Clinical application of 3D printing technology to the surgical treatment of atlantoaxial subluxation in small breed dogs

Ex vivo comparison of pin placement with patient-specific drill guides or freehand technique in canine cadaveric spines

OBJECTIVE

To compare vertebral implant placement in the canine thoracolumbar spine between 3D-printed patient-specific drill guides (3DPG) and the conventional freehand technique (FH).

STUDY DESIGN

Ex vivo study.

ANIMALS

Cadaveric canine spines (n = 24).

METHODS

Implant trajectories were established for the left and right sides of the T10 through L6 vertebrae based on computed tomography (CT) imaging. Customized drill guides were created for each vertebra of interest. Each cadaver was randomly assigned to one of six veterinarians with varying levels of experience placing vertebral implants. Vertebrae were randomly assigned a surgical order and technique (3DPG or FH) for both sides. Postoperative CT images were acquired. A single, blinded observer assessed pin placement using a modified Zdichavsky classification.

RESULTS

A total of 480 implants were placed in 240 vertebrae. Three sites were excluded from the analysis; therefore, a total of 238 implants were evaluated using the FH technique and 239 implants using 3DPG. When evaluating implant placement, 152/239 (63.6%) of 3DPG implants were considered to have an acceptable placement in comparison with 115/248 (48.32%) with FH. Overall, pin placement using 3DPG was more likely to provide acceptable pin placement (p < .001) in comparison with the FH technique for surgeons at all levels of experience.

CONCLUSION

The use of 3DPG was shown to be better than the conventional freehand technique regarding acceptable placement of implants in the thoracolumbar spine of canine cadavers.

CLINICAL SIGNIFICANCE

Utilizing 3DPG can be considered better than the traditional FH technique when placing implants in the canine thoracolumbar spine.

3D-printed, patient-specific cutting guides improve femoral and tibial cut alignment in canine total knee replacement

OBJECTIVES

The purpose of this cadaveric study was to determine whether patient-specific guides (PSGs) improve the accuracy of tibial and femoral cut alignment in canine total knee replacement (TKR), as compared with generic cutting guides.

STUDY DESIGN

Original research.

ANIMALS

Sixteen pelvic limbs from skeletally mature medium- to large-breed canine cadavers.

METHODS

Specimens were randomly allocated to one of two groups (PSG or Generic; N = 8/group). In the Generic group, femoral and tibial ostectomies were made using the standard canine TKR femoral cutting blocks and tibial alignment guide. In the PSG group, the cuts were made using a series of custom 3D-printed cutting guides. "Planned" and "actual" tibial and femoral cut alignments were compared in the frontal and sagittal planes, and errors were calculated by subtracting actual from planned values.

RESULTS

Use of 3D-printed PSGs improved tibial cut alignment in the frontal plane but not the sagittal plane. PSGs also improved the alignment of the cranial and distal femoral ostectomies but did not impact varus-valgus alignment.

CONCLUSIONS

These findings support the use of PSGs for TKR in dogs. Clinical trials are now needed to determine whether the benefits of PSGs translate into measurable improvements in joint function and implant longevity.

CLINICAL SIGNIFICANCE

PSGs have the potential to improve femoral and tibial component alignment in canine TKR.

Students with access to 3D study materials are better able to translate spatial relationships between abdominal organs and correctly interpret abnormal radiographic images

Previous studies have demonstrated evidence that three-dimensional (3D) visualization techniques can be helpful as learning tools. This prospective randomized control study was designed to test the hypothesis that 3D learning tools would have improved translation into interpreting normal and abnormal canine abdominal radiographic images over traditional learning tools. Sagittal and dorsal plane 3D image scenes were created from CT scans, with canine abdominal organs labeled using virtual reality and 3D visualization software tools. Eighty students from the first- and second-year veterinary classes at a single institution participated in the study. The control group studied canine abdominal anatomy from a textbook and the experimental group studied canine abdominal anatomy using the 3D learning tools for a set time. Each participant then took a three-part written examination to assess their learning for the following categories: 3D anatomy organ identification, radiographic anatomy organ identification of normal structures and radiographic anatomy organ identification of abnormal structures. All participants were also asked to identify the sex of the test patient from the 3D study. Participants from the experimental group performed statistically better than participants in the control group for all parts of the examination, with the exception of normal radiographic anatomy.

Preoperative Planning Using Three-dimensional Printing for Full-endoscopic Spine Surgery: A Technical Note

Transforaminal full-endoscopic spine surgery (TF-FESS) is a novel minimally invasive spine surgery that requires only an 8-mm skin incision and causes minimal damage to the paravertebral muscles. To perform TF-FESS safely and efficiently, preoperative planning is quite important as the intervention requires anatomical understanding and high technical skills. Recently, three-dimensional (3D) printing has become a useful tool in various surgeries, and several studies have addressed its efficacy; however, there are no reports on the application of 3D printing to FESS. In this study, we present two cases of severe lumbar deformities for which preoperative 3D printing was useful. The 3D printing enabled the surgeons to visualize and plan the drilling of the superior articular process for a successful foraminoplasty at a low cost. The manufacturing equipment cost about USD 900 and is able to produce an actual-size model at a cost of less than USD 10 per patient. In conclusion, preoperative planning using 3D printing should be adopted to safely perform FESS.

Accuracy of a patient-specific 3D-printed drill guide for placement of bicortical screws in atlantoaxial ventral stabilization in dogs

Atlantoaxial instability (AAI) in dogs refers to abnormal motion at the C1–C2 articulation due to congenital or developmental anomalies. Surgical treatment options for AAI include dorsal and ventral stabilization techniques. Ventral stabilization techniques commonly utilize transarticular and vertebral body screws or pins. However, accurate screw insertion into the vertebrae of C1 and C2 is difficult because of the narrow safety corridors. This study included 10 mixed dogs, 1 Pomeranian, and 1 Shih-Tzu cadaver. All dogs weighed <10 kg. Each specimen was scanned using computed tomography (CT) from the head to the 7th cervical vertebrae. This study used 12 bone models and 6 patient-specific drill guides. Bone models were made using CT images and drill guides were created through a CAD (computer-aided design) program. A total of six cortical screws were used for each specimen. Two screws were placed at each of the C1, C2 cranial, and C2 caudal positions. Postoperative CT images of the cervical region were obtained. The degree of cortex breaching and angle and bicortical status of each screw was evaluated. The number of screws that did not penetrate the vertebral canal was higher in the guided group (33/36, 92%) than in the control group (20/36, 56%) (P = 0.003). The screw angles were more similar to the reference angle compared to the control group. The number of bicortically applied screws in the control group was 28/36 (78%) compared to 34/36 (94%) in the guided group. Differences between the preoperative plan and the length of the applied screw at the C1 and C2 caudal positions were determined by comparing the screw lengths in the guide group. The study results demonstrated that the use of a patient-specific 3D-printed drill guide for AAI ventral stabilization can improve the accuracy of the surgery. The use of rehearsal using bone models and a drilling guide may improve screw insertion accuracy.

Case Report: Clinical Use of a Patient-Individual Magnetic Resonance Imaging-Based Stereotactic Navigation Device for Brain Biopsies in Three Dogs

Three-dimensional (3D) printing techniques for patient-individual medicine has found its way into veterinary neurosurgery. Because of the high accuracy of 3D printed specific neurosurgical navigation devices, it seems to be a safe and reliable option to use patient-individual constructions for sampling brain tissue. Due to the complexity and vulnerability of the brain a particularly precise and safe procedure is required. In a recent cadaver study a better accuracy for the 3D printed MRI-based patient individual stereotactic brain biopsy device for dogs is determined compared to the accuracies of other biopsy systems which are currently used in veterinary medicine. This case report describes the clinical use of this 3D printed MRI-based patient individual brain biopsy device for brain sampling in three dogs. The system was characterized by a simple handling. Furthermore, it was an effective and reliable tool to gain diagnostic brain biopsy samples in dogs with no significant side effects.

Successful Management of and Recovery from Multiple Cranial Nerve Palsies following Surgical Ventral Stabilization in a Dog with Atlantoaxial Subluxation

A 4-year-old spayed female miniature poodle dog presented with a 1-week history of acute tetraparesis. A neurological examination revealed severe neck pain and non-ambulatory tetraparesis. Computed tomography and magnetic resonance imaging showed hypoplastic dens with moderate compression of the spinal cord at C1–C2. The atlantoaxial subluxation (AAS) was surgically stabilized using ventral pins and polymethylmethacrylate (PMMA) cement. On the second postoperative day, the patient showed significant dyspnea, and aspiration pneumonia was identified on radiography. The patient exhibited dysphagia with abnormal food prehension and an inability to protrude the tongue, with no gag reflex. We tentatively diagnosed the patient with multiple cranial nerve (CN) palsies involving the 9th, 10th, and 12th CNs following surgical ventral stabilization. The protruding cranial part of the implanted PMMA cement, which could mechanically contribute to the corresponding CNs dysfunction, was surgically removed. The symptoms gradually improved, and the patient showed normal tongue movement 1 month after revision surgery. In conclusion, we report herein a canine case of multiple CN palsies following ventral stabilization surgery for AAS. The experience gained from this case suggests an optimized management plan for postoperative neurological complications associated with ventral stabilization.

Applications of 3-dimensional printing in small-animal surgery: A review of current practices

Three-dimensional (3D) printing, also called rapid prototyping or additive manufacturing, transforms digital images into 3D printed objects, typically by layering consecutive thin films of material. This technology has become increasingly accessible to the public, prompting applications in veterinary surgery. Three-dimensional prints provide direct visualization of complex 3D structures and also haptic feedback relevant to surgery. The main objective of this review is to report current applications of 3D printing in small-animal surgery, including surgical education, preoperative planning, and treatment of tissue defects. The reported uses of 3D prints, their proposed advantages, and current limitations are discussed considering published evidence. Aspects of the manufacturing process specific to each application are described, along with current practices in veterinary surgery.

Evaluation of a Novel Dorsal-Cemented Technique for Atlantoaxial Stabilisation in 12 Dogs

Dorsal atlantoaxial stabilisation (DAAS) has mostly been described to treat atlantoaxial instability using low stiffness constructs in dogs. The aim of this study was to assess the feasibility and surgical outcome of a rigid cemented DAAS technique using bone corridors that have not previously been reported. The medical records of 12 consecutive dogs treated with DAAS were retrospectively reviewed. The method involved bi-cortical screws placed in at least four of eight available bone corridors, embedded in polymethylmethacrylate. Screw placement was graded according to their position and the degree of the breach from the intended bone corridor. All DAAS procedures were completed successfully. A total of 72 atlantoaxial screws were placed: of those, 51 (70.8%) were optimal, 17 (23.6%) were suboptimal, and 4 (5.6%) were graded as hazardous (including 2 minor breaches of the vertebral canal). Surgical outcome was assessed via a review of client questionnaires, neurological examination, and postoperative CT images. The clinical outcome was considered good to excellent in all but one case that displayed episodic discomfort despite the appropriate atlantoaxial reduction. A single construct failure was identified despite a positive clinical outcome. This study suggests the proposed DAAS is a viable alternative to ventral techniques. Prospective studies are required to accurately compare the complication and success rate of both approaches.

Feasibility and accuracy of 3D printed patient-specific skull contoured brain biopsy guides

Objective

Design 3D printed skull contoured brain biopsy guides (3D‐SCGs) from computed tomography (CT) or T1‐weighted magnetic resonance imaging (T1W MRI).

Study Design

Feasibility study.

Sample Population

Five beagle dog cadavers and two client‐owned dogs with brain tumors.

Methods

Helical CT and T1W MRI were performed on cadavers. Planned target point was the head of the caudate nucleus. Three‐dimensional‐SCGs were created from CT and MRI using commercially available open‐source software. Using 3D‐SCGs, biopsy needles were placed into the caudate nucleus in cadavers, and CT was performed to assess needle placement accuracy, followed by histopathology. Three‐dimensional‐SCGs were then created and used to perform in vivo brain tumor biopsies.

Results

No statistical difference was found between the planned target point and needle placement. Median needle placement error for all planned target points was 2.7 mm (range: 0.86–4.5 mm). No difference in accuracy was detected between MRI and CT‐designed 3D‐SCGs. Median needle placement error for the CT was 2.8 mm (range: 0.86–4.5 mm), and 2.2 mm (range: 1.7–2.7 mm) for MRI. Biopsy needles were successfully placed into the target in the two dogs with brain tumors and biopsy was successfully acquired in one dog.

Conclusion

Three‐dimensional‐SCGs designed from CT or T1W MRI allowed needle placement within 4.5 mm of the intended target in all procedures, resulting in successful biopsy in one of two live dogs.

Clinical Significance

This feasibility study justifies further evaluation of 3D‐SCGs as alternatives in facilities that do not have access to stereotactic brain biopsy.

Time Reduction by Prebending Osteosynthesis Plates Using 3D-Printed Anatomical Models, In Patients Treated With Open Reduction and Internal Fixation

INTRODUCTION

The incidence of facial bones fractures is 18 to 32 for each 100,000 inhabitants. The most affected population are young working people. Fractures are most commonly caused by assaults and motor vehicle accidents. Its cost of care reaches 1.06 billion dollars. Premodeling osteosynthesis plates with anatomical models can decrease surgical time, bleeding, and increase patient satisfaction. This study aims to evaluate the impact of premodeled osteosynthesis plates, using anatomical models in patients with facial fractures.

MATERIAL AND METHODS

Patients with facial fractures treated by open reduction and internal fixation were included-Group A without premolding plates and Group B with premolding. The variables studied were: age, sex, etiology of the fractures, number of fractures, among other variables that reflect the quality of the results.

RESULTS

A total of 17 osteosynthesis plates were included in 6 patients. The age was 22 to 47 years; all patients were male. The maximum surgery time was 129 to 300 minutes. The average time to start work was 4.8 weeks. When comparing the variables between the groups, we found no difference between the groups for bleeding P = 0.24, the start of work P = 0.19, the time of surgery P = 0.082, or for osteosynthesis time P = 0.15. There was only a significant difference in patient satisfaction, P = 0.04.

CONCLUSIONS

The evidence collected shows that premodeling the plates only improves patients' satisfaction among facial fractures treated by open reduction and internal fixation.

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.

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

OBJECTIVE

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

STUDY DESIGN

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

RESULTS

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

CONCLUSION

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