The wide range of dietary niches filled by modern mammals is reflected in morphological diversity of the feeding apparatus. Despite volumes of data on the biomechanics of feeding, the extent to which the shape of mammal skulls reflects stresses generated by feeding is still unknown. In addition to the feeding apparatus, the skull accommodates the structural needs of the sensory systems and brain. We turned to bats as a model system for separating optimization for masticatory loads from optimization for other functions. Because the energetic cost of flight increases with body mass, it is reasonable to suggest that bats have experienced selective pressure over evolutionary time to minimize mass. Therefore, the skulls of bats are likely to be optimized to meet functional demands. We investigate the hypothesis that there is a biomechanical link between biting style and craniofacial morphology by combining biting behavior and bite force data gathered in the field with finite-element (FE) analysis. Our FE experiments compared patterns of stress in the craniofacial skeletons within and between two species of bats (Artibeus jamaicensis and Cynopterus brachyotis) under routine and atypical loading conditions. For both species, routine loading produced low stresses in most of the skull. However, the skull of Artibeus was most resistant to loads applied via its typical biting style, suggesting a mechanical link between routine loading and skull form. The same was not true of Cynopterus, where factors other than feeding appear to have had a more significant impact on craniofacial morphology. Key words: biting behavior; bone stress; adaptation; finite-element analysis; Chiroptera Mammal evolution is largely a story of the expansion of dietary niches from an insect-eating ancestor to include foods ranging from meat and bone to plankton. This diversity is clearly reflected in the morphology of the craniofacial skeleton. The association between skull structure and diet across distantly related mammals suggests that skull shape underwent selection over evolutionary time as new dietary niches were explored. Many excellent laboratory-based studies of feeding have provided a wealth of detailed information about the biomechanical behavior of bones and muscles under controlled experimental conditions. Building on this knowledge, morphologists are beginning to venture into the field to investigate how natural behaviors interact with morphology to define how animals function within their native environments. By

The purpose of this study was to compare 6 different graft fixation techniques to determine the preparation speed, fixation security, biomechanical strength, and resultant tissue trauma. Methods: Six different techniques (10 samples each): #2 OrthoCord Krackow stitch, #2 FiberWire Krackow stitch, SpeedTrap, WhipKnot, Loop-in-loop stitch were created in the distal 3 cm of 9 cm bovine flexor tendons. The proximal 3 cm tendon segment was clamped in a testing machine and the distal suture ends secured by pneumatic grips. 3 preload cycles (10N-100N) and 50N static load was followed by 500 cycles (50N-200N) and then loaded to failure. Graft preparation times, 100 and 500 cycle displacement, maximum failure load, stiffness, and failure mode were recorded. Results: Representative graft preparation times were: OrthoCord Krackow (247s), FiberWire Krackow (401s), FiberLoop (177s), SpeedTrap (42s), WhipKnot (39s), Loopin-loop (45s). No WhipKnots survived cyclic loading. 100 cycle displacements were: OrthoCord Krackow (11.5 AE 3.9 mm), FiberWire Krackow (8.9 AE 1.2 mm), FiberLoop (14.2 AE 6.1 mm), SpeedTrap (8.8 AE 2.5 mm), Loop-in-loop (10.4 AE 2.9 mm). FiberLoop displaced significantly more than all others (P ¼ .016). Maximum failure loads were: OrthoCord Krackow (364 AE 24N), FiberWire Krackow (375 AE 45N), FiberLoop (413 AE 95N), SpeedTrap (437 AE 65N), WhipKnot (153 AE 42N), Loop-in-loop (329 AE 112N). The most common failure mode was suture breaking. FiberWire containing constructs (Krackow and FiberLoop) shredded or cut through ("cheese wiring") prior to failure in a majority. Conclusions: SpeedTrap, WhipKnot and Loop-in-loop were quickest to create (under 1 minute). The Krackow, SpeedTrap, WhipKnot, and Loop-in-Loop did not damage the tendon during cyclic loading. SpeedTrap and Krackow had the least displacement. FiberLoop displaced more than all other groups (P ¼ .016). No WhipKnot completed cyclic loading. The SpeedTrap (437N) and FiberLoop (413N) had the highest ultimate strength. Clinical Relevance: While the SpeedTrap and FiberLoop are the strongest techniques, the FiberLoop shreds the tendon, displaced the most, and took longer to create. Based on these results, the SpeedTrap demonstrates the best overall performance.

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