Enhanced wear performance of highly crosslinked UHMWPE for artificial joints.

It is well known that osteolysis induced by polyethylene wear debris is the main cause of long-term failure of hip and knee prostheses. We developed a treatment of medical-grade ultra-high molecular-weight polyethylene (UHMWPE) in order to improve its tribologic properties and reduce its wear. Medical-grade UHMWPE was irradiated with a 200 kGy dose of radiation, thermally stabilized at a temperature close to the melting point, and then sterilized with ethylene oxide. The irradiation treatment was performed to crosslink the UHMWPE. The thermal stabilization treatment, contributing to the reaction between the free radicals generated by the irradiation process, was chosen to enhance crosslinking and to prevent oxidation and the shortening of chains. The non-invasive sterilization process with ethylene oxide was chosen to prevent the re-formation of free radicals. The wear performance of this material was compared to UHMWPE, untreated or treated with different sterilization techniques, using gamma and beta irradiation. Insoluble crosslinked constituents were measured with an extraction method. Wear was evaluated using a flat-on-ring wear test machine. While small differences were found among the different sterilization processes, 200 kGy-irradiated UHMWPE followed by thermal treatment and sterilization with ethylene oxide had the least wear and the greatest amount of crosslinking.

Hyperfractionation versus conventional fractionation in oropharyngeal carcinoma: final analysis of a randomized trial of the EORTC cooperative group of radiotherapy.

EORTC protocol 22791 compared once daily fractionation (CF) of 70 Gy in 35-40 fractions in 7-8 weeks, to pure hyperfractionation (HF) of 80.5 Gy in 70 fractions in 7 weeks using 2 fractions of 1.15 Gy per day, in T2-T3 oropharyngeal carcinoma (excluding base of tongue), N0,N1 of less than 3 cm. From 1980 to 1987, 356 patients were entered. In the final analysis (June 1990), the local control was significantly higher (p = 0.02 log-rank) after HF compared with CF. At 5 years, 59% of patients are local disease-free in the HF arm compared to 40% in the CF arm. The superiority of HF was demonstrated in patients staged T3N0,T3N1 but not in T2. The Cox model confirmed that the treatment regimen was an independent significant prognostic factor for locoregional control (p = 0.007 log-rank). This improvement of locoregional control was responsible for a trend to an improved survival (p = 0.08 log-rank). There was no difference in late normal tissue damage between the two treatment modalities.

Veno-occlusive disease in children after intensive chemo- and radiotherapy and repeated halothane anesthesias. A report of 2 cases.

Two cases of veno-occlusive disease (VOD) occurring in metastatic neuroblastoma patients are reported. Treatment included a remission induction by conventional chemotherapy and surgery followed by an early consolidation with massive chemotherapy, total body irradiation and cleared autologous bone marrow transplantation (ABMT). Both patients had multiple halothane anesthesias. Liver complications occurred 10 and 21 days respectively after ABMT. The first patient had a precocious and severe clinical and biological VOD, heparinotherapy and symptomatic treatment were ineffective and he died 12 days after ABMT. The second patient had a moderate and later syndrome which was controlled by heparin therapy (100 U/kg/day) delivered by continuous infusion; he is now alive free of hepatic disturbance 28 months after ABMT. The potential iatrogenic factors are discussed, with special focus on the use of halogenated anesthetic drugs.