Reliability and validity of handheld structured light scanners and a static stereophotogrammetry system in facial three-dimensional surface imaging.

Several new systems for three-dimensional (3D) surface imaging of the face have become available to assess changes following orthognathic or facial surgery. Before they can be implemented in practice, their reliability and validity must be established. Our aim, therefore, was to study the intra- and inter-system reliability and validity of 3dMD (stereophotogrammetry), Artec Eva and Artec Space Spider (both structured light scanners). Intra- and inter-system reliability, expressed in root mean square distance, was determined by scanning a mannequin's head and the faces of healthy volunteers multiple times. Validity was determined by comparing the linear measurements of the scans with the known distances of a 3D printed model. Post-processing errors were also calculated. Intra-system reliability after scanning the mannequin's head was best with the Artec Space Spider (0.04 mm Spider; 0.07 mm 3dMD; 0.08 mm Eva). The least difference in inter-system reliability after scanning the mannequin's head was between the Artec Space Spider and Artec Eva. The best intra-system reliability after scanning human subjects was with the Artec Space Spider (0.15 mm Spider; 0.20 mm Eva; 0.23 mm 3dMD). The least difference in inter-system reliability after scanning human subjects was between the Artec Eva and Artec Space Spider. The most accurate linear measurement validity occurred with the Artec Space Spider. The post-processing error was 0.01 mm for all the systems. The Artec Space Spider is the most reliable and valid scanning system.

Guided placement of zygomatic implants in head and neck cancer patients: implant survival and patient outcomes at 1-3 years of follow-up.

Zygomatic implants (ZI) are a valuable option for supporting an obturator prosthesis after maxillary resection. This study was performed to assess the clinical outcomes of a digitally validated guided technique for ZI placement, followed by immediate prosthetic obturation. The primary objective was to evaluate implant survival, while the secondary objective was to assess patient-reported quality of life post-rehabilitation. Twelve patients treated for head and neck cancer received a total of 36 ZI after ablative surgery. The mean duration of ZI follow-up was 30.1 months. The survival rate of ZI placed in non-irradiated patients was 100%, while it was 85% in irradiated patients. Patient-reported outcomes were evaluated using the Liverpool Oral Rehabilitation Questionnaire (LORQv3) and the University of Washington Quality of Life Questionnaire (UW-QOL v4). Most patients reported satisfactory outcomes in the oral function domain of the LORQv3 (mean score 17.7 ± 4.5; possible range 12-48, with lower scores indicating better outcomes). Regarding the UW-QOL v4, the swallowing and chewing domains had the highest scores (mean 97.5 ± 8.7 and 95.8 ± 14.4, respectively; maximum possible score of 100). In conclusion, this treatment approach improves function and quality of life after maxillary ablative surgery. However, irradiated patients showed a noticeable trend of higher implant failure, and this was influenced by tumour position and size impacting the radiation dose to the zygomatic bone.

Postoperative skeletal stability at the one-year follow-up after splintless Le Fort I osteotomy using patient-specific osteosynthesis versus conventional osteosynthesis: a randomized controlled trial.

The purpose of this study was to assess the 1-year skeletal stability of the osteotomized maxilla after Le Fort I surgery, comparing conventional osteosynthesis with patient-specific osteosynthesis. Patients were assigned to a conventional or patient-specific osteosynthesis group using prospective randomization. The primary outcome was the three-dimensional change in postoperative skeletal position of the maxilla between the 2-week and 1-year follow-up cone beam computed tomography scans. Fifty-eight patients completed the protocol for the 2-week postoperative analysis, and 27 patients completed the 1-year follow-up study protocol. Of the 27 patients completing the entire protocol, 13 were in the conventional group and 14 in the patient-specific osteosynthesis group. The three-dimensional translation analysis showed that the use of the patient-specific osteosynthesis resulted in a skeletally stable result, comparable to that of conventional miniplate fixation. For both the patient-specific osteosynthesis and conventional miniplate fixation groups, median translations of less than 1 mm and median rotations of less than 1° were observed, indicating that both methods of fixation resulted in a stable result for the 27 patients examined. For the Le Fort I osteotomy, the choice between patient-specific osteosynthesis and conventional osteosynthesis did not affect the postoperative skeletal stability after 1 year of follow-up.

The accuracy of gap and step-off measurements in acetabular fracture treatment.

The assessment of gaps and steps in acetabular fractures is challenging. Data from various imaging techniques to enable accurate quantification of acetabular fracture displacement are limited. The aim of this study was to assess the accuracy of pelvic radiographs, intraoperative fluoroscopy, and computed tomography (CT) in detecting gaps and step-offs in acetabular fractures. Sixty patients, surgically treated for acetabular fractures, were included. Five observers (5400 measurements) measured the gaps and step-offs on radiographs and CT scans. Intraoperative fluoroscopy images were reassessed for the presence of gaps and/or step-offs. Preoperatively, 25% of the gaps and 40% of the step-offs were undetected on radiographs compared to CT. Postoperatively, 52% of the gaps and 80% of the step-offs were missed on radiographs compared to CT. Radiograph analysis led to a significantly smaller gap and step-off compared to the CT measurements, an underestimation by a factor of two. Approximately 70% of the residual gaps and step-offs was not detected using intraoperative fluoroscopy. Gaps and step-offs that exceed the critical cut-off indicating worse prognosis often remained undetected on radiographs compared to CT scans. Less-experienced observers tend to overestimate gaps and step-offs compared to the more-experienced observers. In acetabular fracture treatment, gaps and step-offs were often undetected and underestimated on radiographs and intraoperative fluoroscopy in comparison with CT scans. This means that CT is superior to radiographs in detecting acetabular fracture displacement, which is clinically relevant for patient counselling regarding treatment decisions and prognosis.

Immediate implant-retained prosthetic obturation after maxillectomy based on zygomatic implant placement by 3D-guided surgery: a cadaver study.

BACKGROUND: The aim of this study was to introduce a complete 3D workflow for immediate implant retained prosthetic rehabilitation following maxillectomy in cancer surgery. The workflow consists of a 3D virtual surgical planning for tumor resection, zygomatic implant placement, and for an implant-retained prosthetic-obturator to fit the planned outcome situation for immediate loading. MATERIALS AND METHODS: In this study, 3D virtual surgical planning and resection of the maxilla, followed by guided placement of 10 zygomatic implants, using custom cutting and drill/placement-guides, was performed on 5 fresh frozen human cadavers. A preoperatively digitally designed and printed obturator prosthesis was placed and connected to the zygomatic implants. The accuracy of the implant positioning was obtained using 3D deviation analysis by merging the pre- and post-operative CT scan datasets. RESULTS: The preoperatively designed and manufactured obturator prostheses matched accurately the per-operative implant positions. All five obturators could be placed and fixated for immediate loading. The mean prosthetic point deviation on the cadavers was 1.03 ± 0.85 mm; the mean entry point deviation was 1.20 ± 0.62 mm; and the 3D angle deviation was 2.97 ± 1.44°. CONCLUSIONS: It is possible to 3D plan and accurately execute the ablative surgery, placement of zygomatic implants, and immediate placement of an implant-retained obturator prosthesis with 3D virtual surgical planning.The next step is to apply the workflow in the operating room in patients planned for maxillectomy.

Augmented Reality Visualization for Image-Guided Surgery: A Validation Study Using a Three-Dimensional Printed Phantom.

BACKGROUND: Oral and maxillofacial surgery currently relies on virtual surgery planning based on image data (CT, MRI). Three-dimensional (3D) visualizations are typically used to plan and predict the outcome of complex surgical procedures. To translate the virtual surgical plan to the operating room, it is either converted into physical 3D-printed guides or directly translated using real-time navigation systems. PURPOSE: This study aims to improve the translation of the virtual surgery plan to a surgical procedure, such as oncologic or trauma surgery, in terms of accuracy and speed. Here we report an augmented reality visualization technique for image-guided surgery. It describes how surgeons can visualize and interact with the virtual surgery plan and navigation data while in the operating room. The user friendliness and usability is objectified by a formal user study that compared our augmented reality assisted technique to the gold standard setup of a perioperative navigation system (Brainlab). Moreover, accuracy of typical navigation tasks as reaching landmarks and following trajectories is compared. RESULTS: Overall completion time of navigation tasks was 1.71 times faster using augmented reality (P = .034). Accuracy improved significantly using augmented reality (P < .001), for reaching physical landmarks a less strong correlation was found (P = .087). Although the participants were relatively unfamiliar with VR/AR (rated 2.25/5) and gesture-based interaction (rated 2/5), they reported that navigation tasks become easier to perform using augmented reality (difficulty Brainlab rated 3.25/5, HoloLens 2.4/5). CONCLUSION: The proposed workflow can be used in a wide range of image-guided surgery procedures as an addition to existing verified image guidance systems. Results of this user study imply that our technique enables typical navigation tasks to be performed faster and more accurately compared to the current gold standard. In addition, qualitative feedback on our augmented reality assisted technique was more positive compared to the standard setup.?>.

Accuracy of fit analysis of the patient-specific Groningen temporomandibular joint prosthesis.

Total joint replacement (TJR) with a prosthesis can be indicated for patients with severe temporomandibular joint (TMJ) dysfunction. Surgical accuracy is necessary for correct translation of the preoperatively predicted functional outcome, wear, and biomechanical behaviour of the patient-specific TMJ-TJR prosthesis. This study describes the first clinical applications of the patient-specific TMJ-TJR prosthesis according to the Groningen principles (G-TMJ-TJR), which was developed and validated in a prior human cadaver test study. The aim of this study was to validate the accuracy of placement of the patient-specific G-TMJ-TJR in the clinical setting. It was hypothesized that a virtual surgical plan (VSP) combined with guided placement of the patient-specific G-TMJ-TJR would be performed as predictably and accurately as in the prior cadaver series. All patients who received a VSP-based patient-specific G-TMJ-TJR between December 2017 and March 2020 were included in this study. The accuracy analysis was based on postoperative cone beam computed tomography (CBCT) data. All 11 prostheses could be inserted using routine pre-auricular and retromandibular surgical approaches. Analysis of the VSPs and postoperative CBCTs showed an average three-dimensional deviation of 1.07mm (standard deviation 0.46mm, range 0.33-1.91mm) for all of the fossa and mandibular components. The patient-specific G-TMJ-TJR can be applied predictably and accurately in a clinical setting.

The use of xenografts to prevent inferior border defects following bilateral sagittal split osteotomies: three-dimensional skeletal analysis using cone beam computed tomography.

The aim of this retrospective study was to investigate grafting in the osteotomy gap during bilateral sagittal split osteotomy (BSSO), using a xenograft and fibrin glue. Hard tissue defects in the inferior mandibular border were assessed using cone beam computed tomography scans taken 1 week and 1year postoperatively. The study group of 20 patients underwent bone grafting during BSSO (mean age 26.1years; mean horizontal displacement 8.5mm) and the control group of 20 patients did not (mean age 30.2 years; mean horizontal displacement 7.6mm). The mean height of the mandibular defects was significantly lower in the study group, but there was no significant difference in volume measurements between the groups. Grafting had a negligible effect on large displacements (9.0-15.0mm), which might have been due to an inadequate amount and/or positioning of the graft, or to poor dimensional stability. This may be resolved by improved graft positioning or by using a different kind of (xeno)graft.

Splintless surgery using patient-specific osteosynthesis in Le Fort I osteotomies: a randomized controlled multi-centre trial.

The accuracy of orthognathic surgery has improved with three-dimensional virtual planning. The translation of the planning to the surgical result is reported to vary by >2mm. The aim of this randomized controlled multi-centre trial was to determine whether the use of splintless patient-specific osteosynthesis can improve the accuracy of maxillary translation. Patients requiring a Le Fort I osteotomy were included in the trial. The intervention group was treated using patient-specific osteosynthesis and the control group with conventional osteosynthesis and splint-based positioning. Fifty-eight patients completed the study protocol, 27 in the patient-specific osteosynthesis group and 31 in the control group. The per protocol median anteroposterior deviation was found to be 1.05mm (interquartile range (IQR) 0.45-2.72mm) in the patient-specific osteosynthesis group and 1.74mm (IQR 1.02-3.02mm) in the control group. The cranial-caudal deviation was 0.87mm (IQR 0.49-1.44mm) and 0.98mm (IQR 0.28-2.10mm), respectively, whereas the left-right translation deviation was 0.46mm (IQR 0.19-0.96mm) in the patient-specific osteosynthesis group and 1.07mm (IQR 0.62-1.55mm) in the control group. The splintless patient-specific osteosynthesis method improves the accuracy of maxillary translations in orthognathic surgery and is clinically relevant for planned anteroposterior translations of more than 3.70mm.

Quantitative 3D measurements of tibial plateau fractures.

Fracture gap and step-off measurements on 2DCT-slices probably underestimate the complex multi-directional features of tibial plateau fractures. Our aim was to develop a quantitative 3D-CT (Q3DCT) fracture analysis of these injuries. CT-based 3D models were created for 10 patients with a tibial plateau fracture. Several 3D measures (gap area, articular surface involvement, 3D displacement) were developed and tested. Gaps and step-offs were measured in 2D and 3D. All measurements were repeated by six observers and the reproducibility was determined by intra-class correlation coefficients. Q3DCT measurements demonstrated a median gap of 5.3 mm, step-off of 5.2 mm, gap area of 235 mm2, articular surface involvement of 33% and 3D displacement of 6.1 mm. The inter-rater reliability was higher in the Q3DCT than in the 2DCT measurements for both the gap (0.96 vs. 0.81) and step-off (0.63 vs. 0.32). Q3DCT measurements showed excellent reliability (ICC of 0.94 for gap area, 1 for articular surface involvement and 0.99 for 3D displacement). Q3DCT fracture analysis of tibial plateau fractures is feasible and shows excellent reliability. 3D measurements could be used together with the current classification systems to quantify the true extent of these complex multi-directional fractures in a standardized way.

Introduction of a three-dimensional computed tomography measurement method for acetabular fractures.

INTRODUCTION: Acetabular fractures consist of complex fracture patterns whereby bone fragments are displaced in different directions. Two-dimensional computed tomography (2DCT) gap and step-off measurements tend to underestimate the multidirectional features of these fractures. The aim was to develop a three-dimensional computed tomography (3DCT) measurement method for acetabular fractures and validate whether this method will provide an observer independent fracture characterization. MATERIALS AND METHODS: Sixty patients, operated for an acetabular fracture between 2007 and 2018, were included. The displacement was measured on the pre- and postoperative CT scans. Pre- and postoperative CT-based 3D models were made for each patient. Multiple 3D measurements, namely the 3D step-off, gap and the total gap area were introduced to quantify the preoperative and postoperative displacement. The Wilcoxon signed rank analysis was used to compare the 2DCT and 3DCT measurements. RESULTS: The preoperative displacement was significantly underestimated by 2DCT measurements in comparison with 3DCT measurements (2D vs. 3D; step-off 8 vs. 16 mm with P < 0.001; gap 19 vs. 21 mm with P = 0.001). The same applies to the postoperative residual displacement (2D vs. 3D; step-off 0 vs. 6 mm; gap 3 vs. 8 mm; P < 0.001). The total gap area, defined as the surface area between all fracture lines in the 3D model, was measured for each patient, resulting in a median value of 722 mm2 preoperatively and 168 mm2 postoperatively, with excellent inter- and intra-rater reliability. CONCLUSION: 2DCT measurements tend to underestimate the initial and residual displacement in complex acetabular fractures. A 3DCT analysis of these injuries was developed to overcome this and should be used in addition to the Judet/Letournel and AO/OTA classification systems, in order to provide an observer independent quantifiable fracture description and accurate assessment of the fracture reduction.

Multi-modality 3D mandibular resection planning in head and neck cancer using CT and MRI data fusion: A clinical series.

OBJECTIVES: 3D virtual surgical planning (VSP) and guided surgery has been proven to be an effective tool for resection and reconstruction of the mandible. Currently, most widely used 3D VSP approaches to mandibular resection do not include detailed tumour information in the VSP. This manuscript presents a strategy where the aim was to incorporate tumour visualisation into the 3D virtual plan. Three-dimensional VSP of the mandibular resections was based on the fusion of CT and MRI data which was subsequently applied in clinical practice. METHODS: All patients diagnosed with oral squamous cell carcinoma between 2014 and 2017 at the University Medical Centre Groningen were included. The tumour was delineated on the MRI data, after which this dataset was fused with the CT bone data in order to construct a 3D bone and tumour model for virtual resection planning. Guided resections were performed and post-operative evaluation quantified the accuracy of the resection. The histopathological findings and patient and tumour characteristics were compared to those of a historical cohort (2009-2014) of conventional mandibular continuity resections. RESULTS: Twenty-four patients were included in the cohort. The average deviation from planned resection was found to be 2.2 mm. Histopathologic analysis confirmed all resection planes (bone) were tumour free, compared to 96.4% in the historic cohort. CONCLUSION: MRI-CT base tumour visualisation and 3D resection planning is a safe and accurate method for oncologic resection of the mandible. It is an improvement on the current methods reported for 3D resection planning based solely on CT data.

Patient-specific pre-contouring of osteosynthesis plates for mandibular reconstruction: Using a three-dimensional key printed solution.

PURPOSE: In mandibular reconstructive surgery, the osteosynthesis plates require contouring according to the patients' individual anatomical situation. These plates are frequently contoured around a three-dimensional (3D) printed model. However, the translation to the actual patient can introduce inaccuracies and unwanted rotations in the condyles and mandibular ramus, due to malpositioning of the pre-contoured plate. MATERIALS AND METHODS: This article describes an easy-access method for exact translation of the pre-contoured plate to the patient's mandible. This is done by using 3D printed guides that allow pre-drilling of screw holes in both the contour model and the patients' mandible. The accuracy of the Key Printed Solution was analysed by comparing the anatomical landmarks on both the 3D planned and post-operative models. RESULTS: The method was applied to 4 cases. All landmarks were identified on both the 3D planning and post-operative computed tomographic data. This showed an average deviation of 1.0 mm between planning and the post-operative result. The inter-observer variation was 0.6 mm (intra-class correlation, 0.75). CONCLUSION: This article presents an easy-to-use method for pre-bending the osteosynthesis plate and subsequent accurate translation of the intended contour with corresponding screw hole locations. The method was proved to be accurate and time-efficient.

Development of a patient-specific temporomandibular joint prosthesis according to the Groningen principle through a cadaver test series.

OBJECTIVES: Patients suffering from osteoarthritis, ankylosis (e.g. post-trauma or tumour) in the temporomandibular joint (TMJ) can present with symptoms such as severely restricted mouth opening, pain or other dynamic restrictions of the mandible. To alleviate the symptoms, a total joint prosthesis can be indicated, such as the Groningen TMJ prosthesis. This was developed as a stock device with a lowered centre of rotation for improved translational and opening capacity. This study aimed to improve the design of the prosthesis, and produce a workflow for a customized Groningen TMJ prosthesis, in order to make it more accurate and predictable. METHODS: The fossa and mandibular components of the Groningen TMJ prosthesis were customized. A series of five human cadavers was operated and bilateral TMJ prostheses were placed using custom cutting and drilling guides. Placement accuracy was evaluated based on post-operative CT data. RESULTS: A total of N = 10 prostheses were placed and analysed. The average Euclidean distance deviation from planned to actual position was 0.81 mm (SD 0.21). All prostheses were placed according to the routine surgical approaches and had an excellent alignment with the bony structures. CONCLUSION: The newly developed custom Groningen TMJ prosthesis can be placed with great accuracy and is the first step for improving TMJ total joint replacement surgery.

Secondary surgical management of osteoradionecrosis using three-dimensional isodose curve visualization: a report of three cases.

Osteoradionecrosis is defined as bone death secondary to radiotherapy. There is a relationship between the radiation dose received and the occurrence of osteoradionecrosis of the jaws, with the risk increasing above a dose of 60Gy. In cases of class III mandibular osteoradionecrosis, a segmental resection can be indicated. Current practice is to completely remove the affected bone up to the point where the bone looks healthy and is bleeding. Exact resection planning and the use of guided surgery based on imaging of the bone changes have not been reported so far. This article describes a method whereby the radiotherapy dose information is incorporated into the imaging of the affected bone in order to plan a three-dimensional (3D) virtual guided resection and reconstruction of the mandible in osteoradionecrosis. The method enables 3D visualization of each desired dose field in relation to the 3D model of the affected bone. Two types of application - for resection and reconstruction - are described.

The design, production and clinical application of 3D patient-specific implants with drilling guides for acetabular surgery.

An innovative procedure for the development of 3D patient-specific implants with drilling guides for acetabular fracture surgery is presented. By using CT data and 3D surgical planning software, a virtual model of the fractured pelvis was created. During this process the fracture was virtually reduced. Based on the reduced fracture model, patient-specific titanium plates including polyamide drilling guides were designed, 3D printed and milled for intra-operative use. One of the advantages of this procedure is that the personalised plates could be tailored to both the shape of the pelvis and the type of fracture. The optimal screw directions and sizes were predetermined in the 3D model. The virtual plan was translated towards the surgical procedure by using the surgical guides and patient-specific osteosynthesis. Besides the description of the newly developed multi-disciplinary workflow, a clinical case example is presented to demonstrate that this technique is feasible and promising for the operative treatment of complex acetabular fractures.

Splintless surgery: does patient-specific CAD-CAM osteosynthesis improve accuracy of Le Fort I osteotomy?

To analyse the accuracy of maxillary positioning after Le Fort I osteotomy, we retrospectively assessed the outcome in three patients (mean (range) age 40 (21 - 60) years) who had been treated with patient-specific CAD-CAM osteosynthesis plates as part of a bimaxillary osteotomy. Virtual surgical planning in each case was based on cone-beam computed tomography (CT) (Simplant® O&O, Dentsply Implants NV, Kessel-Lo, Belgium), and patient-specific CAD-CAM drilling guides and osteosynthesis plates were produced for maxillary positioning and fixation. We evaluated the accuracy of the placement by virtual comparison of the preoperative and postoperative images. In the upper dentition, postoperative analysis showed a mean (SD) deviation of 1.3 (1.4) mm from the preoperative plan. The method enables accurate placement of the maxilla, independent of the condyle or mandible, without the need for extraoral reference points.

Individual risk profiling for breast cancer recurrence: towards tailored follow-up schemes.

BACKGROUND: Breast cancer follow-up is not tailored to the risk of locoregional recurrences (LRRs) in individual patients or as a function of time. The objective of this study was to identify prognostic factors and to estimate individual and time-dependent LRR risk rates. METHODS: Prognostic factors for LRR were identified by a scoping literature review, expert consultation, and stepwise multivariate regression analysis based on 5 years of data from women diagnosed with breast cancer in the Netherlands in 2005 or 2006 (n=17,762). Inter-patient variability was elucidated by examples of 5-year risk profiles of average-, medium-, and high-risk patients, whereby 6-month interval risks were derived from regression estimates. RESULTS: Eight prognostic factors were identified: age, tumour size, multifocality, gradation, adjuvant chemo-, adjuvant radiation-, hormonal therapy, and triple-negative receptor status. Risk profiles of the low-, average-, and high-risk example patients showed non-uniform distribution of recurrence risks (2.9, 7.6, and 9.2%, respectively, over a 5-year period). CONCLUSION: Individual risk profiles differ substantially in subgroups of patients defined by prognostic factors for recurrence and over time as defined in 6-month time intervals. To tailor follow-up schedules and to optimise allocation of scarce resources, risk factors, frequency, and duration of follow-up should be taken into account.