RESUMO
PURPOSE: The aim of the study was to evaluate the feasibility of a bioabsorbable cage consisting of magnesium and magnesium phosphate cement (MPC) in a porcine lumbar interbody fusion model. METHODS: Twelve male Ba-Ma mini pigs underwent lumbar discectomy and fusion with an Mg-MPC cage or a PEEK cage at the L3/L4 and L4/L5 level. Computed tomography (CT) scans were made to evaluate the distractive property by comparing average disc space height (DSH) before and at 6, 12, and 24 weeks after the operation. After the lumbar spines were harvested at 6 or 24 weeks after the operation, micro-CT examination was conducted to analyze the fusion rate, and stiffness of motion segments was investigated through mechanical tests. A histological study was performed to evaluate the tissue type, inflammation, and osteolysis in the intervertebral space. RESULTS: CT scans showed no significant difference between the two groups in average DSH at each time point. Micro-CT scans revealed an equal fusion rate in both groups (0% at 6 weeks, 83.3% at 24 weeks). Both groups showed time-dependent increases in stability, the Mg-MPC cages achieved an inferior stiffness at 6 weeks and a comparable stiffness at 24 weeks. Histologic evaluation showed the presence of newly formed bone in both groups. However, empty spaces were observed at the interface or around the Mg-MPC cages. CONCLUSION: Compared with the PEEK cages, the Mg-MPC cages achieved comparable distraction, fusion rate, and spinal stability at 24 weeks after the operation. However, due to inferior stiffness at the early stage and fast degradation, further modification of material composition and design are necessary.
RESUMO
MINI: A 3D printing technology is proposed for reconstructing multilevel cervical spine (C2-C4) after resection of metastatic papillary thyroid carcinoma. The personalized porous implant printed in Ti6AL4V provided excellent physicochemical properties and biological performance, including biocompatibility, osteogenic activity, and bone ingrowth effect. STUDY DESIGN: A unique case report. OBJECTIVE: A three-dimensional (3D) printing technology is proposed for reconstructing multilevel cervical spine (C2-C4) after resection of metastatic papillary thyroid carcinoma in a middle-age female patient. SUMMARY OF BACKGROUND DATA: Papillary thyroid carcinoma is a malignant neoplasm with a relatively favorable prognosis. A metastatic lesion in multilevel cervical spine (C2-C4) destroys neurological functions and causes local instability. Radical excision of the metastasis and reconstruction of the cervical vertebrae sequence conforms with therapeutic principles, whereas the special-shaped multilevel upper-cervical spine requires personalized implants. 3D printing is an additive manufacturing technology that produces personalized products by accurately layering material under digital model control via a computer. Reporting of this recent technology for reconstructing multilevel cervical spine (C2-C4) is rare in the literature. METHODS: Anterior-posterior surgery was performed in one stage. Radical resection of the metastatic lesion (C2-C4) and thyroid gland, along with insertion of a personalized implant manufactured by 3D printing technology, were performed to rebuild the cervical spine sequences. The porous implant was printed in Ti6AL4V with perfect physicochemical properties and biological performance, such as biocompatibility and osteogenic activity. Finally, lateral mass screw fixation was performed via a posterior approach. RESULTS: Patient neurological function gradually improved after the surgery. The patient received 11/17 on the Japanese Orthopedic Association scale and ambulated with a personalized skull-neck-thorax orthosis on postoperative day 11. She received radioiodine I therapy. The plane x-rays and computed tomography revealed no implant displacement or subsidence at the 12-month follow-up mark. CONCLUSION: The presented case substantiates the use of 3D printing technology, which enables the personalization of products to solve unconventional problems in spinal surgery. LEVEL OF EVIDENCE: 5.
