Polyethylene cross‐linking by two different methods reduces acetabular liner wear in a hip joint wear simulator

Abstract

Advances in cross-linking have led to the development of wear resistant hltrahigh rnaleeulat. weight pdlyethylenc f@r tdtd joint replacement. This study compared wear reduction by two different croes-lidking methads as measured in a hip bear simulhtdr, On@ highly cross-linked polyethylene was treated with 7.5 Mrad gamma irradiation with post-irradiation annealing add a 'sterilization dose of 2.5 Mrad (10 Gamma), while the other used 9.5 Mrad warm irradiation with 10 MeV electron-beam (9.5 EB). Liners of the same design, made from nominally cross-lhked (gamma sterilized) polyethylene were also tested. Gravimetric wear analysis was performed every 500,000 cycles for 5,000,000 cycles. After correcting for weight gain due to water absorption, the nominally crosslinked liners demonstrated meail wear rates of 15.7 (f1.7) and 12.5 (11.0) mglmillion cycies. Both highly cross-linked polyethylene liners demoiistrated significantly less wear than their respective controls (hith Mean hiear rates of 1.5 (11.2) and -1.4 (11.5) mgl million cycles). The 9.5 EB liners gained weight presumably due to intfea'sed fluid absurptidii, itl addition to tnat measured ih loaded-soaked control implahts. Any wear occurring was therefore assumed td have been more thhn offset by weight gain. Highly cross-linked polyethylene was significantly more wear resistant than non-or ndminally Cro's's-linked polyethylene. The differeilces in wear rates between the two highly crass-linked polyethylene designs (9.5 EB or 10 Ghmma) art2 probably too srriall to be clinically significant. lntroduction Improvements in implant design and surgical techrlique have reduced the incidence of early failllre of the acetabular and femoral components and ifidreased survivorship of total hip arthroplasty [2,29,31,41]. As a result, osteolysis resulting from ultrahigh molecular weight polyethylene (UHMWPE) wear debris has become one of the most significant factdrs affecting long term survivorship [ 1,13,16,19,49]. Alternative bearing surfaces have been proposed such as ceramic-on-ceramic and metal-on-metal articulations. However, these have their own poteritial disadvantages [3,9,18]. The long history and pbpulafitp of UfIMWPE as a bearihg surface has led to research in the development of tougher and fiore wear resistant polpetliylerie rrlatCrialS. These [12]. Another, more resent modification was HylamZr'", L.1 pdlyethylehe irl Which AH 2%-tefided chaili srystallile inorphology *ds ci-&ttPd with thicker lamellae and higher crystallinity thari cdnt.eritiO= iial UHMWPE. The yield strength and ultimate strength were slightly higher, but the elastic modulus was significantly higher than that of cbhventional UHMWPE. High

The John Charnley Award: An Accurate and Sensitive Method to Separate, Display, and Characterize Wear Debris: Part 1: Polyethylene Particles

“…With the introduction of highly wear-resistant crosslinked ultrahigh-molecular-weight polyethylene (UHMWPE), the overall volume of wear debris in THA has decreased compared to conventional polyethylene (PE) from more than 15 mm 3 /million cycles to less than 1 mm 3 /million cycles, particularly in THAs [9,37]. The reduction in overall PE wear rates has resulted in an associated and substantial reduction in the rates of osteolysis, with several clinical studies reporting no incidence at 5 to nearly 10 years' followup [10,13,19,20,27,32,39].…”

The effect of oxidative aging on the wear performance of highly crosslinked polyethylene knee inserts under conditions of severe malalignment

“…1 Crosslinking UHMWPE reduces wear rates when compared with conventional UHMWPE in the hip. [2][3][4][5][6][7] However, a major concern for the use of highly crosslinked UHMWPE in TKA is that the reduction in mechanical properties, decreased resistance to fatigue damage, and increased potential for oxidation might outweigh the benefits in wear when subjected to high contact stresses in the knee.…”

Comparison of CMM and Micro-CT Volumetric Analysis of Polyethylene Tibial Knee Inserts in Total Knee Replacement

“…It can be seen from Figure 5 that both CMM and Micro-CT measurement appear to be an overestimate compared to gravimetric measurement. Gravimetric measurement methodology is the standard method used in the determination of volume loss [3,4]. However, fluid absorption and metallic debris inclusion may affect the measurement.…”

“…Thus, wear measurement is very important for accurate determination of wear rate and volume loss in total knee replacements. The most standard method is gravimetric analysis [3,4]. However, the fundamental issue with gravimetric measurement is that it needs a reference from which to calculate the wear.…”