Computer-aided position planning of miniplates to treat facial bone defects

In this contribution, a software system for computer-aided position planning of miniplates to treat facial bone defects is proposed. The intra-operatively used bone plates have to be passively adapted on the underlying bone contours for adequate bone fragment stabilization. However, this procedure can lead to frequent intra-operatively performed material readjustments especially in complex surgical cases. Our approach is able to fit a selection of common implant models on the surgeon's desired position in a 3D computer model. This happens with respect to the surrounding anatomical structures, always including the possibility of adjusting both the direction and the position of the used osteosynthesis material. By using the proposed software, surgeons are able to pre-plan the out coming implant in its form and morphology with the aid of a computer-visualized model within a few minutes. Further, the resulting model can be stored in STL file format, the commonly used format for 3D printing. Using this technology, surgeons are able to print the virtual generated implant, or create an individually designed bending tool. This method leads to adapted osteosynthesis materials according to the surrounding anatomy and requires further a minimum amount of money and time.Comment: 19 pages, 13 Figures, 2 Table

Myxofibroma of the maxilla. Reconstruction with iliac crest graft and dental implants after tumor resection

Odontogenic fibromyxomas are benign odontogenic tumors of mesenchymal origin of rare presentation in the oral cavity, which exhibit locally aggressive behavior and are prone to local recurrence. The controversy has mainly been on therapeutic management with recommendations varying, depending on the clinical cases, from simple curettage of lesion to segmental bone resection. We present a case report describing the reconstruction of an osseous defect in the maxilla and the restoration with dental implants in a 32 year old female patient after radical surgical excision due to an odontogenic fibromyxoma with locally aggressive behavior. The primary reconstruction of maxillary discontinuity defect was carried out by an immediate non-vascularized cortico-cancellous iliac crest graft. Using a computer-guided system for the implant treatment-planning, three dental implants were secondary placed in the bone graft by means of flapless implant surgery. The patient was subsequently restored with an implant-supported fixed prosthesis that has remained in continuous function for a period of three years. The surgical, reconstructive and restorative treatment sequence and techniques are discussed. © Medicina Oral S. L

Fuel qualification plan for the Advanced Neutron Source Reactor

This report describes the development and qualification plan for the fuel for the Advanced Neutron Source. The reference fuel is U{sub 3}Si{sub 2}, dispersed in aluminum and clad in 6061 aluminum. This report was prepared in May 1994, at which time the reference design was for a two-element core containing highly enriched uranium (93% {sup 235}U) . The reactor was in the process of being redesigned to accommodate lowered uranium enrichment and became a three-element core containing a higher volume fraction of uranium enriched to 50% {sup 235}U. Consequently, this report was not issued at that time and would have been revised to reflect the possibly different requirements of the lower-enrichment, higher-volume fraction fuel. Because the reactor is now being canceled, this unrevised report is being issued for archival purposes. The report describes the fabrication and inspection development plan, the irradiation tests and performance modeling to qualify performance, the transient testing that is part of the safety program, and the interactions and interfaces of the fuel development with other tasks

The Use of a 3D Printer in Pre-operative Planning for a Patient Requiring Acetabular Reconstructive Surgery.

INTRODUCTION: Surgical management of acetabular fractures is often highly complex, and a successful outcome depends upon an appreciation of the fracture pattern and the most appropriate approach to reduce and hold it. Currently, computed tomography (CT) images are used in conjunction with plain x-rays to identify the main fracture components and their spatial relationship to one another, and as such surgeons still have to make decisions based upon their ability to visualise the fracture from the images available. 3D printers have now become widely available and inexpensive, and can be used to rapidly produce life-size models based on CT scans of an individual patient. The availability of patient specific, accurate and detailed models of complex acetabular fractures can aid planning of surgical management on a patient specific basis. CASE REPORT: This report describes the use of a 3D printer to create a life-size model reconstruction of the pelvis of a 48 year old male patient who sustained a left sided associated both column acetabular fracture following a motorbike accident in the Sahara Desert. The model allowed visualisation of the multiple fracture fragments and their relative displacements. The tactile feedback allowed assessment of the different fracture fragments. The relative displacement of the quadrilateral plate and posterior column fragments could be assessed and the surgeon felt that these would be amenable to reduction from an ilioinguinal approach. An anatomic reduction was achieved and was held with the application of a pelvic brim plate with 2 screws lagging the posterior column/quadrilateral plate fragment. CONCLUSION: There are previous examples of 3D models being used in orthopaedic surgery through the use of rapid prototyping, however this method is usually expensive and time consuming. Advances in 3D printer technology offer surgeons a number of advantages when treating these complex fractures. With the ever-increasing economy, ease of use and speed of additive processing, the possible applications of this technology within orthopaedic surgery are numerous. Given the possible applications of this technology, and its ever increasing availability, we feel that its use can only improve patient outcomes and so should be explored further for use in orthopaedic surgery

Factors Influencing Fixation of Plates in Fracture Mandible: A Clinical and Biomechanical study

AIM : The symphysis and angle region are the most frequent sites for mandibular fractures. Direct application of 2.0mm conventional and locking titanium miniplates are the most commonly used intraoral open reduction and internal fixation technique today. Anatomic and biomechanical limitations continue to make this application technically challenging with a considerable complication rate. Such incongruences are analysed with respect to the complex biomechanical behaviour of the mandible. METHODOLOGY : Individual human mandible geometry, the specific bone density distribution, and the position and orientation of the masticatory muscles were evaluated by performing computed tomography scan of the cadaveric human mandible. Dimensional changes in the holes of the 2.0mm (Orthomax, Leforte and Synthes) titanium conventional and locking miniplates/screws were evaluated using RAPID-I Precision Vision Measuring System (VMS) pre and post adaptation to angle and symphysis region. The average bite forces of 15 patients who were operated for symphysis and angle fractures were measured using AXPERT electronic bite force gauge at 5 bite points viz right molars, right premolars, left molars, left premolars and anteriors. Three Dimensional Finite Element Analysis (3D FEA) was performed for symphysis and angle fracture sites with Temporomandibular Joint remaining static. Deflection, stability, mechanical stress over bone, maximal stress over miniplate, fracture gap and direction of displacement evaluated for loading conditions. RESULTS : Symphysis fracture fixation showed maximum deflection of 6.05196mm with Orthomax conventional and least of 2.50747mm with Leforte locking miniplates. Maximum stress over bone was 98.6587 Mpa with Orthomax conventional and least was with Synthes locking of about 78.476 MPa. Stress over plate was more of about 75.4011 MPa in Orthomax conventional and least of about 61.2447 MPa in Synthes locking. Fracture gap was more of about 0.86241mm in Orthomax conventional and least of about 0.01804mm with Leforte locking. Angle fracture fixation showed maximum deflection of 5.93459mm with Orthomax conventional and least of about 3.00287mm with Synthes locking plates. Maximum stress over bone was more of about 379.81 Mpa for Orthomax conventional and least of about 309.63 MPa for Synthes locking plates. Stress over plate was more of about 2114.62 MPa in Orthomax conventional and least of about 833.457 MPa in Synthes locking. Fracture gap was more of about 2.2708mm in Orthomax conventional and least of about 1.86241mm with Leforte locking. CONCLUSION : Consecutive rapid failure of the miniplates could not be prevented when the angle and symphysis region are loaded with vertical bite forces. The more stable plate is Synthes locking plate followed by Leforte locking plate for the symphysis region and angle region. The static yield limit of titanium exceeds, when geometry and dimension of the miniplates get altered, while adapted to angle and symphysis region. Hence, the dimensional changes in the holes of miniplates occurring during adaptation of the plate to the fracture site are also a factor to be considered for stability of the plate

Biodegradable versus tutanium plates and screws in maxillofacial surgery

Nowadays, titanium is regarded as the ‘golden standard’ for fixation of bone segments. It appears to be necessary that titanium is removed following bone healing in a second operation in 5-40% of the cases. Biodegradable fixation systems have been developed to dissolve gradually in the human body in order to reduce or even delete the problems associated with titanium plate removal. Despite this supposed advantage of biodegradable osteofixation devices, these systems have not replaced the titanium systems, and are currently applied in only limited numbers. The major drawback for general use of biodegradable devices is the lack of clinical evidence for well-defined indications. Therefore, we performed a prospective multicenter randomized controlled trial. 230 patients who underwent an osteotomy and those treated for fractures of/in the facial skeleton, were randomly assigned to a titanium group (KLS Martin) or to a biodegradable group (Inion CPS). Briefly, short-term healing outcomes were similar between biodegradable and titanium fixation. However, there were more biodegradable plate removals, due to adverse tissue reactions to degradation products of the biodegradable material, within the first 2 post-operative years, and the costs associated with the biodegradable system were higher. Therefore, the biodegradable system was considered less cost-effective. The relapse 2 years post-operatively in patients who underwent an osteotomy was comparable between both groups. Considering the above, there appears to be no place for biodegradable plates and screws of Inion CPS in the regular treatment spectrum of osteotomies and fractures in/of the facial skeleton, and titanium should remain the ‘golden standard’