The advent of 3D printing has markedly transformed various sectors, and medicine is no exception. Within surgical applications, creating patient-specific implants, particularly for cranial reconstruction, has become increasingly feasible. This advancement leverages technologies like handheld 3D scanners and additive manufacturing to produce models and implants, offering potentially superior solutions compared to traditional methods. The focus on precision, biocompatibility, and efficient workflows is paramount in this field. Exploring the process of utilizing 3D scanning and 3D printing for creating accurate skull models and implants highlights both the current capabilities and areas for future refinement in this exciting domain.
Enhancing Precision in Skull Modeling with 3D Scanning Technology
Creating accurate 3D models of the human skull is the foundational step for many medical applications, ranging from surgical planning to the fabrication of customized cranial implants. Handheld 3D scanners, such as the Artec Leo, offer a compelling solution for capturing the complex geometry of the skull. These devices often feature real-time processing and integrated touch screens, allowing for immediate visualization and on-the-fly correction of scan data. This interactivity is crucial in ensuring comprehensive data capture, although challenges such as maintaining consistent scanning paths and avoiding gaps in the model can arise. Sophisticated software applications designed for contour closure and hole-filling are essential tools to address these potential imperfections and refine the initial scan into a complete and accurate 3D skull model [31].
The portability and wireless operation of handheld scanners are particularly advantageous in clinical settings, enabling easier data acquisition directly in the operating room or examination room. Initially, a hurdle was encountered in efficiently scanning both the inner and outer surfaces of cranial bone flaps and subsequently merging these scans into a cohesive digital model. Rotating the object for complete capture increased the risk of scan interruption. To mitigate this, transparent scanning aids, adaptable in size and sterilizable, were developed. These aids streamline the scanning process and simplify the subsequent alignment and merging of scan datasets, leading to more robust and accurate 3D skull representations. While rapid scanning is achievable, it’s crucial to recognize that scan duration alone doesn’t guarantee improved accuracy. Establishing distinct reference points around the scanning area can be beneficial, enabling easier realignment of the scan if interruptions occur.
Designing Patient-Specific 3D Printed Skull Implants
Once a precise 3D scan of the skull defect or anatomy is obtained, the design phase for a 3d Printed Skull implant commences. The digital skull model, ideally a closed and solid mesh, serves as the blueprint for implant creation. The field of reverse engineering plays a vital role in adapting scanned models for manufacturing, particularly in refining the edges and contours to ensure optimal fit and function. Computer-Aided Design (CAD) programs are indispensable tools in this stage, allowing for the precise manipulation and refinement of the 3D skull model to design an implant that perfectly matches the patient’s unique anatomy. The versatility of CAD software ensures that this design approach is applicable to various skull shapes and anatomical complexities, making it a universally adaptable methodology for creating customized 3D printed skull implants. The ultimate goal is to convert the digital surface model into a manufacturable implant design, a process that has proven successful across a range of cranial reconstructions.
Accuracy and Material Selection for 3D Printed Skulls
Ensuring the accuracy of 3D printed skull implants is paramount for successful surgical outcomes. Studies comparing 3D scans to CT-derived models reveal a tendency for the scanned models to exhibit slight shrinkage. This phenomenon is more pronounced at the edges of the bone flaps, impacting the overall dimensional accuracy, especially in thinner sections of the skull. Deviation analysis, as shown in Table 1 of the original study, highlights these discrepancies. For instance, test case K8 demonstrated an average deviation of -0.30 mm, with a maximum positive deviation of 0.58 mm and a minimum deviation of -1.13 mm. The minimum deviation is often attributed to the inherent challenges in scanning thin structures accurately. Furthermore, the segmentation process in CT imaging, which relies on grayscale differentiation to capture bone structure, can introduce its own set of deviations, particularly in cancellous bone regions where holes may be present in the segmented model.
Table 1 Data from the accuracy study. Overview of the average, maximum and minimum deviationFull size table
Despite these deviations, when compared to retrospective studies on cranioplasty implant accuracy, the deviations observed with 3D scanned and printed implants fall within an acceptable range. However, ongoing efforts to minimize these discrepancies are crucial to further enhance the precision and fit of 3D printed skull implants. It’s important to note that handheld scanners, while versatile, are inherently user-dependent. Stationary 3D scanners offer the potential for greater accuracy and could be seamlessly integrated into surgical workflows due to their compact designs.
Material selection is another critical aspect of 3D printed skull implant fabrication. Titanium and PEEK (polyetheretherketone) have emerged as leading materials due to their biocompatibility and sterilizability. Titanium implants are typically manufactured using Selective Laser Melting (SLM), while PEEK implants are produced via Fused Deposition Modeling (FDM). Extensive testing and validation are necessary to ensure the chosen printing process yields implants meeting the stringent requirements for medical applications.
Quality Assessment of 3D Printed Skull Implants
Rigorous quality control is essential to guarantee the integrity and performance of 3D printed skull implants. Various methods are employed to assess print quality, including dimensional accuracy and material integrity. Haptic measurement methods prove less suitable for complex geometries due to probe limitations and time-consuming data acquisition. High-resolution 3D scanners offer a more effective approach for capturing the intricate surface details of printed parts. Furthermore, micro-computed tomography (µ-CT) is particularly valuable for evaluating the internal structure of PEEK implants.
Nominal/actual comparisons reveal that deviations tend to increase with component size for both PEEK and titanium, although deviations are generally smaller for titanium. Microscopic analysis of PEEK samples reveals the presence of pores (blowholes), whereas titanium samples produced via SLM exhibit a denser, pore-free microstructure.
CT imaging further confirms the presence of internal defects in PEEK implants, often aligned with the printing direction due to the FDM process. Optimizing printing parameters, such as shorter printing paths and controlled material deposition, can help minimize these defects in PEEK. In contrast, titanium implants produced by SLM generally exhibit fewer internal defects and are less susceptible to directional dependencies.
Conclusion: The Future of 3D Printed Skulls in Medicine
3D printing technology offers a transformative pathway for creating patient-specific skull implants, promising improved surgical outcomes and personalized medical solutions. The combination of handheld 3D scanning for accurate skull geometry capture and additive manufacturing techniques for implant fabrication presents a powerful paradigm shift in cranial reconstruction. While challenges remain in achieving absolute accuracy, particularly with handheld scanners and certain materials like PEEK, ongoing advancements in both scanning and printing technologies are continually refining the precision and reliability of 3D printed skull implants. The use of titanium and PEEK, coupled with rigorous quality assessment methods, ensures biocompatibility and structural integrity. As research and development progress, 3D printed skulls are poised to play an increasingly vital role in revolutionizing cranial surgery and enhancing patient care.
