Positioning error of custom 3D-printed surgical guides for the radius: influence of fitting location and guide design

The clinical value of preoperative 3D planning and 3D surgical guides for Imhäuser osteotomy in slipped capital femoral epipysis: a retrospective study

BACKGROUND

Accurate repositioning of the femoral head in patients with Slipped Capital Femoral Epiphysis (SCFE) undergoing Imhäuser osteotomy is very challenging. The objective of this study is to determine if preoperative 3D planning and a 3D-printed surgical guide improve the accuracy of the placement of the femoral head.

METHODS

This retrospective study compared outcome parameters of patients who underwent a classic Imhäuser osteotomy from 2009 to 2013 with those who underwent an Imhäuser osteotomy using 3D preoperative planning and 3D-printed surgical guides from 2014 to 2021. The primary endpoint was improvement in Range of Motion (ROM) of the hip. Secondary outcomes were radiographic improvement (Southwick angle), patient-reported clinical outcomes regarding hip and psychosocial complaints assessed with two questionnaires and duration of surgery.

RESULTS

In the 14 patients of the 3D group radiographic improvement was slightly greater and duration of surgery was slightly shorter than in the 7 patients of the classis Imhäuser group. No difference was found in the ROM, and patient reported clinical outcomes were slightly less favourable.

CONCLUSIONS

Surprisingly we didn't find a significant difference between the two groups. Further research on the use of 3D planning an 3D-printed surgical guides is needed.

TRIAL REGISTRATION

Approval for this study was obtained of the local ethics committees of both hospitals.

Three-Dimensionally Planned and Printed Patient-Tailored Plates for Corrective Osteotomies of the Distal Radius and Forearm

PURPOSE

We evaluated the 1-year postoperative clinical and patient-reported outcomes in patients who had a 3-dimensional planned corrective osteotomy of their distal radius, radial shaft, or ulnar shaft using a printed, anatomical, patient-tailored plate to determine the feasibility and effectiveness of this methodology.

METHODS

Simulations in computer-assisted preoperative planning of corrective osteotomies resulted in 3-dimensionally printed surgical guides, surgical models, and anatomically customized plates for application at the distal radius and forearm. Patients with malunions of the distal radius or forearm who underwent fixation with the custom-made plates were documented in our registry. Grip strength and range of motion assessments were made before surgery (baseline), as well as at 6 weeks and 3 and 12 months. Additionally, patients rated their wrist-related pain and disability using the Patient-Rated Wrist Evaluation.

RESULTS

Fifteen patients underwent corrective surgery, and the 1-year follow-up data of 14 patients with a median age of 56 years (interquartile range, 24-64 years) were available for analysis. The median baseline Patient-Rated Wrist Evaluation score improved from 47 to 7 after 1 year. The flexion-extension arc of motion of the wrist increased from 90° at baseline to 130° at 1 year and the pronation-supination arc of motion of the wrist increased from 135° to 160° in the same time period. Differences in radiological measurements for palmar and radial inclinations, as well as for ulnar variance between the affected and contralateral wrists, were reduced with the osteotomy. In 1 case, the plate was removed 11 months after the osteotomy. No severe adverse events were reported.

CONCLUSIONS

Three-dimensionally planned and printed patient-tailored plates offer a reliable method for correcting even complex malunions of the distal radius and forearm.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Using a patient-specific cutting guide enables identical knee osteotomies: An evaluation of accuracy on sawbones

PURPOSE

It was hypothesized that using a Patient-Specific Cutting Guide (PSCG) would allow the creation of sawbones model osteotomies, identical in the 3 planes and the hinge parameters, that can be used for biomechanical studies. The aim of the study was to evaluate the accuracy of the PSCG system and to introduce and assess the new hinge parameter; the hinge area.

METHODS

Six identical sawbones tibia models were identically set up for identical osteotomy cuts by the same surgeon in the same session and with identical instruments. A medical scanner was used to evaluate the 3D configuration of all the specimens. The analyzed parameters included the cutting angles in both the coronal and sagittal planes (degrees) and the hinge and the slicing areas (cm2), and the hinge thickness (mm). The values were statistically evaluated for average, standard deviation, 95% confidence index, and delta to the expected values were calculated.

RESULTS

The mean values for the coronal and sagittal angles were 110.5̊±1̊ and 89.8̊±0.8̊, respectively. The 95% confidence index level ranged between 0.1̊, and 0.8̊ in both the coronal & the sagittal planes. The mean values for the hinge thickness, the hinge area, and the slicing area were 12.7±1.5mm, 4.2±0.9 cm2, and 18.3±1.2 cm2, respectively.

CONCLUSION

In the presented study, it can be demonstrated that mechanically identical osteotomy specimens, with regard to the cutting planes and hinge parameters, can be reliably created using the PSCG. The identical specimens can be used for biomechanical research purposes to further expand our knowledge of the factors affecting osteotomy outcomes.

LEVEL OF EVIDENCE

IV.

Use of Preoperative 3D Virtual Planning and 3D-Printed Patient-Specific Guides to Facilitate a Single-Stage Cranial Closing Wedge Ostectomy and Tibial Plateau Leveling Osteotomy Procedure to Address Proximal Tibial Deformity, an Excessive Tibial Plateau Angle, and Cranial Cruciate Ligament Insufficiency in a Dog

A 9-month-old mixed-breed dog was presented for bilateral proximal tibial deformity resulting in an excessive tibial plateau angle and cranial cruciate ligament insufficiency. Initial surgical management of the right pelvic limb was done by performing a cranial closing wedge ostectomy. Inadequate leveling of the plateau resulted in a postliminal meniscal tear which was addressed during a revision tibial plateau leveling osteotomy. The left pelvic limb was managed in a single-session surgery using three-dimensional (3D) virtual surgical planning and custom 3D-printed surgical guides to perform a combined cranial closing wedge ostectomy and tibial plateau leveling osteotomy. Postoperative 3D analysis of the left tibia revealed the accuracy of the surgical result within 2° of the virtual surgical plan. The dog developed a transient grade II/IV left medial patellar luxation following surgery but ultimately attained a full functional recovery and was actively engaged in competitive agility work 46 months following surgery on the left pelvic limb.

Novel Positioning Feedback System as a Guidance in Bone Tumor Resection

Need: Bone resection using customized 3D-printed guides can improve accuracy, but the technique is still associated with clinically significant errors.Technical solution: We developed an inexpensive optical feedback system (OFS) that compares intraoperative 2D camera images to the pre-operative plan, and accurately depicts the surgeon's guide placement prior to cutting, reducing the errors in resection.Proof of concept: We simulated wide resections of a bone sarcoma on 24 cadaver femurs using 3 cutting guide types. Guide placement was measured using the OFS and compared to CT-scans showing the actual guide position. We carried out a second, controlled study on 20 sawbones, comparing the accuracy of the final bone cuts with and without the surgeon actively using the OFS to adjust the guide position before cutting.Results: For cadavers, in 2 of 3 planes, the position of the jig recorded by the OFS closely matched its actual position, with an accuracy of .87° ± .65°(r = .94) and 1.2° ± 1.3°(r = .81) in the transverse and sagittal planes, respectively. In the second study, OFS increased accuracy of the final cut about the transverse and sagittal planes, respectively by 53.1% (P = .011)/54.7% (P = .04) and 33% (P = .051)/38% (P = .042) in terms of rotation and translation.Next steps: Developing the OFS as a mobile application to reduce the processing time and improve accessibility in the operating room.Conclusion: The OFS could accurately depict the guide placement on the bone and significantly improve the surgical accuracy of 3D printed jigs.

An Overview of 3D Anatomical Model Printing in Orthopedic Trauma Surgery

Introduction

3D object printing technology is a resource increasingly used in medicine in recent years, mainly incorporated in surgical areas like orthopedics. The models made by 3D printing technology provide surgeons with an accurate analysis of complex anatomical structures, allowing the planning, training, and surgery simulation. In orthopedic surgery, this technique is especially applied in oncological surgeries, bone, and joint reconstructions, and orthopedic trauma surgeries. In these cases, it is possible to prototype anatomical models for surgical planning, simulating, and training, besides printing of instruments and implants.

Purpose

The purpose of this paper is to describe the acquisition and processing from computed tomography images for 3D printing, to describe modeling and the 3D printing process of the biomodels in real size. This paper highlights 3D printing with the applicability of the 3D biomodels in orthopedic surgeries and shows some examples of surgical planning in orthopedic trauma surgery.

Patients and Methods

Four examples were selected to demonstrate the workflow and rationale throughout the process of planning and printing 3D models to be used in a variety of situations in orthopedic trauma surgeries. In all cases, the use of 3D modeling has impacted and improved the final treatment strategy.

Conclusion

The use of the virtual anatomical model and the 3D printed anatomical model with the additive manufacturing technology proved to be effective and useful in planning and performing the surgical treatment of complex articular fractures, allowing surgical planning both virtual and with the 3D printed anatomical model, besides being useful during the surgical time as a navigation instrument.

Assessment of foot deformities in individuals with cerebral palsy using weight-bearing CT

OBJECTIVE

The aims of this study were to visualize and quantify relative bone positions in the feet of individuals with cerebral palsy (CP) with a foot deformity and compare bone positions with those of typically developed (TD) controls.

MATERIALS AND METHODS

Weight-bearing CT images of 14 individuals with CP scheduled for tendon transfer and/or bony surgery and of 20 TD controls were acquired on a Planmed Verity WBCT scanner. Centroids of the navicular and calcaneus with respect to the talus were used to quantify foot deformities. All taluses were aligned and the size and dimensions of the individuals' talus were scaled to correct for differences in bone sizes. In order to visualize and quantify variations in relative bone positions, 95% CI ellipsoids and standard deviations in its principle X-, Y-, and Z-directions were determined.

RESULTS

In individuals with CP (age 11-17), a large variation in centroid positions was observed compared to data of TD controls. Radiuses of the ellipsoids, representing the standard deviations of the 95% CI in the principle X-, Y-, and Z-directions, were larger in individuals with CP compared to TD controls for both the calcaneus (3.16 vs 1.86 mm, 4.26 vs 2.60 mm, 9.19 vs 3.60 mm) and navicular (4.63 vs 1.55 mm, 5.18 vs 2.10 mm, 16.07 vs 4.16 mm).

CONCLUSION

By determining centroids of the calcaneus and navicular with respect to the talus on WBCT images, normal and abnormal relative bone positions can be visualized and quantified in individuals with CP with various foot deformities.

Application of 3D modeling in a personalized approach to bone osteosynthesis (A literature review)

Three-dimensional printing opens up many opportunities for use in traumatology and orthopedics, because it takes into account personal characteristics of the patients. Modern methods of high-resolution medical imaging can process data to create threedimensional images for printing physical objects. Today, three-dimensional printers are able to create a model of any complexity of shape and geometry. The article provides a review of the literature about three-dimensional digital modeling in shaping implants for osteosynthesis. Data search was carried out on the Scopus, Web of Scince, Pubmed, RSCI databases for the period 2012–2022. The effectiveness of three-dimensional printing for preoperative modeling of bone plates has been confirmed: implants perfectly corresponds with the unique anatomy of the patient, since the template for it is based on the materials of computed tomography. Individual templates can be useful when the geometry of patients' bones goes beyond the standard, and when improved results of surgery are expected due to better matching of implants to the anatomical needs of patients. 

Cochlear implant positioning and fixation using 3D-printed patient specific surgical guides; a cadaveric study

Hypothesis

To develop and validate the optimal design and evaluate accuracy of individualized 3D- printed surgical guides for cochlear implantation.

Background

Positioning and fixation of the cochlear implant (CI) are commonly performed free hand. Applications of 3-dimensional (3D) technology now allow us to make patient specific, bone supported surgical guides, to aid CI surgeons with precise placement and drilling out the bony well which accommodates the receiver/stimulator device of the CI.

Methods

Cone beam CT (CBCT) scans were acquired from temporal bones in 9 cadaveric heads (18 ears), followed by virtual planning of the CI position. Surgical, bone-supported drilling guides were designed to conduct a minimally invasive procedure and were 3D-printed. Fixation screws were used to keep the guide in place in predetermined bone areas. Specimens were implanted with 3 different CI models. After implantation, CBCT scans of the implanted specimens were performed. Accuracy of CI placement was assessed by comparing the 3D models of the planned and implanted CI’s by calculating the translational and rotational deviations.

Results

Median translational deviations of placement in the X- and Y-axis were within the predetermined clinically relevant deviation range (< 3 mm per axis); median translational deviation in the Z-axis was 3.41 mm. Median rotational deviations of placement for X-, Y- and Z-rotation were 5.50°, 4.58° and 3.71°, respectively.

Conclusion

This study resulted in the first 3D-printed, patient- and CI- model specific surgical guide for positioning during cochlear implantation. The next step for the development and evaluation of this surgical guide will be to evaluate the method in clinical practice.

Additive Manufacturing in Orthopedics: A Review

Additive manufacturing is an advanced manufacturing manner that seems like the industrial revolution. It has the inborn benefit of producing complex formations, which are distinct from traditional machining technology. Its manufacturing strategy is flexible, including a wide range of materials, and its manufacturing cycle is short. Additive manufacturing techniques are progressively used in bone research and orthopedic operation as more innovative materials are developed. This Review lists the recent research results, analyzes the strengths and weaknesses of diverse three-dimensional printing strategies in orthopedics, and sums up the use of varying 3D printing strategies in surgical guides, surgical implants, surgical predictive models, and bone tissue engineering. Moreover, various postprocessing methods for additive manufacturing for orthopedics are described.

3D surgical planning of pediatric tumors: a review

BACKGROUND

3D surgical planning for the treatment of tumors in pediatrics using different neuroimaging methods is witnessing an accelerating and dynamic development. Until now, there have been many reports on the use of 3D printing techniques in different aspects of medical practice. Pediatric tumors mainly in the abdomen are among the most medical specialties that benefit from using this technique. The purpose of the current study is to review published literature regarding 3D surgical planning and its applications in the treatment of pediatric tumors and present challenges facing these techniques.

MATERIALS AND METHODS

A completed review of the available literature was performed, effect sizes from published studies were investigated, and results are presented concerning the use of 3D surgical planning in the management of pediatric tumors, most of which are abdominal.

RESULTS

According to the reviewed literature, our study comes to the point that 3D printing is a valuable technique for planning surgery for pediatric tumors in heart, brain, abdomen and bone. MRI and CT are the most common used techniques for preparing 3D printing models, as indicated by the reviewed reports. The reported studies have indicated that 3D printing allows the understanding of the anatomy of complex tumor cases, the simulation using surgical instruments, and medical and family education. The materials, 3D printing techniques and costs to be used depend on the application.

CONCLUSION

This technology can be applied in clinical practice with a wide spectrum, using various tools and a range of available 3D printing methods. Incorporating 3D printing into an effective application can be a gratifying process with the use of a multidisciplinary team and rapid advances, so more experience would be needed with this technique to show a clinical gain.

Development of a Novel X-ray Compatible 3D-Printed Bone Model to Characterize Different K-Wire Fixation Methods in Support of the Treatment of Pediatric Radius Fractures

Additive manufacturing technologies are essential in biomedical modeling and prototyping. Polymer-based bone models are widely used in simulating surgical interventions and procedures. Distal forearm fractures are the most common pediatric fractures, in which the Kirschner wire fixation is the most widely used operative method. However, there is still lingering controversy throughout the published literature regarding the number of wires and sites of insertion. This study aims to critically compare the biomechanical stability of different K-wire fixation techniques. Different osteosyntheses were reconstructed on 189 novel standardized bone models, which were created using 3D printing and molding techniques, using PLA and polyurethane materials, and it has been characterized in terms of mechanical behavior and structure. X-ray imaging has also been performed. The validation of the model was successful: the relative standard deviations (RSD = 100 × SD × mean-1, where RSD is relative standard deviation, SD is the standard deviation) of the mechanical parameters varied between 1.1% (10° torsion; 6.52 Nm ± 0.07 Nm) and 5.3% (5° torsion; 4.33 Nm ± 0.23 Nm). The simulated fractures were fixed using two K-wires inserted from radial and dorsal directions (crossed wire fixation) or both from the radial direction, in parallel (parallel wire fixation). Single-wire fixations with shifted exit points were also included. Additionally, three-point bending tests with dorsal and radial load and torsion tests were performed. We measured the maximum force required for a 5 mm displacement of the probe under dorsal and radial loads (means for crossed wire fixation: 249.5 N and 355.9 N; parallel wire fixation: 246.4 N and 308.3 N; single wire fixation: 115.9 N and 166.5 N). We also measured the torque required for 5° and 10° torsion (which varied between 0.15 Nm for 5° and 0.36 Nm for 10° torsion). The crossed wire fixation provided the most stability during the three-point bending tests. Against torsion, both the crossed and parallel wire fixation were superior to the single-wire fixations. The 3D printed model is found to be a reliable, cost-effective tool that can be used to characterize the different fixation methods, and it can be used in further pre-clinical investigations.

Accuracy of commercial 3D printers for the fabrication of surgical guides in dental implantology

OBJECTIVES

To evaluate the accuracy of two different surgical guides (small extent = single implant and large extent = full arch) fabricated by five additive manufacturing technologies (SLA=Stereolithography, DLP= Digital Light Processing, FDM=Fused Deposition Modeling, SLS=Selective Laser Sintering, Inkjet).

METHODS

Overall, 72 guides (6 per type) were obtained with the different machines (SLA=Form2; DLP=Rapid Shape D40 and Cara Print 4.0; FDM=Raise 3D Pro2; SLS=Prodways P1000; Polyjet®=Stratasys J750). The guides were surface-scanned with an optical dental scanner, and the resulting files were compared with the initial design files using a surface matching software. Root Mean Square (RMS) and standard deviation were calculated, representing respectively trueness and precision. Kruskall-Wallis non-parametric test was used to compare trueness and precision between small-extent and large-extent guides and 3D printer by pairs. The threshold for significance was α=0.05, except for the comparison of printers by pairs where a Bonferroni-corrected level of 0.0033 was used.

RESULTS

Significant differences were observed for trueness and precision between small-extent and large-extent guides, regardless the printer except for DLP (trueness and precision) and SLS (precision). SLA, DLP and Polyjet® technologies showed similar results in terms of trueness and precision for both small-extend and large-extend guides (P>0.05).

CONCLUSIONS

The size affected the accuracy of CAD-CAM surgical guides. The different additive manufacturing technologies had a limited impact on the accuracy.

CLINICAL SIGNIFICANCE

This study is of clinical interest as it shows that the 3D printing technology (SLA/DLP) has a limited impact on 3D printed surgical guides accuracy. However, the size of the guide can have a significant impact, as small-extent guides were more accurate than large-extent guides.

An image fusion system for corrective osteotomy of distal radius malunion

Background

To provide surgical support for corrective osteotomy, we developed an image fusion system for three-dimensional (3D) preoperative planning and fluoroscopy. To assess the utility of this image fusion system, we evaluated the reproducibility of preoperative planning for corrective osteotomy of dorsally angulated distal radius malunion using the system and compared reproducibility without using the system.

Methods

Ten wrists from 10 distal radius malunion patients who underwent corrective osteotomy were evaluated. 3D preoperative planning and the image fusion system were used for the image fusion group (n = 5). Only 3D preoperative planning was used for the control group (n = 5). 3D preoperative planning was performed for both groups in order to assess reduction, placement, and the choice of implants. In the image fusion group, the outline of the planned image was displayed on a monitor and overlapped with fluoroscopy images during surgery. Reproducibility was evaluated using preoperative plan and postoperative 3D images. Images were compared with the 3D coordinates of the radial styloid process (1), the volar and dorsal edges of the sigmoid notch (2) (3), and the barycentric coordinates of the three reference points. The reproducibility of the preoperative plan was evaluated by the distance of the coordinates between the plan and postoperative images for the reference points.

Results

The distances between preoperative planning and postoperative reduction in the image fusion group were 2.1 ± 1.1 mm, 1.8 ± 0.7 mm, 1.9 ± 0.9 mm, and 1.4 ± 0.7 mm for reference points (1), (2), (3), and the barycenter, respectively. The distances between preoperative planning and postoperative reduction in the control group were 3.7 ± 1.0 mm, 2.8 ± 2.0 mm, 1.7 ± 0.8 mm, and 1.8 ± 1.2 mm for reference points (1), (2), (3), and the barycenter, respectively. The difference in reference point (1) was significantly smaller in the image fusion group than in the control group (P < 0.05).

Conclusion

Corrective osteotomy using an image fusion system will become a new surgical support method for fracture malunion.

Trial registration Registered as NCT03764501 at ClinicalTrials.gov.

3D-printed saw guides for lower arm osteotomy, a comparison between a synthetic CT and CT-based workflow

BACKGROUND

Three-dimensional (3D)-printed saw guides are frequently used to optimize osteotomy results and are usually designed based on computed tomography (CT), despite the radiation burden, as radiation-less alternatives like magnetic resonance imaging (MRI) have inferior bone visualization capabilities. This study investigated the usability of MR-based synthetic-CT (sCT), a novel radiation-less bone visualization technique for 3D planning and design of patient-specific saw guides.

METHODS

Eight human cadaveric lower arms (mean age: 78y) received MRI and CT scans as well as high-resolution micro-CT. From the MRI scans, sCT were generated using a conditional generative adversarial network. Digital 3D bone surface models based on the sCT and general CT were compared to the surface model from the micro-CT that was used as ground truth for image resolution. From both the sCT and CT digital bone models saw guides were designed and 3D-printed in nylon for one proximal and one distal bone position for each radius and ulna. Six blinded observers placed these saw guides as accurately as possible on dissected bones. The position of each guide was assessed by optical 3D-scanning of each bone with positioned saw guide and compared to the preplanning. Eight placement errors were evaluated: three translational errors (along each axis), three rotational errors (around each axis), a total translation (∆T) and a total rotation error (∆R).

RESULTS

Surface models derived from micro-CT were on average smaller than sCT and CT-based models with average differences of 0.27 ± 0.30 mm for sCT and 0.24 ± 0.12 mm for CT. No statistically significant positioning differences on the bones were found between sCT- and CT-based saw guides for any axis specific translational or rotational errors nor between the ∆T (p = .284) and ∆R (p = .216). On Bland-Altman plots, the ∆T and ∆R limits of agreement (LoA) were within the inter-observer variability LoA.

CONCLUSIONS

This research showed a similar error for sCT and CT digital surface models when comparing to ground truth micro-CT models. Additionally, the saw guide study showed equivalent CT- and sCT-based saw guide placement errors. Therefore, MRI-based synthetic CT is a promising radiation-less alternative to CT for the creation of patient-specific osteotomy surgical saw guides.

Comparison between Novice and Experienced Surgeons Performing Corrective Osteotomy with Patient-Specific Guides in Dogs Based on Resulting Position Accuracy

Corrective osteotomy has been applied to realign and stabilize the bones of dogs with lameness. However, corrective osteotomy for angular deformities requires substantial surgical experience for planning and performing accurate osteotomy. Three-dimensional printed patient-specific guides (3D-PSGs) were developed to overcome perioperative difficulties. In addition, novices can easily use these guides for performing accurate corrective osteotomy. We compared the postoperative results of corrective osteotomy accuracy when using 3D-PSGs in dogs between novice and experienced surgeons. We included eight dogs who underwent corrective osteotomy: three angular deformities of the radius and ulna, three distal femoral osteotomies, one center of rotational angle-based leveling osteotomy, and one corrective osteotomy with stifle arthrodesis. All processes, including 3D bone modeling, production of PSGs, and rehearsal surgery were carried out with computer-aided design software and a 3D-printed bone model. Pre- and postoperative positions following 3D reconstruction were evaluated by radiographs using the 2D/3D registration technique. All patients showed clinical improvement with satisfactory alignment and position. Postoperative accuracy evaluation revealed no significant difference between novice and experienced surgeons. PSGs are thought to be useful for novice surgeons to accurately perform corrective osteotomy in dogs without complications.

Patient-specific plate for navigation and fixation of the distal radius: a case series

Purpose

Corrective osteotomy of a malunited distal radius conventionally relies on 2D imaging techniques for alignment planning and evaluation. However, this approach results in suboptimal bone repositioning, which is associated with poor patient outcomes. In this case series, we evaluate the use of novel patient-specific plates (PSPs), which feature navigation and fixation of bone segments as preoperatively planned in 3D.

Methods

Ten participants with distal radius malunion underwent CT scans for preoperative alignment planning. Patient-specific guides and plates were designed, 3D-printed, and sterilized for use in corrective surgery of the distal radius. Pre- and postoperative results were compared in regard to clinical, functional, and radiographic outcomes.

Results

The application of a PSP was successful in 7 of the 10 cases. After treatment, the residual alignment error was reduced by approximately 50% compared with conventional treatment. The use of PSPs reduced pain significantly. Pre- and postoperative results were pooled and demonstrated significant correlations between: (1) pain and malpositioning, (2) the range of pro- and supination motion, the MHOQ score, the EQ-5D-5L score and dorsovolar angulation, and (3) MHOQ score and proximodistal translation.

Conclusion

The correlation between malalignment and MHOQ score, EQ-5D-5L score, pain, and range of motion shows that alignment should be restored as well as possible. Compared to the conventional approach, which relies on 2D imaging techniques, corrective osteotomy based on 3D preoperative planning and intraoperative fixation with a PSP has been shown to improve bone alignment and reduce pain.

Level of evidence

IV.

A 3D printed cast for minimally invasive transfer of distal radius osteotomy: a cadaver study

Purpose

In corrective osteotomy of the distal radius, patient-specific 3D printed surgical guides or optical navigation systems are often used to navigate the surgical saw. The purpose of this cadaver study is to present and evaluate a novel cast-based guiding system to transfer the virtually planned corrective osteotomy of the distal radius.

Methods

We developed a cast-based guiding system composed of a cast featuring two drilling slots as well as an external cutting guide that was used to orient the surgical saw for osteotomy in the preoperatively planned position. The device was tested on five cadaver specimens with different body fat percentages. A repositioning experiment was performed to assess the precision of replacing an arm in the cast. Accuracy and precision of drilling and cutting using the proposed cast-based guiding system were evaluated using the same five cadaver arms. CT imaging was used to quantify the positioning errors in 3D.

Results

For normal-weight cadavers, the resulting total translation and rotation repositioning errors were ± 2 mm and ± 2°. Across the five performed surgeries, the median accuracy and Inter Quartile Ranges (IQR) of pre-operatively planned drilling trajectories were 4.3° (IQR = 2.4°) and 3.1 mm (IQR = 4.9 mm). Median rotational and translational errors in transferring the pre-operatively planned osteotomy plane were and 3.9° (IQR = 4.5°) and 2.6 mm (IQR = 4.2 mm), respectively.

Conclusion

For normal weight arm specimens, navigation of corrective osteotomy via a cast-based guide resulted in transfer errors comparable to those using invasive surgical guides. The promising positioning capabilities justify further investigating whether the method could ultimately be used in a clinical setting, which could especially be of interest when used with less invasive osteosynthesis material.

Fused deposition modelling for the development of drug loaded cardiovascular prosthesis

Cardiovascular diseases constitute a number of conditions which are the leading cause of death globally. To combat these diseases and improve the quality and duration of life, several cardiac implants have been developed, including stents, vascular grafts and valvular prostheses. The implantation of these vascular prosthesis has associated risks such as infection or blood clot formation. In order to overcome these limitations medicated vascular prosthesis have been previously used. The present paper describes a 3D printing method to develop medicated vascular prosthesis using fused deposition modelling (FDM) technology. For this purpose, rifampicin (RIF) was selected as a model molecule as it can be used to prevent vascular graft prosthesis infection. Thermoplastic polyurethane (TPU) and RIF were combined using hot melt extrusion (HME) to obtain filaments containing RIF concentrations ranging between 0 and 1% (w/w). These materials are capable of providing RIF release for periods ranging between 30 and 80 days. Moreover, TPU-based materials containing RIF were capable of inhibiting the growth of Staphylococcus aureus. This behaviour was observed even for TPU-based materials containing RIF concentrations of 0.1% (w/w). TPU containing 1% (w/w) of RIF showed antimicrobial properties even after 30 days of RIF release. Alternatively, these methods were used to prepare dipyridamole containing TPU filaments. Finally, using a dual extrusion 3D printer vascular grafts containing both drugs were prepared.

Use of Hausdorff Distance and Computer Modelling to Evaluate Virtual Surgical Plans with Three-Dimensional Printed Guides against Freehand Techniques for Navicular Bone Repair in Equine Orthopaedics

OBJECTIVE

 The aim of this study was to evaluate the surgical execution of a virtual surgical plan (VSP) with three-dimensional (3D) guides against a freehand approach in the equine navicular bone using an automated in silico computer analysis technique.

STUDY DESIGN

 Eight pairs of cadaveric forelimb specimens of adult horses were used in an ex vivo experimental study design with in silico modelling. Limbs received either a 3.5 mm cortical screw according to a VSP or using an aiming device. Using computed tomography and computer segmentation, a comparison was made between the executed screw and the planned screw using the Hausdorff distance (HD).

RESULTS

 Navicular bone mean HD registration error was -0.06 ± 0.29 mm. The VSP with 3D printing demonstrated significantly superior accuracy with a mean deviation of 1.19 ± 0.42 mm compared with aiming device group (3.53 ± 1.24 mm, p = 0.0018). The VSP group was 5.0 times more likely to result in a mean aberration of less than 1.0 mm (95% confidence interval, 0.62-33.4). A 3.5 mm screw with an optimal entry point can have a maximum deviation angle of 3.23 ± 0.07, 2.70 ± 0.06 and 2.37 ± 0.10 degrees in a proximal, dorsal and palmar direction respectively, prior to violating one of the cortical surfaces.

CONCLUSION

 Procedures performed using the 3D guides have a high degree of accuracy, with minimal mean deviations (<1 mm and <1 degree) of a VSP compared with those using the conventional aiming device. The use of VSP and the HD for evaluation of orthopaedic surgeries and outcome measures shows promise for simplifying and improving surgical accuracy.

Current standards and ethical landscape of engineered tissues-3D bioprinting perspective

Tissue engineering is an evolving multi-disciplinary field with cutting-edge technologies and innovative scientific perceptions that promise functional regeneration of damaged tissues/organs. Tissue engineered medical products (TEMPs) are biomaterial-cell products or a cell-drug combination which is injected, implanted or topically applied in the course of a therapeutic or diagnostic procedure. Current tissue engineering strategies aim at 3D printing/bioprinting that uses cells and polymers to construct living tissues/organs in a layer-by-layer fashion with high 3D precision. However, unlike conventional drugs or therapeutics, TEMPs and 3D bioprinted tissues are novel therapeutics and need different regulatory protocols for clinical trials and commercialization processes. Therefore, it is essential to understand the complexity of raw materials, cellular components, and manufacturing procedures to establish standards that can help to translate these products from bench to bedside. These complexities are reflected in the regulations and standards that are globally in practice to prevent any compromise or undue risks to patients. This review comprehensively describes the current legislations, standards for TEMPs with a special emphasis on 3D bioprinted tissues. Based on these overviews, challenges in the clinical translation of TEMPs & 3D bioprinted tissues/organs along with their ethical concerns and future perspectives are discussed.

Application of 3D-printed Customized Guides in Subtalar Joint Arthrodesis

OBJECTIVE

To explore the feasibility of 3D printed customized guides assisting the precise drilling of Kirschner wires in subtalar joint arthrodesis.

METHODS

We retrospectively reviewed the data of 29 patients (30 subtalar joints) who underwent subtalar joint arthrodesis between 1 July 2013 and 31 December 2017. The customized guides were designed on a full-scale 3D polylactic acid model made from computed tomography (CT) data of patients by Model Intestinal Microflora in Computer Simulation (MIMICS) software, which were manufactured by 3D printing technology. A total of 14 joints used customized guides (experimental group); the remained 16 joints used the traditional method (control group). The time of drilling the Kirschner wires to the correct position, the time of subtalar fusion, American Orthopaedic Foot & Ankle Society (AOFAS) scores, and complications were evaluated in both groups.

RESULTS

All customized guides were successfully manufactured. In the experimental group, it took 2.1 ± 0.7 min to drill the Kirschner wire to the satisfactory position, and 2 cases needed to be re-drilled; in the control group, it took 4.6 ± 1.9 min to drill the Kirschner wire to the satisfactory position (P < 0.05), and 8 cases needed to be re-drilled. No serious complications occurred in both groups during and after the surgery. Postoperative radiographic fusion was confirmed in all cases. No significant difference was observed in the fusion time and AOFAS scores 1 year postoperatively between the two groups (P > 0.05).

CONCLUSION

It is safe to apply 3D-printed customized guides for subtalar joint arthrodesis, which can assist the accurate drilling of Kirschner wires into the appropriate position according to the preoperative plan, and reduce the operation time as well as intraoperative radiation.

Implementation of a semiautomatic method to design patient-specific instruments for corrective osteotomy of the radius

PURPOSE

3D-printed patient-specific instruments (PSIs), such as surgical guides and implants, show great promise for accurate navigation in surgical correction of post-traumatic deformities of the distal radius. However, existing costs of computer-aided design and manufacturing process prevent everyday surgical use. In this paper, we propose an innovative semiautomatic methodology to streamline the PSIs design.

METHODS

The new method was implemented as an extension of our existing 3D planning software. It facilitates the design of a regular and smooth implant and a companion guide starting from a user-selected surface on the affected bone. We evaluated the software by designing PSIs starting from preoperative virtual 3D plans of five patients previously treated at our institute for corrective osteotomy. We repeated the design for the same cases also with commercially available software, with and without dedicated customization. We measured design time and tracked user activity during the design process of implants, guides and subsequent modifications.

RESULTS

All the designed shapes were considered valid. Median design times ([Formula: see text]) were reduced for implants (([Formula: see text]) = 2.2 min) and guides (([Formula: see text]) = 1.0 min) compared to the standard (([Formula: see text]) = 13 min and ([Formula: see text]) = 8 min) and the partially customized (([Formula: see text]) = 6.5 min and ([Formula: see text]) = 6.0 min) commercially available alternatives. Mouse and keyboard activities were reduced (median count of strokes and clicks during implant design (([Formula: see text]) = 53, and guide design (([Formula: see text]) = 27) compared to using standard software (([Formula: see text]) = 559 and ([Formula: see text]) = 380) and customized commercial software (([Formula: see text]) = 217 and ([Formula: see text]) = 180).

CONCLUSION

Our software solution efficiently streamlines the design of PSIs for distal radius malunion. It represents a first step in making 3D-printed PSIs technology more accessible.

Application of 3D-Printed Personalized Guide in Arthroscopic Ankle Arthrodesis

Objective

To accurately drill the Kirschner wire with the help of the 3D-printed personalized guide and to evaluate the feasibility of the 3D technology as well as the outcome of the surgery.

Methods

Patients' DICM data of ankle via CT examinations were introduced into the MIMICS software to design the personalized guides. Two 2mm Kirschner wires were drilled with the help of the guides; the C-arm fluoroscopy was used to confirm the position of the wires before applying the cannulated screws. The patients who underwent ankle arthrodesis were divided into two groups. The experimental group adopted the 3D-printed personalized guides, while the control group received traditional method, i.e., drilling the Kirschner wires according to the surgeon's previous experience. The times of completing drilling the Kirschner wires to correct position were compared between the two groups. Regular follow-ups were conducted to statistically analyze the differences in the ankle fusion time and AOFAS scores between the two groups.

Results

3D-printed personalized guides were successfully prepared. A total of 29 patients were enrolled, 15 in the experimental group and 14 in the control group. It took 2.2 ± 0.8 minutes to drill the Kirschner wires to correct position in the experimental group and 4.5 ± 1.6 minutes in the control group (p=0.001). No obvious complications occurred in the two groups during and after surgery. Postoperative radiographs confirmed bony fusion in all cases. There were no significant differences in the fusion time (p=0.82) and AOFAS scores at 1 year postoperatively between the two groups (p=0.55).

Conclusions

The application of 3D-printed personalized guide in assisting the accurate drilling of Kirschner wire in ankle arthrodesis can shorten the operation time and reduce the intraoperative radiation. This technique does not affect the surgical outcome.

Trial Registration Number

This study is registered on www.clinicaltrials.gov with NCT03626935.