Upper cervical spine reconstruction using customized 3D-printed vertebral body in 9 patients with primary tumors involving C2

Coatless modification of 3D-printed Ti6Al4V implants through tailored Cu ion implantation combined with UV photofunctionalization to enhance cell attachment, osteogenesis and angiogenesis

The three-dimensional-printed Ti6Al4V implant (3DTi) has been widely accepted for the reconstruction of massive bone defects in orthopedics owing to several advantages, such as its tailored shape design, avoiding bone graft and superior bone-implant interlock. However, the osteoinduction activity of 3DTi is inadequate when applied clinically even though it exhibits osteoconduction. This study developes a comprehensive coatless strategy for the surface improvement of 3DTi through copper (Cu) ion implantation and ultraviolet (UV) photofunctionalization to enhance osteoinductivity. The newly constructed functional 3DTi (UV/Ti-Cu) achieved stable and controllable Cu doping, sustained Cu2+ releasing, and increased surface hydrophilicity. By performing cellular experiments, we determined that the safe dose range of Cu ion implantation was less than 5×1016 ions/cm2. The implanted Cu2+ enhanced the ALP activity and the apatite formation ability of bone marrow stromal cells (BMSCs) while slightly decreasing proliferation ability. When combined with UV photofunctionalization, cell adhesion and proliferation were significantly promoted and bone mineralization was further increased. Meanwhile, UV/Ti-Cu was conducive to the migration and angiogenesis of human umbilical vein endothelial cells (HUVECs) in vitro, theoretically facilitating vascular coupling osteogenesis. In conclusion, UV/Ti-Cu is a novel attempt to apply two coatless techniques for the surface modification of 3DTi. In addition, it is considered a potential bone substrate for repairing bone defects.

[Treatment of cervical ossification of posterior longitudinal ligament with titanium alloy trabecular bone three-dimensional printed artificial vertebral body]

Objective

To evaluate the effectiveness of using titanium alloy trabecular bone three-dimensional (3D) printed artificial vertebral body in treating cervical ossification of the posterior longitudinal ligament (OPLL).

Methods

A retrospective analysis was conducted on clinical data from 45 patients with cervical OPLL admitted between September 2019 and August 2021 and meeting the selection criteria. All patients underwent anterior cervical corpectomy and decompression, interbody bone graft fusion, and titanium plate internal fixation. During operation, 21 patients in the study group received titanium alloy trabecular bone 3D printed artificial vertebral bodies, while 24 patients in the control group received titanium cages. There was no significant difference in baseline data such as gender, age, disease duration, affected segments, or preoperative pain visual analogue scale (VAS) score, Japanese Orthopaedic Association (JOA) score, Neck Disability Index (NDI), vertebral height, and C 2-7Cobb angle ( P>0.05). Operation time, intraoperative blood loss, and occurrence of complications were recorded for both groups. Preoperatively and at 3 and 12 months postoperatively, the functionality and symptom relief were assessed using JOA scores, VAS scores, and NDI evaluations. The vertebral height and C 2-7 Cobb angle were detected by imaging examinations and the implant subsidence and intervertebral fusion were observed.

Results

The operation time and incidence of complications were significantly lower in the study group than in the control group ( P<0.05), while the difference in intraoperative blood loss between the two groups was not significant ( P>0.05). All patients were followed up 12-18 months, with the follow-up time of (14.28±4.34) months in the study group and (15.23±3.54) months in the control group, showing no significant difference ( t=0.809, P=0.423). The JOA score, VAS score, and NDI of the two groups improved after operation, and further improved at 12 months compared to 3 months, with significant differences ( P<0.05). At each time point, the study group exhibited significantly higher JOA scores and improvement rate compared to the control group ( P<0.05); but there was no significantly difference in VAS score and NDI between the two groups ( P>0.05). Imaging re-examination showed that the vertebral height and C 2-7Cobb angle of the two groups significantly increased at 3 and 12 months after operation ( P<0.05), and there was no significant difference between 3 and 12 months after operation ( P>0.05). At each time point, the vertebral height and C 2-7Cobb angle of the study group were significantly higher than those of the control group ( P<0.05), and the implant subsidence rate was significantly lower than that of the control group ( P<0.05). However, there was no significant difference in intervertebral fusion rate between the two groups ( P>0.05).

Conclusion

Compared to traditional titanium cages, the use of titanium alloy trabecular bone 3D-printed artificial vertebral bodies for treating cervical OPLL results in shorter operative time, fewer postoperative complications, and lower implant subsidence rates, making it superior in vertebral reconstruction.

An additively manufactured model for preclinical testing of cervical devices

Purpose

Composite models have become commonplace for the assessment of fixation and stability of total joint replacements; however, there are no comparable models for the cervical spine to evaluate fixation. The goal of this study was to create the framework for a tunable non-homogeneous model of cervical vertebral body by identifying the relationships between strength, in-fill density, and lattice structure and creating a final architectural framework for specific strengths to be applied to the model.

Methods

The range of material properties for cervical spine were identified from literature. Using additive manufacturing software, rectangular prints with three lattice structures, gyroid, triangle, zig-zag, and a range of in-fill densities were 3D-printed. The compressive and shear strengths for all combinations were calculated in the axial and coronal planes. Eleven unique vertebral regions were selected to represent the distribution of density. Each bone density was converted to strength and subsequently correlated to the lattice structure and in-fill density with the desired material properties. Finally, a complete cervical vertebra model was 3D-printed to ensure sufficient print quality.

Results

Materials testing identified a relationship between in-fill densities and strength for all lattice structures. The axial compressive strength of the gyroid specimens ranged from 1.5 MPa at 10% infill to 31.3 MPa at 100% infill and the triangle structure ranged from 2.7 MPa at 10% infill to 58.4 MPa at 100% infill. Based on these results, a cervical vertebra model was created utilizing cervical cancellous strength values and the corresponding in-fill density and lattice structure combination. This model was then printed with 11 different in-fill densities ranging from 33% gyroid to 84% triangle to ensure successful integration of the non-homogeneous in-fill densities and lattice structures.

Conclusions

The findings from this study introduced a framework for using additive manufacturing to create a tunable, customizable biomimetic model of a cervical vertebra.

Simvastatin/hydrogel-loaded 3D-printed titanium alloy scaffolds suppress osteosarcoma via TF/NOX2-associated ferroptosis while repairing bone defects

Postoperative anatomical reconstruction and prevention of local recurrence after tumor resection are two vital clinical challenges in osteosarcoma treatment. A three-dimensional (3D)-printed porous Ti6Al4V scaffold (3DTi) is an ideal material for reconstructing critical bone defects with numerous advantages over traditional implants, including a lower elasticity modulus, stronger bone-implant interlock, and larger drug-loading space. Simvastatin is a multitarget drug with anti-tumor and osteogenic potential; however, its efficiency is unsatisfactory when delivered systematically. Here, simvastatin was loaded into a 3DTi using a thermosensitive poly (lactic-co-glycolic) acid (PLGA)-polyethylene glycol (PEG)-PLGA hydrogel as a carrier to exert anti-osteosarcoma and osteogenic effects. Newly constructed simvastatin/hydrogel-loaded 3DTi (Sim-3DTi) was comprehensively appraised, and its newfound anti-osteosarcoma mechanism was explained. Specifically, in a bone defect model of rabbit condyles, Sim-3DTi exhibited enhanced osteogenesis, bone in-growth, and osseointegration compared with 3DTi alone, with greater bone morphogenetic protein 2 expression. In our nude mice model, simvastatin loading reduced tumor volume by 59%-77 % without organic damage, implying good anti-osteosarcoma activity and biosafety. Furthermore, Sim-3DTi induced ferroptosis by upregulating transferrin and nicotinamide adenine dinucleotide phosphate oxidase 2 levels in osteosarcoma both in vivo and in vitro. Sim-3DTi is a promising osteogenic bone substitute for osteosarcoma-related bone defects, with a ferroptosis-mediated anti-osteosarcoma effect.

Customized 3-dimensional-printed Vertebral Implants for Spinal Reconstruction After Tumor Resection: A Systematic Review

STUDY DESIGN

Systematic review.

OBJECTIVE

To examine the outcomes of customized 3-dimensional (3D) printed implants for spinal reconstruction after tumor resection.

SUMMARY OF BACKGROUND DATA

Various techniques exist for spinal reconstruction after tumor resection. Currently, there is no consensus regarding the utility of customized 3D-printed implants for spinal reconstruction after tumor resection.

MATERIALS AND METHODS

A systematic review was registered with PROSPERO and performed according to "Preferred Reporting Items for Systematic Reviews and Meta-analyses" guidelines. All level I-V evidence studies reporting the use of 3D-printed implants for spinal reconstruction after tumor resection were included.

RESULTS

Eleven studies (65 patients; mean age, 40.9 ± 18.1 y) were included. Eleven patients (16.9%) underwent intralesional resections with positive margins and 54 patients (83.1%) underwent en bloc spondylectomy with negative margins. All patients underwent vertebral reconstruction with 3D-printed titanium implants. Tumor involvement was in the cervical spine in 21 patients (32.3%), thoracic spine in 29 patients (44.6%), thoracolumbar junction in 2 patients (3.1%), and lumbar spine in 13 patients (20.0%). Ten studies with 62 patients reported perioperative outcomes radiologic/oncologic status at final follow-up. At the mean final follow-up of 18.5 ± 9.8 months, 47 patients (75.8%) had no evidence of disease, 9 patients (14.5%) were alive with recurrence, and 6 patients (9.7%) had died of disease. One patient who underwent C3-C5 en bloc spondylectomy had an asymptomatic subsidence of 2.7 mm at the final follow-up. Twenty patients that underwent thoracic and/or lumbar reconstruction had a mean subsidence of 3.8 ± 4.7 mm at the final follow-up; however, only 1 patient had a symptomatic subsidence that required revision surgery. Eleven patients (17.7%) had one or more major complications.

CONCLUSION

There is some evidence to suggest that using customized 3D-printed titanium or titanium alloy implants is an effective technique for spinal reconstruction after tumor resection. There is a high incidence of asymptomatic subsidence and major complications that are similar to other methods of reconstruction.

LEVEL OF EVIDENCE

Level V, systematic review of level I-V studies.

Technical aspects of total spondylectomy of C2

BACKGROUND

Tumorous involvement of the second cervical vertebra is an infrequent, but severe disease. Primary tumors and solitary metastases can be addressed by a radical procedure, a complete removal of the whole compartment. The second cervical vertebra has a highly complex anatomy, and its operation requires considerable surgical skills. The aim of this retrospective study is to present technical aspects of complete resection of C2 for tumor indications, clinical and radiological evaluation of our group of patients and comparison of results of recent reports on surgery in this region in the literature.

METHODS

Between 2006 and 2019 we performed 10 total resections of C2 for primary bone tumor or solitary metastasis at our department. Operation was indicated for chordoma in 4 cases and for other diagnoses (plasmacytoma, EWSA, metastases of papillary thyroid carcinoma, medullary thyroid carcinoma, lung carcinoma and sinonasal carcinoma) in one case each. The operative procedure was in all cases performed in two steps. It always started with the posterior approach. The anterior procedure was scheduled according to the patient's condition after an average interval of 16.9 days (range 7-21).

RESULTS

A stable upper cervical spine was achieved in all patients. A solid bone fusion over the whole instrumentation was present in all living patients and they returned to their preoperative activity level. By the final follow-up 6 patients died: one patient died on the 5th postop day because of diffuse uncontrollable bleeding from surgical wound, three patients died of generalization of the underlying disease and two patients due to complications associated with local recurrence of the disease. In addition to regular follow-ups, the surviving patients (N.=4) were also examined upon completion of the study, i.e., on average 91 months (range 17-179 months) postoperatively. With exclusion of an early deceased patient, the average follow-up period of deceased patients was 34.6 months (range 9-55) (N.=5). The average follow-up of the whole group of patients was 59,7 months (N.=9).

CONCLUSIONS

Total spondylectomy of C2 is an exceptional surgical procedure associated with risk of serious complications but offers chance for a complete recovery of the patient. Defining indications accurately, especially in solitary metastases, is very difficult even with current level of imaging and other testing. The quality of life of long-term surviving patients in our study was not significantly impacted.

Cervical spine reconstruction after total vertebrectomy using customized three-dimensional-printed implants in dogs

BACKGROUND

Sufficient surgical resection is necessary for effective tumor control, but is usually limited for vertebral tumors, especially in the cervical spine in small animal neurosurgery.

OBJECTIVE

To evaluate the primary stability and safety of customized three-dimensional (3D)-printed implants for cervical spine reconstruction after total vertebrectomy.

METHODS

Customized guides and implants were designed based on computed tomography (CT) imaging of five beagle cadavers and were 3D-printed. They were used to reconstruct C5 after total vertebrectomy. Postoperative CT images were obtained to evaluate the safety and accuracy of screw positioning. After harvesting 10 vertebral specimens (C3-C7) from intact (group A) and implanted spines (group B), implant stability was analyzed using a 4-point bending test comparing with groups A and C (reconstituted with plate and pins/polymethylmethacrylate after testing in Group A).

RESULTS

All customized implants were applied without gross neurovascular damage. In addition, 90% of the screws were in a safe area, with 7.5% in grade 1 (< 1.3 mm) and 2.5% in grade 2 (> 1.3 mm). The mean entry point and angular deviations were 0.81 ± 0.43 mm and 6.50 ± 5.11°, respectively. Groups B and C significantly decreased the range of motion (ROM) in C3-C7 compared with intact spines (p = 0.033, and 0.018). Both groups reduced overall ROM and neutral zone in C4-C6, but only group B showed significance (p = 0.005, and 0.027).

CONCLUSION

Customized 3D-printed implants could safely and accurately replace a cervical vertebra in dog cadavers while providing primary stability.

Novelties for increased safety in cranio-vertebral surgery: a review

The cranio-vertebral junction (CVJ) was formerly considered a surgical "no man's land" due to its complex anatomical and biomechanical features. Surgical approaches and hardware instrumentation have had to be tailored in order to achieve successful outcomes. Nowadays, thanks to the ongoing development of new technologies and surgical techniques, CVJ surgery has come to be widely performed in many spine centers. Accordingly, there is a drive to explore novel solutions and technological nuances that make CVJ surgery safer, faster, and more precise. Improved outcome in CVJ surgery has been achieved thanks to increased safety allowing for reduction in complication rates. The Authors present the latest technological advancements in CVJ surgery in terms of imaging, biomaterials, navigation, robotics, customized implants, 3D-printed technology, video-assisted approaches and neuromonitoring.

Surgical Treatment of Spinal Metastatic Pheochromocytoma and Paraganglioma: A Single Institutional Cohort of 18 Patients

STUDY DESIGN

Retrospective Cohort Study.

OBJECTIVES

To describe surgeries and treatment outcomes of metastatic pheochromocytomas and paragangliomas (PPGLs) on the spine.

METHODS

We reviewed a cohort of 18 patients with spinal PPGLs who were consecutively treated in our spinal center. Their clinical data was reviewed. The survival period and its relevant factors was then analyzed.

RESULTS

The cohort included ten cases of pheochromocytomas and eight paragangliomas. The local pain and neurological deficits were the two most common symptoms. One third of the spinal PPGLs were diagnosed as functional tumors, arousing secondary hypertension. The imaging features were consistent with those of osteolytic lesions. The surgical strategies for the cohort included percutaneous vertebroplasty, neurological decompression and partial tumor resection, and total en-bloc resection. The postoperative courses were uneventful except 1 patient developed heart failure. The adjuvant therapies were implemented in 6 patients with 131I-MIBG, five with radiotherapy, two with chemotherapy, and 1 with target therapy. The median survival period was 39 months, and the overall survival rate of 1 year was 77.8% (14/18). The patients' Karnofsky performance scores were positively correlated with the survival period (P < .05).

CONCLUSION

Surgery is indicated for intractable local pain and neurological impairment in the patients with spinal PPGLs. Palliative surgical strategies, including neurological decompression and partial tumor resection, could bring fair outcomes, especially for the patients in poor physical conditions.

3D printing metal implants in orthopedic surgery: Methods, applications and future prospects

Background

Currently, metal implants are widely used in orthopedic surgeries, including fracture fixation, spinal fusion, joint replacement, and bone tumor defect repair. However, conventional implants are difficult to be customized according to the recipient's skeletal anatomy and defect characteristics, leading to difficulties in meeting the individual needs of patients. Additive manufacturing (AM) or three-dimensional (3D) printing technology, an advanced digital fabrication technique capable of producing components with complex and precise structures, offers opportunities for personalization.

Methods

We systematically reviewed the literature on 3D printing orthopedic metal implants over the past 10 years. Relevant animal, cellular, and clinical studies were searched in PubMed and Web of Science. In this paper, we introduce the 3D printing method and the characteristics of biometals and summarize the properties of 3D printing metal implants and their clinical applications in orthopedic surgery. On this basis, we discuss potential possibilities for further generalization and improvement.

Results

3D printing technology has facilitated the use of metal implants in different orthopedic procedures. By combining medical images from techniques such as CT and MRI, 3D printing technology allows the precise fabrication of complex metal implants based on the anatomy of the injured tissue. Such patient-specific implants not only reduce excessive mechanical strength and eliminate stress-shielding effects, but also improve biocompatibility and functionality, increase cell and nutrient permeability, and promote angiogenesis and bone growth. In addition, 3D printing technology has the advantages of low cost, fast manufacturing cycles, and high reproducibility, which can shorten patients' surgery and hospitalization time. Many clinical trials have been conducted using customized implants. However, the use of modeling software, the operation of printing equipment, the high demand for metal implant materials, and the lack of guidance from relevant laws and regulations have limited its further application.

Conclusions

There are advantages of 3D printing metal implants in orthopedic applications such as personalization, promotion of osseointegration, short production cycle, and high material utilization. With the continuous learning of modeling software by surgeons, the improvement of 3D printing technology, the development of metal materials that better meet clinical needs, and the improvement of laws and regulations, 3D printing metal implants can be applied to more orthopedic surgeries.

The translational potential of this paper

Precision, intelligence, and personalization are the future direction of orthopedics. It is reasonable to believe that 3D printing technology will be more deeply integrated with artificial intelligence, 4D printing, and big data to play a greater role in orthopedic metal implants and eventually become an important part of the digital economy. We aim to summarize the latest developments in 3D printing metal implants for engineers and surgeons to design implants that more closely mimic the morphology and function of native bone.

3D-printed Titanium Prosthetic Reconstruction of Unilateral Bone Deficiency After Surgical Resection of Tumor Lesions in the Upper Cervical Spine: Clinical Outcomes of Three Consecutive Cases and Narrative Review

MAIN POINTS

Operational excision of tumor lesions in the upper cervical spine remains a tremendous challenge to surgeons due to the local complex anatomic relationships. Meanwhile, no commercially available device has been specially designed to address bone deficiency after surgical resection. Here, we described the reconstruction of unilateral bone deficiency after surgical resection of a giant cell tumor of the tendon sheath originating from the lateral atlantoaxial joint with the employment of a 3D printing technique and reviewed the relevant literature. In our study, 3 patients with giant cell tumor of the tendon sheath in the upper cervical spine achieved complete tumor removal, and received unilateral bone reconstruction with one-armed 3D-printed titanium prosthesis. During the follow-up, these patients remained neurologically intact and got back to a normal life without wearing the braces. Images demonstrated the satisfactory placement of 3D-printed prosthesis with no failure of fixation and no subsidence. In addition, 6 articles describing the employment of 3D-printed prostheses or models for tumor surgery in the upper cervical spine were reviewed, and satisfactory clinical outcomes were reported in these studies. Hence, 3D-printed titanium prosthetic reconstruction of bone deficiency in the upper cervical spine was a safe and effective technique.

LEVEL OF EVIDENCE

Level IV.

A Systematic Review of Perioperative Complications in en Bloc Resection for Spinal Tumors

STUDY DESIGN

Systematic review.

OBJECTIVE

En bloc resection is a major, invasive surgical procedure designed to completely resect a vertebral tumor with a sufficient margin. It is technically demanding and potentially poses risks of perioperative complications. In this systematic review, we investigated the incidence of complications after en bloc resection for spinal tumors.

METHODS

We screened PubMed and Embase databases for relevant English publications, from 1980 to 2020, using the following terms: spine OR spinal AND en bloc AND tumor. Using a standard PRISMA template, after the initial screening, full-text articles of interest were evaluated.

RESULTS

Thirty-six studies with 961 patients were included. The overall mean age of patients was 49.6 years, and the mean follow-up time was 33.5 months. There were 560 complications, and an overall complication rate of 58.3% (560/961). The 5 most frequent complications were neurological damage (12.7%), hardware failure (12.1%), dural tear and cerebrospinal fluid leakage (10.6%), wound-related complications (7.6%) and vascular injury and bleeding (7.3%). The complication-related revision rate was 10.7% (103/961). The average incidence of complication-related death was 1.2% (12/961).

CONCLUSIONS

En bloc resection is a surgical procedure that is very invasive and technically challenging, and the possible risks of perioperative complications should not be neglected. The overall complication rate is high. However, complication-related death was rare. The advantages of surgery should be weighed against the serious perioperative morbidity associated with this technique.

[3D-printed vertebral body in anterior spinal reconstruction after total spondylectomy for patients with cervical chordoma]

OBJECTIVE

To investigate whether 3D-printed artificial vertebral body can reduce prosthesis subsidence rate for patients with cervical chordomas, through comparing the rates of prosthesis subsidence between 3D printing artificial vertebral body and titanium mesh for anterior spinal reconstruction after total spondylectomy.

METHODS

This was a retrospective analysis of patients who underwent surgical treatment for cervical chordoma at our hospital from March 2005 to September 2019. There were nine patients in the group of 3D artificial vertebral body (3D group), and 15 patients in the group of titanium mesh cage (Mesh group). The patients' characteristics and treatment data were extracted from the medical records, including age, gender, CT hounsfield unit of cervical vertebra and surgical information, such as the surgical segments, time and blood loss of surgery, frequency and degree of prosthesis subsidence after surgery. Radiographic observations of prosthesis subsidence during the follow-up, including X-rays, CT, and magnetic resonance imaging were also collected. SPSS 22.0 was used to analysis the data.

RESULTS

There was no significant difference between the two groups in gender, age, CT hounsfield unit, surgical segments, time of surgery, blood loss of posterior surgery and total blood loss. Blood loss of anterior surgery was 700 (300, 825) mL in 3D group and 1 500 (750, 2 800) mL in Mesh group (P < 0.05). The prosthesis subsidence during the follow-up, 3 months after surgery, there was significant difference between the two groups in mild prosthesis subsidence (P < 0.05). The vertebral height of the 3D group decreased less than 1 mm in eight cases (no prosthesis subsidence) and more than 1 mm in one case (mild prosthesis subsidence). The vertebral height of the Mesh group decreased less than 1 mm in five cases (no prosthesis subsidence), and more than 1 mm in eight cases (mild prosthesis subsidence). Two patients did not have X-rays in 3 months after surgery. There was a statistically significant difference between the two groups in the prosthesis subsidence rate at the end of 12 months (P < 0.01). The vertebral height of eight cases in the 3D group decreased less than 1 mm (no prosthesis subsidence) and one case more than 3 mm (severe prosthesis subsidence). Four of the 15 cases in the Mesh group decreased less than 1 mm (no prosthesis subsidence), two cases more than 1 mm (mild prosthesis subsidence), and nine cases more than 3 mm (severe prosthesis subsidence). There was a statistically significant difference between the two groups in the prosthesis subsidence rate at the end of 24 months (P < 0.01). The vertebral height of seven cases in the 3D group decreased less than 1 mm (no prosthesis subsidence), one case more than 3 mm (severe prosthesis subsidence), and one case died with tumor. One case in the Mesh group decreased less than 1 mm (no prosthesis subsidence), one case more than 1 mm (mild prosthesis subsidence), 11 case more than 3 mm (severe prosthesis subsidence), one case died with tumor and one lost the follow-up. Moreover, at the end of 12 months and 24 months, there was significant difference between the two groups in severe prosthesis subsidence rate (P < 0.01).

CONCLUSION

3D-printed artificial vertebral body for anterior spinal reconstruction after total spondylectomy for patients with cervical chordoma can provide reliable spinal stability, and reduce the incidence of prosthesis subsidence after 2-year follow-up.

[3D-printed vertebral body in anterior spinal reconstruction after total spondylectomy for patients with cervical chordoma]

OBJECTIVE

To investigate whether 3D-printed artificial vertebral body can reduce prosthesis subsidence rate for patients with cervical chordomas, through comparing the rates of prosthesis subsidence between 3D printing artificial vertebral body and titanium mesh for anterior spinal reconstruction after total spondylectomy.

METHODS

This was a retrospective analysis of patients who underwent surgical treatment for cervical chordoma at our hospital from March 2005 to September 2019. There were nine patients in the group of 3D artificial vertebral body (3D group), and 15 patients in the group of titanium mesh cage (Mesh group). The patients' characteristics and treatment data were extracted from the medical records, including age, gender, CT hounsfield unit of cervical vertebra and surgical information, such as the surgical segments, time and blood loss of surgery, frequency and degree of prosthesis subsidence after surgery. Radiographic observations of prosthesis subsidence during the follow-up, including X-rays, CT, and magnetic resonance imaging were also collected. SPSS 22.0 was used to analysis the data.

RESULTS

There was no significant difference between the two groups in gender, age, CT hounsfield unit, surgical segments, time of surgery, blood loss of posterior surgery and total blood loss. Blood loss of anterior surgery was 700 (300, 825) mL in 3D group and 1 500 (750, 2 800) mL in Mesh group (P < 0.05). The prosthesis subsidence during the follow-up, 3 months after surgery, there was significant difference between the two groups in mild prosthesis subsidence (P < 0.05). The vertebral height of the 3D group decreased less than 1 mm in eight cases (no prosthesis subsidence) and more than 1 mm in one case (mild prosthesis subsidence). The vertebral height of the Mesh group decreased less than 1 mm in five cases (no prosthesis subsidence), and more than 1 mm in eight cases (mild prosthesis subsidence). Two patients did not have X-rays in 3 months after surgery. There was a statistically significant difference between the two groups in the prosthesis subsidence rate at the end of 12 months (P < 0.01). The vertebral height of eight cases in the 3D group decreased less than 1 mm (no prosthesis subsidence) and one case more than 3 mm (severe prosthesis subsidence). Four of the 15 cases in the Mesh group decreased less than 1 mm (no prosthesis subsidence), two cases more than 1 mm (mild prosthesis subsidence), and nine cases more than 3 mm (severe prosthesis subsidence). There was a statistically significant difference between the two groups in the prosthesis subsidence rate at the end of 24 months (P < 0.01). The vertebral height of seven cases in the 3D group decreased less than 1 mm (no prosthesis subsidence), one case more than 3 mm (severe prosthesis subsidence), and one case died with tumor. One case in the Mesh group decreased less than 1 mm (no prosthesis subsidence), one case more than 1 mm (mild prosthesis subsidence), 11 case more than 3 mm (severe prosthesis subsidence), one case died with tumor and one lost the follow-up. Moreover, at the end of 12 months and 24 months, there was significant difference between the two groups in severe prosthesis subsidence rate (P < 0.01).

CONCLUSION

3D-printed artificial vertebral body for anterior spinal reconstruction after total spondylectomy for patients with cervical chordoma can provide reliable spinal stability, and reduce the incidence of prosthesis subsidence after 2-year follow-up.

Treatment of spinal rhabdomyosarcoma in adults: A case report and literature review of current evidence

Spinal rhabdomyosarcoma (RMS) is a rare yet highly malignant tumor in adults. Literature on this entity is lacking and no mature treatment guideline is currently available. The treatment arsenals include surgery, radiotherapy and chemotherapy, being used singly or jointly. However, the prognosis is dismal, with a mean overall survival period of 10 months. Thus, any case of this disease with encouraging outcomes shall be shared. A case of a middle-aged female patient with spinal RMS was presented in the current report. The patient suffered from back pain but was neurologically intact. The patient underwent a total en-bloc spondylectomy of the T11-L2 vertebrae and spinal reconstruction with 3D-printed prosthetic vertebrae. Afterwards, the patient received a rigid schedule of stereotactic body radiotherapy (SBRT) and chemotherapy. To date, the patient has survived for 40 months, with the preservation of neurological function and sustained mitigation of local pain after the operation. The patient suffered subcutaneous colonization of tumor cells and pulmonary metastasis 10 months postoperatively, but obtained a long locoregional control of 19 months. In conclusion, total en-bloc lesion resection is indicated for the treatment of isolated, primary spinal RMS in adults. Some authors reported that the usage of new surgical tools and instruments has facilitated surgery, which was previously invasive and technically challenging. Advanced radiotherapy techniques, such as SBRT, which were proven effective for local lesion control, should be implemented early after the operation. Chemotherapy remains the mainstay of treatment, but further research and evidence for the efficacy of regimens specifically for adults are required.

Complex geometry and integrated macro-porosity: Clinical applications of electron beam melting to fabricate bespoke bone-anchored implants

The last decade has witnessed rapid advancements in manufacturing technologies for biomedical implants. Additive manufacturing (or 3D printing) has broken down major barriers in the way of producing complex 3D geometries. Electron beam melting (EBM) is one such 3D printing process applicable to metals and alloys. EBM offers build rates up to two orders of magnitude greater than comparable laser-based technologies and a high vacuum environment to prevent accumulation of trace elements. These features make EBM particularly advantageous for materials susceptible to spontaneous oxidation and nitrogen pick-up when exposed to air (e.g., titanium and titanium-based alloys). For skeletal reconstruction(s), anatomical mimickry and integrated macro-porous architecture to facilitate bone ingrowth are undoubtedly the key features of EBM manufactured implants. Using finite element modelling of physiological loading conditions, the design of a prosthesis may be further personalised. This review looks at the many unique clinical applications of EBM in skeletal repair and the ground-breaking innovations in prosthetic rehabilitation. From a simple acetabular cup to the fifth toe, from the hand-wrist complex to the shoulder, and from vertebral replacement to cranio-maxillofacial reconstruction, EBM has experienced it all. While sternocostal reconstructions might be rare, the repair of long bones using EBM manufactured implants is becoming exceedingly frequent. Despite the various merits, several challenges remain yet untackled. Nevertheless, with the capability to produce osseointegrating implants of any conceivable shape/size, and permissive of bone ingrowth and functional loading, EBM can pave the way for numerous fascinating and novel applications in skeletal repair, regeneration, and rehabilitation. STATEMENT OF SIGNIFICANCE: Electron beam melting (EBM) offers unparalleled possibilities in producing contaminant-free, complex and intricate geometries from alloys of biomedical interest, including Ti6Al4V and CoCr. We review the diverse range of clinical applications of EBM in skeletal repair, both as mass produced off-the-shelf implants and personalised, patient-specific prostheses. From replacing large volumes of disease-affected bone to complex, multi-material reconstructions, almost every part of the human skeleton has been replaced with an EBM manufactured analog to achieve macroscopic anatomical-mimickry. However, various questions regarding long-term performance of patient-specific implants remain unaddressed. Directions for further development include designing personalised implants and prostheses based on simulated loading conditions and accounting for trabecular bone microstructure with respect to physiological factors such as patient's age and disease status.

Reconstruction after resection of C2 vertebral tumors: A comparative study of 3D-printed vertebral body versus titanium mesh

Background

Surgical resection of C2 vertebral tumors is challenging owing to the complex anatomy of C2 vertebrae and the challenges to surgical exposure. Various surgical approaches are available, but some are associated with excessively high risks of complications. An additional challenge is reconstruction of the upper cervical spine following surgery. In the last decade, additive-manufacturing personalized artificial vertebral bodies (AVBs) have been introduced for the repair of large, irregular bony defects; however, their use and efficacy in upper cervical surgery have not been well addressed. Therefore, in this study, we compared instrumented fixation status between patients who underwent conventional titanium mesh reconstruction and those who underwent the same resection but with personalized AVBs.

Methods

We performed a retrospective comparative study and recruited a single-institution cohort of patients with C2 vertebral tumors. Clinical data and imaging findings were reviewed. Through data processing and comparative analysis, we described and discussed the feasibility and safety of surgical resection and the outcomes of hardware implants. The primary outcome of this study was instrumented fixation status.

Results

The 31 recruited patients were divided into two groups. There were 13 patients in group A who underwent conventional titanium mesh reconstruction and 18 group B patients who underwent personalized AVBs. All patients underwent staged posterior and anterior surgical procedures. In the cohort, 9.7% achieved total en bloc resection of the tumor, while gross total resection was achieved in the remaining 90.3%. The perioperative complication and mortality rates were 45.2% and 6.5%, respectively. The occurrence of perioperative complications was related to the choice of anterior approach (p < 0.05). Group A had a higher complication rate than group B (p < 0.05). Four patients (4/13, 30.8%) developed hardware problems during the follow-up period; however, this rate was marginally higher than that of group B (1/18, 5.6%).

Conclusions

Total resection of C2 vertebral tumors was associated with a high risk of perioperative complications. The staged posterior and retropharyngeal approaches are better surgical strategies for C2 tumors. Personalized AVBs can provide a reliable reconstruction outcome, yet minor pitfalls remain that call for further modification.

[Application and research progress of three-dimentional printed porous titanium alloy after tumor resection]

Objective

To review the current research and application progress of three-dimentional (3D) printed porous titanium alloy after tumor resection, and provide direction and reference for the follow-up clinical application and basic research of 3D printed porous titanium alloy.

Methods

The related literature on research and application of 3D printed porous titanium alloy after tumor resection in recent years was reviewed from three aspects: performance of simple 3D printed porous titanium alloy, application analysis of simple 3D printed porous titanium alloy after tumor resection, and research progress of anti-tumor 3D printed porous titanium alloy.

Results

3D printing technology can adjust the pore parameters of porous titanium alloy, so that it has the same biomechanical properties as bone. Appropriate pore parameters are conducive to inducing bone growth, promoting the recovery of skeletal system and related functions, and improving the quality of life of patients after operation. Simple 3D printed porous titanium alloy can more accurately match the bone defect after tumor resection through preoperative personalized design, so that it can closely fit the surgical margin after tumor resection, and improve the accuracy and efficiency of the operation. The early and mid-term follow-up results show that its application reduces the postoperative complications such as implant loosening, subsidence, fracture and so on, and enhances the bone stability. The anti-tumor performance of 3D printed porous titanium alloy mainly includes coating and drug-loading treatment of pure 3D printed porous titanium alloy, and some progress has been made in the basic research stage.

Conclusion

Simple 3D printed porous titanium alloy is suitable for patients with large and complex bone defects after tumor resection, and the anti-tumor effect of 3D printed porous titanium alloy can be achieved through coating and drug delivery.

Current and Emerging Approaches for Spine Tumor Treatment

Spine tumors represent a significant social and medical problem, affecting the quality of life of thousands of patients and imposing a burden on healthcare systems worldwide. Encompassing a wide range of diseases, spine tumors require prompt multidisciplinary treatment strategies, being mainly approached through chemotherapy, radiotherapy, and surgical interventions, either alone or in various combinations. However, these conventional tactics exhibit a series of drawbacks (e.g., multidrug resistance, tumor recurrence, systemic adverse effects, invasiveness, formation of large bone defects) which limit their application and efficacy. Therefore, recent research focused on finding better treatment alternatives by utilizing modern technologies to overcome the challenges associated with conventional treatments. In this context, the present paper aims to describe the types of spine tumors and the most common current treatment alternatives, further detailing the recent developments in anticancer nanoformulations, personalized implants, and enhanced surgical techniques.

3D printing in spine care: A review of current applications

3D printing (3DP) has been brought to medical use since the early part of this century- but it has been widely researched on and publicized only in the last few years. Amongst patients with spinal disorders, 3DP has been utilized in various facets of patient care. These include pre-operative aspects - such as patient education, resident training, pre-operative planning and simulations, intra-operative assistance in the form of customized jigs for pedicle screw insertion, patient specific interbody cages and vertebral body substitutes in complex malignancies and spinal infections. It has also been utilized in deformity surgeries and has opened new avenues in minimally invasive spine care. Guidelines have now been drafted by various organizations including the FDA with a prime focus on quality control measures applicable to this new technology. There has been a recent surge in publications supporting the use of 3DP in spinal disorders, reporting an improvement in various aspects of patient care. As the technology spreads out its wings further, more innovations and applications are expected to unfold in the coming years. Considering the rapid advances that 3DP has made, having a basic understanding of this technology is imperative for all spine surgeons. Despite promising preliminary results, there still exist a few pitfalls of the technology which have hindered the universal application of 3DP. Most importantly, there is a dearth of data related to long term outcomes supporting its clinical use. The prohibitive cost of 3D models, the specialized manpower it necessitates and the need for specific instrumentation are major deterrents to widespread use of this technology, particularly in small-scale healthcare setups. With further advancements in technology, the goal must be to make it more accurate and affordable to hospitals and patients so that the benefits of the technology can reach a wider patient population.

3D-printed vertebral body for anterior spinal reconstruction in patients with thoracolumbar spinal tumors

OBJECTIVE

A 3D-printed vertebral prosthesis can be used to reconstruct a bone defect more precisely because of its tailored shape, with its innermost porous structure inducing bone ingrowth. The aim of this study was to evaluate the clinical outcomes of using a 3D-printed artificial vertebral body for spinal reconstruction after en bloc resection of thoracolumbar tumors.

METHODS

This was a retrospective analysis of 23 consecutive patients who underwent surgical treatment for thoracolumbar tumors at our hospital. En bloc resection was performed in all cases, based on the Weinstein-Boriani-Biagini surgical staging system, and anterior reconstruction was performed using a 3D-printed artificial vertebral body. Prosthesis subsidence, fusion status, and instrumentation-related complications were evaluated. Stability of the anterior reconstruction method was evaluated by CT, and CT Hounsfield unit (HU) values were measured to evaluate fusion status.

RESULTS

The median follow-up was 37 (range 24-58) months. A customized 3D-printed artificial vertebral body was used in 10 patients, with an off-the-shelf 3D-printed artificial vertebral body used in the other 13 patients. The artificial vertebral body was implanted anteriorly in 5 patients and posteriorly in 18 patients. The overall fusion rate was 87.0%. The average prosthesis subsidence at the final follow-up was 1.60 ± 1.79 mm. Instrument failure occurred in 2 patients, both of whom had substantial subsidence (8.47 and 3.69 mm, respectively). At 3 months, 6 months, and 1 year postoperatively, the mean CT HU values within the artificial vertebral body were 1930 ± 294, 1997 ± 336, and 1994 ± 257, respectively, with each of these values being significantly higher than the immediate postoperative value of 1744 ± 321 (p < 0.05).

CONCLUSIONS

The use of a 3D-printed artificial vertebral body for anterior reconstruction after en bloc resection of the thoracolumbar spinal tumor may be a feasible and reliable option. The low incidence of prosthesis subsidence of 3D-printed endoprostheses can provide good stability instantly. Measurement of HU values with CT is a valuable method to evaluate the osseointegration at the bone-metal interface of a 3D-printed vertebral prosthesis.

3D printing applications in spine surgery: an evidence-based assessment toward personalized patient care

PURPOSE

Spine surgery entails a wide spectrum of complicated pathologies. Over the years, numerous assistive tools have been introduced to the modern neurosurgeon's armamentarium including neuronavigation and visualization technologies. In this review, we aimed to summarize the available data on 3D printing applications in spine surgery as well as an assessment of the future implications of 3D printing.

METHODS

We performed a comprehensive review of the literature on 3D printing applications in spine surgery.

RESULTS

Over the past decade, 3D printing and additive manufacturing applications, which allow for increased precision and customizability, have gained significant traction, particularly spine surgery. 3D printing applications in spine surgery were initially limited to preoperative visualization, as 3D printing had been primarily used to produce preoperative models of patient-specific deformities or spinal tumors. More recently, 3D printing has been used intraoperatively in the form of 3D customizable implants and personalized screw guides.

CONCLUSIONS

Despite promising preliminary results, the applications of 3D printing are so recent that the available data regarding these new technologies in spine surgery remains scarce, especially data related to long-term outcomes.

Patient-Tailored 3D-Printing Models in the Subspecialty Training of Spinal Tumors: A Comparative Study and Questionnaire Survey

BACKGROUND

Training in the subspecialty of spinal tumors is challenging and less researched. The anatomic variations and complex relationship with paraspinal structures tend to be the main obstacle for the trainees in this field. Three-dimensional (3D)-printing technique has the advantage of individual customization and high fidelity, and can produce case-tailored models as auxiliary tools in medical training.

METHODS

The main parts of the study included case-based lectures with tailored 3D-printing models, evaluating their performances in a controlled examination and anonymous questionnaire survey regarding the trainees' opinion towards the tailored models. The examination was designed as case-based clinical analysis. All trainees were randomly allocated to the study group and control group, and the former group was additively provided a case-tailored model.

RESULTS

Thirty-six participants were recruited in this study, including 16 residents and 20 fellows. In the section of examination, there was significant difference in the aspects of describing the involvement of paraspinal structures and discriminating the relationship between the tumor and large vessels (P < 0.05), but similar in the aspects of surgical planning and relevant complications (P > 0.05). In the survey, most participants gave favorable responses to 3D-printing models in the aspects of understanding anatomic structures and relationship, inter-trainee communication, surgical planning, and enhancement of interest and confidence (50.0% to 94.4%, respectively).

CONCLUSIONS

The 3D-printing model is a valuable tool in the training of new residents and fellows in the subspecialty of spinal tumors. It can facilitate the trainees' understanding of tumor anatomy, surgical readiness, and confidence as well.

The Role of 3D-Printed Custom-Made Vertebral Body Implants in the Treatment of Spinal Tumors: A Systematic Review

In spinal surgery, 3D prothesis represents a useful instrument for spinal reconstruction after the removal of spinal tumors that require an “en bloc” resection. This represents a complex and demanding procedure, aiming to restore spinal length, alignment and weight-bearing capacity and to provide immediate stability. Thus, in this systematic review the authors searched the literature to investigate and discuss the advantages and limitations of using 3D-printed custom-made vertebral bodies in the treatment of spinal tumors. A systematic literature review was conducted following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement, with no limits in terms of date of publication. The collected studies were exported to Mendeley. The articles were selected according to the following inclusion criteria: availability of full articles, full articles in English, studies regarding the implant of 3D custom-made prothesis after total or partial vertebral resection, studies regarding patients with a histologically confirmed diagnosis of primary spinal tumor or solitary bone metastasis; studies evaluating the implant of 3d custom-made prothesis in the cervical, thoracic, and lumbar spine. Nineteen published studies were included in this literature review, and include a total of 87 patients, 49 males (56.3%) and 38 females (43.7%). The main tumoral location and primary tumor diagnosis were evaluated. The 3D custom-made prothesis represents a feasible tool after tumor en-bloc resection in spinal reconstruction. This procedure is still evolving, and long-term follow-ups are mandatory to assess its safeness and usefulness.

Addressing the Needs of the Rapidly Aging Society through the Development of Multifunctional Bioactive Coatings for Orthopedic Applications

The unprecedented aging of the world's population will boost the need for orthopedic implants and expose their current limitations to a greater extent due to the medical complexity of elderly patients and longer indwelling times of the implanted materials. Biocompatible metals with multifunctional bioactive coatings promise to provide the means for the controlled and tailorable release of different medications for patient-specific treatment while prolonging the material's lifespan and thus improving the surgical outcome. The objective of this work is to provide a review of several groups of biocompatible materials that might be utilized as constituents for the development of multifunctional bioactive coatings on metal materials with a focus on antimicrobial, pain-relieving, and anticoagulant properties. Moreover, the review presents a summary of medications used in clinical settings, the disadvantages of the commercially available products, and insight into the latest development strategies. For a more successful translation of such research into clinical practice, extensive knowledge of the chemical interactions between the components and a detailed understanding of the properties and mechanisms of biological matter are required. Moreover, the cost-efficiency of the surface treatment should be considered in the development process.

[3D printing in spinal surgery-Update]

The technique of 3D printing offers a high potential for further optimization of spinal surgery. This new technology has been published for different areas in the field of spinal surgery, e.g. in preoperative planning, intraoperative use as well as to create patient-specific implants. For example, it has been demonstrated that preoperative 3‑dimensional visualization of spinal deformities is helpful in planning procedures. Moreover, insertion of pedicle screws seems to be more accurate when using individualized templates to guide the drill compared to freehand techniques. This review summarizes the current literature dealing with 3D printing in spinal surgery with special consideration of the current applications, the limitations and the future potential.

Reconstruction of Ipsilateral Femoral and Tibial Bone Defect by 3D Printed Porous Scaffold Without Bone Graft: A Case Report

CASE

This study reported the case of a 42-year-old woman with traumatic ipsilateral critical bone defect of right femur and tibia after a motor accident. Three-dimensional (3D) printed porous titanium scaffolds were innovatively used to reconstruct this challenging situation. The initial stability was safe enough for early exercise and partial weight bearing. The 26-month follow-up showed osseous integration of the prosthesis-bone interface with short-term satisfactory clinical result.

CONCLUSION

The custom-designed 3D-printed porous scaffold has the potential to become an effective option for reconstructing the segmental irregular-shaped bone defect.

Three-Dimensional Printing of Medical Devices Used Directly to Treat Patients: A Systematic Review

Until recently, three-dimensional (3D) printing/additive manufacturing has not been used extensively to create medical devices intended for actual clinical use, primarily on patient safety and regulatory grounds. However, in recent years there have been advances in materials, printers, and experience, leading to increased clinical use. The aim of this study was to perform a structured systematic review of 3D-printed medical devices used directly in patient treatment. A search of 13 databases was performed to identify studies of 3D-printed medical devices, detailing fabrication technology and materials employed, clinical application, and clinical outcome. One hundred and ten papers describing one hundred and forty medical devices were identified and analyzed. A considerable increase was identified in the use of 3D printing to produce medical devices directly for clinical use in the past 3 years. This is dominated by printing of patient-specific implants and surgical guides for use in orthopedics and orthopedic oncology, but there is a trend of increased use across other clinical specialties. The prevailing material/3D-printing technology used were titanium alloy/electron beam melting for implants, and polyamide/selective laser sintering or polylactic acid/fused deposition modeling for surgical guides and instruments. A detailed analysis across medical applications by technology and materials is provided, as well as a commentary regarding regulatory aspects. In general, there is growing familiarity with, and acceptance of, 3D printing in clinical use.

A Review on Development of Bio-Inspired Implants Using 3D Printing

Biomimetics is an emerging field of science that adapts the working principles from nature to fine-tune the engineering design aspects to mimic biological structure and functions. The application mainly focuses on the development of medical implants for hard and soft tissue replacements. Additive manufacturing or 3D printing is an established processing norm with a superior resolution and control over process parameters than conventional methods and has allowed the incessant amalgamation of biomimetics into material manufacturing, thereby improving the adaptation of biomaterials and implants into the human body. The conventional manufacturing practices had design restrictions that prevented mimicking the natural architecture of human tissues into material manufacturing. However, with additive manufacturing, the material construction happens layer-by-layer over multiple axes simultaneously, thus enabling finer control over material placement, thereby overcoming the design challenge that prevented developing complex human architectures. This review substantiates the dexterity of additive manufacturing in utilizing biomimetics to 3D print ceramic, polymer, and metal implants with excellent resemblance to natural tissue. It also cites some clinical references of experimental and commercial approaches employing biomimetic 3D printing of implants.

Opinion Piece: Patient-Specific Implants May Be the Next Big Thing in Spinal Surgery

The emergence of 3D-Printing technologies and subsequent medical applications have allowed for the development of Patient-specific implants (PSIs). There have been increasing reports of PSI application to spinal surgery over the last 5 years, including throughout the spine and to a range of pathologies, though largely for complex cases. Through a number of potential benefits, including improvements to the implant–bone interface and surgical workflow, PSIs aim to improve patient and surgical outcomes, as well as potentially provide new avenues for combating challenges routinely faced by spinal surgeons. However, obstacles to widespread acceptance and routine application include the lack of quality long-term data, research challenges and the practicalities of production and navigating the regulatory environment. While recognition of the significant potential of Spinal PSIs is evident in the literature, it is clear a number of key questions must be answered to inform future clinical and research practices. The spinal surgical community must selectively and ethically continue to offer PSIs to patients, simultaneously allowing for the necessary larger, comparative studies to be conducted, as well as continuing to provide optimal patient care, thereby ultimately determining the exact role of this technology and potentially improving outcomes.

Use of a novel Screen-Enrich-Combine(-biomaterials) Circulating System to fill a 3D-printed open Ti6Al4V frame with mesenchymal stem cells/β-tricalcium phosphate to repair complex anatomical bone defects in load-bearing areas

Background

Repairing complex anatomical load-bearing bone defects is difficult because it requires the restoration of the load-bearing function, reconstructing the anatomical shape, and repair by regenerated bone. We previously developed a Screen–Enrich–Combine(-biomaterials) Circulating System (SECCS) for rapid intraoperative enrichment of autologous bone marrow mesenchymal stem cells (MSCs) to enhance the osteogenic ability of porous bone substitutes. In this study, we prepared a 3D-printed Ti6A14V macroporous frame matching the defect shape to provide early load-bearing support and evaluated the efficacy of filling the frame with SECCS-processed MSCs/beta tricalcium phosphate (β-TCP) for long-term bone growth.

Methods

Fifteen 2-year-old goats were involved in this study, and the lateral part of their distal femur was removed by an electric saw and was fitted by a matching electron beam melting technology-prepared (EBM) Ti6Al4V frame. Three types of frames, filled with nothing, pure porous β-TCP, or SECCS-processed MSCs/β-TCP, were fixed onto the defect site. Repair efficacy was evaluated by X-ray radiography, computed tomography (CT), histology, and histomorphometry.

Results

In the basic regular hexagon printing unit, the combined side width (w) and the inscribed circle diameter (d) determines the printing frame’s mechanical strength. The compressive load was significantly higher for w=1.9 mm, d=4.4 mm than for w=1.7 mm, d=4.0 mm or w=2.0 mm, d=5.0 mm (P<0.05). The EBM-prepared Ti6Al4V defect-matched frame was well maintained 9 months after implantation. The MSCs successfully adhered to the wall of the porous β-TCP in the SECCS-processed group and had spread fully in the test samples. Each goat in the MSCs/β-TCP–the filled group, had approximately 31,321.7±22,554.7 of MSCs and a larger area of new bone growth inside the frame than the control and blank areas groups.

Conclusions

Filling the 3D-printed Ti6Al4V large-aperture frame with osteogenic materials achieved biological reconstruction over a larger area of regenerated bone to repair complex anatomical weight-bearing bone defects under the condition of early frame-supported load bearing. MSCs/β-TCP prepared by SECCS can be used as a filling material for this type of bone defect to obtain more efficacious bone repair.

A systematic review of preclinical in vivo testing of 3D printed porous Ti6Al4V for orthopedic applications, part I: Animal models and bone ingrowth outcome measures

For Ti6Al4V orthopedic and spinal implants, osseointegration is often achieved using complex porous geometries created via additive manufacturing (AM). While AM porous titanium (pTi) has shown clinical success, concerns regarding metallic implants have spurred interest in alternative AM biomaterials for osseointegration. Insights regarding the evaluation of these new materials may be supported by better understanding the role of preclinical testing for AM pTi. We therefore asked: (a) What animal models have been most commonly used to evaluate AM porous Ti6Al4V for orthopedic bone ingrowth; (b) What were the primary reported quantitative outcome measures for these models; and (c) What were the bone ingrowth outcomes associated with the most frequently used models? We performed a systematic literature search and identified 58 articles meeting our inclusion criteria. We found that AM pTi was evaluated most often using rabbit and sheep femoral condyle defect (FCD) models. Additional ingrowth models including transcortical and segmental defects, spinal fusions, and calvarial defects were also used with various animals based on the study goals. Quantitative outcome measures determined via histomorphometry including ''bone ingrowth'' (range: 3.92-53.4% for rabbit/sheep FCD) and bone-implant contact (range: 9.9-59.7% for rabbit/sheep FCD) were the most common. Studies also used 3D imaging to report outcomes such as bone volume fraction (BV/TV, range: 4.4-61.1% for rabbit/sheep FCD), and push-out testing for outcomes such as maximum removal force (range: 46.6-3092 N for rabbit/sheep FCD). Though there were many commonalities among the study methods, we also found significant heterogeneity in the outcome terms and definitions. The considerable diversity in testing and reporting may no longer be necessary considering the reported success of AM pTi across all model types and the ample literature supporting the rabbit and sheep as suitable small and large animal models, respectively. Ultimately, more standardized animal models and reporting of bone ingrowth for porous AM materials will be useful for future studies.