Anatomical background for the development of preformed cranioplasty implants.

Preformed cranioplasty implants form a new concept of implants to repair relatively large-sized calvarial defects. They could offer an alternative treatment to manually molded cranioplasty, and to flat or patient specific implants, while still achieving a satisfactory clinical result.We report on 3D statistical modeling and analysis performed in 80 clinical CT data of adult European Whites with unaffected calvarial bones to establish an anatomical background for the development of preformed alloplastic cranioplasty implants.Most size and shape (=form) variation was observed bilateral symmetrically in the central temporal region, showing up to 26.8 mm variation and 9.4 mm standard deviation from the mean form. Large deviation was also observed in the central lower forehead, in the central occipital region at the protuberantia occipitalis externa and laterally to it. An intermediate variation was detected at the transition area from the temporal to other regions, as well as in the frontal and occipital area. The cranial roof, the temporal fossa, and the nuchal region exhibited the lowest variability with a standard deviation of about 4 mm. Principal components analysis revealed no relevant shape but a significant size difference between genders. Size contributed to 24.4% of the overall form variability. The mean surface area difference between genders was 67 cm.The size and number of implant forms required have to be referred to the relatively large anatomical variation experienced, and also to considerations related to implant location, design, and material. A rigid material is considered to significantly increase the number of implants forms, especially when repairing relatively large-sized defects.

An evaluation of face-bow transfer for the planning of orthognathic surgery.

PURPOSE: The purpose of this study was to evaluate the error magnitude in the clinical application of face-bow devices. Technical and methodologic inaccuracies, as well as deviations from reference planes, were determined. MATERIALS AND METHODS: The presented method is part of a 3-dimensional virtual planning procedure for orthognathic surgery and included 15 patients with dentoskeletal deformities. Cone beam computed tomography datasets obtained from patients with a referenced face-bow plane and a centric registration splint were matched with cone beam computed tomography datasets of the registered plaster model of the maxilla mounted in an articulator. To assess potential sources of methodologic errors, angulations were measured between the virtual face-bow plane and the horizontal cross bar of the virtual articulator. To evaluate the reproducibility of the anatomic reference plane, angulations between the Frankfort plane and the horizontal cross bar of the articulator were measured. Statistical significance was set at P < .05 and tested by univariate analysis of variance. RESULTS: Technical and methodologic errors showed a mean deviation of 3.5°, with a median of 3.6° and SD of 2.7°. The values did not reach statistical significance (P = .1). However, there was a significant error (P < .05) in determining the position of the anatomic reference plane by face-bow transfer. The mean deviation was 7.7° (values ranged between 1.2° and 18.9°), with a median of 6.7° and SD of 5.3°. CONCLUSIONS: In this study the traditional use of face-bow devices showed inaccuracies in model mounting as well as in assignment of anatomic reference planes. Three-dimensional virtual computer-assisted planning seems to be more accurate than conventional methods.

Anatomy-based surgical concepts for individualized orbital decompression surgery in graves orbitopathy. II. Orbital rim position and angulation.

PURPOSE: To detect anatomical conditions that may benefit from an orbital rim advancement procedure in patients suffering from Graves orbitopathy. METHODS: In postprocessed 70 clinical CTs from adults of white European ethnicity with unaffected orbits, the authors assessed the intra- and interindividual variability of the orbital rim angulation and orbital rim position relative to their medial rim parts. This included morphometrical analysis and computer model visualization using Amira software (version 5.3.1, Visage Imaging GmbH, Berlin, Germany). RESULTS: Significant variation was observed in rim angulation, varying up to 16.6° in different individuals. A large variability of the sagittal rim position became evident, with the highest at the lateral orbital rim being 1.1 cm. CONCLUSIONS: These anatomical data may be used to benchmark the given Graves orbitopathy patients. CT assessment to detect and quantify orbital rim pro-/retrusion may help to decide whether orbital rim advancement may be considered for orbital decompression/enlargement.

In vitro biomechanical comparison of the effect of pattern, inclination, and size of positional screws on load resistance for bilateral sagittal split osteotomy.

PURPOSE: The purpose of this in vitro investigation was to determine whether the pattern, angle of placement, or size of positional screws affected their ability to resist vertical loads resembling mastication in the bilateral sagittal split osteotomy system. MATERIALS AND METHODS: Standardized bone substitutes were secured with three 12- to 16 mm-long, 1.85-, 2.0-, 2.1-, and 2.4-mm outer diameter, self-tapping titanium screws (Synthes, Solothurn, Switzerland) in various patterns using a positional screw technique. These patterns included transbuccal triangular, intraoral triangular, and transbuccal linear patterns. The models were secured in a jig and subjected to vertical loads by a mechanical testing unit (1475 UPM; Zwick, Ulm, Germany) until failure. Loading test data analysis was based on peak load values resulting in mechanical deformation of the system (1-, 3-, and 5-mm displacement), maximal force, and stiffness (load/displacement slope curve) for each group. Means and standard deviations were derived and compared for statistical significance using univariate analysis of variance with a confidence level of 95% (P values < .05). RESULTS: The designed study demonstrated that 1.85- and 2.0-mm-diameter positional screws provided similar stability in all 3 setups. Three screws placed in an inverted L pattern at 90° (simulating a transbuccal approach) showed significantly higher resistance to vertical forces for advancement movements at 1-, 3-, and 5-mm displacement when compared with the inverted L group of screws placed at an angle (intraoral approach) or 3 screws in a linear pattern placed at 90° (transbuccal approach) (P < .01). CONCLUSIONS: Under the conditions tested in this in vitro study, differences in the load resistance of positional screws placed in a transbuccal or intraoral approach could be demonstrated depending on the fixation technique. The transbuccal group of 3 screws in an inverted L pattern showed significantly greater stability than the intraoral group of 3 screws placed in an inverted L pattern and the transbuccal group of 3 screws in a linear pattern. Resistance to vertical loads with 1.85-mm screws was similar to that with the standard 2.0-mm screws in all 3 setups. The results of this study suggest that the angle of screw placement (surgical approach) and pattern have a greater influence on the stability of the bilateral sagittal split osteotomy system than the screw size.

Prediction of surface area size in orbital floor and medial orbital wall fractures based on topographical subregions.

OBJECTIVE: This retrospective study evaluates the occurrence and frequency of different fracture patterns in a series of computed tomography (CT) scans in terms of the AOCMF Trauma Classification (TC) orbit module and correlates the assigned defects with measurements of the fracture area in order to get an approximate guideline for fracture size predictions on the basis of the classification. MATERIAL AND METHODS: CT scans of patients with orbital floor fractures were evaluated using the AOCMFTC to determine the topographical subregions. The coding consisted of: W = orbital wall, 1 = anterior orbit, 2 = midorbit, i = inferior, m = medial. The 3-dimensional surface area size of the fractures was quantified by the "defect body" method (Brainlab, Munich, Germany). The fracture area size and its confidence and prediction interval within each topographical subregion was estimated by regression analysis. RESULTS: A total of 137 CT scans exhibited 145 orbital floor fractures, which were combined with 34 medial orbital wall fractures in 31 patients. The floor fractures - W1(i)2(i) (n = 86) and W1(i) (n = 19) were the most frequent patterns. Combined floor and medial wall fractures most frequently corresponded to the pattern W1 (im)2 (im) (n = 15) ahead of W1 (im) 2(i) (n = 10). The surface area size ranged from 0.11 cm2 to 6.09 cm2 for orbital floor and from 0.29 cm2 to 5.43 cm2 for medial wall fractures. The prediction values of the mean fracture area size within the subregions were computed as follows: W1(i) = 2.25 cm2, W2(i) = 1.64 cm2, W1(i)2(i) = 3.10 cm2, W1(m) = 1.36 cm2, W2(m) = 1.65 cm2, W1(m)2(m) = 2.98 cm2, W1 (im) = 3.35 cm2, W1 (im) 2(i) = 4.63 cm2, W1 (im)2(m) = 4.06 cm2 and W1 (im)2 (im) = 7.16 cm2. CONCLUSION: The AOCMFTC orbital module offers a suitable framework for topographical allocation of fracture patterns inside the infero-medial orbital cavity. The involvement of the subregions is of predictive value providing estimations of the mean 3-D fracture area size.

Anatomy-based surgical concepts for individualized orbital decompression surgery in graves orbitopathy. I. Orbital size and geometry.

PURPOSE: To analyze orbital morphological parameters that potentially could influence the effect of decompression surgery on exophthalmos reduction in Graves orbitopathy, thus making decompression surgery more predictable. METHODS: To generate a reference database, a CT-based study was performed in 140 orbits obtained from adult patients with unaffected orbits in a European white ethnicity. The following parameters were chosen: orbital volume, globe volume, globe to orbital volume ratio, and orbital cone angle. Volumes were measured on postprocessed CT data using morphometric techniques. To define the cone angle, a 3-dimensional approach was chosen using the program Amira. RESULTS: Significant interindividual variation was found in orbital volume from 18.9 to 33.4 ml and in globe volume from 6.0 to 10.1 ml. The globe to orbital volume ratio showed a relatively broad variation from 0.25 to 0.4. Differences in the orbital cone angle from 39.7° to 65.7° were observed. CONCLUSION: The experienced large variations in orbital morphology might significantly influence the degree of exophthalmos reduction, which can be obtained by standardized decompression procedures. Based on our results, a prospective clinical study will be conducted to test our hypothesis.

A method for assessing 3D shape variations of fuzzy regions and its application on human bony orbits.

In complex orbital defects, typically the eye globe is retruded in a pathological position. This is associated with severe functional and cosmetic post-traumatic conditions. Characteristically, the posterior orbital floor and the medial wall of the bony orbit (=region of interest, ROI) is fractured where adequate reconstruction is crucial for a satisfactory surgical outcome but difficult to achieve. By introducing the concept of preshaped, navigated orbital implants, the repair of complex orbital fracture patterns could be significantly facilitated and improved. However, this ROI, delineated according to surgical criteria, cannot be defined by distinct anatomical landmarks because of the absence of reliable anatomical features. The determination of homologous surface points therefore remains a problem in such regions. The aim of this study was to provide a method for the assessment of the 3D shape of the ROI and of its variability, respectively. By aligning an anatomically determinable region that embeds the region of interest with a thin plate spline, transformation homology can be determined suitable for subsequent state-of-the-art shape analysis. First results of shape variations are illustrated and give hints into the future of optimized implant design.

Imaging in Graves' orbitopathy.

In patients with Graves' orbitopathy, magnetic resonance imaging (MRI) is a useful tool to distinguish the acute inflammatory active disease in demonstrating interstitial edema within the extraocular muscles on coronal TIRM-sequences from fibrotic, inactive endstage disease. MRI is the modality of choice to identify active inflammatory changes in order to decide on possible immunomodulatory treatment response. However, MRI should be considered in atypical cases as in asymmetrical orbital involvement, to exclude other orbital pathologies and to confirm the clinical suspicion of apical optic nerve compression in Graves' orbitopathy. Computed tomography (CT) provides precise imaging of the osseous periorbital structures and does not reveal information on the disease activity in most cases. It is therefore the method of choice to plan CT-guided orbital decompression surgery in the inactive phase of disease.

[The interdisciplinary fixed restoration of an edentulous maxilla with a pronounced resorption of the alveolar crest. A case report. Part I: The immediate reconstruction]. / Die interdisziplinäre festsitzende Rekonstruktion eines zahnlosen Oberkiefers mit ausgeprägter Resorption des Alveolarfortsatzes. Ein Fallbericht. Teil 1: Die Sofortversorgung.

Edentulous patients wearing a conventional complete denture often request a fixed restoration for functional, esthetical and/or psychosocial reasons. For these patients implant-supported fixed dental prostheses are a prosthetic means of choice. However, after years of edentulism often a marked resorption of the alveolar crest has taken place, asking for bone augmentation before implant placement. Thus, fixed implant reconstructions are time and cost intense and stressful for the patient. This case report documents the immediate fixed reconstruction in the edentulous maxilla after ridge augmentation with a cortical cancellous bone graft from the iliac crest and implant placement. A CAD/CAM-system was used for implant planning and the fabrication of a drilling guide. The prosthetic reconstruction was inserted immediately after implant placement.

[The prosthetic rehabilitation of a patient after gunshot wound and initial maxillofacial surgical reconstruction. A case report]. / Die defektprothetische Versorgung eines Patienten mit Status nach einer Schussverletzung und chirurgischer Rekonstruktion. Ein Fallbericht.

An improvement of prognosis after tumour therapy as well as a rather high number of multiple traumas in the craniofacial area imply a high treatment need for craniofacial tissue defects. For a successful rehabilitation of these individuals, reconstructive oral and maxillofacial surgery and prosthodontics must collaborate closely and synergistically. Besides medical and psychological findings, functional and esthetical aspects need to be taken into account. In this case report the prosthetic reconstruction of a patient with a tooth-supported telescopic defect prosthesis in the maxilla and with a multiple-unit implant-supported fixed prosthesis plus two full ceramic crowns in the mandible is shown. The prosthetic solution was indicated after maxillofacial reconstruction due to the consequence of a suicide attempt.

Callus mineralization following distraction osteogenesis of the mandible monitored by scanning acoustic microscopy (SAM).

BACKGROUND: Scanning acoustic microscopy uses ultrasound to analyse histomorphology of tissues with microscopic resolution and delivers data about physical properties of the specimen. MATERIAL AND METHODS: Bony consolidation was monitored by scanning acoustic microscopy in 12 embedded specimens of dog mandibles after distraction osteogenesis. Increasing mineralization was detected by measurements of acoustic impedance (Z). RESULTS: There was a strong correlation between acoustic impedance and time of consolidation. Measurements of the speed of sound (v) provided specific information about non-mineralized zones of the distracted area. Distribution of density in the distracted area could be reconstructed by using the measurements of acoustic impedance and speed of sound. CONCLUSION: The method seems suitable for studying bone remodelling qualitatively and quantitatively.

Possible problems of moulding the regenerate in mandibular distraction osteogenesis -- experimental aspects in a canine model.

INTRODUCTION: Moulding of the regenerate created by distraction osteogenesis has been shown clinically to be efficient and good enough so that for complex three-dimensional deformities, final adjustments by moulding the regenerate may be part of the treatment plan. This study assessed possible drawbacks of moulding a regenerate, taking into consideration compressive and tensile forces acting simultaneously on the fresh callus. METHOD: Distraction osteogenesis in 15 Beagle mandibles was performed using custom made devices which allowed for lengthening as well as for angulation. After linear distraction of 10 mm, a defined 20 degrees angulation was performed in one step. The position of the fulcrum of the device allowed simultaneously compression and stretching of the regenerated bone. Effects on bone healing were assessed after 6 and 13 weeks of consolidation respectively and compared with a control group where only linear distraction was performed. RESULTS: Radiological and histological investigations demonstrated that no significant differences between the biological behaviour of the compressed and the stretched zones of the regenerate could be found. However, there were signs showing the more critical character of the stretched area. After 6 weeks of consolidation some specimens revealed delayed ossification of the stretched zone. Under stable conditions, this delay was compensated for after 13 weeks of consolidation and complete osseous healing occurred. CONCLUSION: Under stable conditions, a fresh regenerate can be moulded to a considerable extent without permanently endangering osseous healing. Nevertheless tensile forces acting on the regenerate should be minimized to prevent damage to the new bone. This can be achieved by overdistraction prior to callus moulding or by gradually changing the vector of distraction during the lengthening process.

A faster method for 3D/2D medical image registration--a simulation study.

3D/2D patient-to-computed-tomography (CT) registration is a method to determine a transformation that maps two coordinate systems by comparing a projection image rendered from CT to a real projection image. Iterative variation of the CT's position between rendering steps finally leads to exact registration. Applications include exact patient positioning in radiation therapy, calibration of surgical robots, and pose estimation in computer-aided surgery. One of the problems associated with 3D/2D registration is the fact that finding a registration includes solving a minimization problem in six degrees of freedom (dof) in motion. This results in considerable time requirements since for each iteration step at least one volume rendering has to be computed. We show that by choosing an appropriate world coordinate system and by applying a 2D/2D registration method in each iteration step, the number of iterations can be grossly reduced from n6 to n5. Here, n is the number of discrete variations around a given coordinate. Depending on the configuration of the optimization algorithm, this reduces the total number of iterations necessary to at least 1/3 of it's original value. The method was implemented and extensively tested on simulated x-ray images of a tibia, a pelvis and a skull base. When using one projective image and a discrete full parameter space search for solving the optimization problem, average accuracy was found to be 1.0 +/- 0.6(degrees) and 4.1 +/- 1.9 (mm) for a registration in six parameters, and 1.0 +/- 0.7(degrees) and 4.2 +/- 1.6 (mm) when using the 5 + 1 dof method described in this paper. Time requirements were reduced by a factor 3.1. We conclude that this hardware-independent optimization of 3D/2D registration is a step towards increasing the acceptance of this promising method for a wide number of clinical applications.

In vivo efficacy of bone-marrow-coated polycaprolactone scaffolds for the reconstruction of orbital defects in the pig.

Alloplastic materials offer a number of advantages over bone autografts in the reconstruction of craniofacial defects. These include: lack of donor site morbidity, unlimited quantities of available material, and the possibility to conform exactly to the defect. An ideal bioresorbable material would degrade slowly, and have osteoconductive properties to allow replacement and remodeling by osseous tissue. This is seldom observed, the materials instead being replaced by fibrous tissue. Polycaprolactone (PCL), an FDA-approved bioresorbable polymer, has several properties that might make it suitable for reconstruction of craniofacial defects. The technique of fused deposition modeling (FDM) allows for the fabrication of highly reproducible bioresorbable 3D scaffolds. The nature of the fully interconnected pore network might enhance vascular ingrowth and osteoconductive properties. It was hypothesized that coating the scaffolds in bone marrow might enhance bone formation due to the osteoinductive nature of the bone-marrow mesenchymal cells. This study aimed to test these hypotheses in the pig model. Defects measuring 2 x 2 cm were surgically created in each orbit of eight Yorkshire pigs. The orbits were divided into three groups: Group 1 (n=4), no reconstruction (control); Group 2 (n=6), reconstruction with no coated PCL scaffolds; and Group 3 (n=6) reconstruction with bone-marrow-coated PCL scaffolds. The results were evaluated at 3 months by histological and histomorphometric analyses. The defects in Group 1 were covered with fibrous scar tissue. The shape of the reconstructed area was insufficient. The defects in Groups 2 and 3 were reconstructed correctly. In Group 2 the noncoated scaffolds showed 4.5% of new bone formation compared with 14.1% in Group 3, which is statistically significant (p<0.05). The entirely interconnected 3D polycaprolactone scaffold seems to be a promising material. It induces the bone ingrowth required for reconstructing craniofacial and orbital defects. Further long-term evaluations of these PCL scaffolds must be made in order to confirm these conclusions.

Maxillofacial reconstruction with prefabricated osseous free flaps: a 3-year experience with 24 patients.

Between January of 1998 and May of 2002, 25 prefabricated osseous free flaps (23 fibula and two iliac crest flaps) were transferred in 24 patients to repair maxillary (six flaps) or mandibular (eight flaps) defects after tumor resection, severe maxillary (four flaps) or mandibular (one flap) atrophy (Cawood VI), maxillary (one flap) or mandibular (three flaps) defects after gunshot injury, and maxillary (two flaps) defects after traffic accidents. Prefabrication included insertion of dental implants, positioned with a drilling template in a preplanned position, and split-thickness grafting. Drilling template construction was based on the prosthetic planning. The template determined the position of the implants and the site and angulation of osteotomies, if necessary. The mean delay between prefabrication and flap transfer was 6 weeks (range, 4 to 8 weeks). While the flap was harvested, a bar construction with overdentures was mounted onto the implants. The overdentures were used as an occlusal key for exact three-dimensional positioning of the graft within the defect. The bar construction also helped to stabilize the horseshoe shape of the graft. The follow-up period ranged from 2 months to 4 years (mean, 21 months), during which time two total and three partial flap losses occurred. One total loss was due to thrombosis of the flap veins during the delay period, whereas the other total loss was caused by spasm of the peroneal artery. Two partial losses were due to oversegmentation of the flaps with necrosis of the distal fragment, whereas one partial loss was caused by disruption of the vessel from the distal part. Of the 90 implants that were inserted into the prefabricated flaps during the study period, 10 were lost in conjunction with flap failure; of the remaining 80 implants, four were lost during the observation period, for a success rate of 95 percent. Flap prefabrication based on prosthetic planning offers a powerful tool for various reconstructive problems in the maxillofacial area. Although it involves a two-stage procedure, the time for complete rehabilitation is shorter than with conventional procedures.

Computer-assisted secondary reconstruction of unilateral posttraumatic orbital deformity.

Until now, computer-assisted surgery has not been practiced as part of the surgical routine of posttraumatic orbital reconstruction. The purpose of this study was to investigate the use of a navigation system for computer-assisted preoperative planning with virtual reconstruction to obtain symmetry of the orbits and intraoperative control of virtual contours in comparison with the clinically achieved surgical results. A further objective of the computer-assisted orbital analysis was to use an ideal measurement for the two-dimensional and three-dimensional changes following orbital reconstruction and to check the equality of the postoperative values for the affected orbits in comparison with those of the unaffected sides. Patients with unilateral posttraumatic orbital defects (n = 18) underwent computer-assisted surgery and preoperative planning using a spiral computed tomography database. Surgical procedures were preplanned with virtual correction by mirroring an individually defined three-dimensional segment from the unaffected side onto the deformed side, creating an ideal unilateral reconstruction. These computer-models were intraoperatively used as virtual templates to navigate the preplanned contours and the globe projection using the Stryker-Leibinger navigation system. Individual noninvasive registration with an overall inaccuracy of approximately 1 mm was achieved by using a maxillary occlusal splint with four markers. The mirroring of the unaffected side allowed an ideal virtual reconstruction. A mean decrease in enlarged orbital volume of 4.0 (SD +/- 1.9) cm was achieved, as was a mean increase in the sagittal globe projection of 5.88 (SD +/- 2.98) mm. With a paired Student test, the decrease between the preoperative and postoperative differences of the affected and unaffected sides was proved significant for orbital volume, globe projection, and computed tomography-based Hertel scale changes (p < 0.01). In 15 of 18 cases, simultaneous malar bone advancement resulted primarily in an additional increase in orbital volume before intraorbital augmentation with calvarial split-bone grafts could be performed. Intraorbital bony augmentation included one (n = 1), two (n = 7), three (n = 8), and all four (n = 2) orbital walls. Computer-assisted preoperative planning enables the surgeon to predict reconstructive surgical steps before the operation. Highly vulnerable structures such as the optic nerve can be detected and avoided intraoperatively, and virtually preplanned bone graft positions and/or orbital frame contours can be checked. Computer-assisted preoperative planning and surgery thus advance the difficult surgical field of orbital reconstruction, particularly through a greater exploitation of radiologic information without additional radiation to the patient.

The sphenozygomatic suture as a key site for osteosynthesis of the orbitozygomatic complex in panfacial fractures: a biomechanical study in human cadavers based on clinical practice.

The aims of this study were to determine the forces required for fracturing the intact orbitozygomatic complex and to evaluate the strength of the orbitozygomatic complex-fixation, especially with regard to the sphenozygomatic suture as a fixation point. In severe midfacial and panfacial fractures, the sphenozygomatic suture is routinely used in the authors' practice as a key site for fixation of the orbitozygomatic complex, thus establishing a stable outer frame as a basis for subsequent reconstruction. However, this has never been formally described, nor has it been biomechanically tested. Eight human cadaver heads were subjected to forces applied in a standard fashion to the orbitozygomatic complex on both sides (n = 16) using a servohydraulic testing machine. The force required to break the intact orbitozygomatic complex was measured on both sides. Subsequently, fracture patterns were noted and each orbitozygomatic complex (n = 16) was assigned to one of four groups: four-point fixation (zygomatic arch, frontozygomatic suture, infraorbital rim, zygomaticomaxillary buttress) using a 1.3/2.0-mm titanium system (group 1) and a 2.0-mm bioresorbable system (group 3); or three-point fixation (zygomatic arch, frontozygomatic suture, sphenozygomatic suture) using 1.3/2.0-mm titanium system (group 2) and a 2.0-mm bioresorbable system (group 4). Forces for failure of the constructs were measured. The force for failure of the intact orbitozygomatic complex was 1826 +/- 852 N. The mean force required for failure of the reconstructed orbitozygomatic complex was 504 +/- 178 N for group 1, 620 +/- 304 N for group 2, 93 +/- 22 N for group 3, and 133 +/- 31 N for group 4. The titanium constructs provided 27.7 percent (four-point fixation) and 31.7 percent (three-point fixation) of the intact breaking strength of the orbitozygomatic complex, which was significantly higher (p < 0.05) compared with 5.4 percent (four-point fixation) and 7.7 percent (four-point fixation) for the bioresorbable system. Plate bending (91 percent) was the primary cause for failure in the titanium plating system, whereas plate and screw breakage (57 percent) was responsible for failure of the resorbable system. The fixation of the sphenozygomatic suture was a key site in the fixation of the orbitozygomatic complex, which could be demonstrated with superior results in the three-point fixation group compared with the four-point fixation group. The bioresorbable system showed the lowest values in this cadaver study. Further experimental and clinical studies might determine whether the bioresorbable materials are sufficient for the treatment of complex fractures of the orbitozygomatic complex.

Prefabricated fibular flaps for reconstruction of defects of the maxillofacial skeleton: planning, technique, and long-term experience.

Reconstruction of complex defects involving the maxilla or mandible often requires transfer of free vascularized tissue. In the conventional approach, a flap is transferred to provide vital tissue, and subsequent shaping and debulking are required. The authors present their experience with prefabrication of vascularized fibular flaps. Since 1999, 48 prefabricated flaps have been used to reconstruct 28 maxillary and 20 mandibular defects. The technique involves two surgical steps (prefabrication and flap transfer) and requires accurate planning, done with a solid model of the skull. Correct positioning of the prefabricated flap is accomplished by using the occlusion as a guide. Planning includes fabrication of a provisional prosthesis that is fixed to the flap with implants. Putting the prosthesis into occlusion determines the position of the flap.

Classification of orbital morphology for decompression surgery in Graves' orbitopathy: two-dimensional versus three-dimensional orbital parameters.

AIM: Three-dimensional (3D) CT reconstruction of the bony orbit for accurate measurement and classification of the complex orbital morphology may not be suitable for daily practice. We present an easily measurable two-dimensional (2D) reference dataset of the bony orbit for study of individual orbital morphology prior to decompression surgery in Graves' orbitopathy. METHODS: CT images of 70 European adults (140 orbits) with unaffected orbits were included. On axial views, the following orbital dimensions were assessed: orbital length (OL), globe length (GL), GL/OL ratio and cone angle. Postprocessed CT data were required to measure the corresponding 3D orbital parameters. The 2D and 3D orbital parameters were correlated. RESULTS: The 2D orbital parameters were significantly correlated to the corresponding 3D parameters (significant at the 0.01 level). The average GL was 25 mm (SD±1.0), the average OL was 42 mm (SD±2.0) and the average GL/OL ratio was 0.6 (SD±0.03). The posterior cone angle was, on average, 50.2° (SD±4.1). Three orbital sizes were classified: short (OL≤40 mm), medium (OL>40 to <45 mm) and large (OL≥45 mm). CONCLUSIONS: We present easily measurable reference data for the orbit that can be used for preoperative study and classification of individual orbital morphology. A short and shallow orbit may require a different decompression technique than a large and deep orbit. Prospective clinical trials are needed to demonstrate how individual orbital morphology affects the outcome of decompression surgery.

Importance of patient-specific intraoperative guides in complex maxillofacial reconstruction.

BACKGROUND: Conventional maxillofacial reconstruction often leads to suboptimal results due to inaccurate planning or surgical difficulties in adjusting a free flap and osteosynthesis plates into a three-dimensional defect. OBJECTIVES: To justify the importance of patient-specific intraoperative guides in complex maxillofacial reconstruction. CLINICAL EXAMPLE: A 40-year old patient underwent a left hemimaxillectomy for an adenoid cystic carcinoma of the palate. Six years later, massive recurrence required radical resection of the left orbit and reconstruction with cranial bone grafts and a free latissimus dorsi flap. Postoperative radiotherapy resulted in local osteoradionecrosis. Surgical revision and restoration of the maxillary defect with a prefabricated fibula flap was performed. The authors provide ample information on the application of computer-aided design and manufacturing (CAD-CAM) and rapid prototyping at each reconstructive step. DISCUSSION: Stereolithographic models enable simulation of the resective and reconstructive phases, prebending of reconstruction plates and fabrication of surgical guides. CONCLUSIONS: Optimal restitution of complex maxillofacial defects requires meticulous planning of the surgical and prosthetic phases and effective transfer of the plan to the operating room through patient specific guides. CAD-CAM technology and stereolithographic models represent an effective strategy to achieve this. Improved patient outcomes and intraoperative efficiency certainly offset the inherent increase in costs.