Assessing the accuracy of computer-planned osteotomy guided by stereolithographic template: A methodological framework applied to the mandibular bone harvesting

[Individualized surgical treatment of sarcomas of the extremities]

Sarcomas of the extremities are rare entities, the treatment of which requires special expertise. Even if the treatment of patients is always interdisciplinary, the surgical R0 resection is the key point of each curatively intended treatment. In addition to resection in sano, the aim is to preserve the extremities and function, so that defect reconstruction after resection plays a decisive role. Due to the heterogeneity of tumors as well as their localization and extent, reconstruction is always an individually adapted treatment. Modular tumor endoprostheses are often used in this context, which can be constructed according to the size of the defect. The transplantation of autologous or allogeneic bone is also frequently used alone or as an additive procedure. Patient-specific (mega)prostheses are used particularly for pelvic tumors. Defect reconstruction using scaffold-based procedures from the field of tissue engineering is being tested as a promising procedure for the future. This article provides an overview of the treatment principles for sarcomas of the extremities and their individual reconstruction options.

Clinical feasibility evaluation of a digital workflow of prosthetically oriented onlay bone grafting for horizontal alveolar augmentation: a prospective pilot study

BACKGROUND

Onlay bone grafting is considered highly reliable for reconstructing severe horizontal bone defects. A critical problem is how to achieve precise position of the bone block to control alveolar ridge dimensions. This research aims to establish a digital workflow for prosthetically oriented onlay bone grafting and evaluate its accuracy and efficiency.

METHODS

This prospective pilot study investigated eight patients who required implant restoration in the esthetic area with horizontal alveolar bone defects. The workflow includes preoperative virtual planning, design and manufacture of patient-specific templates, bone grafting surgery, and implant insertion. Primary outcomes were graft accuracy, defined by root mean square estimate (RMSE) values between preoperatively designed and actual implanted outer contours of bone blocks. Secondary outcomes were bone graft and implant success rates. Besides, the surgeons used the visual analog scale (VAS) to rate the intuitiveness, ease of understanding, and helpfulness of the workflow.

RESULTS

No bone grafts or implants failed in any of the eight patients, resulting in a 100% success rate. The RMSE values between the preoperative design and the implanted outer contour of bone blocks were 0.41 ± 0.15 mm. The digital approach showed advantages in intuitiveness (9.3 ± 0.5), understanding (9.0 ± 0.5), and helpfulness (8.4 ± 1.1) according to surgeons' VAS scores.

CONCLUSIONS

A digital workflow provided encouraging results, in terms of accuracy and efficacy, for horizontal bone augmentation.

TRIAL REGISTRATION

This study was registered in the National Clinical Trials Registry in 16/02/2023 under the identification number ChiCTR2300068361.

Impact of Mandibular Angle Osteotomy Using a Geometric Mathematical Design on the Aesthetic Osteotomy Line: A Retrospective Observational Study

BACKGROUND

Mandibular angle osteotomy (MAO) is a frequently described technique in Eastern females. The success hinges on the precise positioning of the osteotomy line. The geometric mathematical method is viable. Therefore, we explored the impact of mandibular angle osteotomy using aesthetic standards and printed digital osteotomy templates (DOTs) on the aesthetic osteotomy line.

METHODS

This retrospective observational study included female patients with prominent mandibular angle (PMA) who underwent MAO at our hospital between January 2020 and March 2021. Thirty-three female patients were included, 22 in the DOTs group using new DOTs, and 11 in the traditional group using traditional free-hand techniques.

RESULTS

Regarding the width of the excised bone, the postoperative deviation from the preoperative plan was not significant in the DOTs group (0.5 ± 0.3 mm, P > 0.05), while the deviation was significant for the traditional group (2.5 ± 1.2 mm, P<0.05). The preparation time was longer in the DOTs group than in the traditional group (82 ± 11 vs. 53±4 min, P < 0.001). The osteotomy time and the operation time were shorter in the DOTs group than in the traditional group (osteotomy: 54 ± 5 vs. 73 ± 6 min; preparation: 124 ± 10 vs. 169 ± 13 min; both P < 0.001). The Likert (4.0 ± 0.5 vs. 1.0 ± 0.6, P = 0.006) and FACE-Q scores (17.5 ± 1.7 vs. 15.6 ± 1.3, P = 0.029) were higher in the DOTs group.

CONCLUSIONS

The new method of positioning the new aesthetic osteotomy line based on geometric analysis might provide a possible osteotomy method that strongly suggests effectiveness, safety, individualization, and accuracy, with a shorter operation and higher patient satisfaction.

LEVEL OF EVIDENCE IV

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Computer-Guided Osteotomy with Simultaneous Implant Placement and Immediately Loaded Full-Arch Fixed Restoration: A Case Report

Aim: This case report aims to illustrate a clinical protocol that allows for the rehabilitation of patients requiring extensive osteotomy, simultaneous implant placement, and full-arch, screwed-in prosthetics in one session. This protocol allows for the improvement of the aesthetics and functionality of the fixed implant-supported prosthesis through the preoperative planning of all surgical procedures, including osteotomy, and of the prosthesis through the application of 3D-printing technology for the creation of surgical templates and prostheses. Methods: This case report concerns a 72-year-old patient, ASA1, who, following diagnosis, the establishment of a treatment plan, and the provision of informed consent, opted for an immediate, full-arch rehabilitation of the lower arch. The digital planning stage started with the correct positioning of the fixtures. The proper bone levels were found and used to guide the creation of the provisional screwed-in prothesis. Two templates with the same supports (landmarks/pins) were then 3D-printed: a positioning template, including a slit to assist the surgeon during the osteotomy, and a surgery template to assist the surgeon during the implants’ positioning. A screwed-in prosthesis encased in resin C&B MFH (NEXTDENT®, Soesterberg, The Netherlands) was delivered. Minimal occlusal adjustments were performed. Results: In a single clinical session, through careful planning and the pre-operative 3D printing of a prosthesis, a temporary implant-supported prosthetic rehabilitation was possible in a case that required an extended osteotomy. Clinically, the correspondence between the virtual design phase and the final realization was consistent. At a functional level, the provisional prosthesis required minimal occlusal adjustments and the DVO values obtained in the immediate post-operative period were found to be comparable to those of the virtual design. By planning the final position of the bone and the implants in advance, it was possible to deliver a full-arch prothesis with proper implant emergence, occlusal vertical dimensions, and occlusal relationship. Conclusion: This fully digital protocol allows the clinician to preview and plan the osteotomy and implant surgery as well as the delivery of the temporary, immediately loaded, complete, fixed prosthesis in patients who are candidates for post-extraction surgery with the need for severe osteotomy.

Accuracy and Technical Predictability of Computer Guided Bone Harvesting from the Mandible: A Cone-Beam CT Analysis in 22 Consecutive Patients

This study assesses the accuracy and technical predictability of a computer-guided procedure for harvesting bone from the external oblique ridge using a patient-specific cutting guide. Twenty-two patients needing bone augmentation for implant placement were subjected to mandibular osteotomy employing a case-specific stereolithographic surgical guide generated through computer aided design. Differences between planned and real cut planes were measured comparing pre- and post-operative Cone Beam Computed Tomography images of the donor site according to six validated angular and displacement indexes. Accuracy and technical predictability were assessed for 119 osteotomy planes over the study population. Three different guide fitting approaches were compared. An average root-mean-square discrepancy of 0.52 (0.30-0.97) mm was detected. The accuracy of apical and medial planes was higher than the mesial and distal planes due to occasional antero-posterior guide shift. Fitting the guide with an extra reference point on the closest tooth performed better than using only the bone surface, with two indexes significantly lower and less disperse. The study showed that the surgical plan was actualized with a 1 mm safety margin, allowing effective nerve preservation and reducing technical variability. When possible, surgical guide design should allow fitting on the closest tooth based on both radiological and/or intra-oral scan data.

Fully digital versus conventional workflow for horizontal ridge augmentation with intraoral block bone: A randomized controlled clinical trial

OBJECTIVES

To compare the outcome and efficiency of the computer-aided intraoral block bone grafting procedure with those of the conventional technique for the augmentation of horizontal ridge defects.

MATERIALS AND METHODS

A total of 28 patients with single missing tooth in esthetic zone with class IV horizontal alveolar bone defect in need of dental implant restoration were recruited. Computer-aided design of the implant restoration and intraoral block bone grafting was performed for all the participants. The patients were randomly and equally divided into guide and control groups. A fully guided bone harvesting, trimming, and grafting surgery was executed in the guide group. The control group patients underwent surgery without any guide. After 6 months, all the patients underwent implant placement. The primary outcomes were the root mean square estimate (RMSE) values between the outer contours of the actual implanted and planned bone block as well as the RMSE values between the inner surface of the implanted bone block and the original bone surface of the recipient site immediately after surgery. The secondary outcomes were the trimming time of bone block and the surgery-associated complications. The postoperative visual analog scale (VAS) of pain, swelling, and mouth opening difficulty was recorded.

RESULTS

All 28 patients underwent intraoral block bone grafting, followed by the placement of implant after 191.8 ± 19.69 days. The RMSE values between the outer contours of the implanted and planned bone blocks were significantly lower in the guide group (0.37 ± 0.16 mm) as compared to those in the control group (0.72 ± 0.29 mm) (p = 0.0007). The RMSE values between the inner contours of the graft block and original bone at the recipient site were lower in the guide group (0.35 ± 0.15 mm) as compared to those in the control group (0.48 ± 0.17 mm) (p = 0.043). The duration of bone block trimming was shorter in the guide group (401.51 ± 97.60 s) as compared to the control group (602.36 ± 160.57 s) (p = 0.0005). In the control group, two patients received secondary bone grafting, one patient experienced bleeding of donor site and temporary hypoesthesia of the lower lip and chin skin, and one patient developed temporary sensitivity of the adjacent tooth.

CONCLUSIONS

As compared to the conventional procedure, the fully digital workflow in the present study seemed to be a more accuracy and effective protocol for horizontal ridge augmentation with intraoral block bone.

TRIAL REGISTRATION

Chictr.org.cn (ChiCTR2000036390).

Horizontal ridge augmentation in the anterior maxilla with in situ onlay bone grafting: a retrospective cohort study

OBJECTIVES

This study aimed to introduce a digitally guided in situ autogenous onlay grafting technique and compare its effectiveness with the conventional (ex situ) onlay technique in augmenting horizontal bone defects of the anterior maxilla.

MATERIALS AND METHODS

This retrospective cohort study included 24 patients who had received autogenous onlay bone grafts combined with guided bone regeneration (GBR) in the anterior maxilla. Fourteen patients were recruited into the in situ onlay grafting group (EG), and 10 were recruited into the ex situ onlay group (CG), defined by the donor sites. The clinical parameters, radiographic changes, micro-CT, and histological processes were evaluated after a mean follow-up period of 1.7 years.

RESULTS

The horizontal bone width reflected significant bone modeling over time (p < 0.001) in the first 6 months. Multivariable analysis showed that the treatment modality (grouping) was a critical factor positively associated with vertical bone height alteration. However, neither the alteration rate of horizontal bone width nor the bone volume was associated with the treatment modality. The number of periosteal screws per graft positively affected horizontal contour maintenance (p < 0.05). No significant differences were observed between the groups in the clinical parameters (complications, success rate, and peri-implant parameters). The micro-CT and histological outcomes were similar between the groups.

CONCLUSION

Despite the limitations of this study, in situ onlay grafting combined with GBR was an effective and reliable approach for horizontal bone augmentation in the anterior maxilla and appeared to demonstrate better stability in vertical bone remodeling.

CLINICAL RELEVANCE

This study introduces a modified and minimally invasive technique of onlay grafting for horizontal bone augmentation. This in situ onlay grafting demonstrates superior stability in vertical bone remodeling. The trial registration number is ChiCTR2100054683.

Application of Segmented Template in Three-Dimensionally Guided Mandibular Angle Osteotomy

BACKGROUND

The procedure of mandibular angle osteotomy (MAO) via an intraoral approach is challenging and experience-dependent due to the limited field of view and inadequate operational space. Uncertainty about the osteotomy line and plane can lead to severe complications. A three-dimensional printed guidance template based on a computer-assisted preoperative simulation is a potential solution to this problem. The current study aims to retrospectively investigate the feasibility and accuracy of using a custom-made segmented template to guide the osteotomy plane during the procedure.

METHODS

Sixty patients who had segmented template-guided MAO were included in the study. Preoperative simulation using the custom-designed template and postoperative computed tomography were collected and parameters, including mandibular angle, gonion distance, and the mandibular plane angle were measured. A paired t tests and intraclass correlation coefficients (ICCs) were used to evaluate the efficacy, accuracy, and symmetry of the results. All complications were reviewed.

RESULTS

The patients had a significantly larger mandibular angle and narrower gonion distance postoperatively. Preoperative simulations and postoperative outcomes were compared; ICCs were larger than 95% indicating significant agreement. Bilateral postoperative comparisons of the mandible also demonstrated excellent agreement (ICC > 95%). Numbness in the chin area was the most frequent complication but all recovered by 3 months postoperatively.

CONCLUSIONS

The custom-made template can guide the osteotomy plane during the MAO procedure and achieve favorable accuracy and symmetry. Direct contact of the saw with the guidance template not only facilitates control of the osteotomy line but also the oblique angle of the osteotomy plane. This methodology may be a feasible and effective tool for mandibular contouring.

Automatic mandible segmentation from CT image using 3D fully convolutional neural network based on DenseASPP and attention gates

PURPOSE

In cranio-maxillofacial surgery, it is of great clinical significance to segment mandible accurately and automatically from CT images. However, the connected region and blurred boundary in teeth and condyles make the process challenging. At present, the mandible is commonly segmented by experienced doctors using manually or semi-automatic methods, which is time-consuming and has poor segmentation consistency. In addition, existing automatic segmentation methods still have problems such as region misjudgment, low accuracy, and time-consuming.

METHODS

For these issues, an automatic mandibular segmentation method using 3d fully convolutional neural network based on densely connected atrous spatial pyramid pooling (DenseASPP) and attention gates (AG) was proposed in this paper. Firstly, the DenseASPP module was added to the network for extracting dense features at multiple scales. Thereafter, the AG module was applied in each skip connection to diminish irrelevant background information and make the network focus on segmentation regions. Finally, a loss function combining dice coefficient and focal loss was used to solve the imbalance among sample categories.

RESULTS

Test results showed that the proposed network obtained a relatively good segmentation result, with a Dice score of 97.588 ± 0.425%, Intersection over Union of 95.293 ± 0.812%, sensitivity of 96.252 ± 1.106%, average surface distance of 0.065 ± 0.020 mm and 95% Hausdorff distance of 0.491 ± 0.021 mm in segmentation accuracy. The comparison with other segmentation networks showed that our network not only had a relatively high segmentation accuracy but also effectively reduced the network's misjudgment. Meantime, the surface distance error also showed that our segmentation results were relatively close to the ground truth.

CONCLUSION

The proposed network has better segmentation performance and realizes accurate and automatic segmentation of the mandible. Furthermore, its segmentation time is 50.43 s for one CT scan, which greatly improves the doctor's work efficiency. It will have practical significance in cranio-maxillofacial surgery in the future.