Craniosynostosis, the premature fusion of one or more fibrous joints between the bones of the skull, affects roughly one in every 2,000 to 2,500 births in its typical forms. Because the skull must expand rapidly to accommodate a growing brain, early suture fusion forces the cranium to grow in compensatory directions, producing characteristic head shapes and, in some cases, raised intracranial pressure. Most cases are classified as primary, arising from genetic or developmental factors intrinsic to the suture itself. Secondary craniosynostosis, by contrast, is triggered by external or systemic influences, including metabolic bone disease, hyperthyroidism, or conditions that alter the biomechanical environment of the growing skull. The pattern reported in the new study appears to belong to this second category, but with features the authors say have not been documented together before.

The study population was narrowly and deliberately defined. The researchers reviewed charts of infants born at their institution between January 2020 and May 2025, including only those delivered at 22 to 28 weeks of gestation who went on to develop severe BPD and ultimately required a tracheostomy. Severe BPD is the most disabling form of chronic lung disease of prematurity, generally defined by a profound ongoing need for respiratory support well beyond the neonatal period. These infants spend months on mechanical ventilation, often at pressures far exceeding those used for typical neonatal care. Ten patients met all inclusion criteria, a small number that reflects both the rarity of this degree of respiratory morbidity and the single-center design of the review.

The most eye-catching quantitative result concerned head growth. Using standardized preterm growth charts and electronic growth chart calculators, the team tracked each infant’s head circumference percentile over time and found that the greatest four-week rise averaged 43 plus or minus 14 percentile points. That surge in head growth significantly outpaced concurrent changes in weight and length percentiles, a dissociation the authors report with a P value of 0.0023. In practical terms, these infants’ heads were growing dramatically faster than the rest of their bodies, the reverse of the growth faltering more commonly seen in chronic lung disease. The researchers also calculated a weighted mean sustained positive end-expiratory pressure of 10.6 centimeters of water across the cohort, a figure that quantifies the substantial ventilatory forces these infants’ chests and, potentially, their cranial circulation were exposed to for months.

Imaging told the rest of the story. Three-dimensional reconstructions of computed tomography scans of the head and maxillofacial region, presented in the published figures, revealed suture closure patterns described as atypical, alongside visible thickening of the calvarial bone, the dome of the skull. Calvarial thickening is not a feature of ordinary primary craniosynostosis and suggests an active bone-forming response rather than a simple failure of suture patency. The combination of rapid head circumference acceleration, abnormal suture fusion, and thickened skull bone led the authors to propose a novel phenotype of secondary craniosynostosis specific to this population of ventilator-dependent, tracheostomized infants with severe BPD.

The study was not the first to hint at this connection. The authors build on a 2023 report in the Journal of Craniofacial Surgery that described a similar phenotype of calvarial thickening and increased rates of premature calvarial suture closure in children with chronic lung disease. An earlier 2009 study had also associated rapid head growth in children following tracheostomy tube placement, suggesting that the airway intervention itself, or the underlying respiratory failure that necessitates it, may be linked to altered cranial growth dynamics. The new work sharpens the picture by focusing on a homogeneous group of extremely premature infants and by quantifying both the growth acceleration and the ventilatory pressures involved.

Why might prolonged high-pressure ventilation reshape a growing skull? The authors point to several plausible mechanisms that remain to be tested. Positive end-expiratory pressure, the pressure maintained in the airways at the end of each breath to keep the lungs open, is known from decades of neonatal physiology research to influence cerebral hemodynamics. Studies dating back to the late 1980s documented changes in cerebral blood flow velocity when positive end-expiratory pressure was adjusted in preterm infants, and more recent work has shown that ventilation mode changes can affect cerebral oxygen saturation. Sustained elevations in intracranial venous pressure or altered pulsatile forces transmitted through the dura could, in theory, alter the mechanical signaling environment of cranial sutures, which are exquisitely sensitive to tension and compression during development. Chronic hypoxia and the inflammatory milieu of severe BPD may add further systemic influences on osteoblast activity in the skull vault.

The clinical implications are potentially significant for both monitoring and intervention. Head circumference is routinely measured in neonatal follow-up care, but an accelerating head growth curve in a ventilator-dependent infant might currently be attributed to catch-up growth or, in some cases, mistaken for hydrocephalus. The new findings suggest that clinicians caring for infants with severe BPD on prolonged high-pressure support should consider cranial imaging when head growth accelerates disproportionately, since early identification of suture fusion can inform decisions about surgical release. Traditional management of single-suture craniosynostosis, as reviewed in the neurosurgical literature, ranges from observation to endoscopic strip craniectomy or open cranial vault remodeling, and the optimal approach for these medically fragile infants with thickened, abnormally remodeling skulls is entirely uncharted territory.

The authors are careful about the limits of their evidence. Ten patients from a single center, identified retrospectively, cannot establish causation, and the study lacked a comparison group of ventilated infants without severe BPD or of preterm infants managed with lower ventilatory pressures. The researchers explicitly call for prospective studies to define ventilatory exposure thresholds, clarify the underlying mechanisms, and determine the neurologic and surgical implications of this phenotype. Data availability is constrained by privacy protections inherent to such a small, reidentifiable cohort, though deidentified data may be shared upon reasonable request with institutional review board approval. The study protocol was approved by the Orlando Health Institutional Review Board, and the authors declare no competing interests.

Even with those caveats, the report opens an unexpected window onto how the environment of intensive care may leave structural marks on the developing body. The skull of an extremely premature infant is a dynamic, pliable structure whose sutures normally remain open for years to allow brain growth; the idea that months of positive-pressure breathing could accelerate bone deposition and suture fusion adds intensive care itself to the list of forces that sculpt cranial development. For the growing population of technology-dependent children who survive extreme prematurity, the findings underscore the need for long-term craniofacial surveillance and for research that treats the ventilator not merely as a life-sustaining tool but as a physiological exposure with consequences that may extend to the skeleton. As the authors conclude, only carefully designed prospective studies can determine whether this novel phenotype represents a true complication of modern neonatal intensive care and what it will mean for the neurodevelopmental and surgical futures of the children it affects.

Subject of Research: Atypical secondary craniosynostosis in ventilator-dependent premature infants with severe bronchopulmonary dysplasia

Article Title: Are premature infants with severe bronchopulmonary dysplasia at increased risk for atypical craniosynostosis?

Article References: Martin, S. G., Matrone, C., Stephens, M., Queliz Pena, T., Schreck, M., Guerrero, R. A., Zimmerman, A., Elbabaa, S. K., Jafrani, R., & Golden, B. (2026). Are premature infants with severe bronchopulmonary dysplasia at increased risk for atypical craniosynostosis?. Journal of Perinatology. https://doi.org/10.1038/s41372-026-02907-3

Image Credits: AI Generated

DOI: 10.1038/s41372-026-02907-3

Keywords: craniosynostosis, bronchopulmonary dysplasia, premature infants, mechanical ventilation, positive end-expiratory pressure, tracheostomy, head circumference, calvarial thickening, neonatology, craniofacial surgery, Journal of Perinatology, retrospective study

The research, published in the journal 3D Printing in Medicine, was conducted by a team from the Regional Hospital in Liberec, the Motol Faculty Hospital in Prague, the Faculty of Medicine in Hradec Kralove and the Technical University of Liberec in the Czech Republic. Led by Lukas Capek of the Department of Clinical Biomechanics, the group set out to answer a deceptively simple question: how well do the materials commonly fed into desktop fused deposition modeling printers actually mimic the mechanical behavior of pediatric cranial bone? The answer, distilled through mechanical testing and computer simulation, is that most of them do not, and that even the best candidate carries trade-offs that anyone building surgical training models needs to understand.

The team compared six widely available fused deposition modeling materials: polylactic acid, better known as PLA; acrylonitrile styrene acrylate, or ASA; PET-G; a commercial filament marketed under the name Simu Bone specifically for anatomical models; polypropylene, or PP; and thermoplastic polyurethane, or TPU. These were benchmarked against genuine ex vivo specimens of pediatric calvarial bone, the skull cap bone harvested with ethical approval from Motol University Hospital. The mechanical yardstick was the three-point bending test, a standard technique in which a sample is supported at both ends and loaded in the middle until it deflects, allowing researchers to extract the Young’s modulus, a measure of stiffness that describes how much a material resists elastic deformation.

The numbers revealed a striking spread. Native pediatric cranial bone exhibited a mean Young’s modulus of 375 plus or minus 204 megapascals, a value that reflects both the intrinsic softness of infant skull bone and considerable biological variability between specimens. Simu Bone, the filament explicitly designed to imitate bone, turned out to be dramatically too stiff, measuring 3380 plus or minus 14 megapascals, roughly nine times stiffer than the real tissue it is meant to emulate. At the opposite extreme, TPU was far too compliant at just 61 plus or minus 11 megapascals, behaving more like a flexible rubber than a cranial plate. Polypropylene emerged as the closest match to native bone mechanics, although the researchers note that printing with it posed practical challenges, since PP is notoriously prone to warping and poor bed adhesion on consumer printers.

Between those extremes sat the everyday workhorse filaments. PLA, ASA and PET-G, the materials most hobbyists and hospital makerspaces reach for first, all landed well above the stiffness of pediatric calvarial bone, meaning models printed from them will feel rigid and unyielding where a real infant skull would flex and give under surgical instruments. That discrepancy matters more than it might appear. In craniosynostosis procedures, surgeons rely on tactile feedback, feeling how bone bends, springs and fractures as it is cut, contoured and reshaped. A model that is nine times too stiff invites the trainee to apply far more force than would ever be safe in the operating room, while one that is too soft fails to convey the resistance that guides instrument handling.

The researchers also explored a popular workaround: tuning the infill density of the print. Fused deposition modeling builds parts as hollow shells filled with internal lattice patterns, and reducing the infill percentage is the easiest way to soften a printed part without changing material. The experiments showed that infill reduction does modestly decrease stiffness, offering a degree of tunability. But the effect is limited and gradual, and it cannot bridge the enormous gap between, say, a 3380 megapascal filament and 375 megapascal bone. Infill tuning, in other words, is a fine adjustment tool, not a substitute for choosing the right polymer in the first place.

Perhaps the most conceptually important finding came from the finite element analysis, the computational half of the study. The team built numerical simulations of the bending tests to explore whether matching a single global property such as overall elasticity is enough to make a printed model behave like bone. The simulations indicated that it is not. Regional deformation patterns, the way strain distributes across the geometry of a skull segment during loading, are critical for realistic simulation, and a material can match the average stiffness of bone while still deforming in the wrong places and in the wrong way. This finding pushes the field beyond the naive goal of hitting one target number and toward the harder challenge of replicating the spatial mechanical behavior of layered, heterogeneous cranial bone.

The implications reach well beyond the laboratory. Patient-specific three-dimensional printed models have become a mainstay of preoperative planning and surgical rehearsal for complex craniofacial cases, and they are increasingly central to training the next generation of neurosurgeons and craniofacial surgeons. Hospitals around the world have installed banks of desktop printers precisely because printed skulls are cheap, fast to produce and anatomically faithful, derived directly from patient imaging. This study adds a crucial caveat to that enthusiasm: anatomical accuracy without mechanical fidelity produces a model that looks right but feels wrong, and in surgery, feel is often what counts. The authors emphasize that anyone selecting materials for cranial training models must balance mechanical fidelity against printability, since the most mechanically faithful option, polypropylene, is also among the most difficult to print reliably.

There are also broader lessons for the growing field of medical simulation. The wide scatter in the native bone measurements, with a standard deviation of more than half the mean modulus, is a reminder that pediatric cranial bone is not a single well-defined material but a biological structure whose properties vary with donor age, skull location and the layered architecture of inner and outer cortical tables separated by diploë. Any single polymer, however well tuned, will be an approximation. The Czech team’s work, supported by the Ministry of Health of the Czech Republic under grant NW25-08-00228, provides the quantitative baseline that material scientists and biomedical engineers will need as they develop next-generation bone-mimicking filaments, and it gives surgical educators an evidence-based ranking for the materials they can buy today. For now, the practical takeaway is clear: if the goal is to rehearse surgery on an infant skull, polypropylene is the closest thing to bone that a standard fused deposition modeling printer can deliver, provided the printer operator is prepared to wrestle with its temperamental printing behavior.

Subject of Research: Comparative mechanical assessment of 3D printed skull materials versus pediatric cranial bone for craniosynostosis surgical training

Article Title: Comparative assessment of 3D printed skull materials and ex vivo bone for craniosynostosis training: a finite element analysis

Article References: Capek, L., Celisova, S., Taborsky, J., Vitvar, J., Benes, V., & Solfronk, P. (2026). Comparative assessment of 3D printed skull materials and ex vivo bone for craniosynostosis training: a finite element analysis. 3D Printing in Medicine. https://doi.org/10.1186/s41205-026-00347-5

Image Credits: AI Generated

DOI: 10.1186/s41205-026-00347-5

Keywords: craniosynostosis, 3D printing, fused deposition modeling, surgical training, finite element analysis, Young's modulus, pediatric cranial bone, polypropylene, Simu Bone, three-point bending, patient-specific models, surgical simulation