To determine whether a fluoroscopic technique can be used to improve the accuracy of the determination of the femoral origin of the lateral collateral ligament (LCL).
A 1-cm incision was made over ...the lateral epicondyle in 13 fresh-frozen cadaveric knee specimens, and the LCL origin was determined first by palpation and then with a previously described fluoroscopic method. Both points for the LCL origin were marked with 2-mm Kirschner wires. The distances between the center of the anatomic LCL origin and the LCL origin points determined by palpation and fluoroscopic imaging were calculated. An independent t-test was used to compare the distances between the anatomic LCL origin center and the determined LCL origin points.
The LCL origin points determined by fluoroscopic imaging were significantly (P = .005) closer to the anatomic center of the LCL origin point than the ones determined by palpation (3.2 mm ± 1.6 mm vs 5.0 mm ± 1.6 mm, respectively). A total of 92.7% fluoroscopically determined LCL origin points were within a 5 mm radius surrounding the anatomic LCL origin point. In contrast, only 53.8% LCL origin points determined by palpation were within a 5 mm radius surrounding the anatomic LCL origin point.
The use of palpation to identify the LCL origin may not be an accurate method for performing an isometric and anatomic LCL reconstruction. The use of fluoroscopic imaging appears to be a feasible method for identifying the LCL origin in clinical practice and may increase the accuracy of LCL origin identification. Fluoroscopic guidance improves accuracy in determining the anatomic LCL origin, which may help avoiding tunnel malplacement during LCL reconstruction.
The use of a previously described radiographic method for identifying the LCL origin may be used to achieve a more anatomic LCL reconstruction.
Purpose/hypothesis
The purpose of this observational study was to determine which factors, including sex, are associated with increased rotatory knee laxity in collegiate athletes with no history of ...knee injuries. It was hypothesized that increased rotatory knee laxity, measured by a quantitative pivot shift test, would correlate with female sex, increased anterior translation during the Lachman test, generalized ligamentous laxity, and knee hyperextension.
Methods
Ninety-eight collegiate athletes with a median age of 20 (range 18–25) years with no history of knee injuries were tested. IKDC and Marx activity scores were obtained and subjects underwent measurement of anterior translation during the Lachman test with a Rolimeter and measurement of knee hyperextension with a goniometer for both knees. A standardized pivot shift test was performed in both knees and quantified using image analysis technology. Generalized ligamentous laxity was assessed using the modified Beighton score.
Results
The average anterior translation of the lateral compartment during the pivot shift test was 1.6 mm (range 0.1–7.1) with a mean side-to-side difference of 0.6 mm (range 0–2.7). The average anterior translation during the Lachman test was 9.0 (range 2–15). The anterior translation of the lateral compartment during the pivot shift test was significantly higher in females (median, 1.6; range 0.3–4.9) than in males (1.1, 0.1–7.1 mm) (
p
< 0.05). Anterior translation of the lateral compartment during the pivot shift test was significantly correlated with anterior translation during the Lachman test (
r
= 0.34;
p
< 0.05). There was no significant correlation between anterior translation of the lateral compartment during the pivot shift test and knee hyperextension or modified Beighton score (n.s).
Conclusion
The data from this study show that female sex is associated with increased rotatory knee laxity measured during the pivot shift test and anterior translation during the Lachman test in collegiate athletes. In the future, these data may be helpful in diagnosing and managing ACL injuries in athletes and could be used in the clinic as a baseline by which to compare and identify patients who might exhibit increased rotatory laxity.
Level of evidence
Diagnostic level II.
The value of reputation Pfeiffer, Thomas; Tran, Lily; Krumme, Coco ...
Journal of the Royal Society interface,
11/2012, Volume:
9, Issue:
76
Journal Article
Peer reviewed
Open access
Reputation plays a central role in human societies. Empirical and theoretical work indicates that a good reputation is valuable in that it increases one's expected payoff in the future. Here, we ...explore a game that couples a repeated Prisoner's Dilemma (PD), in which participants can earn and can benefit from a good reputation, with a market in which reputation can be bought and sold. This game allows us to investigate how the trading of reputation affects cooperation in the PD, and how participants assess the value of having a good reputation. We find that depending on how the game is set up, trading can have a positive or a negative effect on the overall frequency of cooperation. Moreover, we show that the more valuable a good reputation is in the PD, the higher the price at which it is traded in the market. Our findings have important implications for the use of reputation systems in practice.
Although limited by a single resource, microbial populations that grow for long periods in continuous culture (chemostat) frequently evolve stable polymorphisms. These polymorphisms may be maintained ...by cross‐feeding, where one strain partially degrades the primary energy resource and excretes an intermediate that is used as an energy resource by a second strain. It is unclear what selective advantage cross‐feeding strains have over a single competitor that completely degrades the primary resource. Here we show that cross‐feeding may evolve in microbial populations as a consequence of the following optimization principles: the rate of ATP production is maximized, the concentration of enzymes of the pathway is minimized, and the concentration of intermediates of the pathway is minimized.
Purpose
A deep lateral femoral notch (LFN) on lateral radiographs is indicative of ACL injury. Prior studies have suggested that a deep LFN may also be a sign of persistent rotatory instability and a ...concomitant lateral meniscus tear. Therefore, the purpose of this study was to evaluate the relationship between LFN depth and both quantitative measures of rotatory knee instability and the incidence of lateral meniscus tears. It was hypothesized that greater LFN depth would be correlated with increased rotatory instability, quantified by lateral compartment translation and tibial acceleration during a quantitative pivot shift test, and incidence of lateral meniscus tears.
Methods
ACL-injured patients enrolled in a prospective ACL registry from 2014 to 2016 were analyzed. To limit confounders, patients were only included if they had primary ACL tears, no concurrent ligamentous or bony injuries requiring operative treatment, and no previous knee injuries or surgeries to either knee. Eighty-four patients were included in the final analysis. A standardized quantitative pivot shift test was performed pre-operatively under anesthesia in both knees, and rotatory instability, specifically lateral compartment translation and tibial acceleration, was quantified using tablet image analysis software and accelerometer sensors. Standard lateral radiographs and sagittal magnetic resonance images (MRI) of the injured knee were evaluated for LFN depth.
Results
There were no significant correlations between LFN depth on either imaging modality and ipsilateral lateral compartment translation or tibial acceleration during a quantitative pivot shift test or side-to-side differences in these measurements. Patients with lateral meniscus tears were found to have significantly greater LFN depths than those without on conventional radiograph and MRI (1.0 vs. 0.6 mm,
p
< 0.05; 1.2 vs. 0.8 mm,
p
< 0.05, respectively).
Conclusion
There was no correlation between lateral femoral notch depth on conventional radiographs or MRI and quantitative measures of rotatory instability. Concomitant lateral meniscus injury was associated with significantly greater LFN depth. Based on these findings, LFN depth should not be used as an indicator of excessive rotatory instability, but may be an indicator of lateral meniscus injury in ACL-injured patients.
Level of evidence
Prognostic level IV.
A high level of robustness against gene deletion is observed in many organisms. However, it is still not clear which biochemical features underline this robustness and how these are acquired during ...evolution. One hypothesis, specific to metabolic networks, is that robustness emerges as a byproduct of selection for biomass production in different environments. To test this hypothesis we performed evolutionary simulations of metabolic networks under stable and fluctuating environments. We find that networks evolved under the latter scenario can better tolerate single gene deletion in specific environments. Such robustness is underlined by an increased number of independent fluxes and multifunctional enzymes in the evolved networks. Observed robustness in networks evolved under fluctuating environments was "apparent," in the sense that it decreased significantly as we tested effects of gene deletions under all environments experienced during evolution. Furthermore, when we continued evolution of these networks under a stable environment, we found that any robustness they had acquired was completely lost. These findings provide evidence that evolution under fluctuating environments can account for the observed robustness in metabolic networks. Further, they suggest that organisms living under stable environments should display lower robustness in their metabolic networks, and that robustness should decrease upon switching to more stable environments.
Abstract
Progress in neuroscience research hinges on technical advances in visualizing living brain tissue with high fidelity and facility. Current neuroanatomical imaging approaches either require ...tissue fixation (electron microscopy), do not have cellular resolution (magnetic resonance imaging) or only give a fragmented view (fluorescence microscopy). Here, we show how regular light microscopy together with fluorescence labeling of the interstitial fluid in the extracellular space provide comprehensive optical access in real-time to the anatomical complexity and dynamics of living brain tissue at submicron scale. Using several common fluorescence microscopy modalities (confocal, light-sheet and 2-photon microscopy) in mouse organotypic and acute brain slices and the intact mouse brain in vivo, we demonstrate the value of this straightforward ‘shadow imaging’ approach by revealing neurons, microglia, tumor cells and blood capillaries together with their complete anatomical tissue contexts. In addition, we provide quantifications of perivascular spaces and the volume fraction of the extracellular space of brain tissue in vivo.
An understanding of the behavior of SARS-CoV-2 in pediatric hematology-oncology patients is essential to the optimal management of these patients during the COVID-19 pandemic. This study describes ...the characteristics and outcomes of COVID-19 disease in children with cancer or hematologic disorders treated at a large children's hospital. A retrospective cohort study was conducted at Texas Children's Cancer and Hematology Center from January 1, 2020 to September 30, 2020. All patients with a primary hematology-oncology diagnosis and SARS-CoV-2 positivity by reverse transcription polymerase chain reaction were identified. Clinical and laboratory data were obtained from the medical record. Descriptive analyses were performed to evaluate COVID-19-related outcomes and risk factors for severe disease in this population. We identified 109 patients with COVID-19 disease, including 52 hematology, 51 oncology, and 6 HSCT patients; median age was 10.3 years (IQR 4.4-15.9), and 58.7% were male. Seventy-four percent of the patients were managed in the outpatient setting. Patients with sickle cell disease were more likely to require hospitalization. ICU care was needed in 8% (n = 9) of the entire cohort, and mechanical ventilation was required in 6.4% (6 oncology patients, 1 hematology patient). COVID-19 contributed to the deaths of two cancer patients. No deaths occurred in hematology or HSCT patients. In conclusion, the risk of severe COVID-19 complications is slightly higher in pediatric hematology-oncology patients than in the general pediatric population but lower than initially feared. For most asymptomatic patients, primary disease management may continue as planned, but treatment decisions must be individualized.
► We show how asymmetric information alters a firm’s supplier switching process. ► Under symmetric information, delayed contracting is unambiguously beneficial. ► Under asymmetric information, ...hurried contracting can be beneficial. ► Under delayed contracting, switching inertia occurs. ► Under hurried contracting, switching acceleration and abandonment occurs.
Applying a real option approach, this paper examines how asymmetric information alters key variables of a firm’s supplier switching process, such as the timing of contracting (hurried versus delayed contracting), transfer payments, set-up, switching, and abandonment decisions. In a symmetric information setting, delayed contracting is unambiguously beneficial. Abandoning the once established relation with the entrant supplier is never an issue. In contrast, under asymmetric information hurried contracting with potentially abandoning the relation can be beneficial. Consistent with adverse selection models, we find that under delayed contracting, in equilibrium, the firm switches less frequently to the entrant supplier (switching inertia). Surprisingly, we also find that under hurried contracting the firm switches more frequently to the entrant supplier (switching acceleration) and may abandon the relation. Finally, we study how these key variables of the supplier switching process change when also the incumbent supplier has private information (two-sided asymmetric information case).
This paper studies how simple two-part wholesale-price, cost-plus, and revenue-sharing contracts enable the coordination of trade and bilateral non-cooperative effort decisions under uncertainty for ...a decentralized supply chain consisting of a supplier and a retailer. For all these contracts, the use of an up-front fixed payment is beneficial because it allows separating the supply chain's coordination problem from the allocation of the total supply chain profit across the two parties. In particular, we find that slotting allowances, i.e. fixed payments from the supplier to the retailer, can be optimal in conjunction with a cost-plus and revenue-sharing contract, but not in conjunction with a wholesale-price contract. A performance comparison shows that the wholesale-price contract dominates the more advanced cost-plus and revenue-sharing contract if cost uncertainty is low (and vice versa). Finally, we provide additional insights regarding the optimal design of the contract parameters and the performance of the individual contracts for linear demand functions.
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