3D Printing in Spine Surgery

Evaluating the efficacy and suggesting technical optimizations for endoscopic lumbar interbody fusion across different lumbar spondylolisthesis types

Purpose

To evaluate the efficacy of the endoscopic lumbar interbody fusion technique across different types of lumbar spondylolisthesis, specifically Grade I and Grade II, and suggest technical optimizations based on therapeutic outcomes, complications, and patient satisfaction for both grades.

Methods

We analyzed data from 57 L4 to 5 spondylolisthesis patients, all categorized as either Grade I or Grade II, comprising 31 males and 26 females. Of these, 36 were diagnosed with Grade I and 21 with Grade II. All subjects underwent the endoscopic lumbar interbody fusion procedure. Primary evaluation metrics included pre and post-operative Vasual Analogue Scale（VAS） pain scores, Osewewtry Disability Index（ODI） functional scores, surgical duration, intraoperative blood loss, degree of spondylolisthesis correction, complications, and patient satisfaction levels.

Results

At a minimum of 6 months post-operation, the VAS score for the Grade I cohort reduced from an initial 7.30 ± 0.69 to 2.97 ± 0.47, while the Grade II cohort saw a decrease from 7.53 ± 0.56 to 3.37 ± 0.62 (P = 0.0194). The ODI score in the Grade I group declined from 66.88 ± 5.15 % pre-operation to 29.88 ± 6.36 % post-operation, and in the Grade II group, it decreased from 69.33 ± 5.27 % to 34.66 ± 6.01 % (P = 0.0092). The average surgical duration for the Grade I group stood at 155.72 ± 17.75 min, compared to 180.38 ± 14.72 min for the Grade II group (P < 0.001). The mean intraoperative blood loss for the Grade I group was 144.58 ± 28.61 ml, whereas the Grade II group registered 188.23 ± 9.41 ml (P < 0.001). Post-surgery, 83 % of the Grade I patients achieved a correction degree exceeding 80 %, and 61 % of the Grade II patients surpassed 50 % (P = 0.0055). Complication rates were recorded at 8 % for Grade I and 16 % for Grade II. Patient satisfaction reached 94 % in the Grade I cohort and 90 % in the Grade II cohort.

Conclusion

Endoscopic lumbar interbody fusion showcases promising therapeutic outcomes for both Grade I and Grade II lumbar spondylolisthesis. However, surgeries for Grade II spondylolisthesis tend to be lengthier, more challenging, involve greater blood loss, and have a heightened complication risk. Tailored technical adjustments and enhancements are essential for addressing the distinct spondylolisthesis types.

Fabrication of a composite 3D-printed titanium alloy combined with controlled in situ drug release to prevent osteosarcoma recurrence

Osteosarcoma is a malignant bone tumor occurring in adolescents. Surgery combined with adjuvant or neoadjuvant chemotherapy is the standard treatment. However, systemic chemotherapy is associated with serious side effects and a high risk of postoperative tumor recurrence, leading to a high amputation rate and mortality in cancer patients. Implant materials that can simultaneously repair large bone defects and prevent osteosarcoma recurrence are in urgent need. Herein, an intelligent system comprising 3D-printed titanium scaffold (TS) and pH-responsive PEGylated paclitaxel prodrugs was fabricated for bone defect reconstruction and recurrence prevention following osteosarcoma surgery. The drug-loaded implants exhibited excellent stability and biocompatibility for supporting the activity of bone stem cells under normal body fluid conditions and the rapid release of drugs in response to faintly acidic environments. An in vitro study demonstrated that five human osteosarcoma cell lines could be efficiently eradicated by paclitaxel released in an acidic microenvironment. Using mice models, we demonstrated that the drug-loaded TS can enable a pH-responsive treatment of postoperative tumors and effectively prevent osteosarcoma recurrence. Therefore, local implantation of this composite scaffold may be a promising topical therapeutic method to prevent osteosarcoma recurrence.

The Changing Environment in Postgraduate Education in Orthopedic Surgery and Neurosurgery and Its Impact on Technology-Driven Targeted Interventional and Surgical Pain Management: Perspectives from Europe, Latin America, Asia, and The United States

Personalized care models are dominating modern medicine. These models are rooted in teaching future physicians the skill set to keep up with innovation. In orthopedic surgery and neurosurgery, education is increasingly influenced by augmented reality, simulation, navigation, robotics, and in some cases, artificial intelligence. The postpandemic learning environment has also changed, emphasizing online learning and skill- and competency-based teaching models incorporating clinical and bench-top research. Attempts to improve work-life balance and minimize physician burnout have led to work-hour restrictions in postgraduate training programs. These restrictions have made it particularly challenging for orthopedic and neurosurgery residents to acquire the knowledge and skill set to meet the requirements for certification. The fast-paced flow of information and the rapid implementation of innovation require higher efficiencies in the modern postgraduate training environment. However, what is taught typically lags several years behind. Examples include minimally invasive tissue-sparing techniques through tubular small-bladed retractor systems, robotic and navigation, endoscopic, patient-specific implants made possible by advances in imaging technology and 3D printing, and regenerative strategies. Currently, the traditional roles of mentee and mentor are being redefined. The future orthopedic surgeons and neurosurgeons involved in personalized surgical pain management will need to be versed in several disciplines ranging from bioengineering, basic research, computer, social and health sciences, clinical study, trial design, public health policy development, and economic accountability. Solutions to the fast-paced innovation cycle in orthopedic surgery and neurosurgery include adaptive learning skills to seize opportunities for innovation with execution and implementation by facilitating translational research and clinical program development across traditional boundaries between clinical and nonclinical specialties. Preparing the future generation of surgeons to have the aptitude to keep up with the rapid technological advances is challenging for postgraduate residency programs and accreditation agencies. However, implementing clinical protocol change when the entrepreneur-investigator surgeon substantiates it with high-grade clinical evidence is at the heart of personalized surgical pain management.

Imaging of low-energy vertebral fractures

Low-energy vertebral fractures pose a diagnostic challenge for the radiologist due to their often-inadvertent nature and often subtle imaging semiology. However, the diagnosis of this type of fractures can be decisive, not only because it allows targeted treatment to prevent complications, but also because of the possibility of diagnosing systemic pathologies such as osteoporosis or metastatic disease. Pharmacological treatment in the first case has been shown to prevent the development of other fractures and complications, while percutaneous treatments and various oncological therapies can be an alternative in the second case. Therefore, it is necessary to know the epidemiology and typical imaging findings of this type of fractures. The objective of this work is to review the imaging diagnosis of low-energy fractures, with special emphasis on the characteristics that should be outlined in the radiological report to guide a specific diagnosis that favours and optimizes the treatment of patients suffering of low energy fractures.

Artificial lamina after laminectomy: Progress, applications, and future perspectives

In clinical practice, laminectomy is a commonly used procedure for spinal decompression in patients suffering from spinal disorders such as ossification of ligamentum flavum, lumbar stenosis, severe spinal fracture, and intraspinal tumors. However, the loss of posterior column bony support, the extensive proliferation of fibroblasts and scar formation after laminectomy, and other complications (such as postoperative epidural fibrosis and iatrogenic instability) may cause new symptoms requiring revision surgery. Implantation of an artificial lamina prosthesis is one of the most important methods to avoid post-laminectomy complications. Artificial lamina is a type of synthetic lamina tissue made of various materials and shapes designed to replace the resected autologous lamina. Artificial laminae can provide a barrier between the dural sac and posterior soft tissues to prevent postoperative epidural fibrosis and paravertebral muscle compression and provide mechanical support to maintain spinal alignment. In this paper, we briefly review the complications of laminectomy and the necessity of artificial lamina, then we review various artificial laminae from clinical practice and laboratory research perspectives. Based on a combination of additive manufacturing technology and finite element analysis for spine surgery, we propose a new designing perspective of artificial lamina for potential use in clinical practice.

Investigating the accuracy of mandibulectomy and reconstructive surgery using 3D customized implants and surgical guides in a rabbit model

BACKGROUND

This study aimed to analyze the accuracy of the output of three-dimensional (3D) customized surgical guides and titanium implants in a rabbit model, and of mandibulectomy, reconstructive surgery, and surgical outcome; additionally, the correlation between surgical accuracy and surgical outcomes, including the differences in surgical outcome according to surgical accuracy, was analyzed.

RESULTS

The output of implants was accurately implemented within the error range (- 0.03-0.03 mm), and the surgical accuracy varied depending on the measured area (range - 0.4-1.1 mm). Regarding surgical outcomes, angle between the mandibular lower borders showed the most sensitive results and distance between the lingual cusps of the first molars represented the most accurate outcomes. A significant correlation was noted between surgical accuracy in the anteroposterior length of the upper borders pre- and postoperatively and the angle between the mandibular lower borders (regression coefficient = 0.491, p = 0.028). In the group wherein surgery was performed more accurately, the angle between the mandibular lower borders was reproduced more accurately (p = 0.021). A selective laser melting machine accurately printed the implants as designed. Considering the positive correlation among surgical accuracy in the mandibular upper borders, angle between the mandibular lower borders, and more accurately reproduced angle between the mandibular lower borders, the angle between the mandibular lower borders is considered a good indicator for evaluating the outcomes of reconstructive surgery.

CONCLUSION

To reduce errors in surgical outcomes, it is necessary to devise a positioner for the surgical guide and design a 3D surgical guide to constantly maintain the direction of bone resection. A fixed area considering the concept of three-point fixation should be selected for stable positioning of the implant; in some cases, bilateral cortical bone fixation should be considered. The angle between the mandibular lower borders is a sensitive indicator for evaluating the outcomes of reconstructive surgery.

Three-dimensional printing and 3D slicer powerful tools in understanding and treating neurosurgical diseases

With the development of the 3D printing industry, clinicians can research 3D printing in preoperative planning, individualized implantable materials manufacturing, and biomedical tissue modeling. Although the increased applications of 3D printing in many surgical disciplines, numerous doctors do not have the specialized range of abilities to utilize this exciting and valuable innovation. Additionally, as the applications of 3D printing technology have increased within the medical field, so have the number of printable materials and 3D printers. Therefore, clinicians need to stay up-to-date on this emerging technology for benefit. However, 3D printing technology relies heavily on 3D design. 3D Slicer can transform medical images into digital models to prepare for 3D printing. Due to most doctors lacking the technical skills to use 3D design and modeling software, we introduced the 3D Slicer to solve this problem. Our goal is to review the history of 3D printing and medical applications in this review. In addition, we summarized 3D Slicer technologies in neurosurgery. We hope this article will enable many clinicians to leverage the power of 3D printing and 3D Slicer.

Virtual Scoliosis Surgery Using a 3D-Printed Model Based on Biplanar Radiographs

The aim of this paper is to describe a protocol that simulates the spinal surgery undergone by adolescents with idiopathic scoliosis (AIS) by using a 3D-printed spine model. Patients with AIS underwent pre- and postoperative bi-planar low-dose X-rays from which a numerical 3D model of their spine was generated. The preoperative numerical spine model was subsequently 3D printed to virtually reproduce the spine surgery. Special consideration was given to the printing materials for the 3D-printed elements in order to reflect the radiopaque and mechanical properties of typical bones most accurately. Two patients with AIS were recruited and operated. During the virtual surgery, both pre- and postoperative images of the 3D-printed spine model were acquired. The proposed 3D-printing workflow used to create a realistic 3D-printed spine suitable for virtual surgery appears to be feasible and reliable. This method could be used for virtual-reality scoliosis surgery training incorporating 3D-printed models, and to test surgical instruments and implants.

Clinical applications and prospects of 3D printing guide templates in orthopaedics

Background

With increasing requirements for medical effects, and huge differences among individuals, traditional surgical instruments are difficult to meet the patients' growing medical demands. 3D printing is increasingly mature, which connects to medical services critically as well. The patient specific surgical guide plate provides the condition for precision medicine in orthopaedics.

Methods

In this paper, a systematic review of the orthopedic guide template is presented, where the history of 3D-printing-guided technology, the process of guides, and basic clinical applications of orthopedic guide templates are described. Finally, the limitations of the template and possible future directions are discussed.

Results

The technology of 3D printing surgical templates is increasingly mature, standard, and intelligent. With the help of guide templates, the surgeon can easily determine the direction and depth of the screw path, and choose the angle and range of osteotomy, increasing the precision, safety, and reliability of the procedure in various types of surgeries. It simplifies the difficult surgical steps and accelerates the growth of young and mid-career physicians. But some problems such as cost, materials, and equipment limit its development.

Conclusions

In different fields of orthopedics, the use of guide templates can significantly improve surgical accuracy, shorten the surgical time, and reduce intraoperative bleeding and radiation. With the development of 3D printing, the guide template will be standardized and simplified from design to production and use. 3D printing guides will be further sublimated in the application of orthopedics and better serve the patients.

The translational potential of this paper

Precision, intelligence, and individuation are the future development direction of orthopedics. It is more and more popular as the price of printers falls and materials are developed. In addition, the technology of meta-universe, digital twin, and artificial intelligence have made revolutionary effects on template guides. We aim to summarize recent developments and applications of 3D printing guide templates for engineers and surgeons to develop more accurate and efficient templates.

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.

Clinical Application of a 3D-Printed Positioning Module and Navigation Template for Percutaneous Vertebroplasty

BACKGROUND

This study aimed to evaluate a personalized 3D-printed percutaneous vertebroplasty positioning module and navigation template based on preoperative CT scan data that was designed to treat patients with vertebral compression fractures caused by osteoporosis.

METHODS

A total of 22 patients with vertebral compression fractures admitted to our hospital were included in the study. Positioning was performed with the new 3D-printed positioning module, and the navigation template was used for patients in the experimental group, and the traditional perspective method was used for patients in the control group. The experimental group consisted of 11 patients, 2 males and 9 females, with a mean age of 67.27 ± 11.86 years (range: 48 to 80 years), and the control group consisted of 11 patients, 3 males and 8 females, with a mean age of 74.27 ± 7.24 years (range: 63 to 89 years). The puncture positioning duration, number of intraoperative fluoroscopy sessions, and preoperative and postoperative visual analog scale (VAS) scores were statistically analyzed in both groups.

RESULTS

The experimental group had shorter puncture positioning durations and fewer intraoperative fluoroscopy sessions than the control group, and the differences were statistically significant (P < .05). There were no significant differences in age or preoperative or postoperative VAS scores between the two groups (P > .05).

CONCLUSIONS

The new 3D-printed vertebroplasty positioning module and navigation template shortened the operation time and reduced the number of intraoperative fluoroscopy sessions. It also reduced the difficulty in performing percutaneous vertebroplasty and influenced the learning curve of senior doctors learning this operation to a certain degree.

Advances in the application of mesenchymal stem cells, exosomes, biomimetic materials, and 3D printing in osteoporosis treatment

Owing to an increase in the aging population, osteoporosis has become a severe public health concern, with a high prevalence among the elderly and postmenopausal adults. Osteoporosis-related fracture is a major cause of morbidity and mortality in elderly and postmenopausal adults, posing a considerable socioeconomic burden. However, existing treatments can only slow down the process of osteoporosis, reduce the risk of fractures, and repair fractures locally. Therefore, emerging methods for treating osteoporosis, such as mesenchymal stem cell transplantation, exosome-driving drug delivery systems, biomimetic materials, and 3D printing technology, have received increasing research attention, with significant progress. Mesenchymal stem cells (MSCs) are pluripotent stem cells that can differentiate into different types of functional cells. Exosomes play a key role in regulating cell microenvironments through paracrine mechanisms. Bionic materials and 3D printed scaffolds are beneficial for the reconstruction and repair of osteoporotic bones and osteoporosis-related fractures. Stem cells, exosomes, and biomimetic materials represent emerging technologies for osteoporosis treatment. This review summarizes the latest developments in these three aspects.

Pharmaceutical electrospinning and 3D printing scaffold design for bone regeneration

Bone regenerative engineering provides a great platform for bone tissue regeneration covering cells, growth factors and other dynamic forces for fabricating scaffolds. Diversified biomaterials and their fabrication methods have emerged for fabricating patient specific bioactive scaffolds with controlled microstructures for bridging complex bone defects. The goal of this review is to summarize the points of scaffold design as well as applications for bone regeneration based on both electrospinning and 3D bioprinting. It first briefly introduces biological characteristics of bone regeneration and summarizes the applications of different types of material and the considerations for bone regeneration including polymers, ceramics, metals and composites. We then discuss electrospinning nanofibrous scaffold applied for the bone regenerative engineering with various properties, components and structures. Meanwhile, diverse design in the 3D bioprinting scaffolds for osteogenesis especially in the role of drug and bioactive factors delivery are assembled. Finally, we discuss challenges and future prospects in the development of electrospinning and 3D bioprinting for osteogenesis and prominent strategies and directions in future.

Island sternocleidomastoid myocutaneous flap for posterior pharyngeal wall defect repair after anterior cervical spine surgery

Injuries and tumours of the cervical spine represent therapeutic challenges to the treating surgeon due to the complex anatomical relationships and biomechanical features. The anterior cervical midline (ACM) and anterior cervical retropharyngeal (ACR) approaches are effective and safe surgical approaches for certain cervical spine lesions, such as cervical spine neoplasms, atlantoaxial subluxation, and certain odontoid fractures. Posterior pharyngeal wall defects (PPWDs) is one of the most frequently encountered surgical morbidities after anterior cervical spine surgery (ACSS). However, limited information has been published concerning effective approaches for PPWD reconstruction after ACSS. The manuscript aimed to describe a novel application of the island sternocleidomastoid myocutaneous flap (ISMF) in the management of PPWDs after ACSS, including surgery with the ACM approach and ACR approach. From April 2015 to November 2019, the clinical data of three patients with PPWDs repaired using the ISMF in Peking university third hospital were retrospectively analysed. The observational indexes are as follows: postoperative survival of the flap, wound healing 2 weeks after surgery, eating and pronunciation function 2 months after surgery. The above indexes of these three cases recovered well. Three patients did not have any persistent PPWD after repair with the ISMF and did not require any further surgical procedures related to the cervical spine.

Practical strategy to construct anti-osteosarcoma bone substitutes by loading cisplatin into 3D-printed titanium alloy implants using a thermosensitive hydrogel

Surgical resection and perioperative adjuvant chemotherapy-based therapies have improved the prognosis of patients with osteosarcoma; however, intraoperative bone defects, local tumour recurrence, and chemotherapy-induced adverse effects still affect the quality of life of patients. Emerging 3D-printed titanium alloy (Ti₆Al₄V) implants have advantages over traditional implants in bone repair, including lower elastic modulus, lower stiffness, better bone conduction, more bone in-growth, stronger mechanical interlocking, and lager drug-loading capacity by their inherent porous structure. Here, cisplatin, a clinical first-line anti-osteosarcoma drug, was loaded into Ti₆Al₄V implants, within a PLGA-PEG-PLGA thermo-sensitive hydrogel, to construct bone substitutes with both anti-osteosarcoma and bone-repair functions. The optimal concentrations of cisplatin (0.8 and 1.6 mg/mL) were first determined in vitro. Thereafter, the anti-tumour effect and biosafety of the cisplatin/hydrogel-loaded implants, as well as their bone-repair potential were evaluated in vivo in tumour-bearing mouse, and bone defect rabbit models, respectively. The loading of cisplatin reduced tumour volume by more than two-thirds (from 641.1 to 201.4 mm³) with negligible organ damage, achieving better anti-tumour effects while avoiding the adverse effects of systemic cisplatin delivery. Although bone repair was hindered by cisplatin loading at 4 weeks, no difference was observed at 8 weeks in the context of implants with versus without cisplatin, indicating acceptable long-term stability of all implants (with 8.48%–10.04% bone in-growth and 16.94%–20.53% osseointegration). Overall, cisplatin/hydrogel-loaded 3D-printed Ti₆Al₄V implants are safe and effective for treating osteosarcoma-caused bone defects, and should be considered for clinical use.

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Vehiculated within PLGA-PEG-PLGA hydrogel, cisplatin can be conveniently loaded into 3D-printed Ti₆Al₄V implants.

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The cisplatin/hydrogel-loaded implants are safe and show a good anti-tumour potential both in vitro and in vivo.

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This strategy has better anti-osteosarcoma effects and fewer side effects than the conventional cisplatin delivery method.

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Cisplatin loading does not decrease the bone repair effect of 3D-printed Ti₆Al₄V implants 8 weeks after surgery.

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As the components of the implants are non-toxic, this strategy has great potential for clinical translation.

Different Cell and Tissue Behavior of Micro-/Nano-Tubes and Micro-/Nano-Nets Topographies on Selective Laser Melting Titanium to Enhance Osseointegration

Background and Purpose

Micro-/nano-tubes (TNTs) and micro-/nano-nets (TNNs) are the common and sensible choice in the first step of combined modifications of titanium surface for further functionalization in the purpose of extended indications and therapeutic effect. It is important to recognize the respective biologic reactions of these two substrates for guiding a biologically based first-step selection.

Materials and Methods

TNTs were produced by anodic oxidation and TNNs were formed by alkali-heat treatment. The original selective laser melting (SLM) titanium surface was set as control. Surface characterization was evaluated by scanning electron microscopy, surface roughness, and water contact angle measurements. Osteoclastogenesis and osteogenesis were measured. MC3T3-E1 cells and RAW 264.7 cells were used for in vitro assay in terms of adhesion, proliferation, and differentiation. In vivo assessments were taken on Beagle dogs with micro-CT and histological analysis.

Results

TNN and TNT groups performed decreased roughness and increased hydrophilicity compared with SLM group. For biological detections, the highest ALP activity and osteogenesis-related genes expression were observed in TNT group followed by TNN group (P <0.05). Interestingly, when it comes to the osteoclastogenesis, TNNs displayed lowest TRAP activity and osteoclastogenesis-related genes expression and TNTs were lower than SLM but higher than TNNs (P <0.05). BV/TV around implants was highest in TNT group after 4 weeks (P <0.05). HE, ALP and TRAP staining showed that osteogenic and osteoclastic activity around TNTs were both higher than TNNs (P <0.05).

Conclusion

TNNs and TNTs have dual advantages in promotion of osteogenesis and inhibition of osteoclastogenesis. Furthermore, TNNs showed better capability in inhibiting osteoclast activity while TNTs facilitated stronger osteogenesis. Our results implied that TNT substrates would take advantage in early application after implantation, while diseases with inappropriate osteoclast activity would prefer TNN substrates, which will guide a biologically based first-step selection on combined modification for different clinical purposes.

3D Printing in Development of Nanomedicines

Three-dimensional (3D) printing is gaining numerous advances in manufacturing approaches both at macro- and nanoscales. Three-dimensional printing is being explored for various biomedical applications and fabrication of nanomedicines using additive manufacturing techniques, and shows promising potential in fulfilling the need for patient-centric personalized treatment. Initial reports attributed this to availability of novel natural biomaterials and precisely engineered polymeric materials, which could be fabricated into exclusive 3D printed nanomaterials for various biomedical applications as nanomedicines. Nanomedicine is defined as the application of nanotechnology in designing nanomaterials for different medicinal applications, including diagnosis, treatment, monitoring, prevention, and control of diseases. Nanomedicine is also showing great impact in the design and development of precision medicine. In contrast to the "one-size-fits-all" criterion of the conventional medicine system, personalized or precision medicines consider the differences in various traits, including pharmacokinetics and genetics of different patients, which have shown improved results over conventional treatment. In the last few years, much literature has been published on the application of 3D printing for the fabrication of nanomedicine. This article deals with progress made in the development and design of tailor-made nanomedicine using 3D printing technology.

A novel 3D-printed locking cage for anterior atlantoaxial fixation and fusion: case report and in vitro biomechanical evaluation

BACKGROUND

Treatment of atlantoaxial dislocation is aimed at reduction and stabilization of the atlantoaxial joint. 3D printing refers to a process where additive manufacturing is achieved under precise computer control. Literature on its utilization in anterior atlantoaxial fixation and fusion is rare. This study is the first report on a 3D-printed locking cage used in the anterior procedure for atlantoaxial dislocation.

METHODS

A middle-aged male in his 40s presented with weakness and numbness of his extremities for 3 years and could only walk slowly with assistance. Imaging studies revealed severe anterior migration of C1, irreducible atlantoaxial dislocation, and severe cervical-medullary compression. A preoperative plan consisting of trans-oral soft tissue release and fixation using tailor-designed 3D-printed cages was devised. Following fluoroscopic confirmation of reduction of the atlantoaxial joints, two customized 3D-printed cages made of titanium alloy were inserted into the bilateral facet joints, which were then locked by six screws into the lateral masses of C1 and C2. The microstructure of the inserted cages was optimized for improved biomechanical stability and enhanced osseo-integration, without the need for bone grafting. In addition, a biomechanical test was performed on seven human cadaveric specimens comparing the novel implant with the conventional C1 lateral mass-C2 pedicle screw construct in three modes of motion (flexion-extension, lateral bending, axial rotation).

RESULTS

Improvement of neurologic function in the patient was evident immediately after surgery. He was able to walk independently 1 month post-operatively. At the 12-month follow-up, coronal reconstruction of CT demonstrated properly-positioned 3D-printed cages, evidence of osseo-integration at the bone-implant interface, and no subsidence or displacement of the implant. Eighteen months out of surgery, the mJOA score improved to 15, and lateral X-ray confirmed reduction of atlanto-axial dislocation. Additionally, the new construct provided strong fixation comparable to that conferred by conventional constructs as there was no significant difference observed between the two groups in all three directions of motion.

CONCLUSIONS

The novel implant represents a new option in the treatment of irreducible atlantoaxial dislocation. It can provide strong anterior support for solid fixation and fusion with a low profile and a microstructure that obviates the need for bone grafting.

Effect of 4DryField® PH on blood loss in hip bipolar hemiarthroplasty following intracapsular femoral neck fracture - a randomized clinical trial

BACKGROUND

One of the most common complications of hip arthroplasty is excessive blood loss that could necessitate allogenic blood transfusion, which is further associated with other complications, such as infections, transfusion reactions or immunomodulation. In gynecology, 4DryField®PH, an absorbable polysaccharide-based formulation, is used for hemostasis and adhesion prophylaxis. In this study, we evaluated its hemostatic effect in patients undergoing hip bipolar hemiarthroplasty following intracapsular femoral neck fracture.

METHODS

We studied 40 patients with intracapsular femoral neck fractures (Garden III or IV) admitted at our institution between July 2016 and November 2017. We included patients above 60 years with simple fracture and without pathologic fractures. Patients were randomized into intervention and control groups. The intervention group received 5 g of 4DryField® PH (subfascially and subcutaneously) during wound closure. Three drainages were inserted in a standardized manner (submuscular, subfascial, and subcutaneous) and drainage volume was measured immediately before extraction. Total blood loss was calculated using Mercuriali's formula and standard hemograms upon admission and five days after surgery. Volume of postoperative hematoma was measured using point-of-care ultrasound seven days after surgery.

RESULTS

Volume of the postoperative hematoma was reduced by 43.0 mL. However, significant reduction of total blood loss and drainage volume was not observed.

CONCLUSIONS

We observed that 4DryField® PH had a local hemostatic effect, thereby reducing volume of the postoperative hematoma. However, this reduction was small and had no effect on the total blood loss. Further studies are warranted to improve the application algorithm.

TRIAL REGISTRATION

DRKS, DRKS00017452 , Registered 11 June 2019 - Retrospectively registered.

Orientation Planning in the Fused Deposition Modeling 3D Printing of Anatomical Spine Models

Three‐dimensional (3D) printing has revolutionized medical training and patient care. Clinically it is used for patient‐specific anatomical modeling with respect to surgical procedures. 3D printing is heavily implemented for simulation to provide a useful tool for anatomical knowledge and surgical techniques. Fused deposition modeling (FDM) is a commonly utilized method of 3D printing anatomical models due to its cost-effectiveness. A potential disadvantage of FDM 3D printing complex anatomical shapes is the limitations of the modeling system in providing accurate representations of multifaceted ultrastructure, such as the facets of the lumbar spine. In order to utilize FDM 3D printing methods in an efficient manner, the pre-printing G-code assembly must be oriented according to the anatomical nature of the print. This article describes the approach that our institution's 3D printing laboratory has used to manipulate models’ printing angles in regard to the print bed and nozzle, according to anatomical properties, thus creating quality and cost-effective anatomical spine models for education and procedural simulation. 

Using personalized 3D printed Titanium sleeve-prosthetic composite for reconstruction of severe segmental bone loss of proximal femur in revision total hip arthroplasty: A case report

RATIONALE

Allograft-prosthetic composites (APCs) and proximal femoral replacement have been applied for reconstruction of severe segmental femoral bone loss in revision total hip arthroplasty. The outcomes are encouraging but the complication rate is relatively high. Considering the high complication rates and mixed results of APCs and megaprosthesis, we presented a case using personalized 3D printed Titanium sleeve-prosthetic composite for reconstruction of segmental bone defect.

PATIENT CONCERNS

A 73-year-old woman presented to the emergency department on account of acute severe pain of the left hip without history of trauma. She had undergone a cemented total hip arthroplasty for osteonecrosis of femoral head at the left side in 2000. In 2013 she underwent a cemented revision total hip arthroplasty as a result of aseptic loosening of hip prosthesis. She denied obvious discomfort prior to this episode since the revision surgery in 2013.

DIAGNOSIS

According to the clinical history, imaging and physical examination, we confirmed the diagnosis of severe segmental bone loss of proximal femur and fracture of prosthetic stem. The femoral bone defect was evaluated using the Paprosky classification system and rated as Type 3B, and the acetabular bone defect was rated as Type 2C.

INTERVENTIONS

In this study, we present the first case of severe segmental bone loss of proximal femur in revision total hip arthroplasty that was successfully treated using personalized 3D printed Titanium sleeve-prosthetic composite OUTCOMES:: At the 2-year follow-up, the patient was symptom free with a Harris Hip Score of 91. Radiographs showed excellent osteointegration between the interface of sleeve-prosthetic composite and the host bone, with no signs of implant loosening or subsidence.

LESSONS

Despite the absence of long term results of 3D printed Titanium sleeve-prosthetic composite reconstruction, the good clinical and radiological outcome at 2 years follow up implied its potential role for reconstruction of segmental femoral bone defect in revision THA.

A Feasibility Study for the Production of Three-dimensional-printed Spine Models Using Simultaneously Extruded Thermoplastic Polymers

Background Medical simulation is an emerging field for resident training. Three-dimensional printing has accelerated the development of models for spine surgical simulation. Previous models have utilized augmented infill ratios to simulate the density difference between cortical and cancellous bone; however, this does not fully account for differences in the material properties of these components of human vertebrae. In order to replicate the differences in both density and material characteristics for realistic spinal simulation, we created a three-dimensional model composed of multiple thermoplastic polymers. Materials and methods Three lumbar vertebrae and 20 C2 vertebrae models using an experimental dual material fabrication method were printed on an Ultimaker S5 3D printer. Assessment of model integrity during instrumentation as well as user tactile feedback were points of interest to determine prototype viability for educational and biomechanical use. The experimental cohort was compared with a control cohort consisting of a single material print, resin print, and polyurethane mold. Results Based on tactile feedback, the experimental dual material print (polylactic acid [PLA]/polyvinyl alcohol [PVA]) more accurately represented the sensation of in vivo instrumentation during pedicle probing, pedicle tapping, and screw placement. There were no instrumentation or material failures in the PLA/PVA experimental model cohort. Conclusions This feasibility study indicates that multiple material printing using PLA and PVA is a viable method to replicate the cortico-cancellous interface in vertebral models. This concept and design using our unique infill algorithm have not been yet reported in the medical literature. Further educational and biomechanical testing on our design is currently underway to establish this printing method as a new standard for spinal biomimetic modeling.