No differences in clinical outcome between CMI and Actifit meniscal scaffolds: a systematic review and meta-analysis

Biologic Augmentation of Isolated Meniscal Repair

PURPOSE OF REVIEW

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.

RECENT FINDINGS

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.

Safety and Efficacy of a Novel Polyglycolic Acid Meniscal Scaffold for Irreparable Meniscal Tear

OBJECTIVE

Meniscal tears treated with a partial meniscectomy could induce knee osteoarthritis, thereby altering or damaging knee kinetics and biomechanics. We have developed a meniscal scaffold made of polyglycolic acid (PGA) coated with polylactic acid/caprolactone (PGA scaffold), which could induce new tissue growth of meniscus-like tissue. This study aimed to evaluate the safety and efficacy of a novel meniscal scaffold for the treatment of irreparable meniscal injuries.

DESIGN

This study describes the findings of a cyclic torque test and first clinical trial of a PGA scaffold for inducing meniscus-like tissue in humans. As the first step, biomechanical testing of the PGA scaffold was performed using a cyclic torque test. Six patients underwent arthroscopic implantation of the PGA scaffold. Furthermore, the patients underwent preoperative clinical, serological, radiographic, and magnetic resonance imaging examinations at 3, 6, and 12 months postoperatively. The patients also underwent a second-look arthroscopy 12 months after implantation.

RESULTS

Torque increased with increasing cyclic loading. However, no structural damage to the sample was noted after 70,000 loading cycles. All patients showed improvement in pain, Lysholm scores, Tegner activity scores, International Knee Documentation Committee, and knee injury and osteoarthritis outcome. The second-look arthroscopy revealed that meniscal tissue had regenerated in 5 patients (83%). Radiography and magnetic resonance imaging confirmed no progression of degenerative joint disease.

CONCLUSIONS

The PGA scaffold could tolerate shear forces, did not produce safety concerns, and may have therapeutic potentials for irreparable meniscal tears in humans.

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.

Clinical Outcomes After Polyurethane Meniscal Scaffolds Implantation Remain Stable Despite a Joint Space Narrowing at 10-Year Follow-Up

PURPOSE

To report the clinical outcomes, radiologic evolution, and survivorship of a series of patients affected by the postmeniscectomy syndrome and treated with a polyurethane scaffold at a minimum 10-year follow-up. In addition, the radiologic evolution of these patients was also assessed.

METHODS

All the patients operated on with a polyurethane meniscal scaffold implantation to treat postmeniscectomy syndrome from 2008 to 2011 were prospectively followed. Clinical evaluations and radiologic studies were assessed at the preoperative period, at 5-year follow-up, and at minimum 10-year follow-up. Clinical outcomes were based on patient-reported outcomes (e.g., the Knee injury and Osteoarthritis Outcome Score, International Knee Documentation Committee, Lysholm, and Tegner). Radiographical evaluation of the joint-space narrowing was done in the Rosenberg view. Failure was defined as patients who required surgery to remove the scaffold or those patients who needed surgery for a total or partial knee replacement.

RESULTS

Twenty-one of 27 patients, with a mean age of 56 ± 9.8 years, were available for the final follow-up. The mean follow-up was 11.8 (range, 10-12.7) years. Six patients were lost to follow-up. All functional scores showed a significant improvement (P < .001) at the 5- and 10-year follow-up. The exception was the Tegner score, which remained stable. The joint-space width was maintained from the preoperative period (1.9 ± 1.2 mm) up to the 5-year follow-up (1.3 ± 1.5 mm, P = .3) and decreased by the last evaluation (0.6 ± 1.2 mm, P = .001) at the last follow-up. Two (9.5%) of 21 patients were converted to a total knee replacement during the study period. None of the other patients needed revision surgery during the study period.

CONCLUSIONS

The polyurethane meniscal scaffold provides significant and stable pain relief over time and improved functional outcomes at a minimum of 10 years after surgery. However, degenerative changes progressed in the treated compartment, with a joint-space narrowing over the 10-year period.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

Fibronectin-coated polyurethane meniscal scaffolding supplemented with MSCs improves scaffold integration and proteoglycan production in a rabbit model

PURPOSE

The role of mesenchymal stem cells (MSC) in supporting the formation of new meniscal tissue in a meniscal scaffold is not well understood. The objective of this study was to assess the quality of the meniscal tissue produced in a fibronectin (FN)-coated polyurethane (PU) meniscal scaffold after a meniscal injury was made in an experimental rabbit model.

METHODS

Twelve New Zealand white rabbits were divided in two groups after performing a medial meniscectomy of the anterior horn. In group 1, the meniscal defect was reconstructed with a non-MSC supplemented FN-coated PU scaffold. On the other hand, the same scaffold supplemented with MSCs was used in group 2. The animals were sacrificed at 12 week after index surgery. A modified scoring system was used for histological assessment. This new scoring (ranging from 0 to 15) includes a structural evaluation (meniscal scaffold interface and extracellular matrix production) and tissue quality evaluation (proteoglycan and type I-collagen content).

RESULTS

The meniscal scaffold was found loose in the joint in three cases, corresponding to two cases in group 1 and 1 case in group 2. No differences were observed between the groups in terms of the total score (7.0 ± 0.9 vs. 9.4 ± 2.6, p = 0.09). However, differences were observed in group 2 in which 2 out of the 5 scored items, scaffold integration (1 ± 0.0 vs. 1.9 ± 0.6, p = 0.03) and proteoglycan production (1.2 ± 0.3 vs. 2.4 ± 0.2, p = 0.001). A trend to a higher production of Type I-Collagen production was also observed in group 2 (1.1 ± 0.4 vs. 1.4 ± 0.7, p = 0.05).

CONCLUSION

In a rabbit model at 12 weeks, the adhesion of MSCs to a FN-coated PU scaffold improves scaffold integration, proteoglycan production and the characteristics of the new meniscal-like tissue obtained when compared to a non-supplemented scaffold. This fact could be a major step toward improving the adhesion of the MSCs to meniscal scaffolds and, consequently, the obtention of better quality meniscal tissue.

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

INTRODUCTION

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 5 years.

METHODS

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).

RESULTS

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).

CONCLUSION

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.

LEVEL OF EVIDENCE

II, therapeutic study.

Does laterality matter? a systematic review and meta-analysis of clinical and survival outcomes of medial versus lateral meniscal scaffolds

PURPOSE

Meniscal scaffold implants have gained interestas a therapeutic alternative for irreparable partial meniscal defects and post-meniscectomy syndrome. However, the effect of laterality on outcomes is unclear. This study aimsto assess the hypothesis that lateral meniscal scaffold implants have worse clinical or survival outcomes compared with medial scaffold implants.

METHODS

The study was performedaccording to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines and registered with PROSPERO. Three databases (PubMed, Embase, Scopus) were searched from date of database establishment to 21 January 2022. Human studies reporting clinical or survival outcomedata specific to the medial or lateral meniscal scaffold implant were included. Random-effects model was used to analyse survival outcome data.

RESULTS

Ten studies comprising 568 patients (mean age 29.2-40 years, follow up duration 1-14 years) were included. There were 483 medial and 85 lateral meniscal scaffold implants. Amongst two studies directly comparing the survival rate of medial and lateral meniscal scaffolds, there was no significant difference in survival rates between medial and lateral meniscus scaffolds (hazard ratio = 1.24, 95 % confidence interval: 0.51-3.03, P = 0.63). There were no consistent statistically significant differences between medial and lateral meniscal scaffolds in terms of postoperative Visual Analog Scale pain,Tegner Activity, Lysholm, International Knee Documentation Committee, Knee Injury and Osteoarthritis Outcome, and Knee Society Scores.

CONCLUSION

Despite anatomical and biomechanical differences between the medial and lateral meniscus, there are no significant differences in clinical outcomes or survival rates between medial and lateral meniscal scaffold implants for irreparable partial meniscal defects at short- or mid-term follow up. Lateral meniscal scaffold implants are therefore non-inferior to medial meniscal scaffold implants.

MRI follow up of bilateral partial meniscal substitution with a demineralized bone block. A case report

The case of a 60-year-old male is described, who presented in 2020 with a symptomatic degenerative bilateral posterior horn lesion of the medial meniscus. On MRI both lesions appeared identical as 60%-70% incomplete radial tears in the posterior horn of the medial meniscus with a flap tear component. The patient was arthroscopically treated with bilateral implantation of a demineralized bone block as a partial medial meniscus substitute. A complete isointense and homogenous signal was recorded after 16 weeks and 12 months on the right knee and after 12 weeks on the left knee, indicating a complete ingrowth and remodeling of the implant. KOOS and IKDC score improved from 81 and 66% presurgery to 94 and 93%, respectively, 6 months after the second partial medial meniscus substitution on the left knee.

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.

Clinical Replacement Strategies for Meniscus Tissue Deficiency

Meniscus tissue deficiency resulting from primary meniscectomy or meniscectomy after failed repair is a clinical challenge because the meniscus has little to no capacity for regeneration. Loss of meniscus tissue has been associated with early-onset knee osteoarthritis due to an increase in joint contact pressures in meniscectomized knees. Clinically available replacement strategies range from allograft transplantation to synthetic implants, including the collagen meniscus implant, ACTIfit, and NUSurface. Although short-term efficacy has been demonstrated with some of these treatments, factors such as long-term durability, chondroprotective efficacy, and return to sport activities in young patients remain unpredictable. Investigations of cell-based and tissue-engineered strategies to treat meniscus tissue deficiency are ongoing.