Comparing the Bone Healing After Cold Ablation Robot-Guided Er:YAG Laser Osteotomy and Piezoelectric Osteotomy-A Pilot Study in a Minipig Mandible.

BACKGROUND AND OBJECTIVE: To take major advantage of erbium-doped yttrium aluminium garnet (Er:YAG) lasers in osteotomy-like freedom of cutting geometries and high accuracy-the integration and miniaturization of the robot, laser, and navigation technology was tried and applied to minipigs. The investigators hypothesized laser osteotomy would render acceptable bone healing based on the intraoperative findings and postoperative cut surface analysis. STUDY DESIGN/MATERIALS AND METHODS: We designed and implemented a comparative bone-cutting surgery in the minipig mandible with a cold ablation robot-guided Er:YAG laser osteotome (CARLO) and a piezoelectric (PZE) osteotome. The sample was composed of different patterns of defects in the mandibles of six grown-up female Goettingen minipigs. The predictor variable was Er:YAG osteotomy and PZE osteotomy. The outcome variable was the cut surface characteristics and bone healing at 4 and 8 weeks postoperatively. Descriptive and qualitative comparison was executed. RESULTS: The sample was composed of four kinds of bone defects on both sides of the mandibles of six minipigs. We observed more bleeding during the operation, open-cut surfaces, and a faster healing pattern with the laser osteotomy. There was a possible association between the intraoperative findings, postoperative cut surface analysis, and the bone healing pattern. CONCLUSIONS: The results of this study suggest that characteristic open-cut surfaces could explain favorable bone healing after laser osteotomy. Future studies will focus on the quantification of the early healing characteristics after laser osteotomy, its diverse application, and the safety feature. Lasers Surg. Med. © 2020 Wiley Periodicals LLC.

The Use of Finite Element Method Analysis for Modeling Different Osteotomy Patterns and Biomechanical Analysis of Craniosynostosis Correction.

PURPOSE: Several post-processing algorithms for 3D visualization of the skull in craniosynostosis with their specific advantages and disadvantages have been already described. The Finite Element Method (FEM) described herein can also be used to evaluate the efficacy of the cutting patterns with respect to an increase in the projected surface area under assumed uniform loading of the manipulated and cut bone segments. METHODS: The FEM analysis was performed. Starting with the classic cranial osteotomies for bifrontal craniotomy and orbital bandeau a virtually mirroring of the unaffected triangular shaped frontal bone was performed to achieve a cup-shaped sphere of constant thickness of 2.5 mm with a radius of 65 mm. Mechanical properties required for the analysis were Young's modulus of 340 MPa and Poisson's ratio of 0.22. Four different cutting patterns from straight to curved geometries have been projected onto the inner surface of the sphere with a cutting depth set to 2/3rds of the shell thickness. The necessary force for the deformation, the resulting tensions and the volume loss due to the osteotomy pattern were measured. RESULTS: Better outcomes were realized with pattern D. The necessary force was 73.6% smaller than the control group with 66N. Best stress distribution was achieved. Curved cutting patterns led to the highest peak of stress and thus to a higher risk of fracture. Straight bone cuts parallel to the corners or to the thighs of the sphere provided a better distribution of stresses with a small area with high stress. Additionally, also with pattern D a surface increase of 20.7% higher than reference was registered. CONCLUSION: As a proof of concept for different cutting geometries for skull molding in the correction of craniosynostosis, this computational model shows that depending of the cutting pattern different biomechanical behavior is achieved.

A comparative investigation of bone surface after cutting with mechanical tools and Er:YAG laser.

BACKGROUND AND OBJECTIVES: Despite of the long history of medical application, laser ablation of bone tissue became successful only recently. Laser bone cutting is proven to have higher accuracy and to increase bone healing compared to conventional mechanical bone cutting. But the reason of subsequent better healing is not biologically explained yet. In this study we present our experience with an integrated miniaturized laser system mounted on a surgical lightweight robotic arm. STUDY DESIGN/MATERIALS AND METHODS: An Erbium-doped Yttrium Aluminium Garnet (Er:YAG) laser and a piezoelectric (PZE) osteotome were used for comparison. In six grown up female Göttingen minipigs, comparative surgical interventions were done on the edentulous mandibular ridge. Our laser system was used to create different shapes of bone defects on the left side of the mandible. On the contralateral side, similar bone defects were created by PZE osteotome. Small bone samples were harvested to compare the immediate post-operative cut surface. RESULTS: The analysis of the cut surface of the laser osteotomy and conventional mechanical osteotomy revealed an essential difference. The scanning electron microscopy (SEM) analysis showed biologically open cut surfaces from the laser osteotomy. The samples from PZE osteotomy showed a flattened tissue structure over the cut surface, resembling the "smear layer" from tooth preparation. CONCLUSIONS: We concluded that our new finding with the mechanical osteotomy suggests a biological explanation to the expected difference in subsequent bone healing. Our hypothesis is that the difference of surface characteristic yields to different bleeding pattern and subsequently results in different bone healing. The analyses of bone healing will support our hypothesis.

How much dentists are ethically concerned about overtreatment; a vignette-based survey in Switzerland.

BACKGROUND: Overtreatment (or unnecessary treatment) is when medical or dental services are provided with a higher volume or cost than is appropriate. This study aimed to investigate how a group of dentists in Switzerland, a wealthy country known to have high standards of healthcare including dentistry, evaluated the meaning of unnecessary treatments from an ethical perspective and, assessed the expected frequency of different possible behaviors among their peers. METHODS: A vignette describing a situation that is susceptible for overtreatment of a patient was presented to a group of dentists. The vignette was followed by five options. A questionnaire including the vignette was posted to 2482 dentists in the German-speaking areas of Switzerland. The respondents were asked to rate each option according to their estimation about its prevalence and their judgment about the degree to which the behavior is ethically sound. RESULTS: 732 completed questionnaires were returned. According to the responses, the most ethical and the most unethical options are considered to be the most and the least prevalent behaviors among dentists practicing in Switzerland, respectively. CONCLUSIONS: Suggesting unnecessary treatments to patients seems to be an ethically unacceptable conduct in the eyes of a sample of dentists in Switzerland. Although the respondents believed their colleagues were very likely to behave in an ethical way in response to a situation that is susceptible to overtreatment, they still seemed to be concerned about the prevalence of unethical behaviors in this regard.

A computer-assisted diagnostic and treatment concept to increase accuracy and safety in the extracranial correction of cranial vault asymmetries.

PURPOSE: Proteus syndrome is described as a progressive, asymmetric, disproportional overgrowth of various parts of the body. The theory of somatic mosaicism is widely accepted to be the cause of this disease. Affected patients present very heterogeneous symptoms, but in about 30% craniofacial deformities are the leading clinical features. Because no causal therapy exists, treatment options are limited to surgical improvement of functional constraints. MATERIALS AND METHODS: A computer-assisted method was used to increase the accuracy and safety of bone removal in the extracranial correction of cranial vault asymmetries. Descriptions of the diagnosis, preoperative planning, and intraoperative management of craniofacial dysmorphia caused by Proteus syndrome in a 6-year-old boy are presented. After computed tomography-based generation of a virtual 3-dimensional (3D) model of the patient and a haptic stereolithographic model to display the special pathology, flow-sensitized 4-dimensional magnetic resonance imaging was performed to clarify the properties of vascular formation inside the hyperostosis. To transfer the mathematically optimized preoperative planning of a new skull shape to the patient, a surgical guide was fabricated by rapid manufacturing. Intraoperative 3D real-time navigation was installed as an additional visualization and security feature. RESULTS: The surgery could be performed safely and quickly. Postoperative imaging showed that the surgical plan was realized with high accuracy. CONCLUSION: This newly developed and validated method can be successfully implemented in the operating room environment.

First-in-man application of a cold ablation robot guided laser osteotome in midface osteotomies.

The aim of the study was to assess the clinical applicability of robot guided laser osteotomy for clinical application. This is the initial report on 14 consecutive patients requiring an orthognathic procedure with a midface osteotomy (no restrictions made on the surgical indication itself) who have undergone surgery by means of the Cold Ablation Laser Osteotome CARLO® (AOT Advanced Osteotomy Tools, Basle, Switzerland), which is an integrated system, functionally comprising: an Er:YAG laser source, intended to perform osteotomies using cold laser ablation, a robot arm that controls the position of the laser source, an optical tracking device that provides a continuous and accurate measurement of the position of the laser source and of reference elements attached to instruments or bones, a navigation system (software) that is able to read preoperatively defined planned osteotomies, and - under the control of a surgeon - performs the planned osteotomies. Safety was assessed by unimpaired postoperative healing and the absence of device related injuries; performance was assessed as ability to cut the maxilla along the preoperatively planned cutting path with a rage of accuracy of 2mm. Cold ablation robot-guided laser osteotomy could successfully be performed in 14 consecutive patients. No intraoperative complications or technical failure occurred. All osteotomies were within an average deviation of 0.80 mm (±0.26 mm) of the virtually preplanned location. The registration procedure to set up the robot at the beginning of the operation required a mean time of 4.6 min (±5.3min). In this report we describe the effective and successful routine use of Cold ablation robot-guided laser osteotomy in an actual clinical setting. It is a promising technical innovation that has the potential to set new standards for accuracy and safety in orthognathic surgery.

Cold Ablation Robot-Guided Laser Osteotome (CARLO®): From Bench to Bedside.

BACKGROUND: In order to overcome the geometrical and physical limitations of conventional rotating and piezosurgery instruments used to perform bone osteotomies, as well as the difficulties in translating digital planning to the operating room, a stand-alone robot-guided laser system has been developed by Advanced Osteotomy Tools, a Swiss start-up company. We present our experiences of the first-in-man use of the Cold Ablation Robot-guided Laser Osteotome (CARLO®). METHODS: The CARLO® device employs a stand-alone 2.94-µm erbium-doped yttrium aluminum garnet (Er:YAG) laser mounted on a robotic arm. A 19-year-old patient provided informed consent to undergo bimaxillary orthognathic surgery. A linear Le Fort I midface osteotomy was digitally planned and transferred to the CARLO® device. The linear part of the Le Fort I osteotomy was performed autonomously by the CARLO® device under direct visual control. All pre-, intra-, and postoperative technical difficulties and safety issues were documented. Accuracy was analyzed by superimposing pre- and postoperative computed tomography images. RESULTS: The CARLO® device performed the linear osteotomy without any technical or safety issues. There was a maximum difference of 0.8 mm between the planned and performed osteotomies, with a root-mean-square error of 1.0 mm. The patient showed normal postoperative healing with no complications. CONCLUSION: The newly developed stand-alone CARLO® device could be a useful alternative to conventional burs, drills, and piezosurgery instruments for performing osteotomies. However, the technical workflow concerning the positioning and fixation of the target marker and the implementation of active depth control still need to be improved. Further research to assess safety and accuracy is also necessary, especially at osteotomy sites where direct visual control is not possible. Finally, cost-effectiveness analysis comparing the use of the CARLO® device with gold-standard surgery protocols will help to define the role of the CARLO® device in the surgical landscape.

Three-dimensional imaging of the larynx for pre-operative planning of laryngeal framework surgery.

Modern laryngeal framework surgery (LFS) requires an exact understanding of the laryngeal biomechanics and precise pre-operative planning, for which bi-planar imaging is not sufficient. The aim of the study was to test whether MIMICS, a commercially available software package for three-dimensional (3D) rendering of high-resolution computerised tomography (HRCT), is suitable for 3D imaging of the larynx, analysis of laryngeal biomechanics and pre-operative planning. We examined four cadaver larynx and one patient larynx. In the five larynges, all relevant structures and landmarks could be 3D visualised. Superimposing of two HRCT scans shows that when the arytenoids move from 'respiration' to 'phonation', they perform a rotating, translating and tilting motion. Moreover, we could demonstrate that the vocal fold elongates by 7% with cricothyroid approximation. We conclude that MIMCS is well suited for 3D imaging of the larynx, analysis of laryngeal biomechanics and pre-operative planning of LFS procedures.

Performing partial mandibular resection, fibula free flap reconstruction and midfacial osteotomies with a cold ablation and robot-guided Er:YAG laser osteotome (CARLO®) - A study on applicability and effectiveness in human cadavers.

OBJECTIVE: Aim of the study was to prove the safety, accuracy characteristics of contact-free laser osteotomy executed with the cold ablation and robot-guided Er:YAG laser osteotome in a human cadaver test. MATERIAL AND METHODS: On six human cadavers mandible resections with a swallowtail like pattern were performed with the laser system on each side. The defects were reconstructed with a fibula graft of identical design and enlarged by 0.2 units. Mandibles and fibulas width as well surgery times were recorded. Additionally a Le Fort I and median mandible split were done. Macroscopically, the bone margins were examined for necrosis. RESULTS: Laser osteotomies of the mandible up to a depth of 23 mm were possible without any thermal damage. Repeatability and precision of the system could be easily assessed. With the navigation system precise control of localization was achievable. Mean surgery time for the mandible resection was 13.32 min and for the fibula osteotomy 12.38 min. CONCLUSION: The simply transmission of a cold ablation and robot-guided laser osteotome in an operation room identical environment for surgical interventions could be demonstrated. Precise osteotomy patterns with freedom in the design and carbonisation-free cut surfaces have been shown.

Accuracy of soft tissue prediction in surgery-first treatment concept in orthognathic surgery: A prospective study.

PURPOSE: The purpose of this study was to provide a quantitative accuracy assessment of soft tissue predictions generated by a computer-aided maxillofacial planning system in patients undergoing orthognathic surgery following the "surgery-first" treatment. MATERIALS AND METHODS: For this study, we looked at 16 patients with open bite dentofacial-dysmorphosis who underwent orthognathic surgery. Surgeries were planned using conventional sketches and the newly developed computer-assisted SOTIRIOS planning software (developed by the authors). Validation procedures were performed in the following steps: (1) Standardized registration of the pre- and postoperative CT volumes; (2) Automated adjustment of the bone-related preoperative planning to the actual postoperative bony displacement; (3) Simulation of soft tissue changes according to the definitive bony movements; and (4) Calculation of soft tissue differences between the predicted and the actual 6-month postoperative results by distance mapping. RESULTS: The program produced a clinically satisfactory 3D soft tissue prediction, with a mean error of 1.46 mm ± 1.53 mm. The program was suitable for use in virtual surgical planning without technical assistance. CONCLUSION: This study shows that the program is quite accurate, enabling the surgeon to predict the outcome of the soft tissue. This has the potential to promote the routine application of the surgery-first approach in patients suffering from open bite.

Is subcranial Le Fort III plus Le Fort I osteotomy stable?

The purpose of this study was to test whether associated subcranial Le Fort III (sLF III) and Le Fort I (LF I) osteotomies are stable after large advancements of the middle third of the face and maxilla. The authors designed a retrospective study and enrolled a sample of consecutive patients with midface hypoplasia treated with associated sLF III and LF I osteotomies in this IRB-approved study between September 2013 and February 2015. To test whether the long-term stability was satisfactory, the authors compared cephalometric changes from immediately after surgery to 18 months after surgery taken from multi-slice computed tomography using two different third-party imaging software programs. Statistical significance was set as P ≤ 0.05. The sample comprised 11 patients (mean age 23.84 ± 4.17 yr; 54% men). The mean advancement of the upper incisor immediately after surgery was 10.03 ± 1.6 mm. After 18 months, the position of the upper incisor did not vary significantly (10.18 ± 2.35 mm). All other cephalometric landmarks did not present statistically significant differences between immediately after and 18 months after surgery, with horizontal and vertical variations of less than one millimetre. This study supports that sLF III and LF I osteotomies are effective in maintaining stable horizontal and vertical skeletal positioning after surgery.

Treatment of condylar fractures with an intraoral approach using an angulated screwdriver: results of a multicentre study.

BACKGROUND: This multicentre study aimed to investigate long-term radiographic and functional results following the treatment of condylar fractures using an angulated screwdriver system and open rigid internal fixation with an intraoral surgical approach. METHODS: Twenty-nine patients with a total of 32 condylar fractures were evaluated. The patients were investigated prospectively based on the following variables: age, sex, aetiology, side, location and classification of the fracture, degree of displacement, associated fractures, surgical approach, oral health status, type of osteosynthesis plate, duration of surgery, mouth-opening, complications, and duration of follow-up. RESULTS: The fractures were classified as subcondylar (n = 25) or condylar neck (n = 7). Mean patient age was 36.38 ± 16.60 years. The median duration of postoperative follow-up was 24.39 ± 13.94 months. No joint noise, weakness of the facial nerve, joint pain, or muscle pain was observed. An additional retromandibular approach was necessary to enable the treatment of one subcondylar fracture with medial displacement. CONCLUSION: Subcondylar or condylar neck fractures with medial or lateral displacement can be treated using an intraoral approach with satisfactory results with the advantages of the absence of visible scarring, the avoidance of facial nerve injury, and the ability to obtain rapid access to the fracture.

Odontogenic myxoma: diagnostic and therapeutic challenges in paediatric and adult patients--a case series and review of the literature.

INTRODUCTION: Odontogenic myxomas are benign but locally invasive tumours originating from primordial mesenchymal tooth forming tissues which do not metastasise. We present a series of two paediatric and two adult cases and focus on differences in diagnostic and therapeutic approaches between children and adults based on our own experience and a critical review of the literature.

Biomechanics of the cricoarytenoid joint: three-dimensional imaging and vector analysis.

OBJECTIVES/HYPOTHESIS: Laryngeal framework surgery requires a good understanding of the biomechanics of the cricoarytenoid (CA) joint, the precise function of which is still only poorly understood. The aim of the study was (1) to show that, by superimposing two or more three-dimensional (3D) images, we can visualize the exact position of the arytenoid cartilages within the larynx at different phases of their movement; and (2) to demonstrate that it is possible to analyze the arytenoid cartilage movements mathematically with the help of vector analysis. STUDY DESIGN: In vitro cadaver study. METHODS: Twenty fresh and intact cadaver larynges were scanned by high-resolution computerized tomography with the arytenoid cartilages in "respiratory" position and in "phonatory" position. The two positions were superimposed and rendered in 3D with MIMICS (Materialise Interactive Medical Image Control System, Leuven, Belgium). The spatial trajectory of the arytenoid cartilage movements was calculated with vector analysis. RESULTS: The movement from the "respiratory" to the "phonatory" position has three components: (1) an inward rocking action around the longitudinal CA joint; (2) a forward sliding movement along the longitudinal axis of the CA joint; and (3) an inward rotation around a virtual axis that runs perpendicular to the CA joint axis. CONCLUSIONS: Superimposing 3D images of the larynx with the help of the software package MIMICS allows us to visualize and to analyze mathematically the trajectory of the arytenoid cartilage. The arytenoid cartilages rock inward, slide forward, and rotate inward when they move from the "respiratory" to the "phonatory" position.

Enabling an unimpeded surgical approach to the skull base in patients with cranial hyperostosis, exemplarily demonstrated for craniometaphyseal dysplasia.

Craniometaphyseal dysplasia is an extremely rare, genetic bone-remodeling disorder. Comparable to osteopetrosis, fibrous dysplasia, and other infrequent conditions, craniometaphyseal dysplasia is characterized by progressive diffuse hyperostosis of the neuro- and viscerocranium. Affected patients present with a pathognomonic dysmorphia: macrocephalus, hypertelorism, bulky facial skeleton, and a prominent mandible. Progressive thickening and petrification of the craniofacial bones can continue throughout life, often resulting in neurological symptoms due to obstruction of the cranial nerves in the foramina and therefore immediately requiring neurosurgical interventions to avoid persistent symptoms with severe impairment of function. Treatment is largely infeasible given the lack of suitable tools to perform a craniotomy through the gross calvarial bone. In this paper, the authors present a complete process chain from the CT-based generation of an individual patient's model displaying his pathology to optimized preoperative planning of the skull's shape with a thickness of about 6-7 mm. For concise verification of the surgical plan in an operating room environment, a 3D real-time navigation prototype system was utilized. To guarantee realization of the surgery in a reasonable time frame, the mechanical tools were preoperatively selected for optimizing the ablation rate in porcine and bovine bone, which were comparable to that in the patient. This process chain was developed in a modular way, so that it could be easily adopted completely or partially for other surgical indications. A 21-year-old man was treated according to this sophisticated concept. Skull bone more than 50 mm thick in some regions was reduced to physiological thickness. The patient was thus in a stage that neurosurgical interventions could be performed with a regular risk within a reasonable time of treatment.

Developing a 3D model of the laryngeal cartilages using HRCT data and MIMICS's segmentation software.

Discussions relating to the biomechanics of the larynx are still generally controversial. The purpose of this study is to develop a 3D model of the larynx based on high-resolution computer tomography (HRCT) data identifying and visualizing anatomical landmarks and structures of the larynx. We examined four fresh cadaver larynges with HRCT. The DICOM (Digital Imaging and Communication in Medicine) data were post-processed with the software package MIMICS for three-dimensional visualization. All relevant structures of the laryngeal cartilages could be identified on HRCT and visualized in a 3D model. We conclude that 1) HRCT provides excellent data for three-dimensional visualization of the laryngeal anatomy, and 2) the combined technology of HRCT and MIMICS is useful to study the biomechanics on 3D images and for preoperative planning of laryngeal framework surgery.