Jutta Markwardt

Analysis of Complications after Reconstruction of Bone Defects Involving Complete Mandibular Resection Using Finite Element Modelling

Background: In a retrospective study, risk factors for complications after the bridging of mandibular defects using reconstruction plates were reviewed. Especially the loosening of the plate-screw-mandible complex should be analyzed with a finite element model in order to reduce plate complications in future. Patients and Methods: We examined 60 patients who underwent a treatment with reconstruction plates after tumor resection during a period of 10 years. The problem of screw loosening was additionally reviewed by means of a finite element study, and a model for the loosening process was developed. Results: Our postoperative examination showed that 26 patients suffered from complications that required an early removal of the plate. These complications were oral or extraoral plate exposures, the looseness of screws with or without plate displacement, and plate fractures. Thereby, we noticed that maxillary and mandibular areas of opposing teeth, the size of the mandible defect, and the crossing of the orofacial midline are all risk factors for plate complications. On the basis of the finite element model, a modified arrangement of the screws was derived. Hence, a new type of resection plate was established. Conclusions: By repositioning the screw holes along the long axis of the plate, the transition from tensile force to torque force of the screws in the screw-plate-bone complex can be minimized. Thereby, the complication of screw loosening will be considerably reduced.

PREFABRICATED BONY RADIAL FOREARM FLAP FOR SECONDARY MANDIBLE RECONSTRUCTION AFTER RADIOCHEMOTHERAPY

Primary reconstruction of the mandible is the golden standard of surgical treatment after ablative tumor surgery. Many different microvascular bone grafts are used to reduce wound healing complications at the severely compromised recipient site. The loss of primary grafts due to radiotherapy or osteoradionecrosis can make secondary mandibular reconstruction necessary. To address this problem, we developed the technique of the prefabrication of a radial forearm flap with cancellous bone. The aims were to establish these techniques into the clinical routine and to create a safe and reliable flap with low donor site morbidity.

Experimental study on the behavior of primary human osteoblasts on laser-cused pure titanium surfaces

Mandibular tumor resection can lead to a mandibular segmental defect. LaserCUSING® is used to produce a mandibular implant, designed to be identical to the shape of the mandibular defect. Novel microrough surfaces result from this generative technology. In the current study, the behavior of human osteoblasts on untreated laser-cused titanium specimens or on specimens conditioned with different blasting agents was analyzed. The conditioning of these specimens resulted in surfaces with graded roughness. White light confocal microscopy and single-cell force spectroscopy were used to characterize the surface of the specimens and to quantify the initial adhesion of primary human osteoblasts to the specimens, respectively. Furthermore, cell growth, viability, apoptosis as well as mineralization of the specimens were analyzed over a time-period of 2 months. Compared to specimens that were treated with blasting agents, untreated specimens had the highest surface roughness. Quantitative SCFS measurements demonstrated that the adhesion of human primary osteoblasts was the highest on these specimens. Additionally, the untreated specimens allowed the highest number of osteoblasts to colonize. Mineralization studies showed increasing calcium and phosphor elemental composition for all specimen series. It can be concluded that untreated laser-cused titanium specimens are superior to promote the initial adhesion and subsequent colonization by osteoblast cells.

Clinical Test of Masticatory Efficacy in Patients with Maxillary/Mandibular Defects Due to Tumors

Background: The goal of the study was to evaluate the masticatory efficacy in patients who had been provided with resection prostheses after tumor removal in the maxillary/ mandibular region. These patients complained of impairment of masticatory function. Patients and Methods: 3 groups of patients were compared under clinical-experimental conditions. A uniform chewing material was masticated by the participants under standardized conditions. A sieving procedure was used to evaluate the masticatory efficacy. Analysis of the particle sizes and particle masses obtained was performed with the aid of computers. Results: The results showed that the masticatory efficacy of the patients with resection prostheses was the lowest of the 3 groups compared. The number of existing supporting zones and the location of the defect were found to be important influencing factors. Recording of the dietary habits of all patients was performed using a standardized dietary questionnaire. These data were analyzed using the corresponding software of the German Nutrition Society. With regard to the patients with resection prostheses, it was revealed that they often switched to food that did not require mastication. Conclusions: A nutritional guideline for patients with resection prostheses was developed, which is available for downloading free of charge on the Internet.

One vs. two piece customized implants to reconstruct mandibular continuity defects: A preliminary study in pig cadavers

OBJECTIVES The reconstruction of mandibular continuity defects by bridging plates often leads to complications. Customized mandibular implants might be an alternative option. In the present study, the stability at the bone-implant-interface of customized two-piece implants was compared to one-piece implants. METHODS Thirty pig mandibles were randomly divided into three groups. One group (A) was left untreated and served as reference. In groups B and C, a continuity defect was created in the left mandibular side. The defects were reconstructed by customized pure titanium implants, manufactured using the LaserCUSING(®) technology. Group B received a one-piece implant; in group C a two-piece implant was inserted to reconstruct the continuity defect. The bonding strength was examined statically and dynamically under standardized conditions. Digital Image Correlation was used for distortion measurement. Different dynamic measurements were performed for orientation purposes. RESULTS The highest bonding strength was measured for the reference group. The two-piece implant showed an increased bonding strength when compared to the one-piece design. In all pig mandibles treated with individual implants a fracture occurred on the non-operated side. This indicates a high primary stability of the bone-implant-interface. CONCLUSION The two-piece individual mandibular implant manufactured by LaserCUSING(®) technology should be further analyzed in future studies.

Experimental findings on customized mandibular implants in Göttingen minipigs – A pilot study

Reconstructing continuity defects of the mandible is still challenging for surgeons. The currently applied conventional titanium bridging plates have considerable rates of complications. Now, a new technology enables an individual shape-identical creation of a mandibular implant in a form-board design by the method of LaserCUSING using pure titanium. This technology has been successfully performed in previous examinations to individually reconstruct mandibular continuity defects. This pilot study evaluated the surgical procedure in 10 female Göttingen mini pigs. First, a computed tomography scan from a mini pig cranium was performed. A three-dimensional model of the mandible was designed by data conversion. Based on the data, a customized mandibular implant resembling the natural shape was virtually created and manufactured. Then, a continuity defect of the left mandible was created in a standardized way. The implants were inserted into the defect and the wounds were allowed to heal for 21, 35, 56 and 180 days. During the healing period, no signs of inflammation or infection were observed. After the sacrifice of the minipigs the mandibles were resected. Histological microsections using Donaths sawing and grinding technique were manufactured and stained with Masson Goldner trichrome staining. The histomorphological results showed a pronounced ossification at the outer and inner surface of the implants. This animal study describes a promising approach to optimize customized implants for the application in humans.

Evaluation of selected speech parameters after prosthesis supply in patients with maxillary or mandibular defects.

Background: Ablative surgery of oropharyngeal tumors frequently leads to defects in the speech organs, resulting in impairment of speech up to the point of unintelligibility. The aim of the present study was the assessment of selected parameters of speech with and without resection prostheses. Patients and Methods: The speech sounds of 22 patients suffering from maxillary and mandibular defects were recorded using a digital audio tape (DAT) recorder with and without resection prostheses. Evaluation of the resonance and the production of the sounds /s/, /sch/, and /ch/ was performed by 2 experienced speech therapists. Additionally, the patients completed a non-standardized questionnaire containing a linguistic self-assessment. Results: After prosthesis supply, the number of patients with rhinophonia aperta decreased from 7 to 2 while the number of patients with intelligible speech increased from 2 to 20. Correct production of the sounds /s/, /sch/, and /ch/ increased from 2 to 13 patients. A significant improvement of the evaluated parameters could be observed only in patients with maxillary defects. The linguistic self-assessment showed a higher satisfaction in patients with maxillary defects. Conclusion: In patients with maxillary defects due to ablative tumor surgery, an increase in speech performance and intelligibility is possible by supplying resection prostheses.

[Computation and experimental examination of an implant structure made by a fibre-reinforced building method for the bypass of continuity defects of the mandible].

Zusammenfassung Eine Unterkieferteilresektion muss nicht selten im Rahmen der chirurgischen Entfernung von Tumoren im Unterkiefer-, Mundboden- und Zungenbereich bzw. mit Substanzverlust einhergehenden Unterkieferfrakturen, gutartigen Knochenläsionen und ausgedehnten, schwer zu beherrschenden Knochengewebsentzündungen durchgeführt werden. Die primäre Rekonstruktion des Unterkiefers ist nach einer Teilresektion mit Kontinuitätsverlust vorwiegend aus funktionellen und auch aus ästhetischen Gründen notwendig. Derzeit werden die Unterkieferkontinuitätsdefekte häufig mit metallischen Rekonstruktionsplatten überbrückt, um die mastikatorische Funktion des Unterkiefers temporär oder endgültig wieder herzustellen. Funktionelle sowie ästhetische Nachteile ergeben sich bei der Anwendung derartiger Platten durch einen hohen Steifigkeitssprung zwischen Rekonstruktionsplatte und Knochen sowie deren wenig individuell gestaltetes Design. Der Einsatz von biokompatiblem, kohlenstofffaserverstärktem Polyetheretherketon (CF-PEEK) erlaubt die Entwicklung einer dem Unterkiefer kontur- und steifigkeitsangepassten Tragstruktur. Für die beanspruchungsgerechte Auslegung und den Test einer CF-PEEK-Tragbandage bieten sich die Finite-Elemente-Methode sowie die Anwendung optischer Methoden wie etwa das Grauwertkorrelationsverfahren an. Das Deformationsverhalten wurde für verschiedenartige Osteosynthesekonfigurationen an einem Modellkiefer vergleichend untersucht. Die Berechnungen und Tests des defektüberbrückten Modellkiefers zeigen beim Einsatz der neuartigen CF-PEEK-Tragbandage im Vergleich zur Verwendung herkömmlicher Titan-Osteosyntheseplatten ein dem natürlichen Unterkiefer wesentlich besser angepasstes mechanisches Verhalten. Abstract A partial resection of the lower jaw often has to be carried out in the context of the surgical removal of tumours in the lower jaw, mouth and tongue-floor space and lower jaw fractures with loss of substance, benign bone lesions and extensive difficult inflammation of bone tissue, respectively. The primary reconstruction of the lower jaw after partial resection with loss of continuity is mainly important for functional and aesthetic reasons. The defects of lower jaw continuity are often bridged with metal plates to reconstruct the masticatory function of the lower jaw, temporarily or permanently. Functional as well as aesthetic disadvantages arise in the case of the application of such plates as a result of a high stiffness jump between reconstruction plate and bone and their insufficiently individual design. The employment of biocompatible, carbon-fibre-reinforced Polyetheretherketon (CF-PEEK) permits the development of a geometry- and stiffness-adapted carrying structure for the mandible. For the demand-adapted dimensioning and the test of a CF-PEEK bandage, the application of optical methods, such as the grey value correlation method, is suited as well as numeric methods, such as the finite element method. In an initial analysis of deformation behaviour, the various osteosynthesis configurations are comparatively investigated on a model jaw. The calculations and tests of the lower jaw model show that the use of the new CF-PEEK bandage compared to the use of conventional titanium osteosynthesis plates shows a mechanical behaviour which is much better adapted to the natural lower jaw.A partial resection of the lower jaw often has to be carried out in the context of the surgical removal of tumours in the lower jaw, mouth and tongue-floor space and lower jaw fractures with loss of substance, benign bone lesions and extensive difficult inflammation of bone tissue, respectively. The primary reconstruction of the lower jaw after partial resection with loss of continuity is mainly important for functional and aesthetic reasons. The defects of lower jaw continuity are often bridged with metal plates to reconstruct the masticatory function of the lower jaw, temporarily or permanently. Functional as well as aesthetic disadvantages arise in the case of the application of such plates as a result of a high stiffness jump between reconstruction plate and bone and their insufficiently individual design. The employment of biocompatible, carbon-fibre-reinforced Polyetheretherketon (CF-PEEK) permits the development of a geometry- and stiffness-adapted carrying structure for the mandible. For the demand-adapted dimensioning and the test of a CF-PEEK bandage, the application of optical methods, such as the grey value correlation method, is suited as well as numeric methods, such as the finite element method. In an initial analysis of deformation behaviour, the various osteosynthesis configurations are comparatively investigated on a model jaw. The calculations and tests of the lower jaw model show that the use of the new CF-PEEK bandage compared to the use of conventional titanium osteosynthesis plates shows a mechanical behaviour which is much better adapted to the natural lower jaw.

Contour identical implants to bridge mandibular continuity defects - individually generated by LaserCUSING ® - A feasibility study in animal cadavers

BackgroundAblative tumor surgery often results in continuity defects of the mandible. When an immediate reconstruction using autologous bone grafts is not possible the bridging of the defects with a variety of bridging plates might be achieved. However, those bridging plates have the risk of plate fractures or exposure. Customized titanium implants manufactured using CAD/CAM and the LaserCUSING® technique might be an alternative.MethodsIn the present study, computed tomographies (CT) of porcine cadaver mandibles were generated and transferred into DICOM data. Following, different continuity defects were surgically created in the mandibles. Based on the DICOM data customized titanium implants were manufactured using CAD/CAM procedures and the LaserCUSING® technique. The implants were fixed to the remaining stumps with screws. Subsequently, the accuracy of the reconstructed mandibles was tested using plaster casts.ResultsThe workflow from the CT to the application of the customized implants was proved to be practicable. Furthermore, a stable fixation of the customized implant to the remaining stumps could be achieved. The control of the accuracy showed no frictions or obstacles.ConclusionThe customized titanium implant seems to be a promising approach to bridge continuity defects of the mandible whenever an immediate reconstruction with autologous bone is not possible.