M. Jagodzinski

Tissue engineering of osteochondral constructs in vitro using bioreactors

Articular cartilage is a relatively simple tissue, but has a limited capacity of restoration. Tissue engineering is a promising field that seeks to accomplish the in vitro generation of complex, functional, 3-dimensional tissues. Various cell types and scaffolds have been tested for these purposes. The results of tissue engineered cartilage and bone are as yet inferior to native tissue. Strain and perfusion have been shown to stimulate cell proliferation and differentiation of various cell phenotypes. The perfect protocol to produce articular cartilage has not been defined yet. Bioreactors could provide the environment to engineer osteochondral constructs in vitro and to provide a stress protocol. The bioreactor has to provide an economically viable approach to automated manufacture of functional grafts under clinical aspects. Composite engineered tissues, like an engineered joint, represent a future goal. Cross-disciplinary approaches are necessary in order to succeed in engineering osteochondral grafts that provide adequate primary biomechanical stability and incorporate rapidly in vivo with histological appearance close to healthy osteochondral tissue. This review surveys current clinical and experimental concepts and discusses challenges and future expectations in this advancing field of regenerative medicine focusing human osteochondral constructs in bioreactors.

Lokalisation von TGF-β und PDGF und deren Bedeutung für die Pathogenese der Arthrofibrose

Arthrofibrosis is a disabling complication after knee trauma and surgery and is characterised clinically by joint stiffness. Due to an immune response, the proliferation of fibroblasts and synthesis of extracellular matrix proteins are increased. The cytokines transforming growth factor beta (TGF-beta) and platelet-derived growth factor (PDGF) are critical players in tissue fibrosis, stimulating cell proliferation and the production of various extracellular matrix proteins. Tissue samples from the infrapatellar fat pad and intercondylar synovia of seven patients (age 18-49 years) suffering from arthrofibrosis were taken at surgery. The mean interval between trauma and arthrolysis was 14.3 months. All samples were stained with haematoxylin and eosin, and monoclonal and polyclonal antibodies were applied for immunohistological localisation of TGF-beta and PDGF. The percentage of both cytokines was then analysed using an image analysis system. Tissue samples with no macroscopic pathology of the synovial tissue from eight patients for anterior cruciate ligament replacement served as controls. Immunostaining for TGF-beta and PDGF was found to be increased in arthrofibrotic tissue. Both cytokines could be detected subsynovially around inflammatory cells. The profibrotic cytokines TGF-beta and PDGF play an important role in the pathogenesis of arthrofibrosis. Both cytokines are key mediators of tissue fibrosis.

[Localisation of TGF-beta and PDGF and their relevance for the pathogenesis of arthrofibrosis].

Arthrofibrosis is a disabling complication after knee trauma and surgery and is characterised clinically by joint stiffness. Due to an immune response, the proliferation of fibroblasts and synthesis of extracellular matrix proteins are increased. The cytokines transforming growth factor beta (TGF-beta) and platelet-derived growth factor (PDGF) are critical players in tissue fibrosis, stimulating cell proliferation and the production of various extracellular matrix proteins. Tissue samples from the infrapatellar fat pad and intercondylar synovia of seven patients (age 18-49 years) suffering from arthrofibrosis were taken at surgery. The mean interval between trauma and arthrolysis was 14.3 months. All samples were stained with haematoxylin and eosin, and monoclonal and polyclonal antibodies were applied for immunohistological localisation of TGF-beta and PDGF. The percentage of both cytokines was then analysed using an image analysis system. Tissue samples with no macroscopic pathology of the synovial tissue from eight patients for anterior cruciate ligament replacement served as controls. Immunostaining for TGF-beta and PDGF was found to be increased in arthrofibrotic tissue. Both cytokines could be detected subsynovially around inflammatory cells. The profibrotic cytokines TGF-beta and PDGF play an important role in the pathogenesis of arthrofibrosis. Both cytokines are key mediators of tissue fibrosis.

Ist eine routinemäßige Implantatentfernung nach unfallchirurgischen Eingriffen sinnvoll

We present a literature review about implant removal after operative extremity and spine fracture treatment. The indication for implant removal procedures has become less frequent in recent years, but is still more common in Europe than for example in North America. The time required to perform a implant removal can easily exceed the planned amount. Implant removal can result in significant complications like soft tissue damage, fractures, infections, and other problems. Not only because of these problems, the decision on whether or not to remove the implant should be made with great care. Therefore good communication with the patient and thorough information about risks and benefits are essential.

RETRACTED ARTICLE: Entwicklung und biomechanische Testung einer femoralen Press-fit-Fixierung für Semitendinosus-/Gracilissehnen

PURPOSE The purpose of this study was to investigate press fit femoral fixation of hamstring tendons and to compare the mechanical properties with press fit patellar tendon bone (PTB) fixation. METHODS The PTB and hamstring tendons of 30 human cadavers (age: 55.8+/-18.0 years) were used as grafts. An outside-in press fit fixation with a knot in the semitendinosus and gracilis graft (SG-K) and an inside-out (SG-BI) and an outside-in fixation (SG-BO) with the tendons looped over a bone block were compared with a bone-patellar tendon (PT) press fit fixation in 30 bovine femora. The angle between the direction of force and bone tunnel was 60 degrees. The constructs underwent 20 cycles of loading between 60 and 260 N. Constructs were loaded until failure at a speed of 1 mm/sec. Graft fixation was analyzed in terms of maximum load to failure, stiffness and elongation during cyclic stretching. A video analysis of length changes was investigated. RESULTS There was a significant difference in the maximum load to failure. The SG-BI fixation was inferior to the other three techniques (Mann-WhitneyU-test, P<0.01). There was no difference in stiffness between the techniques. Length changes of PT-fixation from the first to the fifth loading cycle were significantly smaller compared with all other groups (0.73+/-0.58 mm). There was no significant difference between the groups from the 15th to the 20th cycle of cyclic loading. CONCLUSIONS Press fit fixation of hamstring grafts is technically challenging. However, pull-out forces for SG-O and SG-K were equivalent to BPT-graft fixation. Adequate preconditioning for all hamstring tendon press fit techniques is crucial.

[Intracondylar segment osteotomy: correction of intra-articular malalignment after fracture of the tibial plateau].

Intracondylar deformities after tibial plateau fractures are intra-articular deformities which present within the medial and/or lateral knee compartments. They exist either isolated or in combination with other extra-articular deformities and/or ligament problems. These deformities are complex problems and difficult to treat. While many treatment concepts exist for extra-articular deformities there is limited information available for intra-articular or even intracondylar deformities. Selecting the appropriate procedure for the approach, osteotomy, management of bone defects and cartilage damage is crucial. The authors describe the analysis, planning, treatment and clinical outcome for these rare but difficult problems and present step by step details of the surgical technique.ZusammenfassungIntrakondyläre Fehlstellungen nach Tibiakopffrakturen sind Fehlstellungen und Verwerfungen der Gelenkoberfläche innerhalb des lateralen und/oder medialen Gelenkkompartiments. Diese können allein oder in Kombination mit extraartikulären und/oder ligamentären Problemen an der proximalen Tibia auftreten, sie sind komplex in der Analyse und schwierig zu behandeln. Während für extraartikuläre Fehlstellungen zahlreiche Behandlungskonzepte mit entsprechenden Zugangs- und Osteotomieoptionen bestehen, gibt es für intraartikuläre und intrakondyläre Fehlstellungen kaum Literatur. Gerade für diese schwierige Situationen gilt es die geeigneten Vorgehensweisen für Zugang (Standard- oder erweiterte Zugänge), Osteotomie („open“ oder „closed wedge“, intraartikuläre und andere Osteotomien) und Knochenersatz (autologer Knochen, Ersatzstoffe, Knochendistraktion, Wachstumsfaktoren) sowie differenzierte Strategien zur Adressierung des Knorpelschadens (Änderung der mechanischen Achse, Mikrofrakturierung, Chondrozytentransplantation) differenziert und problemorientiert auszuwählen. Anhand von klinischen Beispielen werden Analyse, Planung, Indikationsstellung und chirurgische Vorgehensweise mit umfangreichen Bild- und Videomaterial anschaulich und „Schritt für Schritt“ demonstriert. Die dargelegten mittelfristigen Ergebnisse nach intraartikulärer, intrakondylärer Korrekturosteotomie nach fehlverheilter Tibiakopffraktur sind vielversprechend und verzögern aber verbauen nicht die später ggf. notwendige Knieendoprothese.AbstractIntracondylar deformities after tibial plateau fractures are intra-articular deformities which present within the medial and/or lateral knee compartments. They exist either isolated or in combination with other extra-articular deformities and/or ligament problems. These deformities are complex problems and difficult to treat. While many treatment concepts exist for extra-articular deformities there is limited information available for intra-articular or even intracondylar deformities. Selecting the appropriate procedure for the approach, osteotomy, management of bone defects and cartilage damage is crucial. The authors describe the analysis, planning, treatment and clinical outcome for these rare but difficult problems and present step by step details of the surgical technique.

Is routine implant removal after trauma surgery sensible

We present a literature review about implant removal after operative extremity and spine fracture treatment. The indication for implant removal procedures has become less frequent in recent years, but is still more common in Europe than for example in North America. The time required to perform a implant removal can easily exceed the planned amount. Implant removal can result in significant complications like soft tissue damage, fractures, infections, and other problems. Not only because of these problems, the decision on whether or not to remove the implant should be made with great care. Therefore good communication with the patient and thorough information about risks and benefits are essential.

Biomechanische Analyse der Press-fit-Fixierung von Kreuzbandtransplantaten

Press-fit fixation of anterior cruciate ligament autografts is an interesting technique because no hardware is necessary. A total of 168 cadaveric human patellar, quadriceps and hamstring tendons (average age 49.2 +/- 18.5 years) were used and 15 different fixation methods were tested. Constructs were cyclically stretched and then loaded until failure. Maximum load to failure, stiffness and elongation during failure testing and cyclical loading were compared. Some techniques showed comparable biomechanical qualities to interference screw fixation. All investigated double bundle fixation techniques were equal in terms of maximum load to failure, stiffness and elongation. All techniques exhibited greater elongation during initial cyclical loading. Some of the press-fit fixation techniques investigated exhibited comparable biomechanical properties and preconditioning of the constructs is critical. Press-fit fixation enhances tendon to bone contact at the entry of the bone tunnel to the joint.

[Ligament bracing--augmented cruciate ligament sutures: biomechanical studies of a new treatment concept].

BACKGROUND In the context of acute knee dislocations, suture repair of ruptured cruciate ligaments leads to good clinical results in 80% of cases. Disadvantages are low primary stability and subsequently secondary elongation of the sutured ligaments. In the present study, we compared primary stability of suture repair, reinforced by different suture augments, to cruciate ligament reconstruction. OBJECTIVE The concept of ligament bracing with transosseous suture repair of the cruciate ligaments and additional suture augmentation is biomechanically superior to cruciate ligament reconstruction. MATERIAL AND METHODS A total of 42 porcine knee joints divided into seven groups were examined. The stability of four different suture/augmentation combinations were compared to cruciate ligament reconstruction with human hamstring tendons. The investigational setup consisted of testing 1000 cycles with 20 N to 154 N load in a.-p. translation and 60° flexion. Elongation and load to failure were measured. RESULTS Neither reconstruction (3.13 ± 1.65 mm; 362 ± 51 N) nor augmented suture repair (1.89-2.5 mm; 464-624 N) achieved the primary stability of the intact cruciate ligament (0.63 ± 0.34 mm, 1012 ± 91 N). In comparison to ligament reconstruction, all four augmented suture repairs showed minor elongation in the cyclic test and a higher load to failure. The isolated suture repair showed poor results (6.79 ± 4.86 mm, 177 ± 73 N). CONCLUSION Augmented suture repair provides significantly higher stability compared with isolated suture repair and reconstruction with hamstring tendons. The concept of ligament bracing could be a promising future treatment option in acute knee dislocations. Clinical results remain to be seen.

„Ligament bracing“ – die augmentierte Kreuzbandnaht

BACKGROUND In the context of acute knee dislocations, suture repair of ruptured cruciate ligaments leads to good clinical results in 80% of cases. Disadvantages are low primary stability and subsequently secondary elongation of the sutured ligaments. In the present study, we compared primary stability of suture repair, reinforced by different suture augments, to cruciate ligament reconstruction. OBJECTIVE The concept of ligament bracing with transosseous suture repair of the cruciate ligaments and additional suture augmentation is biomechanically superior to cruciate ligament reconstruction. MATERIAL AND METHODS A total of 42 porcine knee joints divided into seven groups were examined. The stability of four different suture/augmentation combinations were compared to cruciate ligament reconstruction with human hamstring tendons. The investigational setup consisted of testing 1000 cycles with 20 N to 154 N load in a.-p. translation and 60° flexion. Elongation and load to failure were measured. RESULTS Neither reconstruction (3.13 ± 1.65 mm; 362 ± 51 N) nor augmented suture repair (1.89-2.5 mm; 464-624 N) achieved the primary stability of the intact cruciate ligament (0.63 ± 0.34 mm, 1012 ± 91 N). In comparison to ligament reconstruction, all four augmented suture repairs showed minor elongation in the cyclic test and a higher load to failure. The isolated suture repair showed poor results (6.79 ± 4.86 mm, 177 ± 73 N). CONCLUSION Augmented suture repair provides significantly higher stability compared with isolated suture repair and reconstruction with hamstring tendons. The concept of ligament bracing could be a promising future treatment option in acute knee dislocations. Clinical results remain to be seen.