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.