Clinical safety and wear resistance of the phospholipid polymer-grafted highly cross-linked polyethylene liner

Abstract

To reduce the production of wear particles and subsequent aseptic loosening, we created a human articular cartilage-mimicked surface for a highly cross-linked polyethylene liner, whose surface grafted layer consisted of a biocompatible phospholipid polymer, poly(2-methacryloyloxyethyl phosphorylcholine). Although our previous in vitro findings showed that poly(2-methacryloyloxyethyl phosphorylcholine)-grafted particles were biologically inert and caused no subsequent bone resorptive responses, and poly(2-methacryloyloxyethyl phosphorylcholine) grafting markedly decreased wear in hip joint simulator tests, the clinical safety, and in vivo wear resistance of poly(2-methacryloyloxyethyl phosphorylcholine)-grafted highly cross-linked polyethylene liners remained open to question. Therefore, in the present study, we evaluated clinical and radiographic outcomes of poly(2-methacryloyloxyethyl phosphorylcholine)-grafted highly cross-linked polyethylene liners 5 years subsequent to total hip replacement in 68 consecutive patients. No reoperation was required for any reason, and no adverse events were associated with the implanted liners. The average Harris Hip Score increased from 38.6 preoperatively to 96.5 5 years postoperatively, and health-related quality of life, as indicated by the Short Form 36 Health Survey, improved. Radiographic analyses showed no periprosthetic osteolysis or implant migration. Between 1 and 5 years postoperatively, the mean steady-state wear rate was 0.002 mm/year, which represented a marked reduction relative to other highly cross-linked polyethylene liners, and appeared to be unaffected by patient-related or surgical factors. Although longer follow up is required, poly(2-methacryloyloxyethyl phosphorylcholine)-grafted highly cross-linked polyethylene liners improved mid-term clinical outcomes. The clinical safety and wear-resistance results are encouraging with respect to the improvement of long-term clinical outcomes with poly(2-methacryloyloxyethyl phosphorylcholine)-grafted highly cross-linked polyethylene liners. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2007-2016, 2017.

Short-term clinical and radiographic outcomes of total hip arthroplasty with PMPC-grafted highly cross-linked polyethylene liners against 32-mm femoral heads

“…In the first phase, the femoral head rapidly moves into the liner by a phenomenon known as “bedding-in,” which is largely attributed to permanent plastic deformation and settling of the liner in the metal shell [ 19 ]. Following previous study [ 12 ], “bedding-in,” was defined as 1 year operatively. In the second phase, the femoral head slowly moves into the liner; this movement is largely attributed to true wear (material loss in the form of particles) and is considered to define the “steady-state wear rate.” The present report uses these terms to describe the measurement results.…”

“…Previous hip simulator studies revealed that grafting reduced wear in HXLPE acetabular liners substantially [ 10 ]. The results of multicenter clinical trials of THA with PMPC-HXLPE acetabular liners, which begun in 2007 in Japan, reported that at 1 and 5 years postoperatively, the PMPC-HXLPE acetabular liner was an improved option for THA [ 11 , 12 ]. The clinical trials reported an improvement in the clinical scores, and no revision surgery due to PMPC-HXLPE acetabular liner degradation was required.…”

“…The rate of wear of the PMPC-HXLPE acetabular liner was 0.002 mm per year, which was significantly lower than of other untreated HXLPE acetabular liners. Although these findings suggested that PMPC-grafted HXLPE acetabular liners may be a promising approach to improve the longevity of artificial hip joints, the report [ 12 ] had several limitations. First, only one femoral head size (26 mm) was used for all the clinical trials.…”

MPC‐grafted highly cross‐linked polyethylene liners retrieved from short‐term total hip arthroplasty: Further evidences for the unsuitability of the MPC method

“…Conversely, the studied liners appeared to have serious problems of surface oxidation due to a relatively large amount of free radicals created both during manufacturing and as a consequence of MPC peeling off. A more recent follow‐up study which was co‐authored by a representative of Kyocera Medical Corp., performed on 80 patients which received such implants, reported no adverse reactions and lower wear rates when compared to not‐grafted liners, but the study did not include controls and the outstandingly low average wear rate measured (0.002 mm/year) resulted to be one order of magnitude lower than the data dispersion (0.023 mm/year), which suggests the presence of (unrealistic) negative wear rate values or a few exceptionally damaged liners which were not mentioned anywhere else in the document (Moro et al, 2017). Negative average wear rates and abnormal dispersions were indeed reported on the paper (table 6; Moro et al, 2017), rising concerns on the significance and objectivity of the study itself.…”

Controlled biointerfaces with biomimetic phosphorus-containing polymers

“…used in Japan; the hip joint is expected to last longer than conventional artificial hip joints [24].…”