Fifteen Year Outcome of the Ceraver Hermes Posterior-Stabilized Total Knee Arthroplasty: Safety of the Procedure with Experienced and Inexperienced Surgeons

We wished to determine whether total knee replacement (TKA) performed by young surgeons increased rates of mortality and complications compared with TKA performed by senior surgeons using the same model of arthroplasty. There were no significant pre-operative differences between the groups in terms of age, gender, height, weight, body mass index, diagnosis, comorbidity and duration of follow-up, which was a mean of 15 years in both groups. Hence, we assessed the 15 year survival of the first 150 Ceraver Posterior-Stabilized total knee arthroplasties undertaken by young surgeons (aged of less than 30 years) in formation in a single university hospital setting (Group B). We used survival curve analysis, with strict definitions regarding end-points, and evaluated a number of different endpoint criteria to assess the outcome and to compare the results with those obtained by the two seniors (aged of more than 40 years) with their 50 first implantations (Group A). The clinical results and survival rate of implants at intermediate to long-term follow-up were similar in both Groups. Kaplan-Meier survival analysis, with revision as the endpoint for failure, showed that the rate of survival at ten years was 96% (95% CI, 93 to 100) in both groups. At fifteen years the rate of survival was 91% (95% CI, 85 to 97) in group B, and 92% (95% CI, 90 to 94) in group A. The implant used in this series appears particularly safe since the usual complications observed with posterior stabilized arthroplasties were not observed even with young surgeons

Two stage fracture of a polyethylene post in a 9-year-old posterior-stabilized knee prosthesis: a case report

<p>Abstract</p> <p>Introduction</p> <p>Several cases of tibial post breakage are reported in the literature. To the best of our knowledge, only three cases of NexGen knee prosthesis (Zimmer, Warsaw, Indiana, USA) tibial post failure have been reported.</p> <p>Case presentation</p> <p>In November 1999, a 63-year-old Caucasian woman from Italy with a history of symptomatic left knee osteoarthritis underwent a total knee arthroplasty. In March 2008, while rising from a chair, she felt a sudden pain and instability in her left knee. She reported a fracture of the polyethylene post of the tibial insert. No malposition or malalignment of either the femoral or tibial components were identified. The polyethylene tibial insert was studied under light microscopy and scanning electron microscopy. The fracture was also noted to have occurred without any notable polyethylene wear.</p> <p>Conclusion</p> <p>Scanning electron microscopy revealed two different damage patterns that could be explained with a two-stage rupture of our patient's polyethylene post. This could have been caused by a non-optimal ligamentous balancing during first implant surgery. Her knee probably developed a varus instability that weakened the post, and then a posterior anterior stress finally broke the polyethylene.</p

Environmental Predictors of Seasonal Influenza Epidemics across Temperate and Tropical Climates

Human influenza infections exhibit a strong seasonal cycle in temperate regions. Recent laboratory and epidemiological evidence suggests that low specific humidity conditions facilitate the airborne survival and transmission of the influenza virus in temperate regions, resulting in annual winter epidemics. However, this relationship is unlikely to account for the epidemiology of influenza in tropical and subtropical regions where epidemics often occur during the rainy season or transmit year-round without a well-defined season. We assessed the role of specific humidity and other local climatic variables on influenza virus seasonality by modeling epidemiological and climatic information from 78 study sites sampled globally. We substantiated that there are two types of environmental conditions associated with seasonal influenza epidemics: “cold-dry” and “humid-rainy”. For sites where monthly average specific humidity or temperature decreases below thresholds of approximately 11–12 g/kg and 18–21°C during the year, influenza activity peaks during the cold-dry season (i.e., winter) when specific humidity and temperature are at minimal levels. For sites where specific humidity and temperature do not decrease below these thresholds, seasonal influenza activity is more likely to peak in months when average precipitation totals are maximal and greater than 150 mm per month. These findings provide a simple climate-based model rooted in empirical data that accounts for the diversity of seasonal influenza patterns observed across temperate, subtropical and tropical climates