Printing a 3-dimensional, Patient-specific Splint for Wound Immobilization: A Case Demonstration
Abstract
Three-dimensional (3D) printing technology can generate objects in almost any shape and geometry. This technique also has clinical applications, such as the fabrication of specific devices based on a patient’s anatomy. A demonstration study is presented of a 54-year-old man who needed a thermoplastic splint to limit arm movement while a dehisced left shoulder wound healed.
The patient’s upper extremity was scanned using the appropriate noncontact scanner and 3D technology software, and the polylactic acid splint was printed over the course of 66 hours. This patient-specific splint was worn during the day, and after 2 weeks the wound was healed sufficiently to permit hospital discharge. Creation of an individualized splint is one of many potential medical uses of 3D technology. Although the lengthy printing time imposes limitations, the implications for practice are positive.
The digitization of manufacturing using cutting-edge software, materials, robots, new processes (notably 3-dimensional [3D] printing), and web-based services has revolutionized production methods.1 Traditional production methods involve machining parts from blocks of material and then screwing or welding them together. Products now can be designed on a computer and printed on a 3D printer, which basically creates the object by building upon successive layers of material. Such printers can produce numerous objects that are too complex for a traditional factory to handle. The development of 3D printing has evolved in 4 successive stages: rapid prototyping in the early 1990s, rapid tooling in the late 1990s, direct manufacturing in the late 2000s, and home fabrication, with end-users manufacturing objects using 3D printing equipment at home, in the early 2010s.2
The application of 3D printing in medical fields requires regulatory compliance; for example, a medical device should be approved by United States Food and Drug Administration (FDA) before marketing. The first 3D-printed item — a titanium skull implant — was created in 2006.3 This type of device has since been employed successfully in other scenarios where 3D printing has opened a world of potential medical applications.4 Similar to the first prototyping phase developed in industry, medical doctors use routine medical images, such as computerized tomography (CT) or magnetic resonance imaging (MRI), to construct 3D models. The 3D model then can be either manipulated in a computer or printed for treatment planning or surgical simulation.5-7
When they were first made, 3D-printed organs were created to train junior physicians. The 3D-image and printout could accurately represent the anatomy of the specific patient and the senior physician could explain the surgical planning to the patient and residents or interns. This use has evolved. Similar to the 3D printing rapid tooling developed in industry, surgeons have demonstrated that 3D printing is feasible and promising to use as a surgical guide for complex surgical procedures, such as surgical treatment of complex acetabular fractures8 and (as shown in a case study) improvement of joint function after reconstruction of a malignant bone tumor around the knee joint.9 In liver tumor surgery, for example, the 3D-image and printout can adequately show the hepatic and portal veins, enabling the surgeon to plan the surgical route to avoid bleeding. Using 3D technology in both treatment planning and surgical simulation has shown promising results.8,9
Patient-specific implants involve the direct manufacture and fabrication of end-use products with 3D printers that have been used to create shoulder, hip, and craniomaxillofacial implants.10-12 Facilities may use bioprinters that utilize 3D printing techniques to combine cells, growth factors, and biomaterials to fabricate biomedical parts with natural tissue characteristics; this process is still in the very early stages.13,14 Home fabrication (ie, end users manufacturing objects themselves using 3D equipment) is still under development in the industry.2
In 2015, a Forbes report15 predicted “3D-printed hip and knee replacements, as well as other common internal and external medical devices, will be in mainstream use within 2 to 5 years.” Within the year, the US FDA approved 3D-printed oral medication (tablets)16 used to treat epilepsy, 3D-printed medical implants, 3D-printable material used as a denture base,17 and the first patient-specific cervical rod18 using 3D printing technology.
To keep pace with the technological revolution and offer patients the newest options, the authors have been working on 3D printing at the Taipei Veterans General Hospital (Taipei, Taiwan) since October 2015. Taiwan FDA released 3D printing guidance in January 2018; thus far, 3D printing technologies are utilized mainly for modeling and surgical guides as previously described, because such use presents a low risk for patients.
Because the authors could find no literature on the risks and benefits of creating 3D devices for medical application, the purpose of this case study was to describe the use of 3D printing technologies to generate a patient-specific splint device for wound care.
Case Report
History. Mr. C was 54 years old when he was diagnosed with hepatocellular carcinoma for which he underwent a hepatectomy in 2011. Two (2) months later, he experienced persistent muscle soreness and tingling pain over his center trunk. A whole-body bone scan revealed bone metastasis over his left proximal humerus. Preoperative x-rays revealed an osteolytic lesion over his left proximal humerus with pending pathological fracture (see Figure 1). He subsequently underwent left hemishoulder arthroplasty in December 2011. The tumor was widely resected, as shown in the intraoperative photograph (see Figure 2). After tumor excision, the bone defect was reconstructed by long-stem hemiarthroplasty, and a titanium alloy artificial joint was implanted (see Figure 3). After reconstruction, Mr. C returned to normal daily life.
In December 2015, Mr. C noticed persistent, painful swelling of his left shoulder; infection was diagnosed based on routine clinical signs but without culture or biopsy. Orthopedic surgeons at the authors’ facility debrided and then closed the wound over his left shoulder with mesh and tape in April 2016. Wound discharge was noted 3 months later, and progressive shoulder pain and redness recurred in August 2016; septic arthritis was diagnosed. Due to deep infection, the artificial joint prosthesis was resected and high-dose vancomycin-impregnated polymethylmethacrylate was inserted to control the infection (see Figure 4). 
Plastic surgeons reconstructed the defect using a latissimus dorsi muscle flap and split-thickness skin graft on November 23, 2016; 5 months later, Mr. C visited the outpatient department with new wound dehiscence and was readmitted to the hospital for debridement and local flap repair in April 2017. During his hospital stay, Mr. C was asked to decrease movement of his left hand to facilitate wound healing. His physicians noticed that he constantly used his right hand to hold his left hand. They decided to use 3D technology to generate a patient-specific splint (PSS) to help immobilize the arm. Use of a readily available type of splint was avoided because Mr. C had just undergone debridement and local flap repair, and using a ready-made splint would involve the painful bending of his arm and potential added tension on the wound.
Modeling. The dimensions of the patient’s whole arm were captured using a handheld 3D scanner (Eva; Artec 3D, Luxembourg) that uses safe, structured, light-scanning technology to capture an object’s dimensions and shape. The scanner is equipped with post-processing software that can erase unneeded portions of an object. In this case, Mr. C’s upper extremity was scanned; the result is shown in Figure 5. Based on the 3D upper extremity model scanned, computer-aided design (CAD) software (Meshmixer; Autodesk, San Rafael, CA) was utilized to build the splint model. Clinicians marked the area on the computer model that required the splint and extracted the relevant dimensions, extending the surface area to 3-mm thickness to obtain the 3D splint model (see Figure 6).
The 3D model was saved in an stereolithography (.stl) file format. Using this file, this printer technology creates an object by building up material layer by layer; logically, the bigger the object, the longer the printing time. Numerous professional 3D printing companies provide outsourcing worldwide.
3D printing. The authors’ 3D printing equipment center includes D-Force 500 (D-Force. Taiwan, Kaohsiung, Taiwan), Form 2 (Formlabs, Inc, Somerville, MA), UpBox (Tiertime, Beijing, China), and other home assembly components (users assemble the device). The D-Force 500 was selected for use because it has the capacity to print longer objects, and the arm splint needed to be approximately 400 mm long. Printing took approximately 66 hours and polylactic acid, a biodegradable thermoplastic derived from renewable resources such as corn starch or sugar cane, was used to create the splint. As shown in Figure 7, Velcro straps were attached to affix the splint on the patient. 
If any events interrupt the process, the printing must be repeated; for example, if the filament tangles, the printing process may fail. This occurred in the process of creating the splint, but ultimately printing was successful.
Splint application. Once the splint was applied, the hospital course of care went smoothly. Mr. C wore the PSS during the day and rested his arm on a soft pillow at night. Because the PSS helped Mr. C hold and protect his left hand, the splint appeared to help expedite the wound healing process. The wound showed signs of healing, presumably because tension on the wound was reduced; no pain or swelling was noted and signs of infection no longer were present. Mr. C was discharged in stable condition <2 weeks after his admission for debridement and flap repair. The wound continued to appear to be healing at the postdischarge follow-up 1 week after discharge. Because Mr. C had terminal liver cancer, he decided not to have any artificial joint implant on his left shoulder, choosing instead to occasionally wear the splint for support. After returning to normal daily life, he wrote an appreciation letter to the Hospital Superintendent, noting that the PSS promoted his wound healing.
Discussion
The digitization of the manufacturing process via 3D printing has dramatically changed production methods of items previously available only through standard production means.1 According to a review article20 and the authors’ experience using 3D applications in medical fields, the greatest advantage of 3D printing technology in medical applications is the ability to produce patient-specific devices. For example, news in medical field and reviews12,15,21 note the application of 3D printing to customize prosthetics and implants represents significant value for both patients and physicians.
To the best of the authors’ knowledge, no studies have reported the creation of a splint using 3D technology.22,23 Although 3D technology can create a splint without the need to touch the wound (as would occur using traditional thermoplastic materials), the 66-hour production time represented a serious limitation of 3D printing a splint. However, the benefits of not coming in direct contact with the wound outweighed the disadvantages of the print time. Furthermore, given that the left artificial joint was removed, the patient required fixation that might not have been possible using a traditional immobilization device. The 3D-printed PSS also demonstrated the advantage of customization; in addition, material costs were almost the same as that of traditional thermoplastic material.
Conclusion
To limit arm movement while a dehisced wound healed, 3D-printing technology was successfully used to create a PSS device. The main limitation of the using the 3D printing technology for this patient was the amount of time required (66 hours) to print the splint. With the utility and availability of 3D printing hardware progressing, the use of more precise and rapid 3D printers in the near future is expected.2 n
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Potential Conflicts of Interest: This work was supported in part by a Taipei Veterans General Hospital Research Grant (V106 E-003-1, V107 D39-001-MY2-1, and V107C-198), Taiwan.
Dr. Wu is the Division Chief, Therapeutical and Research Center, Musculoskeletal Tumor, Department of Orthopedic Surgery and Traumatology, Taipei Veterans General Hospital, Taipei, Taiwan; and an Assistant Professor, Institute of Clinical Medicine, School of Medicine, National Yang-Ming University, Taipei, Taiwan. Dr. Shih is a visiting staff member, Division of Plastic and Reconstructive Surgery, Taipei Veterans General Hospital; and a lecturer, Department of Surgery, School of Medicine, National Yang-Ming University. Dr. CM Chen is a visiting staff member, Department of Orthopedic Surgery and Traumatology, Taipei Veterans General Hospital; and a lecturer, Institute of Clinical Medicine, National Yang-Ming University. Dr. G Chen is a resident, Division of Plastic and Reconstructive Surgery, Taipei Veterans General Hospital; and a lecturer, Department of Surgery, National Yang-Ming University. Dr. WM Chen is Vice Superintendent, Taipei Veterans General Hospital; and the Associate Dean, Institute of Clinical Medicine, School of Medicine, National Yang-Ming University. Ms. Huang is a physiotherapist, Rehabilitation and Technical Aids Center, Taipei Veterans General Hospital. Mr. Hung is a physiotherapist, Rehabilitation and Technical Aids Center, Taipei Veterans General Hospital. Mr. Wang is a research assistant, Rehabilitation and Technical Aids Center, Taipei Veterans General Hospital. Mr. Yu is a research assistant, Rehabilitation and Technical Aids Center, Taipei Veterans General Hospital. Dr. CK Chang is a visiting staff member, Rehabilitation and Technical Aids Center, Taipei Veterans General Hospital. Dr. BC Chang is a visiting staff member, Rehabilitation and Technical Aids Center, Taipei Veterans General Hospital; and an Assistant Professor, Department of Biomedical Engineering, Chung Yuan Christian University, Taoyuan City, Taiwan. Dr. Lin is the Divisional Chief of Rehabilitative Treatment for Physical Dysfunction, Rehabilitation and Technical Aids Center, Taipei Veterans General Hospital. Dr. Wang is a Researcher, Rehabilitation and Technical Aids Center and Division of Experimental Surgery; and a Professor, Institute of Hospital and Health Care Administration, National Yang-Ming University. Please address correspondence to: Shyh-Jen Wang, PhD; email: wangsj@vghtpe.gov.tw; or Pei-Hsin Lin, MD, PhD; email: phlin2@vghtpe.gov.tw.