F Lassner

RWTH Aachen University, Aachen, North Rhine-Westphalia, Germany

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Publications (40)59.49 Total impact

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    ABSTRACT: The use of bioengineered nerve guides as alternatives for autologous nerve transplantation (ANT) is a promising strategy for the repair of peripheral nerve defects. In the present investigation, we present a collagen-based micro-structured nerve guide (Perimaix) for the repair of 2 cm rat sciatic nerve defects. Perimaix is an open-porous biodegradable nerve guide containing continuous, longitudinally orientated channels for orientated nerve growth. The effects of these nerve guides on axon regeneration by six weeks after implantation have been compared with those of ANT. Investigation of the regenerated sciatic nerve indicated that Perimaix strongly supported directed axon regeneration. When seeded with cultivated rat Schwann cells (SC), the Perimaix nerve guide was found to be almost as supportive of axon regeneration as ANT. The use of SC from transgenic green-fluorescent-protein (GFP) rats allowed us to detect the viability of donor SC at 1 week and 6 weeks after transplantation. The GFP-positive SC were aligned in a columnar fashion within the longitudinally orientated micro-channels. This cellular arrangement was not only observed prior to implantation, but also at one week and 6 weeks after implantation. It may be concluded that Perimaix nerve guides hold great promise for the repair of peripheral nerve defects.
    Biomaterials 11/2011; 33(5):1363-75. · 8.31 Impact Factor
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    ABSTRACT: Deutsche Gesellschaft für Chirurgie Chirurgisches Forum und DGAV Forum 2009für experimentelle und klinische Forschung 126. Kongress der Deutschen Gesellschaft für Chirurgie München, 28.04.-01.05.2009 10.1007/978-3-642-00625-8_107 V.Schumpelick, H.-P.Bruch und H.K.Schackert Peripheres Nervensystem: Neuro-Tissue Engineering mit einem mikrostrukturierten Kollagenträger als bioartifizielle Nervenleitschiene A.Bozkurt43, 44, G.A.Brook44, I.Heschel45, F.Lassner43, S.Möllers45, L.Olde Damink45, F.Schügner45, R.Deumens46, D.M.O’Dey43, R.Tolba46, B.Sellhaus44, J.Weis44 und N.Pallua43 (43) Klinik für Plastische Chirurgie, Hand- und Verbrennungschirurgie, Universitätsklinikum der RWTH Aachen, Pauwelsstr. 30, 52074Aachen, Deutschland (44) Institut für Neuropathologie, Universitätsklinikum der RWTH Aachen, Deutschland (45) Matricel GmbH, Herzogenrath, Deutschland (46) Institut für Versuchstierkunde, Universitätsklinikum der RWTH Aachen, Deutschland Peripheral nervous system: Neuro-Tissue Engineering using a microstructured collagen matrix A.BozkurtEmail: abozkurt77@gmx.de
    12/2008: pages 289-291;
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    ABSTRACT: Complete nerve transection (neurotmesis) of the rat sciatic nerve is a well-established animal model. The most frequently used behavioural for evaluation of neurotmesis-induced deficits is the walking track analysis with calculation of the sciatic functional index (SFI). More recently, the static sciatic index (SSI) has been developed, which shows a good correlation with the SFI. However, despite all advantages (high accessibility, easy handling, high accuracy, cost-effectiveness), the SSI is still not widely used. We, therefore, developed a novel programme ("Visual-SSI"), which will be made freely available for the assessment of the SSI. As gold-standard for the treatment of neurotmesis-induced nerve gaps, autologous nerve transplantation studies in the rat sciatic nerve model (n=16 [6 weeks], n=8 [12 weeks]) were carried out to test the effectiveness and feasibility of the Visual-SSI software. We observed a significant recovery starting from the pre-operative condition over the 3rd, 6th, 9th weeks until the 12th week after surgery (p<0.05). Theoretically, the SSI can be calculated from both rearing and normal standing position of the rats and we investigated whether the SSI is affected differentially by these positions. We observed no significant differences between animals in a rearing and normal standing stance (p>0.05). The present method combines efficiency (simplicity of use, rapid and economical setup) with accurate and precise quantification of the functional regeneration in the sciatic nerve lesion model of the rat.
    Journal of Neuroscience Methods 06/2008; 170(1):117-22. · 2.11 Impact Factor
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    ABSTRACT: The goal of this study was the development of a bioartificial nerve guide to induce axonal regeneration in the peripheral nervous system (PNS). In this in vitro study, the ability of a novel, 3-dimensional (3D), highly oriented, cross-linked porcine collagen scaffold to promote directed axonal growth has been studied. Collagen nerve guides with longitudinal guidance channels were manufactured using a series of chemical and mechanical treatments with a patented unidirectional freezing process, followed by freeze-drying (pore sizes 20-50 microm). Hemisected rat dorsal root ganglia (DRG) were positioned such that neural and non-neural elements could migrate into the collagen scaffold. After 21 days, S100-positive Schwann cells (SCs) migrated into the scaffold and aligned within the guidance channels in a columnar fashion, resembling "Bands of Büngner." Neurofilament-positive axons (mean length +/- SD 756 microm +/- 318 microm, maximum 1496 microm) from DRG neurons entered the scaffold where the growth within the guidance channels was closely associated with the oriented SCs. This study confirmed the importance of SCs in the regeneration process (neurotrophic theory). The alignment of SCs within the guidance channels supported directional axonal growth (contact guidance theory). The microstructural properties of the scaffold (open, porous, longitudinal pore channels) and the in vitro data after DRG loading (axonal regeneration along migrated and columnar-aligned SCs resembling "Band of Büngner") suggest that this novel oriented 3D collagen scaffold serves as a basis for future experimental regeneration studies in the PNS.
    Tissue Engineering 01/2008; 13(12):2971-9. · 4.25 Impact Factor
  • Journal of Plastic Reconstructive and Aesthetic Surgery - J PLAST RECONSTR AESTHET SURG. 01/2007; 60(4).
  • Journal of Plastic Reconstructive & Aesthetic Surgery 09/2006; 59(9). · 1.44 Impact Factor
  • M H J Becker, F Lassner
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    ABSTRACT: The thoracic outlet compression syndrome has a great number of clinical variations. Arterial and venous perfusion impairment is an associated symptom, nerve irritation can occur with or without vascular problems. The degree of nerve damage ranges from transient irritation to permanent motoric and sensory defects. The lack of space in the supracostoclavicular compartment is the cause for nerve compression. The degree of neural damage depends on the degree and duration of the compression. Anatomic variations between the clavicle and first rib are frequent causes for the TOS: accessory ribs and muscles, and fibrous bands have been described. A preexisting chronic compression may lead to a subclinical TOS, in this case an inadequate trauma of minor degree may be sufficient to manifest a plexus palsy. Intraoperative findings in children with incomplete and complete brachial plexus palsy and the corresponding findings in adults prompted us to present this communication.
    Handchirurgie · Mikrochirurgie · Plastische Chirurgie 03/2006; 38(1):51-5. · 0.86 Impact Factor
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    ABSTRACT: Loss of muscle tissue at the area of the neuromuscular junction after tumor resection or after trauma precludes the reconstruction with conventional nerve grafts, because the distal nerve stump is absent. For these cases, we recommend direct insertion of the nerve grafts into the muscle. We describe a standardized technique, which has been performed in 19 patients and led to a mean motor recovery of grade M4 after Highet. The key procedure of this technique is the interfascicular dissection of the nerve grafts, which allows a wide distribution of the grafts into the muscle tissue.
    Handchirurgie · Mikrochirurgie · Plastische Chirurgie 04/2003; 35(2):127-31. · 0.86 Impact Factor
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    ABSTRACT: In brachial plexus lesions and their revision, evaluation of nerve stumps is very important for the reconstructive strategy. We intraoperatively perform cryostat sections, Haematoxilin-Eosin (HE) stained, and compare the clinical appearance of the nerves to the microscopic results. Toluidine blue staining is later used to validate the structural details. Intraneural fibrosis can be traced safely with both staining methods, in root avulsions a histology is helpful, too. For more proximal, intraforaminal lesions semithin section stained with toluidine-blue are less informative than are HE-stained cryostat sections. In these lesions the clinical control by electrical stimulation and evoked potentials is superior.
    Handchirurgie · Mikrochirurgie · Plastische Chirurgie 04/2003; 35(2):112-6. · 0.86 Impact Factor
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    ABSTRACT: A modified surgical technique is introduced, enabling restoration of muscle function with direct muscular neurotization. Reliable clinical outcomes result from this technique. We report on a series of 10 patients in whom the supplying motor nerve had been lost at the level of the neuromuscular junction as the result of trauma or tumor resection. Our modification of the operative technique ensures a wide distribution of nerve fibers throughout the remaining muscle tissue and produces a mean motor recovery of M4 after a period of 1 to 2 years.
    Muscle & Nerve 10/2002; 26(3):362-6. · 2.31 Impact Factor
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    ABSTRACT: Controversy surrounds the aetiology of obstetric brachial plexus lesions. Most authors consider that it is caused by traction or compression of the brachial plexus during delivery. Some patients, however, present without a history of major traction during delivery, and some delivered by Caesarean section also suffer the injury. In our series of 42 infants, 28 had an Erb's palsy, and the remaining 14 presented with a more extensive lesion, involving the lower roots. In five of these, a complete ossified cervical rib was found. We believe that anatomical variations, such as cervical ribs or fibrous bands, can cause narrowing of the supracostoclavicular space, and render the adjacent nerves more susceptible to external trauma.
    Journal of Bone and Joint Surgery - British Volume 08/2002; 84(5):740-3. · 2.69 Impact Factor
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    ABSTRACT: The authors present a series of 15 patients with large soft-tissue defects of the fingertips as a prospective, nonrandomized study. In all cases, reconstruction was achieved using a bilaterally innervated sensory cross-finger flap. This sensory fasciocutaneous flap relies on the dorsal branch of the proper digital nerves, which branch off at the level of the head of the proximal phalanx; sensory supply to the dorsal skin of the middle phalanx is thus ensured. The reconstructive procedure consists of two steps. First, the contralateral dorsal branch of the proper digital nerve is elevated with the flap at proximal interphalangeal joint level. Microsurgical coaptation is performed to the proximal nerve stump of the injured fingertip. After 3 weeks, when the pedicle is dissected, the second nerve is dissected and coapted. Clinical results were evaluated after 12 months. Because the regenerative distance is only 1.5 to 2.5 cm, good sensory regeneration should be expected. In nine of 16 flaps, sensory quality of S2+ (Highet) was present in the flap after 3 weeks. After 12 months, two-point discrimination was present in all patients, the values ranging between 2 and 6 mm (for two-point discrimination), with an average of 3.6 mm. The rate of complications was low. With acceptable additional operative action, a good functional result can be achieved. The indications of this method are discussed in comparison with other methods of fingertip reconstruction.
    Plastic &amp Reconstructive Surgery 04/2002; 109(3):988-93. · 3.54 Impact Factor
  • F Lassner, M Becker, N Pallua
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    ABSTRACT: Complex hand injuries are characterized by a combination of soft tissue injury and additional trauma to functional structures such as nerves, bones, tendons, vessels and joints. A good functional result requires the reconstruction of the injured structures and early mobilisation. Good vascularized soft tissue and stable osteosyntheses are the major prerequisites to avoid infections and to allow early mobilisation. The optimal timing for soft tissue reconstruction remains controversial with respect to the incidence of infections. We have evaluated retrospectively our series of complex hand injuries addressing the question whether a delay of soft tissue coverage for up to 72 hours causes significant increase of infection rates. 48 patients were treated with complex injuries of the hand within a three year period between December 1998 and December 2000. The lowest incidence of infections occurred in the group, where soft tissue coverage was completed as an emergency procedure. Ideally primary reconstruction of complex hand injuries should be strived for to minimize scar formation as a result of secondary operations and further immobilisation periods. This includes, if necessary, free tissue transfer. Exceptions are situations where the vitality of soft remains uncertain. In these cases, definitive surgery is delayed for a maximum period of 72 hours.
    Der Chirurg 01/2002; 72(12):1439-45. · 0.52 Impact Factor
  • F. Lassner, M. Becker, N. Pallua
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    ABSTRACT: Einleitung: Komplexe Handverletzungen sind durch eine Kombination von schwerem Weichteilschaden und Zusatzverletzungen (Frakturen und Mitbeteiligung funktioneller Strukturen wie Nerven, Sehnen, Gefäße, Gelenken und Bandapparat) charakterisiert. Ein gutes funktionelles Ergebnis kann nur erzielt werden, wenn nach Wiederherstellung der verletzten Strukturen eine frühe Übungsbehandlung möglich ist. Gut durchblutete Weichteile und übungsstabile Osteosynthesen sind die wesentliche Voraussetzung zur Vermeidung von Infekten und zur Durchführung einer frühfunktionellen Behandlung. Zur Frage des Zeitpunktes der Rekonstruktion der Weichteile gibt es divergierende Meinungen, insbesondere was das Risiko für Wundinfektionen anbelangt. Methoden: In einer retrospektiven Studie wurden die Komplexverletzungen der Hand an der Klinik für Plastische Chirurgie, Hand- und Verbrennungschirurgie unter der Fragestellung nachuntersucht, ob eine um bis zu 72 Std. verzögerte Rekonstruktion der Weichteile einen Einfluss auf die Häufigkeit von Wundinfekten hat. Ergebnisse:Über einen Zeitraum von 3 Jahren von Dezember 1998 bis Dezember 2000 wurden 48 Patienten mit komplexen Handverletzungen behandelt. Die niedrigste Infektrate wurde in der Gruppe erreicht, bei der die Defektdeckung notfallmäßig erfolgte. Diskussion: Idealerweise sollte eine komplette Primärversorgung angestrebt werden, um weitere Narbenbildung durch spätere operative Eingriffe sowie zusätzliche Immobilisierungszeiten zu minimieren. Diese schließt den notfallmäßigen freien Gewebetransfer ein. Ausnahmen werden da gemacht, wo die Vitalität der Weichteile primär nicht sicher beurteilbar ist. In diesem Fall erfolgt die Versorgung innerhalb der 72-Std.-Grenze. Introduction: Complex hand injuries are characterized by a combination of soft tissue injury and additional trauma to functional structures such as nerves, bones, tendons, vessels and joints. A good functional result requires the reconstruction of the injured structures and early mobilisation. Good vascularized soft tissue and stable osteosyntheses are the major prerequisites to avoid infections and to allow early mobilisation. The optimal timing for soft tissue reconstruction remains controversial with respect to the incidence of infections. Methods: We have evaluated retrospectively our series of complex hand injuries adressing the question whether a delay of soft tissue coverage for up to 72 hours causes significant increase of infection rates. Results: 48 patients were treated with complex injuries of the hand within a three year period between December 1998 and December 2000. The lowest incidence of infections occured in the group, where soft tissue coverage was completed as an emergency procedure. Discussion: Ideally primary reconstruction of complex hand injuries should be strived for to minimize scar formation as a result of secondary operations and further immobilisation periods. This includes, if necessary, free tissue transfer. Exceptions are situations where the vitality of soft remains uncertain. In these cases, definitive surgery is delayed for a maximum period of 72 hours.
    Der Chirurg 01/2001; 72(12):1439-1445. · 0.52 Impact Factor
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    ABSTRACT: The utilization of viable biological nerve graft substitutes and nerve allografts raises the problem of nerve storage. To clarify this, rat sciatic nerve segments were harvested and stored in Dulbecco's modified eagle medium. The segments were divided into three groups. In the first group, no cryoprotectant was added, whereas the second had 10% dimethyl sulfoxide (DMSO) added as cryoprotectant. These two groups of nerve segments were subjected to controlled freezing. In a third group, segments were frozen uncontrolled in liquid nitrogen (-196 degrees C). All nerves were replanted orthotopically. Fresh conventional autografts (fourth group) served as control group. Histologically, freezing did not affect the structural elements such as basal lamina tubes and perineurial tissue. Morphometrically, all cryopreserved grafts had significantly reduced axon counts and less myelinization than did controls. Cryoprotected nerves (group 2) showed no different morphometric parameters compared with the group without DMSO (group 1). Controlled freezing was superior to uncontrolled freezing (group 3). Impaired regeneration was attributed mainly to delayed Wallerian degeneration and slower revascularization. Moreover, decreased survival of resident Schwann cells in the graft may impair regeneration due to the lack of neurotrophic, neurotropic, and attachment factors in early regeneration. Grafts subjected to controlled freezing support axonal regeneration to a certain extent, but further studies are required to assess various cooling patterns, cryoprotectants, and graft revascularization.
    Muscle & Nerve 09/2000; 23(8):1227-33. · 2.31 Impact Factor
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    ABSTRACT: The resident macrophages have been accepted as an important component of the peripheral nervous system as Schwann cells. To elucidate their role during Wallerian degeneration without interference from extrinsic hematogenous macrophages, we designed a culture system to investigate the behavior of resident macrophages in vitro. A total of 75 adult male Lewis rats were used; 2. 5-cm-length sciatic nerve explants were harvested. There were three groups. In the culture groups, the nerve explants were incubated in Dulbecco's modified Eagle's medium (DMEM) only or in DMEM supplemented with 2 microm forskolin and 10 microg/ml pituitary extract (mitogenic medium for Schwann cells). In vivo predegenerated nerves and normal nerves were used as the positive and negative controls, respectively. The observation periods extended to 3 weeks. Hematoxylin and eosin (H&E) stain was employed to estimate overall cell number in nerve explants. Macrophages were labeled with ED1; S-100 immunostaining was used to evaluate the presence of Schwann cells during Wallerian degeneration. Trichrome stain and toluidine blue stain were used to visualize the fate of myelin. In the culture groups, the number of resident macrophages increased continuously, although there were significantly fewer resident macrophages than hematogenous macrophages after 3 days of Wallerian degeneration (P < 0.01). Morphologically, resident macrophages contained densely small ED1-positive granules within their cytoplasm, even at later stages of observation, whereas hematogenous macrophages contained typical large ED1-positive foam vacuoles characteristic of their mature phagocytic ability. The cellular activity of Schwann cells was well preserved in the mitogenic medium; however, myelin removal was not significantly enhanced as compared with the DMEM groups (P > 0.05). The clearance of myelin debris was shown to be incomplete in culture groups as compared with the complete removal of myelin debris in the in vivo groups. Resident macrophages were actively involved in Wallerian degeneration, but their phagocytic and proliferation ability was limited. Schwann cells played an adjunctive role during the removal of myelin debris.
    Microsurgery 01/2000; 20(5):255-61. · 1.62 Impact Factor
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    ABSTRACT: Previous studies demonstrated that the viability of nerve grafts had a positive effect on nerve regeneration, while the cold storage of nerve grafts obtained few viable cells at the later stage. The purpose of this study was to examine the cellular activities of Schwann cells and fibroblasts in cultured nerve grafts prior to transplantation. 2.5-cm long sciatic nerve grafts were harvested from 75 male Lewis rats. Two different media were utilized to culture the nerve grafts up to 3 weeks: Dulbecco's modified eagle medium (DMEM) only or DMEM supplemented with 2 microM forskolin and 10 microg/ml pituitary exact (mitogen medium for Schwann cells). In vivo predegenerated and normal nerve grafts were used as positive and negative controls, respectively. We employed a 5-bromo-2'-deoxyuridine (BrdU) incorporation method to evaluate the proliferating cells in the cultured nerve grafts. S-100 and vimentin immunostaining were used to estimate the presence of Schwann cells and fibroblasts in all nerve grafts at different intervals. The results showed that the proliferating cells increased progressively under culture conditions. The proliferating cells distributed evenly in small fascicles (average diameter 251 +/- 71.5 microm), whereas they appeared mainly in the margin of large fascicles (average diameter 624 +/- 87.3 microm). The mitogen medium stimulated Schwann cell multiplication more significantly in comparison with DMEM after 3 days of culture (P < 0.01), however, there were fewer fibroblasts present in the mitogen medium than in DMEM after 2 days of culture (P < 0.01). It is suggested that the viability of nerve grafts can be preserved under culture conditions. Furthermore, the cellular activity of the Schwann cells and fibroblasts in nerve grafts can be manipulated in in vitro Wallerian degeneration.
    Microsurgery 01/1999; 19(8):356-63. · 1.62 Impact Factor
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    ABSTRACT: In the early days of replantation surgery, if viability was restored the operation was judged a success. Nowadays restoration of viability alone is not sufficient to fulfill the criteria of successful replantation, which are as follows: Lack of severe systemic disturbances due to the replantation, a "functional extremity" according to the definition of Chen et al. (1978), no or little pain at the site of the replantation, good aesthetic results, and an acceptable length of time for rehabilitation and return to normal life. Successful replantation needs a therapy concept that is based on an exact definition of the amputation injury from the viewpoint of the amount of severance, the level of the amputation, and the type of amputation mechanism, complete knowledge of current replantation indications, and exact selection of patients amenable for replantation.
    Der Unfallchirurg 10/1997; 100(9):694-704. · 0.64 Impact Factor
  • P Brenner, F Lassner, M Becker, A Berger
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    ABSTRACT: Because of favourable survival rates in replantation surgery and a high standard of free tissue transfer the interval between injury and microsurgical reconstruction has become gradually shorter. The acute phase can be defined as the interval ranging from emergency procedures within 24 hours to urgent procedures done within 72 hours. Bearing in mind the infection rates that have been reported of 1.5% for the acute phase and 17.5% for the late phase, we should encourage emergency reconstructions. However, in most cases of upper extremity injuries, reconstruction with conventional flaps is possible. Between 1981 and 1995 we did 72 acute post-traumatic free tissue transfers to the upper extremity in our unit within 72 hours (urgently). There were no significant differences in the incidence of infections when acute were compared with urgent procedures. As a result we support the concept of urgent operations. The following advantages are to be considered: urgent operations allow a second look operation, the viability of the extremity can be assessed, and the reconstructive procedure can be planned more precisely. Last but not least, the procedure is done during the day time with better operating conditions.
    Scandinavian Journal of Plastic and Reconstructive Surgery and Hand Surgery 07/1997; 31(2):165-70. · 0.94 Impact Factor
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    ABSTRACT: Most cases of genital amputation represent an isolated penile amputation; the combined amputation of both penile and testes is reported very seldom. We describe a case of complete amputation of the external genitals with successful replantation and good functional outcome. The problem is analyzed with respect to operative strategy, ischemic periods, postoperative management, and psychiatric background. For the replantation of the testes, time frames are comparable to those for macroreplantations.
    Plastic &amp Reconstructive Surgery 05/1997; 99(4):1165-8. · 3.54 Impact Factor

Publication Stats

318 Citations
59.49 Total Impact Points

Institutions

  • 2000–2011
    • RWTH Aachen University
      • • Institute of Neuropathology
      • • Department of Plastic Surgery, Hand and Burns Surgery
      Aachen, North Rhine-Westphalia, Germany
  • 2008
    • University Hospital RWTH Aachen
      • Department of Neurology
      Aachen, North Rhine-Westphalia, Germany
  • 2002
    • Universität Witten/Herdecke
      • Chair of Plastic Surgery
      Witten, North Rhine-Westphalia, Germany
  • 1993–2000
    • Hannover Medical School
      • Department of Plastic, Hand and Reconstructive Surgery
      Hannover, Lower Saxony, Germany
  • 1994
    • Leibniz Universität Hannover
      Hanover, Lower Saxony, Germany
  • 1989
    • Deutsche Gesellschaft für Plastische und Wiederherstellungschirurgie e.V.
      Hanover, Lower Saxony, Germany