Meniscal Implants Research Articles

The Potential of Tendon Autograft as Meniscus substitution: Current concepts

Meniscectomy is known to alter the mechanics, stability, and kinematics of the tibiofemoral joint, leading to early knee osteoarthritis (KOA). While several meniscal substitutions exist, such as meniscus allograft transplantation, collagen meniscus implants, and artificial substitutes, they often come with technical challenges, high costs, and risks, including allograft failure, infections, and disease transmission. Tendon autografts emerge as a promising option, offering safety, availability, biocompatibility, and a reduced risk of pathophoresis.This review delves into basic, in vivo, in vitro, and biomechanical studies alongside clinical outcomes and future prospects of tendon autografts as meniscus substitutes. A thorough understanding of this option is vital for integrating these evolving techniques into clinical practice and mitigating early KOA progression.

Surgical Therapy and Tissue Engineering for Meniscal Repair.

Meniscal damage is one of the prevalent causes of knee pain, swelling, instability, and functional compromise, frequently culminating in osteoarthritis (OA). Timely and appropriate interventions are crucial to relieve symptoms and prevent or delay the onset of OA. Contemporary surgical treatments include total or partial meniscectomy, meniscal repair, allograft meniscal transplantation, and synthetic meniscal implants, but each presents its specific limitations. Recently, regenerative medicine and tissue engineering have emerged as promising fields, offering innovative prospects for meniscal regeneration and repair. This review delineates current surgical methods, elucidating their specific indications, advantages, and disadvantages. Concurrently, it delves into state-of-the-art tissue engineering techniques aimed at the functional regenerative repair of meniscus. Recommendations for future research and clinical practice are also provided.

Biologic Augmentation of Isolated Meniscal Repair.

The limited blood supply and intrinsic healing capacity of the meniscus contributes to suboptimal tissue regeneration following injury and surgical repair. Biologic augmentation techniques have been utilized in combination with isolated meniscal repair to improve tissue regeneration. Several innovative strategies such as Platelet-Rich Plasma (PRP), fibrin clots, mesenchymal stem cells (MSCs), bone marrow stimulation, meniscal scaffolds, and meniscal wrapping, are being explored to enhance repair outcomes. This article provides a comprehensive review of recent findings and conclusions regarding biologic augmentation techniques. Studies on PRP reveal mixed outcomes, with some suggesting benefits in reducing failure rates of isolated meniscal repair, while others question its efficacy. Fibrin clots and PRF (Platelet-rich fibrin), although promising, show inconsistent results and lack sufficient evidence for definitive conclusions. MSCs demonstrate potential in preclinical studies, but clinical trials have been limited and inconclusive. Bone marrow stimulation appears effective in certain contexts, but its broader applicability remains uncertain. Meniscal scaffolds, including CMI (Collagen Meniscal Implants) and Actifit (polyurethane scaffolds), show encouraging short- and mid-term outcomes but have not consistently surpassed traditional methods in the long term. Meniscal wrapping is infrequently studied but demonstrates positive short-term results with certain applications. The review reveals a diverse range of outcomes for biologic augmentation in meniscal repair. While certain techniques show promise, particularly in specific scenarios, the overall efficacy of these methods has yet to reach a consensus. The review underscores the necessity for standardized, high-quality research to establish the definitive effectiveness of these biologic augmentation methods.

Evaluation of Porous (Poly(lactide-co-glycolide)-co-(ε-caprolactone)) Polyurethane for Use in Orthopedic Scaffolds.

To develop an orthopedic scaffold that could overcome the limitations of implants used in clinics, we designed poly(ester-urethane) foams and compared their properties with those of a commercial gold standard. A degradable poly(ester-urethane) was synthetized by polyaddition between a diisocyanate poly(ε-caprolactone) prepolymer (PCL di-NCO, Mn = 2400 g·mol-1) and poly(lactic-co-glycolic acid) diol (PLGA, Mn = 2200 g·mol-1) acting as a chain extender. The resulting high-molecular-weight poly(ester-urethane) (PEU, Mn = 87,000 g·mol-1) was obtained and thoroughly characterized by NMR, FTIR and SEC-MALS. The porous scaffolds were then processed using the solvent casting (SC)/particle leaching (PL) method with different NaCl crystal concentrations. The morphology, pore size and porosity of the foams were evaluated using SEM, showing interconnected pores with a uniform size of around 150 µm. The mechanical properties of the scaffolds are close to those of the human meniscus (Ey = 0.5~1 MPa). Their degradation under accelerated conditions confirms that incorporating PLGA into the scaffolds greatly accelerates their degradation rate compared to the gold-standard implant. Finally, a cytotoxicity study confirmed the absence of the cytotoxicity of the PEU, with a 90% viability of the L929 cells. These results suggest that degradable porous PLGA/PCL poly(ester-urethane) has potential in the development of meniscal implants.

Photocrosslinkable silk-based bioinks embedded with growth factor loaded microspheres towards cell-free 3D printing approach for biomimetic regeneration of meniscal tissue

Fibrocartilaginous meniscal tear regeneration is a major challenge due to the large avascular regions which suffer several injuries among all age-groups. Mostly, meniscus implants are focused on the development of multi-layered meniscus constructs and scaffolds that mimic the macro-architecture, functionality and mechanical strength. The native human menisci consist of vascular and avascular regions that contain different cellular phenotypes and are hence composed of a gradient of extracellular matrix (ECM) components. The biochemical composition of the inner, middle and outer regions of the knee menisci plays a significant role in the mechanical behavior and its overall functionality. We have developed a photo-polymerizing mulberry and non-mulberry silk-based biomaterial ink which is laden with growth factor loaded gelMA microspheres for the zone-specific regeneration of full thickness meniscus tears using three-dimensional (3D) fabrication. We have fabricated growth factor loaded gelMA microspheres and encapsulated them within the biomaterial ink for controlled release of Connective Tissue Growth Factor (CTGF) and Transforming Growth Factor-beta3 (TGF-β3) from the different zones of the meniscus constructs. The growth factor releasing constructs demonstrate the requisite mechanical resilience, degradability and release behaviour for regeneration of meniscal tissue. The developed growth factor loaded constructs demonstrate zone specific phenotypic differentiation of adipose derived stem cells and extracellular matrix deposition by the differentiated stem cells in vitro. The microsphere loaded constructs were found to be immuno-compatible as well. Therefore, these bioactive microsphere-laden 3D printed meniscus constructs would potentially promote regeneration and integration of meniscal tissue in vivo.

3D BIOPRINTING TISSUE-ENGINEERED MENISCAL CONSTRUCTS

Meniscal injuries affect over 1.5 million people across Europe and the USA annually. Injury greatly reduces knee joint mobility and quality of life and frequently leads to the development of osteoarthritis. Tissue engineered strategies have emerged in response to a lack of viable treatments for meniscal pathologies. However, to date, constructs mimicking the structural and functional organisation of native tissue, whilst promoting deposition of new extracellular matrix, remains a bottleneck in meniscal repair. 3D bioprinting allows for deposition and patterning of biological materials with high spatial resolution. This project aims to develop a biomimetic 3D bioprinted meniscal substitute.Meniscal tissue was characterised to effectively inform the design of biomaterials for bioprinting constructs with appropriate structural and functional properties. Histology, gene expression and mass spectrometry were performed on native tissue to investigate tissue architecture, matrix components, cell populations and protein expression regionally across the meniscus. 3D laser scanning and magnetic resonance imaging were employed to acquire the external geometrical information prior to fabrication of a 3D printed meniscus. Bioink suitability was investigated through regional meniscal cell encapsulation in blended hydrogels, with the incorporation of growth factors and assessed for their suitability through rheology, scanning electron microscopy, histology and gene expression analysis.Meniscal tissue characterisation revealed regional variations in matrix compositions, cellular populations and protein expression. The process of imaging through to 3D printing highlighted the capability of producing a construct that accurately replicated meniscal geometries. Regional meniscal cell encapsulation into hydrogels revealed a recovery in cell phenotype, with the incorporation of growth factors into the bioink's stimulating cellular re-differentiation and improved zonal functionality.Meniscus biofabrication highlights the potential to print patient specific, customisable meniscal implants. Achieving zonally distinct variations in cell and matrix deposition highlights the ability to fabricate a highly complex tissue engineered construct.Acknowledgements: This work was undertaken as part of the UK Research and Innovation (UKRI)-funded CDT in Advanced Biomedical Materials.

Evaluation of Remodeling and Extrusion of Polyurethane Meniscal Implants after Meniscus Reconstruction using Ultrasonography.

Meniscal tears are among the most common indications for knee arthroscopy. Artificial polyurethane scaffolds have demonstrated efficacy in reducing pain and promoting the growth of normal meniscal tissue, with high absorption rates facilitating full tissue regeneration. This study aimed to evaluate the remodeling of polyurethane meniscal implants post-reconstruction using ultrasonography. This imaging technique not only assesses changes in implant properties, such as echogenicity, but also the shape changes during functional examination. The assessment of meniscal extrusion, comparing size at rest and under weight-bearing, is an indirect parameter that provides insight into the physical properties of the remodeling implant, with greater extrusion indicating reduced stiffness and inferior physical properties of the meniscus. Ultrasonography has the valuable advantage of allowing for assessment of the blood supply to the meniscus through Power Doppler imaging. The presence of vessels within the meniscal implants serves as evidence of ongoing remodeling. The study included 35 patients (13 female, 22 male; mean age 41.6 years, range 18-66) who underwent arthroscopic meniscal reconstruction with polyurethane implants, with an average time from surgery of 2.8 years (range 0.3-4.5 years). Results showed complete (29.7%), significant (45.9%), or moderate (16.2%) remodeling into natural meniscal tissue in 91.8% of the implants. The mean values of extrusion in the supine position and during 90-degree flexion were significantly greater in the operated limb (2.603) compared to the contralateral limb (1.978; t(35) = 2.442; P < 0.05). No significant differences in extrusion were found between the limbs in a standing position, indicating favorable physical properties of the polyurethane meniscal implants. Further ultrasonography studies of meniscal scaffolds are deemed relevant.

Could a three-dimensional contralateral meniscus segmentation for allograft or scaffold sizing be possible? A prospective study.

Meniscal allografts and biodegradable meniscal implants are attractive surgical options for painful subtotal or total meniscectomies. In order to get the best results, these should be as similar as possible to the original meniscus in terms of shape, structure, and volume. Three-dimensional meniscus sizing could be an approach to improve the accuracy of meniscus matching. Therefore, the aims of this study were to perform a comparative morphological and volumetric analysis of the healthy meniscus based on manual tri-planar segmentation and to demonstrate that the menisci from the contralateral knee could be used as a reference in the sizing of a meniscal graft or a scaffold. Three-dimensional meniscal models were created based on 120 MRIs in 60 healthy subjects (bilateral knees). The differences between the pairs of menisci concerning the widths, thicknesses, lateromedial distances, anteroposterior distances, angles of coverage, and meniscal volumes were evaluated. T-Student tests were used to compare the quantitative numerical variables of the different groups. Pearson's linear regression was used to determine if correlations existed between demographic variables (age, gender, height, weight) and anatomical parameters. Statistical significance was set at p < 0.05. Comparing the 120 pairs of menisci of each subject, there was no statistically significant difference for all parameters studied for both the medial and lateral meniscus. When the measurements were stratified by gender, statistically significant differences were observed for all parameters except meniscal coverage angles. We observed that anteroposterior and lateromedial distances were positively correlated with height and body mass index both at the level of the medial meniscus (r = 0.68; r = 0.66; r = 0.65; and r = 0.63) and lateral (r = 0.68; r = 0.69; r = 0.61; and r = 0.60). Our study demonstrated that the intra-individual 3D shapes of the left and right menisci are very similar. Therefore, the contralateral side could be used as a template for the 3D sizing of meniscal allografts or meniscal implants.

Poster 242: Predictors of the Ten-Year Patient-Reported Outcome Measures After Collagen Meniscus Implant (CMI) for Partial Meniscus Deficiency

Objectives: Collagen Meniscus Implant (CMI) is considered an effective procedure for reducing knee pain and improving knee function after previous meniscectomy. Nevertheless, the current knowledge regarding the clinical results of CMI are limited to small case series at short- to mid-term follow-up studies. The goal of the present study was to evaluate clinical outcomes, reoperations, and failures of CMI at a minimum 10 years of follow-up. Methods: Consecutive patients who underwernt CMI at a single institution were screened for elegibility. Inclusion criteria for the present study were (1) Medial or Lateral CMI, (2) Isolated or combined procedure with ACL reconstruction, knee osteotomy or cartilage treatment, (3) follow-up between 10 and 15 years. Demographics and surgical details were obtained via chart review. Patients were asked if they were satisfied with the procedure and were evaluated with the Lysholm score, Knee injury and Osteoarthritis Outcome Score (KOOS), visual analog scale (VAS) for pain, and Tegner score at the final follow-up. Survival analysis was performed with Kaplan-Meier curve, and clinical scores were analyzed based on the Patient Acceptable Symptom State (PASS). Results: A total of 92 patients (mean age, 42.8 years) were included in the analysis. A significant improvement in all the clinical scores was reported between the preoperative evaluation and the last follow-up. A chondropaty with outerbridge grade ≥III was associated with significantly overall lower clinical score, while a timing from meniscectomy to CMI implant to ≥5 years determined more pain at rest and lower score in the KOOS quality of life. Overall, 25% of patients did not achieved the PASS for Lysholm score and a percentage variable from 19% (KOOS Pain) and 40% (KOOS Symptoms) did not achieved the PASS in the KOOS subscales. Chondropaty with outerbridge grade ≥III was associated with an higher Risk of not achieving the PASS in all the KOOS subscales, while an age at surgery ≥45 years was resulted in a lower risk of not achieving PASS in the pain subscale. At the last follow-up 63% of patients returned to sport practice after CMI implantation, with 41% at the same or higher level. Finally, 80% of the patients were satisfied with the procedure Conclusions: CMI provided satisfactory results in terms of function, symptoms, sports and quality of life in 60% to 80% of the patients after more than 10 years of follow-up with clinical scores still higher compared to the preoperative evaluation. The cartilage status and the time from meniscectomy have shown to impact negatively on the outcomes, while an age &gt;45 years was associated with less pain. [Table: see text][Table: see text]

Development of a bioreactor for in-vitro compression cycling of tissue engineered meniscal implants

Injuries to the meniscus are common and can impair physical activities. Bioprinted meniscal tissue offers an attractive alternative to donor tissue for meniscal repair but achieving the strength of native tissue is a challenge. Here we report the development of a tissue engineering bioreactor designed to apply repetitive force which may lead to an increase in the compressive modulus and durability of bioprinted meniscal tissues. The modular bioreactor system is composed of a sterilizable tissue culture vessel together with a dock that applies and measures mechanical force. The culture vessel allows for simultaneous compression cycling of two anatomically sized menisci. Using a hybrid linear actuator with a stepper motor, the dock can apply up to 300 N of force at speeds up to 20 mm/s, corresponding to the upper limits of anatomical force and motion in the knee. An interchangeable 22 N load cell was mated between the culture vessel and the dock to log changes in force. Both the culture vessel and dock are maintained in a standard cell culture incubator to provide heat and CO2, while the dock is powered and controlled externally using a step motor drive and customized software.

3D printing of mechanically functional meniscal tissue equivalents using high concentration extracellular matrix inks

Decellularized extracellular matrix (dECM) has emerged as a promising biomaterial in the fields of tissue engineering and regenerative medicine due to its ability to provide specific biochemical and biophysical cues supportive of the regeneration of diverse tissue types. Such biomaterials have also been used to produce tissue-specific inks and bioinks for 3D printing applications. However, a major limitation associated with the use of such dECM materials is their poor mechanical properties, which limits their use in load-bearing applications such as meniscus regeneration. In this study, native porcine menisci were solubilized and decellularized using different methods to produce highly concentrated dECM inks of differing biochemical content and printability. All dECM inks displayed shear thinning and thixotropic properties, with increased viscosity and improved printability observed at higher pH levels, enabling the 3D printing of anatomically defined meniscal implants. With additional crosslinking of the dECM inks following thermal gelation at pH 11, it was possible to fabricate highly elastic meniscal tissue equivalents with compressive mechanical properties similar to the native tissue. These improved mechanical properties at higher pH correlated with the development of a denser network of smaller diameter collagen fibers. These constructs also displayed repeatable loading and unloading curves when subjected to long-term cyclic compression tests. Moreover, the printing of dECM inks at the appropriate pH promoted a preferential alignment of the collagen fibers. Altogether, these findings demonstrate the potential of 3D printing of highly concentrated meniscus dECM inks to produce mechanically functional and biocompatible implants for meniscal tissue regeneration. This approach could be applied to a wide variety of different biological tissues, enabling the 3D printing of tissue mimics with diverse applications from tissue engineering to surgical planning.

Tribological behaviour of a synthetic synovial fluid and polyurethane in biomedical implants

The purpose of this research is to evaluate the lubrication properties of a synthetic synovial fluid in combination with biocompatible polyurethanes, versus materials commonly used in biomedical implants. This combination is found in endurance testing of meniscal implants made from polyurethane.Two different polyurethanes were used for friction measurements, applying a synthetic lubricant, containing a Ringer's solution, hyaluronic acid and bovine serum albumin. The results were compared with friction measurements, using a polyurethane sphere against bovine cartilage, lubricated with bovine synovial fluid. The influence of the lubricants was tested by comparing water, synthetic- and bovine synovial fluids with the various material combinations, found in existing knee implants. From the measurements it was shown that the friction pairs including metal surfaces did not show the common Stribeck behaviour, with respect to transitions from the boundary regime to full film lubrication, and friction remained relatively constant over the whole velocity range. Friction pairs including the polymer counter surfaces and the water lubricated contacts, showed the expected transitions from boundary to mixed lubrication. From this it was concluded that protein adsorption mainly defined the frictional behaviour when using metal surfaces, leading to a coefficient of friction (COF)≈0.2 using synthetic synovial fluid, and COF≈0.15 when using bovine synovial fluid. PEEK samples showed higher values in the boundary lubrication region, which decreased to values of COF≈0.1 at higher velocities. Polyethylene samples showed higher friction results, which was attributed to the surface roughness. From the observed friction results and wear tracks it was concluded that a synthetic synovial lubricant performs very well with all material combinations, when more attention is paid to the polyethylene surface finish.

3D printing a universal knee meniscus using a custom collagen ink

Tears of the meniscus are among the most commonly diagnosed knee injuries. Because most of the meniscus lacks the ability to self-heal due to its low vascularity, surgical intervention is needed in more than 85% of cases. Tissue-engineered meniscal implants may provide a treatment strategy that better supports healing and long-term health and mobility benefits. We used three-dimensional printing to develop a “universal” human meniscal tissue repair device that can be trimmed to match the corresponding area of damage debrided during the patient's surgical repair. Computer aided design software was used to design an adult meniscus of average shape based on published physical dimensions. To reproduce the natural fiber arrangement found in the meniscus, the tool path for 3D bioprinting was structured to use alternating layers of circumferential and radial extrusions. We also developed extrudable, shear thinning bioinks based on meniscus biochemical components, including collagen I methacrylate, collagen II, and chondroitin sulfate methacrylate. The combination of this tissue-specific bioink and the deposition pattern to build the meniscus are novel. Ink formulations were evaluated with rheology to assess the viscosity and post-gelling stiffness. Inks retained shape fidelity when thermally gelled after printing into a support bath, and the fabricated menisci maintained stable dimensions for up to 4 weeks post printing. Bioprinted menisci containing human mesenchymal stem cells were also dimensionally stable, and viable cells were present up to 4 weeks post printing. Increased glycosaminoglycan deposition was noted in the bioprinted meniscus over 21 days, and decorin and collagen type I gene expression increased. Compression testing demonstrated that Young's modulus approaches 100 kPa when molded as a solid object and 45 kPa when extruded into the meniscus shape. This 3D printed, anisotropic meniscus emulates the natural architecture and biochemical composition of the natural human meniscus and has potential to be developed into a device for use in treatment of meniscal injuries.

Meniscal restoration: scaffolds, transplantation, and implants

Preservation of the injured meniscus tissue is the ideal goal of surgical treatment. However, many meniscal tears are not repairable with the result a loss of varying degrees of meniscal tissue. Various techniques are available to replace either portions of lost meniscal tissue or the entire meniscus. These techniques include the use of scaffolds, meniscal allografts, and synthetic meniscal implants. This article reviews the techniques utilized to restore the deficient meniscus.

Segmental meniscal replacement

Meniscal damage results in higher peak stress on the articular cartilage and leads to cartilage degeneration and osteoarthritis. Thus, in recent years there has been an increasing tendency to “save the meniscus” and to repair meniscal defects. However, this is not always possible and restoring meniscal function using scaffolds fulfills this gap. This approach requires the physical presence of an artificial meniscus to allow successful migration and colonization with precursor cells and vessels that lead to the development of organized meniscal tissue. Two meniscal scaffolds are currently available; 1 composed of aliphatic polyurethane named Actifit (Orteq Sports Medicine, Ltd.), and one based on collagen type I fibers called Collagen Meniscus Implant (Stryker Kalamazoo). Both provide an effective and safe solution to treat symptomatic patients with segmental meniscus mid-substance defects. Indeed, recent studies have demonstrated their ability to significantly improve patient satisfaction and clinical evaluation in the mid- to long-term. As such, these approaches hold great promise as a meniscus preservation option to facilitate long-term knee health.

Treatment Protocol According to the Meniscal Tears: A Review the Literature for all Comparing Methods

Purpose: Menisci are fibrocartilage formations that have multiple functional roles in the knee joint. After the better understanding of their function and also the observations of the changes of the knee joint after their removal, such as osteoarthritic changes, instability and changes on the allocation of the weight, a solution of repairing the tear was a demand. Methods: In our effort to conclude in one treatment protocol according to the meniscal tears we reviewed the literature for all the review articles of comparing methods of several suturing techniques of the meniscal tears. Results and Conclusions: After reviewing all these articles someone could conclude that simple sutures, mostly horizontal but also vertical have more stability and they are a good and trustable solution for the suturing of a meniscal tears. They demand then very good technique and a lot of surgical time. These very important disadvantages try to solve the various meniscal implants, but with a lower stability so far.

Placement of a polyurethane implant is not associated with a chondroprotective effect: comparative study with cases of isolated medial meniscectomy with at least five years of follow-up.

Our main objective was to evaluate clinically and radiologically and compare patients who had undergone partial meniscectomy alone, with those who had received a partial meniscectomy in which a polyurethane implant was placed, with a minimum follow-up of 5years. We performed a prospective cohort study. Patients were randomly distributed into Group A if they only received meniscectomy or Group B if they received meniscectomy plus a meniscal implant (Actifit®). We performed preoperative, postoperative, and 5-year-follow-up functional and radiological evaluations (magnetic resonance imaging). Twelve patients (40%) were treated with meniscal implants (Group B); 18 (60%) were treated with a conventional meniscectomy (Group A). Tegner, Lysholm and KOOS scores were evaluated prior to surgery and at 5-year follow-up. Only the Lysholm score showed a significant difference between groups, with a score increase between the preoperative evaluation and the 5-year follow-up evaluation (p = 0.013). Preoperative and postoperative MRIs were both available in 19 cases (63.3%). Long-term follow-up MRIs were performed in 11 cases of group B. No significant differences were found in functional outcomes or MRI findings (WORMS cartilage score increase p = 0.360). Although total reabsorptions of the collagen meniscus implant were not statistically significant in younger patients, a tendency towards a higher reabsorption process was seen in older patients (p = 0.015). The placement of a polyurethane implant after a wide meniscectomy is not accompanied by a chondroprotective effect over time. There is no functional difference between implant placement and isolated meniscectomy. There is a discrepancy between good clinical results and radiologic appearance of these implants and their underlying cartilage. II, therapeutic study.

Risk Factors Affecting the Survival Rate of Collagen Meniscal Implant for Partial Meniscal Deficiency: An Analysis of 156 Consecutive Cases at a Mean 10 Years of Follow-up

Background: Collagen meniscal implant (CMI) is a biologic scaffold that can be used to replace meniscus host tissue after partial meniscectomy. The short-term results of this procedure have already been described; however, little is known about risk factors for failure. Purpose: To determine the factors that predict failure of meniscal scaffold implantation in a large series of patients treated at a single institution and to better define the indications for surgery. Study Design: Case-control study; Level of evidence, 3. Methods: The analysis included 186 consecutive patients with a minimum 5-year follow-up who underwent CMI scaffold implantation or combined procedures. Patients’ characteristics and details of the surgery were obtained via chart review. Patients with a Lysholm score <65 were considered to have experienced clinical failure. Surgical failure was defined as partial or total scaffold removal. Results: The final analysis included 156 patients (84%) at a mean follow-up of 10.9 ± 4.3 years. The patients’ mean age at surgery was 42.0 ± 11.1 years, and the survival rate was 87.8%. Subgroup analysis identified Outerbridge grade 3-4 (Hazard ratio [HR], 3.8; P = .004) and a lateral meniscal implant (HR, 3.2; P = .048) as risk factors for failure. The survival rate was 90.4% for medial implants and 77.4% for lateral implants. An Outerbridge grade 3-4 (HR, 2.8; P < .001) and time from meniscectomy to scaffold >10 years (HR, 2.8; P = .020) were predictive of surgical or clinical failure. Conclusion: CMI for partial meniscal deficiency provided good long-term results, with 87.8% of the implants still in situ at a mean 10.9 years of follow-up. Outerbridge grade 3-4, lateral meniscal implants, and longer time from the meniscectomy to implantation of the CMI were identified as risk factors for clinical and surgical failure.

Paper 31: Risk factors affecting the survival rate of Collagen Meniscus Implant (CMI) for partial meniscus deficiency. An analysis of 156 consecutive cases at a mean 10 years of follow-up

Objectives:The present study aimed to determine the factors that predict failure of meniscus scaffold implantation in a large series of patients treated at a single institution, to better refine the indications for surgery and better inform future patients.Methods:156 consecutive patients with a minimum 5-year follow-up who underwent isolate CMI scaffold implantation or combined procedures were included in the analysis. Demographic and surgical information were obtained via chart review. Patients with partial meniscal deficiency requiring CMI implant, who had an Outerbridge grade of at least 3 and also underwent an additional surgery were considered as “complex cases”. Patients were asked to complete the Lyshlom questionnaire and those with a “poor” Lysholm score (<65 points) were considered a clinical failure. Patients were also inquired regarding further reoperations on the ipsilateral knee during the follow-up period to determine the incidence of surgical failure, defined as partial or total scaffold removal.Results:156 patients (84%) with a mean age at surgery of 42.0 ± 11.1 were included in the final analysis at an average follow-up of 10.9 ± 4.3 years. The overall survival rate from surgical failure was 87.8%. When further evaluating the different subgroups of patients, an Outerbridge grade of III-IV (HR 3.8; P =.004) and lateral scaffold (HR, 3.2; P= .0048) were identified as risk factors In the specific, the overall survival rate of the medial scaffold was 90.4%, while the survival rate of the lateral one was 77.4%. Finally, 42 patients (26.9%) were considered either a surgical or clinical failure. In this case, risk factors identified were: an Outerbridge grade of III-IV (HR, 3.1; P =.000), and time from meniscectomy to scaffold greater than 10 years (HR, 2.7; P = .042).Conclusions:Collagen meniscus implant for partial meniscus deficiency provided good long-term results, with 87.8% of the implants still in-situ at a mean 10.9 years of follow-up. The cartilage status, laterality of the scaffold, and time from meniscectomy to CMI surgery were identified to affect significantly clinical and/or surgical failures.

Potential of Melt Electrowritten Scaffolds Seeded with Meniscus Cells and Mesenchymal Stromal Cells.

Meniscus injury and meniscectomy are strongly related to osteoarthritis, thus there is a clinical need for meniscus replacement. The purpose of this study is to create a meniscus scaffold with micro-scale circumferential and radial fibres suitable for a one-stage cell-based treatment. Poly-caprolactone-based scaffolds with three different architectures were made using melt electrowriting (MEW) technology and their in vitro performance was compared with scaffolds made using fused-deposition modelling (FDM) and with the clinically used Collagen Meniscus Implants® (CMI®). The scaffolds were seeded with meniscus and mesenchymal stromal cells (MSCs) in fibrin gel and cultured for 28 d. A basal level of proteoglycan production was demonstrated in MEW scaffolds, the CMI®, and fibrin gel control, yet within the FDM scaffolds less proteoglycan production was observed. Compressive properties were assessed under uniaxial confined compression after 1 and 28 d of culture. The MEW scaffolds showed a higher Young’s modulus when compared to the CMI® scaffolds and a higher yield point compared to FDM scaffolds. This study demonstrates the feasibility of creating a wedge-shaped meniscus scaffold with MEW using medical-grade materials and seeding the scaffold with a clinically-feasible cell number and -type for potential translation as a one-stage treatment.