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Nishimura M, Nakamura T, Nishida H, Misaki T, Aikawa T. In Vivo Oxidation and Wear in Remelted Highly Cross-Linked Polyethylene Liners Retrieved at a Minimum of 10 Years After Total Hip Arthroplasty. J Arthroplasty 2024; 39:3092-3096. [PMID: 38909854 DOI: 10.1016/j.arth.2024.06.034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Revised: 06/13/2024] [Accepted: 06/14/2024] [Indexed: 06/25/2024] Open
Abstract
BACKGROUND With the decreasing age threshold for patients undergoing total hip arthroplasty (THA), there is an escalating demand for enhanced polyethylene durability. Although reports assessing wear in remelted highly cross-linked polyethylene (HXLPE) through radiographic imaging exist, a consensus regarding its oxidation level is lacking. This study investigated the wear, oxidation levels, and degradation of remelted HXLPE that was retrieved at least 10 years after THA. METHODS Our analysis focused on 7 cases of melted HXLPE liners retrieved ≥10 years after THA. All patients were women, who had an average age of 64 ± 6.5 years at the initial operation, and the mean postoperative period after THA was 12 years and 11 months ±1 year and 5 months. The wear conditions were measured by matching the shape analysis data obtained from a coordinate-measuring machine with a spherical model. Fourier-transform infrared spectroscopy was used to study the oxidation of polyethylene, and the polyethylene structure was evaluated using scanning electron microscopy. RESULTS Osteolysis was not observed in any case on X-rays, computed tomography, or intraoperative findings during revision surgery. The average oxidation index (OI) of the sliding surface under load was 0.31 ± 0.22 in the 6 cases calculated after hexane treatment, and 0.69 for one case without hexane treatment. In the 6 cases calculated after hexane treatment, the average OI of the non-load-bearing sliding surface was 0.11 ± 0.20. Average wear values were 0.33 ± 0.11 mm at 45 degrees from the equatorial direction and 0.04 ± 0.07 mm in the opposite direction. The initial structure of the polyethylene was preserved at all sites with low oxidation levels; however, in one case with stem subsidence, morphological changes and a high OI were observed. CONCLUSIONS Long-term oxidation and wear of remelted HXLPE liners retrieved from THA patients were minimal.
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Affiliation(s)
- Manase Nishimura
- Department of Orthopaedic Surgery, Toyama Nishi General Hospital, Toyama, Japan
| | - Takuya Nakamura
- Department of Orthopaedic Surgery, Toyama Nishi General Hospital, Toyama, Japan
| | - Hideji Nishida
- Department of Orthopaedic Surgery, Toyama Nishi General Hospital, Toyama, Japan
| | - Tomonori Misaki
- Department of Orthopaedic Surgery, Fukui Prefectural Hospital, Fukui, Japan
| | - Takao Aikawa
- Department of Orthopaedic Surgery, Toyama Prefecture Central Hospital, Toyama, Japan
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Zitsch BP, Cahoy KM, Urban ND, Buckner BC, Garvin KL. Highly Cross-Linked Polyethylene in Patients 50 Years of Age and Younger: A 20-year Follow-Up Analysis. J Arthroplasty 2024; 39:S145-S152. [PMID: 38548239 DOI: 10.1016/j.arth.2024.03.051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Revised: 03/15/2024] [Accepted: 03/18/2024] [Indexed: 04/21/2024] Open
Abstract
BACKGROUND Highly cross-linked polyethylene (HXLPE) has been an excellent bearing for total hip arthroplasty (THA) due to improved wear characteristics compared to conventional materials. Patients 50 years of age or younger are at high risk for wear-related complications of their THA, and few studies have followed these patients who have HXPLE into the third decade. METHODS In a retrospective review of 88 consecutive THAs performed in 77 patients aged 50 years and younger (mean 41; range, 20 to 50), in which HXLPE was utilized, they were evaluated for their clinical and radiographic results at an average of 20-year follow-up (range, 18 to 24). The current study reports on longer-term follow-up from our previously published series at shorter follow-up times. Patients were categorized by femoral head material: cobalt chrome (n = 14), ceramic (n = 30), and oxidized zirconium (n = 22) and by femoral head size: 26 mm (n = 12), 28 mm (n = 46), and 32 mm (n = 8). Harris Hip Scores were collected preoperatively and at the most recent follow-up. Radiographs were evaluated for linear and volumetric wear, radiolucent lines, and osteolysis. RESULTS Mean Harris Hip Scores improved from 47.1 (standard deviation [SD] 8.8) preoperatively to 92.0 (SD 7.7) (P < .0001) at 20-year follow-up. There was one hip that was revised for recurrent instability, and no hip demonstrated radiographic evidence of loosening or osteolysis. The mean polyethylene linear wear rate was 0.017 (SD 0.012) mm/y, and the mean polyethylene volumetric wear rate was 3.15 (SD 2.8) mm3/year, with no significant differences based on articulation type or head size. CONCLUSIONS Total hip arthroplasty with HXLPE in patients ≤ 50 years of age continues to demonstrate excellent long-term clinical and radiographic outcomes with low wear characteristics at 20-year follow-up, regardless of femoral head material or size.
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Affiliation(s)
- Bradford P Zitsch
- Department of Orthopaedic Surgery, University of Nebraska Medical Center, Omaha, Nebraska
| | - Kevin M Cahoy
- College of Medicine, University of Nebraska Medical Center, Omaha, Nebraska
| | - Nathanael D Urban
- College of Medicine, University of Nebraska Medical Center, Omaha, Nebraska
| | - Brandt C Buckner
- Department of Orthopaedic Surgery, University of Nebraska Medical Center, Omaha, Nebraska
| | - Kevin L Garvin
- Department of Orthopaedic Surgery, University of Nebraska Medical Center, Omaha, Nebraska
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Parilla FW, Youngman TR, Layon DR, Ince DC, Pashos GE, Maloney WJ, Clohisy JC. Excellent 20-Year Results of Total Hip Arthroplasty With Highly Cross-Linked Polyethylene on Cobalt-Chromium Femoral Heads in Patients ≤50 Years. J Arthroplasty 2024; 39:409-415. [PMID: 37572728 DOI: 10.1016/j.arth.2023.08.025] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/21/2023] [Revised: 08/04/2023] [Accepted: 08/05/2023] [Indexed: 08/14/2023] Open
Abstract
BACKGROUND Highly cross-linked polyethylene (HXLPE) acetabular bearing surfaces have appeared to offer excellent wear resistance, low incidence of wear-related osteolysis, and high implant survivorship at 10-year to 15-year follow-up. However, concerns over potential performance deterioration at longer-term follow-up remain - particularly in younger patients - and outcome data into the third decade have not been available. METHODS We retrospectively assessed 62 patients (68 hips) who underwent primary total hip arthroplasty (THA) at age ≤50 years with a single manufacturer's cementless components, remelted HXLPE liner, and small diameter (26 and 28 millimeter) cobalt-chromium (CoCr) femoral heads at minimum 18-year follow-up. We assessed clinical outcomes (modified Harris Hip score, University of California Los Angeles Activity Score, polyethylene wear rates, radiographic findings (osteolysis, component loosening), and implant survivorship. RESULTS At 20.6-year mean follow-up (range, 18 to 23 years) modified Harris Hip scores for surviving hips remained an average of 41 points above preoperative baseline (49 versus 90, P < .001) and UCLA scores 2.8 points above baseline (3.7 versus 6.4, P < .001). Wear analysis revealed a population linear wear rate of 0.0142 mm/y (standard deviation (SD), 0.0471) and volumetric wear rate of 10.14 mm3/y (SD, 23.41). Acetabular lysis was noted in 2 asymptomatic hips at 16.6 and 18.4 years. No components were radiographically loose. Survivorship free from wear-related revision was 100% at 20 years (97% free from any revision). CONCLUSION The HXLPE-CoCr bearing couple with small femoral heads continues to be extremely effective 20 years after primary THA in the younger patient population.
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Affiliation(s)
- Frank W Parilla
- Department of Orthopaedic Surgery, Washington University School of Medicine, St. Louis, Missouri
| | - Tyler R Youngman
- Department of Orthopaedic Surgery, Washington University School of Medicine, St. Louis, Missouri
| | - Daniel R Layon
- Department of Orthopaedic Surgery, Washington University School of Medicine, St. Louis, Missouri
| | - Deniz C Ince
- Department of Orthopaedic Surgery, Washington University School of Medicine, St. Louis, Missouri
| | - Gail E Pashos
- Department of Orthopaedic Surgery, Washington University School of Medicine, St. Louis, Missouri
| | - William J Maloney
- Department of Orthopaedic Surgery, Stanford University School of Medicine, Redwood City, California
| | - John C Clohisy
- Department of Orthopaedic Surgery, Washington University School of Medicine, St. Louis, Missouri
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4
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Naito Y, Hasegawa M, Tone S, Wakabayashi H, Sudo A. Minimum 7-year results of cementless total hip arthroplasty with vitamin E-diffused and 2-methacryloyloxyethyl phosphorylcholine-grafted highly cross-linked polyethylene. Medicine (Baltimore) 2023; 102:e36257. [PMID: 38050300 PMCID: PMC10695485 DOI: 10.1097/md.0000000000036257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Accepted: 11/01/2023] [Indexed: 12/06/2023] Open
Abstract
The purpose of this study was to evaluate the mid-term clinical results and polyethylene wear of vitamin E-diffused highly cross-linked polyethylene (HXLPE) and 2-methacryloyloxyethyl phosphorylcholine (MPC)-grafted HXLPE in cementless total hip arthroplasty (THA). Thirty-four THAs with vitamin E-diffused HXLPE (VEPE) and 32-mm cobalt-chromium head, and 116 THAs with MPC-grafted HXLPE and 32-mm alumina head were evaluated. The Merle d'Aubigné and Postel scores were administered. Kaplan-Meier survivorship was analyzed. Annual radiographs were analyzed using computerized method and linear steady-state wear rate was measured. The mean duration of follow-up was 9 years (range, 7-11 years) in VEPE group and 8 years (range, 7-10 years) in MPC group. The mean Merle d'Aubigné and Postel scores improved postoperatively in both groups. Kaplan-Meier survivorship with endpoint of revision was 100% (95% confidence interval, 100%-100%) in VEPE group and 98.3% (95% confidence interval, 93.4%-99.6%) in MPC group at 10 years (P = .44). The mean steady-state wear rate was 0.007 mm/year in VEPE group and 0.006 mm/year in MPC group (P = .60). The clinical results of both groups were good and wear rates of both liners were very low.
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Affiliation(s)
- Yohei Naito
- Department of Orthopaedic Surgery, Mie University Graduate School of Medicine, Tsu, Mie, Japan
| | - Masahiro Hasegawa
- Department of Orthopaedic Surgery, Mie University Graduate School of Medicine, Tsu, Mie, Japan
| | - Shine Tone
- Department of Orthopaedic Surgery, Mie University Graduate School of Medicine, Tsu, Mie, Japan
| | - Hiroki Wakabayashi
- Department of Orthopaedic Surgery, Mie University Graduate School of Medicine, Tsu, Mie, Japan
| | - Akihiro Sudo
- Department of Orthopaedic Surgery, Mie University Graduate School of Medicine, Tsu, Mie, Japan
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Kump J, Teeter MG, Matheson J, Klassen R, Lanting BA, Decker MM. The impact of free-radical stabilization techniques on in vivo subsurface mechanical properties in highly cross-linked polyethylene acetabular liners. J Orthop Res 2023. [PMID: 36601654 DOI: 10.1002/jor.25502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2022] [Revised: 11/14/2022] [Accepted: 12/07/2022] [Indexed: 01/06/2023]
Abstract
Highly cross-linked polyethylene (HXLPE) for total hip arthroplasty was developed to improve wear resistance in vivo and associated complications in comparison to ultrahigh molecular weight polyethylene. This material typically goes through various free-radical stabilization techniques by remelting, single-annealing, or sequentially annealing the polyethylene to improve in vivo oxidation and wear properties. The purpose of this study is to determine if there is evidence of subsurface microhardness changes in retrieved HXLPE liner at the rim and articular subsurface after extended in vivo time that could be associated with oxidation and its effects on mechanical properties and implant integrity. Retrieved HXLPE liners were chosen based on peak subsurface Fourier transform infrared spectroscopy oxidation values. Each was mechanically tested for subsurface microhardness at both the rim and articular surface using a validated microindentation technique. Rim testing demonstrated a decrease in mechanical integrity that corresponded to higher subsurface oxidation values regardless of the free-radical stabilization technique. At the articular surface, a decrease in mechanical integrity was observed near the surface corresponding to peak oxidation and Vicker's hardness, which decreased with increasing depths. This was found in all groups, with the exception of the single-annealed liners, which demonstrated decreased mechanical integrity trends at greater depths between 1.0 and 2.0 mm. Our results suggest that subsurface mechanical properties do change in vivo for certain implants. Though it is likely that the mechanical failures are multifactorial, we have shown that mechanical property degradation of HXLPE liners does occur with long-term in vivo exposure and should be considered a possible risk factor.
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Affiliation(s)
- Jordan Kump
- Department of Orthopaedic Surgery, The University of New Mexico Health Sciences Center, University of New Mexico, Albuquerque, New Mexico, USA
| | - Matthew G Teeter
- Department of Medical Biophysics, Schulich School of Medicine and Dentistry, London, Canada.,Western University, Imaging Research Laboratories, Robarts Research Institute, Schulich School of Medicine and Dentistry, London, Ontario, Canada.,Surgical Innovation Program, Lawson Health Research Institute, London, Canada.,Division of Orthopaedic Surgery, London Health Sciences Centre, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada
| | - John Matheson
- Division of Orthopaedic Surgery, London Health Sciences Centre, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada
| | - Robert Klassen
- Department of Mechanical and Materials Engineering, Western University, London, Ontario, Canada
| | - Brent A Lanting
- Division of Orthopaedic Surgery, London Health Sciences Centre, University Hospital, London, Ontario, Canada
| | - Michael M Decker
- Department of Orthopaedic Surgery, The University of New Mexico Health Sciences Center, University of New Mexico, Albuquerque, New Mexico, USA
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Rowell SL, Reyes CR, Hopper RH, Engh CA, Muratoglu OK. Do total hip arthroplasty polyethylene liners without free radicals oxidize in vivo or ex vivo? J Biomed Mater Res B Appl Biomater 2021; 110:1113-1119. [PMID: 34894062 DOI: 10.1002/jbm.b.34985] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Revised: 08/15/2021] [Accepted: 11/13/2021] [Indexed: 11/08/2022]
Abstract
Crosslinking substantially reduces the wear of ultra-high molecular weight polyethylene (UHMWPE) used in total hip arthroplasty (THA) but some reports have indicated that first generation liners manufactured without antioxidants may be vulnerable to in vivo oxidation. This study evaluated maximum oxidation using Fourier transform infrared spectroscopy per ASTM F2102-06ε1 and linear head penetration using a coordinate measuring machine among 66 revision-retrieved THA components with in vivo durations ranging from 0.02 to 24.6 years. These included 30 liners crosslinked with 5 Mrad of gamma radiation and then melted, 13 non-crosslinked, never-irradiated liners sterilized with gas plasma and 23 non-crosslinked, never-irradiated liners sterilized with ethylene oxide. All liners were vacuum-sealed and stored at -20°C prior to analysis with the exception of three retrievals of each material type that were stored in air for 9.9 to 21.5 years. All 57 vacuum-sealed and frozen retrievals demonstrated good oxidative stability with maximum oxidation indices (OIs) less than 1.0 and 75% (43/57) of these liners had maximum OIs less than 0.1. Linear penetration measurements were lower in the crosslinked liners compared to non-crosslinked retrievals. Although instances of oxidation and embrittlement were found after ex vivo storage in air among liners that did not have free radicals at the time of implantation, in vivo oxidation does not appear to be a clinical concern through the first decade of service for crosslinked liners and at up to 25 years after surgery for non-crosslinked liners.
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Affiliation(s)
- Shannon L Rowell
- Harris Orthopaedics Laboratory at Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Christopher R Reyes
- Harris Orthopaedics Laboratory at Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Robert H Hopper
- Anderson Orthopaedic Research Institute, Alexandria, Virginia, USA
| | - Charles A Engh
- Anderson Orthopaedic Research Institute, Alexandria, Virginia, USA.,Inova Mount Vernon Hospital Joint Replacement Center, Alexandria, Virginia, USA
| | - Orhun K Muratoglu
- Harris Orthopaedics Laboratory at Massachusetts General Hospital, Boston, Massachusetts, USA
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7
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Decker M, Price A, Khalili A, Klassen R, Walzak MJ, Teeter M, McCalden R, Lanting B. The Impact of Free Radical Stabilization Techniques on in vivo Mechanical Changes in Highly Cross-Linked Polyethylene Acetabular Liners. Orthop Res Rev 2021; 13:113-122. [PMID: 34429667 PMCID: PMC8380133 DOI: 10.2147/orr.s309210] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Accepted: 07/22/2021] [Indexed: 01/13/2023] Open
Abstract
Introduction Numerous thermal free radical stabilization techniques are used in the production of highly cross-linked polyethylene (HXLPE) to improve oxidative stability. Little knowledge exists on the effects of in vivo time on the mechanical properties of HXLPE. The purpose of this study was to determine if free radical stabilization of HXLPE impacts mechanical properties as well as oxidative stability of acetabular liner rims after extended in vivo time. Methods Retrieved and control remelted, single annealed and sequentially annealed HXLPE liner rims were tested for mechanical properties. Oxidation was measured with FTIR spectroscopy and crystalline phase composition measured with Raman spectroscopy. Results No correlation was found between in vivo, ex vivo time and hardness for annealed groups. A statistically significant difference in hardness was identified between free radical stabilization groups. No correlation between maximum rim oxidation and in vivo time was found. Detectable levels of rim oxidation were present in 100% of single annealed, 75% of sequentially annealed, and 25% of remelted retrieved liners. Single and sequentially annealed liners demonstrated oxidation and increased crystallinity. Rim mechanical properties change in vivo for implant types. With in vivo time, retrieved remelted HXLPE demonstrated decreased mechanical properties, whereas retrieved single and sequentially annealed HXLPE properties remained stable. All liner cohorts demonstrated evidence of rim oxidation. Subsequent changes in crystallinity were only observed in oxidized annealed liners. Conclusion HXLPE acetabular liner rims show evidence of in vivo mechanical property degradation, notably in remelted HXLPE, which may be a risk factor in rim fracture and catastrophic implant failure.
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Affiliation(s)
- Michael Decker
- Department of Orthopaedic Surgery, The University of New Mexico Health Sciences Center, University of New Mexico, Albuquerque, NM, USA
| | - Amber Price
- Department of Orthopaedic Surgery, The University of New Mexico Health Sciences Center, University of New Mexico, Albuquerque, NM, USA
| | - Aria Khalili
- Department of Mechanical and Materials Engineering, Western University, London, Ontario, Canada
| | - Robert Klassen
- Department of Mechanical and Materials Engineering, Western University, London, Ontario, Canada
| | - Mary Jane Walzak
- Surface Science Western, University of Western Ontario, London, Ontario, Canada
| | - Matthew Teeter
- Department of Medical Biophysics, Schulich School of Medicine and Dentistry.,Imaging Research Laboratories, Robarts Research Institute, Schulich School of Medicine and Dentistry.,Surgical Innovation Program, Lawson Health Research Institute.,Division of Orthopaedic Surgery, Schulich School of Medicine and Dentistry, Western University and London Health Sciences Centre, London, Ontario, Canada
| | - Richard McCalden
- Division of Orthopaedic Surgery, London Health Sciences Centre, University Hospital, London, Ontario, Canada
| | - Brent Lanting
- Division of Orthopaedic Surgery, London Health Sciences Centre, University Hospital, London, Ontario, Canada
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Vitamin E-blended versus conventional polyethylene liners in prostheses : Prospective, randomized trial with 3-year follow-up. DER ORTHOPADE 2021; 49:1077-1085. [PMID: 31696260 DOI: 10.1007/s00132-019-03830-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
BACKGROUND Despite continuous technical improvements, polyethylene wear debris induced periprosthetic osteolysis remains the main cause for failure of hip arthroplasty. Progressive oxidation of polyethylene was identified as another risk factor for material failure. To overcome this problem, antioxidants such as vitamin E (alpha-tocopherol) were supplemented by diffusion into the latest generation of polyethylene liners. OBJECTIVE The purpose of the present study was to investigate the clinical outcome of patients treated with vitamin E blended highly cross-linked ultra-high molecular weight polyethylene liners (UHMWPE-XE) in comparison with conventional UHMWPE‑X liners by evaluating patient-reported outcome measures (PROM's) at 3‑year follow-up. METHODS A total of 143 patients were recruited into this prospective, randomized trial in our academic center. Three years after implantation, 101 patients were examined in the outpatient clinic for follow-up. Of these, 51 (50.5%) received UHMWPE-XE and 50 (49.5%) UHMWPE‑X liners. Clinical outcome was evaluated using Harris-Hip-Score (HHS) UCLA-Score and Hip Disability and Osteoarthritis Outcome Score (HOOS). RESULTS There was a significant improvement in all PROM's at one- and three-year follow-up compared to the status before implantation. PROM's did not differ significantly between the first and third year follow-up. Both liner groups showed an equal clinical outcome. CONCLUSION The present study demonstrates that the supplementation of vitamin E to polyethylene liners is reliable and safe without showing higher complication rates compared with conventional polyethylene liners. The shortterm clinical outcome of vitamin E-blended (UHMWPE‑XE) is equivalent to those of conventional highly cross-linked polyethylene liners.
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9
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Vitamin E-blended highly cross-linked polyethylene liners in total hip arthroplasty: a randomized, multicenter trial using virtual CAD-based wear analysis at 5-year follow-up. Arch Orthop Trauma Surg 2020; 140:1859-1866. [PMID: 32048017 DOI: 10.1007/s00402-020-03358-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Indexed: 10/25/2022]
Abstract
BACKGROUND Progressive oxidation of highly cross-linked ultra-high molecular weight (UHMPWE-X) liners is considered to be a risk factor for material failure in THA. Antioxidants such as vitamin E (alpha-tocopherol) (UHMWPE-XE) were supplemented into the latest generation of polyethylene liners. To prevent inhomogenous vitamin E distribution within the polymer, blending was established as an alternative manufacturing process to diffusion. The purpose of the present study was to investigate the in vivo wear behavior of UHMWPE-XE in comparison with conventional UHMWPE-X liners using virtual CAD-based radiographs. METHODS Until now, 94 patients from a prospective, randomized, controlled, multicenter study were reviewed at 5-year follow-up. Of these, 51 (54%) received UHMWPE-XE and 43 (46%) UHMWPE-X liners. Anteroposterior pelvic radiographs were made immediately after surgery and at 1 and 5 years postoperatively. The radiographs were analyzed using the observer-independent analysis software RayMatch® (Raylytic GmbH, Leipzig, Germany). RESULTS The mean wear rate was measured to be 23.6 μm/year (SD 13.7; range 0.7-71.8 μm). There were no significant differences between the two cohorts (UHMWPE-X: 23.2 μm/year vs. UHMWPE-XE: 24.0 μm/year, p = 0.73). Cup anteversion significantly changed within the 1st year after implantation independent from the type of polyethylene liner [UHMWPE-X: 18.2-23.9° (p = 0.0001); UHMWPE-XE: 21.0-25.5° (p = 0.002)]. No further significant changes of cup anteversion in both groups were found between year 1 and 5 after implantation [UHMWPE-X (p = 0.46); UHMWPE-XE (p = 0.56)]. CONCLUSION The present study demonstrates that the addition of vitamin E does not adversely affect the midterm wear behavior of UHMWPE-X. The antioxidative benefit of vitamin E is expected to become evident in long-term follow-up. Cup anteversion increment by 5° within the 1st year is likely a result of the released hip flexion contracture resulting in an enhanced posterior pelvic tilt. Therefore, a reassessment of target values in acetabular cup placement might be considered.
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10
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CORR Insights®: High Oxidation Stability of Tea Polyphenol-stabilized Highly Crosslinked UHMWPE Under an in Vitro Aggressive Oxidative Condition. Clin Orthop Relat Res 2019; 477:1956-1957. [PMID: 31232732 PMCID: PMC7000031 DOI: 10.1097/corr.0000000000000859] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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11
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Singh G, Klassen R, Howard J, Naudie D, Teeter M, Lanting B. Manufacturing, oxidation, mechanical properties and clinical performance of highly cross-linked polyethylene in total hip arthroplasty. Hip Int 2018; 28:573-583. [PMID: 29998768 DOI: 10.1177/1120700018780677] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Ultra-high molecular weight polyethylene (UHMWPE) continues to be the gold standard bearing surface in total hip arthroplasty (THA) for nearly 5 decades. Highly cross-linked UHMWPE (HXLPE) was adapted for routine use in the early 2000s to reduce the revision rates related to wear, osteolysis, and aseptic loosening resulting from conventional UHMWPE wear. Since its inception, consistent evidence showing reduced wear rates and osteolysis supports the use of HXLPE in THA. High quality studies demonstrating the advantage in long term survivorship of HXLPE over conventional UHMWPE are emerging. Though retrieval studies have demonstrated evidence of in vivo oxidation and fatigue related damage at the rim of the first generation HXLPE liners, clinical significance of this remains to be seen. Second-generation sequentially annealed and vitamin E containing HXLPE liners demonstrate improved mechanical properties, resistance to oxidation, and equivalent wear rates in comparison to their first-generation counterparts, but long term success remains to be seen.
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Affiliation(s)
- Gurpreet Singh
- 1 Joint Replacement Institute, London Health Science Center (LHSC), University Hospital, Schulich School of Medicine, Western University, London, Ontario, Canada
| | - Robert Klassen
- 2 Department of Mechanical and Materials Engineering, Western University, London, Ontario, Canada
| | - James Howard
- 1 Joint Replacement Institute, London Health Science Center (LHSC), University Hospital, Schulich School of Medicine, Western University, London, Ontario, Canada
| | - Douglas Naudie
- 1 Joint Replacement Institute, London Health Science Center (LHSC), University Hospital, Schulich School of Medicine, Western University, London, Ontario, Canada
| | - Matthew Teeter
- 3 Joint Replacement Institute, LHSC, University Hospital, Department of Medical Biophysics, Western University, Surgical Innovation Program, Lawson Health Research Institute, London, Ontario, Canada
| | - Brent Lanting
- 1 Joint Replacement Institute, London Health Science Center (LHSC), University Hospital, Schulich School of Medicine, Western University, London, Ontario, Canada
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12
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Pezzotti G, Zhu W, Sugano N, Marin E, Yamamoto K, Nishiike N, Hori T, Rondinella A, McEntire BJ, Bock R, Sonny Bal B. Oxide ceramic femoral heads contribute to the oxidation of polyethylene liners in artificial hip joints. J Mech Behav Biomed Mater 2018; 82:168-182. [PMID: 29601988 DOI: 10.1016/j.jmbbm.2018.03.021] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Revised: 03/12/2018] [Accepted: 03/15/2018] [Indexed: 12/01/2022]
Abstract
Experimental evidence demonstrates that a loss of stoichiometry at the surface of oxide bioceramic femoral heads enhances the oxidation rate of polyethylene acetabular liners in artificial hip joints. Contradicting the common notion that ceramics are bioinert, three independent experiments confirmed substantial chemical interactions between the ceramic femoral heads and their polyethylene counterparts. The experiments reported herein included hydrothermal tests, frictional tests, and hip-simulator experiments. It was discovered that oxide and non-oxide femoral heads differently affected the oxidation processes at the surface of the polyethylene liners, all other testing parameters being equal. Analytical data from X-ray photoelectron (XPS), cathodoluminescence (CL), Fourier-transform infrared (FTIR), and Raman spectroscopies unequivocally and consistently showed that the oxidation rate of polyethylene liners was greater when coupled with oxide as opposed to non-oxide ceramic heads. XPS analyses of O-Al-O bond fractions at the surface of a zirconia-toughened alumina (ZTA) short-term (20 months in vivo) femoral heads retrieval showed a ~50% reduction in favor of oxygen vacancy O-Al-VO and hydroxylated Al-O-H bonds. Off-stoichiometry drifts were confirmed in vitro under both static and dynamic conditions. They triggered oxidation and tangibly affected an advanced highly cross-linked sequentially irradiated and annealed ultra-high molecular weight polyethylene (UHMWPE) liner (increase in oxidation index up to ΔOI~1.2 after 5 × 105 cycles under dynamic swing conditions). Second-generation UHMWPE liners infused with vitamin E were also affected by the free flow of oxygen from the oxide femoral heads, although to a lesser extent. The fundamental findings of this study, which were also confirmed on retrievals, call for revised standards in material design and testing. Adopting these new criteria will provide an improved understanding of the importance of off-stoichiometry at the head/liner interface and may lead to significant extensions in artificial joint lifetimes.
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Affiliation(s)
- Giuseppe Pezzotti
- Ceramic Physics Laboratory, Kyoto Institute of Technology, Sakyo-ku, Matsugasaki, 606-8585 Kyoto, Japan; Department of Orthopedic Surgery, Tokyo Medical University, 6-7-1 Nishi-Shinjuku, Shinjuku-ku, 160-0023 Tokyo, Japan; The Center for Advanced Medical Engineering and Informatics, Osaka University, Yamadaoka, Suita, 565-0871 Osaka, Japan; Department of Molecular Cell Physiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kamigyo-ku, 465 Kajii-cho, Kawaramachi dori, 602-0841 Kyoto, Japan; The Center for Advanced Insect Research Promotion (CAIRP), Kyoto Institute of Technology, Sakyo-ku, Matsugasaki, 606-8585 Kyoto, Japan.
| | - Wenliang Zhu
- Department of Medical Engineering for Treatment of Bone and Joint Disorders, Osaka University, 2-2 Yamadaoka, Suita, Osaka 565-0854, Japan
| | - Nobuhiko Sugano
- Department of Medical Engineering for Treatment of Bone and Joint Disorders, Osaka University, 2-2 Yamadaoka, Suita, Osaka 565-0854, Japan
| | - Elia Marin
- Ceramic Physics Laboratory, Kyoto Institute of Technology, Sakyo-ku, Matsugasaki, 606-8585 Kyoto, Japan
| | - Kengo Yamamoto
- Department of Orthopedic Surgery, Tokyo Medical University, 6-7-1 Nishi-Shinjuku, Shinjuku-ku, 160-0023 Tokyo, Japan
| | - Naomichi Nishiike
- Ceramic Physics Laboratory, Kyoto Institute of Technology, Sakyo-ku, Matsugasaki, 606-8585 Kyoto, Japan
| | - Tsubasa Hori
- Ceramic Physics Laboratory, Kyoto Institute of Technology, Sakyo-ku, Matsugasaki, 606-8585 Kyoto, Japan
| | - Alfredo Rondinella
- Ceramic Physics Laboratory, Kyoto Institute of Technology, Sakyo-ku, Matsugasaki, 606-8585 Kyoto, Japan
| | - Bryan J McEntire
- Amedica Corporation, 1885 West 2100 South, Salt Lake City, UT 84119, USA
| | - Ryan Bock
- Amedica Corporation, 1885 West 2100 South, Salt Lake City, UT 84119, USA
| | - B Sonny Bal
- Amedica Corporation, 1885 West 2100 South, Salt Lake City, UT 84119, USA; Department of Orthopaedic Surgery, University of Missouri, Columbia, MO 65212, USA
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Wright TM. Commentary on "increased oxidative protection by high active vitamin E content and partial radiation crosslinking of UHMWPE". J Orthop Res 2018; 36:2087-2088. [PMID: 29533485 DOI: 10.1002/jor.23885] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- Timothy M Wright
- F.M. Kirby Chair of Orthopaedic Biomechanics, Hospital for Special Surgery, 535 East 70th Street, New York 10021, New York
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Otto Aufranc Award: Crosslinking Reduces THA Wear, Osteolysis, and Revision Rates at 15-year Followup Compared With Noncrosslinked Polyethylene. Clin Orthop Relat Res 2018; 476. [PMID: 29529656 PMCID: PMC6259699 DOI: 10.1007/s11999.0000000000000036] [Citation(s) in RCA: 77] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
BACKGROUND Crosslinked polyethylene (XLPE) liners used for primary THA have demonstrated lower wear rates than noncrosslinked, conventional polyethylene (CPE) liners through the first decade of clinical service. However, little high-quality evidence is currently available regarding the second decade performance of these implants and it remains uncertain whether the onset of osteolysis has simply been delayed or if the wear associated with XLPE liners will remain low enough that osteolysis will not occur. It is also unknown how the potential reductions in wear and osteolysis will influence long-term revision rates. QUESTIONS/PURPOSES Do patients who underwent THA with XLPE liners demonstrate (1) a lower rate of revision for wear-related complications; (2) a reduced wear rate; and (3) a lower frequency of osteolysis compared with those with CPE liners? METHODS Over an 18-month period from 1999 to 2000, 226 patients who had 236 primary THAs consented to participate in a randomized controlled trial conducted at one institution. To be eligible for intraoperative randomization, patients had to be implanted with a 28-mm cobalt-chrome alloy femoral head, a 4-mm lateralized liner, and the same cup and stem design. Six patients with six THAs were excluded intraoperatively because they did not receive study components for reasons unrelated to the liner material. The remaining 230 THAs among 220 patients were randomized to XLPE liners or CPE liners. The mean age at surgery was 62 ± 11 years and there were no differences in age, gender, or body mass index among the groups. There was no differential loss to followup between the study groups; among patients not known to be deceased or having undergone revision, minimum 14-year radiographic followup is available for 85 THAs including 46 with XLPE and 39 with CPE liners. Polyethylene wear was measured radiographically using Martell's Hip Analysis Suite and areas of osteolysis were evaluated before revision or at most recent followup. Revision rates at 15 years using reoperation for any reason and revision for wear or osteolysis were calculated using cumulative incidence considering patient death as a competing risk. RESULTS The cumulative incidence of revision at 15 years using reoperation for wear-related complications as an endpoint was lower in the XLPE group than the CPE group (0%, 95% confidence interval [CI], 0%-0% versus 12%, 95% CI, 7%-19%; p < 0.001). Among unrevised THAs with minimum 14-year radiographic followup, the mean steady-state linear wear rate for THAs with XLPE liners was lower than the mean linear wear rate for the THAs with CPE liners (0.03 ± 0.05 versus 0.17 ± 0.09 mm/year; mean difference, 0.14; 95% CI, 0.11-0.17; p < 0.001). Osteolysis of any size was noted among 9% (four of 46) of the hips in the XLPE group and 46% (18 of 39) of the hips in the CPE group (odds ratio, 0.19; 95% CI, 0.07-0.51; p < 0.001). CONCLUSIONS This randomized study with followup into the second decade demonstrated reductions in revision, wear, and osteolysis associated with the use of XLPE. The low wear rates and absence of any mechanical failures among the XLPE liners at long-term followup affirm the durability of these components that did not incorporate antioxidants. Although osteolysis has not been eliminated, it occurs infrequently and has not caused any clinical problems to date. LEVEL OF EVIDENCE Level I, therapeutic study.
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Epinette JA, Harwin SF, Rowan FE, Tracol P, Mont MA, Chughtai M, Westrich GH. Early experience with dual mobility acetabular systems featuring highly cross-linked polyethylene liners for primary hip arthroplasty in patients under fifty five years of age: an international multi-centre preliminary study. INTERNATIONAL ORTHOPAEDICS 2016; 41:543-550. [PMID: 28013332 DOI: 10.1007/s00264-016-3367-0] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Accepted: 12/02/2016] [Indexed: 01/25/2023]
Abstract
PURPOSE To evaluate early performance of contemporary dual mobility acetabular systems with second generation annealed highly cross-linked polyethylene for primary hip arthroplasty of patients under 55 years of age. METHODS A prospective observational five years study across five centers in Europe and the USA of 321 patients with a mean age of 48.1 years was performed. Patients were assessed for causes of revision, hip instability, intra-prosthetic dissociation, Harris hip score and radiological signs of osteolysis. RESULTS There were no dislocations and no intra-prosthetic dissociations. Kaplan Meier analysis demonstrated 97.51% survivorship for all cause revision and 99.68% survivorship for acetabular component revision at five years. Mean Harris hip score was 93.6. Two acetabular shells were revised for neck-rim implant impingement without dislocation and ten femoral stems were revised for causes unrelated to dual mobility implants. CONCLUSION Contemporary highly cross-linked polyethylene dual mobility systems demonstrate excellent early clinical, radiological, and survivorship results in a cohort of patients that demand high performance from their implants. It is envisaged that DM and second generation annealed HXLPE may reduce THA instability and wear, the two most common causes of THA revision in hip arthroplasty.
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Affiliation(s)
- Jean-Alain Epinette
- Orthopaedic Research and Imaging Center in Arthroplasty, 62700, Bruay-La-Buissière, France.
| | - Steven F Harwin
- Adult Reconstruction and Total Joint Replacement, Mount Sinai Hospital, New York, NY, USA
| | - Fiachra E Rowan
- Adult Reconstruction and Joint Replacement, Hospital for Special Surgery, New York, NY, USA
| | - Philippe Tracol
- , Clinique Saint-Roch 235, route des Gordes, Cavaillon, France
| | - Michael A Mont
- Adult Reconstruction and Joint Replacement, Cleveland Clinic Foundation, Cleveland, OH, USA
| | - Morad Chughtai
- Adult Reconstruction and Joint Replacement, Cleveland Clinic Foundation, Cleveland, OH, USA
| | - Geoffrey H Westrich
- Adult Reconstruction and Joint Replacement, Hospital for Special Surgery, New York, NY, USA
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Malatray M, Roux JP, Gunst S, Pibarot V, Wegrzyn J. Highly crosslinked polyethylene: a safe alternative to conventional polyethylene for dual mobility cup mobile component. A biomechanical validation. INTERNATIONAL ORTHOPAEDICS 2016; 41:507-512. [PMID: 27837329 DOI: 10.1007/s00264-016-3334-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2016] [Accepted: 10/31/2016] [Indexed: 11/30/2022]
Abstract
PURPOSE Dual mobility cup (DMC) consists of a cobalt-chromium (CoCr) alloy cup articulated with a polyethylene (PE) mobile component capturing the femoral head in force using a snap-fit technique. This biomechanical study was the first to evaluate and compare the generation of cracks in the retentive area of DMC mobile components made of highly crosslinked PE (XLPE) or conventional ultra-high molecular weight PE (UHMWPE). METHODS Eighty mobile components designed for a 52-mm diameter Symbol® DMC (Dedienne Santé, Mauguio, France) and a 28-mm diameter femoral head were analyzed. Four groups of 20 mobile components were constituted according to the PE material: raw UHMWPE, sterilized UHMWPE, annealed XLPE and remelted XLPE. Ten mobile components in each group were impacted with a 28-mm diameter CoCr femoral head using a snap-fit technique. The occurrence, location and area of the cracks in the retentive area were investigated using micro-CT (Skyscan 1176®, Bruker, Aarsellar, Belgium) with a 35 μm nominal isotropic voxel size by two observers blinded to the PE material and impaction or not of the mobile components. RESULTS Compared to conventional UHMWPE, the femoral head snap-fit did not generate more or wider cracks in the retentive area of annealed or remelted XLPE mobile components. CONCLUSION This biomechanical study suggests that XLPE in DMC could be a safe alternative to conventional UHMWPE regarding the generation of cracks in the retentive area related to the femoral head snap-fit.
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Affiliation(s)
- Matthieu Malatray
- Department of Orthopedic Surgery - Pavillon T, Hôpital Edouard Herriot, Hospices Civils de Lyon, 5, place d'Arsonval, 69437, Lyon, France
- INSERM UMR 1033, Université de Lyon, Lyon, France
| | | | - Stanislas Gunst
- Department of Orthopedic Surgery - Pavillon T, Hôpital Edouard Herriot, Hospices Civils de Lyon, 5, place d'Arsonval, 69437, Lyon, France
| | - Vincent Pibarot
- Department of Orthopedic Surgery - Pavillon T, Hôpital Edouard Herriot, Hospices Civils de Lyon, 5, place d'Arsonval, 69437, Lyon, France
| | - Julien Wegrzyn
- Department of Orthopedic Surgery - Pavillon T, Hôpital Edouard Herriot, Hospices Civils de Lyon, 5, place d'Arsonval, 69437, Lyon, France.
- INSERM UMR 1033, Université de Lyon, Lyon, France.
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D'Antonio J, Capello WN, Ramakrishnan R. Once Annealed Highly Cross-Linked Polyethylene Exhibits Low Wear at 9 to 15 Years. Orthopedics 2016; 39:e565-71. [PMID: 27088350 DOI: 10.3928/01477447-20160414-03] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Accepted: 07/17/2015] [Indexed: 02/03/2023]
Abstract
A once annealed highly cross-linked polyethylene (HXLPE) was introduced in 1998. Concerns regarding its long-term performance and oxidative resistance exist because of the presence of retained free radicals. The authors studied 48 patients with 50 hip implants having an average age of 62 years. They were followed for 9 to 15 years. The purpose of this study was to determine linear wear rate and the incidence of osteolysis and/or mechanical failure. At an average follow-up of 12.2 years, the annual linear wear rate was 0.018 mm (SD, 0.024 mm). No mechanical failures or osteolysis have been found to date. The clinical performance of this HXLPE continues to meet expectations despite the presence of free radicals. [Orthopedics. 2016; 39(3):e565-e571.].
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Reinitz SD, Currier BH, Levine RA, Collier JP, Van Citters DW. Oxidation and other property changes of a remelted highly crosslinked
UHMWPE
in retrieved tibial bearings. J Biomed Mater Res B Appl Biomater 2015; 105:39-45. [DOI: 10.1002/jbm.b.33533] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2015] [Revised: 07/21/2015] [Accepted: 09/12/2015] [Indexed: 11/09/2022]
Affiliation(s)
- Steven D. Reinitz
- Thayer School of EngineeringDartmouth CollegeHanover New Hampshire03755
| | | | - Rayna A.C. Levine
- Thayer School of EngineeringDartmouth CollegeHanover New Hampshire03755
| | - John P. Collier
- Thayer School of EngineeringDartmouth CollegeHanover New Hampshire03755
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Shen J, Gao G, Liu X, Fu J. Natural polyphenols enhance stability of crosslinked UHMWPE for joint implants. Clin Orthop Relat Res 2015; 473:760-6. [PMID: 25106800 PMCID: PMC4317458 DOI: 10.1007/s11999-014-3850-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
BACKGROUND Radiation-crosslinked UHMWPE has been used for joint implants since the 1990s. Postirradiation remelting enhances oxidative stability, but with some loss in strength and toughness. Vitamin E-stabilized crosslinked UHMWPE has shown improved strength and stability as compared with irradiated and remelted UHMWPE. With more active phenolic hydroxyl groups, natural polyphenols are widely used in the food and pharmaceutical industries as potent stabilizers and could be useful for oxidative stability in crosslinked UHMWPE. QUESTIONS/PURPOSES We asked whether UHMWPE blended with polyphenols would (1) show higher oxidation resistance after radiation crosslinking; (2) preserve the mechanical properties of UHMWPE after accelerated aging; and (3) alter the wear resistance of radiation-crosslinked UHMWPE. METHODS The polyphenols, gallic acid and dodecyl gallate, were blended with medical-grade UHMWPE followed by consolidation and electron beam irradiation at 100 kGy. Radiation-crosslinked virgin and vitamin E-blended UHMWPEs were used as reference materials. The UHMWPEs were aged at 120 °C in air with oxidation levels analyzed by infrared spectroscopy. Tensile (n = 5 per group) and impact (n = 3 per group) properties before and after aging as per ASTM F2003 were evaluated. The wear rates were examined by pin-on-disc testing (n = 3 per group). The data were reported as mean ± SDs. Statistical analysis was performed by using Student's t-test for a two-tailed distribution with unequal variance for tensile and impact data obtained with n ≥ 3. A significant difference is defined with p < 0.05. RESULTS The oxidation induction time of 100 kGy UHMWPE was prolonged to 144 hours with 0.05 wt% dodecyl gallate and 192 hours with 0.05 wt% gallic acid compared with 48 hours for 0.05 wt% vitamin E-blended UHMWPE. Accelerated aging of these polyphenol-blended UHMWPEs resulted in ultimate tensile strength of 50.4 ± 1.4 MPa and impact strength of 53 ± 5 kJ/m(2) for 100 kGy-irradiated UHMWPE with 0.05 wt% dodecyl gallate, for example, in comparison to 51.2 ± 0.7 MPa (p = 0.75) and 58 ± 5 kJ/m(2) (p = 0.29) before aging. The pin-on-disc wear rates of 100 kGy-irradiated UHMWPE with 0.05 wt% dodecyl gallate and 0.05 wt% gallic acid were 2.29 ± 0.31 and 1.65 ± 0.32 mg/million cycles, comparable to 1.68 ± 0.25 and 2.05 ± 0.22 mg/million cycles for 100 kGy-irradiated virgin and 0.05 wt% vitamin E-blended UHMWPE. CONCLUSIONS Based on the sample numbers tested in this study, polyphenols appear to effectively enhance the oxidation stability without altering the mechanical properties or pin-on-disc wear rate of radiation-crosslinked UHMWPE. CLINICAL RELEVANCE Crosslinked UHMWPE with natural polyphenols with improved oxidative stability and low wear may find clinical application in joint implants.
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Affiliation(s)
- Jie Shen
- />Ningbo Key Laboratory of Polymer Materials, Polymers and Composites Division, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, 1219 Zhongguan West Road, Zhenhai District, Ningbo, 315201 People’s Republic of China
- />Faculty of Materials Science and Chemical Engineering, Ningbo University, Ningbo, Zhejiang Province, People’s Republic of China
| | - Guorong Gao
- />Ningbo Key Laboratory of Polymer Materials, Polymers and Composites Division, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, 1219 Zhongguan West Road, Zhenhai District, Ningbo, 315201 People’s Republic of China
| | - Xincai Liu
- />Faculty of Materials Science and Chemical Engineering, Ningbo University, Ningbo, Zhejiang Province, People’s Republic of China
| | - Jun Fu
- />Ningbo Key Laboratory of Polymer Materials, Polymers and Composites Division, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, 1219 Zhongguan West Road, Zhenhai District, Ningbo, 315201 People’s Republic of China
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Abstract
BACKGROUND Minimizing the impact of oxidation on ultrahigh-molecular-weight polyethylene components is important for preserving their mechanical integrity while in vivo. Among the strategies to reduce oxidation in modern first-generation highly crosslinked polyethylenes (HXLPEs), postirradiation remelting was considered to afford the greatest stability. However, recent studies have documented measurable oxidation in remelted HXLPE retrievals. Biologic prooxidants and physiologic loading have been proposed as potential mechanisms. QUESTIONS/PURPOSES In our pilot study, we asked: (1) Does cyclic stress induced by wear or (2) by cyclic compression loading increase oxidation and crystallinity of remelted HXLPE? (3) Does oxidative aging reduce the wear resistance of remelted HXLPE? METHODS Remelted and annealed HXLPE prisms (n = 1 per test condition) were tested in a wear simulator for 500,000 cycles. After wear testing, some samples were subjected to accelerated aging and then wear-tested again. Wear track volumes were characterized by confocal microscopy. Thin films (200-μm thick) were microtomed from wear prisms and then used for Fourier transform infrared spectroscopy oxidation and crystallinity assessments. Remelted HXLPE compression cylinders (n = 1 per test condition) were subjected to fatigue experiments and similar oxidation characterization. RESULTS Remelted HXLPE qualitatively showed low oxidation indices (≤ 1) when subjected either to cyclic loading or aging alone. However, oxidation levels almost doubled in near-surface regions when remelted HXLPE samples underwent consecutive cyclic loading, artificial aging, and cyclic loading steps. The type of loading (wear versus compression fatigue) appeared to not affect the oxidation behavior in the studied conditions. Annealed HXLPE showed higher oxidation (oxidation index > 3) than remelted HXLPE and delamination wear. No delamination wear was observed in remelted HXLPE in agreement with its comparatively low oxidation levels (oxidation index < 3). CONCLUSIONS With the numbers available in our pilot study, the findings suggest that cyclic stress arising from a wear process or from cyclic compression may trigger the loss of oxidative stability of remelted HXLPE and contribute to synergistically accelerate its progression. Further studies of the effect of cyclic stress on oxidation of remelted HXLPE are needed. CLINICAL RELEVANCE Retrieval studies are warranted to determine the natural history of the in vivo oxidation and wear behavior of first-generation, remelted HXLPE.
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Multidirectional wear and impact-to-wear tests of phospholipid-polymer-grafted and vitamin E-blended crosslinked polyethylene: a pilot study. Clin Orthop Relat Res 2015; 473:942-51. [PMID: 25342007 PMCID: PMC4317438 DOI: 10.1007/s11999-014-3995-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
BACKGROUND Modifying the surface and substrate of a crosslinked polyethylene (CLPE) liner may be beneficial for high wear resistance as well as high oxidative stability and excellent mechanical properties, which would be useful in contributing to the long-term performance of orthopaedic bearings. A grafted poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) layer on a vitamin E-blended crosslinked PE (HD-CLPE[VE]) surface may provide hydrophilicity and lubricity without compromising the oxidative stability or mechanical properties. QUESTIONS/PURPOSES (1) Will the modifications (PMPC grafting and vitamin E blending) affect the lubrication characteristics of the CLPE surface? (2) Will the modifications affect wear resistance? (3) Will the modifications affect fatigue resistance? METHODS We investigated the effects of surface and substrate modifications (PMPC grafting and vitamin E blending) on the wear and fatigue fracture of thin CLPE samples. For each of the untreated and PMPC-grafted CLPE surfaces with and without vitamin E blended (four groups), wettability and lubricity surface analyses were conducted as well as multidirectional wear and impact-to-wear tests using a pin-on-disk testing machine. RESULTS The water wettability and lubricity (CLPE [mean ± 95% confidence interval]: 23.2° ± 1.8°, 0.005 ± 0.001; HD-CLPE[VE]: 26.0° ± 2.3°, 0.009 ± 0.003) of the PMPC-grafted surfaces were greater (p < 0.001) than that (CLPE: 90.3° ± 1.2°, 0.067 ± 0.015; HD-CLPE[VE]: 90.8° ± 2.0°, 0.063 ± 0.008) of the untreated surface regardless of vitamin E additives. It was observed that the PMPC grafting (CLPE: 0.23 ± 0.06 mg; HD-CLPE[VE]: 0.05 ± 0.10 mg) was associated with reduced gravimetric wear (CLPE: 0.53 ± 0.08 mg, p = 0.004 HD-CLPE[VE]: 0.23 ± 0.07 mg, p = 0.038) in the multidirectional wear test. The PMPC-grafted surface characteristics did not appear to affect the impact fatigue resistance regardless of vitamin E blending. CONCLUSIONS PMPC grafting improved the surface hydrophilicity and lubricity, and it reduced the gravimetric wear in terms of multidirectional sliding. It did not result in differences in terms of the impact-to-unidirectional sliding regardless of vitamin E blending. Further research is needed to evaluate the wear resistance of PMPC-grafted HD-CLPE(VE) in long-term hip simulator tests under normal and severe conditions, which may offer useful clues to the possible performance of these materials in vivo. CLINICAL RELEVANCE Our preliminary in vitro findings suggest that some improvement in the wear performance of crosslinked polyethylene acetabular liners in total hip arthroplasty could be obtained using PMPC grafting. Further research is needed to evaluate the wear resistance of PMPC-grafted HD-CLPE(VE) in long-term hip simulator tests under normal and severe conditions, which may offer useful clues to the possible performance of these materials in vivo.
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Kurtz SM, MacDonald DW, Mont MA, Parvizi J, Malkani AL, Hozack W. Retrieval analysis of sequentially annealed highly crosslinked polyethylene used in total hip arthroplasty. Clin Orthop Relat Res 2015; 473:962-71. [PMID: 25537808 PMCID: PMC4317461 DOI: 10.1007/s11999-014-4113-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
BACKGROUND First-generation annealed and second-generation sequentially annealed, highly crosslinked polyethylenes (HXLPEs) have documented reduced clinical wear rates in their first decade of clinical use compared with conventional gamma inert-sterilized polyethylene. However, for both types of annealed HXLPE formulations, little is known about their reasons for revision, their in vivo oxidative stability, and their resistance to mechanical degradation. QUESTIONS/PURPOSES We asked whether retrieved sequentially annealed HLXPE acetabular liners exhibited: (1) similar reasons for revision; (2) lower oxidation; (3) improved resistance to wear and degradation of mechanical properties; and (4) improved resistance to macroscopic evidence of rim damage when compared with acetabular liners fabricated from single-dose annealed HXLPE. METHODS One hundred eighty-five revised acetabular liners in two cohorts (annealed and sequentially annealed) were collected in a multicenter retrieval program between 2000 and 2013. We controlled for implantation time between the two cohorts by excluding annealed liners with a greater implantation time than the longest term sequentially annealed retrieval (5 years); the mean implantation time (± SD) for the annealed components was 2.2 ± 1.4 years, and for the sequentially annealed liners, it was 1.2 ± 1.2 years. Reasons for revision were assessed based on medical records, radiographs, and examinations of the retrieved components. Oxidation was measured at the bearing surface, the backside surface, the locking mechanism, and the rim using Fourier transform infrared spectroscopy (ASTM F2102). Penetration was measured directly using a micrometer (accuracy: 0.001 mm). Mechanical behavior (ultimate load) was measured at the superior and inferior bearing surfaces using the small punch test (ASTM F2183). We used nonparametric statistical testing to analyze for differences in oxidation, penetration rates, and ultimate load when adjusting for HXLPE formulation as a function of implantation time. RESULTS The acetabular liners in both cohorts were revised most frequently for instability, loosening, and infection. Oxidation indices (OIs) of the sequentially annealed liners were lower than annealed liners at the bearing surface (mean OI difference = 0.3; p < 0.001), the backside surface (mean OI difference = 0.2; p < 0.001), and the rim (mean OI difference = 2.6; p < 0.001). No differences were detected in linear penetration rates between the cohorts (p = 0.10). Ultimate strength at the bearing surface of the HLXPE was not different between sequentially annealed and annealed cohorts (p = 0.72). CONCLUSIONS We observed evidence of in vivo oxidation in retrieved annealed and, to a lesser extent, retrieved sequentially annealed acetabular liners. However, we observed no association between the levels of oxidation and clinical performance of the liners. CLINICAL RELEVANCE The findings of this study document the oxidative and mechanical behavior of sequentially annealed HXLPE. The reduced oxidation levels in sequentially annealed liners support the hypothesis that annealing in sequential steps eliminates more free radicals. However, as a result of the short-term followup, analysis of longer-term retrievals is warranted.
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Affiliation(s)
- Steven M. Kurtz
- Implant Research Center, Drexel University, 3401 Market Street, Suite 345, Philadelphia, PA 19104 USA ,Exponent, Inc., 3440 Market Street, Suite 600, Philadelphia, PA 19104 USA
| | - Daniel W. MacDonald
- Implant Research Center, Drexel University, 3401 Market Street, Suite 345, Philadelphia, PA 19104 USA
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Effect of squalene absorption on oxidative stability of highly crosslinked UHMWPE stabilized with natural polyphenols. Polym Degrad Stab 2014. [DOI: 10.1016/j.polymdegradstab.2014.08.023] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Kyomoto M, Moro T, Yamane S, Watanabe K, Hashimoto M, Takatori Y, Tanaka S, Ishihara K. Poly(2-methacryloyloxyethyl phosphorylcholine) grafting and vitamin E blending for high wear resistance and oxidative stability of orthopedic bearings. Biomaterials 2014; 35:6677-86. [DOI: 10.1016/j.biomaterials.2014.04.051] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2014] [Accepted: 04/12/2014] [Indexed: 11/29/2022]
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Jäger M, van Wasen A, Warwas S, Landgraeber S, Haversath M, Group V. A multicenter approach evaluating the impact of vitamin e-blended polyethylene in cementless total hip replacement. Orthop Rev (Pavia) 2014; 6:5285. [PMID: 25002933 PMCID: PMC4083306 DOI: 10.4081/or.2014.5285] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2014] [Accepted: 02/07/2014] [Indexed: 11/23/2022] Open
Abstract
Since polyethylene is one of the most frequently used biomaterials as a liner in total hip arthroplasty, strong efforts have been made to improve design and material properties over the last 50 years. Antioxidants seems to be a promising alternative to further increase durability and reduce polyethylene wear in long term. As of yet, only in vitro results are available. While they are promising, there is yet no clinical evidence that the new material shows these advantages in vivo. To answer the question if vitamin-E enhanced ultra-high molecular weight polyethylene (UHMWPE) is able to improve long-term survivorship of cementless total hip arthroplasty we initiated a randomized long-term multicenter trial. Designed as a superiority study, the oxidation index assessed in retrieval analyses of explanted liners was chosen as primary parameter. Radiographic results (wear rate, osteolysis, radiolucency) and functional outcome (Harris Hip Scores, University of California-Los Angeles, Hip Disability and Osteoarthritis Outcome Score, Visual Analogue Scale) will serve as secondary parameters. Patients with the indication for a cementless total hip arthroplasty will be asked to participate in the study and will be randomized to either receive a standard hip replacement with a highly cross-linked UHMWPE-X liner or a highly cross-linked vitamin-E supplemented UHMWPE-XE liner. The follow-up will be 15 years, with evaluation after 5, 10 and 15 years. The controlled randomized study has been designed to determine if Vitamin-E supplemented highly cross-linked polyethylene liners are superior to standard XLPE liners in cementless total hip arthroplasty. While several studies have been started to evaluate the influence of vitamin-E, most of them evaluate wear rates and functional results. The approach used for this multicenter study, to analyze the oxidation status of retrieved implants, should make it possible to directly evaluate the ageing process and development of the implant material itself over a time period of 15 years.
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Affiliation(s)
- Marcus Jäger
- Orthopaedic Department, University of Duisburg-Essen, University Hospital Essen ; Tuttlingen, Germany
| | - Andrea van Wasen
- Orthopaedic Department, University of Duisburg-Essen, University Hospital Essen ; Tuttlingen, Germany
| | - Sebastian Warwas
- Orthopaedic Department, University of Duisburg-Essen, University Hospital Essen ; Tuttlingen, Germany
| | - Stefan Landgraeber
- Orthopaedic Department, University of Duisburg-Essen, University Hospital Essen ; Tuttlingen, Germany
| | - Marcel Haversath
- Orthopaedic Department, University of Duisburg-Essen, University Hospital Essen ; Tuttlingen, Germany
| | - Vitas Group
- B. Braun Melsungen AG, Aesculap Division , Tuttlingen, Germany
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Abstract
We reviewed the literature on the currently available choices of bearing surface in total hip replacement (THR). We present a detailed description of the properties of articulating surfaces review the understanding of the advantages and disadvantages of existing bearing couples. Recent technological developments in the field of polyethylene and ceramics have altered the risk of fracture and the rate of wear, although the use of metal-on-metal bearings has largely fallen out of favour, owing to concerns about reactions to metal debris. As expected, all bearing surface combinations have advantages and disadvantages. A patient-based approach is recommended, balancing the risks of different options against an individual’s functional demands. Cite this article: Bone Joint J 2014;96-B:147–56.
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Affiliation(s)
- A. Rajpura
- Wrightington Hospital, The Centre
for Hip Surgery, Appley Bridge, Wigan
WN6 9EP, UK
| | - D. Kendoff
- Helios ENDO Klinik, Holstenstr. 2, 22767
Hamburg, Germany
| | - T. N. Board
- Wrightington Hospital, The Centre
for Hip Surgery, Appley Bridge, Wigan
WN6 9EP, UK
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Highly crosslinked polyethylene does not reduce the wear in total knee arthroplasty: in vivo study of particles in synovial fluid. J Arthroplasty 2013; 28:1333-7. [PMID: 23507066 DOI: 10.1016/j.arth.2013.01.026] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2012] [Revised: 12/05/2012] [Accepted: 01/21/2013] [Indexed: 02/01/2023] Open
Abstract
The aim was to assess if the reduction in polyethylene wear with highly crosslinked polyethylene suggested by studies with knee simulators is confirmed in patients with a knee arthroplasty. The use of a conventional or a highly crosslinked polyethylene was randomly assigned intraoperatively. Twelve months after surgery a knee arthrocentesis was performed and the synovial fluid of 17 patients in each group was studied analysing the number, size and shape of the polyethylene particles by scanning electron microscope. We found no significant differences in the concentration, size or morphology of polyethylene particles between groups. The great variability in the number of particles between individuals suggests that in vivo polyethylene wear depends on many factors and probably the type of polyethylene is not the most significant.
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Oxidative properties and surface damage mechanisms of remelted highly crosslinked polyethylenes in total knee arthroplasty. INTERNATIONAL ORTHOPAEDICS 2013; 37:611-5. [PMID: 23397564 DOI: 10.1007/s00264-013-1796-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2012] [Accepted: 01/12/2013] [Indexed: 10/27/2022]
Abstract
PURPOSE Remelted highly crosslinked polyethylenes (HXLPEs) were introduced in total knee replacement (TKR) starting in 2001 to reduce wear and particle-induced lysis. The purpose of this study was to investigate the damage mechanisms and oxidative stability of remelted HXLPEs used in TKR. METHODS A total of 186 posteriorly stabilised tibial components were retrieved at consecutive revision operations. Sixty nine components were identified as remelted HXLPE. The conventional inserts were implanted for 3.4 ± 2.7 years, while the remelted components were implanted 1.4 ± 1.2 years. Oxidation was assessed using Fourier transform infrared spectroscopy. RESULTS Remelted HXLPE inserts exhibited lower oxidation indices compared to conventional inserts. We were able to detect slight regional differences within the HXLPE cohort, specifically at the bearing surface. CONCLUSION Remelted HXLPE was effective at reducing oxidation in comparison to gamma inert sterilised controls. Additional long-term HXLPE retrievals are necessary to ascertain the long term in vivo stability of these materials in TKR.
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MacDonald D, Hanzlik J, Sharkey P, Parvizi J, Kurtz SM. In vivo oxidation and surface damage in retrieved ethylene oxide-sterilized total knee arthroplasties. Clin Orthop Relat Res 2012; 470:1826-33. [PMID: 22125241 PMCID: PMC3369100 DOI: 10.1007/s11999-011-2184-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
BACKGROUND Gas sterilization (eg, ethylene oxide [EtO] and gas plasma) was introduced for polyethylene to reduce oxidation due to free radicals occurring during radiation sterilization. Recently, oxidation has been observed in polyethylenes with undetectable levels of free radicals, which were expected to be oxidatively stable. It is unclear whether in vivo oxidation will occur in unirradiated inserts sterilized with EtO. QUESTIONS/PURPOSES We analyzed the oxidation, mechanical behavior, and surface damage mechanisms of tibial inserts of a single design sterilized using EtO. METHODS We collected 20 EtO-sterilized tibial inserts at revision surgeries. We assessed oxidative using Fourier transform infrared spectroscopy and mechanical properties using the small punch test. Surface damage was assessed using damage scoring techniques and micro-CT. RESULTS Oxidation indexes were low and uniform between the regions. The subtle changes did not affect the mechanical properties of the polymer. The dominant surface damage modes included burnishing, abrasion, and third-body wear. There was no evidence of delamination in the retrievals. CONCLUSIONS The retrieved EtO-sterilized UHMWPE retrievals remained stable with respect to both oxidative and mechanical properties for up to 10 years in vivo. We did observe slight measurable amounts of oxidation in the inserts; however, it was far below levels that would be expected to compromise the strength of the polymer. CLINICAL RELEVANCE Due to the stable oxidative and mechanical properties, EtO-sterilized tibial components appear to be an effective alternative to gamma-sterilized inserts, at least in short-term implantations.
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Affiliation(s)
- Daniel MacDonald
- Implant Research Center, School of Biomedical Engineering, Science, and Health Systems, Drexel University, 3401 Market Street, Suite 300, Philadelphia, PA 19104 USA ,Exponent, Inc, Philadelphia, PA USA
| | - Josa Hanzlik
- Implant Research Center, School of Biomedical Engineering, Science, and Health Systems, Drexel University, 3401 Market Street, Suite 300, Philadelphia, PA 19104 USA ,Exponent, Inc, Philadelphia, PA USA
| | - Peter Sharkey
- Rothman Institute at Jefferson, Philadelphia, PA USA
| | - Javad Parvizi
- Rothman Institute at Jefferson, Philadelphia, PA USA
| | - Steven M. Kurtz
- Implant Research Center, School of Biomedical Engineering, Science, and Health Systems, Drexel University, 3401 Market Street, Suite 300, Philadelphia, PA 19104 USA ,Exponent, Inc, Philadelphia, PA USA
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Hinarejos P, Torres A, Piñol I, Valverde D, Prats E, Puig L. Polyethylene particles in synovial fluid after knee arthroplasty with a conventional or highly cross-linked polyethylene. Preliminary study. Rev Esp Cir Ortop Traumatol (Engl Ed) 2012. [DOI: 10.1016/j.recote.2011.07.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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Hinarejos P, Torres A, Piñol I, Valverde D, Prats E, Puig L. [Polyethylene particles in synovial fluid after knee arthroplasty with a conventional or highly cross-linked polyethylene. Preliminary study]. Rev Esp Cir Ortop Traumatol (Engl Ed) 2012; 56:210-5. [PMID: 23594808 DOI: 10.1016/j.recot.2011.12.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2011] [Revised: 12/14/2011] [Accepted: 12/20/2011] [Indexed: 10/14/2022] Open
Abstract
AIM OF THE STUDY In recent years cross-linked polyethylenes have been developed in an attempt to reduce the wear, as has been demonstrated in knee simulators. The aim is to assess, by counting particles of polyethylene in synovial fluid, whether the reduction in wear is confirmed in patients with a highly crosslinked polyethylene prosthesis. MATERIAL AND METHODS A prospective randomised study was designed. During the implantation of a knee prosthesis, one group of patients was assigned the use of a conventional polyethylene (group A), and the other group a highly crosslinked polyethylene (X3, Stryker Orthopaedics) (group B). At 12 months after surgery a knee arthrocentesis was performed, and the number of polyethylene particles was counted in a scanning electron microscopy. Fourteen samples from each group were studied. RESULTS Both groups were comparable in all study variables. We found no significant differences in the concentration of polyethylene particles/ml (1.49 ± 0.85 million in group A vs 1.42 ± 0.91 million in group B, P=.60) or the total number of isolated particles. We found no differences either in size or morphology of particles between both groups. DISCUSSION AND CONCLUSIONS Although several in vitro studies in vitro using different types of highly crosslinked polyethylene found a significant reduction, we did not find that that wear was reduced in the knees of these patients. The great variability in the number of particles between individuals suggests that polyethylene wear in vivo depends on many factors, so perhaps the type of polyethylene is not the most significant factor.
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Affiliation(s)
- P Hinarejos
- Servicio de Cirugía Ortopédica y Traumatología, Parc de Salut Mar (Hospitales del Mar y Esperanza), Barcelona, España.
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