S. Weihe

Synthesis of CAD/CAM, robotics and biomaterial implant fabrication: single-step reconstruction in computer aided frontotemporal bone resection

The preoperative manufacturing of individual skull implants, developed by an interdisciplinary research group at Ruhr-University Bochum, is based on the use of titanium as the most common material for implants at present. Using the existing technology for materials that can be milled or moulded, customized implants may be manufactured as well. The goal of the study was to examine biodegradable materials and to evaluate the practicability of intraoperative instrument navigation and robotics. Data acquisition of an adult sheeps head was performed with helical computer tomography (CT). The data were transferred onto a computer aided design/computer aided manufacturing system (CAD/CAM system), and two complex defects in the frontotemporal skull were designed. Standard individual titanium implants were milled for both of the defects. Additionally, for one of the defects a resection template, as well as a mould for the biodegradable poly(D,L-lactide) (PDLLA) implant, were fabricated by the CAD/CAM system. A surgeon carried out the first bone resection (#1) for the prefabricated titanium implant using the resection template and an oscillating saw. The robot system Stäubli RX90CR, modified for clinical use, carried out the other resection (#2). Both titanium implants and the PDLLA implant were inserted in their respective defects to compare the precision of their fit. A critical comparison of both implant materials and both resection types shows that fabrication of a PDLLA implant and robot resection are already possible. At present, the titanium implant and resection using a template are more convincing due to the higher precision and practicability.

Thiel embalming technique: a valuable method for teaching oral surgery and implantology.

BACKGROUND Because of its high requirements on surgical experience and the need of complete understanding of the anatomy, oral surgery and especially implantology belong to the most demanding procedures in dentistry. Therefore, hands-on courses for oral surgery and implantology are considered a prerequisite to prepare for clinical practice. To achieve teaching conditions as realistic as possible, we used a novel human cadaver embalming method enabling tissue dissection comparable with the living body. METHODS Thirty cadavers which were offered by the Institute of Anatomy for the purpose of running oral surgery and implantology courses were embalmed in the technique described by Thiel. On each cadaver, dissection of soft and hard tissue and implantological procedures were performed according to a structured protocol by each course participant. The conservation of fine anatomical structures and the suitability of the embalmed tissue for dissecting, drilling, and suturing were observed and photographically documented. RESULTS By means of the Thiel embalming technique, oral surgery and implantological procedures could be performed under realistic conditions similar to the living body. Due to the conservation procedure, preparations could be carried out without any time limit, always maintaining the same high quality of the tissue. The maxillary sinus membrane, mucosa, bone, and nerves could be exposed and allowed dissecting, drilling, and suturing even after weeks like fresh specimens. CONCLUSION The Thiel embalming method is a unique technique which is ideally suited to practice and teach oral surgery and implantology on human material.

Management of cranial and craniofacial bone defects with prefabricated individual titanium implants: follow-up and evaluation of 166 patients with 169 titanium implants from 1994 to 2000

AbstractObjective The TICC (Tomography, Image processing, CAD, CAM) processing chain developed at the Ruhr-University Bochum in Germany has already been established since several years for the reconstruction of large pre-existing posttraumatic skull defects with individual prefabricated implants made of pure titanium. So far, more than 500 titanium implants have been inserted with great success at more than 60 clinical centres worldwide. The aim of our study was to evaluate all implants inserted between 1994 and 2000. Materials and Methods The study describes the clinical experience with 166 patients receiving 169 skull implants between 1994 and 2000. All 169 implants were measured and categorized in the CAD system in terms of size and anatomical localization. The surgical and radiological reports of the patients were evaluated. Sixty patients operated at the university hospital in Bochum and nearby were clinically reviewed describing scars, position of the implants and cosmetic results. Questionnaires of 131 patients were analyzed regarding the postoperative quality of life distinctly. Results The study shows constantly good to excellent results intraoperatively as well as postoperatively regarding complications, fit of the implants and the clinical follow-up. In particular the enquiry of the patients shows that titanium skull implants improve quality of life. Conclusion High precision and easy handling as well as a low complication rate and the high contentedness of the patients make the individual titanium skull implants valuable for cranioplasty, especially in complicated applications with very large defects, multiple previous operations and additional irradiations. Even in these difficult cases predictable results are possible.

Mandibulabeteiligung bei der chronisch rekurrierenden multifokalen Osteomyelitis (CRMO) im Erwachsenenalter

Eine 42-jährige Patientin wurde mit der Diagnose einer primär chronischen Osteomyelitis vorstellig. Seit der Erstmanifestation etwa 9 Monate zuvor waren zahlreiche antibiotische Therapieversuche und Gewebeentnahmen ohne eindeutigen Keimnachweis vorausgegangen. Die Computertomographie zeigte schwere sklerosierende Veränderungen im gesamten rechten horizontalen Unterkieferast mit teilweise osteolytischen Bezirken. Daraufhin erfolgte die Dekortikation mit Gewinnung einer Knochen- und Weichgewebeprobe. Die histologische Begutachtung zeigte gering sklerosierten Knochen mit reaktiver periostaler Knochenneubildung, wie bei einer abgelaufenen chronisch unspezifischen Osteomyelitis. Bei Progression der Beschwerden und Parästhesien im Bereich des N. alveolaris inferior erfolgte im Hinblick auf eine geplante Unterkieferkontinuitätsresektion eine 3-Phasen-Skelettszintigraphie. Neben einer Mehrbelegung im Bereich des Unterkiefers zeigten sich auch intensive Herde an der 1. Rippe rechts, dem Sternum und der Wirbelsäule. Die nachfolgende Magnetresonanztomographie bestätigte bei sämtlichen betroffenen Knochen deutliche Infiltrate, dem Bild einer Osteomyelitis entsprechend. Unter dem Verdacht einer chronisch rekurrierenden multifokalen Osteomyelitis (CRMO) im Erwachsenenalter wurde eine immunsuppressive Therapie mit Diclofenac und Prednisolon eingeleitet, worunter es anfangs zur Vollremission kam. Da es sich bei der CRMO um ein seltenes und in unserem Fachgebiet noch weitgehend unbekanntes Krankheitsbild handelt, ist zu vermuten, dass sie sich in einigen Fällen hinter primär chronischen therapieresistenten Osteomyelitiden verbirgt. Die Problematik liegt in der frühzeitigen Diagnosestellung, da sich der therapeutische Ansatz deutlich von der Therapie der wesentlich häufigeren bakteriellen Osteomyelitis unterscheidet. Im Hinblick darauf ist die skelettszintigraphische Diagnostik therapieresistenter Osteomyelitiden dringend anzuraten. A 42-year-old patient was admitted to our clinic with the diagnosis of primary chronic osteomyelitis of the mandible. Since the initial manifestation, approximately 9 months earlier, the patient had undergone numerous antibiotic treatment trials. Various tissue specimens exhibited no microbial growth. Computer tomography demonstrated severe sclerotic changes with partly osteolytic areas in the complete right horizontal ramus of the mandible. Decortication was carried out and both soft and hard tissue specimens were taken. Histological assessment revealed slightly sclerotic bone with reactive periosteal bone production, as in chronic non-specific osteomyelitis. Because of progressive pain and paresthesia, a 3-phase skeletal scanning was performed before the planned resection. In addition to an intensive labeling in the right mandible, further intensive lesions were found at the first right rib, the sternum, and the vertebral column. The subsequent magnetic resonance tomography confirmed the infiltration, as seen in osteomyelitis, in all these areas. Under the assumption of chronic recurrent multifocal osteomyelitis (CRMO), an immunosuppressive therapy with diclofenac and prednisolone was started, which at first brought about complete remission. As CRMO is very rare in our speciality, it might be suspected that it is the cause of some cases of primary therapy-resistant osteomyelitis. The importance of early diagnosis must be underlined, because therapy differs fundamentally from that of the more common bacterial osteomyelitis. A bone scan is therefore of great value in the diagnostic scheme of therapy-resistant osteomyelitis.

Alternative Knochenersatzmaterialien zur präoperativen Fertigung individueller CAD/CAM-Schädelimplantate

Hintergrund. Die Verfahrenskette zur präoperativen Fertigung individueller CAD/CAM-Schädelimplantate ist auf den Werkstoff Titan zugeschnitten und optimiert, erlaubt jedoch grundsätzlich auch die Verarbeitung anderer Materialien. Verarbeitung anderer Materialien. Der Einsatz von Poly-(D,L-lactid) (PDLLA) als Implantatwerkstoff für individuelle Schädelimplantate wurde an einem adulten, formalinfixierten Schafkopf untersucht. Zum einzeitigen operativen Vorgehen wurde neben einem herkömmlichen Titanimplantat eine korrespondierende Sägeschablone aus Aluminium geplant und mittels computergesteuerter Fräsmaschine gefertigt. Die Herstellung einer Hohlform aus Teflon zur Fertigung eines PDLLA-Implantats mit dem CO2-Begasungsverfahren für denselben Defekt erlaubte die kritische Gegenüberstellung beider Implantatwerkstoffe. Dabei zeigte sich bezüglich Passgenauigkeit und Praktikabilität bei der Herstellung die grundsätzlich problemlose Verarbeitung des PDLLA bei Überlegenheit des Titans in Bezug auf die erreichte Präzision. Diskussion. Zielsetzung gegenwärtiger Forschungsvorhaben ist die Herstellung eines gradierten Werkstoffs aus Polylactid, Polyglycolid, Calciumphosphat und ggf. osteoinduktiven Proteinen in Verbindung mit der individuellen Formgebung durch die oben beschriebene Verfahrenskette, da die hohen Anforderungen an einen idealen Implantatwerkstoff von einem Werkstoff allein nicht erbracht werden können. Background. The preoperative manufacturing of individual skull implants using computer aided design (CAD) and computer aided manufacturing (CAM) is based on the use of titanium, although the use of other materials is also potentially possible. The use of other materials. The use of poly(D,L-lactide) (PDLLA) as an implant material was investigated using an adult, formalin fixed sheeps head with a complex frontolateral defect. A standard individual titanium implant as well as a resection template made of aluminium were milled in order to allow bone resection and reconstruction within one operation. A mould was made of Teflon for the fabrication of the PDLLA implant using carbon dioxide at high pressure. This procedure allowed a critical comparison to be made of both implant materials and showed that the production of a biodegradable PDLLA implant is possible. At present the titanium implant is superior to the PDLLA implant, as PDLLA settled with slightly larger dimensions than the mould, although the structure itself was exact. Discussion. The goal of the present research is the fabrication of a functionally graded material made of polylactide, polyglycolide, calcium phosphate and osteoinductive proteins using existing technology, which will meet all of the requirements for stability, resorption kinetics, biocompatibility, radiotranslucence and osteogenic potency of an ideal implant material.

Rekonstruktion des Os frontale mit individuellen Titanimplantaten nach chirurgischer Therapie der Stirnbeinosteomyelitis

ZusammenfassungNach chirurgischer Therapie der Stirnbeinosteomyelitis ermöglichen individuell hergestellte Titanimplantate die Wiederherstellung einer mechanisch stabilen Hirnprotektion und einer ästhetisch befriedigenden Stirnkontur.Nach dem Primäreingriff erfolgt die Datenakquisition mittels Spiralcomputertomographie (Spiral-CT) und Weiterleitung an ein Computer Aided Design-System (CAD-System). Die Implantatkonstruktion erfolgt auf der Basis von Freiformflächen, wobei sich die Implantatgeometrie aus den knöchernen Defektgrenzen ableitet. Die Fertigungsdaten werden anschließend an eine computergesteuerte Fräsmaschine übermittelt und das Implantat aus einem Block Reintitan gefertigt.Die standardisierte Fertigung mittels CAD/CAM unter Verwendung von CT-Daten gewährleistet eine exakte Passform der Implantate. Hierdurch wird zusätzlich eine Verkürzung der Operationszeiten erreicht.Im Nachbeobachtungszeitraum von 5 bis 42 Monaten wurde kein Implantatverlust oder ein Rezidiv der Stirnbeinosteomyelitis beobachtet.AbstractIndividually prefabricated titanium implants enable the reconstruction of the frontal bone after surgical therapy of osteomyelitis without compromising mechanical stability or aesthetic results.Primarily the infected bone tissue is removed. Helical computed tomographic systems are used for the aquisition of patient data. After being transmitted to a computer aided design system (CAD-system) this data is used for construction of the implant geometry using freeform-surfaces. The outer surface contour is derived from the contours of the bone defect. The completed computer-based implant design is finally transformed into control data to run the milling machine which produces the implant from a block of titanium.Modern industrial CAD/CAM-technology allows standardized prefabrication using data from CT-scans. The precision of all implants was predictable and duration of the reconstructive procedure could be reduced.During postoperative follow-up (5–24 months) no loss of implant or recurrence of the osteomyelitis could be observed.

Single-step robot guided bone resection and individual reconstruction of the skull

The TICC (Tomography Image processing CAD-CAM) processing chain allows the supply of existing craniofacial defects with individually prefabricated implants based on helical CT data [1, 2]. In combination with individual templates single-step bone resection and reconstruction is available [3, 4, 5, 6]. New developments in navigation and robotics allowed a robot guided bone resection according to the preoperative planning with the CAD system [7, 8, 9, 10]. This study shows results of resection experiments on ovine cadaver heads.

Kadaverstudie: Roboterunterstützte Schädelresektion und Versorgung mit Titanimplantaten

A processing chain for the prefabrication of individual titanium implants for cranioplasty was developed at the Ruhr-University Bochum. In patients with tumours a simultaneous resection of cranial bone and insertion of the individual implant is desirable. At first resection templates were used for this. New developments aim at a preoperative definition of resection trajectories for surgical robots corresponding to both the planning of the resection and the implant. This study used ovine cadaver skulls for robot resection experiments. The results demonstrate possible applications, limitations and necessary prerequisites in robot assisted cranial surgery.

FORMGEBUNG DEGRADIERBARER WERKSTOFFE MIT HILFE DER VERFAHRENSKETTE ZUR FERTIGUNG INDIVIDUELLER CAD/CAM-IMPLANTATE

Die an der Ruhr-Universität Bochum entwickelte Verfahrenskette zur präoperativen Herstellung individueller Schädclimplantatc basiert auf Computertomographie (CT)-Daten des Patienten und bedient sich Computer Aided Design (CAD) und Computer Aided Manufacturing (CAM) [1,2, 3]. Dabei ist die Verfahrenskctte auf den Werkstoff Titan zugeschnitten und optimiert, erlaubt jedoch grundsätzlich auch die Verarbeitung anderer Materialien durch Fräsen oder in einer Hohlform [4]. Biodegradierbare Werkstoffe wie Polymere sind diesbezüglich von besonderem Interesse, da sie als Trägersubstanz für osteoinduktive Proteine eine Knochcnncubildung bei gleichzeitiger Degradation es Carriers ermöglichen [5, 6, 7].

EIN GRADIERTER KOMPOSITWERKSTOFF FÜR DEN EINSATZ IM BEREICH DES HIRN- UND GESICHTSSCHÄDELS

For the reconstruction of complex skull defects with individual prefabricated CAD/CAM-implants titanium is well established as bone substitution material. The aim of our studies was to optimize a composite material from polyesters and calcium phosphate. Therefore two different operating procedures (hot pressing and gas-flushing) were combined. As a result the graded composition and porosity of the implants allow a spatial guided degradation progress and cell ingrowth. First biocompatibility tests in vitro with primary human osteoblasts showed a much better pH-characteristic and a better biocompatibility of the composites in comparison with the pure polymers. Degradation experiments in vitro confirmed the different expected degradation rates of the composite materials. As a next step in vivo experiments in ovine skulls are in progress.