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Purpose The German Arthroscopy Registry (DART) has been initiated in 2017 with the aim to collect real-life data of patients undergoing knee, shoulder, hip or ankle surgery. The purpose of this study was to present an overview of the current status and the collected data thus far. Methods Data entered between 11/2017 and 01/2022 were analyzed. The number of cases (each case is defined as a single operation with or without concomitant procedures) entered for each joint, follow-up rates and trends between different age groups (18–29 years, 30–44 years, 45–64 years, ≥ 65 years) and across genders, and quality of life improvement (pre- vs. 1 year postoperative EQ visual analogue scale [EQ-VAS]) for frequently performed procedures (medial meniscus repair [MMR] vs. rotator cuff repair [RCR] vs. microfracturing of the talus [MFX-T]) were investigated. Results Overall, 6651 cases were entered into DART, forming three distinct modules classified by joint (5370 knee, 1053 shoulder and 228 ankle cases). The most commonly entered procedures were: knee: partial medial meniscectomy (n = 2089), chondroplasty (n = 1389), anterior cruicate ligament reconstruction with hamstring autograft (n = 880); shoulder: sub acromial decompression (n = 631), bursectomy (n = 385), RCR (n = 359); ankle: partial synovectomy (n = 117), tibial osteophyte resection (n = 72), loose body removal (n = 48). In the knee and shoulder modules, middle-aged patients were the predominant age group, whereas in the ankle module, the youngest age group was the most frequent one. The two oldest age groups had the highest 1-year follow-up rates across all modules. In the knee and shoulder module, 1-year follow-up rates were higher in female patients, whereas follow-up rates were higher in male patients in the ankle module. From pre- to 1-year postoperative, MFX-T (EQ-VAS: 50.0 [25–75% interquartile range: 31.8–71.5] to 75.0 [54.3–84.3]; ∆ + 25.0) led to a comparably larger improvement in quality of life than did MMR (EQ-VAS: 70.0 [50.0–80.0] to 85.0 [70.0–94.0]; ∆ + 15.0) or RCR (EQ-VAS: 67.0 [50.0–80.0] to 85.0 [70.0–95.0]; ∆ + 18.0). Conclusion DART has been sufficiently established and collects high-quality patient-related data with satisfactory follow-up allowing for a comprehensive analysis of the collected data. The current focus lies on improving patient enrolment and follow-up rates as well as initiating the hip module.

Cartilage regeneration with cell-free matrices has developed from matrix-associated autologous cartilage cell transplantation (MACT) over ten years ago. Adjustments to the legal framework and higher hurdles for cell therapy have led to the procedures being established as an independent alternative to MACT. These procedures, which can be classified as matrix-induced autologous cartilage regeneration (MACR), all rely on the chemotactic stimulus of a cross-linked matrix, which mostly consists of collagens. Given the example of a commercially available type I collagen hydrogel, the physicochemical properties of such a matrix are explained and the available experimental data highlighted in more detail. The interaction between different cell types and the chemotactic properties of the collagen has been investigated extensively and, from a clinical point of view, today offers various reference points for a smart modification of the described method to further improve clinical outcomes. Since the origin of the cells in the ultimately formed repair tissue is still unrevealed, further investigations to clarify the exact mechanism are crucially needed.Die Knorpelregeneration mit zellfreien Matrices hat sich vor mittlerweile über 10 Jahren aus der matrixassoziierten autologen Knorpelzelltransplantation (MACT) entwickelt. Anpassungen der rechtlichen Rahmenbedingungen und höhere Hürden für die Zelltherapie haben dazu geführt, dass sich die Verfahren als eigenständige Alternative zur MACT etabliert haben. Die als matrixinduzierte autologe Knorpelregeneration (MACR) einzuordnenden Verfahren setzen sämtlich auf den chemotaktischen Reiz einer vernetzten Matrix, die zumeist aus Kollagenen besteht. Am Beispiel eines marktüblichen Kollagen-Typ-I-Hydrogels werden die physikochemischen Eigenschaften einer solchen Matrix erläutert und die hierzu vorliegenden experimentellen Daten näher beleuchtet. Das Zusammenspiel zwischen verschiedenen Zelltypen und den chemotaktischen Eigenschaften des Kollagens wurde umfangreich untersucht und bietet aus klinischer Sicht heute unterschiedliche Anknüpfungspunkte zur sinnvollen Modifikation des Verfahrens zur Verbesserung des klinischen Outcomes. Da der Ursprung der Zellen im letztlich gebildeten Regeneratgewebe nach wie vor ungeklärt ist, sind weitere Untersuchungen zur Aufklärung des genauen Wirkmechanismus jedoch zwingend erforderlich.

Introduction While BMP-7 has proven to be one of the most potent growth factors in cartilage tissue engineering, protein concentration and route of administration remain a matter of debate. Here we investigated the effects of a low concentration of BMP-7 on human osteoarthritic chondrocytes administered by protein co-cultivation and plasmid transfection. Methods Freshly released (P0) or in vitro propagated chondrocytes (P2) were cultivated in a collagen type-I gel for 3 weeks in vitro or in nude mice. Seeded chondrocytes were treated with 50 ng/mL BMP-7 directly added to the medium or were subject to transient BMP-7 plasmid transfection prior to gel cultivation. Untreated specimens served as a control. After recovery, samples were investigated by histological and immunohistochemical staining and real-time PCR. Results In vitro, collagen type-II protein production was enhanced, and it was stored mainly pericellularly. Collagen type-II and aggrecan gene expression were enhanced in both treatment groups. After nude mouse cultivation, col-II protein production was further enhanced, but specimens of the BMP-7 transfection group revealed a clustering of col-II positive cells. Gene expression was strongly up-regulated, chondrocyte number was increased and the differentiated phenotype prevailed. In general, freshly released chondrocytes (P0) proved to be superior to chondrocytes pre-amplified in vitro (P2). Conclusions Both BMP-7 co-cultivation and plasmid transfection of human osteoarthritic chondrocytes led to improved cartilage repair tissue. Nevertheless, the col-II distribution following BMP-7 co-cultivation was homogeneous, while samples produced by transient transfection revealed a col-II clustering.

The purpose of this study was to evaluate the potential value of a cell-free collagen type I gel plug for the treatment of focal cartilage defects. Cellular migration and proliferation was addressed in vitro, and the formation of repair tissue in a nude mouse-based defect model. A cell-free plug made of collagen type I was placed in the center of an incubation plate. Surrounding space was filled with a collagen type I gel (Arthro Kinetics, Esslingen, Germany) seeded with 2 x 10(5) human articular chondrocytes/mL gel. After cultivation for up to 6 weeks in vitro, samples were subject to histological and immunohistochemical staining and gene expression analysis. Subsequently, chondral defects of human osteochondral blocks were treated with the plug, and specimens were cultivated subcutaneously in nude mice for 6 weeks. The repair tissue was evaluated macroscopically, and collagen type II production was investigated immunohistochemically. In vitro, morphology of immigrated cells did not show any differences, as did collagen type II gene expression. After 4 weeks, the plug was homogeneously inhabited. After 6 weeks of cultivation in nude mice, collagen gel plug treatment led to a macroscopically excellent repair tissue. Histological staining revealed a tight bonding, and the collagen gel plug started to be remodeled. We conclude that the novel collagen gel plug device offers an environment favorable for the migration of articular chondrocytes and leads to a good-quality repair tissue in the nude mouse model. The arthroscopic transplantation of a collagen gel plug may be one option in the treatment of focal cartilage defects.

The aim of this study is to define stem design related factors causing both gaps in the metal–bone cement interface and cracks within the cement mantle. Six different stem designs (Exeter; Lubinus SP II; Ceraver Osteal; Mueller-straight stem; Centega; Spectron EF) ( n =15 of each design) were cemented into artificial femur bones. Ten stems of each design were loaded, while five stems served as an unloaded control. Physiologically adapted cyclical loading (DIN ISO 7206-4) was performed with a hip simulator. After loading both interfaces and the bone cement itself were analysed regarding gaps and cracks in the cement mantle. Significant differences between the stem designs concerning gaps in the metal–bone cement interface and cracks in the cement mantle became apparent. Additionally, a high correlation between gaps in the metal–bone cement interface and cracks within the cement mantle could be proven. Gaps in the metal–bone cement interface but no cracks within the cement mantle were seen in the unloaded specimens. Differences between the unloaded control groups and the cyclical loaded stems regarding the longitudinal extension and width of gaps in the metal–bone cement interface were obvious. The designs of cemented femoral stems have an influence on both the quality of the metal–bone cement contact and the failure rate of the cement mantle. Less interface gaps and less cement defects were found with anatomically formed, collared, well-rounded stem designs without undercuttings.

Wear of ultra-high-molecular-weight polyethylene (UHM-WPE) inlays is associated with aseptic loosening in total knee replacement (TKR). The aim of this study was to investigate the in vitro performance of a TKR system that combines several measures to decrease UHMWPE wear. Tests were carried out on a BPK-S Integration system (RD mobile, 0.32 microm). In conclusion, the combination of design features and surface modifications of the BPK-S integration TKR system leads to low gravimetric UHMWPE wear.

Purpose This study investigated the potential of cyclic compressive loading in the generation of in vitro engineered cartilaginous tissue with the aim of contributing to a better understanding of mechanical preconditioning and its possible role in further optimizing existing matrix-associated cartilage replacement procedures. Methods Human chondrocytes were harvested from 12 osteoarthritic knee joints and seeded into a type I collagen (col-I) hydrogel at low density (2 × 10(5) cells/ml gel). The cell-seeded hydrogel was condensed and cultivated under continuous cyclic compressive loading (frequency: 0.3 Hz; strain: 10%) for 14 days under standardized conditions. After retrieval, specimens were subject to staining, histomorphometric evaluation, gene expression analysis and biomechanical testing. Results Cellular morphology was altered by both stimulation and control conditions as was staining for collagen II (col-II). Gene expression measurements revealed a significant increase for col-II under either cultivation condition. No significant differences in col-I, aggrecan and MMP-13 gene expression profiles were found. The col-II/col-I mRNA ratio significantly increased under stimulation, whereas the biomechanical properties deteriorated under either cultivation method. Conclusions Although the effects observed are small, mechanical preconditioning has demonstrated its potential to modulate biological properties of collagen hydrogels seeded with human chondrocytes.

Cartilage repair strategies increasingly focus on the in vitro development of cartilaginous tissues that mimic the biological and mechanical properties of native articular cartilage. However, current approaches still face problems in the reproducible and standardized generation of cartilaginous tissues that are both biomechanically adequate for joint integration and biochemically rich in extracellular matrix constituents. In this regard, the present study investigated whether long-term continuous compressive loading would enhance the mechanical and biological properties of such tissues. Human chondrocytes were harvested from 8 knee joints (n=8) of patients having undergone total knee replacement and seeded into a collagen type I hydrogel at low density of 2×10(5)cells/ml gel. Cell-seeded hydrogels were cut to disks and subjected to mechanical stimulation for 28 days with 10% continuous cyclic compressive loading at a frequency of 0.3 Hz. Histological and histomorphometric evaluation revealed long-term mechanical stimulation to significantly increase collagen type II and proteoglycan staining homogenously throughout the samples as compared to unstimulated controls. Gene expression analyses revealed a significant increase in collagen type II, collagen type I and MMP-13 gene expression under stimulation conditions, while aggrecan gene expression was decreased and no significant changes were observed in the collagen type II/collagen type I mRNA ratio. Mechanical propertywise, the average value of elastic stiffness increased in the stimulated samples. In conclusion, long-term mechanical preconditioning of human chondrocytes seeded in collagen type I hydrogels considerably improves biological and biomechanical properties of the constructs, corroborating the clinical potential of mechanical stimulation in matrix-associated autologous chondrocyte transplantation (MACT) procedures.

Three-dimensional autologous chondrocyte implantation based on collagen gel as matrix scaffold has become a clinically applied treatment for focal defects of articular cartilage. However, the low biomechanical properties of collagen gel makes intraoperative handling difficult and creates the risk of early damages to the vulnerable implant. The aim of the study was to create a stabilized form of collagen gel and to evaluate its biomechanical and biochemical properties.Collagen type-I gel was seeded with human articular chondrocytes. 20 samples were subject to condensation which was achieved mechanically by compression and filtration. Control samples were left uncondensed. From both types of gels 10 samples were used for initial biomechanical evaluation by means of unconfined compression and 10 samples were cultivated under standard conditions in vitro. Following cultivation the samples were evaluated by conventional histology and immunohistochemistry. The proliferation rate was calculated and matrix gene expression was quantified by real-time PCR.The biomechanical tests revealed a higher force carrying capacity of the condensed specimens. Strain rate dependency and relaxation was seen in both types of collagen gel representing viscoelastic material properties. Cells embedded within the condensed collagen gel were able to produce extracellular matrix proteins and showed proliferation.Condensed collagen gel represents a mechanically improved type of biomaterial which is suitable for three-dimensional autologous chondrocyte implantation.

BMC complementary and alternative medicine 10, 43-43 (2010). doi:10.1186/1472-6882-10-43, Published by BioMed Central, London

Wear of ultra-high-molecular-weight polyethylene (UHM-WPE) inlays is associated with aseptic loosening in total knee replacement (TKR). The aim of this study was to investigate the in vitro performance of a TKR system that combines several measures to decrease UHMWPE wear. Tests were carried out on a BPK-S Integration system (RD, P. Brehm Chirurgie-Mechanik, Weisendorf, Germany) according to ISO 14,243-1 in a knee joint simulator. Calf serum with a high protein concentration of 30 g/l was chosen as the test lubricant. PE wear was measured gravimetrically. Particle analysis was performed by scanning electron microscopy, with measurement of particle size and shape. Low mean wear rates of 1.20 mg per million cycles were found for the fixed bearing type and 2.47 mg per million cycles for the rotating-platform bearing design. Anteroposterior deflection was low. The contact areas for both types of bearings were large and showed a constant pattern throughout the test. Backside wear was obvious on rotating platforms. Particle analysis revealed equally sized and round-shaped particles in both types of bearings (fixed, 0.35 microm; mobile, 0.32 microm). In conclusion, the combination of design features and surface modifications of the BPK-S integration TKR system leads to low gravimetric UHMWPE wear.

In recent years, a great variety of different matrix systems for the cultivation of chondrocytes have been developed. Although some of these scaffolds show promising experimental results in vitro, the potential clinical value remains unclear. In this comparative study, we propagated human articular chondrocytes precultivated in monolayer culture on six different scaffolds (collagen gels, membranes and sponges) under standardized in vitro conditions. Mechanical properties of the matrix systems were not improved significantly by cultivation of human chondrocytes under the given in vitro conditions. The gel systems (CaReS, Ars Artho, Germany and Atelocollagen, Koken, Japan) showed a homogeneous cell distribution; chondrocytes propagated on Chondro-Gide (Geistlich Biomaterials, Switzerland) and Integra membranes (Integra, USA) were building multilayers. Only few cells penetrated the two Atelocollagen honeycomb sponges (Koken, Japan). During cultivation, chondrocytes propagated on all systems showed a partial morphological redifferentiation, which was best with regard to the gel systems. In general, only small amounts of collagen type-II protein could be detected in the pericellular region and chondrocytes failed to build a territorial matrix. During the first two weeks of cultivation, the two gel systems showed a significantly higher collagen type-II gene expression and a lower collagen type-I gene expression than the other investigated matrix systems. Although collagen gels seem to be superior when dealing with deep cartilage defects, membrane systems might rather be useful in improving conventional autologous chondrocyte transplantation or in combination with gel systems.