A preliminary study into the impact of using three-dimensional models in forensic anthropology learning and teaching.

Forensic anthropology has traditionally relied on two-dimensional (2D) images, such as photographs and sketches, to perform analyses, and disseminate findings. However, as 3D imaging technology advances, it has become more widely implemented into forensic anthropology analysis and practice. Teaching and learning in forensic anthropology still often relies on 2D images, but increasingly three-dimensional (3D) models are available to be used by students training in anatomy and osteology. Additionally, 3D models have been found to be beneficial to comprehension in other contexts within forensic anthropology, such as in the courtroom. The use of these models in the teaching of forensic anthropology is not yet widely implemented and more importantly, the impact on learning is not yet understood. The use of 3D imaging and visualisation in other educational contexts has seen positive results, for example in medical training. To explore this further, a study was conducted using an online activity to compare the comprehension scores of students educated using 2D textbook style images or 3D models on Sketchfab. The results showed that the use of 3D images was not detrimental to comprehension. Students using the 3D models were more consistent in their performance and reported an increase in confidence regardless of prior experience. The results of this study are of particular importance when distance learning due to the COVID-19 pandemic which means that students cannot always learn in a laboratory environment.

Digital dissection of the pelvis and hindlimb of the red-legged running frog, Phlyctimantis maculatus, using Diffusible Iodine Contrast Enhanced computed microtomography (DICE µCT).

BACKGROUND: The current study applies both traditional and Diffusible Iodine Contrast Enhanced computed microtomography (DICE µCT) techniques to reveal the musculoskeletal anatomy of Phlyctimantis maculatus. DICE µCT has emerged as a powerful tool to visualise intricate musculoskeletal anatomy. By generating 3D digital models, anatomical analyses can be conducted non-destructively, preserving the in situ 3D topography of the system, therefore eliminating some of the drawbacks associated with traditional methods. We aim to describe the musculature of the spine, pelvis, and hindlimb, compare the musculoskeletal anatomy and pelvic morphology of P. maculatus with functionally diverse frogs, and produce 3D digital anatomy reference data. METHOD: An adult frog was stained using an aqueous Lugol's solution and scanned in a SkyScan1176 in vivo µCT scanner. Scan images were reconstructed, resampled, and digitally segmented to produce a 3D model. A further adult female frog was dissected traditionally for visualisation of tendinous insertions. RESULTS: Our work revealed three main findings: (1) P. maculatus has similar gross muscular anatomy to Rana catesbeiana (bullfrog) but is distinct from those species that exhibit ancestral traits (leopelmids) and those that are highly specialised (pipids), (2) P. maculatus's pelvic anatomy best fits the description of Emerson's walking/hopping pelvic morphotype IIA, and (3) a split in the semimembranosus and gracilis major muscles is consistent with the reported myology in other anuran species. DISCUSSION: While DICE µCT methods were instrumental in characterising the 3D anatomy, traditional dissection was still required to visualise important structures such as the knee aponeurosis, tendinous insertions, and fasciae. Nonetheless, the anatomical data presented here marks the first detailed digital description of an arboreal and terrestrial frog. Further, our digital model presents P. maculatus as a good frog model system and as such has formed a crucial platform for further functional analysis within the anuran pelvis and hindlimb.

The impact of pelvic lateral rotation on hindlimb kinematics and stride length in the red-legged running frog, Kassina maculata.

Some frog species, such as Kassina maculata (red-legged running frog), use an asynchronous walking/running gait as their primary locomotor mode. Prior comparative anatomy work has suggested that lateral rotation of the pelvis improves walking performance by increasing hindlimb stride length; however, this hypothesis has never been tested. Using non-invasive methods, experimental high-speed video data collected from eight animals were used to create two three-dimensional kinematic models. These models, each fixed to alternative local anatomical reference frames, were used to investigate the hypothesis that lateral rotation of the mobile ilio-sacral joint in the anuran pelvis plays a propulsive role in walking locomotion by increasing hindlimb stride length. All frogs used a walking gait (duty factor greater than 0.5) despite travelling over a range of speeds (0.04-0.23 m s-1). The hindlimb joint motions throughout a single stride were temporally synchronized with lateral rotation of the pelvis. The pelvis itself, on average, underwent an angular excursion of 12.71° (±4.39°) with respect to the body midline during lateral rotation. However, comparison between our two kinematic models demonstrated that lateral rotation of the pelvis only increases the cranio-caudal excursion of the hindlimb modestly. Thus, we propose that pelvic lateral rotation is not a stride length augmenting mechanism in K. maculata.

The dynamic role of the ilio-sacral joint in jumping frogs.

A striking feature among jumping frogs is a sharp pelvic bend about the ilio-sacral (IS) joint, unique to anurans. Although this sagittal plane hinge has been interpreted as crucial for the evolution of jumping, its mechanical contribution has not been quantified. Using a model based on Kassina maculata and animated with kinematics from prior experiments, we solved the ground contact dynamics in MuJoCo enabling inverse dynamics without force plate measurements. We altered the magnitude, speed and direction of IS extension (leaving remaining kinematics unaltered) to determine its role in jumping. Ground reaction forces (GRFs) matched recorded data. Prior work postulated that IS rotation facilitates jumping by aligning the torso with the GRF. However, our simulations revealed that static torso orientation has little effect on GRF due to the close proximity of the IS joint with the COM, failing to support the 'torso alignment' hypothesis. Rather than a postural role, IS rotation has a dynamic function whereby angular acceleration (i) influences GRF direction to modulate jump direction and (ii) increases joint loading, particularly at the ankle and knee, perhaps increasing tendon elastic energy storage early in jumps. Findings suggest that the pelvic hinge mechanism is not obligatory for jumping, but rather crucial for the fine tuning of jump trajectory, particularly in complex habitats.

Inverse dynamic modelling of jumping in the red-legged running frog, Kassina maculata.

Although the red-legged running frog, Kassina maculata, is secondarily a walker/runner, it retains the capacity for multiple locomotor modes, including jumping at a wide range of angles (nearly 70 deg). Using simultaneous hind limb kinematics and single-foot ground reaction forces, we performed inverse dynamics analyses to calculate moment arms and torques about the hind limb joints during jumping at different angles in K. maculata. We show that forward thrust is generated primarily at the hip and ankle, while body elevation is primarily driven by the ankle. Steeper jumps are achieved by increased thrust at the hip and ankle and greater downward rotation of the distal limb segments. Because of its proximity to the GRF vector, knee posture appears to be important in controlling torque directions about this joint and, potentially, torque magnitudes at more distal joints. Other factors correlated with higher jump angles include increased body angle in the preparatory phase, faster joint openings and increased joint excursion, higher ventrally directed force, and greater acceleration and velocity. Finally, we demonstrate that jumping performance in K. maculata does not appear to be compromised by presumed adaptation to walking/running. Our results provide new insights into how frogs engage in a wide range of locomotor behaviours and the multi-functionality of anuran limbs.