Clinical application of three-dimensional printing in the personalized treatment of complex spinal disorders

Reconstruction after Pelvic Bone Massive Resection: Evolution and Actuality of 3D-Printing Technology

PURPOSE OF THE STUDY

Pelvic reconstructions after massive bone resections are among the most challenging practices in orthopedic surgery. Whether the bone gap results after a trauma, a tumor resection, or it is due to a prosthetic revision, it is mandatory to reconstruct pelvic bone continuity and rebuild the functional thread that connects spine and hip joint. Several different approaches have been described in literature through the decades to achieve those goals.

MATERIAL AND METHODS

To this date, 3D-printed implants represent one of the most promising surgical technologies in orthopedic oncology and complex reconstructive surgery. We present our experience with 3D-printed custom-made pelvic prostheses to fulfi ll bone gaps resulting from massive bone loss due to tumor resections. We retrospectively evaluated 17 cases treated with pelvic bone reconstruction using 3D-printed prostheses. Cases were evaluated in terms of both oncological and functional outcomes.

RESULTS

At the last follow-up, local complications were found in 6 cases (36%): in 4 (23.5%) of them the cause was a local recurrence of the disease, whereas only 2 (12.5%) had non-oncologic issues. The mean MSTS score in our population increased from 8.2 before surgery to 22.3 at the latest clinical control after surgery.

DISCUSSION

3D-printing technology, used to produce cutting jigs and prosthetic implants, can lead to good clinical and functional outcomes. These encouraging results are comparable with the ones obtained with other more frequently used reconstructive approaches and support custom-made implants as a promising reconstructive approach.

CONCLUSIONS

Our data confi rm 3D-printing and custom-made implants as promising technologies that could shape the next future of orthopedic oncology and reconstructive surgery.

KEY WORDS

custom made prosthesis, pelvic reconstruction, orthopedic oncology, cutting jigs, 3D-printing.

Three-dimensional printing versus traditional surgery for inveterate pelvic and acetabular fractures: A retrospective study of 37 patients

Treatment of deformed pelvic and acetabular fractures is a considerable challenge for orthopedic surgeons. The aim of this study was to assess the availability of a three-dimensional (3D) printing model used in patients with inveterate pelvic and acetabular fractures by comparing 3D printing technology with conventional surgery. We conducted a retrospective review of patients with inveterate pelvic and acetabular fractures treated in our department between January 2008 and June 2020. The patients were divided into 2 groups according to their willingness. Perioperative data and clinical outcomes were compared to evaluate clinical efficacy. The t-test, Fisher exact test, and multivariable logistic regression analysis were conducted. A P value of .05 or less was considered to be statistically significant (two-tailed). Thirty-seven patients were enrolled in our study. Seventeen patients were divided into the case group treated by 3D printing model-assisted preoperative planning, and 20 patients were divided into the control group treated by conventional surgery. Patients treated with the 3D printing model had significantly shorter operation times, less blood loss, and shorter fluoroscopy times. Patients in the case group also showed better pain relief according to visual analog scale scores. However, the elevations in pelvis and hip joint functional outcomes were similar between the 2 groups, and no significant difference was shown in the radiological result. The usage of 3D printing techniques in patients with inveterate pelvic and acetabular fractures is of great importance in preoperative preparation and optimization of surgery but cannot improve postoperative function compared with conventional treatment.

Accuracy of a 3-dimensionally printed custom endoscopy port for minimally invasive ventral slot decompression in dogs: A cadaveric study

OBJECTIVE

To evaluate the accuracy of a 3-dimensionally (3D)-printed custom endoscopy port (3DEP) for minimally invasive cervical ventral slot decompression.

STUDY DESIGN

Cadaveric study.

ANIMALS

Fifteen cadavers of dogs weighing between 3.1 and 34.4 kg.

METHODS

Minimally invasive cervical ventral slots were created using a 3DEP and an endoscopic system at the C3-C4 intervertebral disc space in each dog by 1 experienced and 1 inexperienced surgeon. Postoperative computed tomography was performed to compare the planned and postoperative screw trajectories (angle, entry point, exit point, and length of the screw entering the spinal canal) and quantify slot formation dimensions.

RESULTS

Thirty screws were inserted in 30 vertebral bodies. Mean screw angle deviation was less than 2.5°, entry and exit point deviation was less than 1.6 mm, and length of the screw entering the spinal canal was less than 0.6 mm. No differences were identified between the experienced and inexperienced surgeons. Ventral slot length ratio was 30.15 ± 1.86 for the experienced surgeon and 29.38 ± 1.61 for the inexperienced surgeon (p = .372). The mean ventral slot width ratio was 45.60 ± 1.80 for the experienced surgeon and 47.20 ± 1.54 for the inexperienced surgeon (p = .261).

CONCLUSION

Screw positioning and creation of ventral slots were accurately performed using the 3DEP by both inexperienced and experienced surgeons.

CLINICAL SIGNIFICANCE

The use of a 3DEP for minimally invasive cervical ventral slot decompression may be an alternative to the conventional ventral slot in dogs. Additional studies are needed to evaluate efficacy and safety.

3D printing for spine pathologies: a state-of-the-art review

Three-Dimensional Printing has advanced throughout the years in the field of biomedical science with applications, especially in spine surgeries. 3D printing has the ability of fabricating highly complex structures with ease and high dimensional accuracy. The complexity of the spine's architecture and the inherent dangers of spinal surgery bring the evaluation of 3D printed models into consideration. This article summarizes the benefits of 3D printing based models for application in spine pathology. 3D printing technique is extensively used for fabrication of anatomical models, surgical guides and patient specific implants (PSI). The 3D printing based anatomical models assist in preoperative planning and training of students. Furthermore, 3D printed models can be used for improved communication and understanding of patients about the spinal disorders. The use of 3D printed surgical guides help in the stabilization of the spine during surgery, improving post procedural outcomes. Improved surgical results can be achieved by using PSIs that are tailored for patient specific needs. Finally, this review discusses the limitations and potential future scope of 3D printing in spine pathologies. 3D printing is still in its infancy, and further research would provide better understanding of the technology's true potential in spinal procedures.

The Role of 3D Printing in Treatment Planning of Spine and Sacral Tumors

Three-dimensional (3D) printing technology has proven to have many advantages in spine and sacrum surgery. 3D printing allows the manufacturing of life-size patient-specific anatomic and pathologic models to improve preoperative understanding of patient anatomy and pathology. Additionally, virtual surgical planning using medical computer-aided design software has enabled surgeons to create patient-specific surgical plans and simulate procedures in a virtual environment. This has resulted in reduced operative times, decreased complications, and improved patient outcomes. Combined with new surgical techniques, 3D-printed custom medical devices and instruments using titanium and biocompatible resins and polyamides have allowed innovative reconstructions.

Accuracy of 3D printed spine models for pre-surgical planning of complex adolescent idiopathic scoliosis (AIS) in spinal surgeries: a case series

Adolescent idiopathic scoliosis (AIS) is a noticeable spinal deformity in both adult and adolescent population. In majority of the cases, the gold standard of treatment is surgical intervention. Technological advancements in medical imaging and 3D printing have revolutionised the surgical planning and intraoperative decision making for surgeons in spinal surgery. However, its applicability for planning complex spinal surgeries is poorly documented with human subjects. The objective of this study is to evaluate the accuracy of 3D printed models for complex spinal deformities based on Cobb angles between 40° to 95°.This is a retrospective cohort study where, five CT scans of the patients with AIS were segmented and 3D printed for evaluating the accuracy. Consideration was given to the Inter-patient and acquisition apparatus variability of the CT-scan dataset to understand the effect on trueness and accuracy of the developed CAD models. The developed anatomical models were re-scanned for analysing quantitative surface deviation to assess the accuracy of 3D printed spinal models. Results show that the average of the root mean square error (RMSE) between the 3DP models and virtual models developed using CT scan of mean surface deviations for the five 3d printed models was found to be 0.5±0.07 mm. Based on the RMSE, it can be concluded that 3D printing based workflow is accurate enough to be used for presurgical planning for complex adolescent spinal deformities. Image acquisition and post processing parameters, type of 3D printing technology plays key role in acquiring required accuracy for surgical applications.

Analysis of the approach angle to medial orbitotomy that avoids accidental neurotrauma in the mesaticephalic dog skull utilizing 3D computer models and virtual surgical planning

This study was conducted to determine an approach angle to medial orbitotomy that avoids accidental neurotrauma in mesaticephalic dogs. Medical records of dogs with mesaticephalic skulls that were presented to the veterinary medical teaching hospital for head computed tomography (CT) between September 2021 and February 2022 were reviewed. Descriptive data were queried, and CT findings were analyzed. Dogs greater than 20 kg and possessing a disease-free orbitozygomaticomaxillary complex (OZMC) on at least one side of the skull were included in this study. Digital imaging and communications in medicine (DICOM) files of head CT studies were imported into medical modeling software, and the safe approach angle for medial orbitotomy was determined using three-dimensional (3D) computer models and virtual surgical planning (VSP) principles. Angles were measured along the ventral orbital crest (VOC) from the rostral cranial fossa (RCF) to the rostral alar foramen (RAF). The safe approach angle at four points from rostral to caudal along the VOC was measured. The results at each location were reported as mean, median, 95% CI, interquartile ranges, and distribution. The results were statistically different at each location and generally increased from rostral to caudal. The variances between subjects and the differences between locations were large enough to suggest a standard safe approach angle in mesaticephalic dogs cannot be determined and should be measured for each patient. A standardized approach angle to medial orbitotomy is not possible in the mesaticephalic dog. Computer modeling and VSP principles should be implemented as part of the surgical planning process to accurately measure the safe approach angle along the VOC.

Properties and Implementation of 3-Dimensionally Printed Models in Spine Surgery: A Mixed-Methods Review With Meta-Analysis

OBJECTIVE

Spine surgery addresses a wide range of spinal pathologies. Potential applications of 3-dimensional (3D) printed in spine surgery are broad, encompassing education, planning, and simulation. The objective of this study was to explore how 3D-printed spine models are implemented in spine surgery and their clinical applications.

METHODS

Methods were combined to create a scoping review with meta-analyses. PubMed, EMBASE, the Cochrane Library, and Scopus databases were searched from 2011 to 7 September 2021. Results were screened independently by 2 reviewers. Studies utilizing 3D-printed spine models in spine surgery were included. Articles describing drill guides, implants, or nonoriginal research were excluded. Data were extracted according to reporting guidelines in relation to study information, use of model, 3D printer and printing material, design features of the model, and clinical use/patient-related outcomes. Meta-analyses were performed using random-effects models.

RESULTS

Forty articles were included in the review, 3 of which were included in the meta-analysis. Primary use of the spine models included preoperative planning, education, and simulation. Six printing technologies were utilized. A range of substrates were used to recreate the spine and regional pathology. Models used for preoperative and intraoperative planning showed reductions in key surgical performance indicators. Generally, feedback for the tactility, utility, and education use of models was favorable.

CONCLUSIONS

Replicating realistic spine models for operative planning, education, and training is invaluable in a subspeciality where mistakes can have devastating repercussions. Future study should evaluate the cost-effectiveness and the impact spine models have of spine surgery outcomes.

Tribo-corrosive behavior of additive manufactured parts for orthopaedic applications

Background

Additive manufacturing (AM) being an integral component of the production offers a wide variety of applications in the production of different components. The medical industry after the introduction of Additive Manufacturing has resulted in several advancements. The production of intricate patient-specific implants is one of such advancements which greatly assist a surgeon during a surgery. Orthopedic implants apart from possessing good mechanical strength are also expected to exhibit good tribological and corrosion behavior. As a result, the development of various orthopaedic implants and tools has become simple with the use of additive manufacturing.

Objectives and Rationale

In the current paper an effort has been made to discuss actual scientific knowledge on the tribo-corrosive behavior of additive manufactured parts for orthopedic applications. Different studies dealing with the mechanisms of lubrication and friction in synovial joints have also been considered. A special focus has also been laid down to study the corrosive effect of implants on the human body. A section dedicated to texturing of orthopedic implants has also been provided. The paper further elaborates the different research challenges and issues related to the use of additive manufacturing for the production of optimized orthopedic implants.

Conclusion

The study revealed that additive manufacturing has greatly aided in the manufacture of different orthopaedic implants with enhanced properties. However, a detailed study of the effect of processes like friction, wear, lubrication and corrosion in these implants needs to be done. The performance of these implants in the presence of various synovial fluids also needs to be addressed. However, the lack of more biocompatible materials, scalability and cost issues hinder the widespread use of AM in the different orthopaedic applications.

Prediction of the functional and radiological outcome on the basis of independent factors with special emphasis on the use of 3D printed models in craniovertebral junction surgery

Background:

The aim of the study was to evaluate the advantage of performing planned surgery using customized three-dimensional (3D) printed models versus performing surgery without using 3D printed models in patients with craniovertebral junction (CVJ) anomalies and traumatic CVJ fractures and dislocations.

Methods:

Forty-two patients with CVJ anomalies, who were planned for operative intervention in the Department of Neurosurgery at SMS Hospital from March 2019 to February 2021, were randomly divided into two groups and analyzed. First group was operated after rehearsal on a customized 3D printed model whereas the second group underwent operative intervention without the rehearsal of surgery on the 3D printed model.

Results:

Forty-two patients were enrolled for the study. Twenty-five of these patients had developmental CVJ anomalies, 16 had post traumatic Atlantoaxial dislocation (AAD), and one had congenital AAD. Twenty-three patients underwent surgical intervention using 3D printed models and 19 without using 3D printed models. The outcome in the two groups was compared using modified Japanese orthopedic association score (mJOA), recovery rate, incidence of complications such as screw malposition, postoperative neurological deterioration, vertebral artery (VA) injury, and radiological improvement based on Atlanto-Dental interval, the distance of the tip of dens from Wackhenheims clivus canal line, and the distance of tip of dens from the Chamberlain’s line. The improvement in mJOA score postoperatively was found to be statistically significant in study group (P < 0.001) as compared to control group (P = 0.06). Recovery rate was better in study group than in control group (P = 0.023). In study group, the incidence of screw malposition and VA injury was lower than control group. Three patients deteriorated neurologically postoperatively in the control group and none in the study group. The average improvements in the radiological parameters were found to be better in study group as compared to control group postoperatively.

Conclusion:

The authors conclude that 3D printed models are extremely helpful in analyzing joints and VA anatomy preoperatively and are helpful in unmasking any abnormal bony and vascular anatomy effectively, making the surgeon confident about the placement of the screws intraoperatively. These 3D models help in intraoperative error minimization with better neurological outcomes in postoperative period. In our opinion, these models should be included as a basic investigation tool in patients of CVJ abnormalities. The models also offer other advantages such as preoperative simulation, teaching modules, and patient education.

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.

NO SIGNIFICANT EFFECT OF 3D MODELLING ON SURGICAL PLANNING IN SPINAL DEFORMITIES

ABSTRACT Objective: To evaluate the effect of 3d printed models on surgical pre-operative planning of complex spinal deformities. Methods: In our study, five orthopedic surgeons made surgical planning of 5 patients with severe spinal deformity in three conditions: X-ray with computer tomography (X-ray-CT), 3D-computed tomography (3dCT), and 3d printed spine models. Operation plans were examined according to the level and number of instrumentations, osteotomy level, and time required for decision-making. Results: X-ray-CT, 3dCT, and 3d modeling methods were compared, and no statistically significant difference was observed in the number of screws and osteotomy score to be used in operation. The time required for decision ranking is 3d Model, 3d CT, and Xray-CT. Conclusions: 3d printed models do not influence the operative plan significantly; however, it reduces surgical planning time at pre-op duration, and those models gave some opportunities to practice with implants on a patient’s 3d spine model. Level of Evidence III; Diagnostic Studies - Investigating a Diagnostic Test .

Establishing a point-of-care additive manufacturing workflow for clinical use

Additive manufacturing, or 3-Dimensional (3-D) Printing, is built with technology that utilizes layering techniques to build 3-D structures. Today, its use in medicine includes tissue and organ engineering, creation of prosthetics, the manufacturing of anatomical models for preoperative planning, education with high-fidelity simulations, and the production of surgical guides. Traditionally, these 3-D prints have been manufactured by commercial vendors. However, there are various limitations in the adaptability of these vendors to program-specific needs. Therefore, the implementation of a point-of-care in-house 3-D modeling and printing workflow that allows for customization of 3-D model production is desired. In this manuscript, we detail the process of additive manufacturing within the scope of medicine, focusing on the individual components to create a centralized in-house point-of-care manufacturing workflow. Finally, we highlight a myriad of clinical examples to demonstrate the impact that additive manufacturing brings to the field of medicine.

The utilisation of 3D printing in paediatric neurosurgery

3D printing technology has evolved over the years and there is a growing interest in its application in paediatric neurosurgery. Modern 3D printers have enabled the development of patient-specific 3D models that provide a realistic representation of complex anatomies and will aid in planning complex procedures. Paediatric neurosurgical operations are challenging and hands-on training is restricted. Surgical simulation training with biomodel has provided a new paradigm for trainees to master their surgical skills before encountering similar scenarios in real-life environment. This paper reviews the aspects of 3D printing for preoperative planning and simulation-based surgical training in paediatric neurosurgery.

Usefulness of a Three-Dimensional-Printed Model in the Treatment of Irreducible Atlantoaxial Dislocation with Transoral Atlantoaxial Reduction Plate

Objective

To evaluate the usefulness of a 3D‐printed model for transoral atlantoaxial reduction plate (TARP) surgery in the treatment of irreducible atlantoaxial dislocation (IAAD).

Methods

A retrospective review was conducted of 23 patients (13 men, 10 women; mean age 58.17 ± 5.27 years) with IAAD who underwent TARP from January 2015 to July 2017. Patients were divided into a 3D group (12 patients) and a non‐3D group (11 patients). A preoperative simulation process was undertaken for the patients in the 3D group, with preselection of the TARP system using a 3D‐printed 1:1 scale model, while only imaging data was used for the non‐3D group. Complications, clinical outcomes (Japanese Orthopaedic Association [JOA] and visual analogue score [VAS]), and image measurements (atlas–dens interval [ADI], cervicomedullary angle [CMA], and clivus‐canal angle [CCA]) were noted preoperatively and at the last follow up.

Results

A total of 23 patients with a follow‐up time of 16.26 ± 4.27 months were included in the present study. The surgery duration, intraoperative blood loss, and fluoroscopy times in the 3D group were found to be shorter than those in non‐3D group, with statistical significance. The surgery duration was 3.29 ± 0.45 h in the 3D group and 4.68 ± 0.90 h in the non‐3D group, and the estimated intraoperative blood loss was 131.67 ± 43.03 mL in the 3D group and 185.45 ± 42.28 mL in the non‐3D group. No patients received blood transfusions. The intraoperative fluoroscopy times were 5.67 ± 0.89 in the 3D group and 7.91 ± 1.45 in the non‐3D group. Preoperatively and at last follow up, JOA and VAS scores and ADI, CCA, and CMA were improved significantly within the two groups. However, no statistical difference was observed between the two groups. However, surgical site infection occurred in 1 patient in the 3D group, who underwent an emergency revision operation of the removal of TARP device and posterior occipitocervical fixation; the patient recovered 2 weeks after the surgery. In 2 patients in the traditional group, a mistake occurred in the placement of screws, with no neurological symptoms related to the misplacement.

Conclusion

Preoperative surgical simulation using a 3D‐printed real‐size model is an intuitive and effective aid for TARP surgery for treating IAAD. The 3D‐printed biomodel precisely replicated patient‐specific anatomy for use in complicated craniovertebral junction surgery. The information was more useful than that available with 3D reconstructed images.

3D printing and spine surgery

Rapid prototyping (RP), also known as three-dimensional printing (3DP), allows the rapid conversion of anatomical images into physical components by the use of special printers. This novel technology has also become a promising innovation for spine surgery. As a result of the developments in 3DP technology, production speeds have increased, and costs have decreased. This technological development can be used extensively in different parts of spine surgery such as preoperative planning, surgical simulations, patient-clinician communication, education, intraoperative guidance, and even implantable devices. However, similar to other emerging technologies, the usage of RP in spine surgery has various drawbacks that are needed to be addressed through further studies.

A modern multidisciplinary approach to a large cervicothoracic chordoma using staged en bloc resection with intraoperative image-guided navigation and 3D-printed modeling: illustrative case

BACKGROUND

Cervicothoracic junction chordomas are uncommon primary spinal tumors optimally treated with en bloc resection. Although en bloc resection is the gold standard for treatment of mobile spinal chordoma, tumor location, size, and extent of involvement frequently complicate the achievement of negative margins. In particular, chordoma involving the thoracic region can require a challenging anterior access, and en bloc resection can lead to a highly destabilized spine.

OBSERVATIONS

Modern technological advances make en bloc resection more technically feasible than ever before. In this case, the successful en bloc resection of a particularly complex cervicothoracic junction chordoma was facilitated by a multidisciplinary surgical approach that maximized the use of intraoperative computed tomography–guided spinal navigation and patient-specific three-dimensional–printed modeling.

LESSONS

The authors review the surgical planning and specific techniques that facilitated the successful en bloc resection of this right-sided chordoma via image-guided parasagittal osteotomy across 2 stages. The integration of emerging visualization technologies into complex spinal column tumor management may help to provide optimal oncological care for patients with challenging primary tumors of the mobile spine.

Accuracy of Placement of Pedicle Screws in the Lumbosacral Region of Dogs Using 3D-Printed Patient-Specific Drill Guides

OBJECTIVE

 The aim of this study was to report the accuracy of pedicle screw placement using three-dimensional (3D)-printed, patient-specific drill guides in the lumbosacral region of dogs.

STUDY DESIGN

 This was a retrospective study. Thirty-two pedicle screws were placed in five dogs. Medical records were reviewed between November 2015 and November 2018 for dogs showing clinical signs associated with cauda equina syndrome. Inclusion criteria included preoperative magnetic resonance imaging, pre- and postoperative computed tomography (CT) and dorsal stabilization, with pedicle screws placed using 3D-printed, patient-specific drill guides and polymethylmethacrylate. Screw placement was evaluated for medial or lateral breaching on postoperative CT.

RESULTS

 Five dogs met the inclusion criteria. Four had degenerative lumbosacral stenosis and one had discospondylitis. All dogs had failed medical management prior to surgery. Of 32 bicortical pedicle screws placed, 30 were fully contained inside the pedicle and 2 were partially breaching the vertebral canal (less than one-third of the screw diameter). Postoperative CT revealed good alignment of L7-S1 in all planes.

CONCLUSION

 This technique enabled an accurate and safe placement of pedicle screws in the lumbosacral region of dogs with lumbosacral disease. Three-dimensional, printed patient-specific drill guides are a safe and effective method of placing pedicle screws in dogs with lumbosacral disease.

Three-dimensional Printed Drill Guides Versus Fluoroscopic-guided Freehand Technique for Pedicle Screw Placement: A Systematic Review and Meta-analysis of Radiographic, Operative, and Clinical Outcomes

STUDY DESIGN

A systematic review and meta-analysis.

OBJECTIVE

The objective of this study was to compare surgical, clinical, and radiographic outcomes of 3-dimensional printed (3DP) drill guides to the fluoroscopic-guided, freehand placement of pedicle screws in the spine.

SUMMARY OF BACKGROUND DATA

3DP is a budding technology in spine surgery and has recently been applied to patient-specific drill guides for pedicle screw placement. Several authors have reported the benefits of these drill guides, but no clear consensus exists on their utility.

MATERIALS AND METHODS

A comprehensive search of the literature was conducted and independent reviewers assessed eligibility for included studies. Outcomes analyzed included: total operation time, estimated blood loss, screw accuracy, pain score, Japanese Orthopedic Association score, and postoperative complications. Weighted mean differences (WMD) and weighted risk differences were calculated using a random-effects model.

RESULTS

Six studies with a total of 205 patients were included. There were significantly lower operation times [WMD=-32.32 min, 95% confidence interval (CI)=-53.19 to -11.45] and estimated blood loss (WMD=-51.42 mL, 95% CI=-81.12 to -21.72) in procedures performed with 3DP drill guides as compared with freehand technique. The probability of "excellent" screw placement was significantly higher in 3DP guides versus freehand (weighted risk difference=-0.12, 95% CI=-0.17 to 0.07); however, no differences were observed in "poor" or "good" screw placement. There were no significant differences between groups in pain scores or Japanese Orthopedic Association scores. No difference in the rate of surgical complications was noted between the groups.

CONCLUSIONS

Pedicle screws placed with 3DP drill guides may result in shorter operative time, less blood loss, and a greater probability of excellent screw placement as compared with those placed with freehand techniques. We conclude that 3DP guides may potentially develop into an efficient and accurate option for pedicle screw placement. However, more prospective, randomized controlled trials are needed to strengthen the confidence of these conclusions.

LEVEL OF EVIDENCE

Level III.

Three-Dimensional Printed Anatomic Modeling for Surgical Planning and Real-Time Operative Guidance in Complex Primary Spinal Column Tumors: Single-Center Experience and Case Series

OBJECTIVE

Three-dimensional (3D) printing has emerged as a visualization tool for clinicians and patients. We sought to use patient-specific 3D-printed anatomic modeling for preoperative planning and live intraoperative guidance in a series of complex primary spine tumors.

METHODS

Over 9 months, patients referred to a single neurosurgical provider for complex primary spinal column tumors were included. Most recent spinal magnetic resonance and computed tomography (CT) imaging were semiautomatically segmented for relevant anatomy and models were printed using polyjet multicolor printing technology. Models were available to surgical teams before and during the operative procedure. Patients also viewed the models preoperatively during surgeon explanation of disease and surgical plan to aid in their understanding.

RESULTS

Tumor models were prepared for 9 patients, including 4 with chordomas, 2 with schwannomas, 1 with osteosarcoma, 1 with chondrosarcoma, and 1 with Ewing-like sarcoma. Mean age was 50.7 years (range, 15-82 years), including 6 males and 3 females. Mean tumor volume was 129.6 cm³ (range, 3.3-250.0 cm³). Lesions were located at cervical, thoracic, and sacral levels and were treated by various surgical approaches. Models were intraoperatively used as patient-specific anatomic references throughout 7 cases and were found to be technically useful by the surgical teams.

CONCLUSIONS

We present the largest case series of 3D-printed spine tumor models reported to date. 3D-printed models are broadly useful for operative planning and intraoperative guidance in spinal oncology surgery.

Investigation of a three-dimensional printed dynamic cervical spine model for anatomy and physiology education

INTRODUCTION

Three-dimensional (3D) printing of anatomical structures is a growing method of education for students and medical trainees. These models are generally produced as static representations of gross surface anatomy. In order to create a model that provides educators with a tool for demonstration of kinematic and physiologic concepts in addition to surface anatomy, a high-resolution segmentation and 3D-printingtechnique was investigated for the creation of a dynamic educational model.

METHODS

An anonymized computed tomography scan of the cervical spine with a diagnosis of ossification of the posterior longitudinal ligament was acquired. Using a high-resolution thresholding technique, the individual facet and intervertebral spaces were separated, and models of the C3-7 vertebrae were 3D-printed. The models were placed on a myelography simulator and subjected to flexion and extension under fluoroscopy, and measurements of the spinal canal diameter were recorded and compared to in-vivo measurements. The flexible 3D-printed model was then compared to a static 3D-printed model to determine the educational benefit of demonstrating physiologic concepts.

RESULTS

The canal diameter changes on the flexible 3D-printed model accurately reflected in-vivo measurements during dynamic positioning. The flexible model also was also more successful in teaching the physiologic concepts of spinal canal changes during flexion and extension than the static 3D-printed model to a cohort of learners.

CONCLUSIONS

Dynamic 3D-printed models can provide educators with a cost-effective and novel educational tool for not just instruction of surface anatomy, but also physiologic concepts through 3D ex-vivo modeling of case-specific physiologic and pathologic conditions.

Impact of 3D Printed Calcaneal Models on Fracture Understanding and Confidence in Orthopedic Surgery Residents

OBJECTIVE

To determine if three-dimensionally printed (3Dp) fracture models can improve orthopedic trainee education.

DESIGN

A prospective comparison study of orthopedic trainees and attending surgeons was performed, where a range of calcaneal fractures were used for creating anonymized 3Dp models. Study participants rotated through workstations viewing computed tomography images and either a digital 3D volume rendering or 3Dp model of the fractured calcaneus. Diagnosis, time for evaluation, confidence of fracture understanding, perceived model accuracy, and proposed treatment were compared using a standardized questionnaire.

PARTICIPANTS

Sixteen resident trainees and 5 attending surgeons participated in this study. Attending surgeons were required to have fellowship training in trauma or foot and ankle surgery and manage calcaneal fractures as part of their current practice.

RESULTS

Junior residents had the slowest time of assessment (mean = 121 ± 54 seconds) and lowest percentage of correct diagnoses (69%), although these findings did not reach significance compared to the other residency years. Residents displayed higher levels of confidence in fracture understanding with increasing residency year of training (p < 0.0001), and this confidence was greater for cases that included a 3Dp model (p < 0.03). Perceived accuracy of cases with 3Dp models was significantly higher than cases without 3Dp models (7.0 vs 5.5 p < 0.001).

CONCLUSIONS

This study found that 3Dp models increase the perceived accuracy of fracture assessment, though no statistically significant improvement in diagnostic accuracy was observed. The 3Dp models did improve trainee confidence, although this effect diminished with increasing residency year. In orthopedic residency training programs, 3Dp models of complex fractures can be a valuable educational tool, especially for junior trainees.

Medical Three-Dimensional Printing in Zoological Medicine

Medical 3-dimensional printing allows the creation of anatomic models by using a sequence of computer software programs. Diagnostic imaging data are used to create a physical model that allows clinicians to plan for surgical procedures and create prosthetics and surgical implants and instruments, among other applications. Its use in zoological medicine is limited, but is an area with a great growth potential. This publication reviews the process of creating a 3-dimensional anatomic model, its application in human and small animal medicine and surgery, and reviews peer-reviewed data regarding its use in exotic animals, wildlife, and zoo animals.

Accuracy of placement of pedicle screws in the thoracolumbar spine of dogs with spinal deformities with three-dimensionally printed patient-specific drill guides

OBJECTIVE

To determine the accuracy of pedicle screw placement in the thoracic spine of dogs with spinal deformities with three-dimensionally (3D) printed patient-specific drill guides.

STUDY DESIGN

Retrospective study.

SAMPLE POPULATION

Six dogs in which sixty pedicle screws were placed in the thoracolumbar spine.

METHODS

Medical records were searched between June 2017 and June 2018 for dogs with clinical signs associated with a thoracolumbar vertebral malformation. Inclusion criteria included MRI and computed tomography (CT) data that were used to create 3D printed patient-specific drill guides. All dogs were stabilized dorsally with guided bicortical pedicle screws and polymethylmethacrylate. Accuracy of screw placement was assessed by immediately postoperative CT according to a modified Zdichavsky classification.

RESULTS

Five pugs and one French bulldog met the inclusion criteria. Sixty bicortical pedicle screws were placed; 96.7% were graded as I (optimal placement), and 3.3% were classified as IIa (partial penetration of the medial pedicle wall) according to a modified Zdichavsky classification.

CONCLUSION

Three-dimensionally printed patient-specific drill guides allowed safe and accurate placement of pedicle screws in the thoracolumbar spine in dogs with vertebral malformation.

CLINICAL SIGNIFICANCE

Three-dimensionally printed patient-specific drill guides are a safe and effective method of placing pedicle screws in dogs with thoracolumbar vertebral malformations.

Usefulness of 3D Printed Models in the Management of Complex Craniovertebral Junction Anomalies: Choice of Treatment Strategy, Design of Screw Trajectory, and Protection of Vertebral Artery

OBJECTIVE

To evaluate the usefulness of 3-dimensional (3D) printed models as an aid for the treatment of complex CVJ anomalies.

METHODS

3D printed models were fabricated for 21 patients with complex CVJ anomalies, including vertebral artery anomaly, thin C2 pedicle, vertical atlantoaxial facet joint, or rotational dislocation combined with atlantoaxial dislocation and basilar invagination. Preoperative planning, surgical simulation, and intraoperative reference were achieved using the 3D model during the surgical treatment. The usefulness of 3D printed models, and postoperative clinical and radiological outcomes were assessed.

RESULTS

Direct posterior reduction and atlantoaxial fixation were achieved in 19 patients. Transoral odontoidectomy followed by posterior fixation was implemented for 2 patients with vertical facet joint and rotational dislocation. All screws were safely inserted with no complication, and 90% patients achieved a >60% reduction of both horizontal and vertical dislocation. Clinical symptoms improved in all patients, with the averaged Japanese Orthopedic Association scores increasing from 11.14 to 14.43 (P < 0.01).

CONCLUSIONS

The patient-specific 3D printed model would be an effective tool for evaluation of the reducibility of the atlantoaxial dislocation and basilar invagination, decision making in choosing the optimal surgical approach and way of fixation, and precise placement of the screw while protecting the vertebral artery and spinal cord. The risk of neurovascular injury was minimized, and encouraging outcomes were achieved with the aid of this technique.

The Role of 3D Printing in Medical Applications: A State of the Art

Three-dimensional (3D) printing refers to a number of manufacturing technologies that generate a physical model from digital information. Medical 3D printing was once an ambitious pipe dream. However, time and investment made it real. Nowadays, the 3D printing technology represents a big opportunity to help pharmaceutical and medical companies to create more specific drugs, enabling a rapid production of medical implants, and changing the way that doctors and surgeons plan procedures. Patient-specific 3D-printed anatomical models are becoming increasingly useful tools in today's practice of precision medicine and for personalized treatments. In the future, 3D-printed implantable organs will probably be available, reducing the waiting lists and increasing the number of lives saved. Additive manufacturing for healthcare is still very much a work in progress, but it is already applied in many different ways in medical field that, already reeling under immense pressure with regards to optimal performance and reduced costs, will stand to gain unprecedented benefits from this good-as-gold technology. The goal of this analysis is to demonstrate by a deep research of the 3D-printing applications in medical field the usefulness and drawbacks and how powerful technology it is.

[Accuracy analysis and clinical application of the progressive navigation template system to assist atlas-axial pedicle screw placement]

Objective

To investigate the accuracy of progressive three-dimensional navigation template system (abbreviated as progressive template) to assist atlas-axial pedicle screw placement.

Methods

The clinical data of 33 patients with atlas-axial posterior internal fixation surgery between May 2015 and May 2017 were retrospectively analyzed. According to the different methods of auxiliary screw placement, the patients were divided into trial group (19 cases, screw placement assisted by progressive template) and control group (14 cases, screw placement assisted by single navigation template system, abbreviated as initial navigation template). There was no significant difference in gender, age, cause of injury, damage segments, damage types, and preoperative Frankel classification between the two groups ( P>0.05). The operation time and intraoperative blood loss of the two groups were compared. The safety of screw placement was evaluated on postoperative CT by using the method from Kawaguchi et al, the deviation of screw insertion point were calculated, the angular deviation of the nailing on coordinate systems XOZ, XOY, YOZ were calculated according to Peng's method.

Results

All patients completed the operation successfully; the operation time and intraoperative blood loss in the trial group were significantly less than those in the control group ( t=-2.360, P=0.022; t=-3.006, P=0.004). All patients were followed up 12-40 months (mean, 25.3 months). There was no significant vascular injury or nerve injury aggravation. Postoperative immediate X-ray film and CT showed the dislocation was corrected. Postoperative immediate CT showed that all 76 screws were of grade 0 in the trial group, and the safety of screw placement was 100%; 51 screws were of grade 0, 3 of gradeⅠ, and 2 of gradeⅡ in the control group, and the safety of screw placement was 91.1%; there was significant difference in safety of screw placement between the two groups ( χ ²=7.050, P=0.030). The screw insertion point deviation and angular deviation of the nailing on XOY and YOZ planes in the trial group were significantly less than those in the control group ( P<0.05). There was no significant difference in angular deviation of the nailing on XOZ between the two groups ( t=1.060, P=0.290).

Conclusion

Compared with the initial navigation template, the progressive navigation template assisting atlas-axial pedicle screw placement to treat atlas-axial fracture with dislocation, can reduce operation time and intraoperative blood loss, improve the safety of screw placement, and match the preoperative design more accurately.

Radiological Society of North America (RSNA) 3D printing Special Interest Group (SIG): guidelines for medical 3D printing and appropriateness for clinical scenarios

Medical three-dimensional (3D) printing has expanded dramatically over the past three decades with growth in both facility adoption and the variety of medical applications. Consideration for each step required to create accurate 3D printed models from medical imaging data impacts patient care and management. In this paper, a writing group representing the Radiological Society of North America Special Interest Group on 3D Printing (SIG) provides recommendations that have been vetted and voted on by the SIG active membership. This body of work includes appropriate clinical use of anatomic models 3D printed for diagnostic use in the care of patients with specific medical conditions. The recommendations provide guidance for approaches and tools in medical 3D printing, from image acquisition, segmentation of the desired anatomy intended for 3D printing, creation of a 3D-printable model, and post-processing of 3D printed anatomic models for patient care.

The Role of Three-Dimensional Printing in Contemporary Vascular and Endovascular Surgery: A Systematic Review

BACKGROUND

Three-dimensional (3D) printing, also known as rapid prototyping or additive manufacturing, is a novel adjunct in the medical field. The aim of this systematic review is to evaluate the role of 3D printing technology in the field of contemporary vascular surgery in terms of its technical aspect, practicability, and clinical outcome.

METHODS

A systematic search of literatures published from January 1, 1980 to July 15, 2017 was identified from the EMBASE, MEDLINE, and Cochrane library database with reference to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guideline. The predefined selection inclusion criterion was clinical application of 3D printing technology in vascular surgery of large and small vessel pathology.

RESULTS

Forty-two articles were included in this systematic review, including 2 retrospective cohorts and 1 prospective case control study. 3D printing was mostly applied to abdominal aortic aneurysm (n = 20) and thoracic aorta pathology (n = 8), other vessels included celiac, splenic, carotid, subclavian, femoral artery, and portal vein (n = 10). The most commonly quoted materials were acrylonitrile-butadiene-styrene (n = 2), polylactic acid (n = 4), polyurethane resin (n = 3) and nylon (n = 3). The cost per replica ranged from USD $4-2,360. Cost for a commercial printer was around USD $2,210-50,000.

CONCLUSION

3D printing was recognized and gradually incorporated as a useful adjunct in the field of vascular and endovascular surgery. The production of an accurate anatomic patient-specific replica was shown to bring significant impact in patient management in terms of anatomic understanding, procedural planning, and intraoperative navigation, education, and academic research as well as patient communication. Further analysis on cost-effectiveness was indicated to guide decisions on applicability of such promising technology on a routine basis.

Additive manufacturing applications in orthopaedics: A review

The applications of Additive Manufacturing (AM) have increased extensively in the area of orthopaedics. The AM applications are for making anatomic models, surgical instruments & tool design, splints, implants and prosthesis. A brief review of various research articles shows that patient-specific orthopaedic procedures provide multiple applications areas and provide directions for future developments. The purpose of this paper is to identify the best possible usage of additive manufacturing applications in orthopaedics field. It also presents the steps used to prepare a 3D printed model by using this technology and details applications in the field of orthopaedics. AM gives a flexible solution in orthopaedics area, where customised implants can be formed as per the required shape and size and can help substitution with customised products. A 3D model created by this technology gain an accurate perception of patient's anatomy which is used to perform mock surgeries and is helpful for highly complex surgical pathologies. It makes surgeon's job accessible and increases the success rate of the operation. AM provides a perfect fit implant for the specific patient by unlimited geometric freedom. Various scanning technologies capture the status of bone defects, and printing of the model is done with the help of this technology. It gives an exact generation of a physical model which is also helpful for medical education, surgical planning and training. This technology can help to solve present-day challenges as data of every patient is different from another.

3D Printing Applications in Minimally Invasive Spine Surgery

3D printing (3DP) technology continues to gain popularity among medical specialties as a useful tool to improve patient care. The field of spine surgery is one discipline that has utilized this; however, information regarding the use of 3DP in minimally invasive spine surgery (MISS) is limited. 3D printing is currently being utilized in spine surgery to create biomodels, hardware templates and guides, and implants. Minimally invasive spine surgeons have begun to adopt 3DP technology, specifically with the use of biomodeling to optimize preoperative planning. Factors limiting widespread adoption of 3DP include increased time, cost, and the limited range of diagnoses in which 3DP has thus far been utilized. 3DP technology has become a valuable tool utilized by spine surgeons, and there are limitless directions in which this technology can be applied to minimally invasive spine surgery.

Systematic review of 3D printing in spinal surgery: the current state of play

Three-dimensional printing (3DP), also known as "Additive Manufacturing", is a rapidly growing industry, particularly in the area of spinal surgery. Given the complex anatomy of the spine and delicate nature of surrounding structures, 3DP has the potential to aid surgical planning and procedural accuracy. We perform a systematic review of current literature on the applications of 3DP in spinal surgery. Six electronic databases were searched for original published studies reporting cases or outcomes for 3DP surgical models, guides or implants for spinal surgery. The findings of these studies were synthesized and summarized. These searches returned a combined 2,411 articles. Of these, 54 were included in this review. 3DP is currently used for surgical planning, intra-operative surgical guides, customised prostheses as well as "Off-the-Shelf" implants. The technology has the potential for enhanced implant properties, as well as decreased surgical time and better patient outcomes. The majority of the data thus far is from low-quality studies with inherent biases linked with the excitement of a new field. As the body of literature continues to expand, larger scale studies to evaluate advantages and disadvantages, and longer-term follow up will enhance our knowledge of the effect 3DP has in spinal surgery. In addition, issues such as financial impact, time to design and print, materials selection and bio-printing will evolve as this rapidly expanding field matures.

The application of 3-dimensional printing for preoperative planning in oral and maxillofacial surgery in dogs and cats

OBJECTIVE

To describe the application of 3-dimensional (3D) printing in advanced oral and maxillofacial surgery (OMFS) and to discuss the benefits of this modality in surgical planning, student and resident training, and client education.

STUDY DESIGN

Retrospective case series.

ANIMALS

Client-owned dogs (n = 28) and cats (n = 4) with 3D printing models of the skulls.

METHODS

The medical records of 32 cases with 3D printing prior to major OMFS were reviewed.

RESULTS

Indications for 3D printing included preoperative planning for mandibular reconstruction after mandibulectomy (n = 12 dogs) or defect nonunion fracture (n = 6 dogs, 2 cats), mapping of ostectomy location for temporomandibular joint ankylosis or pseudoankylosis (n = 4 dogs), assessment of palatal defects (n = 2 dogs, 1 cat), improved understanding of complex anatomy in cases of neoplasia located in challenging locations (n = 2 dogs, 1 cat), and in cases of altered anatomy secondary to trauma (n = 2 dogs).

CONCLUSION

In the authors' experience, 3D printed models serve as excellent tools for OMFS planning and resident training. Furthermore, 3D printed models are a valuable resource to improve clients' understanding of the pet's disorder and the recommended treatment.

CLINICAL RELEVANCE

Three-dimensional printed models should be considered viable tools for surgical planning, resident training, and client education in candidates for complex OMFS.

Surgical applications of three-dimensional printing: a review of the current literature & how to get started

Three dimensional (3D) printing involves a number of additive manufacturing techniques that are used to build structures from the ground up. This technology has been adapted to a wide range of surgical applications at an impressive rate. It has been used to print patient-specific anatomic models, implants, prosthetics, external fixators, splints, surgical instrumentation, and surgical cutting guides. The profound utility of this technology in surgery explains the exponential growth. It is important to learn how 3D printing has been used in surgery and how to potentially apply this technology. PubMed was searched for studies that addressed the clinical application of 3D printing in all surgical fields, yielding 442 results. Data was manually extracted from the 168 included studies. We found an exponential increase in studies addressing surgical applications for 3D printing since 2011, with the largest growth in craniofacial, oromaxillofacial, and cardiothoracic specialties. The pertinent considerations for getting started with 3D printing were identified and are discussed, including, software, printing techniques, printing materials, sterilization of printing materials, and cost and time requirements. Also, the diverse and increasing applications of 3D printing were recorded and are discussed. There is large array of potential applications for 3D printing. Decreasing cost and increasing ease of use are making this technology more available. Incorporating 3D printing into a surgical practice can be a rewarding process that yields impressive results.

Applications of 3D printing in the management of severe spinal conditions

The latest and fastest-growing innovation in the medical field has been the advent of three-dimensional printing technologies, which have recently seen applications in the production of low-cost, patient-specific medical implants. While a wide range of three-dimensional printing systems has been explored in manufacturing anatomical models and devices for the medical setting, their applications are cutting-edge in the field of spinal surgery. This review aims to provide a comprehensive overview and classification of the current applications of three-dimensional printing technologies in spine care. Although three-dimensional printing technology has been widely used for the construction of patient-specific anatomical models of the spine and intraoperative guide templates to provide personalized surgical planning and increase pedicle screw placement accuracy, only few studies have been focused on the manufacturing of spinal implants. Therefore, three-dimensional printed custom-designed intervertebral fusion devices, artificial vertebral bodies and disc substitutes for total disc replacement, along with tissue engineering strategies focused on scaffold constructs for bone and cartilage regeneration, represent a set of promising applications towards the trend of individualized patient care.