Egbert Machtens

Reconstruction of craniofacial bone defects with individual alloplastic implants based on CAD/CAM-manipulated CT-data

Reconstruction of craniofacial bone defects by intraoperative modelling of autogenous or alloplastic materials may cause undesirable results concerning the implant shape or the long-term maintenance of this shape. Furthermore, the use of alloplastic materials to be modelled intraoperatively may result in an inflammatory tissue response. Therefore the question is raised whether CAD/CAM-techniques may be used for the pre-operative geometric modelling of the implant based on helical computed tomography data. A numerically based 3-dimensional model of the skull defect serves as the basis for a freeform-surfaces design of the implant shape, position and thickness, using modelling tools and programmes developed for industrial CAD/CAM. The precise and individual fit of the implant results from generating its margins by the borders of the defect, whereas the implant surface is generated by the geometry of the non-affected neighbouring bone contours. The implant data run a numerically controlled milling machine to fabricate the individual implant. The reconstruction of post-traumatic defects of the forehead, of post-surgical temporal defects after intracranial haemorrhage, and of a parieto-occipital defect due to ablative tumour surgery are presented as the first clinical experiences of this new method.

Reconstruction of an extreme frontal and frontobasal defect by microvascular tissue transfer and a prefabricated titanium implant.

: A 30-year-old man was referred to us with an extreme frontal and frontobasal defect from a motorbike accident 12 years before. Multiple attempts at frontal and frontobasal revision and reconstruction had been performed over the years, with several episodes of meningitis. Reconstruction was planned in two steps. First, a revision of the anterior skull base with mobilization of meningeal adhesions and duraplasty, removal of infected masses of polymethylmethacrylate out of the upper ethmoid sinuses, and coverage with a deepithelialized latissimus dorsi free flap were performed. In the second step 3 months later, aesthetic forehead reconstruction was achieved with a pre-fabricated individual titanium implant. The predictable result of this two-step reconstruction was very pleasing. Safe separation of the cranial cavity from the upper airways was essential, requiring free tissue transfer in this case, and is a prerequisite for any alloplastic forehead reconstruction. Timing of the two-step procedure, including the CT data acquisition; handling of soft tissues, bone, and foreign material; and construction details of the implant demonstrate the necessary complex management of this, the most difficult case of the 88 applications of the new computer aided design and manufacturing technique thus far. Even the most elaborate computer aided preparation cannot be successful without consideration of established surgical principles.A 30-year-old man was referred to us with an extreme frontal and frontobasal defect from a motorbike accident 12 years before. Multiple attempts at frontal and frontobasal revision and reconstruction had been performed over the years, with several episodes of meningitis. Reconstruction was planned in two steps. First, a revision of the anterior skull base with mobilization of meningeal adhesions and duraplasty, removal of infected masses of polymethylmethacrylate out of the upper ethmoid sinuses, and coverage with a deepithelialized latissimus dorsi free flap were performed. In the second step 3 months later, aesthetic forehead reconstruction was achieved with a pre-fabricated individual titanium implant. The predictable result of this two-step reconstruction was very pleasing. Safe separation of the cranial cavity from the upper airways was essential, requiring free tissue transfer in this case, and is a prerequisite for any alloplastic forehead reconstruction. Timing of the two-step procedure, including the CT data acquisition; handling of soft tissues, bone, and foreign material; and construction details of the implant demonstrate the necessary complex management of this, the most difficult case of the 88 applications of the new computer aided design and manufacturing technique thus far. Even the most elaborate computer aided preparation cannot be successful without consideration of established surgical principles.

Microsurgical tissue transfer for rehabilitation of the patient with cleft lip and palate.

OBJECTIVE Three case reports of microsurgically revascularized tissue transfer for secondary closure of complex oronasal fistulae in cleft lip and palate patients are reported. One scapular and two radial forearm flaps were used in that respect; the scapular flap was transferred without a skin paddle and was left for secondary epithelialization whereas iliac crest bone was transplanted in the two patients with the forearm flaps in a further surgical step. CONCLUSIONS These microsurgical flaps represent solutions in selected cases of oronasal fistulae in patients with cleft lip and palate with extensive scarring, large defects, or both. Alternative free flaps of the vast spectrum available today, however, also deserve consideration.

Bedeutung von Alveolar- kammhöhe und -breite für die Implantologie am zahnlosen Oberkiefer

Zusammenfassung Die Betrachtung von Alveolarkammprofilen und klinische Erfahrungen zeigen, daß die transversale Dimension in der zahnärztlichen Implantologie bisher vernachlässigt worden ist. Im Hinblick auf eine grundlegende Auswertung des Einflusses von Kieferkammhöhe und -breite erfolgte zunächst die Analyse von 95 zahnlosen knöchernen Oberkiefern aus Sammlungen, die standardisiert gesägt, vermessen und klassifiziert waren. Für 4 Implantattypen (10 mm Mindestlänge) wurden so an 269 Querschnitten 1076 Implantationen simuliert und differenziert nach Implantattyp, Querschnittlage und Atrophieklasse ausgewertet. Ähnlich wurde im klinischen Studienteil bei 24 konsekutiven Implantatpatienten mit zahnlosem Oberkiefer verfahren. Eine Implantateinbringung am Leichenkiefer war nur in 35% der Querschnitte möglich, aber bei ausreichender Kieferhöhe in weiteren 4,5% eigentlich zu erwarten gewesen. Implantatlängenreduktionen wurden zusätzlich in 6% notwendig. Dabei bestanden Abhängigkeiten v. a. zur Atrophieklasse. Anteriore Querschnitte boten wesentlich günstigere Voraussetzungen als posteriore. Demgegenüber war Implantierbarkeit bei keinem der 24 Patienten gegeben. Primär unzureichende Höhe lag in 22 Fällen vor, 2mal stellte sich bei ausreichender Höhe ein transversal zu schmaler Alveolarkamm erst unter der Operation heraus. Die Ergebnisse erlauben die Quantifizierung der Bedeutung von vertikaler und transversaler Oberkieferalveolarkammdimension. Diese Bedeutung liegt vorrangig bei der Knochenhöhe, obwohl auch bei ausreichender Höhe häufig Reduktionen der Implantatlänge nötig werden. Sowohl am Leichenkiefer (12% der Schnitte mit erwarteter Implantierbarkeit) als auch am Patienten (8%) verbleiben jedoch Alveolarkammprofile, für welche die alleinige Höhenausmessung falsche Verhältnisse vortäuscht und evtl. ein exakt geplanter operativer Eingriff abgebrochen werden muß. Komplexität und Preis der implantologischen Rehabilitation und die Tragweite einer inkorrekten präoperativen Planung rechtfertigen oder verlangen sogar daher grundsätzlich erweiterte schnittbilddiagnostische Maßnahmen. Summary Consideration of alveolar profiles and clinical experience demonstrate that the transversal dimension has been neglected in dental implantology so far. For a comprehensive evaluation of the impact of alveolar bone height and width, 95 edentulous bony maxillae with standardized, measured, and classified cross-sections were analyzed. With four types of implants (minimum length, 10 mm), 1076 insertions were simulated at 269 cross-sections and evaluated with regard to type of implant, position of cross-section, and class of atrophy. Similar evaluation was carried out in the clinical part of the study on 24 consecutive patients with edentulous maxillae. Implant insertion could only be simulated in 35% of the cadaver cross-sections, but had been expected in an additional 4.5% based on their sufficient bone height; length reductions were necessary in another 6%. These results depended largely on the class of atrophy. Anterior cross-sections offered better conditions than posterior ones. In contrast, implant insertion was impossible in all 24 patients. Height was primarily inadequate in 22 patients, and in two patients with sufficient bone height inadequate transversal dimensions were only recognised intraoperatively. These results allow a quantification of the impact of vertical and transversal maxillary alveolar bone dimensions. This impact primarily depends on bone height, but even with sufficient height, reductions of implant length often become necessary. Both for the cadaver maxillae (12% of the cross-sections with expected implant insertion) and for the patients (8%), alveolar profiles remain in which height measurement alone leads to incorrect assessment and may even result in the interruption of precisely planned surgical procedures. The complexity and expense of implant-borne rehabilitation and the consequences resulting from incorrect preoperative planning therefore generally justify extended cross-sectional diagnostic measuring.Consideration of alveolar profiles and clinical experience demonstrate that the transversal dimension has been neglected in dental implantology so far. For a comprehensive evaluation of the impact of alveolar bone height and width, 95 edentulous bony maxillae with standardized, measured, and classified cross-sections were analyzed. With four types of implants (minimum length, 10 mm), 1076 insertions were simulated at 269 cross-sections and evaluated with regard to type of implant, position of cross-section, and class of atrophy. Similar evaluation was carried out in the clinical part of the study on 24 consecutive patients with edentulous maxillae. Implant insertion could only be simulated in 35% of the cadaver cross-sections, but had been expected in an additional 4.5% based on their sufficient bone height; length reductions were necessary in another 6%. These results depended largely on the class of atrophy. Anterior cross-sections offered better conditions than posterior ones. In contrast, implant insertion was impossible in all 24 patients. Height was primarily inadequate in 22 patients, and in two patients with sufficient bone height inadequate transversal dimensions were only recognised intraoperatively. These results allow a quantification of the impact of vertical and transversal maxillary alveolar bone dimensions. This impact primarily depends on bone height, but even with sufficient height, reductions of implant length often become necessary. Both for the cadaver maxillae (12% of the cross-sections with expected implant insertion) and for the patients (8%), alveolar profiles remain in which height measurement alone leads to incorrect assessment and may even result in the interruption of precisely planned surgical procedures. The complexity and expense of implant-borne rehabilitation and the consequences resulting from incorrect preoperative planning therefore generally justify extended cross-sectional diagnostic measuring.

One-step resection and reconstruction of the mandible using computer-aided techniques--experimental and clinical results.

Summary In patients with advanced oral cancer, a resection of the mandible continuity is often indicated. This new method presented here uses computer-aided design and manufacturing (CAD/CAM) for preoperative fabrication of individual mandibular prostheses and their corresponding resection templates in a direct fashion without the need for additional physical models. In this experimental application, a segment of a dried mandible was resected and replaced by a titanium prosthesis prefabricated by CAD/CAM. It was the aim of this investigation to verify the processing chain and its precision, i.e., the fit of an individual implant, such as this. Although this new technique offers fascinating opportunities, possible clinical drawbacks have to be taken into account. Zusammenfassung In Fällen von fortgeschrittenen Mundhöhlenneoplasien besteht häufig die Indikation zur Unterkieferkontinuitätsresektion. Das dargestellte neue Verfahren basiert auf Computer-aided-Design und Manufacturing (CAD/CAM) zur präoperativen Anfertigung von individuellen Implantaten und korrespondierenden Resektionsschablonen durch direkte Herstellung ohne Notwendigkeit zusätzlicher Arbeitsmodelle. In dieser experimentellen Anwendung wurde mit einer in CAD/CAM-Technik hergestellten Resektionsschablone die Segmentresektion eines Leichenunterkiefers und seine simultane Rekonstruktion durchgeführt. Das Ziel dieser Studie war es, die Verfahrenstechnik zu verifizieren und ihre Präzision durch die Paßgenauigkeit eines solchen individuellen Implantats zu überprüfen. Trotz der faszinierenden Möglichkeiten, die diese neue Technik bietet, sollten mögliche klinische Einschränkungen nicht außer acht gelassen werden.

Pigmentierte villonoduläre Synovitis des Kiefergelenks mit Einbruch in die mittlere Schädelgrube

Der Fall eines 63jährigen Manns mit einer pigmentierten villonodulären Synovitis wird beschrieben. Bedingt durch expansives Tumorwachstum kam es zur Destruktion der rechten Kiefergelenkpfanne und zum Einbruch in die mittlere Schädelgrube. In der Vorgeschichte erfolgte auswärts, aufgrund uncharakteristischer Symptome, eine rein symptomatische Behandlung. Schließlich wurde in Intubationsnarkose eine Tumorresektion durchgeführt. Der Patient ist 20 Monate rezidivfrei und mit dem Therapieergebnis zufrieden. Differentialdiagnose und Therapie werden diskutiert. A 63-year-old man is presented in whom a tenosynovial giant-cell tumor destroyed the right temporomandibular joint and fossa and showed extensive intracranial growth. Because of uncharacteristic complaints, a symptomatic treatment was performed elsewhere. The lesion was finally resected under endotracheal anesthesia. After 20 months free of recurrence the patient’s outcome is very satisfying. Differential diagnosis and therapy are discussed.

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.

Reintitan als Knochenersatzmaterial

Computergestützt vorgefertigte Schädelimplantate aus Reintitan als Knochenersatzmaterial werden seit 1994 in 22 Kliniken eingesetzt. Die Erfahrungen mit 104 Implantaten umfassen klinische (Indikationsstellung; Implantatlager; Operationstechnik; Patientenführung), aber auch geometrische und materialspezifische Aspekte (CT-Datenakquisition, -transfer und -auswertung; Konstruktion; Fertigung; Reinigung; postoperative Einsatzmöglichkeit bildgebender Verfahren). Während die klinischen Aspekte im Verantwortungsbereich ärztlichen Handelns definiert werden, gilt für die geometrischen und materialspezifischen Aspekte bei individuellen Implantaten das Medizinproduktegesetz. Prospektiv werden entsprechend für jedes Implantat die Spiral-CT-Akquisitionsparameter, die Geometriedaten des rechnerinternen Schädelmodells und des Implantats, das Reinigungsverfahren und die individuelle Kennzeichnung dokumentiert. Medizinisch spezifiziertes Reintitan wird ausschließlich durch Fräsung bearbeitet, sodass weder Reinheit noch Gefüge Änderungen erfahren. Eine eigens entwickelte Frästechnik garantiert die Umsetzung aller konstruierter Elemente bis zu einer Feinheit von 50 μm. Im Hinblick auf die bei tumorbedingten Defekten notwendige bildgebende Verlaufskontrolle werden sämtliche Patienten der eigenen Klinik postoperativ mit MRT untersucht, z. T. mit einer präoperativen Darstellung als intraindividuelle Kontrolle. Eine umfassende Dokumentation und Qualitätssicherung ist für Techniken des vorgefertigten Knochenersatzes unabdingbar. Parallel zur forscherischen Entwicklung und ärztlichen Anwendung müssen diese formalen Kriterien für das jeweilige Verfahren bearbeitet und erfüllt werden. Die erfolgreiche Erarbeitung von eigens adaptierten MRT-Sequenzen geht darüber noch hinaus: Spinechosequenzen minimieren die durch die Titanimplantate erzeugten Feldinhomogenitäten und erlauben eine aussagekräftige postoperative Dokumentation und Diagnostik insbesondere nach Tumoroperationen in der Verlaufsbeobachtung. Computer-assisted prefabricated skull implants of pure titanium as a bone replacement material have been used in 22 departments since 1994. Our experience with 104 implants includes clinical aspects (indication; tissue quality; surgical technique; patient guidance), but also geometric and material-specific parameters (acquisition, transfer, and evaluation of CT data; construction; manufacturing; cleaning; postoperative use of radiologic techniques). While the clinical aspects are responsibly defined by the respective surgeon, the geometric and material-specific parameters of individual implants have to comply with the laws on medical products. Therefore, the prospective documentation for each implant includes: helical CT acquisition parameters; geometric data of the computer-based skull model and implant; the cleaning procedure; and the individual marking. Medically specified pure titanium is processed by milling only so that neither purity nor structure is impaired. A specially developed milling technique guarantees the fabrication of all constructed elements down to fine details of 50 μm. Considering the necessary radiologic follow-up of defects after tumor surgery, all patients in our hospital undergo postoperative MRI examination, partly with preoperative documentation as an intraindividual control. Such comprehensive documentation and quality assurance is essential for techniques of prefabricated bone substitution. Hand in hand with scientific research and clinical application, these formal criteria have to be elaborated and fulfilled for the respective techniques. The successful determination of specifically adapted MRI sequences goes even one step further: spin-echo sequences minimize inhomogeneities of the magnetic field induced by the titanium implants and enable accurate postoperative documentation and diagnostics especially in the follow-up after tumor surgery.Computer-assisted prefabricated skull implants of pure titanium as a bone replacement material have been used in 22 departments since 1994. Our experience with 104 implants includes clinical aspects (indication; tissue quality; surgical technique; patient guidance), but also geometric and material-specific parameters (acquisition, transfer, and evaluation of CT data; construction; manufacturing; cleaning; postoperative use of radiologic techniques). While the clinical aspects are responsibly defined by the respective surgeon, the geometric and material-specific parameters of individual implants have to comply with the laws on medical products. Therefore, the prospective documentation for each implant includes: helical CT acquisition parameters; geometric data of the computer-based skull model and implant; the cleaning procedure; and the individual marking. Medically specified pure titanium is processed by milling only so that neither purity nor structure is impaired. A specially developed milling technique guarantees the fabrication of all constructed elements down to fine details of 50 microns. Considering the necessary radiologic follow-up of defects after tumor surgery, all patients in our hospital undergo postoperative MRI examination, partly with preoperative documentation as an intraindividual control. Such comprehensive documentation and quality assurance is essential for techniques of prefabricated bone substitution. Hand in hand with scientific research and clinical application, these formal criteria have to be elaborated and fulfilled for the respective techniques. The successful determination of specifically adapted MRI sequences goes even one step further: spin-echo sequences minimize inhomogeneities of the magnetic field induced by the titanium implants and enable accurate postoperative documentation and diagnostics especially in the follow-up after tumor surgery.