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Microcellular injection molding (MIM) of thermoplastics is a challenging molding process compared to conventional injection molding (IM) process because of its narrow processing window. As far as microcellular molding of open-celled foam is concerned, it is much more difficult because of extremely narrow processing window for open-cell foam and transient nature of melt temperature and pressure inside cavity during the molding process. However, it is expected that molding of open-celled microcellular foam may open many new areas such as tissue engineering, drug delivery, reverse osmosis, dialysis membranes, and fuel cell. The production cost may also be reduced manifolds. In present work a novel expandable cavity mold (EC mold) was designed and fabricated. EC mold has some nonconventional features like pneumatically actuated gate seal, mechanism for cavity expansion, and arrangement for cyclic heating-cooling of core and cavity blocks. In present study polylactic acid (PLA), a biodegradable polymer, was used and expandable cavity molding (EC molding) variables, namely, cavity expansion rare (mm/s), cavity expansion distance (mm), and cavity expansion-compression-expansion (ECE) profile mode, were studied. The results confirm molding of PLA foams with very high cell density and impinged structure. The micrographs and open-cell ratio confirm the formation of PLA foam with ~40% open-cell content. [ABSTRACT FROM AUTHOR]

Background: The standard commercially available marketed prostheses sometimes may not be the best fit to Indian patients because of the large anatomic variation. Orthopedic surgeons always stress the need for a proper implant-patient match in hip joint replacements, in particular, for a cementless femoral stem. The complications of mismatch are aseptic loosening, improper load distribution, and discomfort. The present study was undertaken to compare the differences in dimensions between femurs of elderly Indians and those of populations from other regions in order to solve the problem of a possible geometric mismatch between a selected implant and the hip joint as far as Indian patients are concerned. Materials and Methods: Measurements were made using computer aided design techniques on computed tomography (CT) scanned images of 98 femurs (56 left and 42 right). The software used to convert the CT images into solid models was MIMICS® (Materialize, Inc., Leuven, Belgium). The geometrical parameters, viz., the femoral head offset, femoral head center (HC), femoral head diameter, femoral head relative position, position of shaft isthmus, neck-shaft angle, bow angle, femoral neck length, canal flare index, femoral length, and canal width at various locations, were chosen to design best-fit standard femoral stems for cementless insertion. These data were compared with the published data of other countries. Results: A difference of 16.8% was found in the femoral head offset between Indian and Swiss populations, which can affect soft tissue tension and range of motion. At a distance of 20 mm above the lesser trochanter (LT), the anteroposterior (AP) canal width was found to differ by 45.4%, when compared with a French population which can affect the mechanical stability of femoral stem. Femoral dimensions of Indian male and female subjects have also been compared and differences evaluated. At the LT, the aspect ratio (ratio of mediolateral canal width and AP canal width) in case of males (1.198) is approximately13% higher than that of females (1.059). Conclusions: This study indicates a need for redesign of femoral stems. The obtained anthropometric femoral dimensions can be used to design and develop indigenous hip joint prosthesis in India. The results of this study can also be used in forensic anthropometric studies. [ABSTRACT FROM AUTHOR]