Accuracy of 3D-planned patient specific instrumentation in high tibial open wedge valgisation osteotomy

Purpose

High tibial osteotomy (HTO) is an effective treatment option in early osteoarthritis. However, preoperative planning and surgical execution can be challenging. Computer assisted three-dimensional (3D) planning and patient-specific instruments (PSI) might be helpful tools in achieving successful outcomes. Goal of this study was to assess the accuracy of HTO using PSI.

Methods

All medial open wedge PSI-HTO between 2014 and 2016 were reviewed. Using pre- and postoperative radiographs, hip-knee-ankle angle (HKA) and posterior tibial slope (PTS) were determined two-dimensionally (2D) to calculate 2D accuracy. Using postoperative CT-data, 3D surface models of the tibias were reconstructed and superimposed with the planning to calculate 3D accuracy.

Results

Twenty-three patients could be included. A mean correction of HKA of 9.7° ± 2.6° was planned. Postoperative assessment of HKA correction showed a mean correction of 8.9° ± 3.2°, resulting in a 2D accuracy for HKA correction of 0.8° ± 1.5°. The postoperative PTS changed by 1.7° ± 2.2°. 3D accuracy showed average 3D rotational differences of − 0.1° ± 2.3° in coronal plane, − 0.2° ± 2.3° in transversal plane, and 1.3° ± 2.1° in sagittal plane, whereby 3D translational differences were calculated as 0.1 mm ± 1.3 mm in coronal plane, − 0.1 ± 0.6 mm in transversal plane, and − 0.1 ± 0.6 mm in sagittal plane.

Conclusion

The use of PSI in HTO results in accurate correction of mechanical leg axis. In contrast to the known problem of unintended PTS changes in conventional HTO, just slight changes of PTS could be observed using PSI. The use of PSI in HTO might be preferable to obtain desired correction of HKA and to maintain PTS.

How 3D patient-specific instruments improve accuracy of pelvic bone tumour resection in a cadaveric study

OBJECTIVES

To assess the accuracy of patient-specific instruments (PSIs) versus standard manual technique and the precision of computer-assisted planning and PSI-guided osteotomies in pelvic tumour resection.

METHODS

CT scans were obtained from five female cadaveric pelvises. Five osteotomies were designed using Mimics software: sacroiliac, biplanar supra-acetabular, two parallel iliopubic and ischial. For cases of the left hemipelvis, PSIs were designed to guide standard oscillating saw osteotomies and later manufactured using 3D printing. Osteotomies were performed using the standard manual technique in cases of the right hemipelvis. Post-resection CT scans were quantitatively analysed. Student's t-test and Mann-Whitney U test were used.

RESULTS

Compared with the manual technique, PSI-guided osteotomies improved accuracy by a mean 9.6 mm (p < 0.008) in the sacroiliac osteotomies, 6.2 mm (p < 0.008) and 5.8 mm (p < 0.032) in the biplanar supra-acetabular, 3 mm (p < 0.016) in the ischial and 2.2 mm (p < 0.032) and 2.6 mm (p < 0.008) in the parallel iliopubic osteotomies, with a mean linear deviation of 4.9 mm (p < 0.001) for all osteotomies. Of the manual osteotomies, 53% (n = 16) had a linear deviation > 5 mm and 27% (n = 8) were > 10 mm. In the PSI cases, deviations were 10% (n = 3) and 0 % (n = 0), respectively. For angular deviation from pre-operative plans, we observed a mean improvement of 7.06° (p < 0.001) in pitch and 2.94° (p < 0.001) in roll, comparing PSI and the standard manual technique.

CONCLUSION

In an experimental study, computer-assisted planning and PSIs improved accuracy in pelvic tumour resections, bringing osteotomy results closer to the parameters set in pre-operative planning, as compared with standard manual techniques.Cite this article: A. Sallent, M. Vicente, M. M. Reverté, A. Lopez, A. Rodríguez-Baeza, M. Pérez-Domínguez, R. Velez. How 3D patient-specific instruments improve accuracy of pelvic bone tumour resection in a cadaveric study. Bone Joint Res 2017;6:577-583. DOI: 10.1302/2046-3758.610.BJR-2017-0094.R1.

Automated multiple trajectory planning algorithm for the placement of stereo-electroencephalography (SEEG) electrodes in epilepsy treatment

Purpose

About one-third of individuals with focal epilepsy continue to have seizures despite optimal medical management. These patients are potentially curable with neurosurgery if the epileptogenic zone (EZ) can be identified and resected. Stereo-electroencephalography (SEEG) to record epileptic activity with intracranial depth electrodes may be required to identify the EZ. Each SEEG electrode trajectory, the path between the entry on the skull and the cerebral target, must be planned carefully to avoid trauma to blood vessels and conflicts between electrodes. In current clinical practice trajectories are determined manually, typically taking 2–3 h per patient (15 min per electrode). Manual planning (MP) aims to achieve an implantation plan with good coverage of the putative EZ, an optimal spatial resolution, and 3D distribution of electrodes. Computer-assisted planning tools can reduce planning time by quantifying trajectory suitability.

Methods

We present an automated multiple trajectory planning (MTP) algorithm to compute implantation plans. MTP uses dynamic programming to determine a set of plans. From this set a depth-first search algorithm finds a suitable plan. We compared our MTP algorithm to (a) MP and (b) an automated single trajectory planning (STP) algorithm on 18 patient plans containing 165 electrodes.

Results

MTP changed all 165 trajectories compared to MP. Changes resulted in lower risk (122), increased grey matter sampling (99), shorter length (92), and surgically preferred entry angles (113). MTP changed 42 % (69/165) trajectories compared to STP. Every plan had between 1 to 8 (median 3.5) trajectories changed to resolve electrode conflicts, resulting in surgically preferred plans.

Conclusion

MTP is computationally efficient, determining implantation plans containing 7–12 electrodes within 1 min, compared to 2–3 h for MP.

Deep learning for automated segmentation of the temporomandibular joint

OBJECTIVE

Quantitative analysis of the volume and shape of the temporomandibular joint (TMJ) using cone-beam computed tomography (CBCT) requires accurate segmentation of the mandibular condyles and the glenoid fossae. This study aimed to develop and validate an automated segmentation tool based on a deep learning algorithm for accurate 3D reconstruction of the TMJ.

MATERIALS AND METHODS

A three-step deep-learning approach based on a 3D U-net was developed to segment the condyles and glenoid fossae on CBCT datasets. Three 3D U-Nets were utilized for region of interest (ROI) determination, bone segmentation, and TMJ classification. The AI-based algorithm was trained and validated on 154 manually segmented CBCT images. Two independent observers and the AI algorithm segmented the TMJs of a test set of 8 CBCTs. The time required for the segmentation and accuracy metrics (intersection of union, DICE, etc.) was calculated to quantify the degree of similarity between the manual segmentations (ground truth) and the performances of the AI models.

RESULTS

The AI segmentation achieved an intersection over union (IoU) of 0.955 and 0.935 for the condyles and glenoid fossa, respectively. The IoU of the two independent observers for manual condyle segmentation were 0.895 and 0.928, respectively (p<0.05). The mean time required for the AI segmentation was 3.6 s (SD 0.9), whereas the two observers needed 378.9 s (SD 204.9) and 571.6 s (SD 257.4), respectively (p<0.001).

CONCLUSION

The AI-based automated segmentation tool segmented the mandibular condyles and glenoid fossae with high accuracy, speed, and consistency. Potential limited robustness and generalizability are risks that cannot be ruled out, as the algorithms were trained on scans from orthognathic surgery patients derived from just one type of CBCT scanner.

CLINICAL SIGNIFICANCE

The incorporation of the AI-based segmentation tool into diagnostic software could facilitate 3D qualitative and quantitative analysis of TMJs in a clinical setting, particularly for the diagnosis of TMJ disorders and longitudinal follow-up.

Osteochondroma of the mandibular condyle: Report of two surgical approaches

Osteochondromas are common tumors of the long bones, but are rare in the craniofacial region. We detailed two different management of osteochondroma of the mandibular condyle treated utilizing three-dimensional (3D) imaging and computer-assisted planning. Simultaneous open temporomandibular joint and orthognathic surgeries were done to treat both the pathology and secondary facial asymmetry. An osteochondroma that presented as a bony mass at the lateral aspect of the left mandibular condyle of a 24-year-old Chinese female was treated with simultaneous orthognathic surgery and conservative excision. No recurrence was detected 7 months postsurgery. An osteochondroma that presented as a generalized enlargement of the right mandibular condyle of a 25-year-old Chinese male was treated with simultaneous orthognathic surgery and condylectomy. There were no significant issues 3 years postsurgery. Simultaneous orthognathic and temporomandibular joint surgeries are a viable option for the management of osteochondroma of the mandibular condyle. The availability of 3D imaging enabled better presurgical examination of the lesion, which directed treatment toward condylectomy or conservative excision.

Improving accuracy of opening-wedge osteotomies of distal radius using a patient-specific ramp-guide technique

BACKGROUND

Opening-wedge osteotomies of the distal radius, performed with three-dimensional printed patient-specific instruments, are a promising technique for accurate correction of malunions. Nevertheless, reports of residual malalignments and discrepancies in the plate and screw position from the planned fixation exist. Consequently, we developed a patient-specific ramp-guide technique, combining navigation of plate positioning, osteotomy cutting, and reduction. The aim of this study is to compare the accuracy of navigation of three-dimensional planned opening-wedge osteotomies, using a ramp-guide, over state-of-the-art guide techniques relying solely on pre-drilled holes.

METHODS

A retrospective analysis was carried out on opening-wedge osteotomies of the distal radius, performed between May 2016 and April 2017, with patient-specific instruments. Eight patients were identified in which a ramp-guide for the distal plate fixation was used. We compared the reduction accuracy with a control group of seven patients, where the reduction was performed with pre-drilled screw holes placed with the patient-specific instruments. The navigation accuracy was assessed by comparing the preoperative plans with the postoperative segmented, computed tomography scans. The accuracy was expressed using a 3D angle and in measurements of all six degrees of freedom (3 translations, 3 rotations), with respect to an anatomical coordinate system.

RESULTS

The duration of the surgery of the ramp-guide group was significantly shorter compared to the control group. Significantly less rotational and translational residual malalignment error was observed in the open-wedged osteotomies, where patient-specific instruments with ramp-guides were used. On average, a residual rotational malalignment error of 2.0° (± 2.2°) and a translational malalignment error of 0.6 mm (± 0.2 mm) was observed in the ramp-guide group, as compared to the 4.2° (± 15.0°) and 1.0 mm (± 0.4 mm) error in the control group. The used plate was not significantly positioned more accurately, but significantly fewer screws (15.6%) were misaligned in the distal fragment compared to the control group (51.9%).

CONCLUSION

The use of the presented ramp-guide technique in opening-wedge osteotomies is improving reduction accuracy, screw position, and surgical duration, compared to the existing patient-specific instrument based navigation methods.

Computer-Assisted Planning for Stereoelectroencephalography (SEEG)

Stereoelectroencephalography (SEEG) is a diagnostic procedure in which multiple electrodes are stereotactically implanted within predefined areas of the brain to identify the seizure onset zone, which needs to be removed to achieve remission of focal epilepsy. Computer-assisted planning (CAP) has been shown to improve trajectory safety metrics and generate clinically feasible trajectories in a fraction of the time needed for manual planning. We report a prospective validation study of the use of EpiNav (UCL, London, UK) as a clinical decision support software for SEEG. Thirteen consecutive patients (125 electrodes) undergoing SEEG were prospectively recruited. EpiNav was used to generate 3D models of critical structures (including vasculature) and other important regions of interest. Manual planning utilizing the same 3D models was performed in advance of CAP. CAP was subsequently employed to automatically generate a plan for each patient. The treating neurosurgeon was able to modify CAP generated plans based on their preference. The plan with the lowest risk score metric was stereotactically implanted. In all cases (13/13), the final CAP generated plan returned a lower mean risk score and was stereotactically implanted. No complication or adverse event occurred. CAP trajectories were generated in 30% of the time with significantly lower risk scores compared to manually generated. EpiNav has successfully been integrated as a clinical decision support software (CDSS) into the clinical pathway for SEEG implantations at our institution. To our knowledge, this is the first prospective study of a complex CDSS in stereotactic neurosurgery and provides the highest level of evidence to date.

Computer-assisted surgical planning of complex bone tumor resections improves negative margin outcomes in a sawbones model

PURPOSE

Several technologies have been implemented in orthopedic surgery to improve surgical outcomes, usually focusing on more accurate execution of a surgical plan, but the development of the plan itself is also of great importance. The purpose of this study is to examine whether the use of preoperative computer planning platforms can improve the surgical plan?

METHODS

Eight surgeons created a preoperative surgical plan to resect a distal femur parosteal osteosarcoma in two settings: (1) Using a 2-D and 3-D CT scan only (current standard); and (2) using a computer-assisted planning platform. The plans were thereafter virtually executed using a novel surgical navigation system and a Sawbones model. This simulated model was derived from, and identical to, an actual patient scenario. The outcomes of interest were the number of positive margin cuts, and the volume of the resected specimen.

RESULTS

Using the surgical plan developed with computer assistance, there were 4 positive margin cuts made by 2 surgeons. In comparison, using standard planning, there were 14 positive margin cuts made by all 8 surgeons (p = 0.02). The resection volume was larger in the computer-assisted plans (96 ± 10 mm³) than in the standard plans (88 ± 7 mm³) (p = 0.055).

CONCLUSIONS

Computer-assisted planning significantly decreased the risk of a positive margin resection in this Sawbones tumor model used to simulate resection of a primary bone sarcoma. This proof of concept study highlights the importance of advanced surgical planning and sets the ground for developing beneficial surgical planning systems.

Intra-oral scan segmentation using deep learning

OBJECTIVE

Intra-oral scans and gypsum cast scans (OS) are widely used in orthodontics, prosthetics, implantology, and orthognathic surgery to plan patient-specific treatments, which require teeth segmentations with high accuracy and resolution. Manual teeth segmentation, the gold standard up until now, is time-consuming, tedious, and observer-dependent. This study aims to develop an automated teeth segmentation and labeling system using deep learning.

MATERIAL AND METHODS

As a reference, 1750 OS were manually segmented and labeled. A deep-learning approach based on PointCNN and 3D U-net in combination with a rule-based heuristic algorithm and a combinatorial search algorithm was trained and validated on 1400 OS. Subsequently, the trained algorithm was applied to a test set consisting of 350 OS. The intersection over union (IoU), as a measure of accuracy, was calculated to quantify the degree of similarity between the annotated ground truth and the model predictions.

RESULTS

The model achieved accurate teeth segmentations with a mean IoU score of 0.915. The FDI labels of the teeth were predicted with a mean accuracy of 0.894. The optical inspection showed excellent position agreements between the automatically and manually segmented teeth components. Minor flaws were mostly seen at the edges.

CONCLUSION

The proposed method forms a promising foundation for time-effective and observer-independent teeth segmentation and labeling on intra-oral scans.

CLINICAL SIGNIFICANCE

Deep learning may assist clinicians in virtual treatment planning in orthodontics, prosthetics, implantology, and orthognathic surgery. The impact of using such models in clinical practice should be explored.

Computer-assisted planning for minimally invasive anterior two-thirds laser corpus callosotomy: A feasibility study with probabilistic tractography validation

•

Laser interstitial thermal therapy (LITT) is a novel minimally invasive technique for the treatment of epilepsy.

•

We test computer assisted planning with LITT to disrupt seizure spread.

•

Trajectory parameters and models were automatically generated from a single T1 image.

•

Probabilistic tractography revealed comparable interhemispheric disconnection to blinded expert surgeons.

Background

Anterior two-thirds corpus callosotomy is an effective palliative neurosurgical procedure for drug-refractory epilepsy that is most commonly used to treat drop-attacks. Laser interstitial thermal therapy is a novel stereotactic ablative technique that has been utilised as a minimally invasive alternative to resective and disconnective open neurosurgery. Case series have reported success in performing laser anterior two-thirds corpus callosotomy. Computer-assisted planning algorithms may help to automate and optimise multi-trajectory planning for this procedure.

Objective

To undertake a simulation-based feasibility study of computer-assisted corpus callostomy planning in comparison with expert manual plans in the same patients.

Methods

Ten patients were selected from a prospectively maintained database. Patients had previously undergone diffusion-weighted imaging and digital subtraction angiography as part of routine SEEG care. Computer-assisted planning was performed using the EpiNav™ platform and compared to manually planned trajectories from two independent blinded experts. Estimated ablation cavities were used in conjunction with probabilistic tractography to simulate the expected extent of interhemispheric disconnection.

Results

Computer-assisted planning resulted in significantly improved trajectory safety metrics (risk score and minimum distance to vasculature) compared to blinded external expert manual plans. Probabilistic tractography revealed residual interhemispheric connectivity in 1/10 cases following computer-assisted planning compared to 4/10 and 2/10 cases with manual planning.

Conclusion

Computer-assisted planning successfully generates multi-trajectory plans capable of LITT anterior two-thirds corpus callosotomy. Computer-assisted planning may provide a means of standardising trajectory planning and serves as a potential new tool for optimising trajectories. A prospective validation study is now required to determine if this translates into improved patient outcomes.

The Effect of Vascular Segmentation Methods on Stereotactic Trajectory Planning for Drug-Resistant Focal Epilepsy: A Retrospective Cohort Study

Background

Stereotactic neurosurgical procedures carry a risk of intracranial hemorrhage, which may result in significant morbidity and mortality. Vascular imaging is crucial for planning stereotactic procedures to prevent conflicts with intracranial vasculature. There is a wide range of vascular imaging methods used for stereoelectroencephalography (SEEG) trajectory planning. Computer-assisted planning (CAP) improves planning time and trajectory metrics. We aimed to quantify the effect of different vascular imaging protocols on CAP trajectories for SEEG.

Methods

Ten patients who had undergone SEEG (95 electrodes) following preoperative acquisition of gadolinium-enhanced magnetic resonance imaging (MR + Gad), magnetic resonance angiography and magnetic resonance angiography (MRV + MRA), and digital subtraction catheter angiography (DSA) were identified from a prospectively maintained database. SEEG implantations were planned using CAP using DSA segmentations as the gold standard. Strategies were then recreated using MRV + MRA and MR + Gad to define the “apparent” and “true” risk scores associated with each modality. Vessels of varying diameter were then iteratively removed from the DSA segmentation to identify the size at which all 3 vascular modalities returned the same safety metrics.

Results

CAP performed using DSA vessel segmentations resulted in significantly lower “true” risk scores and greater minimum distances from vasculature compared with the “true” risk associated with MR + Gad and MRV + MRA. MRV + MRA and MR + Gad returned similar risk scores to DSA when vessels <2 mm and <4 mm were not considered, respectively.

Conclusions

Significant variability in vascular imaging and trajectory planning practices exist for SEEG. CAP performed with MR + Gad or MRV + MRA alone returns “falsely” lower risk scores compared with DSA. It is unclear whether DSA is oversensitive and thus restricting potential trajectories.

Inter-rater variability of three-dimensional fracture reduction planning according to the educational background

Background

Computer-assisted three-dimensional (3D) planning is increasingly delegated to biomedical engineers. So far, the described fracture reduction approaches rely strongly on the performance of the users. The goal of our study was to analyze the influence of the two different professional backgrounds (technical and medical) and skill levels regarding the reliability of the proposed planning method. Finally, a new fragment displacement measurement method was introduced due to the lack of consistent methods in the literature.

Methods

3D bone models of 20 distal radius fractures were presented to nine raters with different educational backgrounds (medical and technical) and various levels of experience in 3D operation planning (0 to 10 years) and clinical experience (1.5 to 24 years). Each rater was asked to perform the fracture reduction on 3D planning software.

Results

No difference was demonstrated in reduction accuracy regarding rotational (p = 1.000) and translational (p = 0.263) misalignment of the fragments between biomedical engineers and senior orthopedic residents. However, a significantly more accurate planning was performed in these two groups compared with junior orthopedic residents with less clinical experience and no 3D planning experience (p < 0.05).

Conclusion

Experience in 3D operation planning and clinical experience are relevant factors to plan an intra-articular fragment reduction of the distal radius. However, no difference was observed regarding the educational background (medical vs. technical) between biomedical engineers and senior orthopedic residents. Therefore, our results support the further development of computer-assisted surgery planning by biomedical engineers. Additionally, the introduced fragment displacement measure proves to be a feasible and reliable method.

Level of Evidence

Diagnostic Level II

Enhancing surgical occlusion setting in orthognathic surgery planning using mixed reality technology: a comparative study

OBJECTIVES

Orthognathic surgery necessitates precise occlusal alignment during surgical planning, traditionally achieved through manual alignment of physical dental models as the recognized gold standard. This study aims to evaluate the efficacy of mixed reality technology in enhancing surgical occlusion setting compared to traditional physical alignment and an established virtual method, addressing the research question: Can mixed reality technology improve the accuracy and efficiency of occlusion setting in orthognathic surgery planning?

MATERIALS & METHODS

This experimental study compared the surgical occlusion settings of 30 orthognathic cases using three methods: a new virtual method with mixed reality technology, the traditional gold standard of physical alignment, and an established virtual occlusion method using the IPS Case Designer (KLS Martin SE & Co. KG, Tuttlingen, Germany).

RESULTS

Results indicated that surgical occlusions set with mixed reality technology were comparable to the conventional method in terms of maxillary movement and occlusal relationship. Differences observed were within the inter-observer variability of the gold standard. Both virtual methods tended to position the maxilla more anteriorly, resulting in fewer occlusal contacts. However, virtual occlusion demonstrated clinical applicability, achieving an average of 11 occlusal contacts with a bilaterally symmetrical distribution along the dental arch.

CONCLUSIONS

The mixed reality environment provides an intuitive and flexible experience for setting surgical occlusion, eliminating the need for costly 3D-printed physical models or the automatic calculations required by other virtual occlusion methods, thereby offering maximum freedom.

CLINICAL RELEVANCE

As a novel form of virtual occlusion, it presents a comprehensive tool that contributes to a timely and cost-effective full digital workflow of orthognathic surgery planning.

Automated condylar seating assessment using a deep learning-based three-step approach

OBJECTIVES

In orthognatic surgery, one of the primary determinants for reliable three-dimensional virtual surgery planning (3D VSP) and an accurate transfer of 3D VSP to the patient in the operation room is the condylar seating. Incorrectly seated condyles would primarily affect the accuracy of maxillary-first bimaxillary osteotomies as the maxillary repositioning is dependent on the positioning of the mandible in the cone-beam computed tomography (CBCT) scan. This study aimed to develop and validate a novel tool by utilizing a deep learning algorithm that automatically evaluates the condylar seating based on CBCT images as a proof of concept.

MATERIALS AND METHODS

As a reference, 60 CBCT scans (120 condyles) were labeled. The automatic assessment of condylar seating included three main parts: segmentation module, ray-casting, and feed-forward neural network (FFNN). The AI-based algorithm was trained and tested using fivefold cross validation. The method's performance was evaluated by comparing the labeled ground truth with the model predictions on the validation dataset.

RESULTS

The model achieved an accuracy of 0.80, positive predictive value of 0.61, negative predictive value of 0.9 and F1-score of 0.71. The sensitivity and specificity of the model was 0.86 and 0.78, respectively. The mean AUC over all folds was 0.87.

CONCLUSION

The innovative integration of multi-step segmentation, ray-casting and a FFNN demonstrated to be a viable approach for automating condylar seating assessment and have obtained encouraging results.

CLINICAL RELEVANCE

Automated condylar seating assessment using deep learning may improve orthognathic surgery, preventing errors and enhancing patient outcomes in maxillary-first bimaxillary osteotomies.

Static Zygomatic Guides: Digital ZAGA Concept

Guided zygomatic implant placement surgery has emerged as a promising solution for patients with severe maxillary bone loss, offering precise implant placement and predictable outcomes. This article provides a comprehensive review of the current state-of-the-art techniques, advantages, challenges, and future directions in guided zygomatic implant surgery.

Computed-tomography-based three-dimensional analysis of bilateral differences in phalanges

Three-dimensional analysis of bones, especially for preoperative planning of corrective osteotomy in fracture malunion, assumes that the bilateral extremities exhibit a symmetrical mirror image when projected onto each other. No studies are available for phalanges. Three-dimensional bone models of all phalanges of 20 healthy participants (40 hands) were created from computed tomography data. For each phalanx, the difference between the left and right sides were assessed with respect to axis of rotation, ulnoradial deviation, flexion-extension and bone length. The average absolute side difference was small, but with significant differences of extension-flexion (mean 1.1°), supination-pronation (mean 1.8°), ulnoradial deviation (mean 0.9°) and translation (mean 0.2 mm). All left proximal phalanges were significantly pronated in comparison to the right side. The differences are likely unimportant, especially in corrective osteotomy using advanced 3D techniques.

Novel CAD/CAM-splint-based navigation protocol enhances intraoperative maxillary position control in orthognathic surgery: a case control study

BACKGROUND

Virtual surgical planning for orthognathic surgery typically relies on two methods for intraoperative plan transfer: CAD/CAM occlusal splints and patient-specific implants (PSI). While CAD/CAM splints may offer limited accuracy, particularly in the vertical dimension, PSIs are constrained by higher costs and extended preparation times. Surgical navigation has emerged as a potential alternative, but existing protocols often involve invasive registration or lack transparent evaluation. This study introduces a novel protocol for point-based optical navigation using modified CAD/CAM splints for non-invasive registration and transparent intraoperative evaluation, assessing its effectiveness in maxillary positioning.

METHODS

This prospective case-control study included 20 patients undergoing bimaxillary orthognathic surgery. The experimental group employed surgical navigation with modified CAD/CAM splints, while the control group used standard CAD/CAM splints. Surgical accuracy was evaluated by measuring translational and rotational discrepancies between the planned and achieved maxillary positions. A mixed ANOVA was conducted to assess other factors, aside from surgical navigation, that might influence surgical accuracy.

RESULTS

Surgical navigation significantly improved accuracy in translational movements along the x-axis (right-left: -0.81 mm; p = 0.021) and z-axis (down-up: -0.82 mm; p = 0.014), as well as in yaw rotation (-0.45°; p = 0.045). Other movements also showed improved precision in the navigated group, though not statistically significant; y-axis (back-front): -0.60 mm (p = 0.094); pitch rotation: -0.70° (p = 0.071); roll rotation: -0.04° (p = 0.428). Besides the use of surgical navigation, the amount of planned movement significantly impacted surgical accuracy, although no specific factors could be identified to predict which cases would particularly benefit from surgical navigation.

CONCLUSIONS

Surgical navigation with modified CAD/CAM splints enhances surgical accuracy without requiring invasive procedures, offering a straightforward and transparent protocol suitable for routine clinical practice that allows intraoperative evaluation of maxillary positioning. However, the clinical significance and cost-effectiveness compared to PSI need further investigation. These findings suggest new directions for future developments, especially with advancements in mixed reality technologies, which could broaden the application of surgical navigation.

TRIAL REGISTRATION

Retrospectively registered with the German Clinical Trials Register (DRKS00034795).

Refining computer-assisted SEEG planning with spatial priors - A novel comparison of implantation strategies across adult and paediatric centres

OBJECTIVES

Computer-assisted planning (CAP) allows faster SEEG planning and improves grey matter sampling, orthogonal drilling angles to the skull, reduces risk scores and minimises intracerebral electrode length. Incorporating prior SEEG trajectories enhances CAP planning, refining output with centre-specific practices. This study significantly expands on the previous work, compares priors libraries between two centres, and describes differences between SEEG in adults and children in these centres.

METHODS

98 adults and 61 children who underwent SEEG implantation as part of epilepsy surgery investigations were included. Priors libraries were created for each population, clustered by target regions and subdivided by cortical approaches. The libraries were coregistered and quantitatively and qualitatively compared.

RESULTS

The average number of implanted electrodes per patient was higher in paediatric patients than adults (13.6 vs 8.0). Paediatric implantations focused more on the insula than adult implantations (38.0 % vs 13.5 %), with similar proportions of electrodes implanted in the temporal and parietal lobes, and a higher proportion of adult electrodes in the frontal and orbitofrontal regions (40.6 % vs 24.0 %). Correspondence between the priors libraries was high. We present an example of a complex insular implantation planned with paediatric spatial priors and illustrate resultant SEEG recordings.

DISCUSSION

The use of centre-specific spatial priors allows the incorporation of surgeon-specific and unit-specific preferences into automated planning. We compare implantation styles between a paediatric and an adult centre, discussing similarities and differences. This tool allows centres to compare practice and represents an effective way to analyse implantation strategies that is agnostic to method of implantation.