Microfracture for the treatment of cartilage defects in the knee joint - A golden standard?

A hybrid repair strategy for full-thickness cartilage defects: Long-term experimental study in eight horses

The objective of this study was to evaluate a non-resorbable implant for the focal repair of chondral defects in eight adult horses with 12-month follow-up. The bi-layered construct composed of a polycarbonate-urethane-urea biomaterial which was printed in 3D fashion onto a bone anchor was implanted into surgically created osteochondral defects into the femoropatellar joints of eight horses. The analysis of post-mortem outcomes were compared to defects treated with microfracture in the same animal on the contralateral femoropatellar jointfemoropatellar joint. The overall macroscopic scoring after 12 months yielded higher scores in the OCI-treated stifles compared to MF treatment (p = 0.09) with better quality and filling of the defect. Histology revealed good anchorage of repair tissue growing into the 3D structure of the implant and histopathology scoring for adjacent native cartilage showed no difference between groups. MRI and micro-CT showed overall less sclerotic reactions in the surrounding bone in the implant group and no foreign body reaction was detected. Biomechanical analysis of the repair tissue revealed a significantly higher peak modulus (p < 0.05) in the implant group (0.74 ± 0.45) compared to the microfracture control group (0.15 ± 0.11). Dynamic loading yielded higher values for the repair tissue overgrowing the implant group (0.23 ± 0.17) compared to the microfracture control (0.06 ± 0.06) (p < 0.05). The bi-layered osteochondral implant provided a safe implant for focal repair of full-thickness osteochondral defects, as no adverse reaction was seen within the joints and the level of degeneration of adjacent cartilage to the repair site was not different compared to that seen in defects treated with microfracture after 12 months.

A novel mechanism behind irreversible development of cartilage degradation driven articular cartilage defects revealed by rat model: The chain reaction initiated by extracellular vesicles delivered LOC102546541

BACKGROUND

Articular cartilage defects (ACD) are injuries with a diameter greater than 3 mm, resulting from wear and tear on joints. When the diameter of the defect exceeds 6 mm, it can further damage the surrounding joint cartilage, causing osteoarthritis (OA). Try to explain why OA is an irreversible disease, we hypothesize that damaged articular chondrocytes (DAC) may have reduced capacities to repair cartilage because its extracellular vesicle (EVs) that might directly contribute to OA formation.

METHODS

In this study, DAC-EVs and AC-EVs were isolated using ultracentrifugation. Next-generation sequencing was employed to screen for a pathogenic long non-coding RNA (lncRNA). After verifying its function in vitro, the corresponding small interfering RNA (siRNA) was constructed and loaded into extracellular vesicles, which were then injected into the knee joint cavities of rats.

RESULTS

The results revealed that DAC-EVs packaged lncRNA LOC102546541 acts as a competitive endogenous RNA (ceRNA) of MMP13, down-regulating miR-632. Consequently, the function of MMP13 in degrading the extracellular matrix is enhanced, promoting the development of osteoarthritis.

CONCLUSIONS

This study uncovered a novel mode of OA pathogenesis using rat models, which DAC deliver pathogenic LOC102546541 packaged EVs to normal articular chondrocytes, amplifying the degradation of the extracellular matrix. Nonetheless, the functions of highly homologous human gene of LOC102546541 need to be verified in the future.

Evaluating Return to Sports After Surgical Treatment of Unstable Osteochondritis Dissecans of the Knee: A Systematic Review

Background

Although the incidence of osteochondritis dissecans (OCD) of the knee may be low, an overview and comparison of sports-related outcomes with current surgical management techniques are needed.

Purpose

To summarize the available evidence regarding outcomes for different surgical treatment options for unstable OCD of the knee in both skeletally mature and immature patients by calculating the return to sports (RTS) rate, the mean RTS time, and other sports-related postoperative outcome measures.

Study Design

Systematic review; Level of evidence, 4.

Methods

A systematic review of studies on RTS after surgical correction of unstable OCD within the knee was conducted utilizing PubMed, Embase, and the Cochrane databases. Included were studies discussing the treatment of unstable OCD with minimum 1-year follow-up outcomes. Multivariate analysis was used to compare studies grouped together based on RTS and skeletal maturity.

Results

Of 2229 articles, 6 studies (197 patients; 198 knees) met the inclusion criteria and were included in our analysis. The percentage of patients who returned to the previous level of sport ranged from 52% to 100%; those returning to any level of sport ranged from 87% to 100%. Clinical outcomes did not differ between patients with open versus closed physes. Osteochondral Autograft Transfer System (OATS) procedures had a 100% RTS rate across several studies with skeletally mature and mixed cohorts, and microfracture had the lowest overall RTS rate (52%). For skeletally immature patients, all examined studies that utilized either open or arthroscopic reduction and internal fixation, 77% and 78%, respectively, had acceptable RTS rates. Arthroscopic fixation had a higher rate of revision surgery in both skeletally mature and immature patients.

Conclusion

Our analysis indicated that the treatment of unstable OCD lesions using the OATS technique demonstrated high RTS rates across several studies, while microfracture alone exhibited the lowest RTS rate. Both arthroscopic and open internal fixation utilizing bioabsorbable screws yielded satisfactory RTS rates for juvenile patients with OCD.

Chitosan-PNIPAM Thermogel Associated with Hydrogel Microspheres as a Smart Formulation for MSC Injection

Regenerative medicine based on cell therapy has emerged as a promising approach for the treatment of various medical conditions. However, the success of cell therapy heavily relies on the development of suitable injectable hydrogels that can encapsulate cells and provide a conducive environment for their survival, proliferation, and tissue regeneration. Herein, we address the medical need for cyto- and biocompatible injectable hydrogels by reporting on the synthesis of a hydrogel-forming thermosensitive copolymer. The copolymer was synthesized by grafting poly(N-isopropylacrylamide-co-carboxymethyl acrylate) (PNIPAM-COOH) onto chitosan through amide coupling. This chemical modification resulted in the formation of hydrogels that exhibit a sol-gel transition with an onset at approximately 27 °C, making them ideal for use in injectable applications. The hydrogels supported the survival and proliferation of cells for several days, which is critical for cell encapsulation. Furthermore, the study evaluates the addition of collagen/chitosan hybrid microspheres to support the adhesion of mesenchymal stem cells within the hydrogels. Altogether, these results demonstrate the potential of the PNIPAM-chitosan thermogel for cell encapsulation and its possible applications in regenerative medicine.

Continuous Low-Intensity Ultrasound Improves Cartilage Repair in Rabbit Model of Subchondral Injury

Subchondral drilling (SD), a bone marrow stimulation technique, is used to repair cartilage lesions that lack regenerative potential. Cartilage repair outcomes upon SD are typically fibrocartilaginous in nature with inferior functionality. The lack of cues to foster the chondrogenic differentiation of egressed mesenchymal stromal cells upon SD can be attributed for the poor outcomes. Continuous low-intensity ultrasound (cLIUS) at 3.8 MHz is proposed as a treatment modality for improving cartilage repair outcomes upon marrow stimulation. Bilateral defects were created by SD on the femoral medial condyle of female New Zealand white rabbits (n = 12), and the left joint received cLIUS treatment (3.8 MHz, 3.5 Vpp, 8 min/application/day) and the contralateral right joint served as the control. On day 7 postsurgery, synovial fluid was aspirated, and the cytokine levels were assessed by Quantibody™ assay. Rabbits were euthanized at 8 weeks and outcomes were assessed macroscopically and histologically. Defect areas in the right joints exhibited boundaries, incomplete fill, irregular cartilage surfaces, loss of glycosaminoglycan (GAG), and absence of chondrocytes. In contrast, the repaired defect area in the joints that received cLIUS showed complete fill, positive staining for GAG with rounded chondrocyte morphology, COL2A1 staining, and columnar organization. Synovial fluid collected from cLIUS-treated left knee joints had lower levels of IL1, TNFα, and IFNγ when compared to untreated right knee joints, alluding to the potential of cLIUS to mitigate early inflammation. Further at 8 weeks, left knee joints (n = 12) consistently scored higher on the O'Driscoll scale, with a higher percent hyaline cartilage score. No adverse impact on bone or change in the joint space was noted. Upon a single exposure of cLIUS to TNFα-treated cells, nuclear localization of pNFκB and SOX9 was visualized by double immunofluorescence and the expression of markers associated with the NFκB pathway was assayed by quantitative real-time polymerase chain reaction. cLIUS extends its chondroprotective effects by titrating pNFκB levels, preventing its nuclear translocation, while maintaining the expression of SOX9, the collagen II transcription factor. Our combined results demonstrate that healing of chondral defects treated with marrow stimulation by SD can be accelerated by employing cLIUS regimen that possesses chondroinductive and chondroprotective properties. Impact statement Repair of cartilage represents an unsolved biomedical burden. In vitro, continuous low-intensity ultrasound (cLIUS) has been demonstrated to possess chondroinductive and chondroprotective potential. To our best knowledge, the use of cLIUS to improve cartilage repair outcomes upon marrow stimulation, in vivo, has not been reported and our work reported here fills that gap. Our results demonstrated enhanced cartilage repair outcomes under cLIUS (3.8 MHz) in a rabbit model of subchondral injury by subchondral drilling. Enhanced repair stemmed from mesenchymal stem cell differentiation in vivo and the subsequent synthesis of articular cartilage-specific matrix.

Immunomodulatory Strategies for Cartilage Regeneration in Osteoarthritis

Osteoarthritis (OA) is the most prevalent musculoskeletal disorder and a leading cause of disability globally. Although many efforts have been made to treat this condition, current tissue engineering (TE) and regenerative medicine strategies fail to address the inflammatory tissue environment that leads to the rapid progression of the disease and prevents cartilage tissue formation. First, this review addresses in detail the current anti-inflammatory therapies for OA with a special emphasis on pharmacological approaches, gene therapy, and mesenchymal stromal cell (MSC) intra-articular administration, and discusses the reasons behind the limited clinical success of these approaches at enabling cartilage regeneration. Then, we analyze the state-of-the-art TE strategies and how they can be improved by incorporating immunomodulatory capabilities such as the optimization of biomaterial composition, porosity and geometry, and the loading of anti-inflammatory molecules within an engineered structure. Finally, the review discusses the future directions for the new generation of TE strategies for OA treatment, specifically focusing on the spatiotemporal modulation of anti-inflammatory agent presentation to allow for tailored patient-specific therapies. Impact statement Osteoarthritis (OA) is a prevalent and debilitating musculoskeletal disorder affecting millions worldwide. Despite significant advancements in regenerative medicine and tissue engineering (TE), mitigating inflammation while simultaneously promoting cartilage tissue regeneration in OA remains elusive. In this review article, we discuss current anti-inflammatory therapies and explore their potential synergy with cutting-edge cartilage TE strategies, with a special focus on novel spatiotemporal and patient-specific anti-inflammatory strategies.

Surgical Treatment of Focal Chondral Lesions of the Knee in the Military Population: Current and Future Therapies

INTRODUCTION

Chondral and osteochondral defects of the knee are common injuries in the military population that have a significant impact on readiness. Definitive treatment of these injuries is challenging since cartilage has a limited capacity for self-repair and regeneration. Management is particularly challenging in military patients who maintain a higher level of activity similar to athletes. Existing surgical techniques have variable results and often long recovery times, sparking the development of several new innovative technologies to return service members back to duty more quickly and effectively after cartilage injury. The purpose of this article is to review the current and future surgical treatments for chondral and osteochondral knee lesions and their relevance in managing these injuries in the military.

METHODS

In this review article, we describe the current treatments for chondral and osteochondral defects of the knee, reporting on outcomes in military populations. We explore emerging treatment modalities for cartilage defects, reporting innovations, stage of research, and current data. Published results of each treatment option in military populations are reviewed throughout the article.

RESULTS

This review includes 12 treatments for chondral lesions. Of these therapies, four are considered synthetic and the remaining are considered regenerative solutions. Regenerative therapies tend to perform better in younger, healthier populations with robust healing capacity. Success of treatment depends on lesions and patient characteristics. Nearly all modalities currently available in the USA were successful in improving patients from presurgical function in the short (<6 months) term, but the long-term efficacy is still challenged. Upcoming technologies show promising results in clinical and animal studies that may provide alternative options desirable for the military population.

CONCLUSIONS

The current treatment options for cartilage lesions are not entirely satisfactory, usually with long recovery times and mixed results. An ideal therapy would be a single procedure that possesses the ability to enable a quick return to activity and duty, alleviate pain, provide long-term durability, and disrupt the progression of osteoarthritis. Evolving technologies for cartilage lesions are expanding beyond currently available techniques that may revolutionize the future of cartilage repair.

Particulated Juvenile Articular Cartilage Allograft Transplantation for Patellofemoral Defects Shows Favorable Return-to-Sport Rates and Patient-Reported Outcomes

PURPOSE

To report return-to-sport rates, postoperative patient-reported outcomes (PROs), complication rates, and reoperation rates of a cohort of patients undergoing particulated juvenile articular cartilage (PJAC) allograft transplantation for patellofemoral articular cartilage defects.

METHODS

We performed a single-institution retrospective review of all patients with patellofemoral articular cartilage defects who received PJAC allograft transplantation from 2014 to 2022. Baseline demographic characteristics and surgical data, including concomitant surgical procedures, were collected. Clinical outcomes recorded included return-to-sport rates, complications, reoperations, and the following PRO scores: Kujala knee score, Patient-Reported Outcomes Measurement Information System (PROMIS) Pain Interference score, and PROMIS Physical Function score.

RESULTS

Forty-one knees with a mean age of 23.4 ± 9.7 years and mean follow-up period of 30.3 months (range, 12-107 months) were included. The mean postoperative PROMIS Pain Interference, PROMIS Physical Function, and Kujala knee scores were 47.4 ± 7.7, 52.2 ± 10.8, and 81.7 ± 16.1, respectively, reflecting low residual anterior knee pain and a return to normal function. For patients playing organized sports at the high school and collegiate levels, the overall return-to-sport rate was 100% (17 of 17). During follow-up, complications developed in 12 knees (29.3%), the most common of which was anterior-based knee pain, and 6 knees (14.6%) required a total of 8 reoperations, which occurred from 6 to 32 months postoperatively.

CONCLUSIONS

The 100% return-to-sport rate and satisfactory PRO scores in our study suggest that PJAC allograft transplantation can effectively address patellofemoral cartilage defects in many patients. The complication and reoperation rates of 29.3% and 14.6%, respectively, are consistent with the challenging and heterogeneous etiology and treatment of patellofemoral articular defects.

LEVEL OF EVIDENCE

Level IV, case series.

Management of chondral and osteochondral lesions of the hip : A comprehensive review

Chondral and osteochondral lesions encompass several acute or chronic defects of the articular cartilage and/or subchondral bone. These lesions can result from several different diseases and injuries, including osteochondritis dissecans, osteochondral defects, osteochondral fractures, subchondral bone osteonecrosis, and insufficiency fractures. As the cartilage has a low capacity for regeneration and self-repair, these lesions can progress to osteoarthritis. This study provides a comprehensive overview of the subject matter that it covers. PubMed, Scopus and Google Scholar were accessed using the following keywords: "chondral lesions/defects of the femoral head", "chondral/cartilage lesions/defects of the acetabulum", "chondral/cartilage lesions/defects of the hip", "osteochondral lesions of the femoral head", "osteochondral lesions of the acetabulum", "osteochondral lesions of the hip", "osteochondritis dissecans," "early osteoarthritis of the hip," and "early stage avascular necrosis". Hip osteochondral injuries can cause significant damage to the articular surface and diminish the quality of life. It can be difficult to treat such injuries, especially in patients who are young and active. Several methods are used to treat chondral and osteochondral injuries of the hip, such as mesenchymal stem cells and cell-based treatment, surgical repair, and microfractures. Realignment of bony anatomy may also be necessary for optimal outcomes. Despite several treatments being successful, there is a lack of head-to-head comparisons and large sample size studies in the current literature. Additional research will be required to provide appropriate clinical recommendations for treating chondral/osteochondral injuries of the hip joint.

Platelet-rich plasma in orthopedics: Bridging innovation and clinical applications for bone repair

In the burgeoning domain of orthopedic therapeutic research, Platelet-Rich Plasma (PRP) has firmly established its position, transforming paradigms ranging from tissue regeneration to the management of chondral lesions. This review delves into PRP's recent integrations with cutting-edge interventions such as 3D-printed scaffolds, its role in bone and cartilage defect management, and its enhanced efficacy when combined with molecules like Kartogenin (KGN) for fibrocartilage zone repair. Significant attention is paid to tissue engineering for meniscal interventions, where a combination of KGN, PRP, and bone marrow-derived mesenchymal stem cells are under exploration. Within the sphere of osteochondral regenerative therapy, the synergy of PRP with Bone Marrow Aspirate Concentrate (BMAC) represents a noteworthy leap towards cartilage regeneration. The innovative incorporation of PRP with biomaterials like hydroxyapatite and graphene oxide further underscores its versatility in supporting structural integrity and ensuring sustained growth factor release. However, while PRP's autologous and nontoxic nature makes it an inherently safe option, concerns arising from its preparation methods, particularly with bovine thrombin, necessitate caution. As of 2023, despite the burgeoning promise of PRP in bone healing, the quest for its standardization, optimization, and substantiation through rigorous clinical trials continues. This comprehensive review elucidates the contemporary applications, challenges, and future trajectories of PRP in orthopedics, aiming to spotlight areas primed for further research and exploration.

Cell Therapy Approaches for Articular Cartilage Regeneration

Articular cartilage is a common cartilage type found in a multitude of joints throughout the human body. However, cartilage is limited in its regenerative capacity. A range of methods have been employed to aid adults under the age of 45 with cartilage defects, but other cartilage pathologies such as osteoarthritis are limited to non-steroidal anti-inflammatory drugs and total joint arthroplasty. Cell therapies and synthetic biology can be utilized to assist not only cartilage defects but have the potential as a therapeutic approach for osteoarthritis as well. In this review, we will cover current cell therapy approaches for cartilage defect regeneration with a focus on autologous chondrocyte implantation and matrix autologous chondrocyte implantation. We will then discuss the potential of stem cells for cartilage repair in osteoarthritis and the use of synthetic biology to genetically engineer cells to promote cartilage regeneration and potentially reverse osteoarthritis.

Return to Play After Knee Articular Cartilage Restoration: Surgical Options, Rehabilitation Protocols, and Performance Outcomes

PURPOSE OF REVIEW

Numerous cartilage restoration techniques have proven to be effective in the treatment of articular cartilage defects. The ultimate goal of these procedures is to improve pain and function, thereby increasing the likelihood of a patient's return to physical activity. Postoperative rehabilitation is a key component for a successful and expedient return to activities. The purpose of this article is to review the current literature regarding common surgical options, rehabilitation protocols, and performance outcomes after operative treatment of articular cartilage defects.

RECENT FINDINGS

Studies have demonstrated improved short- to long-term outcomes in a majority of techniques. However, the clinical benefits of microfracture are short-lived, which has led to the use of alternative procedures. Rehabilitation protocols are not standardized, but emphasis has been placed on bracing, weightbearing, early continuous passive range of motion, and strengthening to improve function. There is growing evidence to suggest that accelerated rehabilitation after matrix-induced autologous chondrocyte implantation may result in superior outcomes compared to delayed rehabilitation. Overall, most techniques result in satisfactory rates of return to play, though existing comparative studies typically include patients with heterogeneous pathology, complicating effective synthesis of outcomes data. In appropriately selected patients, cartilage restoration procedures after articular cartilage injury result in favorable patient-reported clinical outcomes and high rates of return to play. While studies emphasize the critical role that rehabilitation plays with respect to outcomes after surgery, there are substantial inconsistencies in protocols across techniques.

Decellularized allogeneic cartilage paste with human costal cartilage and crosslinked hyaluronic acid-carboxymethyl cellulose carrier augments microfracture for improved articular cartilage repair

Articular cartilage lacks natural healing abilities and necessitates surgical treatments for injuries. While microfracture (MF) is a primary surgical approach, it often results in the formation of unstable fibrocartilage. Delivering hyaline cartilage directly to defects poses challenges due to the limited availability of autologous cartilage and difficulties associated with allogeneic cartilage delivery. We developed a decellularized allogeneic cartilage paste (DACP) using human costal cartilage mixed with a crosslinked hyaluronic acid (HA)-carboxymethyl cellulose (CMC) carrier. The decellularized allogeneic cartilage preserved the extracellular matrix and the nanostructure of native hyaline cartilage. The crosslinked HA-CMC carrier provided shape retention and moldability. In vitro studies confirmed that DACP did not cause cytotoxicity and promoted migration, proliferation, and chondrogenic differentiation of human bone marrow-derived mesenchymal stem cells. After 6 months of implantation in rabbit knee osteochondral defects, DACP combined with MF outperformed MF alone, demonstrating improved gait performance, defect filling, morphology, extracellular matrix deposition, and biomechanical properties similar to native cartilage. Thus, DACP offers a safe and effective method for articular cartilage repair, representing a promising augmentation to MF. STATEMENT OF SIGNIFICANCE: Directly delivering hyaline cartilage to repair articular cartilage defects is an ideal treatment. However, current allogeneic cartilage products face delivery challenges. In this study, we developed a decellularized allogeneic cartilage paste (DACP) by mixing human costal cartilage with crosslinked hyaluronic acid (HA)-carboxymethyl cellulose (CMC). DACP preserves extracellular matrix components and nanostructures similar to native cartilage, with HA-CMC ensuring shape retention and moldability. Our study demonstrates improved cartilage repair by combining DACP with microfracture, compared to microfracture alone, in rabbit knee defects over 6 months. This is the first report showing better articular cartilage repair using decellularized allogeneic cartilage with microfracture, without the need for exogenous cells or bioactive substances.

Microdrilling Resulted in Less Subchondral Bone Destruction Than a Traditional Microfracture Awl for Articular Cartilage Defect Bone Marrow Stimulation

Purpose

The purpose of this study was to compare bone marrow stimulation using micro-computed tomography (micro-CT) analysis of an abrasion arthroplasty technique, drilling k-wire technique, traditional microfacture awl, or a microdrill instrument for subchondral bone defects.

Methods

Eleven cadaveric distal femoral specimens were obtained and divided into 3 common areas of osteochondral defect: trochlea and weightbearing portions of the medial and lateral femoral condyles. Each area of interest was then denuded of cartilage using a PoweRasp and divided into quadrants. Each quadrant was assigned either a 1.6 mm Kirschner wire (k-wire), 1.25 mm microfracture awl, 1.5 mm fluted microdrill, PowerPick, or a curette (abrasion arthroplasty) to create 4 channels into the subchondral bone sing the same instrument. Subchondral bone and adjacent tissue areas were then evaluated using micro-CT to analyze adjacent bone destruction and extension into the bone marrow.

Results

Overall, there was a significantly decreased area of bone destruction or compression using the microdrill (0.030 mm) as compared to the microfracture awl (0.072 mm) and k-wire (0.062 mm) (P < .05). Within the trochlea and the medial femoral condyle, there was significantly decreased bony compression with the microdrill as compared to the awl and k-wire (P < .05); however, when stratified, this was not significant among the lateral femoral condylar samples (P = .08).

Conclusion

Bone marrow stimulation causes bony compression that may negatively impact subchondral bone and trabecular alignment. It is important to understand which tools used for bone marrow stimulation cause the least amount of damage to the subchondral bone.

Clinical Relevance

This study demonstrates the decreased subchondral bony defects seen with the microdrill versus the traditional microfracture awl indicating that when performing bone marrow stimulation, the microdrill may be a less harmful tool to the subchondral bone.

Mincing bovine articular cartilage with commercially available shavers reduces the viability of chondrocytes compared to scalpel mincing

PURPOSE

The study aimed to compare the effect of mincing bovine articular cartilage with different shaver blades on chondrocyte viability.

METHODS

Bovine articular cartilage was harvested either with a scalpel or with three different shaver blades (2.5 mm, 3.5 mm, or 4.2 mm) from a commercially available shaver. The cartilage harvested with a scalpel was then minced into fragments smaller than 1 mm3 with a scalpel. All four conditions were cultivated in a culture medium for seven days. After Day 1 and Day 7, the following measurements were performed: metabolic activity, RNA isolation, and gene expression of anabolic (COL2A1 and ACAN) and catabolic genes (MMP1 and MMP13), live/dead staining and visualization using confocal microscopy, and flow cytometric characterization of minced cartilage chondrocytes.

RESULTS

Mincing the cartilage with shavers significantly reduced metabolic activity after one and seven days compared to scalpel mincing (p < 0.001). Gene expression of anabolic genes (COL2A1 and ACAN) was reduced, while catabolic genes (MMP1 and MMP13) were increased after day 7 in all shaver conditions. Confocal microscopy showed a thin line of dead cells at the lesion side with viable cells beneath for the scalpel mincing and a higher number of dead cells diffusely distributed in the shaver conditions. After seven days, there was a significant decrease in viable cells in the shaver conditions compared to scalpel mincing (p < 0.05). Flow cytometric characterization revealed fewer intact cells and proportionally more dead cells in all shaver conditions compared to the scalpel mincing.

CONCLUSION

Mincing bovine articular cartilage with commercially available shavers reduces the viability of chondrocytes compared to scalpel mincing immediately after harvest and after seven days in culture. This suggests that mincing cartilage with a shaver should be considered a matrix rather than a cell therapy.

LEVEL OF EVIDENCE

Level II therapeutic study.

Cartilage Defect Treatment Using High-Density Autologous Chondrocyte Implantation (HD-ACI)

Hyaline cartilage's inability to self-repair can lead to osteoarthritis and joint replacement. Various treatments, including cell therapy, have been developed for cartilage damage. Autologous chondrocyte implantation (ACI) is considered the best option for focal chondral lesions. In this article, we aimed to create a narrative review that highlights the evolution and enhancement of our chondrocyte implantation technique: High-Density-ACI (HD-ACI) Membrane-assisted Autologous Chondrocyte Implantation (MACI) improved ACI using a collagen membrane as a carrier. However, low cell density in MACI resulted in softer regenerated tissue. HD-ACI was developed to improve MACI, implanting 5 million chondrocytes per cm2, providing higher cell density. In animal models, HD-ACI formed hyaline-like cartilage, while other treatments led to fibrocartilage. HD-ACI was further evaluated in patients with knee or ankle defects and expanded to treat hip lesions and bilateral defects. HD-ACI offers a potential solution for cartilage defects, improving outcomes in regenerative medicine and cell therapy. HD-ACI, with its higher cell density, shows promise for treating chondral defects and advancing cartilage repair in regenerative medicine and cell therapy.

Recent development in multizonal scaffolds for osteochondral regeneration

Osteochondral (OC) repair is an extremely challenging topic due to the complex biphasic structure and poor intrinsic regenerative capability of natural osteochondral tissue. In contrast to the current surgical approaches which yield only short-term relief of symptoms, tissue engineering strategy has been shown more promising outcomes in treating OC defects since its emergence in the 1990s. In particular, the use of multizonal scaffolds (MZSs) that mimic the gradient transitions, from cartilage surface to the subchondral bone with either continuous or discontinuous compositions, structures, and properties of natural OC tissue, has been gaining momentum in recent years. Scrutinizing the latest developments in the field, this review offers a comprehensive summary of recent advances, current hurdles, and future perspectives of OC repair, particularly the use of MZSs including bilayered, trilayered, multilayered, and gradient scaffolds, by bringing together onerous demands of architecture designs, material selections, manufacturing techniques as well as the choices of growth factors and cells, each of which possesses its unique challenges and opportunities.

Current and Novel Therapeutics for Articular Cartilage Repair and Regeneration

Articular cartilage repair is a sophisticated process that has is being recently investigated. There are several different approaches that are currently reported to promote cartilage repair, like cell-based therapies, biologics, and physical therapy. Cell-based therapies involve the using stem cells or chondrocytes, which make up cartilage, to promote the growth of new cartilage. Biologics, like growth factors, are also being applied to enhance cartilage repair. Physical therapy, like exercise and weight-bearing activities, can also be used to promote cartilage repair by inducing new cartilage growth and improving joint function. Additionally, surgical options like osteochondral autograft, autologous chondrocyte implantation, microfracture, and others are also reported for cartilage regeneration. In the current literature review, we aim to provide an up-to-date discussion about these approaches and discuss the current research status.

Failure of cartilage regeneration: emerging hypotheses and related therapeutic strategies

Osteoarthritis (OA) is a disabling condition that affects billions of people worldwide and places a considerable burden on patients and on society owing to its prevalence and economic cost. As cartilage injuries are generally associated with the progressive onset of OA, robustly effective approaches for cartilage regeneration are necessary. Despite extensive research, technical development and clinical experimentation, no current surgery-based, material-based, cell-based or drug-based treatment can reliably restore the structure and function of hyaline cartilage. This paucity of effective treatment is partly caused by a lack of fundamental understanding of why articular cartilage fails to spontaneously regenerate. Thus, research studies that investigate the mechanisms behind the cartilage regeneration processes and the failure of these processes are critical to instruct decisions about patient treatment or to support the development of next-generation therapies for cartilage repair and OA prevention. This Review provides a synoptic and structured analysis of the current hypotheses about failure in cartilage regeneration, and the accompanying therapeutic strategies to overcome these hurdles, including some current or potential approaches to OA therapy.

Applications of Stimuli-Responsive Hydrogels in Bone and Cartilage Regeneration

Bone and cartilage regeneration is an area of tremendous interest and need in health care. Tissue engineering is a potential strategy for repairing and regenerating bone and cartilage defects. Hydrogels are among the most attractive biomaterials in bone and cartilage tissue engineering, mainly due to their moderate biocompatibility, hydrophilicity, and 3D network structure. Stimuli-responsive hydrogels have been a hot topic in recent decades. They can respond to external or internal stimulation and are used in the controlled delivery of drugs and tissue engineering. This review summarizes current progress in the use of stimuli-responsive hydrogels in bone and cartilage regeneration. The challenges, disadvantages, and future applications of stimuli-responsive hydrogels are briefly described.

A guide to preclinical evaluation of hydrogel-based devices for treatment of cartilage lesions

The drive to develop cartilage implants for the treatment of major defects in the musculoskeletal system has resulted in a major research thrust towards developing biomaterial devices for cartilage repair. Investigational devices for the restoration of articular cartilage are considered as significant risk materials by regulatory bodies and therefore proof of efficacy and safety prior to clinical testing represents a critical phase of the multidisciplinary effort to bridge the gap between bench and bedside. To date, review articles have thoroughly covered different scientific facets of cartilage engineering paradigm, but surprisingly, little attention has been given to the preclinical considerations revolving around the validation of a biomaterial implant. Considering hydrogel-based cartilage products as an example, the present review endeavors to provide a summary of the critical prerequisites that such devices should meet for cartilage repair, for successful implantation and subsequent preclinical validation prior to clinical trials. Considerations pertaining to the choice of appropriate animal model, characterization techniques for the quantitative and qualitative outcome measures, as well as concerns with respect to GLP practices are also extensively discussed. This article is not meant to provide a systematic review, but rather to introduce a device validation-based roadmap to the academic investigator, in anticipation of future healthcare commercialization. STATEMENT OF SIGNIFICANCE: There are significant challenges around translation of in vitro cartilage repair strategies to approved therapies. New biomaterial-based devices must undergo exhaustive investigations to ensure their safety and efficacy prior to clinical trials. These considerations are required to be applied from early developmental stages. Although there are numerous research works on cartilage devices and their in vivo evaluations, little attention has been given into the preclinical pathway and the corresponding approval processes. With a focus on hydrogel devices to concretely illustrate the preclinical path, this review paper intends to highlight the various considerations regarding the preclinical validation of hydrogel devices for cartilage repair, from regulatory considerations, to implantation strategies, device performance aspects and characterizations.

Prognostic Factors for the Clinical Outcome after Microfracture Treatment of Chondral and Osteochondral Defects in the Knee Joint: A Systematic Review

OBJECTIVE

The objective of this study is to establish which patient and lesion characteristics are related to the clinical outcome after microfracture of cartilage defects in the knee.

STUDY DESIGN

Systematic review.

METHODS

After preregistration, PubMed, Embase, and Cochrane were searched for studies that analyzed prognostic factors for the outcome of microfracture treatment in the knee. The criteria for inclusion were outcome measured using Patient-Reported Outcome Measures (PROMs), a clinical study with ≥10 participants receiving microfracture, and a minimal follow-up period of 1 year.

RESULTS

For none of the investigated prognostic factors, effect size reporting was sufficiently homogeneous to conduct a meta-analysis. However, a majority of the included studies identified higher age, larger lesion size, longer preoperative symptom duration, and previous surgery on the ipsilateral knee, especially meniscectomy and anterior cruciate ligament reconstruction, as factors that are reported to be correlated to a less favorable outcome. A lesion location that does not include the trochlea or the patellofemoral joint and is not weightbearing, a nondegenerative mechanism of injury, and a single lesion were reported as factors that predict a favorable outcome. As to gender, body mass index, preoperative activity level, smoking, and concomitant knee surgery, the included articles were inconclusive or no effect was reported.

CONCLUSIONS

Several factors correlated with the clinical result after microfracture treatment. However, the information on the effect sizes of the influence on clinical outcome is incomplete due to poor reporting. Large-scale registries or pooling of homogeneous, well-reported data is needed to work toward prognostic models. That would be an important step toward personalized treatment.

Progress and prospect of technical and regulatory challenges on tissue-engineered cartilage as therapeutic combination product

Hyaline cartilage plays a critical role in maintaining joint function and pain. However, the lack of blood supply, nerves, and lymphatic vessels greatly limited the self-repair and regeneration of damaged cartilage, giving rise to various tricky issues in medicine. In the past 30 years, numerous treatment techniques and commercial products have been developed and practiced in the clinic for promoting defected cartilage repair and regeneration. Here, the current therapies and their relevant advantages and disadvantages will be summarized, particularly the tissue engineering strategies. Furthermore, the fabrication of tissue-engineered cartilage under research or in the clinic was discussed based on the traid of tissue engineering, that is the materials, seed cells, and bioactive factors. Finally, the commercialized cartilage repair products were listed and the regulatory issues and challenges of tissue-engineered cartilage repair products and clinical application would be reviewed.

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Tissue engineered cartilage, a promising strategy for articular cartilage repair.

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Nearly 20 engineered cartilage repair products in clinic based on clinical techniques.

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Combination product, the classification of tissue-engineered cartilage.

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Key regulatory compliance issues for combination products.

Cost Effectiveness of Allogeneic Umbilical Cord Blood-Derived Mesenchymal Stem Cells in Patients with Knee Osteoarthritis

OBJECTIVES

The aim of this study was to assess the cost effectiveness of allogeneic umbilical cord blood-derived mesenchymal stem cells with sodium hyaluronate (hUCB-MSC) compared with microfracture in patients with knee cartilage defects caused by osteoarthritis (OA) in South Korea.

METHODS

A partitioned survival model approach was taken consisting of five mutually exclusive health states: excellent, good, fair, poor, and death over a 20-year time horizon. Utility values were obtained from a randomized clinical trial. Cost data were extracted from a database provided by the Health Insurance Review & Assessment Service, and the utilization of healthcare services was estimated from an expert panel of orthopedic surgeons using a structured questionnaire. The incremental cost-effectiveness ratio (ICER) in terms of quality-adjusted life-years (QALY) was calculated. Deterministic and probabilistic sensitivity analyses were performed.

RESULTS

In the base case, the incremental costs of US$14,410 for hUCB-MSC therapy along with its associated QALY gain of 0.857 resulted in an ICER of US$16,812 (₩18,790,773) per QALY (95% confidence interval [CI] US$13,408-US$20,828) when compared with microfracture treatment from a healthcare payer perspective. From a societal perspective, the ICER was US$268 (₩299,255) per QALY (95% CI -US$2915 to US$3784). When using a willingness-to-pay threshold of US$22,367/QALY, the probability of hUCB being cost effectiveness compared with microfracture was 99% from the healthcare payer perspective and 100% from the societal perspective.

CONCLUSIONS

The study demonstrated that hUCB-MSC therapy was cost effective compared with microfracture when treating patients with knee OA. These findings should inform health policy decision makers about considerations for cost-effective therapy for treating knee OA to ultimately enhance population health.

Long-term cost-effectiveness of matrix-associated chondrocyte implantation in the German health care system: a discrete event simulation

INTRODUCTION

Cartilage defects in the knee can be caused by injury, various types of arthritis, or degeneration. As a long-term consequence of cartilage defects, osteoarthritis can develop over time, often leading to the need for a total knee replacement (TKR). The treatment alternatives of chondral defects include, among others, microfracture, and matrix-associated autologous chondrocyte implantation (M-ACI). The purpose of this study was to determine cost-effectiveness of M-ACI in Germany with available mid- and long-term outcome data, with special focus on the avoidance of TKR.

MATERIALS AND METHODS

We developed a discrete-event simulation (DES) that follows up individuals with cartilage defects of the knee over their lifetimes. The DES was conducted with a status-quo scenario in which M-ACI is available and a comparison scenario with no M-ACI available. The model included 10,000 patients with articular cartilage defects. We assumed Weibull distributions for short- and long-term effects for implant failures. Model outcomes were costs, number of TKRs, and quality-adjusted life years (QALYs). All analyses were performed from the perspective of the German statutory health insurance.

RESULTS

The majority of patients was under 45 years old, with defect sizes between 2 and 7 cm² (mean: 4.5 cm²); average modeled lifetime was 48 years. In the scenario without M-ACI, 26.4% of patients required a TKR over their lifetime. In the M-ACI scenario, this was the case in only 5.5% of cases. Thus, in the modeled cohort of 10,000 patients, 2700 TKRs, including revisions, could be avoided. Patients treated with M-ACI experienced improved quality of life (22.53 vs. 21.21 QALYs) at higher treatment-related costs (18,589 vs. 14,134 € /patient) compared to those treated without M-ACI, yielding an incremental cost-effectiveness ratio (ICER) of 3376 € /QALY.

CONCLUSION

M-ACI is projected to be a highly cost-effective treatment for chondral defects of the knee in the German healthcare setting.

Navigating regulatory pathways for translation of biologic cartilage repair products

Long-term clinical repair of articular cartilage remains elusive despite advances in cartilage tissue engineering. Only one cartilage repair therapy classified as a "cellular and gene therapy product" has obtained Food and Drug Administration (FDA) approval within the past decade although more than 200 large animal cartilage repair studies were published. Here, we identify the challenges impeding translation of strategies and technologies for cell-based cartilage repair, such as the disconnect between university funding and regulatory requirements. Understanding the barriers to translation and developing solutions to address them will be critical for advancing cell therapy products for cartilage repair to clinical use.

Creating an Optimal In Vivo Environment to Enhance Outcomes Using Cell Therapy to Repair/Regenerate Injured Tissues of the Musculoskeletal System

Following most injuries to a musculoskeletal tissue which function in unique mechanical environments, an inflammatory response occurs to facilitate endogenous repair. This is a process that usually yields functionally inferior scar tissue. In the case of such injuries occurring in adults, the injury environment no longer expresses the anabolic processes that contributed to growth and maturation. An injury can also contribute to the development of a degenerative process, such as osteoarthritis. Over the past several years, researchers have attempted to use cellular therapies to enhance the repair and regeneration of injured tissues, including Platelet-rich Plasma and mesenchymal stem/medicinal signaling cells (MSC) from a variety of tissue sources, either as free MSC or incorporated into tissue engineered constructs, to facilitate regeneration of such damaged tissues. The use of free MSC can sometimes affect pain symptoms associated with conditions such as OA, but regeneration of damaged tissues has been challenging, particularly as some of these tissues have very complex structures. Therefore, implanting MSC or engineered constructs into an inflammatory environment in an adult may compromise the potential of the cells to facilitate regeneration, and neutralizing the inflammatory environment and enhancing the anabolic environment may be required for MSC-based interventions to fulfill their potential. Thus, success may depend on first eliminating negative influences (e.g., inflammation) in an environment, and secondly, implanting optimally cultured MSC or tissue engineered constructs into an anabolic environment to achieve the best outcomes. Furthermore, such interventions should be considered early rather than later on in a disease process, at a time when sufficient endogenous cells remain to serve as a template for repair and regeneration. This review discusses how the interface between inflammation and cell-based regeneration of damaged tissues may be at odds, and outlines approaches to improve outcomes. In addition, other variables that could contribute to the success of cell therapies are discussed. Thus, there may be a need to adopt a Precision Medicine approach to optimize tissue repair and regeneration following injury to these important tissues.

Adjacent cartilage tissue structure after successful transplantation: a quantitative MRI study using T2 mapping and texture analysis

OBJECTIVES

The aim of this study was to assess the texture of repair tissue and tissue adjacent to the repair site after matrix-associated chondrocyte transplantation (MACT) of the knee using gray-level co-occurrence matrix (GLCM) texture analysis of T₂ quantitative maps.

METHODS

Twenty patients derived from the MRI sub-study of multicenter, single-arm phase III study underwent examination on a 3 T MR scanner, including a T₂ mapping sequence 12 and 24 months after MACT. Changes between the time points in mean T₂ values and 20 GLCM features were assessed for repair tissue, adjacent tissue, and reference cartilage. Differences in T₂ values and selected GLCM features between the three cartilage sites at two time points were analyzed using linear mixed-effect models.

RESULTS

A significant decrease in T₂ values after MACT, between time points, was observed only in repair cartilage (p < 0.001). Models showed significant differences in GLCM features between repair tissue and reference cartilage, namely, autocorrelation (p < 0.001), correlation (p = 0.015), homogeneity (p = 0.002), contrast (p < 0.001), and difference entropy (p = 0.047). The effect of time was significant in a majority of models with regard to GLCM features (except autocorrelation) (p ≤ 0.001). Values in repair and adjacent tissue became similar to reference tissue over time.

CONCLUSIONS

GLCM is a useful add-on to T₂ mapping in the evaluation of knee cartilage after MACT by increasing the sensitivity to changes in cartilage structure. The results suggest that cartilage tissue adjacent to the repair site heals along with the cartilage implant.

KEY POINTS

• GLCM is a useful add-on to T₂ mapping in the evaluation of knee cartilage after MACT by increasing the sensitivity to changes in cartilage structure. • Repair and adjacent tissue became similar to reference tissue over time. • The results suggest that cartilage tissue adjacent to the repair site heals along with the cartilage implant.

Platelet-Rich Plasma and Adipose-Derived Mesenchymal Stem Cells in Association with Arthroscopic Microfracture of Knee Articular Cartilage Defects: A Pilot Randomized Controlled Trial

Background

This study aims to compare the effects of platelet-rich plasma (PRP) alone or in combination with adipose-derived mesenchymal stem cells (AD-MSCs) in patients affected by cartilage defects, undergoing knee arthroscopic microfracture.

Methods

Thirty-eight patients diagnosed with a knee monocompartmental cartilage defect (Outerbridge grade IV) on the MRI, underwent an arthroscopic procedure. After the confirmation of the lesion, they all received the same bone marrow stimulation technique (microfracture) and were randomized into two groups: the first one had additional PRP injection (group A), while the second received PRP and AD-MSC injection (group B). Knee assessment and pain score were documented with Knee Injury Osteoarthritis Outcome Score (KOOS), International Knee Documentation Committee (IKDC) score, Short-Form (SF) 12, and Visual Analogue Scale (VAS) before the treatment and at 1, 3, 6, and 12 months of follow-up postoperatively. An additional arthroscopic procedure, performed in four patients for a subsequent meniscal lesion, let us evaluate cartilage evolution by performing a macro/microscopical assessment on cartilage biopsy specimens.

Results

At the 12-month follow-up, both groups showed a comparable functional improvement. The scores on the IKDC form, KOOS, pain VAS, and SF-12 significantly improved from baseline (p < 0.05) to 12 months postoperatively in both treatment groups. The four second-look arthroscopies showed a complete repair of the articular defects by smooth solid cartilage layer, with a good chondrocytic population, in both groups. A thick smooth hyaline-like cartilage with a predominantly viable cell population and normal mineralization (a form closely resembling native tissue) was observed in group B.

Conclusions

Modern regenerative medicine techniques, such as PRP and AD-MSC, associated with traditional arthroscopic bone marrow stimulating techniques, seem to enhance cartilage restoration ability. The preliminary results of this pilot study encourage the synergic use of these regenerative modulating systems to improve the quality of the regenerated cartilage.

NFκB inhibition to lift the mechano-competence of mesenchymal stromal cell-derived neocartilage toward articular chondrocyte levels

Background

Fully functional regeneration of skeletal defects by multipotent progenitor cells requires that differentiating cells gain the specific mechano-competence needed in the target tissue. Using cartilage neogenesis as an example, we asked whether proper phenotypic differentiation of mesenchymal stromal cells (MSC) into chondrocytes in vitro will install the adequate biological mechano-competence of native articular chondrocytes (AC).

Methods

The mechano-competence of human MSC- and AC-derived neocartilage was compared during differentiation for up to 35 days. The neocartilage layer was subjected to physiologic dynamic loading in a custom-designed bioreactor and assayed for mechano-sensitive gene and pathway activation, extracellular matrix (ECM) synthesis by radiolabel incorporation, nitric oxide (NO) and prostaglandin E₂ (PGE₂) production. Input from different pathways was tested by application of agonists or antagonists.

Results

MSC and AC formed neocartilage of similar proteoglycan content with a hardness close to native tissue. Mechano-stimulation on day 21 and 35 induced a similar upregulation of mechano-response genes, ERK phosphorylation, NO production and PGE₂ release in both groups, indicating an overall similar transduction of external mechanical signals. However, while AC maintained or enhanced proteoglycan synthesis after loading dependent on tissue maturity, ECM synthesis was always significantly disturbed by loading in MSC-derived neocartilage. This was accompanied by significantly higher COX2 and BMP2 background expression, > 100-fold higher PGE₂ production and a weaker SOX9 stimulation in response to loading in MSC-derived neocartilage. Anabolic BMP-pathway activity was not rate limiting for ECM synthesis after loading in both groups. However, NFκB activation mimicked the negative loading effects and enhanced PGE₂ production while inhibition of catabolic NFκB signaling rescued the load-induced negative effects on ECM synthesis in MSC-derived neocartilage.

Conclusions

MSC-derived chondrocytes showed a higher vulnerability to be disturbed by loading despite proper differentiation and did not acquire an AC-like mechano-competence to cope with the mechanical stress of a physiologic loading protocol. Managing catabolic NFκB influences was one important adaptation to install a mechano-resistance closer to AC-derived neocartilage. This new knowledge asks for a more functional adaptation of MSC chondrogenesis, novel pharmacologic co-treatment strategies for MSC-based clinical cartilage repair strategies and may aid a more rational design of physical rehabilitation therapy after AC- versus MSC-based surgical cartilage intervention.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02843-x.

Optimization of loading protocols for tissue engineering experiments

Tissue engineering (TE) combines cells and biomaterials to treat orthopedic pathologies. Maturation of de novo tissue is highly dependent on local mechanical environments. Mechanical stimulation influences stem cell differentiation, however, the role of various mechanical loads remains unclear. While bioreactors simplify the complexity of the human body, the potential combination of mechanical loads that can be applied make it difficult to assess how different factors interact. Human bone marrow-derived mesenchymal stromal cells were seeded within a fibrin-polyurethane scaffold and exposed to joint-mimicking motion. We applied a full factorial design of experiment to investigate the effect that the interaction between different mechanical loading parameters has on biological markers. Additionally, we employed planned contrasts to analyze differences between loading protocols and a linear mixed model with donor as random effect. Our approach enables screening of multiple mechanical loading combinations and identification of significant interactions that could not have been studied using classical mechanobiology studies. This is useful to screen the effect of various loading protocols and could also be used for TE experiments with small sample sizes and further combinatorial medication studies.

Design and clinical application of injectable hydrogels for musculoskeletal therapy

Musculoskeletal defects are an enormous healthcare burden and source of pain and disability for individuals. With an aging population, the proportion of individuals living with these medical indications will increase. Simultaneously, there is pressure on healthcare providers to source efficient solutions, which are cheaper and less invasive than conventional technology. This has led to an increased research focus on hydrogels as highly biocompatible biomaterials that can be delivered through minimally invasive procedures. This review will discuss how hydrogels can be designed for clinical translation, particularly in the context of the new European Medical Device Regulation (MDR). We will then do a deep dive into the clinically used hydrogel solutions that have been commercially approved or have undergone clinical trials in Europe or the United States. We will discuss the therapeutic mechanism and limitations of these products. Due to the vast application areas of hydrogels, this work focuses only on treatments of cartilage, bone, and the nucleus pulposus. Lastly, the main steps toward clinical translation of hydrogels as medical devices are outlined. We suggest a framework for how academics can assist small and medium MedTech enterprises conducting the initial clinical investigation and post‐market clinical follow‐up required in the MDR. It is evident that the successful translation of hydrogels is governed by acquiring high‐quality pre‐clinical and clinical data confirming the device mechanism of action and safety.

Differences in the Demographics and Preferred Management of Knee Cartilage Injuries in Soccer Players Across FIFA Centers of Excellence

OBJECTIVE

We sought to report on the demographics and epidemiology of knee cartilage injuries and preferred management in soccer players, across FIFA Medical Centers of Excellence (FMCE).

DESIGN

A descriptive questionnaire focusing on characteristics of knee cartilage injuries and their management in soccer players during the 10-year period prior to the distribution of the questionnaire was sent to all FMCE around the world in September 2019 via an online platform. Voluntary responses from centers were processed and analyzed. Descriptive characteristics were reported using median and interquartile ranges (IQR) for continuous variables and frequencies and percentages (%) for discrete variables.

RESULTS

A total of 15 centers from 5 continents responded to the questionnaire and reported on a total of 4526 soccer players. Among centers, the median age was 27 years (IQR: 23-38), the median rate of male players was 75% (IQR: 68-90), and the median rate of professional players was 10% (IQR: 5-23). The most common reported etiology for cartilage injury was traumatic (median 40%, IQR: 13-73). The most common nonoperative treatment utilized was physical therapy (median 90%, IQR: 51%-100%) and the most common operative treatment utilized was bone marrow stimulation/micro-fracture (median 40%, IQR: 19-54%). The utilization of other cartilage restoration procedures varied across centers.

CONCLUSIONS

Our findings highlight different tendencies in the management of these injuries across FMCE and emphasize the need for collaborative efforts focusing on establishing consensus guidelines for the optimal management of these challenging injuries in soccer players.

Resorbable Pins to Enhance Scaffold Retention in a Porcine Chondral Defect Model

OBJECTIVE

Cartilage repair strategies have seen improvement in recent years, especially with the use of scaffolds that serve as a template for cartilage formation. However, current fixation strategies are inconsistent with regards to retention, may be technically challenging, or may damage adjacent tissues or the implant itself. Therefore, the goal of this study was to evaluate the retention and repair potential of cartilage scaffolds fixed with an easy-to-implement bioresorbable pin.

DESIGN

Electrospun hyaluronic acid scaffolds were implanted into trochlear groove defects in 3 juvenile and 3 adult pigs to evaluate short-term retention (2 weeks; pin fixation vs. press-fit and fibrin fixation) and long-term repair (8 months; scaffold vs. microfracture), respectively.

RESULTS

For the retention study, press-fit and fibrin fixation resulted in short-term scaffold dislodgment (n = 2 each), whereas pin fixation retained all scaffolds that were implanted (n = 6). Pin fixation did not cause any damage to the opposing patellar surface, and only minor changes in the subchondral bone were observed. For long-term repair, no differences were observed between microfracture and scaffold groups, in terms of second-look arthroscopy and indentation testing. On closer visualization with micro computed tomography and histology, a high degree of variability was observed between animals with regard to subchondral bone changes and cartilage repair quality, yet each Scaffold repair displayed similar properties to its matched microfracture control.

CONCLUSIONS

In this study, pin fixation did not cause adverse events in either the short- or the long-term relative to controls, indicating that pin fixation successfully retained scaffolds within defects without inhibiting repair.

No Effect of Platelet-Rich Plasma Injections as an Adjuvant to Autologous Cartilage Chips Implantation for the Treatment of Chondral Defects

BACKGROUND

Repair of chondral injuries using cartilage chips has recently demonstrated clinical feasibility. Autologous platelet-rich plasma (PRP) is a potential promising technique for improving healing response during cartilage repair.

PURPOSE

To assess the cartilage repair tissue quality after autologous cartilage chips treatment (CC) with and without repeated local injections of PRP for the treatment of full-thickness focal chondral defects of the knee.

MATERIALS AND METHODS

Two full-thickness chondral defects (Ø = 6 mm) were created in the medial and lateral trochlea facets of each knee in 6 skeletally mature Göttingen minipigs. The 2 treatment groups were (1) CC with 1 weekly PRP injection for 3 weeks (n = 12) and (2) CC alone (n = 12). The animals were euthanized after 6 months. Samples of whole blood and PRP were analyzed for concentrations of platelets and nucleated cells. The composition of the cartilage repair tissue was assessed using gross appearance assessment, histomorphometry, and semiquantitative scoring (ICRS II).

RESULTS

Histological evaluation demonstrated no significant difference in the content of hyaline cartilage (CC + PRP: 18.7% vs. CC: 19.6%), fibrocartilage (CC + PRP: 48.1% vs. CC: 51.8%), or fibrous tissue (CC + PRP: 22.7% vs. CC: 21.8%) between the treatment groups. Macroscopic evaluation did not demonstrate any difference between groups.

CONCLUSIONS

PRP injections after CC in the treatment of full-thickness cartilage injuries demonstrated no beneficial effects in terms of macroscopic and histologic composition of cartilage repair tissue.

The Modified Hedgehog Technique to Repair Pure Chondral Shear-off Lesions in the Pediatric Knee

OBJECTIVE

The paediatric knee is prone to pure chondral shear-off lesions due to the developing osteochondral unit. Refixation of the chondral fragment is commonly done using metalwork or absorbable biomaterials. Both fixation methods come with biomaterial-related drawbacks. Earlier work on chondral allografts for cartilage repair in adults has shown successful osteochondral integration when the chondral allograft is treated with multiple incisions and then glued to the subchondral bone using fibrin glue. This is commonly referred to as the "hedgehog technique." This study investigates the feasibility of a modification of the hedgehog technique in autologous cartilage to repair shear-off lesions in children.

DESIGN

Three consecutive patients (aged 11, 12, and 14 years) with shear-off chondral fragments of 2, 5, and 8 cm² were treated using this modified hedgehog technique. The calcified side of the chondral fragments were multiply incised and trimmed obliquely for an interlocking fit in the defect site. Fibrin glue and, if indicated sutures, were applied to fix the fragment to the defect. In 1 patient, an anterior cruciate ligament (ACL) repair was also performed. Patients were evaluated clinically and by magnetic resonance imaging (MRI) up to 12 months postoperatively.

RESULTS

Twelve months after surgery, all patients reported no pain and showed complete return to sport and full range of motion. MRI showed no signs of fragment loosening.

CONCLUSIONS

The modified hedgehog technique is a feasible treatment option to repair pure chondral shear-off lesions in the paediatric knee. This was the first time this technique was used in autografting.

A Systematic Review of Focal Cartilage Defect Treatments in Middle-Aged Versus Younger Patients

Background:

Focal cartilage defects are often debilitating, possess limited potential for regeneration, are associated with increased risk of osteoarthritis, and are predictive for total knee arthroplasty. Cartilage repair studies typically focus on the outcome in younger patients, but a high proportion of treated patients are 40 to 60 years of age (ie, middle-aged). The reality of current clinical practice is that the ideal patient for cartilage repair is not the typical patient. Specific attention to cartilage repair outcomes in middle-aged patients is warranted.

Purpose:

To systematically review available literature on knee cartilage repair in middle-aged patients and include studies comparing results across different age groups.

Study Design:

Systematic review; Level of evidence, 4.

Methods:

A systematic search was performed in EMBASE, MEDLINE, and the Cochrane Library database. Articles were screened for relevance and appraised for quality.

Results:

A total of 21 articles (mean Coleman Methodology Score, 64 points) were included. Two out of 3 bone marrow stimulation (BMS) studies, including 1 using the microfracture technique, revealed inferior clinical outcomes in middle-aged patients in comparison with younger patients. Nine cell-based studies were included showing inconsistent comparisons of results across age groups for autologous chondrocyte implantation (ACI). Bone marrow aspirate concentrate showed age-independent results at up to 8 years of follow-up. A negative effect of middle age was reported in 1 study for both ACI and BMS. Four out of 5 studies on bone-based resurfacing therapies (allografting and focal knee resurfacing implants [FKRIs]) showed age-independent results up to 5 years. One study in only middle-aged patients reported better clinical outcomes for FKRIs when compared with biological repairs.

Conclusion:

Included studies were heterogeneous and had low methodological quality. BMS in middle-aged patients seems to only result in short-term improvements. More research is warranted to elucidate the ameliorating effects of cell-based therapies on the aging joint homeostasis. Bone-based therapies seem to be relatively insensitive to aging and may potentially result in effective joint preservation. Age subanalyses in cohort studies, randomized clinical trials, and international registries should generate more evidence for the large but underrepresented (in terms of cartilage repair) middle-aged population in the literature.

Bone marrow mononuclear cells for joint therapy: The role of macrophages in inflammation resolution and tissue repair

Osteoarthritis (OA) is the most prevalent joint disease causing major disability and medical expenditures. Synovitis is a central feature of OA and is primarily driven by macrophages. Synovial macrophages not only drive inflammation but also its resolution, through a coordinated, simultaneous expression of pro- and anti-inflammatory mechanisms that are essential to counteract damage and recover homeostasis. Current OA therapies are largely based on anti-inflammatory principles and therefore block pro-inflammatory mechanisms such as prostaglandin E₂ and Nuclear factor-kappa B signaling pathways. However, such mechanisms are also innately required for mounting a pro-resolving response, and their blockage often results in chronic low-grade inflammation. Following minor injury, macrophages shield the damaged area and drive tissue repair. If the damage is more extensive, macrophages incite inflammation recruiting more macrophages from the bone marrow to maximize tissue repair and ultimately resolve inflammation. However, sustained damage and inflammation often overwhelms pro-resolving mechanisms of synovial macrophages leading to the chronic inflammation and related tissue degeneration observed in OA. Recently, experimental and clinical studies have shown that joint injection with autologous bone marrow mononuclear cells replenishes inflamed joints with macrophage and hematopoietic progenitors, enhancing mechanisms of inflammation resolution, providing remarkable and long-lasting effects. Besides creating an ideal environment for resolution with high concentrations of interleukin-10 and anabolic growth factors, macrophage progenitors also have a direct role in tissue repair. Macrophages constitute a large part of the early granulation tissue, and further transdifferentiate from myeloid into a mesenchymal phenotype. These cells, characterized as fibrocytes, are essential for repairing osteochondral defects. Ongoing “omics” studies focused on identifying key drivers of macrophage-mediated resolution of joint inflammation and those required for efficient osteochondral repair, have the potential to uncover ways for developing engineered macrophages or off-the-shelf pro-resolving therapies that can benefit patients suffering from many types of arthropaties, not only OA.

PVA-Based Hydrogels: Promising Candidates for Articular Cartilage Repair

The complex, gradient physiological structure of articular cartilage is a severe hindrance of its self-repair, leaving the clinical treatment of cartilage defects a demanding issue to be addressed. Currently applied tissue engineering treatments and traditional non-tissue engineering treatments have different limitations, for example, cell dedifferentiation, immune rejection, and prosthesis-related complications. Thus, studies have been focusing on seeking promising candidates for novel cartilage repair methods. Polyvinyl alcohol (PVA) hydrogels with excellent biocompatibility and tunable material properties have become the alternatives. For pure PVA hydrogels, the mechanical strength and lubricity are not capable of replacing articular cartilage until proper modifications are done. This paper summarizes the research progress in PVA hydrogels, including the preparation, modification, and cartilage-repair-aimed biomimetic improvements. Design guidance of PVA hydrogels is put forward as assistance to functional hydrogel preparation. Finally, the prospects and main obstacles of PVA hydrogels are discussed.

Solubilized Cartilage ECM Facilitates the Recruitment and Chondrogenesis of Endogenous BMSCs in Collagen Scaffolds for Enhancing Microfracture Treatment

Articular cartilage has very poor intrinsic healing ability and its repair remains a significant clinical challenge. To promote neocartilage regeneration, we fabricated two collagen (Col) scaffolds functionalized with a porcine decellularized extracellular matrix (dECM) in the forms of particle and solution named pE-Col and sE-Col, respectively. Their differences were systematically compared, including the biochemical compositions, scaffold properties, cell-material interactions, and in situ cartilage regeneration. While it is demonstrated that both forms of dECM could enhance the cell recruitment, proliferation, and chondrogenesis of bone marrow stem cells (BMSCs) in vitro, better performance was seen in the sE-Col group, which could quickly provide a more favorable chondrogenic microenvironment for endogenous BMSCs. The superiority of sE-Col was also proved by our in vivo study, which showed that the sE-Col scaffold achieved better structural hyaline-like neocartilage formation and subchondral bone repair compared to the pE-Col scaffold, according to the gross morphology, biological assessment, and micro-CT imaging analysis. Together, this study suggests that the sE-Col scaffold holds great potential in developing the one-step microfracture-based strategy for cartilage repair and also reminds us that despite dECM being a promising biomaterial in tissue engineering, the optimization of the proper processing methodology would be a crucial consideration in the future design of dECM-based scaffolds in articular cartilage regeneration.

Use of human induced pluripotent stem cells for cartilage regeneration in vitro and within chondral defect models of knee joint cartilage in vivo: a Preferred Reporting Items for Systematic Reviews and Meta-Analyses systematic literature review

BACKGROUND AIMS

Articular cartilage has limited regenerative ability when damaged through trauma or disease. Failure to treat focal chondral lesions results in changes that inevitably progress to osteoarthritis. Osteoarthritis is a major contributor to disability globally, which results in significant medical costs and lost wages every year. Human induced pluripotent stem cells (hiPSCs) have long been considered a potential autologous therapeutic option for the treatment of focal chondral lesions. Although there are significant advantages to hiPSCs over other stem cell options, such as mesenchymal and embryonic stem cells, there are concerns regarding their ability to form bona fide cartilage and their tumorgenicity in vivo.

METHODS

The authors carried out a systematic literature review on the use of hiPSCs to produce differentiated progeny capable of producing high-quality cartilage in vitro and regenerate cartilage in osteochondral defects in vivo in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Eight studies were included in the review that used hiPSCs or their derived progeny in xenogeneic transplants in animal models to regenerate cartilage in osteochondral defects of the knee joint. The in vitro-differentiated, hiPSC-derived and in vivo defect repair ability of the hiPSC-derived progeny transplants were assessed.

RESULTS

Most studies reported the generation of high-quality cartilage-producing progeny that were able to successfully repair cartilage defects in vivo. No tumorigenicity was observed.

CONCLUSIONS

The authors conclude that hiPSCs offer a valuable source of cartilage-producing progeny that show promise as an effective cell-based therapy in treating focal chondral lesions.

[Update on the Operative Treatment of Cartilage Defects]

Focal cartilage defects lead to swelling, significant pain and loss of function of the affected joint. Additionally, they are linked to early onset of osteoarthritis. Often young and active patients are especially susceptible due to the high stress placed on their joints. A vast amount of treatment options is available to orthopaedic surgeons to cure cartilage defects of the knee, hip, shoulder, elbow and ankle joints. This article serves to give an overview of these available treatment options and to explain the expected outcomes.

Articular Cartilage Injuries of the Knee: Patient Health Literacy, Expectations for Management, and Clinical Outcomes

OBJECTIVE

The purpose of this article is to review the orthopedic literature regarding patient understanding of articular cartilage disease, interpret literature reporting patient expectations for surgical management of articular cartilage injuries of the knee, and review patient-reported outcomes and patient satisfaction with management of these injuries.

DESIGN

A retrospective review of the current literature using the PubMed database (1980-current) was performed on July 15, 2017. The search terms used were "patient understanding knee cartilage," "patient satisfaction knee cartilage," "patient expectation knee cartilage," and "patient reported outcomes knee cartilage." All searches were filtered to human studies and English language only and were reviewed by 2 independent reviewers. Studies not relevant to articular cartilage injury and/or surgical management in the knee were excluded. Additional references were found by backtracing references from obtained articles.

RESULTS

The published study search results for the terms: "patient understanding knee cartilage," "patient satisfaction knee cartilage," "patient expectation knee cartilage," and "patient reported outcomes knee cartilage" displayed a total of 873 studies. Two independent reviewers screen all studies A total of 50 published studies were relevant and included.

CONCLUSION

The subjective and objective clinical outcomes reported are inconsistently obtained resulting in difficulty drawing comparisons between studies. While the relationship between preoperative patient expectations and patient-reported outcomes and patient satisfaction has yet to be well developed, authors have reported patient and injury specific variables associated with superior and inferior outcomes. In conclusion, more work is needed to correlate patient-reported outcomes and satisfaction for cartilage treatments with preoperative expectations and health literacy.

Influence of the Mechanical Environment on the Regeneration of Osteochondral Defects

Articular cartilage is a highly specialised connective tissue of diarthrodial joints which provides a smooth, lubricated surface for joint articulation and plays a crucial role in the transmission of loads. In vivo cartilage is subjected to mechanical stimuli that are essential for cartilage development and the maintenance of a chondrocytic phenotype. Cartilage damage caused by traumatic injuries, ageing, or degradative diseases leads to impaired loading resistance and progressive degeneration of both the articular cartilage and the underlying subchondral bone. Since the tissue has limited self-repairing capacity due its avascular nature, restoration of its mechanical properties is still a major challenge. Tissue engineering techniques have the potential to heal osteochondral defects using a combination of stem cells, growth factors, and biomaterials that could produce a biomechanically functional tissue, representative of native hyaline cartilage. However, current clinical approaches fail to repair full-thickness defects that include the underlying subchondral bone. Moreover, when tested in vivo, current tissue-engineered grafts show limited capacity to regenerate the damaged tissue due to poor integration with host cartilage and the failure to retain structural integrity after insertion, resulting in reduced mechanical function. The aim of this review is to examine the optimal characteristics of osteochondral scaffolds. Additionally, an overview on the latest biomaterials potentially able to replicate the natural mechanical environment of articular cartilage and their role in maintaining mechanical cues to drive chondrogenesis will be detailed, as well as the overall mechanical performance of grafts engineered using different technologies.

Non-viral Gene Therapy for Osteoarthritis

Strategies for delivering nucleic acids into damaged and diseased tissues have been divided into two major areas: viral and non-viral gene therapy. In this mini-review article we discuss the application of gene therapy for the treatment of osteoarthritis (OA), one of the most common forms of arthritis. We focus primarily on non-viral gene therapy and cell therapy. We briefly discuss the advantages and disadvantages of viral and non-viral gene therapy and review the nucleic acid transfer systems that have been used for gene delivery into articular chondrocytes in cartilage from the synovial joint. Although viral gene delivery has been more popular due to its reported efficiency, significant effort has gone into enhancing the transfection efficiency of non-viral delivery, making non-viral approaches promising tools for further application in basic, translational and clinical studies on OA. Non-viral gene delivery technologies have the potential to transform the future development of disease-modifying therapeutics for OA and related osteoarticular disorders. However, further research is needed to optimize transfection efficiency, longevity and duration of gene expression.

The Role of Collagen-Based Biomaterials in Chronic Wound Healing and Sports Medicine Applications

Advancements in tissue engineering have taken aim at treating tissue types that have difficulty healing naturally. In order to achieve improved healing conditions, the balance of exogenous matrix, cells, and different factors must be carefully controlled. This review seeks to explore the aspects of tissue engineering in specific tissue types treated in sports medicine and advanced wound management from the perspective of the matrix component. While the predominant material to be discussed is collagen I, it would be remiss not to mention its relation to the other contributing factors to tissue engineered healing. The main categories of materials summarized here are (1) reconstituted collagen scaffolds, (2) decellularized matrix tissue, and (3) non-decellularized tissue. These three groups are ordered by their increase in additional components beyond simply collagen.

Bioartificial injectable cartilage implants from demineralized bone matrix/PVA and related studies in rabbit animal model

Functional cartilage tissue engineering needs a substantial, easy to handle scaffold with proper mechanical strength to repair defected area in articular cartilage. In this study, we report the development and characterization of demineralized bone matrix (DBM) in with a poly vinyl alcohol (PVA) to have a proper homogenous injectable scaffold. Injectabiliy of the biodegradable scaffolds, degradation rate, swelling ratio compression and tensile mechanical properties, and viability and proliferation of bone marrow mesenchymal stem cells (BM-MSCs) followed by differentiation of them In-vitro and In-vivo seeded within the scaffold were studied. It demonstrated that the PVA 20% could increase significantly (p < 0.05) the biodegradability of DBM after 720 hours.DBM with 20% of PVA scaffold has significantly higher (p < 0.05) compression and tensile mechanical strength and viscosity. SEM images showed a multilayer of cells on DBM scaffold incorporated with PVA 20%.BM-MSCs on scaffolds, DBM+PVA 20% had a significant growth rate (p < 0.0001) compare to 2D and low concentration of PVA after 21 days of culture. Viability of cells was significantly higher (p < 0.05) on DBM+PVA scaffold compare to DBM. DBM+PVA 20% enhanced cell viability (P < 0.05) compare to DBM scaffold. The PVA presence enhanced chondrogenesis differentiation at the cellular and molecular levels, as evidenced by increased COL II (P < 0.05) and SOX2 upregulation of Chondrogensis-specific genes (p < 0.001). Hyline-like cartilage covered the defect which was confirmed by microscopy and histology assessments. Having considered percentages of PVA with a constant amount of DBM, injectability, compressive mechanical properties, homogeneity of the scaffold, and providing sufficient surface area (12.25 cm²/ml) for cell attachment; 0.35 g/ml of DBM in 20% PVA (w/v) has applicable properties within the ranges of studies which can be proposed for the injectable engineered articular cartilage.