In a development that could reshape how scientists study the mechanics of human movement, a team of biomedical engineers and computer scientists has unveiled an open-source software tool capable of tracking the tiny, intricate bones of the wrist as they glide and rotate during motion. The new tool, called Hierarchical 3D Registration, or 3DH, is a module within the SlicerAutoscoperM extension of the widely used 3DSlicer computing environment. Described in a study published in BioMedical Engineering OnLine, the software was validated against previously established methods using both sequential three-dimensional computed tomography, or 3DCT, scans of living participants performing thumb tasks and dynamic four-dimensional CT, or 4DCT, images of cadaveric wrists moving through flexion and extension. The results demonstrate that the open-source approach can match the accuracy of independent, previously published methodologies while offering researchers everywhere a free and reproducible path to quantifying skeletal kinematics.

The wrist has long been one of the most challenging joints for biomechanists to study. It contains eight small carpal bones, including the scaphoid and lunate, along with the radius of the forearm and the metacarpal bones of the hand, all articulating in a tightly packed arrangement that allows the remarkable range of motion humans rely on every day. Understanding how these bones move relative to one another, a field of study known as arthrokinematics, is essential for unraveling the causes of wrist instability, osteoarthritis, ligament injuries and the long-term outcomes of surgical repairs. Yet measuring those movements in living, moving joints has historically required either invasive techniques, labor-intensive manual analysis or proprietary software that few laboratories can access or verify.

Quantitative tracking of skeletal structures in vivo, with both efficiency and high temporal resolution, matters to a wide range of questions in biomechanical research, and the authors of the new study argue that the field has been held back by a shortage of accessible, semi-automated registration tools. Image registration, the computational process of aligning one three-dimensional image volume to another, lies at the heart of motion tracking from CT data. When a bone moves between two scans, its position and orientation change, and a registration algorithm must find the transformation that best overlays the bone’s image from one time point onto the next. Done well, this yields precise measurements of rotation and translation. Done poorly or inconsistently, it introduces errors that can swamp the small movements of carpal bones, which may shift by only a few millimeters and a few degrees during normal function.

The new 3DH module addresses this problem with a hierarchical strategy for registering bones across sequences of image volumes. The researchers presented and evaluated the software using two distinct classes of data drawn from previous studies. The first consisted of sequential 3DCT datasets of human participants performing various thumb tasks, in which the radius, the first metacarpal and the trapezium were the target bones. The second consisted of dynamic 4DCT datasets capturing simulated flexion-extension motion in cadaveric wrists, providing time-resolved, three-dimensional image volumes of the scaphoid and lunate in motion. By testing the tool on both static sequential scans and true dynamic imaging, the team was able to demonstrate that 3DH is not limited to a single imaging paradigm but can serve as a unified tracking solution across modalities.

To determine whether the new open-source tool could be trusted, the investigators compared the arthrokinematics computed with 3DH against values that had been previously calculated using independent approaches for the same 3DCT and 4DCT datasets. The statistical framework for this comparison was the Bland-Altman analysis, a standard method for assessing agreement between two measurement techniques. Rather than simply correlating the two sets of results, Bland-Altman analysis quantifies the mean bias, the systematic difference between methods, and the 95 percent limits of agreement, the range within which most individual differences between the methods are expected to fall. This approach is particularly well suited to method-comparison studies because it reveals whether a new technique introduces systematic error and how widely individual measurements might deviate from those of the established gold standard.

The performance figures reported in the study are striking. For the 3DCT data, in which the radius, first metacarpal and trapezium were tracked, the mean bias for the helical angle, a single-axis description of three-dimensional rotation, was just minus 0.06 degrees, with 95 percent limits of agreement ranging between minus 1.87 degrees and 1.74 degrees. Translation measurements fared nearly as well: the mean bias was 0.12 millimeters, with limits of agreement spanning from minus 2.23 millimeters to 2.00 millimeters. In practical terms, the open-source tool reproduced the rotational and translational measurements of the earlier methods to within roughly two degrees and two millimeters at the extremes, differences small enough to preserve the biological signal in most wrist kinematics experiments.

The dynamic 4DCT results told a similar story for the carpal bones. Tracking the scaphoid and lunate through simulated flexion-extension, 3DH produced mean biases of the Euler angle rotations, which decompose three-dimensional rotation into three orthogonal components, of less than 0.77 degrees about any direction. The widest 95 percent limits of agreement ranged between minus 7.11 degrees and 8.65 degrees. For translations, mean biases were less than 0.5 millimeters in any direction, with the widest limits of agreement ranging between minus 2.36 millimeters and 1.43 millimeters. The wider limits of agreement for rotations in the dynamic data likely reflect the added challenges of time-resolved imaging, including motion blur and the smaller, more complexly shaped carpal bones, but the near-zero mean biases indicate that the tool does not systematically drift away from established values.

Crucially, all target bones were successfully tracked in both the 3DCT and 4DCT datasets, meaning the hierarchical registration algorithm converged on correct solutions in every case tested. This robustness matters because registration algorithms can occasionally fail, locking onto incorrect alignments or diverging entirely, and such failures typically demand time-consuming manual intervention. A semi-automated tool that reliably succeeds across diverse bones, motion tasks and imaging protocols removes a significant bottleneck. Manual bone tracking in CT volume sequences can take hours per bone per trial, and the labor multiplies rapidly in studies involving multiple participants, multiple bones and dozens of motion cycles. By automating this process within a validated framework, 3DH promises to accelerate the pace at which wrist biomechanics data can be collected and analyzed.

The choice to build the module inside 3DSlicer, and specifically within the SlicerAutoscoperM extension, is a deliberate strategic decision with implications well beyond the wrist. 3DSlicer is a free, open-source platform for medical image computing and visualization with a large international user base spanning research, clinical and educational communities. By embedding 3DH in this ecosystem, the developers have made the tool immediately available to any laboratory already working with 3DSlicer, complete with the platform’s established infrastructure for loading DICOM data, segmenting anatomical structures and visualizing results. The authors note that the ability to track bones from both 3DCT and 4DCT data sources, with agreement to prior methodologies, demonstrates that the 3DH approach is a capable tool that could promote collaboration and consistency of results through open-source software.

Consistency is a quietly urgent issue in biomechanics. When different laboratories use different proprietary tools with undisclosed algorithms, it becomes difficult to distinguish true biological differences between study populations from mere methodological discrepancies. Open-source registration changes that calculus: the code can be inspected, verified, extended and reused, and results from different institutions become directly comparable because they are produced by identical algorithms. This transparency also lowers the barrier to entry for research groups in settings that cannot afford commercial licenses, potentially broadening the global community capable of conducting rigorous skeletal kinematics research.

The study itself emerged from a collaboration spanning several institutions. The team included Joseph J. Crisco, Amy M. Morton and John D. Holtgrewe of the Department of Orthopedics at The Warren Alpert Medical School of Brown University and Rhode Island Hospital; Cesar Lopez, Andrew Thoreson and Kristin D. Zhao of the Assistive and Restorative Technology Laboratory and the Department of Physical Medicine and Rehabilitation at the Mayo Clinic in Rochester, Minnesota; and Jean-Christophe Fillion-Robin and Beatriz Paniagua of Kitware Inc. in Clifton Park, New York. The involvement of Kitware, a company known for its leadership in open-source scientific computing, underscores the blend of academic rigor and software engineering expertise required to produce a research tool robust enough for widespread distribution. Funding was provided by the National Institute of Arthritis and Musculoskeletal and Skin Diseases of the National Institutes of Health under award numbers AR059185, AR078924 and AR071338.

The implications of this work extend naturally to the future of musculoskeletal imaging. As newer CT technologies, including photon-counting detector systems, deliver ever-finer spatial resolution and as dynamic 4DCT becomes more widely available, the volume of image data available for kinematic analysis will grow dramatically. Tools like 3DH, which are fast, semi-automated and validated across modalities, will be essential for converting that imaging bounty into quantitative biomechanical knowledge. For patients with wrist disorders, the downstream promise is equally tangible: better measurements of how carpal bones actually move in living joints can inform more accurate diagnoses, improved surgical planning, more realistic computational models of joint loading and ultimately better-designed treatments for conditions ranging from scapholunate instability to thumb-base arthritis. With the tool now openly available in the 3DSlicer environment, researchers around the world can begin putting it to work.

A recent analysis of bones found in two separate underwater cave systems in South Australia has provided researchers with a new framework for investigating how animal remains, including those of extinct megafauna, came to rest in these submerged environments. 

Well-preserved bones have often been found in submerged caves, but interpreting how they accumulated and what happened to them afterward has been difficult. Researchers have had limited tools for determining the environmental processes that alter remains over time.

The new study, led by Griffith University PhD candidate Meg Walker and Professor Julien Louys of the Australian Research Centre for Human Evolution, identifies physical, chemical, and molecular markers that can provide clues about the environmental conditions each specimen experienced. The findings were published in PLOS One.

Reading the Fingerprints Left on Cave Bones

With help from specialist cave divers from the Cave Divers Association of Australia, Walker’s team examined animal bones recovered from Green Waterhole and Gouldens Sinkhole, two underwater cave systems near Mount Gambier, South Australia. Gouldens Sinkhole reaches 63 meters deep through a nearly 30-meter-wide shaft.

The researchers used radiocarbon dating methods on 41 specimens and examined them at various scales, starting with a visual evaluation of spatial distribution and surface wear before progressing to portable X-ray fluorescence, scanning electron microscopy, and protein analysis. Using these techniques, the researchers identified chemical residue, signs of bacterial damage, and traces of ancient DNA. The group also identified changes associated with different preservation environments by comparing submerged bones with those recovered from nearby dry caves.

Light, Algae, and Total Darkness

Light played an important role in some of the most noticeable changes to the bones. Near the cave entrances, where sunlight was available, algae and aquatic plants grew on the bone surfaces and left black biological stains, while cyanobacteria produced circular etchings and tunnels on the outer surfaces. Deeper within the caves, in areas where sunlight did not reach, the bones mostly stayed the same and retained their original characteristics.

This distinction is important because it shows that staining alone does not indicate that a bone was buried in sediment or fully submerged, as previously assumed. Instead, it shows that the bone was simply exposed to light.

A Different Kind of Damage on Dry Land

Bones from the dry sections of the cave systems showed different patterns. In the absence of water and algae, land-based bacteria penetrated the bone from within, while plant roots created long grooves on the surface as they grew in search of nutrients. These features are distinct from those observed in submerged specimens.

Cows, Kangaroos, and One Very Specific Sheep

The bones in the team’s study were not from ancient megafauna, belonging instead to cattle, kangaroos, emus, sheep, pigs, dingoes, rabbits, possums, quolls, and swamp rats. European settlers likely deposited the specimens in the caves after they arrived in the Mount Gambier region in the 1840s. DNA tests showed that one bone came from a Merino sheep.

A Deeper Mystery Still Submerged

The ultimate goal is to apply this framework to older material. Caves in the Mount Gambier region, such as Tank Cave and Englebrechts Cave, have yielded remains of Australia’s Pleistocene megafauna, including Diprotodon, a large marsupial similar in size to a rhinoceros, Thylacoleo carnifex, the largest known marsupial predator, and short-faced kangaroos that reached about 2 meters in height. Some of these fossils have remained undisturbed for more than 60,000 years.

Using Walker’s framework when looking at these specimens might help researchers understand how Australia’s megafauna fossils accumulated and could also provide a method for investigating factors such as human activity and environmental change that caused their extinction.

“This study has delivered the first framework for interpreting how megafauna fossils formed, survived, and changed in underwater caves,” Walker said. “It will provide archaeologists and paleontologists worldwide with a powerful new tool for reconstructing past environments and histories in these challenging conditions.”

Austin Burgess is a writer and researcher with a background in sales, marketing, and data analytics. He holds an MBA, a Bachelor of Science in Business Administration, and a data analytics certification. His work focuses on breaking scientific developments, with an emphasis on emerging biology, cognitive neuroscience, and archaeological discoveries.

Semaglutide was linked to greater weight loss and a 15% lower fracture risk in people with type 2 diabetes, raising the possibility of an unexpected bone health benefit. People with type 2 diabetes who took semaglutide experienced greater weight loss and a lower risk of bone fractures than those using several other weight-loss medications, according [...]

A newly identified vitamin K-dependent signaling pathway appears to help coordinate communication between key bone cells. Bones may seem like lifeless structures, but they are constantly being torn down and rebuilt. Every day, specialized cells remove old bone while others replace it with new material, a process that keeps the skeleton strong and adaptable throughout [...]

A new study suggests that some groups may not experience the expected seasonal boost in vitamin D levels, even during the sunniest months of the year. Many people assume that spending more time outdoors during summer naturally restores vitamin D levels after the darker winter months. But new research suggests that for some groups, that [...]

Carbon-14 dating consistently reveals that dinosaur remains date to less than 40,000 years old, contradicting the conventional geological timeline of millions of years. This finding, along with evidence of preserved soft tissue, supports a Young Earth perspective and challenges the Old Earth paradigm as presumed in mainstream science.

New evidence suggests calcium and vitamin D supplements may do far less to prevent fractures and falls than widely believed. Calcium and vitamin D supplements, whether taken separately or together, provide little to no meaningful benefit in preventing fractures or falls in most older adults, according to a major review published in The BMJ. Nearly [...]