Abstract-A person with amputation's subjective perception is the only tool available to describe fit and comfort to a prosthetist. However, few studies have investigated the effect of alignment on this perception. The aim of this article is to determine whether people with amputation could perceive the alignment perturbations of their prostheses and effectively communicate them. A randomized controlled perturbation of angular (3 and 6 degrees) and translational (5 and 10 mm) alignments in the sagittal (flexion, extension, and anterior and posterior translations) and coronal (abduction, adduction, and medial and lateral translations) planes were induced from an aligned condition in 11 subjects with transtibial prostheses. The perception was evaluated when standing (static) and immediately after walking (dynamic) using software that used a visual analog scale under each alignment condition. In the coronal plane, Friedman test demonstrated general statistical differences in static (p < 0.001) and dynamic (p < 0.001) measures of perceptions with angular perturbations. In the sagittal plane, it also demonstrated general statistical differences in late-stance dynamic measures of perceptions (p < 0.001) with angular perturbations, as well as in early-stance dynamic measures of perceptions (p < 0.05) with translational perturbations. Fisher exact test suggested that people with amputation's perceptions were good indicators for coronal angle malalignments but less reliable when defining other alignment conditions.
Transcutaneous osseointegrated implants can improve function for select amputee patients, but infection serves as a significant limitation of implantable transcutaneous devices. This study examined the efficacy of an antimicrobial, pexiganan acetate (SUPONEX), and a porous tantalum implant material (Trabecular Metal) in preventing pin tract infection of osseointegrated implants in a rabbit model. Thirty-seven rabbits were randomized to three groups: Ti-control group (n = 11) with titanium alloy implant and no antimicrobial, Ti-Pexiganan group (n = 8) with titanium alloy implant and topical pexiganan acetate 1% applied daily at the skin/implant interface, and Ta-control group (n = 18) with porous tantalum implant and no antimicrobial. All implants were placed transcutaneously through skin, muscle, and bone. Rabbits were monitored for infection for 24 weeks. We observed a 75% reduction in rates of pin tract infection in the Ti-Pexiganan group compared to that observed in the Ti-control group (p = 0.019). No difference in rates of infection was observed between the Ta-control group and the Ti-control group (p = 0.230). In conclusion, pexiganan acetate may be an important antimicrobial for transcutaneous osseointegrated implants. Porous tantalum will not likely prevent pin tract infection without additional methods of soft tissue immobilization around the implant site.
Stress shielding from the presence of a femoral component can cause adverse changes to cortical bone geometry and porosity leading to increased fracture risk in the periprosthetic cortical bone. The objectives of this study were to determine if porosity increased after total hip arthroplasty along the principal axes, and to determine if a relationship existed between cortical bone porosity and geometry. Ten postmortem donors allowed comparisons of implanted femurs to the contralateral nonimplanted femurs. Transverse cross-sections of the femur were taken at 25, 45, 65, and 85% along the length of the femoral component. The cortical bone principal axes' location (degrees) and rigidity values (mm(4)) were based on cortical bone geometry by using digitized images of the cortical bone cross-sections. Percent porosity was measured along the principal axes using backscatter electron imaging. Cortical bone porosity increased in the more distal sections of the implanted femurs by approximately 3%, but did not preferentially increase along a particular principal axis. No correlation was found between changes in porosity and rigidity values. In conclusion, the porosity increases in the implanted femurs may have regionally reduced cortical bone strength. The locations of higher porosity did not appear related to the cortical bone geometry.
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