Three-dimensional technologies in presurgical planning of bone surgeries: current evidence and future perspectives

Background:

The recent development of three-dimensional (3D) technologies introduces a novel set of opportunities to the medical field in general, and specifically to surgery. The preoperative phase has proven to be a critical factor in surgical success. Utilization of 3D technologies has the potential to improve preoperative planning and overall surgical outcomes. In this narrative review article, the authors describe existing clinical data pertaining to the current use of 3D printing, virtual reality, and augmented reality in the preoperative phase of bone surgery.

Methods:

The methodology included keyword-based literature search in PubMed and Google Scholar for original articles published between 2014 and 2022. After excluding studies performed in nonbone surgery disciplines, data from 61 studies of five different surgical disciplines were processed to be included in this narrative review.

Results:

Among the mentioned technologies, 3D printing is currently the most advanced in terms of clinical use, predominantly creating anatomical models and patient-specific instruments that provide high-quality operative preparation. Virtual reality allows to set a surgical plan and to further simulate the procedure via a 2D screen or head mounted display. Augmented reality is found to be useful for surgical simulation upon 3D printed anatomical models or virtual phantoms.

Conclusions:

Overall, 3D technologies are gradually becoming an integral part of a surgeon’s preoperative toolbox, allowing for increased surgical accuracy and reduction of operation time, mainly in complex and unique surgical cases. This may eventually lead to improved surgical outcomes, thereby optimizing the personalized surgical approach.

Highlights

• Three-dimensional (3D) technologies introduce a novel set of opportunities to the medical field in general, and specifically to surgery.

• Utilization of 3D technologies has the potential to improve presurgical planning thereby increasing surgical accuracy and reducing operation time.

• 3D printing is currently the most advanced application in terms of clinical use, predominantly creating anatomical models and patient-specific instruments.

• Virtual reality allows to set a surgical plan and to further simulate surgical procedures, while augmented reality is found to be useful for surgical simulation upon 3D printed anatomical models or virtual phantoms.

• Integration of the various 3D technologies may provide a synergistic effect that will enhance surgical preparation and outcomes.

Introduction

Background

The significance of preoperative planning on surgical success is well understood as reflected by clinical outcomes. During the preoperative phase, information is acquired from images to better understand the patient’s anatomy and the relevant pathological condition, thus allowing the surgeon to devise a surgical plan including the type of surgery and the appropriate surgical approach. The techniques used for preoperative planning have improved and increased the surgeon’s efficiency and accuracy as reflected by reduced operation time, complications, and postoperative hospitalization period1–3. Computed tomography (CT) and MRI were introduced in the 1970s and quickly became the gold standard for collecting patient-specific anatomical data prior to the surgery. In the following decade, as CT imaging evolved and enabled three-dimensional (3D) image reconstruction by volume rendering, surgeons were able to better perceptualize the patient’s anatomy4,5. The next significant stage in presurgical planning development took place when additive manufacturing (AM) was introduced to the medical field in the mid-1990s6. The first method to be introduced was stereolithography. This process utilizes 2D slices collected by various modalities and converts them into a highly accurate and specific prototype of a particular anatomical structure in a 3D physical model6. The same data was later used to create a virtual 3D model and the tool known as virtual surgical planning (VSP) which allows for realistic exploration of surgical objectives. This technology was introduced to the clinical field in the early 2000s and is being used today in different surgical disciplines aiding surgeons in mastering the patient’s anatomy prior to surgery and setting the ultimate surgical plan7. We can expect the use of augmented reality (AR) technologies for superimposing models on patients and physical models both preoperatively and intraoperatively8 (Fig. 1). This technology is still in its preliminary phase. The gold standard in presurgical planning remains visualization of 2D images acquired by radiography, CT, MRI, or ultrasound9. In some medical disciplines and in particularly complex cases that require higher precision, the method of choice is a virtual or physical 3D reconstructed model from CT or MRI10,11.

Figure 1.

Chronological development of visualization techniques used for presurgical planning. AR, augmented reality; CT, computed tomography; VR, virtual reality; VSP, virtual surgical planning.

AM and extended realities

AM allows production of both anatomical models and patient-specific instruments (PSIs), which may have a significant impact on surgical precision and operation time. Current technology allows to create accurate models at a 1 : 1 ratio with the original structure. Furthermore, the variety of different materials that can be used to mimic real tissue consistency and texture, allows surgeons to examine any specific organ in an isolated and detailed manner.

3D printed anatomical models have recently started to be used in several medical centers as a precise preoperative tool to simulate patient’s anatomical structures based on imaging data7,12.

In cases where there is a pathological alteration of the original anatomy or the patient presents with anatomical variations, printing patient-specific models can be advantageous and useful when planning a procedure13,14. Additionally, the use of 3D printed PSIs has gained much popularity in clinical practice. This includes the production of aiding devices for intraoperative procedure guidance, internal and external protheses, and other biocompatible implants. All of these are accurately manufactured and designed according to the patient’s specific anatomy. The traditional method of using pre-formed instruments of fixed sizes and shapes may require a compromise. With the use of PSI printing, the surgeons can raise the bar when it comes to precision and compatibility of instruments and devices15,16.

‘Extended reality’ (XR) is an umbrella term that is used to illustrate a fully immersive real-life experience within a virtual world. It includes all the enveloping technologies that are built to extend the users’ reality. Different technologies are available that allow the user to experience this reality-virtuality continuum according to the degree of immersivity17. Virtual reality (VR) creates a completely digital, simulated 3D environment. No real-life elements are incorporated into the experience18. AR refers to the partial immersion of the user in a simulation where virtual elements are superimposed onto the real-life experience. The perception of real-life elements can be either transmitted through a camera-based device that will display a digital video on the device’s screen (Pass-through AR), or directly seen through a semitranslucent see-through screen (See-through AR)18 (Fig. 2). For instance, the surgical plan (e.g. an incision site or osteotomy line) can be projected intraoperatively on the patient’s body for guidance, using AR (either displayed on a 2D smartphone screen through the camera or on a head mounted display (HMD)19,20.

Figure 2.

Visualization principle of head mounted display based on different extended reality technologies – VR; Pass-through AR; See-through AR.

Unlike other parenchymatous organs and soft tissue, the shape and borders of bones are usually well defined and quite resistant to physical manipulations. This allows bones to maintain their approximate location within the body and its relations with adjacent structures21. These unique characteristics make bony structures, among the different body tissues, ‘ideal’ for 3D model production for preoperative planning, either physically or virtually.

In this narrative review, we selected prominent and innovative original articles from the years 2014 to 2022 describing the use of 3D technologies (3D printing, VR, and AR) in presurgical planning in different bone surgery disciplines [orthopedics, spine, craniomaxillofacial (CMF), otorhinolaryngology, and neurosurgery]. These technologies are rapidly evolving, and we believe that their impact will be revolutionary for the field of surgery in the near future.

Surgical disciplines

Orthopedic surgery

Orthopedic surgery is the leading specialty in incorporation of 3D printing in its line of work22. 3D printing in orthopedics is used in a variety of sub-specialties, including traumatology, orthopedic oncology, and various arthroplasty procedures.

The use of 3D printed models was found to be an effective method compared to traditional planning methods with regards to presurgical planning of traumatic fracture procedures23–25. Chen and colleagues reported in a study of 48 cases of reconstruction of complex radius fractures that 3D visualization assisted the surgeons in choosing the appropriate surgical approach and the type of fixation. Furthermore, operation time was significantly reduced in the 3D model group compared to the control group (66.5±5.3 vs.75.4±6.0 min, P<0.001), as well as a reduction in blood loss (41.1±7.5 vs. 54.2±7.9 ml respectively, P<0.05) and a reduction in the use of fluoroscopy (4.4±1.4 vs. 5.6±1.6 times, respectively, P=0.011)23.

The use of PSIs allows for a variety of precise procedures to be performed and has increased in the last years26–29. De Vloo et al.26 demonstrated the advantage of PSIs in components sizing and alignment during knee replacement surgery. Sun et al. 27 showed an effective use of intramedullary patient-specific guides to control femoral component rotation and Gouin et al.29 facilitated a pelvic tumor resection using a PSI. Anatomical models can be used as templates for the design of patient-specific precontoured plates. These personalized plates can then be reprinted in a sterile environment or undergo sterilization and be taken into the operation room. Such plates were used for acetabular fracture fixation and shown to reduce operation times and blood loss, while providing satisfactory clinical outcomes with good reduction quality24,30,31.

Using patient-specific printed models for planning complex total hip arthroplasty have showed superior clinical, logistical, and educational outcomes compared to the traditional planning based on CT or radiography32,33. Planning that included 3D printed models and PSIs (alongside 3D virtual planning) showed better clinical outcomes28,34,35. In a randomized study, Zhang et al.28 demonstrated an increased accuracy of anteversion restoration (5.42±3.65° vs. 2.32±1.89°, respectively, P<0.001) and a reduction in the rate of abnormal cases (8.7 vs. 50% respectively). Jiang et al.32, Knafo et al.36, and Di Laura et al.37 showed that using VR for visualization in planning such surgeries provides excellent accuracy in predicting implant sizes, therefore enabling reduction and optimization of implant inventory size. Li et al.33 and Sariali et al.38 described that VR visualization also provides great accuracy in implant positioning without increasing operation time.

Regarding shoulder replacement surgeries, Werner et al. 39 and Min et al.40 reported on several cases in which implant selection was changed upon using 3D planning, due to better identification of glenoid Walch classification.

3D technologies also provide an effective solution for planning and optimizing corrective surgeries in pediatric orthopedics41–44. Frizziero and colleagues described an integrated approach to complex limb deformity surgeries, including the use of VSP and 3D printing in five different cases. VSP and computer-assisted simulation aided the surgeons in choosing the proper surgical approach while 3D printed models and PSI were used intraoperatively to overcome visualization limitations and execute precise osteotomies41.

Spine surgery

The use of anatomical models in spine surgeries has broadened the understanding of spatial anatomy and increased surgical precision45,46. Furthermore, the use of 3D printed models enhanced the accuracy of screw placement and reduced key poor prognostic factors such as postoperative complications, operation time, and blood loss45,47,48.

In a study conducted by Tan and colleagues, 3D printed spinal models were used for presurgical planning of severe spinal deformity correction surgeries. These models allow the surgeon to confirm the patient-specific anatomy (curve apex, dysmorphic features, fusion mass, and pedicles position) and to further define the screws position and mark the entry point on the models. After sterilization, the models were used intraoperatively as reference for the pedicle screw entry point. A total of 513 freehand pedicle screws were placed in 23 patients with severe spinal deformities. Overall, 494 screws (96.3%) were placed in acceptable position according to the preoperative plan. The results were compared to a historical cohort and showed as good as results, with no significant statistical difference (P=0.99), although the historical cohort included less severe spinal deformities45.

Immersive VR technology was found to be useful in choosing the optimal surgical technique and strategy compared to conventional planning method49,50. In a study conducted by Alsofy and colleagues, preoperative planning with VR for monosegmental lumbar fusion allowed the surgeons to choose minimal invasive surgery more frequently over open fusion surgery, which is correlated with less perioperative complications and shorter procedure time. The authors suggest that the impact of 3D-VR on the surgical strategy may be due to the improved spatial presentation of the pathological structures compared to 2D images and the ability to recognize specific pathologies (such as defects in the pars interarticularis which may be difficult to detect in 2D imaging-based methods)50.

Zheng and colleagues compared VR-based planning to conventional methods for lateral endoscopic lumbar discectomy surgeries. During the presurgical planning, the entry point, entry angle and depth were recorded and compared to the actual surgical values. The VR-based planning showed statistical correlation between the planned and actual puncture entry point and entry angle but not in the depth values. In contrast, the conventional method planning showed correlation with the depth values but not with entry point and angle51.

Salvatore and colleagues, compared preoperative planning using VR-based google cardboard technology compared to traditional 2D computer-based surgery planning for adolescent idiopathic scoliosis surgery. The study revealed reduced operation time, blood loss, and postsurgical hospitalization time for the VR-based group52.

VR presurgical simulation was found to be a useful method compared to conventional simulations for screw placement in several cadaver studies, improving the accuracy and success rate in pedicle screw fixation53–55. Hou and colleagues assessed cervical pedicle screw fixation procedures. The experimental group was trained on cervical drilling and pedicle screw placement in VR computer-based systems while the control group had conventional teaching sessions. The VR-based learning group had a significantly better (36/40) success rate for inserting screws that defined as ‘grade 1’ (no perforation) compared to a (15/40) success rate in the control group (P<0.05)53.

CMF surgery and otorhinolaryngology

In orthognathic surgery, an occlusal splint was printed for intraoperative use in maxillary advancement surgery based on a virtual model56. In a maxillary tumor removal surgery, a biocompatible patient-specific implant made of polycaprolactone mesh was designed and printed according to the virtual model to replace the bony structure of the orbital floor57.

Gao and colleagues and Jiang and colleagues described orthognathic procedure simulations performed on 3D printed mandibles using AR-guidance, based on the VR preoperative plan for mandibular split osteotomy or dental implant surgery, respectively. The establishment of accurate well-planned procedures allowed the surgeons to act more efficiently during the surgery and reduce the operation time without compromising the performance58,59. Similar settings were carried out in an actual temporomandibular joint arthroplasty surgery as well. Preoperative planning included the formation of a 3D virtual model, joint restoration planning on that model followed by AR-guidance intraoperatively. Preoperative planning reduced operation time from an average of 300 minutes in the traditional procedure to an average of 134 minutes (P=0.03) in the AR-guided procedure19.

In addition, applying VR-based technologies were shown to shorten the preoperative phase as well. Zaragoza-Siqueiros et al. 60 reported that the use of 3D virtual planning significantly shortened several preoperative steps including facial analysis (22±4.73–3.2±1.04 min), cephalometric analysis (43±4.02–8.2±3.37 min), and model surgery procedure (127±10.2–9.7±2.93 min).

VR implementation was described in several CMF surgeries such as tumor resection surgery, dental implant positioning, fracture reduction, and other osteotomy procedures. In these cases, a high degree of accuracy was obtained in terms of linear and angular deviations (reflected as a lesser error than the defined threshold) when compared to the preoperative plan. In surgeries using intraoperative AR-based guidance, a high degree of adherence to the VR plan was observed57,61–63. Jiang et al.59 showed that osteotomy performed using preoperative image-to-patient registration and AR-guidance was more accurate than the traditional osteotomy registration and procedure.

The accuracy of VR-based surgery planning has also been evident in several bone reconstruction surgeries such as cranial vault reconstruction, maxillary reconstruction, and nasal deformity correction. To perform the surgery and achieve the desired precision, 3D virtual models were created prior to the operation with the incision or osteotomy line designed in a particular plane. This model was later projected on the patient to accurately guide the procedure intraoperatively. The outcomes were evaluated by the standard measures for each procedure – mean metric errors, cranial volume asymmetry, patient’s satisfaction and more – and regarded as a powerful tool that may provide valuable treatment possibilities, especially when combined with AR-guidance57,64–66.

Surgeons aided by such techniques commonly expressed high grade of satisfaction regarding the procedure and indicated several benefits. Creation of a VR model of the object, visualized with an HMD was reported to help surgeons understand the patient’s anatomy with good perceptual accuracy, enhancing tumor demarcation and improving the assessment of tumor extent and volume of infiltration. Such planning was also appraised as an essential factor in setting an appropriate primary (and additional) surgical plan and enhance surgical safety61,67–69.

Neurosurgery

3D printed models play a crucial role in preoperative planning and simulation of neurosurgeries. In complex surgeries (e.g. base of skull tumor resections), they allow for a precise understanding of the spatial anatomy and relationship between the tumor and important structures such as blood vessels and nerves in this complex region13,70–72.

Guo and colleagues printed 3D models for skull base meningiomas and compared the results to conventional surgical planning. The models were used for presurgical simulation and allowed the team to examine several surgical approaches and their relation to important neurovascular structures. Furthermore, the surgeons used the 3D models to improve patient education and cooperation by showing them the 3D printed model preoperatively and explaining the specific pathology, surgical plan, complications, and risks71.

VR preoperative planning proved to be valuable in surgery by allowing for a better understanding of the regional anatomy, better recognition of the specific pathology, and even optimizing the patients’ head position73–76. Louis et al.73 used VR preoperative planning with further intraoperative AR navigation and verified it as a beneficial tool for surgical planning in addition to improving safety and efficiency of the procedure. Su and colleagues, conducted a study to validate the use of haptic-based VR simulations for lateral ventricular puncture operations. The haptic-based device was found to be realistic and allowed the surgeons to combine the visual field with a more realistic tissue feeling and consistency77.

The use of AR in neurosurgical planning is mainly used for precise incision, surgical instruments planning, and tumor localization. Shu and colleagues and Ivan and colleagues described the use of a smartphone AR application to view the 3D images directly on the patient body prior to the surgery. The pictures allowed the surgeons to locate the tumor projections and to mark the tumor scalp localization78–80. Incekara and colleagues reported on the use of AR in 25 cases. The study compared AR to standard neuronavigation as a presurgical planning procedure tool. The surgeons reported improved ergonomics and increased concentration when using AR. On the other hand, the preoperative time was longer in the AR-based group compared to the standard neuronavigational method and the registration accuracy deviated 0.4 cm more than the standard neuronavigational method78.

Furthermore, AR technology was shown to provide a reliable method for presurgical training and simulation in combination with 3D printed models81,82. In a study performed by Coelho and colleagues, simulation of metopic craniosynostosis correction surgery was done using AR and 3D printed model. Patients’ CT scans were imported and used with an AR mobile application to create 3D printed silicone models for image overlay. The simulation was done in a ‘step by step’ approach, identical to real previous surgeries. This hybrid model allowed more surgeons (N=38) to simulate the surgery. This experience was found to be a useful tool for practice and education purposes82.

Discussion

3D technologies such as AM and XR aim to deal with the most challenging limitations seen today in surgery: (1) the lack of realistic and accurate visualization methods, (2) the attempt to standardize the patient-specific approach in surgery, and (3) the need to better prepare surgeons in a risk-free environment.

Production of anatomical models provides a solution for the lack of visualization ability, thus enabling a comprehensive and intuitive perception of surgical objectives. This may eliminate many operative difficulties that reside in spatial understanding and will enhance the surgeon’s ability to consider anatomical variations between patients. Subsequently, the surgeon could use the printed model to simulate a model surgery which meets the need to prepare surgeons in safe settings, especially relevant for training novice surgeons.

PSI printing is already becoming a ‘game-changing’ factor in patient-specific surgery. PSIs allow perfect anatomical matching, enhance surgical accuracy and safety, and may generate more patient-specific surgeries that were not possible before.

VSP has a clear advantage in the preoperative phase, especially when displayed using an HMD by creating a realistic immersive visualization experience. XR as well provides a proper solution for each of the mentioned challenges. Moreover, it does not require printing facilities and is a relatively simplistic and instant process that can create a detailed, patient-specific virtual model. Accessibility to VR HMD in surgical departments can be an effective tool allowing preoperative virtual exploration of patient’s anatomical data and enable simulating in a risk-free environment. Young surgeons can acquire important surgical skills (e.g. screw placing in spine and orthopedic surgery). To further increase the degree of realism different technologies are currently studied (e.g. haptic feedback systems).

Compared to the other 3D technologies, the usage of AR in the preoperative phase is still minimal. It is mostly being considered for its intraoperative use as a navigation system. Preoperatively, AR can be integrated into the simulation process in which the virtual model is registered on a patient-specific 3D anatomical model. ‘See-through’ AR can create a partially immersive experience that allows visualization of the virtual model and plan, while preserving the surgeon’s visual field. As AR use increases intraoperatively, such simulations will become even more valuable. Feasible and simple methods that can be initially used are smartphone-based AR applications that show good clinical results20,80,83.

Current limitations

In this paper, we present data about the applications and clinical importance of 3D technologies in bone surgeries planning. However, it is important to consider current limitations and the actual practicality of such technologies. The major limitation of implementing 3D technologies is their high cost. First, 3D image workflow usually requires multiple imaging modalities (e.g. CT and MRI) that are expensive and are not available in every medical center. Second, specific equipment for each technology needs to be purchased and maintained. Furthermore, implementation of these technologies requires coordination of a multidisciplinary team of medical engineers, designers, surgeons, and other personnel. All the mentioned factors must be evaluated against the advantages of 3D technologies and their financial implications – reduced operation time, complications, and postoperative hospitalization. Several possible solutions have already been introduced to improve the cost effectiveness and increase accessibility of 3D technologies by using point-of-care 3D printing centers, low-cost 3D-printers, open-source software, and reusable materials42,84. At the same time, regulation and guidelines are necessary in order to keep high standards of safety and quality while applying these solutions85.

In the case of AR, the major limitation of the technology is the registration accuracy – the precise alignment of virtual 3D images with the patient’s body. Accurate registration is crucial for translation of the preoperative AR surgical plan onto the surgical field. Many research groups currently investigate different registration methods – manual registration using fiducial markers; visual marker-guided registration; marker-free registration, with a variety of advanced algorithms86–88. Despite greatly improved accuracy throughout the years, there is still not an optimal and widely accepted solution. We believe that when this limitation is solved, the usage of AR will increase significantly.

Additionally, as for any novel technology – education and adequate guidance are an integral part of the implementation process and have financial and human resources implications. Nonetheless, young students and novices may be using such technology during their education and training, therefore having prior experience with the devices.

Future directions

With increasing evidence and clinical experience, we believe that 3D technologies will become an available tool utilized as part of the routinely preoperative phase. Based on the present knowledge, we propose two main phases for the integration process of 3D technologies in the preoperative phase. First, an implementation phase in which these technologies will be incorporated in routine, simple cases, serving as a proof-of-concept and ensuring safety. Then, after gaining the appropriate skills and clinical experience, 3D technologies should be utilized in more complex surgical cases, where they are shown to have a crucial role. Such prominent indications for 3D presurgical planning come mainly from orthopedic surgery in the treatment of complex fractures such as acetabular fractures24,30 and complex radius fractures23. As for the other disciplines – current knowledge is based on relatively small, preliminary clinical studies that will enable the performance of larger series and randomized controlled trials to show clinical superiority in the future. The distinction of complex cases should be guided by setting appropriate selection criteria based on current evidence and experience, that will reflect the effectiveness of 3D technologies in different scenarios.

As all 3D technologies utilize the same patient-specific imaging data, combining them in the preoperative or intraoperative settings may be especially beneficial. Using VR for setting a surgical plan and then simulating the operation using the same plan on a 3D printed anatomical model using AR, will provide a synergistic effect. In the same manner, taking the plan that was established on the virtual model and overlaying it on the patient’s body in real time using its counterpart intraoperative AR may optimize the abilities of such technologies to produce a complete advanced and innovative surgical environment (Fig. 3).

Figure 3.

Synergistic applications of 3D technologies. AR, augmented reality; PSI, patient-specific instrument; VSP, virtual surgical planning.

Figures

*All figures were created using “Canva Pro“ graphic design software (https://www.canva.com/).

*All pictures (except the picture under ‘stereolithographic models’ at Fig. 1) are original pictures acquired by Levin Center of 3D Printing and Surgical Innovation, Tel Aviv Medical Center, Tel Aviv, Israel

*The picture under ‘stereolithographic models’ at Figure 1 is obtained from licensed collection in ‘Canva Pro’ graphic design software (https://www.canva.com/).

Ethical approval

Not applicable.

Sources of funding

None.

Author contribution

Y.P. and J.K.: perceptualized the idea and concept of the article and conducted the literature review. Y.P., J.K., A.B., and Y.R. were the main authors of the manuscript. All authors drafted and/or critically revised the manuscript.

Conflicts of interest disclosure

The authors declare that they have no conflict of interest.

Research registration unique identifying number (UIN)

None.

Guarantor

Amit Benady, MD PhD, Head of Research, Levin Center for Surgical Innovation and 3D Printing Orthopedic Resident, Division of Orthopedic Surgery, Tel Aviv Medical Center, Israel

Data statement

All data generated or analyzed during this study are included in this article [and/or] its supplementary material files. Further enquiries can be directed to the corresponding author.

Acknowledgments

The author Amit Benady wishes to thank the Kahn foundation for supporting him as part of the “Orion” program at Tel Aviv Medical Center.