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Clinical outcomes of primary total hip arthroplasty with PMPC-grafted highly cross-linked polyethylene liners

Toru Moro1, 2, Yoshio Takatori2, Sakae Tanaka2*, Hiromi Oda3, Takashige Umeyama4, Eisei Fukatani5*, Hideya Ito6, Masayuki Kyomoto1, 7, Hirofumi Oshima1, 2, Takeyuki Tanaka2, Hiroshi Kawaguchi8 and Kazuhiko Ishihara9
  • 1 The University of Tokyo, Division of Science for Joint Reconstruction, Graduate School of Medicine, Japan
  • 2 The University of Tokyo, Sensory & Motor System Medicine, Faculty of Medicine, Japan
  • 3 Saitama Medical University School of Medicine, Department of Orthopaedic Surgery, Japan
  • 4 NTT Medical Center Tokyo, Department of Orthopedic Surgery, Japan
  • 5 JR Tokyo General Hospital, Department of Orthopaedic Surgery, Japan
  • 6 Japan Red Cross Medical Center, Department of Orthopaedic Surgery, Japan
  • 7 KYOCERA Medical Corporation, Research Department, Japan
  • 8 Tokyo Shinjuku Medical Center, Japan Community Health Care Organization, Japan
  • 9 The University of Tokyo, Department of Materials Engineering, School of Engineering, Japan

Introduction: Total hip arthroplasty (THA) is an established treatment modality for patients with end-stage hip disorders such as osteoarthritis and rheumatoid arthritis. However, periprosthetic osteolysis has been recognized as a notable complication affecting the long-term survival of THA; extensive research has shown that wear particles from the polyethylene (PE) liner are responsible for osteolysis. Recent observations of the healthy mammalian articular cartilage surface have disclosed that it is covered with a nanometer-scaled phospholipid layer that protects the articulating surface from mechanical wear and facilitates a smooth motion of joints during daily activities. Hence, the grafting of phospholipid-like polymer layer on the liner surface may mimic the surface conditions of healthy articular cartilage. Aiming at reduction of wear particles and elimination of periprosthetic osteolysis, we have successfully produced a highly cross-linked polyethylene (HXLPE) liner with a surface grafting (100–200 nm in thickness) of phospholipid polymer, poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC). Although our previous in vitro findings showed that PMPC-grafted particles caused no subsequent bone resorptive responses, and PMPC grafting markedly decreased wear in hip joint simulator tests, in vitro findings do not always translate to clinical success. The purpose of this study was to investigate clinical safety and wear-resistance of PMPC-grafted HXLPE liner in primary THAs.

Materials and Methods: Eighty consecutive patients underwent cementless THA using a 26-mm diameter CoCrMo alloy femoral head and a PMPC-grafted HXLPE liner for the bearing couplings. We evaluated the clinical and radiographic outcomes of 68 patients (M/F, 13/55) at 5 years after the index surgery. The mean age of the patients was 64.1 years and mean BMI was 22.5 kg/m2.

Results: No adverse events suspected to correlate with the implanted PMPC-grafted HXLPE liner were recorded, and no revision operations were performed during the follow-up period. The average of Harris hip score improved from 41.0 preoperatively to 96.5 at 5 years postoperatively. On radiographic analyses, neither periprosthetic osteolysis nor femoral component migration was detected in all patients. The mean amount of penetration during the first year was 0.225 mm. Between 1 and 5 years, the mean amount of the steady wear rate was 0.002 mm/year, representing a nearly 90% reduction compared with the mean wear rate of other HXLPE liners.

Discussion: The MPC polymers are biocompatible and hydrophilicity-controllable due to phosphorylcholine groups in the side chain resembling phospholipids of biomembrane. Thus, the MPC polymers can suppress biological reactions even when they are in contact with living organisms, and is now clinically used on the surfaces of many medical devices. Although the safety of MPC polymers as a biomaterial is well established, the influence of PMPC-grafted HXLPE liners on the health of patients remains an open question. In the present study, clinical and radiographic examinations demonstrated results comparable to other contemporary THAs. Moreover, two-dimensional linear wear rate was dramatically improved.

Conclusion: We concluded that the lines of results obtained in this study clearly demonstrate safety and wear-resistance of PMPC-grafted HXLPE liners. This preliminary observation is still short clinical term. Hence, future observations may be to support this result

Keywords: Biomimetic, joint replacement, clinical application, Implant wear

Conference: 10th World Biomaterials Congress, Montréal, Canada, 17 May - 22 May, 2016.

Presentation Type: Poster

Topic: Biomaterials in musculoskeletal orthopeadics and tissues

Citation: Moro T, Takatori Y, Tanaka S, Oda H, Umeyama T, Fukatani E, Ito H, Kyomoto M, Oshima H, Tanaka T, Kawaguchi H and Ishihara K (2016). Clinical outcomes of primary total hip arthroplasty with PMPC-grafted highly cross-linked polyethylene liners. Front. Bioeng. Biotechnol. Conference Abstract: 10th World Biomaterials Congress. doi: 10.3389/conf.FBIOE.2016.01.01696

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Received: 27 Mar 2016; Published Online: 30 Mar 2016.

* Correspondence:
Dr. Sakae Tanaka, The University of Tokyo, Sensory & Motor System Medicine, Faculty of Medicine, Tokyo, Japan, TANAKAS-ORT@h.u-tokyo.ac.jp
Dr. Eisei Fukatani, JR Tokyo General Hospital, Department of Orthopaedic Surgery, Tokyo, Japan, Email1