Thoracic Pedicle Screw Placement Guide Plate Produced by Three-Dimensional (3-D) Laser Printing

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.

Clinical Application of Personalized Digital Surgical Planning and Precise Execution for Severe and Complex Adult Spinal Deformity Correction Utilizing 3D Printing Techniques

(1) Background: The three-dimensional printing (3DP) technique has been reported to be of great utility in spine surgery. The purpose of this study is to report the clinical application of personalized preoperative digital planning and a 3DP guidance template in the treatment of severe and complex adult spinal deformity. (2) Methods: eight adult patients with severe rigid kyphoscoliosis were given personalized surgical simulation based on the preoperative radiological data. Guidance templates for screw insertion and osteotomy were designed and manufactured according to the planning protocol and used during the correction surgery. The perioperative, and radiological parameters and complications, including surgery duration, estimated blood loss, pre- and post-operative cobb angle, trunk balance, and precision of osteotomy operation with screw implantation were collected retrospectively and analyzed to evaluate the clinical efficacy and safety of this technique. (3) Results: Of the eight patients, the primary pathology of scoliosis included two adult idiopathic scoliosis (ADIS), four congenital scoliosis (CS), one ankylosing spondylitis (AS), and one tuberculosis (TB). Two patients had a previous history of spinal surgery. Three pedicle subtraction osteotomies (PSOs) and five vertebral column resection (VCR) osteotomies were successfully performed with the application of the guide templates. The main cobb angle was corrected from 99.33° to 34.17°, and the kyphosis was corrected from 110.00° to 42.00°. The ratio of osteotomy execution and simulation was 97.02%. In the cohort, the average screw accuracy was 93.04%. (4) Conclusions: The clinical application of personalized digital surgical planning and precise execution via 3D printing guidance templates in the treatment of severe adult rigid deformity is feasible, effective, and easily generalizable. The preoperative osteotomy simulation was executed with high precision, utilizing personalized designed guidance templates. This technique can be used to reduce the surgical risk and difficulty of screw placement and high-level osteotomy.

Statistical shape modelling of the thoracic spine for the development of pedicle screw insertion guides

Spinal fixation and fusion are surgical procedures undertaken to restore stability in the spine and restrict painful or degenerative motion. Malpositioning of pedicle screws during these procedures can result in major neurological and vascular damage. Patient-specific surgical guides offer clear benefits, reducing malposition rates by up to 25%. However, they suffer from long lead times and the manufacturing process is dependent on third-party specialists. The development of a standard set of surgical guides may eliminate the issues with the manufacturing process. To evaluate the feasibility of this option, a statistical shape model (SSM) was created and used to analyse the morphological variations of the T4-T6 vertebrae in a population of 90 specimens from the Visible Korean Human dataset (50 females and 40 males). The first three principal components, representing 39.7% of the variance within the population, were analysed. The model showed high variability in the transverse process (~ 4 mm) and spinous process (~ 4 mm) and relatively low variation (< 1 mm) in the vertebral lamina. For a Korean population, a standardised set of surgical guides would likely need to align with the lamina where the variance in the population is lower. It is recommended that this standard set of surgical guides should accommodate pedicle screw diameters of 3.5-6 mm and transverse pedicle screw angles of 3.5°-12.4°.

Feasibility Analysis of 3D Printing-Assisted Pedicle Screw Correction Surgery for Degenerative Scoliosis

Objective. To explore the feasibility of 3D printing-assisted pedicle screw correction surgery for degenerative scoliosis. Methods. From January 1, 2015 to January 31, 2020, patients with degenerative scoliosis who received corrective surgery in our hospital were retrospectively analyzed. Patients were grouped based on the fixation methods. Patients in the control group received traditional pedicle screw internal fixation, while those in the study group received 3D printing-assisted pedicle screw fixation. The therapeutic effects were compared. Results. There were 78 cases in the control group and 82 cases in the study group. There were no significant differences in scoliotic Cobb’s angle, pelvic incidence-lumbar lordosis (PI-LL), VAS score, JOA score, social function, physical function, role function, or cognitive function between the study group and the control group before the surgery, but there were differences in the above parameters between the two groups after surgery. The incidence of postoperative complications in the study group was also significantly lower in the study group. Conclusion. 3D printing-assisted pedicle screw correction surgery provides a strong 3D correction force with reliable effect and fewer complications, and is a good treatment choice for degenerative scoliosis.

Application of 3-dimensional printing guide template and pointed lotus-style regulator in percutaneous pedicle screw fixation for thoracolumbar fractures

This study aims to analysis the efficacy of the 3D printing percutaneous guide template in combination with the pointed lotus-style regulator in percutaneous pedicle screw fixation. 60 thoracolumbar fractures patients receiving percutaneous pedicle screw fixation (PPSF) were enrolled and randomly divided into 3 groups. Patients in Group A received traditional PPSF, while patients in Group B received PPSF with flat end lotus-style regulator and patients in Group C received PPSF with pointed lotus-style regulator. The experimental results showed that the highest number of pedicle screw successfully inserted by the first time was in group C, while lowest in group A (P < 0.05). The total time of fluoroscopy and operation were lower in group C, and higher in group A (P < 0.05). VAS and ODI scores were all lower after surgery than before surgery in 3groups. VAS and ODI scores were lower in group B and C, compared with group A at day 1, 7 after surgery (P < 0.05). KA decreased significantly in 3 groups after surgery and no difference in KA change between 3 groups (P > 0.05). Taken together, Application of the 3D printing guide template in combination with pointed lotus-style regulator improved the accuracy of pedicle insertion.

Trial registration: ClinicalTrials.gov Identifier: NCT04980131. Registered 18/07/2021.

3D printed templates improve the accuracy and safety of pedicle screw placement in the treatment of pediatric congenital scoliosis

Background

Three-dimensional (3-D) printed guidance templates are being increasingly used in spine surgery. The purpose of this study was to determine if 3D printed navigation templates can improve the accuracy of pedicle screw placement and decrease the complication rate compared to freehand screw placement in the treatment of children with congenital scoliosis.

Methods

The records of pediatric patients with congenital scoliosis treated at our hospital from January 2017 to January 2019 were retrospectively reviewed. Patients were divided into those where a 3D printed guidance templated was used and those in which the freehand method was used for pedicle screw placement. The accuracy rate of pedicle screw placement, surgical outcomes, and complications were compared between groups.

Results

A total of 67 children with congenital scoliosis were included (43 males and 24 females; mean age of 4.13 ± 2.66 years; range, 2–15 years). There were 34 children in the template-assisted group and 33 in the freehand group. The excellent accuracy rate of pedicle screw placement was significantly higher in the template-assisted group (96.10% vs. 88.64%, P = 0.007). The main Cobb angle and kyphosis angle were similar between the 2 groups preoperatively and postoperatively (all, P > 0.05), and in both groups both angles were significantly decreased after surgery as compared to the preoperative values (all, P < 0.001). The degree of change of the Cobb angle of the main curve and kyphosis angle were not significantly different between the 2 groups. There were no postoperative complications in the template group and 4 in the freehand group (0% vs. 12.12%; P = 0.009). All 4 patients with complications required revision surgery.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-021-04892-4.

Three-Dimensional Printing for Preoperative Planning and Pedicle Screw Placement in Adult Spinal Deformity: A Systematic Review

STUDY DESIGN

Systematic review.

OBJECTIVES

This current systematic review seeks to identify current applications and surgical outcomes for 3-dimensional printing (3DP) in the treatment of adult spinal deformity.

METHODS

A comprehensive search of publications was conducted through literature databases using relevant keywords. Inclusion criteria consisted of original studies, studies with patients with adult spinal deformities, and studies focusing on the feasibility and/or utility of 3DP technologies in the planning or treatment of scoliosis and other spinal deformities. Exclusion criteria included studies with patients without adult spinal deformity, animal subjects, pediatric patients, reviews, and editorials.

RESULTS

Studies evaluating the effect of 3DP drill guide templates found higher screw placement accuracy in the 3DP cohort (96.9%), compared with non-3DP cohorts (81.5%, P < .001). Operative duration was significant decreased in 3DP cases (378 patients, 258 minutes) relative to non-3DP cases (301 patients,272 minutes, P < .05). The average deformity correction rate was 72.5% in 3DP cases (245 patients). There was no significant difference in perioperative blood loss between 3DP (924.6 mL, 252 patients) and non-3DP cases (935.6 mL, 177 patients, P = .058).

CONCLUSIONS

Three-dimensional printing is currently used for presurgical planning, patient and trainee communication and education, pre- and intraoperative guides, and screw drill guides in the treatment of scoliosis and other adult spinal deformities. In adult spinal deformity, the usage of 3DP guides is associated with increased screw accuracy and favorable deformity correction outcomes; however, average costs and production lead time are highly variable between studies.

[Clinical application of three-dimensional printing technique combined with thoracic pedicle screw track detector in thoracic pedicle screw placement]

OBJECTIVE

To investigate the clinical application of three-dimensional (3D) printing technique combined with a new type of thoracic pedicle screw track detector in thoracic pedicle screw placement.

METHODS

According to the characteristics of thoracic pedicle and common clinical screw placement methods, a new type of thoracic pedicle screw track detector was independently developed and designed. The clinical data of 30 patients with thoracic vertebrae related diseases who underwent posterior thoracic pedicle screw fixation between March 2017 and January 2020 were retrospectively analysed. Among them, there were 18 males and 12 females with an average age of 56.3 years (range, 32-76 years). There was 1 case of thoracic disc herniation, 4 cases of thoracic canal stenosis, 2 cases of ossification of posterior longitudinal ligament of thoracic vertebra, 16 cases of thoracic trauma, 2 cases of thoracic infection, and 5 cases of thoracic canal occupation. Three-dimensional CT of the thoracic vertebra was routinely performed preoperatively, and the model of the patient's thoracic vertebra was reconstructed and printed out. With the assistance of the model, preoperative simulation was performed with the combination of the new type thoracic pedicle screw track detector, and detected no nails after critical cortical damage. During operation, one side was randomly selected to use traditional hand screws placement (control group), and the other side was selected to use 3D printing technique combined with new type thoracic pedicle screw track detector to assist thoracic pedicle screws placement (observation group). The single screw placement time, adjustment times of single screw, and blood loss during screw placement were compared between the two groups. The accuracy of screw placement in the two groups was evaluated according to postoperative CT imaging data.

RESULTS

The single screw placement time, adjustment times of single screw, and blood loss during screw placement in the observation group were significantly less than those in the control group ( P<0.05). Postoperative CT examination showed that the observation group had 87 screws of grade 1, 3 screws of grade 2, and the acceptable screw placement rate was 100% (90/90); the control group had 76 screws of grade 1, 2 screws of grade 2, 11 screws of grade 3, and 1 screw of grade 4, and the acceptable screw placement rate was 86.7% (78/90); showing significant difference in screw placement between the two groups ( χ 2=12.875, P=0.001). All patients were followed up 6-18 months, with an average of 11.3 months. There was no complication of vascular, nerve, spinal cord, or visceral injury, and screws or rods broken, and no patient was revised.

CONCLUSION

The 3D printing technique combined with the new type of thoracic pedicle screw track detector assisted thoracic pedicle screw placement is convenient, and significantly improves the accuracy and safety of intraoperative screw placement, and overall success rate of the surgery.

Are 3D Printing Templates an Advantage in Upper Thoracic Pedicle Screw Fixation?

Background This study aims to compare the clinical results of patients with upper thoracic vertebral fractures treated with pedicle screw and posterior spinal fusion with preoperative surgical planning and 3-dimensional (3D) modeling and patients treated with freehand screws. Methods Fifty patients who underwent pedicle screw placement with a diagnosis of upper thoracic fracture between June 2018 and October 2020 were included in our study. Pedicle screws were used in 25 patients (group 1) after the planning was completed with the help of 3D preoperative printing and modeling. Pedicle screws were applied in 25 patients in the control group (group 2) using the freehand technique. Intraoperative bleeding amount, operation time, and correct screw placement data in both groups were recorded. Results The operation time was 134 ± 22 minutes for group 1 and 152 ± 38 minutes for group 2. The difference in operation times was found to be statistically significant (p < 0.05). Based on axial and sagittal reconstruction images, the accuracy rate of pedicle screw placement (grades 0 and 1) in group I was 96.6% compared to 83.6% in group II. The minor perforation rate (grade 1, <2 mm) was 5.8% in group I compared to 11.8% in group II. The moderate perforation rate (grade 2, 2-4 mm) was 3.4% in group I compared to 14% in group II. The severe perforation rate (grade 3, >4 mm) was 2.3% in group II; however, misplaced screws were not associated with neurological deficits. The difference in overall accuracy rates between the two groups was significant (p < 0.05). Conclusions For 3D models of upper thoracic pedicle screw insertion, guide plates can be produced inexpensively and individually. It provides a new method for the accurate placement of upper thoracic pedicle screws with high accuracy and secure use in screw insertion.

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.

Investigation of the Effects of Three-Dimensional Modeling Techniques on Degenerative Rotoscoliosis Surgery

Objectives The present study aimed to compare patients in whom an operation plan was prepared before surgery using the three-dimensional (3D) modeling technology with the application of freehand screws using magnetic resonance imaging (MRI) and computed tomography (CT) scan images. Methods The printings and modelings were established in the Training and Research Center. Of 40 patients, 20 underwent surgery with 3D printing (Group 1) and 20 with the freehand technique (Group 2). The surgeries were performed by the same surgeons. Moreover, 5-mm pedicle screws were located in 122 vertebrae in 20 patients in whom 3D modeling was used and in 124 vertebrae in 20 patients in whom this modeling technique was not used. Results The mean time of screw insertion was 2.9 ± 1.2 minutes in the experimental group and 4.7 ± 2.3 minutes in the control group. While the mean amount of bleeding was 7.4 ± 4.1 ml in the experimental group, it was found to be 39.6 ± 14.2 ml in the control group. When the locations of the screws in the experimental group were evaluated, it was seen that 106 (86.9%) screws were 'excellent' and 16 (13.1%) screws were 'good.' When the placement of 124 pedicle screws in the control group was evaluated, it was found that 100 (80.6%) screws were 'excellent,' 20 (17.8%) screws were 'good,' and two (1.6%) screws were 'poor.' Conclusion The use of the improved 3D technology in the neurosurgery field is advantageous for surgeons, as it decreases the preoperative preparation phase, length of operation, and risk of complications.

Biomechanical Evaluation and the Assisted 3D Printed Model in the Patient-Specific Preoperative Planning for Thoracic Spinal Tuberculosis: A Finite Element Analysis

Posterior fixation is superior to anterior fixation in the correction of kyphosis and maintenance of spinal stability for the treatment of thoracic spinal tuberculosis. However, the process of selecting the appropriate spinal fixation method remains controversial, and preoperative biomechanical evaluation has not yet been investigated. In this study, we aimed to analyze the application of the assisted finite element analysis (FEA) and the three-dimensional (3D) printed model for the patient-specific preoperative planning of thoracic spinal tuberculosis. An adult patient with thoracic spinal tuberculosis was included. A finite element model of the T7−T11 thoracic spine segments was reconstructed to analyze the biomechanical effect of four different operative constructs. The von Mises stress values of the implants in the vertical axial load and flexion and extension conditions under a 400-N vertical axial pre-load and a 10-N⋅m moment were calculated and compared. A 3D printed model was used to describe and elucidate the patient’s condition and simulate the optimal surgical design. According to the biomechanical evaluation, the patient-specific preoperative surgical design was prepared for implementation. The anterior column, which was reconstructed with titanium alloy mesh and a bone graft with posterior fixation using seven pedicle screws (M+P) and performed at the T7–T11 level, decreased the von Mises stress placed on the right rod, T7 pedicle screw, and T11 pedicle. Moreover, the M+P evaded the left T9 screw without load bearing. The 3D printed model and preoperative surgical simulation enhanced the understanding of the patient’s condition and facilitated patient-specific preoperative planning. Good clinical results, including no complication of implants, negligible loss of the Cobb angle, and good bone fusion, were achieved using the M+P surgical design. In conclusion, M+P was recommended as the optimal method for preoperative planning since it enabled the preservation of the normal vertebra and prevented unnecessary internal fixation. Our study indicated that FEA and the assisted 3D printed model are tools that could be extremely useful and effective in the patient-specific preoperative planning for thoracic spinal tuberculosis, which can facilitate preoperative surgical simulation and biomechanical evaluation, as well as improve the understanding of the patient’s condition.

Three-dimensional printing in spine surgery: a review of current applications

In recent years, the use of three-dimensional printing (3DP) technology has gained traction in orthopedic spine surgery. Although research on this topic is still primarily limited to case reports and small cohort studies, it is evident that there are many avenues for 3DP innovation in the field. This review article aims to discuss the current and emerging 3DP applications in spine surgery, as well as the challenges of 3DP production and limitations in its use. 3DP models have been presented as helpful tools for patient education, medical training, and presurgical planning. Intraoperatively, 3DP devices may serve as patient-specific surgical guides and implants that improve surgical outcomes. However, the time, cost, and learning curve associated with constructing a 3DP model are major barriers to widespread use in spine surgery. Considering the costs and benefits of 3DP along with the varying risks associated with different spine procedures, 3DP technology is likely most valuable for complex or atypical spine disorder cases. Further research is warranted to gain a better understanding of how 3DP can and will impact spine surgery.

Does Three-Dimensional Printed Patient-Specific Templates Add Benefit in Revision Surgeries for Complex Pediatric Kyphoscoliosis Deformity with Sublaminar Wires in Situ? A Clinical Study

STUDY DESIGN

Case-control study.

PURPOSE

To evaluate the accuracy of three-dimensional (3D) printed patient-specific templates (PSTs) for placement of pedicle screws (PAs) in patients undergoing revision surgeries for complex kyphoscoliosis deformity with sublaminar wires in situ.

OVERVIEW OF LITERATURE

Revision kyphoscoliosis correction surgery in pediatric patients is a challenging task for the treating surgeon. In patients with sublaminar wires in situ, the native anatomical landmarks are obscured, thus making the freehand screw placement technique a highly specialized task. Hence, the concept of using PSTs for insertion of PAs in such surgeries is always intriguing and attractive.

METHODS

Five consecutive patients undergoing revision deformity correction with sublaminar wires in situ were included in this study. Patients were divided in two groups based on the technique of PA insertion. A total of 91 PAs were inserted using either a freehand technique (group A) or 3D printed templates (group B) (34 vs. 57). The placement of PAs was classified according to a postoperative computed tomography scan using Neo's classification. Perforation beyond class 2 (>2 mm) was termed as a misplaced screw. The average time required for the insertion of screws was also noted.

RESULTS

Mean age, surgical time, and blood loss were recorded. The change in mean Cobb's angle in both groups was also recorded. The difference in rates of misplaced screws was noted in group A and group B (36.21% vs. 2.56%); however, the mean number of misplaced PAs per patient in group A and group B was statistically insignificant (6.5±3.54 vs. 4.67±1.53, p =0.4641). The mean time required to insert a single PA was also statistically insignificant (120±28.28 vs. 90±30 seconds, p =0.3456).

CONCLUSIONS

Although 3D printed PSTs help to avoid the misplacement of PAs in revision deformity correction surgeries with sublaminar wires in situ, the mean number of misplaced screws per patient using this technique was found to be statistically insignificant when compared with the freehand technique in this study.

Comparing the Treatment of Congenital Spine Deformity Using Freehand Techniques In Vivo and 3D-Printed Templates In Vitro (Prospective-Retrospective Single-Center Analytical Single-Cohort Study)

INTRODUCTION

Hemivertebrae excision with local posterior instrumentation is the most common technique for treatment of patients with congenital spine deformity-it is performed at a very young age. We conducted a comparative analysis for accuracy of pedicle screw positioning in infants with congenital scoliosis of the thoracolumbar area inserted using freehand technique in vivo and 3D-printed guiding templates in vitro.

METHODS

The study analyzes the results of 10 surgically treated patients with congenital deformity of the thoracolumbar spine due to vertebrae failure of formation. These patients were included in group 1 (in vivo) comprising six boys and four girls with a mean age of 3 years 8 months (2 years 2 months-6 years 8 month). Group 2 (in vitro) consisted of 27 plastic 3D-printed models of congenitally deformed spine of the same 10 patients in which screws were placed using 3D-printed guiding templates. The accuracy of screw position was assessed using computer tomography data performed postoperatively with Gertzbein-Robbins classification.

RESULTS

Results of our study show that screw insertion using 3D-printed guiding templates during surgical treatment of infants with congenital spine deformities is more accurate than using freehand technique (96.3% vs. 78.8% p = 0.011).

CONCLUSION

The data show that this method of screw insertion is very promising and can be used in surgical treatment of infants with congenital spine deformities.

The Accuracy of 3D Printing Assistance in the Spinal Deformity Surgery

Background

The pedicle screw is one of the main tools used in spinal deformity correction surgery. Robotic and navigated surgeries are usually used, and they provide superior accuracy in pedicle screw placement than free-hand and fluoroscopy-guided techniques. However, their high cost and space limitation are problematic. We provide a new solution using 3D printing technology to facilitate spinal deformity surgery.

Methods

A workflow was developed to assist spinal deformity surgery using 3D printing technology. The trajectory and profile of pedicle screws were determined on the image system by the surgical team. The engineering team designed drill templates based on the bony surface anatomy and the trajectory of pedicle screws. Their effectiveness and safety were evaluated during a preoperative simulation surgery. The surgery consisted in making a pilot hole through the drill template on a computed tomography- (CT-) based, full-scale 3D spine model for every planned segment. Somatosensory evoke potential (SSEP) and motor evoke potential (MEP) were used for intraoperative neurophysiological monitoring. Postoperative CT was obtained 6 months after the correction surgery to confirm the screw accuracy.

Results

From July 2015 to November 2016, we performed 10 spinal deformity surgeries with 3D printing technology assistance. In total, 173 pedicle screws were implanted using drill templates. No notable change in SSEP and MEP or neurologic deficit was noted. Based on postoperative CT scans, the acceptable rate was 97.1% (168/173). We recorded twelve pedicle screws with medial breach, six with lateral breach, and five with inferior breach. Medial breach (12/23) was the main type of penetration. Lateral breach occurred mostly in the concave side (5/6). Most penetrations occurred above the T8 level (69.6%, 16/23).

Conclusion

3D printing technology provides an effective alternative for spinal deformity surgery when expensive medical equipment, such as intraoperative navigation and robotic systems, is unavailable.

Accurate Osteotomy for the Treatment of a Rare Case of Postaxial Polydactyly of the Foot That Originated From a Deformed Calcaneus Using a 3D-Printed Guiding Plate

Polydactyly is a common congenital deformity of the foot that can be categorized as preaxial, central, or postaxial. Current treatments involve resecting the supernumerary toe(s) and repairing the normal toe(s) and soft tissue. Here, we present the first published report describing a very rare case of polydactyly of the foot, in which the supernumerary toe originated from a deformed calcaneus, which formed an abnormal bony bump. Preoperatively, 3-dimensional (3D) computed tomography reconstruction images revealed the morphology of the deformed toe and calcaneus, and gait analysis showed an abnormal weightbearing zone in the left foot. The 3D printing technology and a specially designed 3D-printed guiding plate were used for osteotomy. Postoperatively, x-ray showed that the calcaneus had a normal shape and surface, whereas gait analysis showed that the left foot was uniformly loaded and the area of pain was eliminated. Our findings should raise awareness among clinicians that a 3D-printed guiding plate is useful in the treatment of such an unusual deformity.

A Review of Current Clinical Applications of Three-Dimensional Printing in Spine Surgery

Three-dimensional (3D) printing is a transformative technology with a potentially wide range of applications in the field of orthopaedic spine surgery. This article aims to review the current applications, limitations, and future developments of 3D printing technology in orthopaedic spine surgery. Current preoperative applications of 3D printing include construction of complex 3D anatomic models for improved visual understanding, preoperative surgical planning, and surgical simulations for resident education. Intraoperatively, 3D printers have been successfully used in surgical guidance systems and in the creation of patient specific implantable devices. Furthermore, 3D printing is revolutionizing the field of regenerative medicine and tissue engineering, allowing construction of biocompatible scaffolds suitable for cell growth and vasculature. Advances in printing technology and evidence of positive clinical outcomes are needed before there is an expansion of 3D printing applied to the clinical setting.

Clinical Outcome of Total Knee Arthroplasty Performed Using Patient-Specific Cutting Guides

Background

Patient-specific instruments have recently gained attention for ensuring the accuracy of osteotomy and correct alignment in total knee arthroplasty (TKA). We aimed to report our experience with TKA performed by using CT-based 3D model of cutting guides in our clinic.

Material/Methods

A total of 36 patients (mean age, 67.58±8.46 years; 24 females, 12 males) who underwent TKA with 3D patient-specific cutting guides in our clinic were included in the study. Differences between preoperatively planned bone resections and actual bone resections were calculated. Femoral and tibial component angles were measured on radiographs of the knee. The change in knee pain was evaluated by patients on a 10-point visual analog scale (VAS). Patients were followed up for 6 months postoperatively.

Results

The actual bone resection was 0.5–1.5 mm higher than the planned resection for all sides, being statistically significant for posterior lateral and distal medial sides (1.1±1.3 mm and 1.5±0.9 mm, respectively; p<0.05). On postoperative radiographs, coronal tibial component angle was 88.8°±0.9° and coronal femoral component angle was 95.2°±1.6°, showing good postoperative alignment. The VAS pain score of patients significantly decreased from preoperative 3.9±0.8 to 1.1±0.9 at 6 months after the operation. One patient developed superficial tissue infection on postoperative follow-up, which was effectively treated. No other pathology was detected in the postoperative period.

Conclusions

Patient-specific cutting guides can provide intraoperative guidance for better placement of the implant in TKA and increase the accuracy of osteotomy and postoperative alignment.

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.

Stable passively harmonic mode-locking dissipative pulses in 2µm solid-state laser

We report on stable passively harmonic mode-locking dissipative pulses with high repetition rate and narrow bandwidth in 2µm Tm: CaYAlO₄ laser. At the large intracavity intensity, the laser generated 1st-order to 5th-order passively harmonic solitons with fundamental repetition rate of ~198 MHz and 5th-order repetition rate up to 0.98 GHz, which was mainly caused by the peak power clamp effect. The solitons yielded a tunable central wavelength from 1940nm to 1950 nm, and a narrow optical spectrum bandwidth of 60 pm without any active optical filter. At low intracavity intensity, the laser operated on the typical SESAM-guided mode-locking mode, with the scaled output average power up to 1.15 W. To our knowledge, this is the first observation of passively harmonic mode locking in 2µm solid laser system, and the first Watt-level output average power in Tm: CYA mode locking laser.

Three-dimensional printing in the surgical treatment of osteoid osteoma of the calcaneus: A case report

Surgical excision is the traditional treatment for osteoid osteoma. However, the complexity of the foot anatomy makes a satisfactory outcome challenging. Difficulty in localizing the lesion intraoperatively may result in either incomplete tumor resection or excessive bone loss. To date, no published report has described the use of three-dimensional printing in the surgical treatment of osteoid osteoma of the calcaneus. In this case, we printed a three-dimensional model of the calcaneus of a 17-year-old female patient with a 2-year history of night pain in the lateral aspect of the hindfoot and ankle, evaluated the lesion as an osteoid osteoma, and designed a surgical guiding plate. Intraoperatively, we had no difficulty achieving complete resection of the lesion from the lateral calcaneus bone window, autogenous bone grafting, and subtalar arthrodesis. At the 2-year follow-up examination, the patient remained asymptomatic with no recurrence of the osteoid osteoma.