Objectives: To examine periprosthetic bone remodeling among the recipients of 2 types of lower-limb osseointegrated systems, the Integral Leg Prosthesis (ILP) and the Osseointegration Prosthetic Limb (OPL) type A, over a >24-month period. Design: Retrospective cohort study. Setting: Private hospital, with a specialized osseointegration unit. Patients: Twenty-eight patients with transfemoral lower-limb amputations were fitted with osseointegrated systems. Of these patients, 15 received the ILP and 13 the OPL osseointegrated implant. Intervention: Radiographic measurements were taken at baseline (0.4 ± 0.5 years) and at follow-up (3.0 ± 0.8 years) after the osseointegration procedure. Main Outcome Measurements: Radiographic bone density, longitudinal bone coverage, and bone width outcomes were measured in inverse “Gruen zones.” Bone remodeling was evaluated by comparing changes between baseline and follow-up measurements. Results: Radiographic bone density decreased in all zones among both ILP and OPL groups. Cortical bone thickness increased among the OPL group in zones 3 (P < 0.05) and 5 (P < 0.05). Distal bone coverage of the ILP implant decreased by 2.3% (P < 0.01) and 4.1% (P < 0.05) of the total implant length on the medial and lateral sides, respectively. Conclusions: Decreased bone density with increased periprosthetic cortical thickness suggests a change in the bone architecture for the OPL group. The findings of this study raise concerns for the long-term success of the ILP implant. Radiographic analysis of x-rays seems to be a useful tool for clinicians to evaluate bone remodeling around osseointegrated prosthesis. Level of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.
Mobility outcomes and changes in bone mineral density (BMD) of the spine and femoral necks in response to unilateral osseointegrated implants was investigated over a 3-year period. A total of 48 unilateral amputees who received an osseointegrated implant, comprising 33 trans-femoral amputees (TFA) and 15 trans-tibial amputees (TTA), underwent dual-energy X-ray absorptiometry (DXA) scans of the lumbar spine (L2-L4) and femoral necks at baseline, 1-, and 3-years follow-ups. Mobility outcomes, including the Six-Minute-Walk Test (6MWT) and Timed-Up-and-Go (TUG), were measured before surgery, at 1 year, and more than 2 years following the osseointegration procedure. We observed a significant increase (p < 0.05) in Z-score values in the femoral neck of the amputated side in TFA patients without a femoral neck lag screw at the 1-and 3-year follow-ups, as well as in TFA patients with a lag screw present at 3-year follow-up. The BMD at 1-year follow-up was found to be positively correlated with pre-surgery 6MWT values in patients who were mobile using a traditional socket prosthesis before receiving an osseointegrated implant. These results suggest that osseointegrated implants induce a physiological response in the femoral neck of recipients and appear to be evidence of restored biomechanical loading in the proximal femur.
Hydroxyapatite (HA) is a widely studied biomaterial for its similar chemical composition to bone and its osteoconductive properties. The crystal structure of HA is flexible, allowing for a wide range of substitutions which can alter bioactivity, biodegradation, and mechanical properties of the substituted apatite. The thermal stability of a substituted apatite is an indication of its biodegradation in vivo. In this study, we investigated the thermal stability and mechanical properties of manganese-substituted hydroxyapatite (MnHA) as it is reported that manganese can enhance cell attachment compared to pure HA. Pure HA and MnHA pellets were sintered over the following temperature ranges: 900 to 1300 °C and 700 to 1300 °C respectively. The sintered pellets were characterized via density measurements, mechanical testing, X-ray diffraction, and field emission electron microscopy. It was found that MnHA was less stable than HA decomposing around 800 °C compared to 1200 °C for HA. The flexural strength of MnHA was weaker than HA due to the decomposition of MnHA at a significantly lower temperature of 800 °C compared to 1100 °C for HA. The low thermal stability of MnHA suggests that a faster in vivo dissolution rate compared to pure HA is expected.
All forms of terrestrial life include cellular machinery to transform and regulate chemical energy flow through electron‐transfer pathways reliant upon key classes of biological redox molecules; life that evolved elsewhere, presumably, would possess a similar possibly overlapping set of energy‐management molecules. A second set of universal processes in terrestrial biology encompasses enzymatic change to add or remove functional groups, such as phosphate moieties, to biomolecules for a variety of purposes, from managing energy flow to tuning protein function; electrochemical assays can detect such enzymes. Thus, measurement of biological redox activity is a promising means to search for two major classes of life indicators as a component of future exploration missions to the “ocean worlds” of our solar system, those bodies that support substantial liquid oceans. Here, we assay a representative set of life‐critical redox molecules in synthetic seawater (SW) using electrochemical techniques. We also appropriate a well‐developed electrochemical assay that indicates the presence of phosphatase(s) by comparing the redox signatures of a substrate for, and the product of, the enzymatic process. We report measured limits of detection in SW as low as 10 nM for naturally occurring redox molecules and 3.1 aM for alkaline phosphatase over a 60‐minute period, demonstrating the promise and sensitivity of electrochemical sensors as effective life‐detection tools for future ocean worlds missions.
Electrochemistry offers a wide range of analytical sensing capability and is therefore suited to serve a variety of NASA missions. Advancements in miniaturization and automation in addition to inherent high sensitivity and specificity have made electrochemical sensors especially attractive. Here, we present recent developments for use of electrochemical sensors in planetary exploration and human exploration missions. This article highlights research developments in the area of electrochemical sensors as presented at the Electrochemistry in Space symposium at the 236th ECS Meeting on October 16, 2019 in Atlanta, GA.
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