The Barrow Biomimetic Spine: Face, Content, and Construct Validity of a 3D-Printed Spine Model for Freehand and Minimally Invasive Pedicle Screw Insertion

Biomechanical Analysis of Pedicle Screw Reinsertion Along the Same Trajectory in a Validated 3D-Printed Synthetic Bone Model

OBJECTIVE

To investigate the biomechanical properties of pedicle screw reinsertion along the same trajectory in a previously validated synthetic bone model.

METHODS

Twenty identical acrylonitrile butadiene styrene models of lumbar vertebrae were three-dimensional-printed. Screws were placed in the standard fashion into each pedicle. Models were separated into 2 equal groups, control and experimental. Experimental group screws were completely removed from their testing block and reinserted once. All screws in both groups were then forcibly removed. Continuous torque monitoring was collected on screw insertion torque (IT), removal torque, and reinsertion torque. Pullout strength (PO), screw stiffness (STI), and strain energy (STR) were calculated.

RESULTS

There was no significant difference between control and experimental groups for PO (P = 0.26), STI (P = 0.55), STR (P = 0.50), or IT (P = 0.24). There was a significant decrease in reinsertion torque (54.5 N-cm ± 8.2 N-cm) from control IT (62.9 N-cm ± 8.4 N-cm, P = 0.045) and experimental IT (67.5 N-cm ± 7.6 N-cm, P = 0.0026). Strong correlations (Pearson's r > 0.80) were seen between control IT against STR and PO, between each of the experimental torque measurements, and between experimental PO and STI.

CONCLUSIONS

Despite a significant decrease in insertion torque, there is no significant loss of pedicle screw performance when a screw is removed and reinserted along the same trajectory.

Image Guided Interpedicular Screw Placement Simulation System for Training and Skill Evaluation. Proof of Concept

BACKGROUND

The SpineST-01 system is an image-guided vertebrae cannulation training system. During task execution, the computer calculates performance-based metrics displaying different visual perspectives (lateral view, axial view, anteroposterior view) with the position of the instrument inside the vertebra. Finally, a report with the metrics is generated as performance feedback.

METHODS

A training box holds a 3D printed spine section. The computer works with 2 orthogonally disposed cameras, tracking passive markers placed on the instrument. Eight metrics were proposed to evaluate the execution of the surgical task. A preliminary study with 25 participants divided into 3 groups (12 novices, 10 intermediates, and 3 expert) was conducted to determine the feasibility of the system and to evaluate and assess the performance differences of each group using Kruskal-Wallis analysis and Mann-Whitney U analysis. In both analyses, a P value ≤ 0.05 was considered statistically significant.

RESULTS

When comparing experts versus novices and all 3 groups, statistical analysis showed significant differences in 6 of the 8 metrics: axial angle error (°), lateral angle error (°), average speed (mm/second), progress between shots (mm), Time (seconds), and shots. The metrics that did not show any statistically significant difference were time between shots (seconds), and speed between shots (mm/second). Also, the average result comparison placed the experts as the best performance group.

CONCLUSIONS

Initial testing of the SpineST-01 demonstrated potential for the system to practice image-guided cannulation tasks on lumbar vertebrae. Results showed objective differences between experts, intermediates, and novices in the proposed metrics, making this system a feasible option for developing basic navigation system skills without the risk of radiation exposure and objectively evaluating task performance.

Expanding Clinician Access to High-Quality, Low-Cost Biomechanical Research: A Technical Report on the Carolina Neurosurgery and Spine Biomechanics Laboratory

Spine biomechanical research helps us better understand the spine in physiologic and pathologic states and gives us a mechanism by which to evaluate surgical interventions, generate and evaluate models of spine pathologies, and develop novel, data-driven surgical strategies and devices. Access to a biomechanical testing laboratory is therefore potentially invaluable to those who specialize in treating spine pathologies. A number of barriers to access have precluded many clinicians from pursuing their biomechanical research interests, foremost among these is cost. The Carolina Neurosurgery and Spine Biomechanics Research Laboratory (CNSBL) was developed as a model of a low-cost, easy-to-access laboratory capable of generating high-quality data in tests of axial load, tension, torque, displacement, and pathological model testing. Our experience in developing this laboratory suggests that a large number of basic biomechanical research inquiries can be studied in a laboratory composed of less than $7500 USD of hardware. We hope that this model serves as a roadmap for any like-minded practitioners seeking broader access to biomechanical testing facilities.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Utility of 3-dimensionally printed models for parent education in pediatric plagiocephaly

Objectives

Demonstrate the benefits of using 3D printed skull models when counseling families regarding disorders of the cranial vault (namely plagiocephaly and craniosynostosis), as traditional imaging review and discussion is often insufficient.

Methods

3D printed skull models of a patient with plagiocephaly were used during clinic appointments to aid in the counseling of parents. Surveys were distributed following the appointment to evaluate the utility of these models during the discussion.

Results

Fifty surveys were distributed (with a 98% response rate). 3D models were both empirically and anecdotally helpful for parents in understanding their child's diagnosis.

Conclusion

Advances in 3D printing technology and software have made producing models more accessible. Incorporating physical, disorder-specific models into our discussions has led to improvements in our ability to communicate with our patients and their families.

Innovation

Disorders of the cranial can be challenging to describe to the parents and guardians of affected children; using 3D printed models is a useful adjunct in patient-centered discussions. The subject response to the use of these emerging technologies in this setting suggests a major role for 3D models in patient education and counseling for cranial vault disorders.

3D-Printed Disease Models for Neurosurgical Planning, Simulation, and Training

Spatial insight into intracranial pathology and structure is important for neurosurgeons to perform safe and successful surgeries. Three-dimensional (3D) printing technology in the medical field has made it possible to produce intuitive models that can help with spatial perception. Recent advances in 3D-printed disease models have removed barriers to entering the clinical field and medical market, such as precision and texture reality, speed of production, and cost. The 3D-printed disease model is now ready to be actively applied to daily clinical practice in neurosurgical planning, simulation, and training. In this review, the development of 3D-printed neurosurgical disease models and their application are summarized and discussed.

Utility of a Novel Biomimetic Spine Model in Surgical Education: Case Series of Three Cervicothoracic Kyphotic Deformities

STUDY DESIGN

Evaluation of new technology.

OBJECTIVES

To evaluate the utility of a novel biomimetic spine model as a surgical planning and education resource in the treatment of cervical spine deformities (CSD).

METHODS

Three patients with CSD were identified and synthetic spine models were manufactured to match the anatomical and biomechanical properties of each patient. Each model underwent 3 phases of surgical correction: maximum correction with no osteotomies performed, with posterior column osteotomies (PCOs) only, and with PCOs and a 3-column osteotomy (3CO). Lateral fluoroscopic films were obtained after each phase of correction for measurement of cervical lordosis. Surgeons were surveyed to obtain subjective feedback on the perceived model utility.

RESULTS

Each model began with a kyphotic deformity that was mobile, rigid, or fixed. The mobile model achieved successive lordotic correction with each phase of correction. The rigid and fixed models achieved much less correction with no osteotomies and PCOs only, and the majority of correction with 3COs. Each model predicted with varying, but overall high, accuracy the amount of correction achieved in each patient. The surgeons felt the model had very high utility as a surgical education platform.

CONCLUSIONS

The models appeared to accurately replicate the gross anatomy and biomechanical performance of the patients' spines. This high fidelity to the individual patient's anatomy, bone quality, and segmental mobility resulted in a custom model that provides an invaluable learning platform for surgical education. These results suggest the models may have utility in surgical planning, but further studies are needed.

The Living Spine Model: A Biomimetic Surgical Training and Education Tool

BACKGROUND

The Living Spine Model (LSM) is a three-dimensionally printed, surgical training platform developed by neurosurgical residents.

OBJECTIVE

To evaluate the face and content validity of this model as a training tool for open posterior lumbar surgery.

METHODS

Six surgeons with varying experience were asked to complete L3-5 pedicle screw fixation and L3-4 laminectomy on an LSM. Face validity was measured using a questionnaire, and content validity was measured using the National Aeronautics and Space Administration Task Load Index (NASA TLX) tests. Student's t-test was used to compare NASA TLX responses between junior and senior residents and to compare responses for live surgery vs simulated surgery on the LSM.

RESULTS

Junior residents took the longest time to complete the procedure, followed by senior residents and the attending surgeon (136.5, 98.3, and 84 min, respectively). The junior residents placed fewer successful pedicle screws (7/12) than senior residents and attending surgeon (18/18). All tested components of the model had excellent face validity, with scores ranging from 60% to 97%. Content validity testing demonstrated that the LSMs created overall workloads and specific types of work like live operating conditions.

CONCLUSION

The overall validity testing of the LSM demonstrates the high-potential utility of this model as a surgical education and testing platform for open posterior lumbar procedures. The LSM has great potential as an adjunct to surgical education, and it may become an increasingly important component of surgical resident curricula in the future.

Development and first clinical use of a novel anatomical and biomechanical testing platform for scoliosis

BACKGROUND

Previous studies have demonstrated that, by using various three-dimensional (3D) printing technologies, synthetic spine models can be manufactured to mimic a human spine in its gross and radiographic anatomy and the biomechanical performance of bony and ligamentous tissue. These manufacturing processes have not, however, been used in combination to create a long-segment, biomimetic model of a patient with scoliosis. The purpose of this study was to describe the development of a biomimetic scoliosis model and early clinical experience using this model as a surgical planning and education platform.

METHODS

Synthetic spine models were printed to mimic the anatomy and biomechanical performance of 2 adult patients with scoliosis. Preoperatively, the models were surgically corrected by the attending surgeon of each patient. Patients then underwent surgical correction of their spinal deformities. Correction of the models was compared to the surgical correction in the patients.

RESULTS

Patient 1 had a preoperative coronal Cobb angle of 40° from L1 to S1, as did the patient's synthetic spine model. The patient's spine model was corrected to 17.6°, and the patient achieved a correction of 17.3°. Patient 2 had a preoperative mid-thoracic Cobb angle of 88° and an upper thoracic Cobb angle of 43°. Preoperatively, the patient's spine model was corrected to 19.5° and 9.2° for the mid-thoracic and upper thoracic curves, respectively. Immediately after surgery, the patient's mid-thoracic and upper thoracic Cobb angles measured 18.7° and 9.5°, respectively. In both cases, the use of the spine models preoperatively changed the attending surgeon's operative plan.

CONCLUSIONS

A novel synthetic spine model for corrective scoliosis procedures is presented, along with early clinical experience using this model as a surgical planning platform. This model has tremendous potential not only as a surgical planning platform but also as an adjunct to patient consent, surgical education, and biomechanical research.