RESUMEN

BACKGROUND: Post-operative non-compliance is a risk factor for fracture fixation failure and presents a challenge for revision surgery planning. We present a patient who underwent revision surgery for a proximal humerus fracture with lateral locked plating augmented with a UV light activated intramedullary implant. CASE: A 45-year-old woman with a history of alcoholism presented with a proximal humerus fracture. After undergoing open reduction internal fixation with a lateral locking plate, the patient suffered a fall secondary to delirium tremens. New radiographs demonstrated displacement of the fracture with failure of screws. Revision surgery consisting of removal of the initial construct as well as open reduction internal fixation via lateral locking plate, augmented with a UV-activated intramedullary cement implant, was performed. CONCLUSION: This is the first case report describing the use of a UV-activated intramedullary cement implant to augment the use of lateral locked plating for proximal humerus fractures. This case illustrates the successful management using UV-activated intramedullary cement to augment fixation, specifically in a patient with risk factors and post-operative non-compliance that predispose to fixation failure.

Asunto(s)

RESUMEN

Meniscus allograft transplantation (MAT) is a technically challenging procedure. Bone plugs, slot techniques, and all-soft-tissue fixation techniques have been described in the past. Each technique comes with advantages and disadvantages. Native menisci have circumferential collagen fibers to help resist hoop stress during loading cycles. Although hoop stress resistance is a known function of the menisci, its recreation in MAT has only been targeted indirectly through anatomic root placement. The authors describe the use of a high-tensile suture tape (i.e. InternalBrace) to promote centralization by directly mitigating hoop stresses through recreation of peripheral meniscus tensioning in MAT.

RESUMEN

Assessing benthic invertebrate community responses to multiple stressors is necessary to improve the success of restoration and biomonitoring projects. Results of mesocosm and field experiments were integrated to predict how benthic macroinvertebrate communities would recover following the removal of acid mine drainage from the North Fork of Clear Creek (NFCC), a U.S. EPA Superfund site in Colorado, USA. We transferred reference and metal-contaminated sediment to an upstream reference site where colonization by benthic macroinvertebrates was measured over 30 days. Additionally, a mesocosm experiment was performed to test the hypothesis that patches of metal-contaminated substrate impede recolonization downstream. Abundance in all treatments increased over time during field experiments; however, colonization was slower in treatments with metal-contaminated fine sediment. Community assemblages in treatments with metal-contaminated fine substrate were significantly different from other treatments. Patterns in the mesocosm study were consistent with results of the field experiment and showed greater separation in community structure between streams with metal-contaminated sediments and reference-coarse habitats; however, biological traits also helped explain downstream colonization. This study suggests that after water quality improvements at NFCC, fine-sediment deposition will likely reduce recovery potential for some taxa; however highly mobile taxa that avoid patches of contaminated habitats can recover quickly.

Asunto(s)

RESUMEN

Identifying causal relationships between acid mine drainage (AMD) and ecological responses in the field is challenging. In addition to the direct toxicological effects of elevated metals and reduced pH, mining activities influence aquatic organisms indirectly through physical alterations of habitat. The primary goal of this research was to quantify the relative importance of physical (metal-oxide deposition) and chemical (elevated metal concentrations) stressors on benthic macroinvertebrate communities. Mesocosm experiments conducted with natural assemblages of benthic macroinvertebrates established concentration-response relationships between metals and community structure. Field experiments quantified effects of metal-oxide contaminated substrate and showed significant differences in sensitivity among taxa. To predict the recovery of dominant taxa in the field, we integrated our measures of metal tolerance and substrate tolerance with estimates of drift propensity obtained from the literature. Our estimates of recovery were consistent with patterns observed at downstream recovery sites in the NFCC, which were dominated by caddisflies and baetid mayflies. We conclude that mesocosm and small-scale field experiments, particularly those conducted with natural communities, provide an ecologically realistic complement to laboratory toxicity tests. These experiments also control for the confounding variables associated with field-based approaches, thereby supporting causal relationships between AMD stressors and responses.

Asunto(s)

RESUMEN

Daphnia magna were exposed to nano-sized CdSe/ZnS quantum dots (QDs) having three different surface coatings. QDs were investigated for their aqueous stability in the test media (hard reconstituted laboratory water) and for their uptake, elimination, and in-vivo dissolution. Positively charged QDs (QEI) and negatively charged QDs (QSH) were electrostatically stable, whereas neutrally charged QDs (QSA) showed aggregation and sedimentation over 48-h. After 24h of exposure to QDs (100µg/L as total Cd), the D. magna whole body Cd concentration significantly increased with no mortality for all QDs. Uptake patterns differed among the three coatings and Cd concentration reached 1460±50, 1014±99, and 584±81µg Cd/g dry wt for QEI, QSH, and QSA, respectively. Significant amounts of QEI and QSA (40% and 43%, respectively) remained in the D. magna after 24h of depuration, while 89% QSH were readily excreted within the initial 1h of the depuration stage. Soluble Cd was released from QDs during both the uptake and depuration. Release of Cd was higher in QEI and QSA than QSH, possibly resulting from the longer retention of QEI and QSA in the D. magna than QSH. These results imply that the surface charge of QDs plays a significant role in both the exposure to organisms and the in-vivo dissolution of nanoparticles.

Asunto(s)