A Review on 3D Scanners Studies for Producing Customized Orthoses

1. Introduction

Orthoses are external medical devices designed to support users' biomechanical needs, significantly contributing to their quality of life [1,2]They serve as pivotal elements in controlling and restoring the functionality of the injured body part [3,4]. Customized orthoses, tailored to individual measurements, exhibit innovative attributes concerning device ventilation, thereby minimizing heat injuries, pressure wounds, and skin breakage [5,6].

Traditionally, a custom-made orthosis has been manufactured using a plaster cast. This conventional practice has several downsides including high plaster consumption, time-intensive processes, being invasive for patients, and lacking data storage for future reference. To circumvent these medical challenges, reverse engineering techniques have been employed, necessitating three-dimensional (3D) geometric data acquisition. A paramount requirement for orthoses is comfort, which is attained through a high level of customization facilitated by an accurate capture of the patient's anatomy [7,8] Given that each patient possesses unique body geometry, custom-made orthoses have emerged as the "gold standard" since the orthosis geometry is individually adapted for each patient [9,10]. The journey towards acquiring a custom-made orthosis entails several stages including scanning (digitization), importing the scanned data into a computer to create a computer-aided design (CAD) file, modeling, topological optimization, and 3D printing [11,12,13,14]. The digitization phase is a linchpin in this process. To generate a reliable CAD file of the limb, the patient is required to remain still for a certain duration during the acquisition process, hence, fast scanning systems are highly desirable [15].

In recent years, a plethora of 3D scanners has been introduced to expedite the manufacture of customized orthoses. Most digitization systems leverage laser scanners (e.g., HandyScan, Faro), structured light (e.g., Vorum, Artec, Sense 3D), photogrammetry software amalgamated with conventional cameras (e.g., PhotoModeler, 3DSOM, My3DScanner, PhotoScan, 123D Catch, Hypr3D, RhinoPhoto), or a blend of diverse technologies. These technologies compute a cloud of three-dimensional points of the object employing the principle of optical triangulation to shape the natural geometry [3,9,12,16,17]. The selection of the most suitable 3D scanner is contingent on the application and the requisite accuracy [18,19].

This review endeavors to scrutinize the application of 3D scanners on human limbs to create a CAD for constructing an orthosis. The investigation also extends to examining the advancements in 3D scanning technology and how these evolutions are influencing the bespoke production of orthoses, enhancing the precision in capturing patient's anatomy, and thereby contributing to better patient outcomes.

2. Materials and Methods

To identify the articles that could be included in this review, the searches were carried out between August and September 2023 in the Web of Science and SCOPUS databases. Searches related to the 3D scanner (3d scanner, photogrammetry, reverse engineering, optical scan, laser scanning, structure light) combined with terms for Orthoses (orthosis, orthoses) and medical device were performed. No restrictions were applied to the year or type of publication.

Original articles written in English with 3D scanners used to acquire human limb to make custom orthotics were included. All narrative, systematic reviews and dissertations were excluded. Any articles not written in English were excluded. Any article with another scanner device (ex. computational tomography (CT) or X-ray) were excluded. Articles using 3D scanners other than for obtaining the human body and other than for orthoses were excluded. Articles whose purpose uses 3D scanners for prostheses were also excluded.

After the removal of excluded articles and deletion of duplicates based on PRISMA, data extraction was standardized. Titles and abstracts from the search results were screened using the eligibility criteria and reviewed by two authors (R.S. e B.S.) for inclusion. Data extraction and evaluation of the remaining articles were performed independently by the same authors. In case of disagreement, an additional reviewer (P.M.) was consulted. Data extraction included first author and year, the aim of the study (reverse engineering, 3D scanner and different types, orthoses) among others.

3. Results

Figure 1 summarizes the results of the different steps to identify appropriate articles for the review, based on PRISMA guidelines [20]. The initial database search identified 4912 articles, and after duplicate removal, 4110 were considered potentially relevant and were screened for relevant content. No additional articles were identified following a hand search of reference lists. After reading the title and abstract of the 4110 articles, 327 were selected for possible inclusion in this systematic review and full-text articles were retrieved. In the last phase, 20 of the 327 articles were included in this review.

4. Discussion

The production of customized orthotics has increasingly garnered attention, with projections indicating a significant surge in their utilization over the next decade. This growth is primarily attributed to advancements in 3D scanning technologies, which are becoming faster, simpler, and more effective [27]. The clinical and research applications of 3D scanning systems, particularly in anthropometric measurement, have been well-documented. Considering growing concerns regarding the use of radiation in medical imaging, these systems offer a safer alternative by minimizing patient exposure to radiation, as seen with X-ray or computer tomography.

Despite their potential, the integration of new 3D technologies in the National Health Service remains limited. The main hurdles are the high costs involved, as well as the time and training required for prosthetist orthotist professionals to adapt to using 3D Scanners. Overcoming these challenges could revolutionize the process of supplying customized orthoses, making it more efficient and cost-effective [1]. Several studies have validated the feasibility of Additive Manufacturing (AM) and scanners in producing customized daily living aids. This approach is expected to significantly enhance the quality of life at a reduced cost[1,3,15,18,25,27,28,30,32]. Patients have expressed a preference for scanning over traditional plaster casting methods [1]. The 3D-printed orthoses are noted for their accurate geometrical correspondence to patient anatomy and comfortable fit, striking a balance between precision and affordability [11,21].

Various types of 3D scanners are utilized for acquiring human anatomy, each serving a specific purpose in the manufacture of custom orthotics. These include photogrammetry [9,11,22,23,26,29,46], structured light [7,12,15,21,24,25,32,34,35,36,39,47], laser scanning [1,18,27,41,42,43], and optical scanning [7,30,31,37,40,45], as well as combinations of these technologies [3]. The choice of scanner is dictated by the healthcare professional’s specific needs, as each type has its own set of advantages and limitations for anatomical acquisition. Photogrammetry, for instance, has emerged as a promising technique in digitization systems due to its rapid acquisition capabilities [48]. This method, which involves creating 3D meshes from multiple photographs taken from different angles, eliminates the issues of body movement during scanning and does not require markers on the patient [22]. It was first utilized in a medical context by Ciobanu et al. [23]. On the other hand, structured light technology works by projecting patterned light lines from a fixed source (like a camera), capturing detailed coordinates of the scanned model, including colors and textures [49,50,51]. However, this technology has the drawback of requiring longer scanning times, which can be challenging for patients who find it difficult to remain still, leading to inaccuracies in the final mesh.

Laser technology is typically employed for scanning shapes and surfaces. It efficiently gathers anthropometric data, aiding in the production of customized orthoses based on digital scans [27,52]. Nonetheless, its limited range can be a disadvantage, particularly for larger body parts like legs and feet, as the process becomes time-consuming [53]. Optical scanners, which project light over the body and trace surface topography, collect data to form a "point cloud." This data is then processed through computer algorithms to generate a precise model [54]. While these scanners are accurate, they require a balance between scanning speed and the resolution of their optical and electronic components to produce a clean CAD model [55]. Ultimately, the choice of 3D scanner should not only consider the radiation safety but also the quality and accuracy of the anatomical model needed for orthosis construction. Traditional plaster casting methods are invasive and time-consuming. In contrast, 3D scanning offers a non-invasive, quicker alternative.

When comparing different technologies, photogrammetry enables rapid capture, but its processing time can be lengthy [22]. For example, Weigert et al. [26] found that while capturing 62 photos through photogrammetry took only 30 minutes, the reconstruction process was time-consuming. Belokar, Banga, and Kumar [3] combined laser and structured light technologies, completing a scan in just one minute by manually rotating the scanner around the patient's limb. Despite the processing times, these methods are still faster than traditional plaster casting.

Grazioso et al. [22] highlighted the advantages of having a body scanner in medical centers, emphasizing its minimally invasive nature and simplicity for medical practitioners. Comparing AM Ankle-Foot Orthoses (AFO) with conventional ones, patients favored the AM AFO for its lighter weight and ease of use, despite the conventional AFO being more effective in some aspects [28]. Significantly, four studies [39,40,45,47] employed the Quebec User Evaluation of Satisfaction with Assistive Technology (QUEST) test to evaluate dimensions, weight, adjustments, safety, durability, simplicity, comfort, and effectiveness. Two of these studies involved orthoses designed using 3D structured light scanners, and their findings demonstrate that patients are more satisfied with 3D-printed orthoses than with conventional orthoses. These observations underscore the critical role of patient-centered design in orthotic development, where customization and material choice are pivotal in enhancing the user experience. The integration of evaluation tools like QUEST into clinical practice provides invaluable insights for healthcare professionals, facilitating a deeper understanding of patient needs and preferences. This comprehension is crucial in guiding the selection and design of more effective and comfortable orthotic solutions, particularly in rehabilitation contexts. Such patient-centric approaches in orthotic design not only cater to functional needs but also significantly improve the overall satisfaction and quality of life for the users.

Parry, Best, and Banks [27] used a laser scanner for data collection, taking approximately 10 minutes, with a manufacturing time of over 10 hours and a cost of €10.90. Their study reinforced the viability of AM and scanners in producing cost-effective, customized aids for individuals suffering from conditions like arthritis [27].

From a biomechanical perspective, the study by Mo et al. [36] compared standard and 3D printed orthoses created using 3D scanners and AM technologies. They found lower peak rearfoot eversion angles during running with both types of orthoses compared to running barefoot, although no statistical differences were observed between the orthoses. Similarly, Telfer et al., employing the same patient data acquisition methodology [42,43], demonstrated that customized foot orthoses could provide a dose-response effect for selected plantar pressure variables. However, they found no corresponding effect on muscle activity. They further noted a dose-response effect, with a linear trend for both the rearfoot and knee, in treating pronated foot type with customized foot orthoses.

Another significant aspect is the application of 3D scanners and AM in clinical practice. Zheng et al. [37] reported that AM orthoses resulted in better outcomes compared to low-temperature thermoplastic plate orthoses in reducing spasticity and swelling, and in improving motor function and passive range of wrist extension in stroke patients. Additionally, Lee et al. [40] designed and manufactured a patient-specific assistive device using 3D printing techniques, optimized for the functional needs of a patient with brain injury, after assessing the patient’s disability status.

From a global perspective, photogrammetry stands out as one of the most promising options due to its accuracy, minimal acquisition time, and high-fidelity color [22] and shape reproduction [30]. The subsequent step involves transferring the acquired data to CAD software for mesh adjustment and measurement processing. Various reverse engineering software like Rhinoceros, Rapidform, Geomagic, and LeiosMesh are used, although this stage is time-consuming and demands high expertise from the user. The challenge lies not only in the orthotist-prosthetist proficiency with 3D Scanners but also in the user-friendliness of these software systems, which are not yet optimally aligned for direct orthosis construction [21,41].

5. Conclusions

Nowadays it is possible to obtain the anatomy of the human being with 3D scanners, however, it is still necessary to decrease the digitization time, to prevent the patient from having any type of minimal movement. In general, the studies analysed have shown that photogrammetry will be the most suitable type of 3D scanner for the 3D acquisition of the human body for custom orthotics. It is also believed that more and more scientists in the field will build 360º 3D scanners, based on photogrammetry, where they can perfectly capture the anatomy of the human limb with just one shot. The method of build custom-made orthoses with plaster cast are the same since the beginning of this method. With today’s technology, there is a chance to evolve from the traditional method to a better one to help the patient and professional needs. With the 3D scanners being more affordable nowadays is possible to introduce this technology in clinics and provide proper training for health professionals, however, it is necessary to create new specific software’s to build orthoses in an easy and fast way.