Introduction: Vertically unstable sacral transforaminal fractures can be stabilized both with a transiliac internal fixator (TIFI) or iliosacral screws (IS). Goals: 1. comparison of radiological and clinical results between dorsal pelvic segment stabilization with TIFI, IS respectively, 2. evaluation and comparison of biomechanical parameters of TIFI and IS construct. Material and methods of clinical study: Prospective study, both TIFI and IS group had 32 patients, the most of injuries were assessed as type C1.3, only patients with a high-energy mechanism of injury were included. Radiological results were evaluated according Matta, clinical results according Majeed score, Pelvic Outcome Score. Categorical data were evaluated by two-sided Fishers exact test or Pearson's χ2 test, continuous data by Student's t-test, a test result with p <0.05 was considered as statistically significant. Methods of biomechanical study: Using CT images, finite element model of the pelvis was developed. Pohlemann type II fracture was simulated and fixed either with TIFI or two IS. The sacral base was loaded vertically (250-500 N), displacement magnitudes on medial and lateral fracture surface and the maximum bone stress were calculated. The intact pelvis was used as a reference. Stiffness was determined by linear...

O fixador esquelético externo circular foi desenvolvido durante a guerra fria na Rússia, pelo Professor Gavril Abramovich Ilizarov. Esse tipo de fixação ganhou espaço como alternativa à fixação interna, devido a sua versatilidade e às suas características biomecânicas que otimizam a formação do calo ósseo. O objetivo desse estudo foi avaliar o fixador esquelético externo circular como método de fixação para fraturas metafisárias de rádio e tíbia de cães atendidos no Hospital de Clínicas Veterinárias da UFRGS. Os resultados a respeito do tipo e frequência de complicações associados a essa técnica foram documentados. No total 16 animais cumpriram os critérios para entrar no estudo sendo sete fêmeas e nove machos. A idade média dos animais foi de 50,87 ± 57,01 meses com peso médio dos animais foi de 8,6 ± 6,95kg. Três (18%) animais apresentaram fratura de tíbia e fíbula e treze (82%) fraturas de rádio e ulna. O aparelho de fixação esquelética utilizado consistiu de um aro proximal 5/8 e dois aros distais inteiros, com dois fios em cada anel. Os fios foram colocados de maneira divergente o mais próximo possível de 90°. O aparelho pesou em média 128 ± 49g, representando em média 4,09 ± 3,22% do peso do animal. O tempo médio de cirurgia foi de 115 ± 32 minutos. O tempo médio de permanência com o aparelho de fixação esquelética externa circular foi de 81,69 ± 23,14 dias. Entre as complicações encontradas estão: tratos de drenagem ao redor dos fios (37,5%), miíase (6,25%), encurtamento dos músculos flexores do antebraço (6,25%), hemorragia associada ao local de passagens dos pinos (6,25%) e quebra do fio com deslocamento do fixador levando a necessidade de sua remoção (6,25%). Não houve diferença estatística entre os tempos cirúrgicos necessários para a osteossíntese de rádio e tíbia. Não houve correlação entre as variáveis: tempo decorrido do trauma até a cirurgia e tempo de duração da cirurgia; tempo decorrido do trauma até a cirurgia e tempo de permanência com o aparelho de fixação esquelética externa circular; peso do animal e duração da cirurgia; proporção do peso do circular em relação ao peso do animal e o tempo de permanecia com o circular. Houve correlação positiva estatisticamente significativa entre as variáveis: duração da cirurgia e tempo de permanência com o aparelho de fixação esquelética externa circular. Essa modalidade de tratamento representa uma opção cirúrgica atrativa para a correção de fraturas de rádio e tíbia em cães, entretanto, devido à possibilidade complicações e necessidade de cuidados pós-operatórios intensivos uma seleção acurada dos pacientes e proprietários deve ser realizada previamente à cirurgia. / The circular external skeletal fixator was developed during the Cold War in Russia, by Professor Gavril Abramovich Ilizarov. This kind of fixation took place as an alternative to internal fixation, due to its versatility and its biomechanical characteristics that improves the formation of callus. The aim of this study was to evaluate the circular external skeletal fixator as a method of fixation for fractures of the radius and tibia of dogs treated at the Veterinary Teaching Hospital of UFRGS, corroborating the results, the type and frequency of complications associated with this technique. Sixteen animals met the criteria to participate on the study, seven females and nine males. The average age of the animals was 50.87 ± 57.01 months. The average weight of the animals was 8.6 ± 6.95 kg. Three (18%) animals showed fracture of tibia and fibula and thirteen (82%) fractures of the radius and ulna. The circular external skeletal fixation frame used consisted of a proximal ring ⅝ and two full distal rings, with two wires in each ring. The wires were placed divergently as close as possible to 90 °. The frame weighed on average 128 ± 49g, representing average 4.09 ± 3.22% of the weight of the animal. The mean time of the surgery was 115 ± 32 minutes. The average time spent with the circular was 81.69 ± 23.14 days. Among the complications found are drainage tracts around the pins (37.5%), myiasis (6.25%), shortening of the forearm flexors (6.25%), hemorrhage associated with the location of pins passages (6, 25%) and breakage of the device wire with displacement of the frame leading to its removal (6.25%). There was no statistical difference between the times required for the surgical fixation of the radius and tibia. There was no correlation between the variables: time elapsed from trauma to surgery and duration of surgery, time elapsed from trauma to surgery and time spent with the circular external skeletal fixation; animal weight and duration of surgery; the proportion of the circular weight in relation to the weight of the animal and the time remained with the circular. There was statistically significant positive correlation between the variables: duration of the surgery and the permanency with the circular external skeletal fixation. This treatment modality represents an attractive surgical option for fractures correction of the radius and tibia in dogs, however, due to possible complications and need for intensive post operative care accurate selection of patients and owners should be performed prior to surgery.

O fixador esquelético externo circular foi desenvolvido durante a guerra fria na Rússia, pelo Professor Gavril Abramovich Ilizarov. Esse tipo de fixação ganhou espaço como alternativa à fixação interna, devido a sua versatilidade e às suas características biomecânicas que otimizam a formação do calo ósseo. O objetivo desse estudo foi avaliar o fixador esquelético externo circular como método de fixação para fraturas metafisárias de rádio e tíbia de cães atendidos no Hospital de Clínicas Veterinárias da UFRGS. Os resultados a respeito do tipo e frequência de complicações associados a essa técnica foram documentados. No total 16 animais cumpriram os critérios para entrar no estudo sendo sete fêmeas e nove machos. A idade média dos animais foi de 50,87 ± 57,01 meses com peso médio dos animais foi de 8,6 ± 6,95kg. Três (18%) animais apresentaram fratura de tíbia e fíbula e treze (82%) fraturas de rádio e ulna. O aparelho de fixação esquelética utilizado consistiu de um aro proximal 5/8 e dois aros distais inteiros, com dois fios em cada anel. Os fios foram colocados de maneira divergente o mais próximo possível de 90°. O aparelho pesou em média 128 ± 49g, representando em média 4,09 ± 3,22% do peso do animal. O tempo médio de cirurgia foi de 115 ± 32 minutos. O tempo médio de permanência com o aparelho de fixação esquelética externa circular foi de 81,69 ± 23,14 dias. Entre as complicações encontradas estão: tratos de drenagem ao redor dos fios (37,5%), miíase (6,25%), encurtamento dos músculos flexores do antebraço (6,25%), hemorragia associada ao local de passagens dos pinos (6,25%) e quebra do fio com deslocamento do fixador levando a necessidade de sua remoção (6,25%). Não houve diferença estatística entre os tempos cirúrgicos necessários para a osteossíntese de rádio e tíbia. Não houve correlação entre as variáveis: tempo decorrido do trauma até a cirurgia e tempo de duração da cirurgia; tempo decorrido do trauma até a cirurgia e tempo de permanência com o aparelho de fixação esquelética externa circular; peso do animal e duração da cirurgia; proporção do peso do circular em relação ao peso do animal e o tempo de permanecia com o circular. Houve correlação positiva estatisticamente significativa entre as variáveis: duração da cirurgia e tempo de permanência com o aparelho de fixação esquelética externa circular. Essa modalidade de tratamento representa uma opção cirúrgica atrativa para a correção de fraturas de rádio e tíbia em cães, entretanto, devido à possibilidade complicações e necessidade de cuidados pós-operatórios intensivos uma seleção acurada dos pacientes e proprietários deve ser realizada previamente à cirurgia. / The circular external skeletal fixator was developed during the Cold War in Russia, by Professor Gavril Abramovich Ilizarov. This kind of fixation took place as an alternative to internal fixation, due to its versatility and its biomechanical characteristics that improves the formation of callus. The aim of this study was to evaluate the circular external skeletal fixator as a method of fixation for fractures of the radius and tibia of dogs treated at the Veterinary Teaching Hospital of UFRGS, corroborating the results, the type and frequency of complications associated with this technique. Sixteen animals met the criteria to participate on the study, seven females and nine males. The average age of the animals was 50.87 ± 57.01 months. The average weight of the animals was 8.6 ± 6.95 kg. Three (18%) animals showed fracture of tibia and fibula and thirteen (82%) fractures of the radius and ulna. The circular external skeletal fixation frame used consisted of a proximal ring ⅝ and two full distal rings, with two wires in each ring. The wires were placed divergently as close as possible to 90 °. The frame weighed on average 128 ± 49g, representing average 4.09 ± 3.22% of the weight of the animal. The mean time of the surgery was 115 ± 32 minutes. The average time spent with the circular was 81.69 ± 23.14 days. Among the complications found are drainage tracts around the pins (37.5%), myiasis (6.25%), shortening of the forearm flexors (6.25%), hemorrhage associated with the location of pins passages (6, 25%) and breakage of the device wire with displacement of the frame leading to its removal (6.25%). There was no statistical difference between the times required for the surgical fixation of the radius and tibia. There was no correlation between the variables: time elapsed from trauma to surgery and duration of surgery, time elapsed from trauma to surgery and time spent with the circular external skeletal fixation; animal weight and duration of surgery; the proportion of the circular weight in relation to the weight of the animal and the time remained with the circular. There was statistically significant positive correlation between the variables: duration of the surgery and the permanency with the circular external skeletal fixation. This treatment modality represents an attractive surgical option for fractures correction of the radius and tibia in dogs, however, due to possible complications and need for intensive post operative care accurate selection of patients and owners should be performed prior to surgery.

O fixador esquelético externo circular foi desenvolvido durante a guerra fria na Rússia, pelo Professor Gavril Abramovich Ilizarov. Esse tipo de fixação ganhou espaço como alternativa à fixação interna, devido a sua versatilidade e às suas características biomecânicas que otimizam a formação do calo ósseo. O objetivo desse estudo foi avaliar o fixador esquelético externo circular como método de fixação para fraturas metafisárias de rádio e tíbia de cães atendidos no Hospital de Clínicas Veterinárias da UFRGS. Os resultados a respeito do tipo e frequência de complicações associados a essa técnica foram documentados. No total 16 animais cumpriram os critérios para entrar no estudo sendo sete fêmeas e nove machos. A idade média dos animais foi de 50,87 ± 57,01 meses com peso médio dos animais foi de 8,6 ± 6,95kg. Três (18%) animais apresentaram fratura de tíbia e fíbula e treze (82%) fraturas de rádio e ulna. O aparelho de fixação esquelética utilizado consistiu de um aro proximal 5/8 e dois aros distais inteiros, com dois fios em cada anel. Os fios foram colocados de maneira divergente o mais próximo possível de 90°. O aparelho pesou em média 128 ± 49g, representando em média 4,09 ± 3,22% do peso do animal. O tempo médio de cirurgia foi de 115 ± 32 minutos. O tempo médio de permanência com o aparelho de fixação esquelética externa circular foi de 81,69 ± 23,14 dias. Entre as complicações encontradas estão: tratos de drenagem ao redor dos fios (37,5%), miíase (6,25%), encurtamento dos músculos flexores do antebraço (6,25%), hemorragia associada ao local de passagens dos pinos (6,25%) e quebra do fio com deslocamento do fixador levando a necessidade de sua remoção (6,25%). Não houve diferença estatística entre os tempos cirúrgicos necessários para a osteossíntese de rádio e tíbia. Não houve correlação entre as variáveis: tempo decorrido do trauma até a cirurgia e tempo de duração da cirurgia; tempo decorrido do trauma até a cirurgia e tempo de permanência com o aparelho de fixação esquelética externa circular; peso do animal e duração da cirurgia; proporção do peso do circular em relação ao peso do animal e o tempo de permanecia com o circular. Houve correlação positiva estatisticamente significativa entre as variáveis: duração da cirurgia e tempo de permanência com o aparelho de fixação esquelética externa circular. Essa modalidade de tratamento representa uma opção cirúrgica atrativa para a correção de fraturas de rádio e tíbia em cães, entretanto, devido à possibilidade complicações e necessidade de cuidados pós-operatórios intensivos uma seleção acurada dos pacientes e proprietários deve ser realizada previamente à cirurgia. / The circular external skeletal fixator was developed during the Cold War in Russia, by Professor Gavril Abramovich Ilizarov. This kind of fixation took place as an alternative to internal fixation, due to its versatility and its biomechanical characteristics that improves the formation of callus. The aim of this study was to evaluate the circular external skeletal fixator as a method of fixation for fractures of the radius and tibia of dogs treated at the Veterinary Teaching Hospital of UFRGS, corroborating the results, the type and frequency of complications associated with this technique. Sixteen animals met the criteria to participate on the study, seven females and nine males. The average age of the animals was 50.87 ± 57.01 months. The average weight of the animals was 8.6 ± 6.95 kg. Three (18%) animals showed fracture of tibia and fibula and thirteen (82%) fractures of the radius and ulna. The circular external skeletal fixation frame used consisted of a proximal ring ⅝ and two full distal rings, with two wires in each ring. The wires were placed divergently as close as possible to 90 °. The frame weighed on average 128 ± 49g, representing average 4.09 ± 3.22% of the weight of the animal. The mean time of the surgery was 115 ± 32 minutes. The average time spent with the circular was 81.69 ± 23.14 days. Among the complications found are drainage tracts around the pins (37.5%), myiasis (6.25%), shortening of the forearm flexors (6.25%), hemorrhage associated with the location of pins passages (6, 25%) and breakage of the device wire with displacement of the frame leading to its removal (6.25%). There was no statistical difference between the times required for the surgical fixation of the radius and tibia. There was no correlation between the variables: time elapsed from trauma to surgery and duration of surgery, time elapsed from trauma to surgery and time spent with the circular external skeletal fixation; animal weight and duration of surgery; the proportion of the circular weight in relation to the weight of the animal and the time remained with the circular. There was statistically significant positive correlation between the variables: duration of the surgery and the permanency with the circular external skeletal fixation. This treatment modality represents an attractive surgical option for fractures correction of the radius and tibia in dogs, however, due to possible complications and need for intensive post operative care accurate selection of patients and owners should be performed prior to surgery.

This diploma thesis aims to create a stress strain analysis of Orthofix external fixator applied to lower limb. The introduction summarizes the background research in available scientific publications, targetting the alternatives of treatment, namely application and fixation solutions of long bones. Furthermore parametric models of the fixator and tibia are created in CAD system CATIA. The fixator model enables to create different geometric variations simulating possible fixator settings and moment load in the range of 1-10 Nm. These geometric and loading states of fixator are solved via FEM in ANSYS. Single versions of the states of Orthofix fixator are then subjected to the stress strain analysis.

Distal radius fractures are one of the most common fractures. In case of a complicated fracture, it is necessary to proceed with surgical treatment using an internal plate fixator. The aim of this thesis was to perform a stress-strain analysis of an internal plate fixator attached to the distal radius using bone screws. Computational modeling using finite element method was used to assess the mechanical interactions among the individual elements of this system. The stress-strain analysis was performed for three different types of fixation in geometry models including a distal radius fracture and a healed distal radius and for three different types of loads. In the evaluation of the results, the influence of the type of load and the influence of the healing of the bone tissue were assessed. For the bending load, which was the most critical, the yield strength was not exceeded in the plate or in the bone screws, and therefore irreversible plastic deformation of the material did not occur.

Introduction: Vertically unstable sacral transforaminal fractures can be stabilized both with a transiliac internal fixator (TIFI) or iliosacral screws (IS). Goals: 1. comparison of radiological and clinical results between dorsal pelvic segment stabilization with TIFI, IS respectively, 2. evaluation and comparison of biomechanical parameters of TIFI and IS construct. Material and methods of clinical study: Prospective study, both TIFI and IS group had 32 patients, the most of injuries were assessed as type C1.3, only patients with a high-energy mechanism of injury were included. Radiological results were evaluated according Matta, clinical results according Majeed score, Pelvic Outcome Score. Categorical data were evaluated by two-sided Fishers exact test or Pearson's χ2 test, continuous data by Student's t-test, a test result with p <0.05 was considered as statistically significant. Methods of biomechanical study: Using CT images, finite element model of the pelvis was developed. Pohlemann type II fracture was simulated and fixed either with TIFI or two IS. The sacral base was loaded vertically (250-500 N), displacement magnitudes on medial and lateral fracture surface and the maximum bone stress were calculated. The intact pelvis was used as a reference. Stiffness was determined by linear...

Bei Patienten, die auf Grund einer schweren Beckenverletzung hämodynamisch instabil sind, ist die primäre Stabilisierung des Beckens und damit die Reduktion des intrapelvinen Volumens entscheidend für den Erfolg der weiteren Therapie. Die Beckenzwinge hat sich als Notfallmaßnahme bewährt, erfordert jedoch in den meisten Fällen eine weitere operative Versorgung. Dieser Sekundäreingriff bedingt in vielen Fällen bei traumatisch geschädigten Weichteilen zusätzliche Wundheilungsstörungen. Ein weiteres Verfahren, der ventrale Fixateur externe, zeichnet sich durch einfache und schnelle Montage bei nur geringem Weichteilschaden aus. In vielen Fällen ist jedoch keine für die Mobilisierung ausreichende biomechanische Stabilisierung des vertikal instabilen dorsalen Beckenringes zu erreichen. Anhand biomechanischer Überlegungen wurde ein neuer schräg dorsaler Beckenfixateur für Becken- C-Verletzungen entwickelt, der die Vorteile des supraacetabulären Fixateur externe nutzt und dabei den hinteren Beckenring von ventral mit einer der Beckenzwinge nahe kommenden Effektivität stabilisieren kann. Er ermöglicht bereits initial eine minimal invasive sowie definitive Stabilisierung des dorsalen Beckenrings. Mehrere Variationen mit zwei unterschiedlichen Pin- Applikationsformen dieses asymmetrischen Fixateurs wurden getestet. In einer zweiten Testreihe wurde die in der ersten Testreihe favorisierte Version des neuen schräg dorsalen Fixateurs mit dem Supraacetabulärem Fixateur externe und der Beckenzwinge (ACE) verglichen. Beide Testreihen erfolgten an Kunststoff-Beckenmodellen im Einbeinstand in einer Materialprüfmaschine. Als Instabilitätsmodell dienten Verletzungen vom Typ C1.2 sowie C1.3 entsprechend der AO Klassifikation. In den Testreihen wurde kein signifikanter Unterschied des neuen verspannten schräg dorsalen Fixateurs zur Beckenzwinge gefunden. Er war jedoch deutlich stabiler als das unverspannte Modell oder der supraacetabuläre Fixateur allein. / In haemodynamically unstable patients with an unstable pelvic ring injury the primary stabilisation of the pelvis and thus reduction of pelvic volume is important for the success of the treatment. The pelvic C-clamp is an approved emergency device for these unstable pelvic ring injuries. A secondary procedure though is necessary in most of the cases with a big rate of wound problems in already traumatized soft tissue areas. The ventrally placed external fixator is a simple and quick procedure with little soft tissue damage. Though primary stability is sufficient even for C-type injuries, biomechanic stability of the posterior pelvic ring is often insufficient for mobilization. Based on biomechanic considerations, a new dorsal oblique pelvic external fixator was developed for pelvic C-type injuries. With the advantages of the supraacetabular fixator and two additional Schanz screws the ventral fixator should stabilize the posterior pelvic ring with comparable stability to the pelvic C-clamp. A primary and already definitive minimal invasive stabilization of the posterior pelvic ring was the aim. In the first series several variations of this asymmetric fixator with two different Schanz screw applications were tested biomechanically. In a second series the favourite version was tested versus the supraacetabular fixator and the pelvic C-clamp. Both of the biomechanic test series were performed with artificial pelves in the one leg stance model in the material testing machine. SI disruption and sacral fracture were the posterior instability types in 6 pelves each. There was no statistically significant difference between the dorsal oblique fixator and the pelvic C-clamp. But the new fixator was significantly more stable than the supraacetabular fixator or the new fixator without pretension.

Bei der internen, extramedullären Osteosynthese des distalen Femurs, auf die sich diese Arbeit fokussiert, haben sich in den letzten Jahren interessante Entwicklungen vollzogen. Ausgehend von unzufriedenstellenden Komplikationsraten wurden neue Wege in der Versorgung dieser schwierigen Frakturen gesucht. Osteosynthesematerialien, Repositionstechniken, die Technik der Implantatplatzierung und die Implantate selbst, bei denen die Entwicklung zu winkelstabilen Systemen gegangen ist, haben sich grundlegend geändert. Die vorliegende Arbeit analysiert in einer retrospektiven Studie distale Femurfrakturen, die zwischen dem 1.1.1995 und 31.9.2000 entweder mit einem Fixateur interne (LISS) oder mit der konventionellen Plattenosteosynthese versorgt wurden. In die Studie konnten 51 Patienten mit 54 distalen Femurfrakturen eingeschlossen werden. Die Infektionsrate war in der LISS-Gruppe (0% versus 11,1%) nichtsignifikant geringer, die Rate der verzögerten Frakturheilungen war nichtsignifikant höher. Die einzige verzögerte Frakturheilung (LISS-Gruppe), die einer sekundären chirurgischen Intervention bedurfte, wurde bei einer Patientin mit einem großen Knochendefekt gesehen, der ohne primäre Spongiosaplastik therapiert worden war. Pseudarthrosen traten in beiden Gruppen nicht auf. Die Rate des Materialversagens unterschied sich nicht signifikant. Beim LISS kam es nicht, wie bei den konventionellen Implantaten zu sekundären Repositionsverlusten, es wurden aber im Anfang der klinischen Einführung proximale Schraubenausrisse aufgrund einer Fehlplatzierung gesehen. Es konnte gezeigt werden, dass es durch die Verwendung des LISS und die indirekten Repositionstechniken zu keiner Zunahme der Achsfehlstellungen oder der Operationszeit kam. Die funktionellen Einzelergebnisse und die Punktzahl der erhobenen Scores (Neer-Score und Lysholm-Score) unterschieden sich nicht signifikant. / Internal, extramedullary osteosynthesis of distal femoral fractures which are focussed on in this study has been influenced by interesting developments in recent years. Driven by unsatisfying complication rates new fracture treatments have been looked for. Osteosynthesis materials, reduction techniques, techniques of implant placement and implants themselves - where development went to angular stable systems - have changed decisively. This study analyzes in a retrospective setting distal femoral fractures which were treated between 1.1.1995 and 31.9.2000 either with an internal fixator (LISS) or with conventional plate osteosynthesis. In this study 51 patients with 54 distal femoral fractures could be included. The Infection rate was non significantly lower in the LISS group (0% versus 11,1%), the rate of delayed union was non significantly higher. The only delayed union in the LISS group which needed secondary surgical intervention was seen in a patient with considerate bone loss which was not treated by primary bone grafting. Non-unions were not seen in either group. The rate of implant failure did not differ significantly. In the LISS group no secondary loss of reduction (like in the group with conventional plate osteosyntesis) was seen but proximal screw pull out due to malplacement was reported in the beginning of clinical introduction. It could be demonstrated the LISS and indirect reduction leading not to a higher rate of malalignement nor to prolonged theatre times. Functional results and the point score of the Neer Score and the Lysholm Score showed no significant difference.

Die Tibiaschaftfraktur ist eine häufig auftretende Verletzung. Der Fixateur externe findet bei der Versorgung von Tibiafrakturen große Verwendung. Die Variabilität und Anpassung an die individuelle Patientensituation stellen den Vorteil der Osteosynthese dar. Gleichzeitig ist unklar, ob und inwiefern die Montageebene die Frakturheilung beeinflusst. Interfragmentäre Bewegungen (IFM) bestimmen die Quantität und Qualität der Kallusbildung. IFM werden wiederum durch die Fixateurmontageebene bedingt. Diese Studie wurde vorgelegt, um den Einfluss der Montageebene auf die Frakturheilung zu bestimmen. Zwei identisch konfigurierte monolaterale Fixateurs externes mit medialer und anteromedialer Montageebene wurden bezüglich ihres Heilungspotentials an der Schafstibia verglichen. IFM und Bodenreaktionsparameter wurden während des neunwöchigen Heilungsverlaufs in vivo ermittelt. Die Knochenkonsolidierung wurde radiologisch und biomechanisch evaluiert. Allein die Änderung der Montageebene führte zu einer Modifikation der IFM. Der Unterschied der IFM war nur in der initialen Heilungsphase signifikant. Diese initialen Unterschiede beeinflussten jedoch bei nicht signifikant unterschiedlicher Gewichtsbelastung die Kallusbildung. Die Gruppe mit anteromedial montierten Fixateur zeigte initial höhere IFM und bewirkte einen radiologisch größeren Kallusdurchmesser und eine biomechanisch größere Kallussteifigkeit im Sinne einer weiter fortgeschrittenen Heilungsphase. Diese erzielten Heilungsergebnisse demonstrieren die Sensitivität der Montageebene und die Bedeutung der initialen biomechanischen Bedingungen, die den Kurs der Frakturheilung beeinflussen. Darum sollte der Montageebene und der dadurch bedingten initialen mechanischen Osteosynthesestabilität in der klinischen Frakturversorgung mehr Beachtung geschenkt werden. / Fractures of the tibia are commonly encountered problems. One of the most common osteosyntheses used to stabilise tibial fractures are external fixators. The fixator allows great freedom in configuration, especially with regard to its mounting plane. Whether and how the mounting plane influences the healing process is still unclear. Interfragmentary movements (IFM) affect the quality and quantity of callus formation. The mounting plane of monolateral external fixators may give direction to those movements. The presented study aimed to determine the influence of the fixator mounting plane on fracture healing. Identically configured fixators were mounted either medially or anteromedially on a standardised ovine tibial diastasis model with regard to their fracture healing potential. IFM and ground reaction forces were evaluated in vivo during a nine week period. Biomechanical and radiological parameters described the bone healing process. Changing only the mounting plane led to a modification of IFM in the initial healing phase. The difference in IFM between the groups was only significant during the first post-operative period. However, these initial differences in mechanical conditions influenced callus tissue formation. The group with the anteromedially mounted fixator, initially showing significantly more IFM, ended up with a radiologically bigger callus diameter and a biomechanically higher callus stiffness as a result of advanced fracture healing. This demonstrates that the initial phase of healing is sensitive to mechanical conditions and influences the course of healing. Therefore, initial mechanical stability of an osteosynthesis should be considered an important factor in clinical fracture treatment.