, H. G. Pandit, D. W. Murray. Optimal interference of the tibial component of the cementless Oxford Unicompartmental Knee Replacement. Bone Joint Res 2018;7:226–231. DOI: 10.1302/2046-3758.73.BJR-2017-0193.R1.

Does the type of tibial component affect mechanical alignment in unicompartmental knee replacement?

2013 ◽  
Vol 21 (1) ◽  
pp. 81-85 ◽  
Author(s):  
Eduardo M. Suero ◽  
Mustafa Citak ◽  
Innocent U. Njoku ◽  
Andrew D. Pearle
Keyword(s):  
Knee Replacement ◽  
Tibial Component ◽  
Unicompartmental Knee Replacement ◽  
Mechanical Alignment ◽  
Unicompartmental Knee

scholarly journals Effects of intracorneal ring segments implementation technique and design on corneal biomechanics and keratometry in a personalized computational analysis

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Niksa Mohammadi Bagheri ◽  
Mahmoud Kadkhodaei ◽  
Shiva Pirhadi ◽  
Peiman Mosaddegh
Keyword(s):  
Clinical Data ◽  
Three Dimensional ◽  
Element Model ◽  
Von Mises Stress ◽  
Patient Specific ◽  
Average Error ◽  
Constant Thickness ◽  
Arc Length ◽  
Implementation Techniques ◽  
Von Mises

AbstractThe implementation of intracorneal ring segments (ICRS) is one of the successfully applied refractive operations for the treatment of keratoconus (kc) progression. The different selection of ICRS types along with the surgical implementation techniques can significantly affect surgical outcomes. Thus, this study aimed to investigate the influence of ICRS implementation techniques and design on the postoperative biomechanical state and keratometry results. The clinical data of three patients with different stages and patterns of keratoconus were assessed to develop a three-dimensional (3D) patient-specific finite-element model (FEM) of the keratoconic cornea. For each patient, the exact surgery procedure definitions were interpreted in the step-by-step FEM. Then, seven surgical scenarios, including different ICRS designs (complete and incomplete segment), with two surgical implementation methods (tunnel incision and lamellar pocket cut), were simulated. The pre- and postoperative predicted results of FEM were validated with the corresponding clinical data. For the pre- and postoperative results, the average error of 0.4% and 3.7% for the mean keratometry value ($$\text {K}_{\text{mean}}$$ K mean ) were predicted. Furthermore, the difference in induced flattening effects was negligible for three ICRS types (KeraRing segment with arc-length of 355, 320, and two separate 160) of equal thickness. In contrast, the single and double progressive thickness of KeraRing 160 caused a significantly lower flattening effect compared to the same type with constant thickness. The observations indicated that the greater the segment thickness and arc-length, the lower the induced mean keratometry values. While the application of the tunnel incision method resulted in a lower $$\text {K}_{\text{mean}}$$ K mean value for moderate and advanced KC, the induced maximum Von Mises stress on the postoperative cornea exceeded the induced maximum stress on the cornea more than two to five times compared to the pocket incision and the preoperative state of the cornea. In particular, an asymmetric regional Von Mises stress on the corneal surface was generated with a progressive ICRS thickness. These findings could be an early biomechanical sign for a later corneal instability and ICRS migration. The developed methodology provided a platform to personalize ICRS refractive surgery with regard to the patient’s keratoconus stage in order to facilitate the efficiency and biomechanical stability of the surgery.

Theoretical analysis of a rolling-sliding elastohydrodynamic lubrication line contact with a subsurface inclusion

2019 ◽  
Vol 233 (8) ◽  
pp. 1197-1207
Author(s):  
Armando Félix Quiñonez ◽  
Guillermo E Morales Espejel
Keyword(s):  
Elastohydrodynamic Lubrication ◽  
Element Model ◽  
Von Mises Stress ◽  
Transient Effects ◽  
Mean Velocity ◽  
The Matrix ◽  
Soft Inclusion ◽  
The Mean ◽  
Von Mises ◽  
Fully Coupled

This work investigates the transient effects of a single subsurface inclusion over the pressure, film thickness, and von Mises stress in a line elastohydrodynamic lubrication contact. Results are obtained with a fully-coupled finite element model for either a stiff or a soft inclusion moving at the speed of the surface. Two cases analyzed consider the inclusion moving either at the same speed as the mean velocity of the lubricant or moving slower. Two additional cases investigate reducing either the size of the inclusion or its stiffness differential with respect to the matrix. It is shown that the well-known two-wave elastohydrodynamic lubrication mechanism induced by surface features is also applicable to the inclusions. Also, that the effects of the inclusion become weaker both when its size is reduced and when its stiffness approaches that of the matrix. A direct comparison with predictions by the semi-analytical model of Morales-Espejel et al. ( Proc IMechE, Part J: J Engineering Tribology 2017; 231) shows reasonable qualitative agreement. Quantitatively some differences are observed which, after accounting for the semi-analytical model's simplicity, physical agreement, and computational efficiency, may then be considered as reasonable for engineering applications.

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