Pictures

Long-Axis Rotation

A missing degree of freedom in avian bipedal locomotion

Figure 1. Experimental setup reconstructed as a Maya scene. (A) Top view of the maneuvering chamber representing the two X-ray systems as a pair of virtual X-ray cameras with overlapping yellow and blue beams. Two calibrated standard cameras (red and green fields of view) provide external imaging of the whole bird and feet. (B) Perspective view of the scene showing the reconstructed skeletal model in place between the four image planes textured with frames of video. (C–F) When viewed through each virtual camera, bone models are registered to their X-ray shadows as well as to the standard video images.

Figure 2. Marker-based XROMM using carbide points. (A–C) Three steps in the fabrication of a conical marker from a stock rod. (D) The thinned blade is strong enough to allow manual insertion, but weak enough for the tip to snap off when bent. (E) Planar X-ray of points implanted into the proximal and distal femur. (F) Implant sites shown by polygonal marker models (red) within their respective bone models.

Figure 3. Individual and combined consequences of LAR. (A) Cranial view of a neutral pose. (B) Internal hip LAR (orange) moves the right foot laterally while external hip LAR (purple) moves the foot medially. (C) External knee LAR (orange) moves the right foot laterally and toes out while internal knee LAR (purple) moves the foot medially and toes in. (D) Internal hip LAR and external knee LAR (orange) are additive, as are external hip LAR and internal knee LAR (purple). (E) Combining internal (orange) and external (purple) LARs generates a range of digital axis angles at a similar toe position.

Figure 4. Yaw during steady locomotion. (A–C) Light video frames from a treadmill sequence while the individual was yawed 7.1 deg to the left, 1.8 deg to the right and 14.1 deg to the right, respectively. (D) Histogram of pelvic yaw values for 10 steady treadmill sequences. Superimposed renderings show the orientation of the pelvis in dorsal view at the maximum yaw to the left and right, with the pelvic long axis (black) and the direction of treadmill travel (red). Arrows show ranges of yaw values for 12 short sequences from the same birds moving freely down a trackway. Arrowheads indicate the animal’s direction of movement; those pointing to the right were facing in the same direction as the treadmill trials.

Figure 5. Sidestep and yawed treadmill trials in overhead view. (A) Sidestep to the left. (B) Forward progression at a large induced yaw. (C) Forward progression at a large natural yaw. (D) Forward progression at low yaw. Arrows show the approximate direction of travel. Red lines show paths of the distal tarsometatarsi during stance relative to the pelvis for right and left steps.

Birth of a Dinosaur Footprint

Subsurface 3D motion reconstruction and discrete element simulation reveal track ontogeny

Figure 1. XROMM analysis of guineafowl limb movement through a compliant substrate (poppy seeds).

Figure 2. Track ontogeny. Simulated track using the motions of guineafowl traversing poppy seeds as part of a discrete element simulation.

Fish Suction Power

Swimming muscles power suction feeding in largemouth bass

Fig. 1: Diagram of largemouth bass cranial skeleton and muscles powering suction feeding, including the cranial (levator arcus palatini, dilator operculi, levator operculi, and sternohyoideus) and body (epaxialis, hypaxialis) muscles. Modified from Camp et al., 2015.

Fig. 2: Suction expansion power (black lines) from the strikes of one bass, compared with the maximum (grey dashed line) and velocity-corrected (red line) power capacities of the cranial muscles from the same individual. For all strikes, peak expansion power was far greater than the maximum power the cranial muscles could produce. Modified from Camp et al., 2015.

Fish Bite Force

Gape-specific bite force and prey-size specific predator performance in
the snail-eating black carp

$Fig. 1: Oral jaws are not used for snail crushing in black carp; instead, the pharyngeal jaws function in fracturing snails. These jaws are modified fifth gill arches, which no longer have respiratory function; arches 1-4 are still normal gills. The pharyngeal jaw lies immediately anterior and medial to the pectoral girdle and is supported by a sling of muscles with no jaw joint. The main focus of this study was the levator muscle, which elevates the jaws into occlusion with the base of the skull.$

Fig. 2: We manufactured a series of different prey items by taking four different sizes of ceramic tubes (sizes, in millimeters, are indicated on the figure). Each size of prey item had a characteristic strength, as determined by a materials testing machine. We coated each prey item with polyurethane to increase its strength, and successive coats yielded at successively higher strengths. Using these manufactured

Fig. 3: Each of our three individuals could fit all four sizes of prey between the jaws, and attempted to break them when they were filled with food. Each individual was given 5-10 attempts to crush each combination of sizes/strengths. Black-filled circles indicate 100% success in crushing the tubes of that size/strength, and success rates decline as the colors get lighter. White indicates zero success on a given food item. Note how performance varies not only with force (along the Y axis), but also with prey size (along the X axis). If an animal was unable to crush all of the food items of a given size and strength, we did not test stronger food items of that same size.

Fig. 4: After the performance tests, we measured muscle force at a variety of muscle lengths. Using this setup, we electrically stimulated the muscle, recorded jaw and skull position using XROMM, and measured force using a force transducer. Since we had some feeding trials also within view of the X-ray machines, we were able to reconstruct what muscle length was used in vivo, and how that corresponded to muscle lengths along the force-length curve in situ.

Fig. 5: By combining our in vivo and in situ data, we were able to show that bite performance in vivo is constrained by the force-length curve of the jaw adductor muscle. This graph is standardized to maximal muscle force for a given individual (Y axis) and the relative muscle length (X axis), where 1.0 is the muscle length at peak force. The grey symbols (circles, squares, and diamonds) represent in situ muscle lengths and forces from the apparatus in Fig. 4.The triangles represent the muscle length and strength of the weakest uncrushable food items of a given size (downward-pointing triangles) and the strongest crushable food items of a given size (upward-pointing triangles). Muscle lengths were measured in vivo while the animals crushed ceramic tubes, and forces were taken from Fig. 2.

Jump Cut

Biomechanics of male and female ACL-intact and ACL-reconstructed
athletes during a jump-cut maneuver

Figure 1: A, illustration depicting the experimental set-up used to capture both biplanar videoradiography and OMC data during a jump-cut maneuver. B, example frame from the Autoscoper markerless tracking software. Each view represents one frame from each of the two videoradiographs generated from the two image intensifiers (Figure 1A). The knee shown in this image is from one of the ACL-reconstructed subjects. Both interference screws are visible in the femur and tibia.

Figure 2: A, ACL-intact vertical GRF. B, ACL-reconstructed vertical GRF. C, ACL-intact AN/PO translational excursion. D, ACL-reconstructed AN/PO translational excursion.

Figure 3: Left y-axis, minimum knee flexion angle for ACL-intact and ACL-reconstructed male and female subjects. Minimum flexion occurred at or immediately following ground contact. Right y-axis, knee flexion angle excursion for ACL-intact and ACL-reconstructed male and female subjects. Knee flexion angle excursion was defined as the change in knee flexion angle from minimum flexion to maximum flexion.

Soft Tissue Artifact

Comparing knee kinematics between XROMM and traditional optical motion capture
during a jump-cut maneuver

Panels A and B represent a single frame of the biplanar videoradiography data for source 1 and 2, respectively. Panels C and D represent the same frame of the biplanar videoradiography data (blue) after image processing. The 3-D models of the tibia and femur driven by optical motion capture (tan) and biplanar motion capture (blue) are shown in panels E and F. All four independently tracked anatomical coordinate systems are also shown. The short and lighter coordinate systems are being driven by OMC and the long and darker coordinate systems are being driven by biplanar videoradiography. The external markers for the thigh and shank are also shown in tan. Panel E represents the initial frame, where OMC and biplanar videoradiography are perfectly aligned. Panel F represents a frame where soft tissue artifact is affecting the OMC driven bones and coordinate systems.

Example OMC (dotted red) and biplanar videoradiography (solid green) knee flexion angle and ground reaction force (solid blue) data versus time. The dotted vertical lines represent the contact event. The period before contact is period A and the period after contact is period B. Period A began and period B ended when the femur and tibia entered and exited the FOV of the biplanar videoradiography system. Thus, the arrows shown above the ME/LA translation graph denote the time point where the knee entered and exited the field of view of the biplanar videoradiography system, respectively.

Fish Feeding

Biomechanics of jaw protrusion in common carp

Common carp have highly kinetic skulls which allow them to protrude their upper jaws. This may aid in suction feeding performance and food-sorting within the oral cavity.

In addition to typical fish skull upper jaw bones such as the maxilla and premaxilla, cypriniform fishes develop a novel bone, the kinethmoid. This mobile bone is embedded between the maxillae along the midline of the fish.

Even in a stained an cleared preparation, which is specifically designed to demonstrate bone shape, a meshwork of ligaments and other bones makes the kinethmoid difficult to see in-situ. Can you find it here?

This medial view of the oral jaw bones in carp demonstrates our marker placement for this study. Neurocranium markers have not been included.

Once we have an xromm, we can use anatomically-relevant axis systems to describe the 6 degrees of freedom of each bone relative to other bones. Here, two of the axes of the maxilla are demonstrated for an open-mouthed protrusion. Rotation about the magenta axis shows parasagittal rotation of the maxilla; rotation about the blue axis shows long-axis rotation of the maxilla; translation along the blue axis shows ventral translation of the maxilla.

In this frame, the same axis system as Photo 5 is shown, only now the animal is performing a closed-mouth protrusion.

Movement patterns of protrusion, ventral translation of the maxilla, lower jaw rotation, and parasagittal rotation of the maxilla are very highly correlated with the kinethmoid's movement pattern (y-axis values close to 1), whereas other maxillary degrees of freedom are not correlated during open mouth protrusion.

During closed mouth protrusion, ventral translation is the only maxillary movement pattern that is correlated significantly with kinethmoid rotation.

Iguana Breathing

Rib kinematics & intercostal muscle strain during breathing in Iguana iguana

Green iguana, Iguana iguana.

Green iguanas have four cervical (Cv) ribs, four sternal (St) ribs that articulate with the sternum via long costal cartilages, and three xiphisternal ribs. XROMM analysis shows that the dorsal osseous ribs (gold) and ventral costal cartilages (green) move as separate rigid elements, connected by thin cartilaginous regions that act as joints.

Still image from biplanar X-ray video of lung ventilation in a green iguana. Snout-vent length of this animal is approximately 50 cm.

To measure intercostal muscle fascicle strain, a 3D digitizer is used to map the fascicles from an iguana cadaver onto the 3D models of the ribs. Then the XROMM animation is used to measure intercostal fascicle strain. External intercostal (red) and internal intercostal (blue) fascicles are shown here.

Rib rotation gradient with cool colors (blue) indicating less motion during breathing and hot colors (red) more motion. XROMM animations reveal little movement of Cv1 and Cv2, increasing amounts of rotation in Cv3-St1, the greatest rotation in St2, and gradually decreasing rotation in St3-4 and more caudal ribs. In the intercostal space between the osseous portions of St1 and St2, the EI lengthen during exhalation and shorten during inhalation, whereas between St3 and St4, the EI shorten during exhalation and lengthen during inhalation.

Pig Feeding

Marker-based XROMM analysis of mastication in minipigs

Figure 1. Sinclair strain miniature pig. Three individuals (3-4 months old) were used in this study.

Figure 2. Fluoroscope image of pig snout with radiopaque tantalum markers. Bones appear dark and air white in this x-ray positive image. The tantalum beads are the small black spots.

Figure 3. Lateral grinding results primarily from rotation of the mandible about a dorsoventrally oriented axis.

Figure 4. Rostrocaudal translations result from jaw protrution and retrusion.

Duck Feeding

Kinematics of the quadrate bone during feeding in mallard ducks

A male and female Mallard duck. All of the ducks in this study were female.

Mallard duck feeding on duck chow mixed with water.

The quadrate bone plays a central role in feeding mechanics, particularly in the elevation of the upper bill. It has been hypothesized that the movement of the quadrate is transferred primarily through the pterygoid and palatine bones to the upper bill (Bock 1964, Gussekloo et al. 2001, Zweers 1974, van Gennip and Berkhoudt, 1992).

The quadrate articulates with four bones: pterygoid, braincase, jugal and mandible.

Hardware

Mobile C-arm fluoroscopes and biplanar x-ray rooms

Diagram of mobile C-arm fluoroscopes, retrofitted for high-speed imaging. New 30-cm image intensifiers have been installed and the original cameras have been replaced with high-speed video cameras. A standard international (size 5) soccer ball is included for scale. Radiological Imaging Services, Hamburg PA (800-748-2040) has experience refurbishing and retrofitting C-arms for high-speed imaging.

Photograph of mobile C-arm fluoroscopes, retrofitted for high-speed imaging. New 30-cm image intensifiers have been installed and the original cameras have been replaced with high-speed video cameras. Radiological Imaging Services, Hamburg PA (800-748-2040) has experience refurbishing and retrofitting C-arms for high-speed imaging.

The W.M. Keck Foundation XROMM Facility at Brown University. Two x-ray tubes are suspended from the ceiling by tube cranes and two image intensifiers are mounted on mobile gantries. Independent movement of the four components gives the system a lot of flexibility in physical configuration. Here the system is configured to collect two oblique, ventro-dorsal views.

The W.M. Keck Foundation XROMM Facility at Brown University. Independent movement of the four components gives the system a lot of flexibility in physical configuration. Here the system is configured to collect two oblique, medio-lateral views.