N. M. Meenen

RGD-peptides for tissue engineering of articular cartilage

One keypoint in the development of a biohybrid implant for articular cartilage defects is the specific binding of cartilage cells to a supporting structure. Mimicking the physiological adhesion process of chondrocytes to the extracellular matrix is expected to improve cell adhesion of in vitro cultured chondrocytes. Our approach involves coating of synthetic scaffolds with tailor-made, cyclic RGD-peptides, which bind to specific integrin receptors on the cell surface. In this study we investigated the expression pattern of integrins on the cell surface of chondrocytes and their capability to specifically bind to RGD-peptide coated materials in the course of monolayer cultivation. Human chondrocytes expressed integrins during a cultivation period of 20 weeks. Receptors proved to be functionally active as human and pig chondrocytes attached to RGD-coated surfaces. A competition assay with soluble RGD-peptide revealed binding specificity to the RGD-entity. Chondrocyte morphology changed with increasing amounts of cyclic RGD-peptides on the surface.

Perfusion cultures and modelling of oxygen uptake with three-dimensional chondrocyte pellets

Chondrocyte pellets were cultivated in a perfused flow chamber and supplied with medium by a constant flow rate from a conditioning vessel. In this conditioning vessel the medium was aerated and used medium was exchanged semi-continuously. The higher amount of DNA and glycosaminoglycane (GAG) in these pellets compared to control cultures under stationary conditions showed a positive effect of the reactor system, compared to standard culture conditions. A diffusion reaction model was applied to calculate the oxygen uptake of the cell pellet and to describe the oxygen profile within the pellet. The model included diffusion within the cell pellet and oxygen uptake of the cells. Calculated data were compared to experimental data obtained by tissue engineered chondrocyte cell pellets. Model calculations agreed rather well with experimental data.

Langzeitergebnisse nach Anwendung einer porösen Hydroxylapatitkeramik (Endobon) zur operativen Versorgung von Tibiakopffrakturen

ZusammenfassungEndobon, eine poröse Hydroxylapatitkeramik bovinen Ursprungs, ist seit 1989 als Knochenersatzmittel zur Therapie von Knochendefekten zugelassen. In der Literatur sind gegenwärtig keine Langzeitdaten zur klinischen Anwendung von Endobon verfügbar.Um die Langzeiteffekte von Endobon zu evaluieren, wurden im Rahmen einer retrospektiven Studie 35 Patienten mit Tibiakopffrakturen untersucht, die von 1992–1997 in unserer Klinik behandelt wurden. Nach Anhebung und Rekonstruktion der Gelenkfläche wurden die metaphysären Defekte mit Endobon gefüllt und die Frakturen durch Plattenosteosynthese stabilisiert. Von den eingeschlossenen Patienten konnten im Januar 2000 insgesamt 26 zu einer Nachuntersuchung einbestellt werden. Ein mechanisches Versagen der implantierten Keramiken mit sekundärem Korrekturverlust wurde nicht beobachtet. Einzelne Biopsate zeigten, dass das eingebrachte Material nach 18 Monaten vollständig ossär integriert wurde. Radiologische Anzeichen für eine Auslockerung, Dislokation, Sinterung oder Fraktur der Keramiken wurden auch nach Entfernung des Osteosynthesematerials nicht gesehen.Diese Daten zeigen, dass Endobon im Langzeitverlauf mechanisch stabil ist und bei entsprechender Indikation eine gute Alternative zur autogenen Spongiosaplastik darstellt.AbstractEndobon is a porous hydroxyapatite ceramic which has been used as a bone replacement substitute since 1989. Currently there are no data available reflecting long-term effects of Endobon in human bone grafting.In order to assess such effects 35 patients with fractures of the proximal tibia were studied retrospectively over a period up to 91 months. The metaphyseal defects were filled by Endobon and fractures were stabilized by internal plate fixation subsequently. A secondary loss of reduction due to mechanical failure of the bone replacement material did not occur even after removal of metal implants. No histological signs of resorption or degradation could be found 18 months after application.Our data show that Endobon provides good mechanical properties during a long term follow-up and can be recommended as a suitable therapeutic option versus cancellous bone graft.

Healing Predictors of Stable Juvenile Osteochondritis Dissecans Knee Lesions After 6 and 12 Months of Nonoperative Treatment

Background: Nonoperative treatment of stable juvenile osteochondritis dissecans (JOCD) lesions of the knee fails in up to 50% of cases. Healing predictors are needed to identify potential failures and thus determine treatment options. Purpose: A predictive model for healing potential after 6 and 12 months of nonoperative treatment of stable JOCD lesions based on sensitive magnetic resonance imagining (MRI) follow-up measurements was developed. Study Design: Cohort study (diagnosis); Level of evidence, 2. Methods: A retrospective cross-sectional study was conducted to analyze 62 white patients (76 stable JOCD lesions) who were initially treated by restriction of activity until they were free of pain. The primary end point was healing investigated on MRI with follow-up measurements after 6 and 12 months of nonoperative treatment. Multivariate logistic regression was used to determine the influence of age, sex, JOCD lesion size, clinical symptoms, and the occurrence of cystlike lesions (CLLs) on healing potential. Additionally, optimal prognostic cutoffs were defined to differentiate failures from nonfailures. Results: After 6 months of nonoperative treatment, 51 (67%) of 76 stable JOCD lesions showed no progression toward healing or showed signs of instability. Normalized lesion width and area and CLL occurrence differed significantly between failures and nonfailures (P < .05). A multivariate logistic regression best-predictors model that included age, CLL size, and normalized lesion width best predicted healing after 6 months and resulted in an area under the curve (AUC) of 0.779 (P < .001). A cutoff at 48% healing probability, as predicted by a nomogram based on age, normalized lesion width, and CLL size, differentiated failures from nonfailures (sensitivity, 60.0%; specificity, 83.7%). After 12 months, 37 lesions (49%) had progressed toward healing, and the sole observation of CLL size had the highest predictive validity (AUC, 0.766). The optimal cutoff was a healing probability of 61% (lesion size, 1.3 mm; sensitivity, 70.3%; specificity, 74.1%). Conclusion: A 6-month period of nonoperative treatment with or without casting might be appropriate if the healing potential is >48%. A 12-month period of nonoperative treatment may be successful if the CLL is <1.3 mm in length as assessed on MRI.

Present and Future Therapies of Articular Cartilage Defects

AbstractBackground: Until today, no universally successful therapy to treat substantial articular cartilage defects has been available. Numerous therapeutic approaches can only improve clinical symptoms of joint lesions, but cannot stimulate the regenerative and reactive capacity of the biological tissue in the defect, and, thus, cannot restore an articular surface capable of functional load bearing. Some other therapeutic options promised impressing results at the beginning, but did not withstand the process of a closer investigation. Even after laborious, invasive and expensive therapies, patients still complain about pain, joint effusions, restricted movement, or articular blockage. Established and Novel Therapies: The aim of all therapeutic procedures to treat patients with damaged articular cartilage is to reconstruct the integrity of the articular cartilage surface in order to enable them to live an unrestricted painless professional and private life. This article gives an overview of the clinically established procedures, their indications and the present long-term results, as well as a crucial look on the limitations of each approach. Novel therapies, which integrate molecular biology techniques and tissue engineering into transplantation surgery, are introduced and analyzed in terms of their capability and future potential.

Fracturoscopy is Superior to Fluoroscopy in the Articular Reconstruction of Complex Tibial Plateau Fractures-An Arthroscopy Assisted Fracture Reduction Technique.

Objective: To analyze the anatomic accuracy of fracture reduction controlled by fluoroscopy as compared with arthroscopically assisted reduction (“fracturoscopy”) in patients with complex tibial plateau fractures (AO/OTA 41-C). Quality of fracturoscopy-guided reduction was checked with postoperative computed tomography. Design: Prospective observational study. Setting: Urban level 1 trauma center. Patients: Seventeen consecutive patients, with a complex, bicondylar tibial plateau fracture. Intervention: The intraoperative, open insertion of an arthroscope (2.4-mm or 2.8-mm optics), to visualize the articular surface and fracture reduction. Main Outcome Measurements: Ability to detect residual fracture depression or gap after previous open reduction under fluoroscopic guidance. Results: An open fracture reduction with fluoroscopic guidance was performed in all cases. In 7 cases, open reduction and fluoroscopy resulted in satisfactory fracture reduction (fluoroscopy group). In 10 of 17 cases, subsequent “fracturoscopy” showed persistent fracture depression (≥2 mm, fracturoscopy group) with the need for intraoperative correction. Patients in the fracturoscopy group demonstrated significantly greater preoperative fragment depression (12.55 ± 6.56 mm) and a larger preoperative fracture gap (7.83 ± 5.49 mm) compared with patients with a satisfactory reduction under fluoroscopy (depression 4.97 ± 4.02 mm, P = 0.016; gap 2.47 ± 1.07 mm, P = 0.023). Fluoroscopy was not successful in achieving satisfactory reduction in cases in which the postero-latero-central region was affected (P = 0.004, &khgr;2 test). Postoperative computed tomography demonstrated satisfactory articular reconstruction in all cases. Conclusions: Intraoperative fracturoscopy permitted a significantly improved visualization of fracture fragment displacement, specifically in the postero-latero-central region of the tibial plateau, as compared with fluoroscopy. Fracturoscopy is recommended for fractures involving the postero-latero-central region of the tibial plateau. Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Anterior Femoral Epiphysiodesis for the Treatment of Fixed Knee Flexion Deformity in Spina Bifida Patients

Background Fixed knee flexion deformity is a common problem in spina bifida patients. Owing to interference with ambulation, this deformity may lead to anterior knee pain and progressive crouch gait. If conservative treatment fails, surgical procedures including supracondylar femoral extension osteotomy, joint distraction, and posterior capsulotomy have to be considered. Potential complications of these procedures are fractures, neurovascular lesions, knee instability, and recurrent deformity with continued growth. As fixed knee flexion deformity in spina bifida patients frequently occurs bilaterally, this results in higher perioperative and postoperative risks and prolonged recovery, making these relatively invasive methods less appealing. In the skeletal immature patient, anterior femoral stapling is a feasible method to treat fixed knee flexion deformity as could be shown in an earlier study. In this study, anterior femoral stapling was performed in a series of patients with diverse etiologies, and the overall success rate was then calculated. The aim of this study was to determine whether anterior femoral epiphysiodesis may improve fixed knee flexion deformity in a group of spina bifida patients. Methods Ten spina bifida patients with bilateral fixed knee flexion deformity (20 knees) were treated by anterior femoral epiphysiodesis through stapling. None of the patients received further knee procedures. The mean preoperative fixed knee flexion deformity was 20.3±9.9 degrees (range: 10 to 40 degrees). Clinical and radiographic follow-up examinations were performed every 3 to 6 months after surgery. Results All patients except 1 experienced significant improvement with a mean correction rate of 0.9±0.5 degrees per month (range: 0.2 to 1.9 degrees). The residual flexion deformity averaged 5.3±5.3 degrees (range: 0 to 15 degrees; P<0.001). Conclusions Anterior femoral epiphysiodesis through stapling is an effective and safe method for the treatment of fixed knee flexion deformity in growing children and adolescents with spina bifida. Level of Evidence Therapeutic Study, Level IV.

Spine Injuries due to Horse Riding Accidents - an Analysis of 30 Cases

INTRODUCTION Horseback riding entails several risk factors that predispose the participant to injury. Especially craniocerebral as well as spinal trauma were common reasons for severe injuries. Hence, it is important to use effective protective gear during riding activities. However, the protective effect of actual safety vests and helmets in case of accident is still unknown. In the present study reasons, mechanisms and patterns of equine-related spine injuries were analyzed. Based on these data the effectiveness of used protective gear during accident was assessed. MATERIAL AND METHODS 30 equestrians took part in a questionnaire survey. Based on these answered questionnaires reasons, mechanisms and patterns of equine-related injuries as well as used protective gear during accident were evaluated and analyzed. RESULTS 24 patients (80 %) were female and 6 (20 %) were male. The median age at the time of injury was 36 years (range 14 - 72 years). The causalities suffered from 18 fractures (60 %) and 11 discoligamentous injuries (37 %), in one case a bone-bruise-injury (3 %) was found. 7 equestrians (23 %) wore a safety vest at time of injury. DISCUSSION Despite wearing a safety vest, the spine can get damaged when accident occurred. It is not possible to create vests for equestrians capable of protecting against all spine injuries in all accidents. If the energy impact is too high, serious injuries can result, even though protective body gear is worn. But the development of improved safety vests is necessary to reduce the number of severe spine injury in the future.

[Reaction of the epiphyseal groove to groove-crossing bore-wire osteosynthesis. Results of a histomorphologic small animal study].

ZusammenfassungBei 40 fünf bis sechs Wochen alten Kaninchen beiderlei Geschlechts wurden die Veränderungen einer 2 mm messenden Läsion in der distalen Femurepiphysenfuge histologisch untersucht. Nach Bohrungen zeigte sich als konstante Reaktion der Epiphysenfuge auf das Trauma die Entwicklung einer knöchernen Brückenbildung zwischen Epi-und Metaphyse. In dieser Studie wurde ein 2mm starker Kirschner-Bohrdraht transepiphysär in proximodistaler Richtung in das distale Femur eingebracht und dort über einen Zeitraum von 16 Wochen belassen. Die Epiphyse wuchs im Rahmen des Längenwachstums der Extremität von dem Kirschner- Draht hinweg, so daß dieser schließlich im metaphysären Bereich des Femurs zu liegen kam. Nach Tötung der Tiere wurden die entnommenen distalen Femora zunächst geröntgt, dann in der aufsteigenden Alkoholreihe entbettet und dehydriert. Anschließend erfolgte die Einbettung in Methacrylat und Aufarbeitung von 5μm dicken Serienschnitten mit dem Jung-Mikrotom und Färbung der Präparate mit Azur-Eosin bzw. Toluidin, Kossa und Trichrom nach Goldner. War die Epiphysenfuge dem Bohrdraht davongewachsen, bildeten sich im Fugendefekt zunächst schmale Ossifikationsbrücken die eine Kontinuitätsunterbrechung in Querrichtung aufwiesen. Es fand eine Kallusdistraktion statt, die eine knöcherne Brückenbildung verhinderte. Es konnte der experimentelle Erweis erbracht werden, daß transepiphysär eingebrachte Kirschner-Drähte das geeignete Osteosynthesematerial zur Behandlung kindlicher Gelenkverletzungen sind, wie die klinische Erfahrung seit Jahren zeigt.AbstractIn young rabbits of five to six weeks of age we revealed bony bridging as constant reaction of the epiphyseal cartilage on drilling with a 2 mm diameter trephine into the distal femur growth plate. Gross growth disturbancies will be the consequence of such partial closures. For this present study we inserted one 2 mm Kirschnerwire across the epiphyseal plate of the distal femur. The drilling was directed distally. During longitudinal growth the epiphysis moves away from the wire, that remains 8 weeks after the operation completely within the metaphyseal cancellous bone. Four, 8, 12 and 16 weeks postoperatively one group of the rabbits were sacrified. After radiological examination of the explanted femurs fixation and embedding in methylmetacrylate for morphological examination was performed. Our histological results reveal, that the crossing Kirschner-wire does not irritate the growth plate, even the physiological structure of the epiphyseal cartilage in the direct contact to the metal implant is not altered. The defect within the epiphyseal plate left after the relative retraction of the wire caused by growth activity fills with cancellous bone. Its trabecular structure is markedly thinner than the spongy bone within the metaphysis and shows longitudinal orientation. These trabeculae undergo segmental disruption by the growth pressure of the surrounding epiphyseal plate. In consequence there is no bone bridging and growth alterations by the Kirschner-wire crossing of the epiphyseal plate. This proves experimentally the clinical experienced therapeutic value of Kirschner-wires for internal fixation of dislocated joint injuries.In young rabbits of five to six weeks of age we revealed bony bridging as constant reaction of the epiphyseal cartilage on drilling with a 2 mm diameter trephine into the distal femur growth plate. Gross growth disturbances will be the consequence of such partial closures. For this present study we inserted one 2 mm Kirschner-wire across the epiphyseal plate of the distal femur. The drilling was directed distally. During longitudinal growth the epiphysis moves away from the wire, that remains 8 weeks after the operation completely within the metaphyseal cancellous bone. Four, 8, 12 and 16 weeks postoperatively one group of the rabbits were sacrificed. After radiological examination of the explanted femurs fixation and embedding in methylmetacrylate for morphological examination was performed. Our histological results reveal, that the crossing Kirschner-wire does not irritate the growth plate, even the physiological structure of the epiphyseal cartilage in the direct contact to the metal implant is not altered. The defect within the epiphyseal plate left after the relative retraction of the wire caused by growth activity fills with cancellous bone. Its trabecular structure is markedly thinner than the spongy bone within the metaphysis and shows longitudinal orientation. These trabeculae undergo segmental disruption by the growth pressure of the surrounding epiphyseal plate. In consequence there is no bone bridging and growth alterations by the Kirschner-wire crossing of the epiphyseal plate. This proves experimentally the clinical experienced therapeutic value of Kirschner-wires for internal fixation of dislocated joint injuries.

Interne Kallusdistraktion im Epiphysenfugendefektein physiologischer Weg der Spontankorrektur

For this experimental study we removed with a trephine in small (rabbit) and larger (pigs) animals cylinders of 2 mm respectively 8 mm diameter from the central growth plate area of proximal tibia. The direction of burring is in the axial line of the femur proximo-distally; the insertion point of the trephine is chosen on the cheek of the medial femoral condyle. As common reaction to that kind of trauma the defects in growth plates of rabbits become filled with a bone bridge that joins the epiphyseal core to the metaphyseal trabeculae, leading to gross growth disturbances. In pigs a similar solid bridging as first reaction develops, interrupted later by a zone of longitudinal collagen fibre bundles within a non-mineralized matrix. The distending pressure of surrounding intact growth cartilage continuously brakes fracture callus formation and its calcification. Such so-called internal callus distraction leads to unaltered longitudinal bone growth.ZusammenfassungIn einer vergleichenden tierexperimentellen Studie am Klein- und Großtier werden aus der Femurepiphyse in proximodistaler Richtung an der medialen Wange des distalen Femurs 2 mm bzw. 8 mm messende knöcherne Zylinder entnommen, die einen entsprechenden Substanzdefekt in der Epiphysenfuge verursachen. Beim Kleintier bildet sich in dem Defekt eine knöcherne Ausheilungsbrücke, die Epiphysenkern und Metaphyse fest miteinander verbindet. Im Großtierversuch kommt es ebenfalls zur Ausbildung einer knöchernen Ausheilungsbrücke. Es findet sich jedoch regelhaft eine Unterbrechungszone der ossären Brücke. In dieser Zone liegen parallel zu den Spongiosabälkchen in Wachstumsrichtung der Extremität angeordnet Kollagenfaserverbände in einer nichtmineralisierten Matrix. Der Frakturkallus wird durch den Wachstumsdruck des intakten Epiphysenfugenknorpels immer wieder auseinandergerissen; die hier stattfindende interne Kallusdistraktion verhindert ein Fehlwachstum.AbstractFor this experimental study we removed with a trephine in small (rabbit) and larger (pigs) animals cylinders of 2 mm respectively 8 mm diameter from the central growth plate area of proximal tibia. The direction of burring is in the axial line of the femur proximo-distally; the insertion point of the trephine is chosen on the cheek of the medial femoral condyle. As common reaction to that kind of trauma the defects in growth plates of rabbits become filled with a bone bridge that joins the epiphyseal core to the metaphyseal trabeculae, leading to gross growth disturbances. In pigs a similar solid bridging as first reaction develops, interrupted later by a zone of longitudinal collagen fibre bundles within a non-mineralized matrix. The distending pressure of sorrounding intact growth cartilage continuously brakes fracture callus formation and its calcification. Such so-called internal callus distraction leads to unaltered longitudinal bone growth.