Abstract-Management of residual limb volume affects decisions regarding timing of fit of the first prosthesis, when a new prosthetic socket is needed, design of a prosthetic socket, and prescription of accommodation strategies for daily volume fluctuations. This systematic review assesses what is known about measurement and management of residual limb volume change in persons with lower-limb amputation. Publications that met inclusion criteria were grouped into three categories: group I: descriptions of residual limb volume measurement techniques; group II: studies investigating the effect of residual limb volume change on clinical care in people with lower-limb amputation; and group III: studies of residual limb volume management techniques or descriptions of techniques for accommodating or controlling residual limb volume. We found that many techniques for the measurement of residual limb volume have been described but clinical use is limited largely because current techniques lack adequate resolution and insocket measurement capability. Overall, limited evidence exists regarding the management of residual limb volume, and the evidence available focuses primarily on adults with transtibial amputation in the early postoperative phase. While we can draw some insights from the available research about residual limb volume measurement and management, further research is required.

An in vivo study was conducted to assess the sensitivity of fibrous capsule thickness and macrophage density to polymer fiber diameter. Single polypropylene fibers of diameters ranging from 2.1 to 26.7 microm were implanted in the subcutaneous dorsum of Sprague-Dawley rats. Results at 5 weeks demonstrated reduced fibrous capsule thickness for small fibers. Capsule thickness was 0.6 (+/-1.8) microm, 11.7 (+/-12.0) microm, 20.3 (+/-11.6) microm, and 25.5 (+/-10.0) microm for fibers in the ranges of 2.1 to 5.9, 6.5 to 10.6, 11.1 to 15.8, and 16.7 to 26.7 microm, respectively. Fibers very near to blood vessels had smaller capsules than did those with local vasculature further away. The macrophage density in tissue with fiber diameters 2.1 to 5.9 microm (23.03 +/- 8.67%) was comparable to that of unoperated contralateral control skin (18.72+/-10.06%). For fibers with diameters in the ranges of 6.5 to 10.6, 11.1 to 15.8, and 16.7 to 26.7 microm, macrophage densities were 33.90+/-13.08%, 34.40+/-15.77%, and 41.68+/-13.98%, respectively, all of which were significantly larger (p<0.002) than that for the control. The reduced fibrous capsule thickness and macrophage density for small fibers (<6 microm) compared with large fibers could be due to the reduced cell-material contact surface area or to a curvature threshold effect that triggers cell signaling. A next step will be to extend the analysis to meshes to evaluate fiber-spacing effects on small-fiber biomaterials.

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A preliminary investigation was conducted to characterize the magnitude and distribution of volume change in transtibial residua at two time intervals: upon prosthesis removal and at 2 week intervals. Six adult male unilateral transtibial amputee subjects, between 0.75 and 40.0 years since amputation, were imaged 10 times over a 35-minute interval with a custom residual limb optical scanner. Volume changes and shape changes over time were assessed. Measurements were repeated 2 weeks later. Volume increase on socket removal for the six subjects ranged from 2.4% to 10.9% (median 6.0% ± standard deviation 3.6%). Rate of volume increase was highest immediately upon socket removal and decreased with time (five subjects). In four subjects, 95% of the volume increase was reached within 8 minutes. No consistent proximal-to-distal differences were detected in limb cross-sectional area change over time. Limb volume differences 2 weeks apart ranged from −2.0% to 12.6% (0.6% ± 5.5%) and were less in magnitude than those within a session over the 35-minute interval (five subjects). Multiple mechanisms of fluid movement may be responsible for short-term volume changes, with different relative magnitudes and rates in different amputees.Abbreviations: A/P = anterior/posterior, CSA = crosssectional area, M/L = medial/lateral, MRI = magnetic resonance imaging, OSS = optical surface scanner, PTB = patellar tendon bearing, SD = standard deviation, SXCT = spiral x-ray computed tomography, 3-D = three-dimensional, TSB = total surface bearing, TT = transtibial.

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The purpose of this study was to assess a new scaffold design for muscle tissue engineering: arrays of parallel-oriented polymer microfibers. First, C2C12 skeletal myoblasts were seeded onto single, laminin-coated polypropylene fibers and their growth and alignment were characterized. With the aim of creating skeletal muscle sheets, it was then investigated whether cell layers of single fibers merged when in close proximity to neighboring fibers. The optimal fiber spacing needed to achieve cell alignment with the lowest possible content of scaffold material was established. Further, it was assessed whether such a cell sheet became contractile and whether it survived in vitro for extended periods of time. C2C12 cells, cultured on fibers 10 to 15 microm in diameter, formed up to 50-microm-thick layers of longitudinally aligned cells. Four different groups based on fiber spacing (30 to 35, 50 to 55, 70 to 75, and 90 to 95 microm) were evaluated. Complete cell sheets formed between fibers that were spaced 55 microm apart or less; larger spacing led to no or incomplete sheets. C2C12 cells, seeded onto a 10 x 20 mm fiber array, formed a contractile cell sheet that was maintained in vitro for 70 days. Larger, three-dimensional structures might be created by arranging fibers in several layers or by stacking cellular sheets.

Tissue response to single polymer microfibers of polyester (PET), polyethylene (PE), poly(L-lactic acid) (PLA), and polyurethane (PU) was assessed using a rat subcutaneous model. Fibers of diameters ranging from 1 to 15 microm were aligned parallel to each other on polycarbonate frames and implanted in the subcutaneous dorsum in the subscapular region. After 5 weeks of implantation, fibrous capsule thickness was significantly less for fibers of diameters 1-5 than for those of 11-15 microm for all polymers tested. For PET and PU, 75.0 and 71.4% respectively of the 1-5 microm fibers had no capsule, while for PE and PLA only 45.5 and 56.3% respectively had no capsule. For 1-5 microm fibers, PE had significantly thicker capsules than PET and PU. Reducing fiber diameters from 6-10 to 1-5 microm induced a greater reduction in capsule thickness than changing polymers among PET, PE, and PLA. PU showed the least encapsulation of all polymers, demonstrating significantly thinner capsules than PET, PE, and PLA for 6-10 and 11-15 microm fibers.