Biomaterials for meniscus and cartilage in knee surgery: state of the art

The effect of silk short fiber biomimetic materials on the recovery of sports function in patients with meniscal injury during sports

BackgroundIn sports, especially high-intensity and high-risk activities, the meniscus is easily damaged. For patients with meniscus injuries, it is necessary to repair or replace the patient's meniscus. However, as age increases, the human meniscus tissue gradually forms and cannot be repaired through its own meniscus. Therefore, it is necessary to maintain the patient's movement function through meniscus support materials.ObjectiveTraditional meniscus support materials have poor mechanical properties and poor biocompatibility. In response to this issue, this study designed a meniscus scaffold made of silk short fibers, silk fibroin, and wool protein.MethodsThrough electrospinning and freeze-drying techniques, the material was processed to obtain a silk short fiber meniscus with a biomimetic structure.ResultsThrough experiments, the surface morphology, hydrophobicity, porosity, secondary structure, thermal stability, water absorption swelling, and MP of MCS made of SSF biomimetic materials were characterized.ConclusionThe experimental results show that the manufactured silk short fiber meniscus has good compressive performance, thermal stability, and water absorption and swelling properties, and it also exhibits good biocompatibility.

Extrusion After Meniscal Allograft Transplantation Is Lower or Equal With Bony Compared With Soft-Tissue Root Fixation: A Systematic Review

PURPOSE

To provide an update on the incidence and extent of graft extrusion after meniscal allograft transplantation (MAT) and to systematically review the literature to identify whether the type of root fixation or additional surgical techniques may reduce the risk of graft extrusion development.

METHODS

A systematic search, in accordance with PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses) guidelines, was conducted using the MEDLINE database, EMBASE database, Cochrane Database of Systematic Reviews, and Cochrane Central Register of Controlled Trials (CENTRAL) database. Patients undergoing medial meniscal allograft transplantation (MMAT) or lateral meniscal allograft transplantation (LMAT) were included. The primary outcome measure was meniscal extrusion measured on postoperative magnetic resonance imaging scans taken more than 6 weeks after MAT. The following extrusion outcomes were investigated: absolute extrusion (AE), relative percentage of extrusion (RPE), and proportion of major extrusion (PME). Additional surgical techniques that reduced the risk of graft extrusion development in the included comparative studies were identified.

RESULTS

For MMAT, the pooled mean extrusion outcomes for soft-tissue versus bony fixation were as follows: AE of 3.2 mm versus 3.36 mm and RPE of 44.43% versus 33.18%. The pooled mean PME for MMAT with soft-tissue fixation was 51.62%. For LMAT, the pooled mean extrusion outcomes for soft-tissue versus bony fixation were as follows: AE of 3.72 mm versus 2.78 mm, RPE of 31.89% versus 29.47%, and PME of 64.37% versus 35.80%. Additional capsulodesis was identified as a technique to reduce LMAT extrusion.

CONCLUSIONS

This study highlights that graft extrusion is a common finding after MMAT and LMAT, independent of the root fixation technique. However, MAT extrusion with bony fixation was, depending on the outcome measurement, lower than or equal to that with soft-tissue fixation.

LEVEL OF EVIDENCE

Level IV, systematic review of Level I, III, and IV studies.

A nosographic and etiopathogenetic framework for subchondral bone marrow lesions in the knee: A narrative review

Purpose

Subchondral bone marrow lesions (BMLs) are present in a wide range of pathologies with different prognoses. Thus, a careful diagnosis is mandatory to address them with the proper treatment. The aim of this review was to examine BMLs aetiology and their relationship with biomechanical and biological factors, to identify BMLs and help clinicians to properly recognize and treat each of these common alterations.

Discussion

Each pathological pattern is determined by different aetiologic factors, which may act alone or synergically in determining the BML. These factors include major or minor trauma, bone tissue alterations, altered joint load distribution, coagulopathies, and hormonal alterations. This narrative review encompasses these patterns and factors providing a nosographic and etiopathogenetic framework for subchondral BMLs in the knee.

Conclusion

While the field is still heterogeneous in the definition of the nosographic framework of BMLs, there is a trend with the convergence towards a common terminology, which could help to shed more light on the complex and varied field of BMLs. Future studies should focus on better understanding the etiopathogenetic mechanisms, which can concur with the development of BML from one side, and, on the other hand, may represent targets for future treatments to address BMLs and preserve or restore the osteochondral unit.

Level of Evidence

Expert Opinion, Level V.

Knee Arthroscopy in the Era of Precision Medicine: A Comprehensive Review of Tailored Approaches and Emerging Technologies

Knee arthroscopy, a minimally invasive procedure, has transformed the treatment of knee pathologies by enabling direct visualization and management with minimal tissue disruption. Recent advances in precision medicine have introduced a new dimension to this field, allowing for highly individualized surgical approaches considering each patient's unique genetic, environmental, and biomechanical characteristics. This review explores the integration of precision medicine into knee arthroscopy, focusing on tailored approaches and emerging technologies. Key innovations such as robotic-assisted surgery, advanced imaging, and patient-specific instrumentation have enhanced surgical accuracy and patient outcomes, reduced recovery times, and minimized postoperative complications. The review also examines the role of biomarkers in guiding personalized treatment strategies, including ligament reconstructions, meniscal repairs, and cartilage restoration, which are now being refined to cater to the specific needs of individual patients. While the benefits of these innovations are clear, there are challenges to widespread adoption, including cost, resource allocation, and the need for further research to validate the efficacy of precision-driven approaches in knee arthroscopy. Moreover, the ethical considerations surrounding personalized medicine, such as patient privacy and genetic data usage, must also be addressed. Despite these barriers, the future of knee arthroscopy in the era of precision medicine holds great promise, with ongoing developments in artificial intelligence, genomics, and biomarker discovery poised to further refine patient-centered care. This comprehensive review provides valuable insights into how precision medicine reshapes knee arthroscopy, offering a glimpse into the future of more targeted and effective orthopedic interventions. By embracing these advancements, surgeons and healthcare providers can ensure optimal outcomes for patients undergoing knee arthroscopy.

Endogenous Tissue Engineering for Chondral and Osteochondral Regeneration: Strategies and Mechanisms

Increasing attention has been paid to the development of effective strategies for articular cartilage (AC) and osteochondral (OC) regeneration due to their limited self-reparative capacities and the shortage of timely and appropriate clinical treatments. Traditional cell-dependent tissue engineering faces various challenges such as restricted cell sources, phenotypic alterations, and immune rejection. In contrast, endogenous tissue engineering represents a promising alternative, leveraging acellular biomaterials to guide endogenous cells to the injury site and stimulate their intrinsic regenerative potential. This review provides a comprehensive overview of recent advancements in endogenous tissue engineering strategies for AC and OC regeneration, with a focus on the tissue engineering triad comprising endogenous stem/progenitor cells (ESPCs), scaffolds, and biomolecules. Multiple types of ESPCs present within the AC and OC microenvironment, including bone marrow-derived mesenchymal stem cells (BMSCs), adipose-derived mesenchymal stem cells (AD-MSCs), synovial membrane-derived mesenchymal stem cells (SM-MSCs), and AC-derived stem/progenitor cells (CSPCs), exhibit the ability to migrate toward injury sites and demonstrate pro-regenerative properties. The fabrication and characteristics of scaffolds in various formats including hydrogels, porous sponges, electrospun fibers, particles, films, multilayer scaffolds, bioceramics, and bioglass, highlighting their suitability for AC and OC repair, are systemically summarized. Furthermore, the review emphasizes the pivotal role of biomolecules in facilitating ESPCs migration, adhesion, chondrogenesis, osteogenesis, as well as regulating inflammation, aging, and hypertrophy-critical processes for endogenous AC and OC regeneration. Insights into the applications of endogenous tissue engineering strategies for in vivo AC and OC regeneration are provided along with a discussion on future perspectives to enhance regenerative outcomes.

The Current State of Meniscus Replacements

PURPOSE OF REVIEW

The field of meniscus replacement is changing continuously, with new devices emerging and others disappearing from the market. With the current tendency to preserve the knee joint, meniscus implants may become more relevant than ever. The purpose of this review is to provide an overview of the current state of partial and total meniscus replacements that have been developed beyond the academic phase. The available clinical and pre-clinical data is evaluated, and omissions are identified.

RECENT FINDINGS

Recent systematic reviews have shown a lack of homogenous clinical data on the CMI and Actifit meniscal scaffolds, especially regarding long-term performance without concomitant surgical interventions. Clinical studies on the medial total meniscus prostheses NUsurface and Artimis are ongoing, with the NUsurface being several years ahead. New techniques for meniscus replacement are rapidly developing, including the Artimis lateral meniscus prosthesis and the MeniscoFix 3D-printed scaffold. All evaluated clinical studies point towards improved clinical outcomes after implantation of partial and total meniscus replacements. Long-term data on survival and performance is of low quality for CMI and Actifit and is unavailable yet for NUsurface and Artimis. It is of major importance that future research focuses on optimizing fixation methods and identifying the optimal treatment strategy for each patient group. New techniques for total and partial replacement of the medial and lateral meniscus will be followed with interest.

Subchondral bone: An emerging target for the treatment of articular surface lesions of the knee

Purpose

When dealing with the health status of the knee articular surface, the entire osteochondral unit has gained increasing attention, and in particular the subchondral bone, which plays a key role in the integrity of the osteochondral unit. The aim of this article was to discuss the current evidence on the role of the subchondral bone.

Methods

Experts from different geographical regions were involved in performing a review on highly discussed topics about the subchondral bone, ranging from its etiopathogenetic role in joint degeneration processes to its prognostic role in chondral and osteochondral defects, up to treatment strategies to address both the subchondral bone and the articular surface.

Discussion

Subchondral bone has a central role both from an aetiologic point of view and as a diagnostic tool, and its status was found to be relevant also as a prognostic factor in the follow-up of chondral treatment. Finally, the recognition of its importance in the natural history of these lesions led to consider subchondral bone as a treatment target, with the development of osteochondral scaffolds and procedures to specifically address osteochondral lesions.

Conclusion

Subchondral bone plays a central role in articular surface lesions from different points of view. Several aspects still need to be understood, but a growing interest in subchondral bone is to be expected in the upcoming future towards the optimization of joint preservation strategies.

Level of Evidence

Level V, expert opinion.

Hydrogel-Based 3D Bioprinting Technology for Articular Cartilage Regenerative Engineering

Articular cartilage is an avascular tissue with very limited capacity of self-regeneration. Trauma or injury-related defects, inflammation, or aging in articular cartilage can induce progressive degenerative joint diseases such as osteoarthritis. There are significant clinical demands for the development of effective therapeutic approaches to promote articular cartilage repair or regeneration. The current treatment modalities used for the repair of cartilage lesions mainly include cell-based therapy, small molecules, surgical approaches, and tissue engineering. However, these approaches remain unsatisfactory. With the advent of three-dimensional (3D) bioprinting technology, tissue engineering provides an opportunity to repair articular cartilage defects or degeneration through the construction of organized, living structures composed of biomaterials, chondrogenic cells, and bioactive factors. The bioprinted cartilage-like structures can mimic native articular cartilage, as opposed to traditional approaches, by allowing excellent control of chondrogenic cell distribution and the modulation of biomechanical and biochemical properties with high precision. This review focuses on various hydrogels, including natural and synthetic hydrogels, and their current developments as bioinks in 3D bioprinting for cartilage tissue engineering. In addition, the challenges and prospects of these hydrogels in cartilage tissue engineering applications are also discussed.

Composite Zonal Scaffolds of Collagen I/II for Meniscus Regeneration

The meniscus is divided into three zones according to its vascularity: an external vascularized red-red zone mainly comprising collagen I, a red-white interphase zone mainly comprising collagens I and II, and an internal white-white zone rich in collagen II. Known scaffolds used to treat meniscal injuries do not reflect the chemical composition of the vascular areas of the meniscus. Therefore, in this study, four composite zonal scaffolds (named A, B, C, and D) were developed and characterized; the developed scaffolds exhibited the main chemical components of the external (collagen I), interphase (collagens I/II), and internal (collagen II) zones of the meniscus. Noncomposite scaffolds were also produced (named E), which had the same shape as the composite scaffolds but were entirely made of collagen I. The composite zonal scaffolds were prepared using different concentrations of collagen I and the same concentration of collagen II and were either cross-linked with genipin or not cross-linked. Porous, biodegradable, and hydrophilic scaffolds with an expected chemical composition were obtained. Their pore size was smaller than the size reported for the meniscus substitutes; however, all scaffolds allowed the adhesion and proliferation of human adipose-derived stem cells (hADSCs) and were not cytotoxic. Data from enzymatic degradation and hADSC proliferation assays were considered for choosing the cross-linked composite scaffolds along with the collagen I scaffold and to test if composite zonal scaffolds seeded with hADSC and cultured with differentiation medium produced fibrocartilage-like tissue different from that formed in noncomposite scaffolds. After 21 days of culture, hADSCs seeded on composite scaffolds afforded an extracellular matrix with aggrecan, whereas hADSCs seeded on noncomposite collagen I scaffolds formed a matrix-like fibrocartilage without aggrecan.

Collagen Meniscal Scaffold Implantation Can Provide Meniscal Regeneration in Asian Patients with Partial Meniscal Defects: A Prospective Randomized Controlled Study with Three-Dimensional Volume Analysis of the Meniscus

Background

To date, the efficiency of collagen meniscal scaffold implantation in Asian patients with partial meniscal defects has not been evaluated. In addition, no study has quantitatively analyzed meniscal regeneration using three-dimensional (3D) volume analysis after collagen scaffold implantation. We aimed to compare meniscal regeneration using 3D volume analysis between Asian patients undergoing collagen-based meniscal scaffold implantation after partial meniscectomy and those undergoing only partial meniscectomy.

Methods

Nineteen patients who underwent collagen-based meniscal scaffold implantation and 14 who underwent partial meniscectomy were analyzed with a prospective randomized control design for 12 months postoperatively. The demographic characteristics, Kellgren-Lawrence grade, and location of the injury lesion (medial or lateral meniscus) were not significantly different between the groups. Using 3D volume analysis with magnetic resonance imaging (MRI), the meniscus-removing ratio during the operative procedure and the meniscus defect-filling ratio were measured during the 12-month postoperative period. Clinically, the visual analog scale, International Knee Documentation Committee score, and Knee Injury and Osteoarthritis Outcome Score were evaluated. The Whole-Organ Magnetic Resonance Imaging Score (WORMS) and Genovese grade were also evaluated using MRI.

Results

In the 3D volume analysis, the average meniscus-removing ratio during surgery was not significantly different between the groups (-9.3% vs. -9.2%, p = 0.984). The average meniscus defect-filling ratio during the postoperative 12-month period was 7.5% in the scaffold group and -0.4% in the meniscectomy group (p < 0.001). None of the clinical results were significantly different between the scaffold and meniscectomy groups at 12 months postoperatively. The average change in the total WORMS score was not significantly different between the groups (0 vs. 1.9, p = 0.399). The Genovese grade of the implanted collagen scaffold did not significantly change during the follow-up period in terms of morphology and size (p = 0.063); however, the grade significantly improved in terms of signal intensity (p = 0.001).

Conclusions

Definite meniscal regeneration and stable scaffold incorporation were observed after collagen-based meniscal scaffold implantation in Asian patients during 12 months of follow-up. A long-term follow-up study with a larger cohort is required to determine the advantages of collagenous meniscal scaffold implantation in Asian patients.

The reimbursement system can influence the treatment choice and favor joint replacement versus other less invasive solutions in patients affected by osteoarthritis

PURPOSE

The aim of this study was to assess how physicians perceive the role of the reimbursement system and its potential influence in affecting their treatment choice in the management of patients affected by osteoarthritis (OA).

METHODS

A survey was administered to 283 members of SIAGASCOT (Italian Society of Arthroscopy, Knee, Upper Limb, Sport, Cartilage and Orthopaedic Technologies), a National scientific orthopaedic society. The survey presented multiple choice questions on the access allowed by the current Diagnosis-Related Groups (DRG) system to all necessary options to treat patients affected by OA and on the influence toward prosthetic solutions versus other less invasive options.

RESULTS

Almost 70% of the participants consider that the current DRG system does not allow access to all necessary options to best treat patients affected by OA. More than half of the participants thought that the current DRG system favors the choice of prosthetic solutions (55%) and that it can contribute to the increase in prosthetic implantation at the expense of less invasive solutions (54%). The sub-analyses based on different age groups, professional roles, and places of work allowed to evaluate the response in each specific category, confirming the findings for all investigated aspects.

CONCLUSIONS

This survey documented that the majority of physicians consider that the reimbursement system can influence the treatment choice when managing OA patients. The current DRG system was perceived as unbalanced in favor of the choice of the prosthetic solution, which could contribute to the increase in prosthetic implantation at the expense of other less invasive options for OA management.

Design and Finite Element Analysis of Artificial Braided Meniscus Model

Currently, artificial meniscus prostheses are mostly homogenous, low strength, and difficult to mimic the distribution of internal fibers in the native meniscus. To promote the overall mechanical performance of meniscus prostheses, this paper designed a new artificial braided meniscus model and conducted finite element analysis. Firstly, we designed the spatial fiber interweaving structure of meniscus model to mimic the internal fiber distribution of the native meniscus. Secondly, we provided the detailed braiding steps and forming process principles based on the weaving structure. Thirdly, we adopted the models of the fiber-embedded matrix and multi-scale methods separately for finite element analysis to achieve the reliable elastic properties. Meanwhile, we compared the results for two models, which are basically consistent, and verified the accuracy of analysis. Finally, we conducted the comparative simulation analysis of the meniscus model and the pure matrix meniscus model based on the solved elastic constants through Abaqus, which indicated a 60% increase in strength.

The first-generation anatomical medial meniscus prosthesis led to unsatisfactory results: a first-in-human study

PURPOSE

The purpose of this first-in-human study was to evaluate the effect of a polycarbonate anatomical meniscus prosthesis system, including the surgical procedure, on knee pain and describe potential adverse events in patients with post-meniscectomy pain syndrome.

METHODS

Eleven patients with post-meniscectomy pain syndrome and limited underlying cartilage damage were enrolled in the study. Five received a medial polycarbonate urethane meniscus prosthesis which was clicked onto 2 titanium screws fixated at the native horn attachments on the tibia. The KOOS score was planned to be collected at baseline and at 3, 6, 12 and 24 months following the intervention including radiographs at 6, 12 and 24 months. MRI scans were repeated after 12 and 24 months.

RESULTS

The surgical technique to select an appropriately sized implant and correct positioning of the fixation screws and meniscus prosthesis onto the tibia was demonstrated to be feasible and reproducible. Inclusion stopped after 5 patients because of serious adverse device-related events. All patients reported knee joint stiffness and slight effusion in their knee at 6 months follow-up. In 3 patients the implant was removed because of implant failure and in 1 patient the implant was removed because of persistent pain and extension limitation. In none of the patients did the KOOS score improve in the first 6 months after surgery. However, in the patient who still has the implant in situ, PROMs started to improve 1 year after surgery and this improvement continued through 2 years of follow-up. The KOOS Pain, symptoms and ADL were close to the maximal 100 points. KOOS QoL and sport did improve but remained suboptimal.

CONCLUSION

This first version of the meniscus prosthesis led to impaired knee function and failed in four out of five patients. The patients where the prosthesis was removed were salvable and the PROMs returned to pre-study levels. The results in the patient where the device is still in place are promising.

LEVEL OF EVIDENCE

Level II.

Loofah-chitosan and poly (-3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) based hydrogel scaffolds for meniscus tissue engineering applications

The meniscus is a fibrocartilaginous tissue that is very important for the stability of the knee joint. However, it has a low ability to heal itself, so damage to it will always lead to articular cartilage degeneration. The goal of this study was to make a new type of meniscus scaffold made of chitosan, loofah mat, and PHBV nanofibers, as well as to describe hydrogel composite scaffolds in terms of their shape, chemical composition, mechanical properties, and temperature. Three different concentrations of genipin (0.1, 0.3, and 0.5 %) were used and the optimal crosslinker concentration was 0.3 % for Chitosan/loofah (CL) and Chitosan/loofah/PHBV fiber (CLF). Scaffolds were seeded using undifferentiated MSCs and incubated for 21 days to investigate the chondrogenic potential of hydrogel scaffolds. Cell proliferation analyses were performed using WST-1 assay, GAG content was analyzed, SEM and fluorescence imaging observed morphologies and cell attachment, and histological and immunohistochemical studies were performed. The in vitro analysis showed no cytotoxic effect and enabled cells to attach, proliferate, and migrate inside the scaffold. In conclusion, the hydrogel composite scaffold is a promising material for engineering meniscus tissue.

Mechanical performance of additively manufactured cobalt-chromium-molybdenum auxetic meta-biomaterial bone scaffolds

Auxetic meta-biomaterials offer unconventional strain behaviour owing to their negative Poisson's ratio (-υ) leading to deformation modes and mechanical properties different to traditional cellular biomaterials. This can lead to favourable outcomes for load-bearing tissue engineering constructs such as bone scaffolds. Emerging early-stage studies have shown the potential of auxetic architecture in increasing cell proliferation and tissue reintegration owing to their -υ. However, research on the development of CoCrMo auxetic meta-biomaterials including bone scaffolds or implants is yet to be reported. In this regard, this paper proposes a potential framework for the development of auxetic meta-biomaterials that can be printed on demand while featuring porosity requirements suitable for load-bearing bone scaffolds. Overall, the performance of five CoCrMo auxetic meta-biomaterial scaffolds characterised under two scenarios for their potential to offer near-zero and high negative Poisson's ratio is demonstrated. Ashby's criterion followed by prototype testing was employed to evaluate the mechanical performance and failure modes of the auxetic meta-biomaterial scaffolds under uniaxial compression. The best performing scaffold architectures are identified through a multi-criteria decision-making procedure combining 'analytic hierarchy process' (AHP) and 'technique for order of preference by similarity to ideal solution' (TOPSIS). The results found the Poisson's ratio for the meta-biomaterial architectures to be in the range of -0.1 to -0.24 at a porosity range of 73-82%. It was found that the meta-biomaterial scaffold (AX1) that offered the highest auxeticity also showed the highest elastic modulus, yield, and ultimate strength of 1.66 GPa, 56 MPa and 158 MPa, respectively. The study demonstrates that the elastic modulus, yield stress, and Poisson's ratio of auxetic meta-biomaterials are primarily influenced by the underlying meta-cellular architecture followed by relative density offering a secondary influence.

Recent strategies of collagen-based biomaterials for cartilage repair: from structure cognition to function endowment

Collagen, characteristic in biomimetic composition and hierarchical structure, boasts a huge potential in repairing cartilage defect due to its extraordinary bioactivities and regulated physicochemical properties, such as low immunogenicity, biocompatibility and controllable degradation, which promotes the cell adhesion, migration and proliferation. Therefore, collagen-based biomaterial has been explored as porous scaffolds or functional coatings in cell-free scaffold and tissue engineering strategy for cartilage repairing. Among those forming technologies, freeze-dry is frequently used with special modifications while 3D-printing and electrospinning serve as the structure-controller in a more precise way. Besides, appropriate cross-linking treatment and incorporation with bioactive substance generally help the collagen-based biomaterials to meet the physicochemical requirement in the defect site and strengthen the repairing performance. Furthermore, comprehensive evaluations on the repair effects of biomaterials are sorted out in terms of in vitro, in vivo and clinical assessments, focusing on the morphology observation, characteristic production and critical gene expression. Finally, the challenge of biomaterial-based therapy for cartilage defect repairing was summarized, which is, the adaption to the highly complex structure and functional difference of cartilage.

Graphical abstract