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Sirimamilla A, Rimnac CM. Crack initiation from a clinically relevant notch in a highly-crosslinked UHMWPE subjected to static and cyclic loading. J Mech Behav Biomed Mater 2018; 91:366-372. [PMID: 30658250 DOI: 10.1016/j.jmbbm.2018.12.032] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Revised: 12/05/2018] [Indexed: 10/27/2022]
Abstract
Crosslinked Ultra High Molecular Weight Polyethylene (UHMWPE), which is used as a bearing material in total joint replacement components, is subjected to static and cyclic loads in vivo. Resistance to crack initiation from a notch as a function of static and cyclic loads is not well understood for crosslinked UHMWPE. This study estimated the resistance of crosslinked UHMWPE (crosslinked with 100 kGy gamma radiation and remelted to extinguish free radicals) to crack initiation for a clinically relevant notch under both static and cyclic loading conditions. For cyclic loading, four frequencies were applied with a sine waveform and two frequencies were applied with a square waveform to independently estimate the effect of frequency and rate of loading on crack initiation. Crack initiation time and cycles to crack initiation were determined. Crack initiation time for fatigue loading conditions was substantially lower compared to static loading conditions. Crack initiation time decreased with an increase in test frequency. A square wave resulted in shorter crack initiation time compared to a sine wave. The results suggest that crosslinked UHMWPE is more resistant to crack initiation from a notch under static loading conditions compared to fatigue loading conditions.
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Affiliation(s)
- Abhi Sirimamilla
- Microsoft Hardware Group, One Microsoft Way, Redmond, WA 98052, United States.
| | - Clare M Rimnac
- Mechanical and Aerospace Engineering Department, Case Western Reserve University, Cleveland, OH 44106, United States.
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Wang Y, Song M, Xu Y, He X, Zhu Y. Absorbable scaphoid screw development: a comparative study on biomechanics. Ther Clin Risk Manag 2016; 12:643-50. [PMID: 27217756 PMCID: PMC4853148 DOI: 10.2147/tcrm.s99024] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
BACKGROUND The scaphoid is critical for maintaining the stability and movement of the wrist joints. This study aimed to develop a new internal fixator absorbable scaphoid screw (ASS) for fixation of the scaphoid waist after fracture and to test the biomechanical characteristics of ASS. MATERIALS AND METHODS An ASS was prepared using polylactic acids and designed based on scaphoid measurements and anatomic features. Twenty fractured scaphoid waist specimens were randomly divided into experimental and control groups (n=10/group). Reduction and internal fixation of the scaphoid were achieved with either Kirschner wires (K-wires) or ASS. A moving target simulator was used to test palmar flexion and dorsal extension, with the range of testing (waist movement) set from 5° of palmar flexion to 25° of dorsal extension. Flexion and extension were repeated 2,000 times for each specimen. Fracture gap displacements were measured with a computerized tomography scanning. Scaphoid tensile and bending strengths were measured by using a hydraulic pressure biomechanical system. RESULTS Prior to biomechanical fatigue testing, fracture gap displacements were 0.16±0.02 mm and 0.22±0.02 mm in the ASS and K-wire groups, respectively. After fatigue testing, fracture gap displacements in the ASS and the K-wire groups were 0.21±0.03 mm and 1.52±0.07 mm, respectively. The tensile strengths for the ASS and K-wire groups were 0.95±0.02 MPa and 0.63±0.02 MPa, respectively. CONCLUSION Fixation using an ASS provided sufficient mechanical support for the scaphoid after fracture.
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Affiliation(s)
- Yi Wang
- Department of Orthopedic Surgery, Kunming General Hospital, Chengdu Military Command, People's Liberation Army, Kunming, Yunnan, People's Republic of China
| | - Muguo Song
- Department of Orthopedic Surgery, Kunming General Hospital, Chengdu Military Command, People's Liberation Army, Kunming, Yunnan, People's Republic of China
| | - Yongqing Xu
- Department of Orthopedic Surgery, Kunming General Hospital, Chengdu Military Command, People's Liberation Army, Kunming, Yunnan, People's Republic of China
| | - Xiaoqing He
- Department of Orthopedic Surgery, Kunming General Hospital, Chengdu Military Command, People's Liberation Army, Kunming, Yunnan, People's Republic of China
| | - YueLiang Zhu
- Department of Orthopedic Surgery, Kunming General Hospital, Chengdu Military Command, People's Liberation Army, Kunming, Yunnan, People's Republic of China
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The mechanical properties of the ultra high molecular weight polyethylene grafted with 3-dimethy (3-(N-methacryamido) propyl) ammonium propane sulfonate. J Mech Behav Biomed Mater 2014; 35:18-26. [PMID: 24727573 DOI: 10.1016/j.jmbbm.2014.03.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2013] [Revised: 03/07/2014] [Accepted: 03/09/2014] [Indexed: 11/23/2022]
Abstract
Ultra-high molecular weight polyethylene (UHMWPE) powder was modified with a zwitterion monomer with good biocompatibility of MPDSAH (3-dimethy (3-(N-methacryamido) propyl) ammonium propane sulfonate) by UV irradiation and then hot pressed. The microstructure and mechanical properties of modified UHMWPE are investigated. The results show that the structure of powder and bulk materials has been changed. The modified powders have more filaments than that of untreated. The surface of modified bulk materials is more rough and displays the granular protuberances which have the random loose arrangement compared with untreated UHMWPE. The crystallinity, uniaxial tensile and compressive properties decreased after grafting. Ultimate elongations decrease with the increase of the monomer concentration and are higher than 300% which is recommended by ASTM and ISO except the sample with 0.45mol/L MPDSAH. The friction coefficient of modified UHMWPE is lower than that of the untreated UHMWPE and it decreases gradually with the increase of monomer concentration. The wear rates have been decreased and the wear resistance has been improved under saline and distilled water lubrication.
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Sobieraj MC, Murphy JE, Brinkman JG, Kurtz SM, Rimnac CM. Monotonic and fatigue behavior of five clinically relevant conventional and highly crosslinked UHMWPEs in the presence of stress concentrations. J Mech Behav Biomed Mater 2013; 28:244-53. [PMID: 24008137 DOI: 10.1016/j.jmbbm.2013.07.024] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2013] [Revised: 07/14/2013] [Accepted: 07/26/2013] [Indexed: 10/26/2022]
Abstract
Five formulations of clinically relevant UHMWPE (conventional, moderately crosslinked annealed and remelted, and highly crosslinked annealed and remelted) were investigated in a physiologically relevant environment. Their monotonic stress-strain behavior in the presence of notches of two different severities and at two different displacement rates was examined using a custom developed video based system. It was found that both an elevation of yield stress and a truncation of orientation hardening took place under monotonic loading and that these changes were found to be material and elastic stress concentration factor dependent. The fatigue behavior of these materials was examined using the same geometries via a stress-life approach with failure defined as fracture of the specimen in the 1000 to 100,000 cycle lifetime range. The results were modeled using the Basquin relationship (σ=AN(b), where σ=stress and N=lifetime, and A and b are experimentally derived constants) via maximum likelihood estimation methods to account for specimen runout (no failure at 250,000cycles). The conventional material was found to have a greater slope, b, and intercept, A, than the crosslinked materials as well as appearing to have less variance in its failure distributions.
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Affiliation(s)
- Michael C Sobieraj
- Musculoskeletal Mechanics and Materials Laboratories, Department of Mechanical and Aerospace Engineering, Case Western Reserve University, 10900 Euclid Ave, Cleveland, OH, USA.
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Deng Y, Xiong D, Wang K. Biotribological properties of UHMWPE grafted with AA under lubrication as artificial joint. JOURNAL OF MATERIALS SCIENCE. MATERIALS IN MEDICINE 2013; 24:2085-2091. [PMID: 23793532 DOI: 10.1007/s10856-013-4970-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Accepted: 05/31/2013] [Indexed: 06/02/2023]
Abstract
Osteolysis caused by wear particles from polyethylene in the artificial hip joints is a serious issue. In order to endow the low friction and wear of the bearing surface of ultra-high molecular weight polyethylene (UHMWPE) artificial joint for a longer term, hydrophilic acrylic acid (AA) was grafted on UHMWPE powders with the method of ultraviolet irradiation and then the modified powders were hot pressed. The tribological properties of modified UHMWPE sliding against CoCrMo metallic plate on reciprocating tribometer under calf serum, saline and distilled water lubrication during a long-term friction were investigated. The measurement of Fourier-transform infrared spectroscopy indicates that AA is successfully grafted on the surface of UHMWPE powders by photo-induced graft polymerization. Contact angles of UHMWPE are decreased from 83° to 35° by grafting and the surface wettability is effectively improved. The tensile strength of modified sample decreases. The friction coefficient and wear rate of UHMWPE-g-PAA under calf serum, saline and distilled water lubrication are lower than that of untreated UHMWPE. With the increase of grafting ratio, the wear rate of UHMWPE-g-PAA decreases firstly and then increases. The modified UHMWPE with grafting ratio of 3.5 % has the lowest wear rate, which is just quarter of the untreated UHMWPE. The hydrated PAA polymer brushes enclosed in the UHMWPE bulk material provide continuous lubrication during long term sliding.
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Affiliation(s)
- Yaling Deng
- School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing, 210094 Jiangsu, People's Republic of China
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Pruitt LA, Ansari F, Kury M, Mehdizah A, Patten EW, Huddlestein J, Mickelson D, Chang J, Hubert K, Ries MD. Clinical trade-offs in cross-linked ultrahigh-molecular-weight polyethylene used in total joint arthroplasty. J Biomed Mater Res B Appl Biomater 2013; 101:476-84. [PMID: 23436567 DOI: 10.1002/jbm.b.32887] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Revised: 08/15/2012] [Accepted: 11/18/2012] [Indexed: 11/09/2022]
Abstract
Highly cross-linked formulations of ultrahigh-molecular-weight polyethylene (XLPE) offer exceptional wear resistance for total joint arthroplasty but are offset with a reduction in postyield and fatigue fracture properties in comparison to conventional ultrahigh-molecular-weight polyethylene (UHMWPE). Oxidation resistance is also an important property for the longevity of total joint replacements (TJRs) as formulations of UHMWPE or XLPE utilizing radiation methods are susceptible to free radical generation and subsequent embrittlement. The balance of oxidation, wear, and fracture properties is an enduring concern for orthopedic polymers used as the bearing surface in total joint arthroplasty. Optimization of material properties is further challenged in designs that make use of locking mechanisms, notches, or other stress concentrations that can render the polymer susceptible to fracture due to elevated local stresses. Clinical complications involving impingements, dislocations, or other biomechanical overloads can exacerbate stresses and negate benefits of improved wear resistance provided by XLPE. This work examines trade-offs that factor into the use of XLPE in TJR implants.
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Affiliation(s)
- Lisa A Pruitt
- Department of Mechanical Engineering, University of California, Berkeley, California, USA
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Xiong L, Xiong D. The influence of irradiation dose on mechanical properties and wear resistance of molded and extruded ultra high molecular weight polyethylene. J Mech Behav Biomed Mater 2012; 9:73-82. [DOI: 10.1016/j.jmbbm.2012.01.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Revised: 01/02/2012] [Accepted: 01/08/2012] [Indexed: 10/14/2022]
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Xiong L, Xiong D, Yang Y, Jin J. Friction, wear, and tensile properties of vacuum hot pressing crosslinked UHMWPE/nano-HAP composites. J Biomed Mater Res B Appl Biomater 2011; 98:127-38. [PMID: 21598380 DOI: 10.1002/jbm.b.31842] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2010] [Revised: 11/26/2010] [Accepted: 02/10/2011] [Indexed: 11/08/2022]
Abstract
Ultra high molecular weight polyethylene (UHMWPE) is a thermoplastic engineering plastic with excellent mechanical properties. In this study, nonirradiated and irradiated UHMWPE/nano-hydroxyapatite (nano-HAP) composites were prepared by vacuum hot-pressing method, and then friction, wear, and tensile properties were investigated. To explore mechanisms of these properties, differential scanning calorimetry, infrared spectrum, and scanning electron microscopy with energy dispersive spectrometry analysis were carried out on the samples. The results in this study indicated that reduced friction coefficients and wear rate could be obtained when nonirradiated and irradiated UHMWPE were filled with 7% nano-HAP. The irradiated UHMWPE/7% nano-HAP also had a synergistic function of wear reduction as compared with irradiated UHMWPE and nonirradiated UHMWPE/7% nano-HAP. Samples filled with 7% nano-HAP showed a brittle fracture behavior, and a linear relationship between modulus and crystallinity for a nonirradiated and irradiated sample was found in this study.
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Affiliation(s)
- Lei Xiong
- Department of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing, Jiangsu 210094, China
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Czaja K, SudoŁ M. Studies on electron-beam irradiation and plastic deformation of medical-grade ultra-high molecular weight polyethylene. Radiat Phys Chem Oxf Engl 1993 2011. [DOI: 10.1016/j.radphyschem.2010.11.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Ong KL, Rundell S, Liepins I, Laurent R, Markel D, Kurtz SM. Biomechanical modeling of acetabular component polyethylene stresses, fracture risk, and wear rate following press-fit implantation. J Orthop Res 2009; 27:1467-72. [PMID: 19489047 DOI: 10.1002/jor.20918] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Press-fit implantation may result in acetabular component deformation between the ischial-ilial columns ("pinching"). The biomechanical and clinical consequences of liner pinching due to press-fit implantation have not been well studied. We compared the effects of pinching on the polyethylene fracture risk, potential wear rate, and stresses for two different thickness liners using computational methods. Line-to-line ("no pinch") reaming and 2 mm underreaming press fit ("pinch") conditions were examined for Trident cups with X3 polyethylene liner wall thicknesses of 5.9 mm (36E) and 3.8 mm (40E). Press-fit cup deformations were measured from a foam block configuration. A hybrid material model, calibrated to experimentally determined stress-strain behavior of sequentially annealed polyethylene, was applied to the computational model. Molecular chain stretch did not exceed the fracture threshold in any cases. Nominal shell pinch of 0.28 mm was estimated to increase the volumetric wear rate by 70% for both cups and peak contact stresses by 140 and 170% for the 5.9 and 3.8 mm-thick liners, respectively. Although pinching increases liner stresses, polyethylene fracture is highly unlikely, and the volumetric wear rates are likely to be low compared to conventional polyethylene.
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Affiliation(s)
- Kevin L Ong
- Exponent Inc., 3401 Market St., Suite 300, Philadelphia, Pennsylvania 19104, USA.
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