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

PURPOSE: 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. METHODS: 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. RESULTS: 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). CONCLUSION: 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.

Integration of polyurethane meniscus scaffold during ACL revision is not reliable at 5 years despite favourable clinical outcome.

PURPOSE: The aim of this study was to evaluate the clinical outcome at 5-year follow-up of a one-step procedure combining anterior cruciate ligament (ACL) reconstruction and partial meniscus replacement using a polyurethane scaffold for the treatment of symptomatic patients with previously failed ACL reconstruction and partial medial meniscectomy. Moreover, the implanted scaffolds have been evaluated by MRI protocol in terms of morphology, volume, and signal intensity. METHODS: Twenty patients with symptomatic knee laxity after failed ACL reconstruction and partial medial meniscectomy underwent ACL revision combined with polyurethane-based meniscal scaffold implant. Clinical assessment at 2- and 5-year follow-ups included VAS, Tegner Activity Score, International Knee Documentation Committee (IKDC), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and the Lysholm Score. MRI evaluation of the scaffold was performed according to the Genovese scale with quantification of the scaffold's volume at 1- and 5-year follow-ups. RESULTS: All scores revealed clinical improvement as compared with the preoperative values at the 2- and 5-year follow-ups. However, a slight, but significant reduction of scores was observed between 2 and 5 years. Concerning the MRI assessment, a significant reduction of the scaffold's volume was observed between 1 and 5 years. Genovese Morphology classification at 5 years included two complete resorptions (Type 3) and all the remaining patients had irregular morphology (Type 2). With regard to the Genovese Signal at the 5-year follow-up, three were classified as markedly hyperintense (Type 1), 15 as slightly hyperintense (Type 2), and two as isointense (Type 1). CONCLUSION: Simultaneous ACL reconstruction and partial meniscus replacement using a polyurethane scaffold provides favourable clinical outcomes in the treatment of symptomatic patients with previously failed ACL reconstruction and partial medial meniscectomy at 5 years. However, MRI evaluation suggests that integration of the scaffold is not consistent. LEVEL OF EVIDENCE: Level IV.

Satisfactory clinical results and low failure rate of medial collagen meniscus implant (CMI) at a minimum 20 years of follow-up.

PURPOSE: The aim of the study was to evaluate the long-term clinical results, reoperations, surgical failure and complications at a minimum of 20 year of follow-up of the first 8 medial CMI scaffolds implanted by a single surgeon during a pilot European Prospective study. METHODS: Seven (88%) out of 8 patients were contacted. The Cincinnati Score, VAS, and Lysholm score were collected. Moreover, magnetic resonance imaging (MRI) was performed on 4 patients at the last follow-up. Complications, reoperations and failures were also investigated. RESULTS: The average follow-up was 21.5 ± 0.5 years. One patient underwent TKA after 13 years from CMI implantation; a second patient underwent valgus high tibial osteotomy 8 years after the index surgery and another patient underwent anterior cruciate ligament hardware removal at 21 years of follow-up. At the final follow-up, 3 patients were rated as "Excellent", 1 as "Good" and 2 as "Fair" according to the Lysholm score. The Cincinnati score and the VAS were substantially stable over time. The MRI showed a mild osteoarthritis progression in 3 out of 4 patients according to the Yulish score, and the CMI signal was similar to the mid-term follow-up revealing 3 cases of myxoid degeneration and 1 case of normal signal with reduced scaffold size. CONCLUSION: The medial CMI is a safe procedure: satisfactory clinical results and a low failure rate could be expected even at a long-term follow-up. For this purpose, the correct indication as well as correcting axial malalignment and addressing knee instability at the time of the index surgery is mandatory. On the other hand, a mild osteoarthritis progression could be expected even after meniscus replacement. LEVEL OF EVIDENCE: IV.

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.

Silk Fibroin/Wool Keratin Composite Scaffold with Hierarchical Fibrous and Porous Structure.

The present study describes a silk microfiber reinforced meniscus scaffold (SMRMS) with hierarchical fibrous and porous structure made from silk fibroin (SF) and wool keratin (WK) using electrospinning and freeze-drying technology. This study focuses on the morphology, secondary structure, mechanical properties, and water absorption properties of the scaffold. The cytotoxicity and biocompatibility of SMRMS are assessed in vivo and in vitro. The scaffold shows hierarchical fibrous and porous structure, hierarchical pore size distribution (ranges from 50 to 650 µm), robust mechanical properties (compression strength can reach at 2.8 MPa), and stable biodegradability. A positive growth condition revealed by in vitro cytotoxicity testing indicates that the scaffold is not hazardous to cells. In vivo assessments of biocompatibility reveal that only a mild inflammatory reaction is present in implanted rat tissue. Meniscal scaffold made of SF/WK composite shows a potential application prospect in the meniscal repair engineering field with its development.

Cell-free 3D wet-electrospun PCL/silk fibroin/Sr2+ scaffold promotes successful total meniscus regeneration in a rabbit model.

Considering the intrinsic poor self-healing capacity of meniscus, tissue engineering has become a new direction for the treatment of meniscus lesions. However, disturbed by mechanical stability and biocompatibility, most meniscus implants fail to relieve symptoms and prevent the development of osteoarthritis. The goal of this study was to develop a potential meniscal substitute for clinical application. Here, silk fibroin with good mechanical performance and biocompatibility, and strontium ion acting as bioactive factor, were incorporated with Ɛ-Polycaprolactone to fabricate a meniscus scaffold (SP-Sr). By the wet-electrospun method, the 3D SP-Sr provided suitable pore size (100-200 µm) and enough mechanical support (61.6 ± 2.9 MPa for tensile modulus and 0.11 ± 0.03 MPa for compressive modulus). Moreover, after addition of Sr2+, the SP-Sr seeded by rabbit adipose tissue-derived stromal cells (rADSCs) showed the highest secretion with 2.61- and 2.98-fold increase in collagen and aggrecan, respectively, compared with SF/PCL group. And the extracellular matrix related genes expression in SP-Sr also showed upregulation results. Particularly, the expression of the collagen II gene, which played a crucial role in the formation of meniscal inner avascular region, showed a 9-fold increase in SP-Sr compared with pure PCL group. Furthermore, the MRI results of SP-Sr implanted in rabbits with total meniscectomy for 6 months demonstrated effective prevention of meniscus extrusion and relieving joint space narrowing compared with meniscectomy group. And the effects of cartilage protection and delaying osteoarthritis development were confirmed by Pathological examination. Especially, after 6-month implantation, the neo-menisci showed similar structural constituent and mechanical performance. STATEMENT OF SIGNIFICANCE: Meniscus regeneration faces great challenge due to the meniscus having limited healing potential owing to its anisotropic structure, its hypocellularity and hypovascularity. The present tissue engineering solutions have failed to maintain the biological function for meniscus reconstruction in vivo because of fragile and poor biocompatible materials, leading to long-term joint degeneration. The goal of this study was to develop a meniscal substitute potential for clinical application. Here, silk fibroin and strontium were incorporated with Ɛ-Polycaprolactone by wet-electrospinning method to fabricate a meniscus scaffold (SP-Sr). The 6-month implantation results revealed that SP-Sr scaffold was effective in preventing meniscus extrusion, cartilage protection and delaying osteoarthritis development, and the regenerated menisci showed similar structural constituent and mechanical performance.

Novel multilayer meniscal scaffold provides biomechanical and histological results comparable to polyurethane scaffolds: An 8 week rabbit study.

OBJECTIVE: The aim of this study was to evaluate the meniscal regeneration and arthritic changes after partial meniscectomy and application of either polyurethane scaffold or novel multilayer meniscal scaffold in a rabbit model. METHODS: Sixteen NewZealand rabbits were randomly divided into three groups. A reproducible 1.5-mm cylindrical defect was created in the avascular zone of the anterior horn of the medial meniscus bilaterally. Defects were filled with the polyurethane scaffold in Group 1 (n:6) and with novel multilayer scaffold in Group 2 (n:6). Rabbits in Group 3 (n:4) did not receive any treatment and defects were left empty. All animals were sacrificed after 8 weeks and bilateral knee joints were taken for macroscopic, biomechanical, and histological analysis. After excision of menisci, inked condylar surfaces and tibial plateaus were evaluated for arthritic changes. Digital photographs of excised menisci were also obtained and surface areas were measured by a computer software. Indentation testing of the tibial condyles and compression tests for the relevant meniscal areas was also performed in all groups. Histological analysis was made and all specimens were scored according to Rodeo scoring system. RESULTS: No signs of inflammation or infection were observed in any animals. A significant difference was observed between meniscus surface areas of the multilayer scaffold group (20.13 ± 1.91 mm2) and the group with empty meniscus defects (15.62 ± 2.04 mm2) (p = 0.047). The results of biomechanical compression tests revealed a significant difference between the Hayes scores of the second group (1.728) and the empty defect group (0,467) (p = 0.029). Intact meniscal tissue showed higher mechanical properties than all the defected samples. Multilayer scaffold group demonstrated the closest results compared to healthy meniscus tissue. Tibia indentation tests and histological evaluation showed no significant differences between groups (p = 0.401 and p = 0.186 respectively). CONCLUSIONS: In this study, the initial evaluation of novel multilayer meniscal scaffold prevented the shrinkage that may occur in the meniscus area and demonstrated superior biomechanical results compared to empty defects. No adverse events related to scaffold material was observed. Besides, promising biomechanical and histological results, comparable to polyurethane scaffold, were obtained.

Actifit® polyurethane meniscal scaffold: MRI and functional outcomes after a minimum follow-up of 5 years.

BACKGROUND: Implantation of the Actifit® polyurethane meniscal scaffold in patients who have pain after partial meniscectomy provides short-term pain relief and better function. But there is a lack of information about medium-term outcomes. The objective of this longitudinal study was to evaluate the MRI and functional outcomes after a minimum follow-up of 5 years. It was hypothesized that the results are stable over time. MATERIAL AND METHODS: Fifteen consecutive patients (8 men, 7 women; mean age 30 years, range 19-47, mean BMI 25) were enrolled in the study between February 2008 and January 2011. Five patients also underwent ACL reconstruction and one underwent mosaicplasty. Nine lateral and six medial Actifit® implants were evaluated prospectively before the surgery and at a minimum of 12, 24 and 60 months' follow-up using a visual analogue scale (VAS) for pain, the objective and subjective IKDC scores, radiological and MRI analysis with measurement of the ICRS score, Genovese score and extrusion. RESULTS: The mean follow-up was 6 years (range 5-8.1). Two patients were lost to follow-up. Three patients were re-operated at 7, 19 and 30 months because they had not improved functionally and the implant appeared damaged on MRI. Partial removal of the implant did not improve the functional outcomes (mean subjective IKDC pre- and post-revision: 37.0 vs. 34.9). Two patients were lost to follow-up. In intention to treat (13 cases), the pain (VAS) and subjective IKDC score were improved between the preoperative period and the last follow-up (5.46 vs. 2.92, P=0.007 and 51.2 vs. 66.1, P=0.05). In per protocol (10 cases, failures excluded), the pain (VAS) and subjective IKDC score were improved (5.3 vs. 1.9, P=0.0009; 49.6 vs. 75.4, P=0.002) along with the pain, daily activities and quality of life components of the KOOS (60.6 vs. 86.0, P=0.0008; 70.3 vs. 90.2, P=0.001; 42.7 vs. 71.0, P=0.0058). The functional scores were stable between months 12, 24 and 60. ICRS cartilage score and mean meniscal extrusion were unchanged at the last follow-up (1.6 vs. 1.6 and 2.41 vs. 2.79). In all patients, the meniscal implant had an intermediate signal and reduced size on MRI. DISCUSSION: Despite an abnormal MRI appearance suggesting the meniscal scaffold is not fully mature after 5 years, the functional scores and cartilage status are stable at this time point. However, the failure rate is still high and removing the implant in patients with poor function does not improve the outcome. TYPE OF STUDY: Prospective cohort study Level IV.

Establishment of novel meniscal scaffold structures using polyglycolic and poly-l-lactic acids.

The purpose of this study was to evaluate various types of meniscus scaffolds that mimic the meniscus structure, and to establish a novel cell-free meniscus scaffold with polyglycolic acid or poly-l-lactic acid. Four types of scaffolds were implanted into Japanese white rabbits: poly-l-lactic acid sponge poly-l-lactic acid, PGA-coated PLLA sponge, PGA lamination, and film-coated PGA lamination. Samples were harvested at 8 and 12 weeks after implantation, and a compression stress test was performed. The meniscus size and Ishida scores were evaluated for regenerated tissue. Immunohistochemistry was analyzed by anti-type I, II and X collagen antibodies to investigate the structure of the regenerated tissue, and by anti-iNOS antibody to investigate the inflammatory tissue of the meniscus. The cell nuclei of lymphocytes and foreign body multinucleated giant cells were counted in hematoxylin and eosin staining. Modified Mankin scores for cartilage degeneration were used for assessment after Safranin-O/Fast Green staining. The biomechanical test showed that l- and film-coated PGA lamination exhibited greater strength than s- and PGA-coated PLLA sponge. At 12 weeks, the size of meniscus and the Ishida score in implanted film-coated PGA lamination were improved significantly compared with the defect groups. The type II collagen staining intensity in the PGA lamination lamination is significantly higher than the defect at eight weeks. The staining intensity of iNOS and number of lymphocytes significantly increased in sponge poly-l-lactic acid at eight weeks, and increased in p-PLLA at 12 weeks. Foreign body multinucleated giant cells in implantation groups appeared, especially at eight weeks. The Mankin score for film-coated PGA lamination was significantly lower than for the defect at 12 weeks. Novel meniscal scaffolds especially PGA should possess not only biological but also biomechanical functions. In conclusions, film-coated PGA lamination was the beneficial property for meniscus scaffold from the points of better biomechanical function, good regeneration, and less inflammation with chondroprotective effects.

Actifit® scaffold implantation: Influence of preoperative meniscal extrusion on morphological and clinical outcomes.

BACKGROUND: Meniscal substitutes have been suggested for the treatment of knee pain after partial meniscectomy. However, despite the partial nature of the initial meniscectomy, secondary extrusion of the substitute is common. The primary objective of this study was to evaluate morphological outcomes of meniscal substitute implantation and their potential associations with preoperative meniscal extrusion. HYPOTHESIS: Preoperative absolute meniscal extrusion in the coronal plane predicts poorer morphological and clinical outcomes. MATERIAL AND METHODS: Consecutive patients who received an Actifit(®) meniscal substitute between 2008 and 2011 were included prospectively. After 1 year and 2 years, the IKDC score and KOOS were determined and magnetic resonance imaging performed. The morphological evaluation consisted in measuring meniscal extrusion and cartilage coverage by the substitute in the coronal and sagittal planes. RESULTS: Twenty patients were included. Among them, 3 required subsequent removal of the substitute. The mean subjective IKDC score increased from 48.1 preoperatively to 56.4 after 2 years. Over the same period, the function/sports/recreational activities component of the KOOS improved significantly (42.9 vs. 55.0, P=0.04). Positive correlations between preoperative and 1-year values were demonstrated for both cartilage coverage in the coronal and the sagittal planes (P=0.03 and P=0.04, respectively) and coronal absolute meniscal extrusion (P=0.05). No significant differences were found between preoperative and 2-year values of cartilage coverage in the coronal and sagittal planes (P=0.38). There was a negative correlation linking preoperative meniscal extrusion in the coronal plane to 1-year cartilage coverage in the coronal and sagittal planes (P=0.01 and P=0.04, respectively). Preoperative absolute meniscal extrusion in the coronal plane correlated negatively with the subjective IKDC score after 1 year (P=0.02). DISCUSSION: Preoperative meniscal extrusion in the coronal plane strongly predicts clinical and morphological outcomes. Marked preoperative meniscal extrusion, even in a patient with symptoms after partial meniscectomy, should prompt an appraisal of whether allograft replacement may be more appropriate than a meniscal substitute. LEVEL OF EVIDENCE: IV, prospective study.

[Results of polyurethane implant for persistent knee pain after partial meniscectomy with a minimum of two years follow-up]. / Resultados de un implante de poliuretano para el tratamiento del dolor persistente de rodilla tras meniscectomía parcial con un mínimo de dos años de seguimiento.

PURPOSE: To present the results of a polyurethane meniscal scaffold implant in 10 patients with persistent pain after meniscectomy. METHODS: Prospective, descriptive study of ten patients who underwent arthroscopic implantation of a polyurethane meniscal scaffold. Functional, MRI, and radiography assessment was performed pre-operatively and at 6-months, 1-year, and a final follow-up at a minimum of two years. Clinical evaluation included Lysholm score, KOOS and VAS. The MRI morphology and signal intensity of the implant were evaluated according to the criteria of Genovese et al. RESULTS: Statistically significant differences were found between the mean Lysholm score before surgery (63.5 points), and that at 6 months (76.8 points) (p=.001), one year (83.3 points) (p<.001) and final follow-up (84.4 points) (p<.001). KOOS showed significant differences between before surgery (64.23 points), 6 months (73.66 points) (p=.001), one year (81.39 points) (p<.001) and final follow-up (83.34 points) (p<.001). The mean values for VAS were 5.7 points in the pre-operative evaluation, 3.6 points at 6 months-follow-up (p<.001), 1.9 points at one year (p<.001), and 1.9 points at final follow-up (p<.001). Radiology showed degenerative changes in one case. In MRI, the size of the implant and the intensity of the MRI signal gradually decreased, but it never changed to that of a normal meniscus. CONCLUSION: A significant improvement was found in all the clinical parameters 24 months after the surgery, except in one patient who underwent furher surgery. The scaffold reduced its size and but never achieved an MRI image similar to that of a normal meniscus. The procedure proved to be safe and useful for the treatment of persistent pain after meniscectomy.