The aims of the current study were to examine polyethylene particles in synovial fluid at an early stage, and to compare a newly introduced medial pivot total knee prosthesis with an established posterior-stabilized total knee prosthesis. Synovial fluid was obtained 1 year after knee arthroplasty from 17 patients with well-functioning prostheses (22 knees, 11 posterior-stabilized prostheses and 11 medial pivot prostheses) under complete sterile conditions. Polyethylene particles were isolated and analyzed by scanning electron microscopy. Particle size (equivalent circle diameter) was 0.78 ± 0.08 μm (mean ± standard error) in posterior-stabilized prostheses and 0.67 ± 0.06 μm in medial pivot prostheses. Particle shape (aspect ratio) was 2.30 ± 0.22 in posterior-stabilized prostheses and 1.90 ± 0.16 in medial pivot prostheses. The total numbers of particles were 1.16 ± 0.57 × 108 in posterior-stabilized prostheses and 9.01 ± 2.95 × 106 in medial pivot prostheses. Particles were smaller and rounder in medial pivot prostheses than in posterior-stabilized prostheses, but the differences were not significant. The difference in the common logarithm of particle number was significant. The medial pivot prosthesis generated less wear particles than the posteriorstabilized prosthesis, and these findings may have an impact on the incidence of osteolysis and aseptic loosening.
From the *Department of Orthopaedic Surgery, Osaka City University Medical School, Osaka, Japan; and the **Department of Orthopaedic Surgery, Osaka Rosai Hospital, Osaka, Japan.
The authors did not receive grants or outside funding in support of their research or preparation of this manuscript. They did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.
Reprint requests to Yukihide Minoda, MD, Department of Orthopaedic Surgery, Osaka City University Medical School, 1-4-3 Asahimachi Abeno-ku Osaka 545-8585, Japan. Phone: 81-6-6645-3851; Fax: 81-6-6646-6260; E-mail: firstname.lastname@example.org.