Early Failure of Articular Surface Replacement XL Total Hip Arthroplasty

Abstract: The ASR (articular surface replacement) XL (DePuy, Warsaw, Ind) metal-on-metal hip arthroplasty offers the advantage of stability and increased motion. However, an alarming number of early failures prompted the evaluation of patients treated with this system. A prospective study of patients who underwent arthroplasty with the ASR XL system was performed. Patients with 2-year follow-up or any revision were included. Failure rates, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores, and radiographs were evaluated. Ninety-five patients (105 hips) were included. There were 16 revisions. Thirteen (12%) were aseptic acetabular failures. Eight were revised for aseptic loosening; 4, for metallosis; 1, for malposition; 2, for infection; and 1, for periprosthetic fracture. Mean time to revision was 1.6 years (0.18-3.4 years). The ASR XL with a revision rate of 12% is the second reported 1 piece metal-on-metal system with a significant failure rate at early follow-up. This particular class of implants has inherent design flaws that lead to early failure. Large diameter metal-on-metal articulations in total hip arthroplasty offers the theoretical advantage of improved stability and increased range of motion compared with smaller diameter bearings The ASR (articular surface replacement) XL total hip arthroplasty system by DePuy (Warsaw, Ind) was initially developed as an alternative to total hip arthroplasty. This total hip system offers a nonmodular metal-on-metal acetabular component, which was initially designed for hip surface replacements, paired with a large diameter femoral head. The acetabular cup is less than a hemisphere, allowing for greater range of motion as well as a degree of bone conservation. The ASR XL head system was then developed, which allowed surgeons to use traditional femoral stems to be matched with larger femoral heads. Although the less-than-hemispherical acetabulum offers a greater theoretical range of motion, the preparation and insertion of a nonmodular cup introduce possible technical errors that may account for early failures. Early failures of less than 2 years of large head metalon-metal hip systems have been reported in another 1 piece metal-on-metal syste

Drosophila melanogaster: A Valuable Genetic Model Organism to Elucidate the Biology of Retinitis Pigmentosa.

Retinitis pigmentosa (RP) is a complex inherited disease. It is associated with mutations in a wide variety of genes with many different functions. These mutations impact the integrity of rod photoreceptors and ultimately result in the progressive degeneration of rods and cone photoreceptors in the retina, leading to complete blindness. A hallmark of this disease is the variable degree to which symptoms are manifest in patients. This is indicative of the influence of the environment, and/or of the distinct genetic makeup of the individual.The fruit fly, Drosophila melanogaster, has effectively proven to be a great model system to better understand interconnected genetic networks. Unraveling genetic interactions and thereby different cellular processes is relatively easy because more than a century of research on flies has enabled the creation of sophisticated genetic tools to perturb gene function. A remarkable conservation of disease genes across evolution and the similarity of the general organization of the fly and vertebrate photoreceptor cell had prompted research on fly retinal degeneration. To date six fly models for RP, including RP4, RP11, RP12, RP14, RP25, and RP26, have been established, and have provided useful information on RP disease biology. In this chapter, an outline of approaches and experimental specifications are described to enable utilizing or developing new fly models of RP