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Journal of Biomaterials Applications, Vol. 21, No. 2, 131-145 (2006) DOI: 10.1177/0885328206058786 Determination of Crystallinity and Crystal Structure of HylamerTM Polyethylene after in vivo WearLaboratorio di Tecnologia Medica Istituti Ortopedici Rizzoli, Bologna 40136, Italy, visentin{at}tecno.ior.it
Laboratorio di Tecnologia Medica Istituti Ortopedici Rizzoli, Bologna 40136, Italy
Laboratorio di Tecnologia Medica Istituti Ortopedici Rizzoli, Bologna 40136, Italy
Dipartimento di Biochimica G. Moruzzi Sez di Chimica e Propedeutica Biochimica Bologna 40126, Italy
Dipartimento di Biochimica G. Moruzzi Sez di Chimica e Propedeutica Biochimica Bologna 40126, Italy
ITOI - CNR, Unita di Bologna c/o Istituti Ortopedici Rizzoli Bologna 40136, Italy
I Divisione di Ortopedia e Traumatologia Istituti Ortopedici Rizzoli, Bologna 40136, Italy HylamerTM polyethylene is a crystalline form of polyethylene of 70% crystallinity whereas conventional polyethylene (PE) has 50% crystallinity. Crystallinity is the percentage by weight of the crystalline phase present in the whole polymer, which comprises both amorphous and crystalline phases. Clinical experience has shown that HylamerTM components used in joint prostheses, if sterilized by gamma rays in the presence of oxygen, are easily affected by wear, which leads to osteolysis. The authors have analyzed the crystallinity of polyethylene liners removed from seven patients who had received HylamerTM polyethylene implants sterilized by gamma rays in air and had suffered prosthetic loosening, using Raman spectroscopy coupled with partial least squares (PLS) analysis. The results have been compared to those of two controls who had received HylamerTM polyethylene implants sterilized by gamma irradiation in a nitrogen atmosphere. The crystal structure of wear particles released into the tissues from the HylamerTM liners sterilized by gamma rays in air is also studied. The materials undergoing two different types of sterilization methods show different crystallinity values (71.50 vs. 69.43), but the crystallinity do not change according to wear (worn and unworn liner region). Both monoclinic and orthorhombic phases are present in the liner, while in wear debris prevalently monoclinic crystals are found in both types of sterilized liners. Different crystallinity rates can explain different wear rates observed in vivo.
Key Words: crystallinity polyethylene wear HylamerTM Raman spectroscopy
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