Yoshio Takatori

Clinical and Laboratory Wear Studies of Zirconia-on-UHMWPE Combination in Cementless THA

We investigated the wear performance of zirconia femoral heads in vivo and in vitro. The in vivo wear rate of polyethylene against the conventional zirconia heads in cementless THA was 0.139 mm/year, which is relatively satisfactory as compared to the reported wear rates of metal-backed polyethylene against metal heads. However, there still exist some problems concerning the degradation of zirconia. Therefore, the present manufacturer has improved the conventional zirconia. The results of hip simulator testing using the improved zirconia heads were satisfactory. Thus, the current improved zirconia which is more resistant to the degradation would contribute to the polyethylene wear reduction over the extended periods. Introduction Zirconia ceramics (Y-TZP) possess high mechanical strength and excellent wear properties, which have been confirmed in numerous in vitro studies [1]. In 1985, zirconia ceramics were successfully introduced into clinical use as femoral heads in articulation with ultrahigh molecular weight polyethylene components in THA. On the other hand, there have been some concerns about the low temperature degradation associated with the long-term implantation. Therefore, zirconia ceramics have been improved by several manufacturers to eliminate such degradation. There still are only a few studies about the clinical wear behavior of zirconia-on-polyethylene bearing combination. In the present study, we measured the clinical wear of polyethylene against the conventional zirconia. In addition, we investigated the wear properties of the improved zirconia especially when articulated with crosslinked polyethylene (CPE) in the hip simulator wear tests, because CPE has recently been expected to reduce wear debris dramatically. Based on these data, we discussed the effectiveness of zirconia as one of alternate bearing materials. Materials and Methods Clinical wear measurement: Between 1992 and 1994, as a multicenter clinical trial in Japan, a total of 94 hips undergone cementless THA using a Kobelco H-5 system (Kobe Steel Ltd., Kobe, Japan), in which a 22 or 26mm modular zirconia head was used. The mechanical properties of zirconia are shown in Table 1. Among these cases, we investigated 74 hips radiographically as to the linear wear of polyethylene liner. Zirconia heads were sterilized by EtO and polyethylene liners and metal implants were sterilized with gamma irradiation. Key Engineering Materials Online: 2003-05-15 ISSN: 1662-9795, Vols. 240-242, pp 823-826 doi:10.4028/www.scientific.net/KEM.240-242.823

Pseudotumour occurring after a metal-on-metal total hip arthroplasty that was diagnosed based on venous congestion in unilateral leg: a case report

Abstract Pseudotumours, caused by an adverse reaction to metal debris (ARMD), are cystic or solid lesions that develop after metal-on-metal total hip arthroplasty (THA). They often lead to rapid osteolysis and muscle necrosis. To prevent consequent loosening of implants, early diagnosis is important. We report a rare case in which venous congestion in unilateral leg enabled the early diagnosis of ARMD. Three years and ten months after undergoing metal-on-metal THA for osteoarthritis, an 83-year-old woman experienced oedema in her lower extremity. Contrast-enhanced computed tomography and magnetic resonance imaging revealed a mass with fluid component that originated from the artificial hip joint and was compressing the external iliac vein. We performed resection of the mass and revision of the THA. The pathological findings from the resected mass revealed necrotic tissue and infiltrating inflammation cells, which is compatible with the diagnosis of ARMD. There was little solid component found inside the mass, and there was no loosening of prosthesis. The patient’s venous congestion improved immediately following the resection. When unilateral leg oedema or venous congestion are observed in cases with a history of metal-on-metal THA, the possibility of ARMD-induced pseudotumour should be taken into consideration.