A prospective randomized cohort study on 3D-printed artificial vertebral body in single-level anterior cervical corpectomy for cervical spondylotic myelopathy

[Application of self-stabilizing zero-profile three-dimensional printed artificial vertebral bodies for treatment of cervical spondylotic myelopathy]

Objective

To evaluate the safety and effectiveness of applying self-stabilizing zero-profile three-dimensional (3D) printed artificial vertebral bodies in anterior cervical corpectomy and fusion (ACCF) for cervical spondylotic myelopathy.

Methods

A retrospective analysis was conducted on 37 patients diagnosed with cervical spondylotic myelopathy who underwent single-level ACCF using either self-stabilizing zero-profile 3D-printed artificial vertebral bodies ( n=15, treatment group) or conventional 3D-printed artificial vertebral bodies with titanium plates ( n=22, control group) between January 2022 and February 2023. There was no significant difference in age, gender, lesion segment, disease duration, and preoperative Japanese Orthopedic Association (JOA) score between the two groups ( P>0.05). Operation time, intraoperative bleeding volume, hospitalization costs, JOA score and improvement rate, incidence of postoperative prosthesis subsidence, and interbody fusion were recorded and compared between the two groups.

Results

Compared with the control group, the treatment group had significantly shorter operation time and lower hospitalization costs ( P<0.05); there was no significant difference in intraoperative bleeding volume between the two groups ( P>0.05). All patients were followed up, with a follow-up period of 6-21 months in the treatment group (mean, 13.7 months) and 6-19 months in the control group (mean, 12.7 months). No dysphagia occurred in the treatment group, while 5 cases occurred in the control group, with a significant difference in the incidence of dysphagia between the two groups ( P<0.05). At 12 months after operation, both groups showed improvement in JOA scores compared to preoperative scores, with significant differences ( P<0.05); however, there was no significant difference in the JOA scores and improvement rate between the two groups ( P>0.05). Radiographic examinations showed the interbody fusion in both groups, and the difference in the time of interbody fusion was not significant ( P>0.05). At last follow-up, 2 cases in the treatment group and 3 cases in the control group experienced prosthesis subsidence, with no significant difference in the incidence of prosthesis subsidence ( P>0.05). There was no implant displacement or plate-screw fracture during follow-up.

Conclusion

The use of self-stabilizing zero-profile 3D-printed artificial vertebral bodies in the treatment of cervical spondylotic myelopathy not only achieves similar effectiveness to 3D-printed artificial vertebral bodies, but also reduces operation time and the incidence of postoperative dysphagia.

Current update and trend of 3D printing in spinal surgery: A bibliometric analysis and review of literature

Incorporation of three-dimensional (3D) printing technology into the field of spinal surgery is on the rise. A bibliometric analysis of the current topic was carried out to elaborate the trend and to navigate future research. A Scopus database search was conducted with keywords related to 3D printing, spine, and surgery. The final 792 articles were extracted and further analyzed with VOSviewer 1.6.19 and Biblioshiny. The first published article was in 2002. A notable increase in articles in 2014 might be attributable to the availability of cheaper 3D printers which rose significantly on a global scale in 2011. China leads in terms of published research on 3D printing in spinal surgery, followed by the US, Australia, and India. The author's keyword co-occurrence analysis reveals 8 theme clusters, including preoperative and intraoperative measures, biomodelling, spinal neoplasms, biomechanics of 3D-printed materials, degenerative spinal diseases, minimally invasive surgery, and bioprinting. The top 15 of the most recently cited keywords are listed to provide future researchers to produce impactful articles. Two strategic diagrams of 2 periods (2002-2018 and 2018-2023) show the theme's evolution. We found 6 consistent themes in keyword co-occurrence analysis and the strategic diagram analysis, that are promising subjects for future research. Overall, this bibliographic study indicates the expanding importance of 3D printing in spinal surgery and suggests several critical themes and impactful keywords for future researchers.

[Clinical outcomes of 3D-printing stand-alone artificial vertebral body in anterior cervical surgeries]

OBJECTIVE

To explore the short-term outcomes of 3D-printing stand-alone artificial vertebral body (AVB) in the surgical procedure of anterior cervical corpectomy and fusion (ACCF).

METHODS

Following the proposal of IDEAL (idea, development, exploration, assessment, and long-term follow-up) framework, we designed and conducted this single-armed, retrospective cohort study. The patients with cervical spondylotic myelopathy were recruited, and these patients exclusively received the surgical procedure of single-level ACCF in our single center. After the process of corpectomy, the size was tailored using different trials and the most suitable stand-alone AVB was then implanted. This AVB was manufactured by the fashion of 3D-printing. Two pairs of screws were inserted in an inclined way into the adjacent vertebral bodies, to stabilize the AVB. The participants were regularly followed-up after the operation. Their clinical data were thoroughly reviewed. We assessed the neurological status according to Japanese Orthopedic Association (JOA) scale. We determined the fusion based on imaging examination six months after the operation. The recorded clinical data were analyzed using specific software and they presented in suitable styles. Paired t test was employed in comparison analysis.

RESULTS

In total, there were eleven patients being recruited eventually. The patients were all followed up over six months after the operation. The mean age of the cohort was (57.2±10.2) years. The mean operation time was (76.1±23.1) min and the median bleeding volume was 150 (100, 200) mL. The postoperative course was uneventful for all the cases. Dysphagia, emergent hematoma, and deterioration of neurological function did not occur. Mean JOA scores were 13.2±2.2 before the operation and 16.3±0.8 at the final follow-up, which were significantly different (P < 0.001). The mean recovery rate of neurological function was 85.9%. By comparing the imaging examinations postoperatively and six months after the operation, we found that the average subsidence length was (1.2±1.1) mm, and that there was only one cases (9.1%) of the severe subsidence (>3 mm). We observed significant improvement of cervical lordosis after the operation (P=0.013). All the cases obtained solid fusion.

CONCLUSION

3D-printing stand-alone AVB presented favorable short-term outcome in one-level ACCF in this study. The fusion rate of this zero-profile prosthesis was satisfactory and the complication rate was relatively low.

Systematic review of the utility and limits of 3D printing in spine surgery

OBJECTIVE

The main objective of this study has been to demonstrate why additive printing allows to make complex surgical pathological processes that affect the spine more visible and understandable, increasing precision, safety and reliability of the surgical procedure.

METHODS

A systematic review of the articles published in the last 10 years on 3D printing-assisted spinal surgery was carried out, in accordance with PRISMA 2020 declaration. Keywords "3D printing" and "spine surgery" were searched in Pubmed, Embase, Cochrane Database of Systematic Reviews, Google Scholar and Opengrey databases, which was completed with a manual search through the list of bibliographic references of the articles that were selected following the defined inclusion and exclusion criteria.

RESULTS

From the analysis of the 38 selected studies, it results that 3D printing is useful in surgical planning, medical teaching, doctor-patient relationship, design of navigation templates and spinal implants, and research, optimizing the surgical process by focusing on the patient, offering magnificent support during the surgical procedure.

CONCLUSIONS

The use of three-dimensional printing biomodels allows: making complex surgical pathological processes that affect the spine more visible and understandable; increase the accuracy, precision and safety of the surgical procedure, and open up the possibility of implementing personalized treatments, mainly in tumor surgery.

A novel artificial vertebral implant with Gyroid porous structures for reducing the subsidence and mechanical failure rate after vertebral body replacement

BACKGROUND

Prosthesis subsidence and mechanical failure were considered significant threats after vertebral body replacement during the long-term follow-up. Therefore, improving and optimizing the structure of vertebral substitutes for exceptional performance has become a pivotal challenge in spinal reconstruction.

METHODS

The study aimed to develop a novel artificial vertebral implant (AVI) with triply periodic minimal surface Gyroid porous structures to enhance the safety and stability of prostheses. The biomechanical performance of AVIs under different loading conditions was analyzed using the finite element method. These implants were fabricated using selective laser melting technology and evaluated through static compression and subsidence experiments.

RESULTS

The results demonstrated that the peak stress in the Gyroid porous AVI was consistently lower than that in the traditional porous AVI under all loading conditions, with a maximum reduction of 73.4%. Additionally, it effectively reduced peak stress at the bone-implant interface of the vertebrae. Static compression experiments demonstrated that the Gyroid porous AVI was about 1.63 times to traditional porous AVI in terms of the maximum compression load, indicating that Gyroid porous AVI could meet the safety requirement. Furthermore, static subsidence experiments revealed that the subsidence tendency of Gyroid porous AVI in polyurethane foam (simulated cancellous bone) was approximately 15.7% lower than that of traditional porous AVI.

CONCLUSIONS

The Gyroid porous AVI exhibited higher compressive strength and lower subsidence tendency than the strut-based traditional porous AVI, indicating it may be a promising substitute for spinal reconstruction.

Implant failure and revision strategies after total spondylectomy for spinal tumors

Background

Although there have been several risk factors reported for implant failure (IF), little consensus exists. Potential applicable measures to protect patients from IF are relatively few. This study aimed to discover new risk factors for IF and explore potential protective measures from IF after total spondylectomy for spinal tumors.

Methods

A total of 145 patients undergoing total spondylectomy for thoracic and lumbar spinal tumors between 2010 and 2021 were included from three tertiary university hospitals. Patient demographic and surgical characteristics and follow-up outcomes were collected.

Results

During a mean follow-up of 53.77 months (range, 12 to 149 months), 22 of 145 patients (15.17%) developed IF. Patients undergoing thoracolumbar junctional region (T12/L1) resection were more likely to develop IF compared to those undergoing surgery at other vertebral levels (HR = 21.622, 95% CI = 3.567-131.084, P = 0.001). Patients undergoing titanium mesh cage reconstruction were more likely to develop IF compared to patients undergoing expandable titanium cage reconstruction (HR = 8.315, 95% CI = 1.482-46.645, P = 0.016). Patients with bone cement augmentation around the cage were less likely to develop IF compared to those not receiving bone cement augmentation (HR = 0.015, 95% CI = 0.002-0.107, P < 0.001). Of the 22 patients with IF, 14 (63.63%) accepted personalized revision surgery.

Conclusion

The use of an expandable cage and the use of bone cement augmentation around the anterior column support cage are protective measures against IF after total spondylectomy.

Comparison of radiological and clinical outcomes of 3D-printed artificial vertebral body with Titanium mesh cage in single-level anterior cervical corpectomy and fusion: A meta-analysis

Propose

This meta-analysis aimed to determine whether 3D-printed artificial vertebral body have superior clinical and radiographic outcome than Titanium Mesh Cage(TMC) in single-level anterior cervical corpectomy and fusion.

Methods

A comprehensive search of the PubMed, Embase, Cochrane Library, Web of Science, and CNKI (China National Knowledge Infrastructure) databases was conducted to find randomized control trials (RCTs) or cohort studies that compared 3D-printed artificial vertebral body with conventional Titanium Mesh Cage (TMC) in single-level anterior cervical corpectomy and fusion (SL-ACCF). Operation time; intraoperative blood loss; subsidence of vertebral body; preoperative, and final follow-up C2-C7 Cobb angle, Japanese Orthopedic Association (JOA) scores, and Visual Analog Scale(VAS) scores were collected from eligible studies for meta-analysis.

Results

We included 6 cohort studies with 341 patients. The results of the meta-analysis showed that the 3D group has a shorter operation time than the traditional TMC group(p = 0.04) and the TMC group had more severe subsidence(≥3 mm) of vertebral body than the 3D group(p < 0.0001). And the cervical C2-C7 Cobb angle in the 3D group was larger than that in the TMC group at the final follow-up.

Conclusion

This meta-analysis demonstrates that 3D-printed artificial vertebral body is superior to traditional TMC in reducing the operation time and maintaining the postoperative vertebral height and restoring sagittal balance to the cervical spine in single-level anterior cervical corpectomy and fusion.

Effect of different fixation methods on biomechanical property of cervical vertebral body replacement and fusion

BACKGROUND

The main purpose of this study was to examine the effect of different fixation methods (anterior fixation, self-stabilizing fixation and anterior-posterior fixation) on biomechanical property of vertebral body replacement and fusion.

METHODS

Three finite element models of cervical vertebral body replacement and fusion were established. The implanted models included artificial vertebral body and fixation system, and the loads imposed on the models included 75 N compression load and 1 Nm moment load.

FINDINGS

For anterior-posterior fixation, the cervical load was mainly transmitted by the posterior pedicle screw and rod (more than 50%), and the stress shielding problem was the most significant than the self-stabilizing and anterior fixation. Self-stabilizing fixation was more helpful to the fusion of implant and vertebrae, but the higher risk of vertebral body collapse was worthy of attention if the cervical spine with osteoporosis. The stress of bone was mainly concentrated around the screw hole. The maximum stress (20.03 MPa) was lower than the yield stress of cortical bone and the possibility of fracture around the fixation device of cervical spine was low. The anterior fixation could meet the requirement of vertebral body replacement and fusion, and the addition of posterior pedicle screws and rods might obtain better treatment in cases of severe spine injury or osteoporosis.

INTERPRETATION

The findings of this study may provide guidance on clinical treatments for choosing more appropriate fixation methods for different patients.

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.

Biomechanical comparison of different prosthetic reconstructions in total en bloc spondylectomy: a finite element study

Objective

To analyse and compare the biomechanical differences between 3D-printed prostheses, titanium mesh cages and poorly matched titanium mesh cages in total en bloc spondylectomy (TES).

Methods

The finite element model of T10-L2 for healthy adults was modified to make three models after T12 total spondylectomy. These models were a 3D-printed prosthesis, titanium mesh cage and prosthesis-endplate mismatched titanium mesh cage for reconstruction. The range of motion (ROM), stress distribution of the endplate and internal fixation system of three models in flexion and extension, lateral bending and axial rotation were simulated and analysed by ABAQUS.

Result

In flexion, due to the support of the anterior prosthesis, the fixation system showed the maximum fixation strength. The fixation strength of the 3D-printed prosthesis model was 26.73 N·m /°, that of the TMC support model was 27.20 N·m /°, and that of the poorly matched TMC model was 24.16 N·m /°. In flexion, the L1 upper endplate stress of the poorly matched TMC model was 35.5% and 49.6% higher than that of the TMC and 3D-printed prosthesis, respectively. It was 17% and 28.1% higher in extension, 39.3% and 42.5% higher in lateral bending, and 82.9% and 91.2% higher in axial rotation, respectively. The lower endplate of T11 showed a similar trend, but the magnitude of the stress change was reduced. In the stress analysis of the 3D-printed prosthesis and TMC, it was found that the maximum stress was in flexion and axial rotation, followed by left and right bending, and the least stress was in extension. However, the mismatched TMC withstood the maximum von Mises stress of 418.7 MPa (almost twice as much as the buckling state) in rotation, 3 times and 5.83 times in extension, and 1.29 and 2.85 times in lateral bending, respectively.

Conclusion

Different prostheses with good endplate matching after total spondylectomy can obtain effective postoperative stable support, and the reduction in contact area caused by mismatch will affect the biomechanical properties and increase the probability of internal fixation failure.

Clinical and radiological efficacy of corpectomy and anterior stabilization with titanium mesh cages in patients with myelopathic syndrome associated with cervical spine degenerative di

The aim of this study was to research the clinical and radiological efficacy of  corpectomy and anterior stabilization with titanium mesh cages in patients with myelopathic syndrome associated with cervical spine degenerative diseases.

Material and methods. A retrospective observational cohort study was performed. The study included medical records of patients with cervical myelopathy associated with degenerative diseases of the cervical spine who underwent corpectomy and  anterior stabilization with titanium mesh cages. Clinical and instrumental parameters were assessed.

Results. The study included 28  medical records of respondents who underwent corpectomy and anterior stabilization with titanium mesh implants. The average age of patients was 61.9 ± 11.3 years, males prevailed (60.7 %). By the 3rd month of  postoperative follow-up, the severity of myelopathy significantly decreased (p˂0.001). After 12  months, the severity of cervical myelopathic syndrome also significantly decreased (p = 0.009). The neurological status of 18 (64.2 %) respondents improved in the first 3  months after corpectomy and anterior stabilization with titanium mesh implants and 6 months after the surgery, the status improved in the remaining 8 (30.7 %) patients (p˂0.001). Preoperative values of the Cobb sagittal angle allowed us to conclude the following. In 13 (46.4 %) patients, the normolordotic axis of the cervical spine was noted, in 12  (42.8  %) – the  hypolordotic axis, and in 3 (10.8 %) respondents, the Cobb angle values corresponded to the kyphotic axis of the cervical spine.

Conclusion. The technique of corpectomy and anterior fixation with mesh titanium implants in patients with myelopathic syndrome against the background of  degenerative diseases of the cervical spine makes it possible to improve the clinical status of the latter already 3 months after the operation was performed while maintaining normal biomechanical parameters of the cervical spine and complete decompression of the neural structures and supply their vessels. 

3D printing in orthopaedic surgery: a scoping review of randomized controlled trials

Aims

The use of 3D printing has become increasingly popular and has been widely used in orthopaedic surgery. There has been a trend towards an increasing number of publications in this field, but existing literature incorporates limited high-quality studies, and there is a lack of reports on outcomes. The aim of this study was to perform a scoping review with Level I evidence on the application and effectiveness of 3D printing.

Methods

A literature search was performed in PubMed, Embase, and Web of Science databases. The keywords used for the search criteria were ((3d print*) OR (rapid prototyp*) OR (additive manufactur*)) AND (orthopaedic). The inclusion criteria were: 1) use of 3D printing in orthopaedics, 2) randomized controlled trials, and 3) studies with participants/patients. Risk of bias was assessed with Cochrane Collaboration Tool and PEDro Score. Pooled analysis was performed.

Results

Overall, 21 studies were included in our study with a pooled total of 932 participants. Pooled analysis showed that operating time (p < 0.001), blood loss (p < 0.001), fluoroscopy times (p < 0.001), bone union time (p < 0.001), pain (p = 0.040), accuracy (p < 0.001), and functional scores (p < 0.001) were significantly improved with 3D printing compared to the control group. There were no significant differences in complications.

Conclusion

3D printing is a rapidly developing field in orthopaedics. Our findings show that 3D printing is advantageous in terms of operating time, blood loss, fluoroscopy times, bone union time, pain, accuracy, and function. The use of 3D printing did not increase the risk of complications.

Cite this article: Bone Joint Res 2021;10(12):807–819.