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This study quantified and compared the efficacy of in-shoe orthoses and ankle braces in stabilizing the hindfoot and medial longitudinal arch in a cadaveric model of acquired flexible flatfoot deformity. This was addressed by combining measurement of hindfoot and arch kinematics with plantar pressure distribution, produced in response to axial loads simulating quiet standing. Experiments were conducted on six fresh-frozen cadaveric lower limbs. Three conditions were tested: intact-unbraced; flatfoot-unbraced; and flatfoot-braced. Flatfoot deformity was created by sectioning the main support structures of the medial longitudinal arch. Six different braces were tested including two in-shoe orthoses, three ankle braces and one molded ankle-foot orthosis. Our model of flexible flatfoot deformity caused the calcaneus to evert, the talus to plantarflex and the height of the talus and medial cuneiform to decrease. Flexible flatfoot deformity caused a pattern of medial shift in plantar pressure distribution, but minimal change in the location of the center of pressure. Furthermore, in-shoe orthoses stabilized both the hindfoot and the medial longitudinal arch, while ankle braces did not. Semi-rigid foot and ankle orthoses acted to stabilize the medial longitudinal arch. Based on these results, it was concluded that treatment of flatfoot deformity should at least include use of in-shoe orthoses to partially restore the arch and stabilize the hindfoot.

Gaseous CO2 was used as an antisolvent to induce the fractional precipitation of alkaline phosphatase, insulin, lysozyme, ribonuclease, trypsin, and their mixtures from dimethylsulfoxide (DMSO). Compressed CO2 was added continuously and isothermally to stationary DMSO solutions (gaseous antisolvent, GAS). Dissolution of CO2 was accompanied by a pronounced, pressure‐dependent volumetric expansion of DMSO and a consequent reduction in solvent strength of DMSO towards dissolved proteins. View cell experiments were conducted to determine the pressures at which various proteins precipitate from DMSO. The solubility of each protein in CO2‐expanded DMSO was different, illustrating the potential to separate and purify proteins using gaseous antisolvents. Polyacrylamide gel electrophoresis in sodium dodecyl sulfate (SDS‐PAGE) was used to quantify the separation of lysozyme from ribonuclease, alkaline phosphatase from insulin, and trypsin from catalase. Lysozyme biological activity assays were also performed to determine the composition of precipitates from DMSO initially containing lysozyme and ribonuclease. SDS‐PAGE characterizations suggest that the composition and purity of solid‐phase precipitated from a solution containing multiple proteins may be accurately controlled through the antisolvent's pressure. Insulin, lysozyme, ribonuclease, and trypsin precipitates recovered substantial amounts of biological activity upon redissolution in aqueous media. Alkaline phosphatase, however, was irreversibly denaturated. Vapor‐phase antisolvents, which are easily separated and recovered from proteins and liquid solvents upon depressurization, appear to be a reliable and effective means of selectively precipitating proteins. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 62: 247–258, 1999.

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