Background Since lateral tibial slope (LTS) affects the amount of anterior tibial translation and anterior cruciate ligament (ACL) strain during a dynamic maneuver, accurate measurements of lateral tibial slope may be beneficial in screening individuals at a higher risk for ACL injury. Methods for measuring LTS on magnetic resonance imaging scans of the proximal tibia include the midpoint and circle methods. There are no current studies that have validated different LTS measurements methods using a proximal tibia magnetic resonance imaging scan. Hypothesis We tested the null hypotheses that (1) LTS measurements were independent of the length of tibia imaged using the midpoint method, and (2) LTS measurements calculated from different methods (‘midpoint’, ‘circle’, and ‘full tibia’) would not differ significantly. Study Design Descriptive Laboratory Study Methods Blinded observers measured LTS from 3-Tesla 3D magnetic resonance images from 40 size-matched donors according to one circle method and three midpoint methods. Outcomes were then compared to the full tibial anatomical axis (line connecting the center of two circles fit within the proximal and distal tibia) in 11 donors. Bonferroni-correct paired t-tests (p < 0.005 significant) were used to compare the five methods. Results The circle and full tibia methods had the lowest inter- and intra-observer variability, while the midpoint method with 10 cm tibia was the most variable. The midpoint method with 10cm and 15 cm proximal tibia closely resembled LTS measurements with the full tibia anatomic axis. The circle method, while repeatable, provided smaller numerical LTS measurements than the full tibia and midpoint methods. Conclusions While LTS measurements using the midpoint method can resemble measurements made using the full tibia, the reliability of the midpoint method depends on the length of proximal tibia used. The circle method may be the preferred method for future studies since it was the most repeatable method and is independent of proximal tibia length. Clinical Relevance LTS measurements vary depending on the method utilized.

No abstract

Fitness costs are frequently invoked to explain the presence of genetic variation underlying plant defense across many types of damaging agents. Despite the expectation that costs of resistance are prevalent, however, they have been difficult to detect in nature. To examine the potential that resistance confers a fitness cost, we examined the survival and fitness of genetic lines of the common morning glory, Ipomoea purpurea, that diverged in the level of resistance to the herbicide glyphosate. We planted a large field experiment and assessed survival following herbicide application as well as fitness of the divergent selection lines in the absence of the herbicide. We found that genetic lines selected for increased resistance exhibited lower death compared to control and susceptible lines in the presence of the herbicide, but no evidence that resistant lines produced fewer seeds in the absence of herbicide. However, susceptible lines produced more viable seeds than resistant or control lines, providing some evidence of a fitness cost in terms of seed germination, and thus potential empirical support for the expectation of trait trade‐offs as a consequence of adaptation to novel environments.

No abstract

This article contains supporting information online at: xxx.