Heike Huempfner-Hierl

Results of a prospective anthropometric and functional study about aesthetics and nasal respiration after secondary rhinoplasty in cleft lip and palate patients.

In contrast to the multitude of investigations regarding aesthetic changes in nasal surgery, few data are available concerning nasal function. This is especially important for cleft patients with a compromised nasal respiration. In this prospective study, 68 cleft patients, who underwent nasal surgery, were evaluated concerning aesthetic and respiratory outcome. To assess nasal respiration, active anterior rhinomanometry, rhinoresistometry, and acoustic rhinometry were performed preoperatively and 6 months postoperatively (without and with nasal decongestion, according to international standards). For analyzing the changes in aesthetic parameters, photographs from 3 directions, which were taken preoperatively and at least 6 months postoperatively, were compared. Thus, 57 angles and relations of lines were created out of 54 anthropometric points. The Wilcoxon test was used to compare preoperative and postoperative data (P < 0.05). Regarding aesthetic outcome, a significant improvement in many parameters was seen. The noses postoperatively proved to be significantly narrower and more symmetric and showed a better projection. Although analysis of functional respiratory data showed a significant increase in nasal volume, no change in nasal airflow and hydraulic diameter could be found. Whereas aesthetic improvement of the cleft nose is a goal, which can be achieved regularly, nasal respiration still seems to be a challenge in cleft patients. This study highlights the necessity of taking functional data to learn more about the effects of surgery. Objective methods to assess nasal respiratory function are important for planning and performing nasal surgery and are a means of quality control.

Transient finite element analysis of a traumatic fracture of the zygomatic bone caused by a head collision

Midfacial fractures rank first concerning maxillofacial traumatology. Collisions of two heads or head to object are the main causes for these fractures. An investigation based on a transient simulation using the finite element method was performed. A biomechanical head model was created and tested. A transient collision of two heads was simulated. The results were compared to a typical real patient case. This comparison revealed an identical fracture pattern, which can be interpreted as a clinical match of the simulation. The results of this study show the validity of biomechanical investigations, which may serve as a method to better understand maxillofacial fracture patterns. These results will be used for the optimization of fracture therapy or trauma prevention in the future.

Morphologic Comparison of Preformed Orbital Meshes

PURPOSE Preformed orbital titanium meshes have been introduced to improve outcomes in the treatment of orbital wall fractures. This study evaluated the geometry of different commercially available orbital meshes and compared them with an average human orbit. MATERIALS AND METHODS Seven commercially available preformed orbital meshes were scanned using an optical scanner. For comparison, an average orbit was generated from 113 computed tomographic scans of unaffected orbits. Meshes and the average orbit were compared by registration and the calculation of congruence. RESULTS All meshes showed a high similarity within a ±1.5-mm deviation corridor. Major differences were seen in the slope between the orbital floor and the medial wall and in the upturning toward the lateral orbital rim. CONCLUSION Preformed orbital meshes conform highly to an average orbit, but differ in size and geometry. Using special software, the best fitting mesh could be chosen preoperatively to improve surgical outcome if its geometry were published.

Blunt forehead trauma and optic canal involvement: finite element analysis of anterior skull base and orbit on causes of vision impairment

Background Clinical studies report on vision impairment after blunt frontal head trauma. A possible cause is damage to the optic nerve bundle within the optic canal due to microfractures of the anterior skull base leading to indirect traumatic optic neuropathy. Methods A finite element study simulating impact forces on the paramedian forehead in different grades was initiated. The set-up consisted of a high-resolution skull model with about 740 000 elements, a blunt impactor and was solved in a transient time-dependent simulation. Individual bone material parameters were calculated for each volume element to increase realism. Results Results showed stress propagation from the frontal impact towards the optic foramen and the chiasm even at low-force fist-like impacts. Higher impacts produced stress patterns corresponding to typical fracture patterns of the anterior skull base including the optic canal. Transient simulation discerned two stress peaks equalling oscillation. Conclusions It can be concluded that even comparatively low stresses and oscillation in the optic foramen may cause micro damage undiscerned by CT or MRI explaining consecutive vision loss. Higher impacts lead to typical comminuted fractures, which may affect the integrity of the optic canal. Finite element simulation can be effectively used in studying head trauma and its clinical consequences.

Biomechanical mechanisms of orbital wall fractures – A transient finite element analysis

As the biomechanical mechanisms of orbital wall fractures are still under research, three different fracture mechanisms were tested in a finite element based investigation. In contrast to earlier studies, a finer skeletal model and a transient dynamic simulation were used to test pure hydraulic, pure buckling and a mixed force transmission. Results showed that each set-up led to different orbital fracture patterns, which correlate well with clinical findings. Therefore the conclusion is that different mechanisms may act together explaining the variety of clinical fracture situations. Biomechanical testing has proven to be appropriate in answering questions regarding fracture mechanisms.

Biomechanical investigation of naso-orbitoethmoid trauma by finite element analysis

Naso-orbitoethmoid fractures account for 5% of all facial fractures. We used data derived from a white 34-year-old man to make a transient dynamic finite element model, which consisted of about 740 000 elements, to simulate fist-like impacts to this anatomically complex area. Finite element analysis showed a pattern of von Mises stresses beyond the yield criterion of bone that corresponded with fractures commonly seen clinically. Finite element models can be used to simulate injuries to the human skull, and provide information about the pathogenesis of different types of fracture.

Biomechanical investigation of the supraorbital arch - a transient FEA study on the impact of physical blows.

IntroductionAs fractures of the supraorbital region are far less common than midfacial or orbital fractures, a study was initiated to investigate whether fist blows could lead to fractures similar to those often seen in the midface.MethodsA detailed skull model and an impactor resembling a fist were created and a fist blow to the supraorbital region was simulated. A transient finite element analysis was carried out to calculate von Mises stresses, peak force, and impact time.ResultsWithin the contact zone of skull and impactor critical stress values could be seen which lay at the lower yield border for potential fractures. A second much lower stress zone was depicted in the anterior-medial orbital roof.ConclusionsIn this simulation a fist punch, which could generate distinct fractures in the midface and naso-ethmoid-orbital region, would only reach the limits of a small fracture in the supraorbital region. The reason is seen in the strong bony architecture. Much higher forces are needed to create severe trauma in the upper face which is supported by clinical findings. Finite element analysis is the method of choice to investigate the impact of trauma on the human skeleton.

Template-Based Orbital Wall Fracture Treatment Using Statistical Shape Analysis

PURPOSE Aim of this study was to investigate whether a mold generated from a statistical shape model of the orbit could be generated to provide a cost-efficient means for the treatment of orbital fractures. MATERIALS AND METHODS A statistical shape model was created from 131 computed tomographic (CT) scans of unaffected adult middle European human orbits. To generate the model, CT scans were segmented in Brainlab software, preregistered using anatomic landmarks, trimmed to an identical size, and definitely registered. Then, the model was created using the global master algorithm. Based on this model, a mold consisting of a male part and a female part was constructed and printed using a rapid prototyping technique. RESULTS A statistical shape model of the human orbit was generated from 125 CT scans. Six scans (4.5%) presented major anatomic deviations and were discarded. A solid mold based on this model was printed. Using this mold, flat titanium mesh could be successfully deformed to serve as an orbital implant. CONCLUSION A mold based on the statistical orbital shape could serve as a cost-effective means for the treatment of orbital fractures. It allows the anatomic preformation of titanium or resorbable implant material for orbital reconstruction. Because these materials could be cut from larger sheets, the use of a mold would be a cost-effective treatment alternative.

Rare anatomical variation of the brachiocephalic trunk encountered in tracheostomy

Tracheostomy is a common procedure in head and neck surgery and emergency medicine to secure a patent airway. Surgeons should always be aware of anatomical variants of the branches of the aortic arch, which could lead to life-threatening complications. Open tracheostomy is the safest emergency procedure.

Maxillofacial fractures and craniocerebral injuries – stress propagation from face to neurocranium in a finite element analysis

BackgroundSevere facial trauma is often associated with intracerebral injuries. So it seemed to be of interest to study stress propagation from face to neurocranium after a fistlike impact on the facial skull in a finite element analysis.MethodsA finite element model of the human skull without mandible consisting of nearly 740,000 tetrahedrons was built. Fistlike impacts on the infraorbital rim, the nasoorbitoethmoid region, and the supraorbital arch were simulated and stress propagations were depicted in a time-dependent display.ResultsFinite element simulation revealed von Mises stresses beyond the yield criterion of facial bone at the site of impacts and propagation of stresses in considerable amount towards skull base in the scenario of the fistlike impact on the infraorbital rim and on the nasoorbitoethmoid region. When impact was given on the supraorbital arch stresses seemed to be absorbed.ConclusionsAs patients presenting with facial fractures have a risk for craniocerebral injuries attention should be paid to this and the indication for a CT-scan should be put widely. Efforts have to be made to generate more precise finite element models for a better comprehension of craniofacial and brain injury.AbstractHintergrundFrakturen des Gesichtsschädels gehen häufig mit intrakraniellen Verletzungen einher. Deshalb erschien es interessant, die Weiterleitung und Verteilung von Spannungen, wie sie bei einem Faustschlag auftreten, vom Gesichtsschädel zum Hirnschädel in einer Finite Elemente Analyse zu untersuchen.MethodenEin Finite Elemente Modell des menschlichen Schädels ohne Unterkiefer, welches aus zirka 740,000 tetraedrischen Volumeneinheiten bestand, wurde entwickelt. Die Einwirkung einer Kraft, die einem Faustschlag entsprach, auf den Infraorbitalrand, die Nasoorbitoethmoidregion und den supraorbitalen Bogen wurden simuliert. Die Weiterleitung der Spannungen wurde in einem zeitlichen Verlauf dargestellt.ErgebnisseDie Finite Elemente Simulation zeigte von Mises-Spannungen oberhalb des Wertes, ab dem Gesichtsschädelknochen frakturieren, im Bereich der Krafteinleitung und Fortleitung von Spannungen in Richtung auf die Schädelbasis in beachtlicher Höhe bei Auftreffen des Impaktors auf den Infraorbitalrand oder die Nasoorbitoethmoidregion. Bei Auftreffen der Kraft supraorbital scheinen die Spannungen absorbiert zu werden.SchlussfolgerungenDa Patienten mit Gesichtsschädelfrakturen ein Risiko für Schädel-Hirn-Traumata aufweisen, sollte eine entsprechende Überwachung erfolgen. Die Indikation für CT-Untersuchungen sollte großzügig gestellt werden. Genauere Finite Elemente-Modelle sind zum besseren Verständnis kraniofazialer Frakturen und Hirnverletzungen notwendig.