Quantitative Analysis of Surface Contouring with Pulsed Bipolar Radiofrequency on Thin Chondromalacic Cartilage

The purpose of this study was to evaluate the quality of surface contouring of chondromalacic cartilage by bipolar radio frequency energy using different treatment patterns in an animal model, as well as examining the impact of the treatment onto chondrocyte viability by two different methods. Our experiments were conducted on 36 fresh osteochondral sections from the tibia plateau of slaughtered 6-month-old pigs, where the thickness of the cartilage is similar to that of human wrist cartilage. An area of 1 cm(2) was first treated with emery paper to simulate the chondromalacic cartilage. Then, the treatment with RFE followed in 6 different patterns. The osteochondral sections were assessed for cellular viability (live/dead assay, caspase (cell apoptosis marker) staining, and quantitative analysed images obtained by fluorescent microscopy). For a quantitative characterization of none or treated cartilage surfaces, various roughness parameters were measured using confocal laser scanning microscopy (Olympus LEXT OLS 4000 3D). To describe the roughness, the Root-Mean-Square parameter (Sq) was calculated. A smoothing effect of the cartilage surface was detectable upon each pattern of RFE treatment. The Sq for native cartilage was Sq=3.8 +/- 1.1 mu m. The best smoothing pattern was seen for two RFE passes and a 2-second pulsed mode (B2p2) with an Sq=27.3 +/- 4.9 mu m. However, with increased smoothing, an augmentation in chondrocyte death up to 95% was detected. Using bipolar RFE treatment in arthroscopy for small joints like the wrist or MCP joints should be used with caution. In the case of chondroplasty, there is a high chance to destroy the joint cartilage

Role of mesenchymal stem cells in meniscal repair

Meniscus integrity is the key for joint health of the knee. Therefore, the main goal of every meniscus treatment should be the maintenance of as much meniscus tissue as possible. Repair of meniscus tears can be achieved by meniscus suture. However, in a recently published meta-analysis, the long-term outcome of meniscus repair showed a mean failure rate of 24%. In a preclinical trial, locally applied mesenchymal stem cells produced differentiated meniscus-like tissue in meniscus tears indicating that mesenchymal-based cells, harvested from the bone marrow, enhance meniscus healing in critical-size meniscus tears. Symptomatic meniscus defects offer the option for meniscus transplantation with porous cell free biomaterials, when a complete meniscus rim is available. Cell-free biomaterials, which are actually in clinical application, reveal variable outcome in mid-term results from complete failure to regeneration with meniscus-like tissue. In several preclinical studies with different critical-size defects in the meniscus, the application of mesenchymal stem cells could significantly enhance meniscus regeneration compared to empty defects or to cell-free biomaterials. Regenerative treatment of meniscus with mesenchymal stem cells seems to be a promising approach to treat meniscal tears and defects. However it is still not clear, whether the stem cell effect is a direct action of the mesenchymal-based cells or is rather mediated by secretion of certain stimulating factors. The missing knowledge of the underlying mechanism is one of the reasons for regulatory burdens to permit these stem cell-based strategies in clinical practice. Other limitations are the necessity to expand cells prior to transplantation resulting in high treatment costs. Alternative treatment modalities, which use growth factors concentrated from peripheral blood aspirates or mononucleated cells concentrated from bone marrow aspirates, are currently in development in order to allow an attractive one-step procedure without the need for cell expansion in cultures and thus lower efforts and costs. In summary, Tissue Engineering of meniscus with mesenchymal based cells seems to be a promising approach to treat meniscal tears and defects in order to restore native meniscus tissue. However, advances of the technology are necessary to allow clinical application of this modern regenerative therapy

Hypoxia-Inducible Factor 1 Is an Inductor of Transcription Factor Activating Protein 2 Epsilon Expression during Chondrogenic Differentiation

The transcription factor AP-2ε (activating enhancer-binding protein epsilon) is expressed in cartilage of humans and mice. However, knowledge about regulatory mechanisms influencing AP-2ε expression is limited. Using quantitative real time PCR, we detected a significant increase in AP-2ε mRNA expression comparing initial and late stages of chondrogenic differentiation processes in vitro and in vivo. Interestingly, in these samples the expression pattern of the prominent hypoxia marker gene angiopoietin-like 4 (Angptl4) strongly correlated with that of AP-2ε suggesting that hypoxia might represent an external regulator of AP-2ε expression in mammals. In order to show this, experiments directly targeting the activity of hypoxia-inducible factor-1 (HIF1), the complex mediating responses to oxygen deprivation, were performed. While the HIF1-activating compounds 2,2′-dipyridyl and desferrioxamine resulted in significantly enhanced mRNA concentration of AP-2ε, siRNA against HIF1α led to a significantly reduced expression rate of AP-2ε. Additionally, we detected a significant upregulation of the AP-2ε mRNA level after oxygen deprivation. In sum, these different experimental approaches revealed a novel role for the HIF1 complex in the regulation of the AP-2ε gene in cartilaginous cells and underlined the important role of hypoxia as an important external regulatory stimulus during chondrogenic differentiation modulating the expression of downstream transcription factors

Sensor system for use with low intensity pulsed ultrasound

Purpose Ultrasound is a well-established technology in medical science, though many of the conventional measurement systems (hydrophones and radiation force balances [RFBs]) often lack accuracy and tend to be expensive. This is a significant problem where sensors must be considered to be "disposable" because they inevitably come into contact with biological fluids and expense increases dramatically in cases where a large number of sensors in array form are required. This is inevitably the case where ultrasound is to be used for the in vitro growth stimulation of a large plurality of biological samples in tissue engineering. Traditionally only a single excitation frequency is used (typically 1.5 MHz), but future research demands a larger choice of wavelengths for which a single broadband measurement transducer is desirable. Furthermore, because of implementation conditions there can also be large discrepancies between measurements. The purpose of this paper deals with a very cost-effective alternative to expensive RFBs and hydrophones. Design/methodology/approach Utilization of cost-effective piezoelectric elements as broadband sensors. Findings Very effective results with equivalent (if not better) accuracy than expensive alternatives. Originality/value This paper concentrates on how very cost-effective piezoelectric ultrasound transducers can be implemented as sensors for ultrasound power measurements with accuracy as good, if not better than those achievable using radiation force balances or hydrophones

Effects on the Distal Radioulnar Joint of Ablation of Triangular Fibrocartilage Complex Tears With Radiofrequency Energy

Purpose This cadaver study investigated the temperature profile in the wrist joint and distal radioulnar joint (DRUJ) during radiofrequency energy (RFE) application for triangular fibrocartilage complex resection. Methods An arthroscopic partial resection of the triangular fibrocartilage complex using monopolar and bipolar RFE was simulated in 14 cadaver limbs. The temperature was recorded simultaneously in the DRUJ and at 6 other anatomic locations of the wrist during RFE application. Results The mean temperature in the DRUJ was 43.3 +/- 8.2 degrees C for the bipolar system in the ablation mode (60 W) and 30.4 +/- 3.4 degrees C for the monopolar system in the cut mode (20 W) after 30 seconds. The highest measured temperature in the DRUJ was 54.3 degrees C for the bipolar system and 68.1 degrees C for the monopolar system. Conclusions The application of RFE for debridement or resection of the triangular fibrocartilage complex in a clinical setting can induce peak temperatures that might cause damage to the cartilage of the DRUJ. Bipolar systems produce higher mean temperatures than monopolar devices. Clinical relevance RFE application increases the mean temperature in the DRUJ after 30 seconds to a level that may jeopardize cartilage tissue. Copyright (C) 2016 by the American Society for Surgery of the Hand. All rights reserved.

In Vitro Testing of Scaffolds for Mesenchymal Stem Cell-Based Meniscus Tissue Engineering—Introducing a New Biocompatibility Scoring System

A combination of mesenchymal stem cells (MSCs) and scaffolds seems to be a promising approach for meniscus repair. To facilitate the search for an appropriate scaffold material a reliable and objective in vitro testing system is essential. This paper introduces a new scoring for this purpose and analyzes a hyaluronic acid (HA) gelatin composite scaffold and a polyurethane scaffold in combination with MSCs for tissue engineering of meniscus. The pore quality and interconnectivity of pores of a HA gelatin composite scaffold and a polyurethane scaffold were analyzed by surface photography and Berliner-Blau-BSA-solution vacuum filling. Further the two scaffold materials were vacuum-filled with human MSCs and analyzed by histology and immunohistochemistry after 21 days in chondrogenic media to determine cell distribution and cell survival as well as proteoglycan production, collagen type I and II content. The polyurethane scaffold showed better results than the hyaluronic acid gelatin composite scaffold, with signs of central necrosis in the HA gelatin composite scaffolds. The polyurethane scaffold showed good porosity, excellent pore interconnectivity, good cell distribution and cell survival, as well as an extensive content of proteoglycans and collagen type II. The polyurethane scaffold seems to be a promising biomaterial for a mesenchymal stem cell-based tissue engineering approach for meniscal repair. The new score could be applied as a new standard for in vitro scaffold testing

RFE based chondroplasty in wrist arthroscopy indicates high risk for chrondocytes especially for the bipolar application

Background The application of radiofrequency energy (RFE) has become widespread for surgical performed chondroplasty especially due to the anticipated sealing effect, however the safety of this procedure in the wrist remains unclear. The purpose of this study was to investigate the subchondral temperature during radiofrequency energy (RFE) application simulating chondroplasty in an arthroscopic setting of the wrist. Methods A chondroplasty of the lunate fossa was performed during an arthroscopy setting on 14 cadaver arms using monopolar or biopolar RFE. The temperature was recorded simultaneously from 7 predefined anatomical landmarks. Results The mean temperature for both application modes did not exceed more than 30°C at all measured points, except for the lunate fossa. The highest subchondral measured peak temperature was 49.35°C (monopolar) and 69.21°C (bipolar) in the lunate fossa. In addition, the temperature decreased for both radiofrequency (RF) devices depending on the distance of the sensors to the RF-probe. Conclusion It remains to be questionable how safe RFE can be used for chondroplasty in wrist arthroscopy under continuous irrigation and constant movement to obtain the desired sealing effect. However, the bipolar device should be applied with more caution since peak temperature in the lunate fossa almost reached 70°C even under continuous irrigation

Higher Ratios of Hyaluronic Acid Enhance Chondrogenic Differentiation of Human MSCs in a Hyaluronic Acid–Gelatin Composite Scaffold

Mesenchymal stem cells (MSCs) seeded on specific carrier materials are a promising source for the repair of traumatic cartilage injuries. The best supportive carrier material has not yet been determined. As natural components of cartilage’s extracellular matrix, hyaluronic acid and collagen are the focus of biomaterial research. In order to optimize chondrogenic support, we investigated three different scaffold compositions of a hyaluronic acid (HA)-gelatin based biomaterial. Methods: Human MSCs (hMSCs) were seeded under vacuum on composite scaffolds of three different HA-gelatin ratios and cultured in chondrogenic medium for 21 days. Cell-scaffold constructs were assessed at different time points for cell viability, gene expression patterns, production of cartilage-specific extracellular matrix (ECM) and for (immuno-)histological appearance. The intrinsic transforming growth factor beta (TGF-beta) uptake of empty scaffolds was evaluated by determination of the TGF-beta concentrations in the medium over time. Results: No significant differences were found for cell seeding densities and cell viability. hMSCs seeded on scaffolds with higher ratios of HA showed better cartilage-like differentiation in all evaluated parameters. TGF-beta uptake did not differ between empty scaffolds. Conclusion: Higher ratios of HA support the chondrogenic differentiation of hMSCs seeded on a HA-gelatin composite scaffold

Temperature Profile of Radiofrequency Probe Application in Wrist Arthroscopy: Monopolar Versus Bipolar

Purpose: The purpose of this study was to investigate the changes in temperature during wrist arthroscopy comparing monopolar and bipolar radiofrequency energy (RFE). Methods: A standard wrist arthroscopy was performed on 14 arms of 7 cadavers without irrigation or with continuous irrigation with 0.9% saline solution and gravity-assisted outflow through an 18-gauge needle. We treated 7 wrists with a bipolar device (VAPR II with 2.3-mm side effect electrodes; DePuy Mitek, Westwood, MA) and 7 wrists with a monopolar device (OPES Ablator for small joints, 45 degrees; Arthrex, Naples, FL). The temperature was recorded simultaneously from 7 predefined anatomic landmarks. Results: We observed an increase in the temperature corresponding to the time of energy application. The highest measured peak temperatures were 52 degrees C (monopolar) and 49.5 degrees C (bipolar) without irrigation. Continuous irrigation led to a significant reduction in the temperature at the site of the energy application. The mean temperature decreased by 7 degrees C for the monopolar system and 5 degrees C for the bipolar system when irrigation was used. For both radiofrequency devices, we found a decrease in the temperature proportional to the distance of the sensors to the radiofrequency probe. Conclusions: Monopolar and bipolar RFE can be safely used in wrist arthroscopy if a continuous irrigation system is applied and the energy impulse does not exceed 5 to 10 seconds. However, it should be used with great care to avoid local heat damage especially at the cartilage. Clinical Relevance: This basic science study was performed to gain data concerning the temperature in wrist arthroscopy and to broaden the knowledge about the risks when using RFE. Furthermore, we sought to control side effects of RFE by finding the best applied form of RFE regarding duration and pulsation (monopolar/bipolar)