An average three-dimensional virtual human skull for a template-assisted maxillofacial surgery

In vitro comparison of guide planes for removable partial dentures prepared with CAD-CAM-assisted templates, guiding rod templates, and freehand

OBJECTIVES

This study aimed to evaluate the accuracy of computer-aided design and computer-aided manufacturing (CAD-CAM)-assisted templates (CCAT), guiding rod templates (GRT), and freehand (FH) preparation of guide planes.

METHODS

Forty-five identical maxillary resin casts were divided into three groups, in which the guide planes of the two abutment teeth were prepared using a CCAT (n=15), GRT (n=15), and FH (n=15). The CCAT and GRT were digitally designed on a digital cast of virtually prepared guide planes and fabricated using three-dimensional printing (3DP) technology. To assess the 3D trueness, the prepared guide planes were digitally scanned and compared to the virtually designed guide planes. The angle deviation was measured to assess the trueness of the direction of the guide plane preparation. Shapiro-Wilk and Levene's tests were used to check the normality and equivalence of the variance of the data. The data were compared by using the Kruskal‒Wallis H test (α=0.05).

RESULTS

The CCAT group exhibited significantly better 3D trueness (78.5±19.8 μm) than the GRT group (211.3±42.4 μm, p<0.05) and the FH group (198.9±44.3 μm, p<0.05). Additionally, the CCAT group (1.31±0.50°) showed significantly smaller direction trueness compared to the GRT (4.65±0.72°, p<0.05) and FH (5.64±0.70°, p<0.05) groups.

CONCLUSIONS

The novel CAD-CAM-assisted template significantly improved the quality of the guide planes compared with the GRT and FH procedures. This enhancement suggests that removable partial dentures can be predictably inserted immediately after guide plane preparation.

CLINICAL SIGNIFICANCE

CAD-CAM-assisted templates improve the quality of guide plane preparation.

Average Three-Dimensional Skeletofacial Model as a Template for Bone Repositioning during Virtual Orthognathic Surgery

BACKGROUND

Virtual planning has revolutionized orthognathic surgery. This study presents a computer-assisted method for constructing average three-dimensional skeletofacial models that can be applied as templates for surgical planning for maxillomandibular repositioning.

METHODS

The authors used the images of 60 individuals (30 women and 30 men) who had never undergone orthognathic surgery to construct an average three-dimensional skeletofacial model for male participants and one for female participants. The authors validated the accuracy of the newly developed skeletofacial models by comparing their images with 30 surgical simulation images (ie, skulls) that had been created using three-dimensional cephalometric normative data. The comparison was conducted by superimposing surgical simulation images created using the authors' models with the previously created images to analyze their differences, particularly differences in the jawbone position.

RESULTS

For all participants, the authors compared the jaw position in the surgical simulation images created using the authors' average three-dimensional skeletofacial models with that in the images created using three-dimensional cephalometric normative data. The results revealed that the planned maxillary and mandibular positions were similar in both images and that the differences between all facial landmarks were less than 1 mm, except for one dental position. Most studies have reported less than 2 mm to be the success criterion for the distance difference between planned and outcome images; thus, the authors' data indicate high consistency between the images in terms of jawbone position.

CONCLUSION

The authors' average three-dimensional skeletofacial models provide an innovative template-assisted orthognathic surgery planning modality that can enhance the fully digital workflow for virtual orthognathic surgical planning.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, V.

3D Virtual Modeling for Morphological Characterization of Pituitary Tumors: Preliminary Results on Its Predictive Role in Tumor Resection Rate

Among potential factors affecting the surgical resection in pituitary tumors, the role of tumor three-dimensional (3D) features is still unexplored. The aim of this study is to introduce the use of 3D virtual modeling for geometrical and morphological characterization of pituitary tumors and to evaluate its role as a predictor of total tumor removal. A total of 75 patients operated for a pituitary tumor have been retrospectively reviewed. Starting from patient imaging, a 3D tumor model was reconstructed, and 3D characterization based on tumor volume (Vol), area, sphericity (Spher), and convexity (Conv) was provided. The extent of tumor removal was then evaluated at post-operative imaging. Mean values were obtained for Vol (9117 ± 8423 mm3), area (2352 ± 1571 mm2), Spher (0.86 ± 0.08), and Conv (0.88 ± 0.08). Total tumor removal was achieved in 57 (75%) cases. The standard prognostic Knosp grade, Vol, and Conv were found to be independent factors, significantly predicting the extent of tumor removal. Total tumor resection correlated with lower Knosp grades (p = 0.032) and smaller Vol (p = 0.015). Conversely, tumors with a more irregular shape (low Conv) have an increased chance of incomplete tumor removal (p = 0.022). 3D geometrical and morphological features represent significant independent prognostic factors for pituitary tumor resection, and they should be considered in pre-operative planning to allow a more accurate decision-making process.

3D Patient-Specific Virtual Models for Presurgical Planning in Patients with Recto-Sigmoid Endometriosis Nodules: A Pilot Study

Background and Objective: In recent years, 3D printing has been used to support surgical planning or to guide intraoperative procedures in various surgical specialties. An improvement in surgical planning for recto-sigmoid endometriosis (RSE) excision might reduce the high complication rate related to this challenging surgery. The aim of this study was to build novel presurgical 3D models of RSE nodules from magnetic resonance imaging (MRI) and compare them with intraoperative findings. Materials and Methods: A single-center, observational, prospective, cohort, pilot study was performed by enrolling consecutive symptomatic women scheduled for minimally invasive surgery for RSE between November 2019 and June 2020 at our institution. Preoperative MRI were used for building 3D models of RSE nodules and surrounding pelvic organs. 3D models were examined during multi-disciplinary preoperative planning, focusing especially on three domains: degree of bowel stenosis, nodule's circumferential extension, and bowel angulation induced by the RSE nodule. After surgery, the surgeon was asked to subjectively evaluate the correlation of the 3D model with the intra-operative findings and to express his evaluation as "no correlation", "low correlation", or "high correlation" referring to the three described domains. Results: seven women were enrolled and 3D anatomical virtual models of RSE nodules and surrounding pelvic organs were generated. In all cases, surgeons reported a subjective "high correlation" with the surgical findings. Conclusion: Presurgical 3D models could be a feasible and useful tool to support surgical planning in women with recto-sigmoidal endometriotic involvement, appearing closely related to intraoperative findings.

Role of Navigation in Oral and Maxillofacial Surgery: A Surgeon's Perspectives

Surgeries related to the maxillofacial area deal with an intricate network of anatomical structures. With the complexity of the vital structures, it necessitates a surgical team to respect each anatomical boundary. In the past, there was an exceptionally high number of cases with surgical errors. These errors were not because of flaws in the surgeon’s skills or techniques but owing to lack of resources. Visualisation is one of the key factors that determines the precision of any surgical outcome. Advances in surgical planning have led to the introduction of a “Navigation” system that helps surgeons to see more, know more and ultimately do more for their patients. The usefulness of the navigation system in oral surgeries has been indicated by its surgical applications in craniomaxillofacial trauma, orthognathic surgeries, head and neck pathological resections, complex skull base surgeries and surgery involving temporomandibular joint. A vast majority of research literature has suggested remarkable improvement in surgical outcomes under the guidance of 3d planning and navigation. However, with such an inordinate advancement, financial expenses and a gradual learning curve are always a constraining factor in surgical navigation. This article overviews indication of navigation in craniofacial surgeries with a focus on applied aspect, planning and solution to the future problem.

The Wearable VOSTARS System for Augmented Reality-Guided Surgery: Preclinical Phantom Evaluation for High-Precision Maxillofacial Tasks

BACKGROUND

In the context of guided surgery, augmented reality (AR) represents a groundbreaking improvement. The Video and Optical See-Through Augmented Reality Surgical System (VOSTARS) is a new AR wearable head-mounted display (HMD), recently developed as an advanced navigation tool for maxillofacial and plastic surgery and other non-endoscopic surgeries. In this study, we report results of phantom tests with VOSTARS aimed to evaluate its feasibility and accuracy in performing maxillofacial surgical tasks.

METHODS

An early prototype of VOSTARS was used. Le Fort 1 osteotomy was selected as the experimental task to be performed under VOSTARS guidance. A dedicated set-up was prepared, including the design of a maxillofacial phantom, an ad hoc tracker anchored to the occlusal splint, and cutting templates for accuracy assessment. Both qualitative and quantitative assessments were carried out.

RESULTS

VOSTARS, used in combination with the designed maxilla tracker, showed excellent tracking robustness under operating room lighting. Accuracy tests showed that 100% of Le Fort 1 trajectories were traced with an accuracy of ±1.0 mm, and on average, 88% of the trajectory's length was within ±0.5 mm accuracy.

CONCLUSIONS

Our preliminary results suggest that the VOSTARS system can be a feasible and accurate solution for guiding maxillofacial surgical tasks, paving the way to its validation in clinical trials and for a wide spectrum of maxillofacial applications.