Highly Cross-linked, Electron-Beam-Irradiated, Melted Polyethylene

Abstract

Extensive new evidence generated within the past the year provides strong support for the use of electron-beam highly cross-linked, subsequently melted ultra-high molecular weight polyethylene in total hip replacement arthroplasty. In terms of wear reduction, three studies involving three different demographic groups and two different measurement techniques have found that the femoral head penetration with this type of polyethylene after bedding in has finished taking place is less than 10 micra per year. This wear rate is similar to the wear rate of metal-on-metal and ceramic-onceramic articulations. Retrieval specimens up to 3 years after insertion confirmed the minimal wear by exhibiting persisting machine marks throughout the inside diameter of the liner. Extensive studies show no evidence of oxidation, confirming the absence of residual free radicals. No evidence of fatigue failure exists except three known cases out of 150,000, in which malposition of the acetabular component produced abnormally high contact stresses on unsupported polyethylene. The in vivo wear, oxidation resistance, and mechanical properties of this alternative bearing material are excellent, with in vivo durations now exceeding five years. The other major advantages over hard-on-hard bearings including familiarity, adaptability, forgiveness, and cost seem to be compelling.The list of advantages of electron-beam highly crosslinked, subsequently melted ultra-high molecular weight polyethylene (PE) as the preferred alternate bearing surface in total hip arthroplasty (THA) is extensive. It includes extremely low wear rate, absence of oxidation, the ability to use femoral large heads, familiarity, adaptability, forgiveness, the absence of the specific disadvantages of metal-on-metal couplings, the absence of the specific disadvantage of ceramic-on-ceramic couplings, and cost relative to hard-on-hard bearings.New in vivo data on wear reduction using this highly cross-linked PE in THA are strong. Two contemporary radiostereometric analysis (RSA) in vivo studies 12 of electron-beam-irradiated, subsequently melted, highly crosslinked ultra-high molecular weight PE attest to the high wear resistance that this cross-linking produces. In one of the two RSA studies, 12 54 patients were examined for a 2-year period with RSA, contrasting contemporary (gamma sterilization in nitrogen) versus electron-beam-irradiated, subsequently melted, highly cross-linked PE (10 Mrad e-beam irradiation) in patients having bilateral simultaneous THA using a modular, cementless socket. At 2 years, the highly cross-linked material showed a 90% reduction in proximal penetration of the femoral head compared with the control group (p ‫ס‬ 0.007). This is a considerable difference in penetration. After the first year, that is to say, after the bedding-in and creep had subsided, there was no detectable further penetration of the femoral head into the PE, which is noteworthy. The reduction in the 3-D penetration was also statistically significant (p ‫ס‬ 0.006).In the second RSA...

Meniscal wear at a three-component total ankle prosthesis by a knee joint simulator

“…Though preliminary, the results here reported provide for the first time possible wear patterns on TAR. The linear penetration observed here in the three specimens compares very well with ceramic-to-polyethylene or metal-to-polyethylene couplings (Affatato et al, 2001a, b;Affatato, et al, 2000;Salernitano and Migliaresi, 2003;Saikko et al, 2001;Liao et al, 2003;McKellop et al, 1996;Saikko et al, 1993;Skinner, 1999;Jazrawi et al, 1999;Firkins et al, 2001;Silva et al, 2005;Wright, 2005;Greenwald and Heim, 2005;Harris, 2004). This is well within the range obtained in RSA (Price et al, 2005) studies for the Oxford Unicompartmental Meniscal Knee, which features, as the presently analyzed TAR design, a fully congruous unconstrained meniscal bearing and articular surfaces compatible with ligament natural function.…”

Femoral Head Size of 36 mm against Highly Cross-linked Polyethylene in Patients Younger than 60 Years: Minimun Three Years of Follow Up

“…2,3,[20][21][22][23][24] However, the widespread adoption of larger diameter femoral heads against conventional polyethylene is limited by the risk of accelerated wear and resulting osteolysis. reported to be independent of head size.…”

“…Large diameter femoral heads provide a means of reducing the risk of dislocation, but increases in wear debris have prevented the widespread use of this option in primary articulation. [1][2][3][4][5] In general, younger patients have higher activity levels, and thus, show higher levels of polyethylene wear. 6) Furthermore, implants placed in younger patients must also have greater longevity.…”

Comparison of Bipolar Hemiarthroplasty and Total Hip Arthroplasty using Large Heads in Patients with Femoral Neck Fractures

“…5,6) Larger diameter femoral heads (≥36 mm) have a larger range of motion and believed to be a valuable tool for preventing a dislocation in THA. [7][8][9] Based on this data, it was hypothesized THA with a 36 mm-femoral head will produce superior results without any serious complications compared with BH. We already reported on clinical data on the performance of THA using a large head in patients with a intracapsular femoral neck fracture.…”