Design and biomechanical analysis of patientspecific porous tantalum prostheses for knee joint revision surgery.

Artificial joint revision surgery, as an increasingly common surgery in orthopedics, often requires patient-specific prostheses to repair the bone defect. Porous tantalum is a good candidate due to its excellent abrasion and corrosion resistance and good osteointegration. Combination of 3D printing technology and numerical simulation is a promising strategy to design and prepare patient-specific porous prostheses. However, clinical design cases have rarely been reported, especially from the viewpoint of biomechanical matching with the patient's weight and motion and specific bone tissue. This work reports a clinical case on the design and mechanical analysis of 3D-printed porous tantalum prostheses for the knee revision of an 84-year-old male patient. Particularly, standard cylinders of 3D-printed porous tantalum with different pore size and wire diameters were first fabricated and their compressive mechanical properties were measured for following numerical simulation. Subsequently, patientspecific finite element models for the knee prosthesis and the tibia were constructed from the patient's computed tomography data. The maximum von Mises stress and displacement of the prostheses and tibia and the maximum compressive strain of the tibia were numerically simulated under two loading conditions by using finite element analysis software ABAQUS. Finally, by comparing the simulated data to the biomechanical requirements for the prosthesis and the tibia, a patient-specific porous tantalum knee joint prosthesis with a pore diameter of 600 µm and a wire diameter of 900 µm was determined. The Young's modulus (5719.32 ± 100.61 MPa) and yield strength (172.71 ± 1.67 MPa) of the prosthesis can produce both sufficient mechanical support and biomechanical stimulation to the tibia. This work provides a useful guidance for designing and evaluating a patient-specific porous tantalum prosthesis.

Highly Porous 3D Printed Tantalum Scaffolds Have Better Biomechanical and Microstructural Properties than Titanium Scaffolds.

OBJECTIVE: To test the biomechanical properties of 3D printed tantalum and titanium porous scaffolds. METHODS: Four types of tantalum and titanium scaffolds with four alternative pore diameters, #1 (1000-700 µm), #2 (700-1000 µm), #3 (500-800 µm), and #4 (800-500 µm), were molded by selective laser melting technique, and the scaffolds were tested by scanning electronic microscope, uniaxial-compression tests, and Young's modulus tests; they were compared with same size pig femoral bone scaffolds. RESULTS: Under uniaxial-compression tests, equivalent stress of tantalum scaffold was 411 ± 1.43 MPa, which was significantly larger than the titanium scaffolds (P < 0.05). Young's modulus of tantalum scaffold was 2.61 ± 0.02 GPa, which was only half of that of titanium scaffold. The stress-strain curves of tantalum scaffolds were more similar to pig bone scaffolds than titanium scaffolds. CONCLUSION: 3D printed tantalum scaffolds with varying pore diameters are more similar to actual bone scaffolds compared with titanium scaffolds in biomechanical properties.

Treatment of massive iliac chondrosarcoma with personalized three-dimensional printed tantalum implant: a case report and literature review.

Although customized three-dimensional tantalum implants have been used to treat a large variety of diseases, few reports have described the application of such implants to reconstruct large pelvic bone defects after the removal of massive tumors. We herein describe a 30-year-old woman with a 9-year history of a massive low-grade chondrosarcoma in the pelvic bone. After removal of a solid 12- × 8- × 6-cm tumor with clear margins, we used a customized three-dimensional printed tantalum implant to fill the large pelvic bone defect and performed hip arthroplasty in a one-step surgery. The patient's postoperative recovery was uneventful. She started walking 1 month after surgery, and she developed no tumor recurrence, instrumentation failure, or implant loosening during the 12-month follow-up period. This report describes the successful application of a customized three-dimensional printed implant to reconstruct a massive pelvic bone defect. Satisfactory functional recovery was achieved with no apparent complications. The methodology of the current case may benefit orthopedic and oncologic surgeons in designing treatment strategies for similar cases.

[Role of cerebral computed tomography in the evaluation of brain injury following hypoxia in neonates].

OBJECTIVE: To investigate the role of cerebral computed tomography (CT) in the evaluation of the severity of brain injury following hypoxia in neonates. METHODS: A total of 114 full-term newborns who had perinatal hypoxia, including 25 cases of hypoxic-ischemic encephalopathy (HIE), 36 cases of neonatal asphyxia and 53 cases of simple intrauterine fetal distress, were enrolled in this study. Twenty normal newborns served as the Control group. All had cerebral CT scan at 2-7 days of age. Neonatal behavior neurological assessment (NBNA) was performed at 5 days of age. RESULTS: The average NBNA scores were significantly lower and the abnormality rate of NBNA was significantly higher in the HIE group than in the other three groups (P < 0.05). The Asphyxia and the Distress groups had also lower NBNA scores and higher abnormality rate of NBNA than the Control group (P < 0.05). Twenty-two patients were found to have cerebral CT abnormality in the HIE group, but there was only 1 case in the Control group (P < 0.01). The abnormality rate of cerebral CT in the Asphyxia and the Distress groups was not statistically different from that of the Control group. Twenty-five cases of HIE were divided into mild (n=15), medium (n=6) and severe (n=4) by clinical grading but were divided into normal (n=3), mild (n=10), medium (n=7) and severe (n=5) by CT grading. CT and clinical grading on HIE was not consistent. The sensitivity of CT in the diagnosis of mild, moderate and severe HIE was 47%, 33% and 50% respectively, the specificity was 70%, 74% and 86% respectively and the accuracy was 48%, 64% and 80% respectively. CONCLUSIONS: CT evaluation on mild brain injury induced by asphyxia or intrauterine fetal distress is not of any value and the role of CT evaluation on the HIE grade is uncertain and doubtful.