Total meniscus replacement with a 3D printing of network hydrogel composite scaffold in a rabbit model.

PURPOSE: The aim of this study was to evaluate the role of a novel total meniscal implant in promoting meniscal regeneration and protecting articular cartilage in a rabbit model for 3 and 6 months. METHODS: Thirty-six New Zealand rabbits were selected and divided into poly(ɛ-caprolactone) (PG-Pg) scaffold group, meniscectomy group and sham group. In this study, it was investigated whether PG-Pg scaffold can prevent articular cartilage degeneration and promote tissue degeneration, and its mechanical properties at 3 and 6 months after surgery were also explored. RESULT: The degree of articular cartilage degeneration was significantly lower in the PG-Pg scaffold group than in the meniscectomy group. The number of chondrocytes increased in the PG-Pg scaffold at 3 and 6 months, while a gradual increase in the mechanical properties of the PG-Pg stent was observed from 6 months. CONCLUSION: The PG-Pg scaffold slows down the degeneration of articular cartilage, promotes tissue regeneration and improves biomechanical properties after meniscectomy. This novel meniscus scaffold holds promise for enhancing surgical strategies and delivering superior long-term results for individuals with severe meniscus tears. LEVEL OF EVIDENCE: NA.

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.

A Comparison Between Polyurethane and Collagen Meniscal Scaffold for Partial Meniscal Defects: Similar Positive Clinical Results at a Mean of 10 Years of Follow-Up.

PURPOSE: To compare, at long-term follow-up, the clinical outcomes and failures of collagen and polyurethane meniscal scaffolds for the treatment of partial meniscal defects. METHODS: Patients affected by partial meniscal defect with intact anterior and posterior meniscal attachments and an intact rim at the circumference of the missing meniscus were included, treated with a collagen meniscal implant or with polyurethane scaffold, and clinically evaluated by analysis of the subjective International Knee Documentation Committee score, the visual analog scale score for the evaluation of knee function and symptoms, and the Tegner score to assess the activity level. RESULTS: After 3 patients dropped out, a total of 47 patients, comprising 31 men and 16 women, with a mean age of 43 ± 14.1 years and mean body mass index of 25 ± 1.4, were clinically evaluated up to a mean of 10 years' follow-up. The International Knee Documentation Committee score improved from 42.9 ± 15.9 to 67.4 ± 12.4 (P < .0005) in the polyurethane implant group and from 46.8 ± 16.7 to 62.1 ± 22.6 (P < .0005) in the collagen meniscal implant group. The visual analog scale score decreased significantly from baseline values of 5.4 ± 2.3 and 4.4 ± 1.7, to 3.4 ± 2.5 and 2.7 ± 2.4, respectively, at final follow-up in the polyurethane implant (P = .002) and collagen meniscal implant (P < .0005) groups. The Tegner score improved in both groups without reaching the preinjury activity level. No significant differences in the scores were found between the polyurethane and collagen scaffold groups. A total of 10 implants failed, 5 per group, for a cumulative failure rate of 21.3%, with no differences between the 2 scaffolds. CONCLUSIONS: The long-term comparison showed positive and similar results for both polyurethane- and collagen-based meniscal scaffolds, with an implant survival rate of about 80% at 10 years of follow-up and no differences in terms of pain, function, and activity level. LEVEL OF EVIDENCE: Level IV, case-control comparative study.

Polyurethane scaffold implants for partial meniscus lesions: delayed intervention leads to an inferior outcome.

PURPOSE: The purpose of this study was to assess the clinical outcomes of the implantation of an aliphatic polyurethane scaffold for the treatment of partial loss of meniscal tissue at a mean follow-up of 36 months. METHODS: A retrospective review on prospectively collected data was performed on patients who underwent implantation of an aliphatic polyurethane-based synthetic meniscal scaffold. Patients were evaluated for demographics data, lesion and implant characteristics (sizing, type and number of meniscal sutures), previous and combined surgeries and complications. Clinical parameters were rated using NRS, IKDC subjective, Lysholm, KOOS, and Tegner activity score, both preoperatively and at final follow-up. RESULTS: Sixty-seven patients were evaluated at a mean follow-up of 36 months (48 M and 19 F; mean age 40.8 ± 10.6 years; mean BMI 25.4 ± 4.3). The scaffold was implanted on the medial side in 54 cases, and on the lateral one in 13. Forty-seven patients had undergone previous surgical treatment at the same knee and 45 required combined surgical procedures. All evaluated scores improved significantly from the baseline. Among possible prognostic factors, a delayed scaffold implantation had lower post-operative clinical scores: IKDC subjective (P = 0.049), KOOS Sport (P = 0.044), KOOS total (p = 0.011), and Tegner (P = 0.03) scores at follow-up. CONCLUSIONS: The polyurethane meniscal scaffold implantation led to a significant clinical benefit in a large number of patients. A delayed intervention correlated with worse results. LEVEL OF EVIDENCE: IV.

Meniscal scaffold for the treatment of partial meniscal defect-clinical and radiological outcomes in a two-year follow-up.

PURPOSE: The aim of meniscal scaffolds is to fill the defect, allow regeneration of meniscal-like tissues, and to prevent long-term risk of cartilage wear and tear. The aim of this study was to evaluate clinical results after two years and magnetic resonance imaging (MRI) results a year after implantation of a meniscal scaffold. METHODS: Fifteen patients were recruited into a prospective, single-arm, single-center study, and treated with meniscal scaffolds as a result of segmental meniscal defect due to previous partial meniscectomy. Patients were evaluated using functional knee scores used pre-operatively and 6, 12, and 24 months postoperatively. The radiological outcome was assessed using MRI at 12 months by evaluating scaffold size, morphology, and intensity according to the Genovese grading system. Cartilage assessment was completed according to The International Cartilage Repair Society (ICRS) score. RESULTS: All patients completed a follow-up of 24 months. A statistically significant increase in mean levels of all functional scores was present in all patients. On the MRI, all but one of the patients presented an incorporated meniscal implant. In most of the patients (73%), the meniscal implant was a Genovese type III. Type II and III signal intensities were present in all scaffolds when compared with the residual meniscal tissue. A stable cartilage (ICRS) status was observed in 80% of the patients compared with the pre-operative cartilage scores. CONCLUSION: In our case series of patients treated with the meniscal scaffold implant, we observed good clinical results at a two year follow-up. Furthermore, MRI findings suggest that meniscal scaffolds might have a beneficial effect on articular cartilage.

Functional and magnetic resonance imaging outcome after polyurethane meniscal scaffold implantation following partial meniscectomy.

PURPOSE: Prevention of the knee osteoarthritis following meniscectomy is implantation of an allotransplant or an artificial meniscus. We present retrospective study of our early results of the treatment using polyurethane meniscal scaffold. METHODS: From 2016 to 2020, we implanted nine polyurethane scaffolds (Actifit) after partial meniscectomy, five males and four females, age 36 (16-47), BMI 26.7 (17.2-35.9) kg/m2. Functional status, activity, pain, and MRI were assessed. RESULTS: FU 20.8 (6-48.5) months, 35.2 (0-68) months from the meniscectomy to the implantation. The average implant length was 46.1 (35-60) mm, average number of sutures was 7.6 (5-10). Lysholm score before surgery was 61.7 (49-85), after the surgery 86.4 (62-95) with p 0.0045, Tegner activity score before meniscectomy was 5.8 (4-7), after 3.8 (2-5), and after the scaffold implantation 4.6 (3-7) with p 0.0488. Before surgery, VAS score was 3.1 (2-4), and after 7.7 (5-9) with p 0.0042. Pursuant to the Genovese classification, the last follow-up MRI showed a type 2 meniscal morphology in four cases and a type 3 in five cases. Seven patients had type 1 and two had type 2 signal intensity. On average, the absolute extrusion of a transplanted meniscus was 3.67 mm, and the relative extrusion was 0.58 mm. Extrusion progress was not detected. CONCLUSION: Significantly improved knee functionality, increased level of physical activity, and reduced pain. MRI analysis revealed the meniscal transplant morphology and volume loss, as well as its extrusion without progression.

SDF-1 preconditioned HPC scaffolds mobilize cartilage-derived progenitors and stimulate meniscal fibrocartilage repair in human explant tissue culture.

Purpose: The purpose of this study was to characterize the influence of SDF-1 on cell migration/adhesion and temporal gene expression of human cartilage mesenchymal progenitor cells (C-PCs); and to utilize SDF-1 conditioned mesenchymal progenitors to stimulate reintegration of human meniscus fibrocartilage breaks.Materials and Methods: Characterization of SDF-1-induced cell migration was achieved using hydroxypropyl cellulose (HPC) scaffolds pretreated with SDF-1. Fluorescence microscopy and cell counting were used to visualize and quantify the extent of cell migration into scaffolds, respectively. Relative mRNA expression analysis was used to characterize the temporal effects of SDF-1 on C-PCs. Tissue reintegration experiments were conducted using cylindrical human meniscal tissue punches, which were then placed back together with an HPC scaffold embedded with C-PCs. Tensile testing was used to evaluate the extent of tissue reintegration stimulated by human mesenchymal progenitors.Results: C-PCs migrate into scaffolds in response to SDF-1 with the same efficiency as mesenchymal progenitors from human marrow (BM-MSCs). SDF-1 treatment of C-PCs did not significantly alter the expression of early and late stage chondrogenic differentiation genes. Scaffolds containing SDF-1 pre-conditioned C-PCs successfully adhered to fibrocartilage breaks and migrated from the scaffold into the tissue. Tensile testing demonstrated that SDF-1 preconditioned C-PCs stimulate reintegration of fibrocartilage tears.Conclusion: C-PCs migrate in response to SDF-1. Exposure to SDF-1 does not significantly alter the unique mRNA profile of C-PCs that make them desirable for cartilaginous tissue repair applications. SDF-1 pretreated mesenchymal progenitors successfully disperse into injured tissues to help facilitate tissue reintegration.

The Biomechanical Performance of the Latest All-Inside Meniscal Repair Devices.

PURPOSE: To evaluate the biomechanical characteristics of recently introduced meniscal repair devices with a hand-tied, inside-out meniscal suture in a human meniscus model. METHODS: In detached adult human menisci, vertical longitudinal cuts were created 3 mm from the synovial-meniscal junction, simulating a bucket-handle meniscal tear. Each cut was repaired using a single device. Group 1 received a vertical mattress suture of No. 2-0 OrthoCord; group 2, TrueSpan device with PEEK (polyether ether ketone) anchors containing No. 2-0 OrthoCord suture; group 3, TrueSpan device with biodegradable poly-lactide-co-glycolide (PLGA) anchors containing No. 2-0 OrthoCord suture; group 4, Meniscal Cinch II device; group 5, AIR meniscal repair device; and group 6, FasT-Fix 360 device. All samples were preloaded at 5 N and cycled 200 times between 5 and 20 N. The specimens that survived cyclic loading were destructively tested at 12.5 mm/s. Endpoints included maximum load, displacement, stiffness, and failure mode. RESULTS: The mean failure loads were as follows: 95.8 N for OrthoCord suture, 87.1 N for TrueSpan with PEEK, 84.6 N for TrueSpan with PLGA, 48.6 N for Meniscal Cinch II, 72.3 N for AIR, and 68.1 N for FasT-Fix 360. Repairs performed with OrthoCord suture (P = .002) and both TrueSpan devices (P < .03) but not the FasT-Fix 360 device or AIR device were statistically significantly stronger than Meniscal Cinch II repairs. Mean cyclic displacement measured 1.1 mm for OrthoCord, 1.5 mm for TrueSpan with PEEK, 1.5 mm for TrueSpan with PLGA, 2.1 mm for Meniscal Cinch II, 1.1 mm for AIR, and 1.4 mm for FasT-Fix 360. The Meniscal Cinch II device showed more displacement than all other devices (P < .05). The FasT-Fix 360, AIR, and Meniscal Cinch II devices failed by anchor pullout from the peripheral meniscus. OrthoCord and both TrueSpan devices failed by suture pulling through the bucket-handle tissue. CONCLUSIONS: OrthoCord suture is stronger than the AIR, FasT-Fix 360, and Meniscal Cinch II devices. The TrueSpan device with PEEK and TrueSpan device with PLGA are stronger than the Meniscal Cinch II device. The Meniscal Cinch II device failed during cyclic loading with greater cyclic displacement than the AIR device, FasT-Fix 360 device, OrthoCord, and TrueSpan device with PEEK. The Meniscal Cinch II, AIR, and FasT-Fix 360 devices failed by anchor pullout, whereas OrthoCord and both TrueSpan devices failed by suture pull-through. CLINICAL RELEVANCE: Some newly introduced all-inside meniscal repair devices show inferior failure strength compared with earlier versions that might adversely impact clinical outcomes.

Are the Biological and Biomechanical Properties of Meniscal Scaffolds Reflected in Clinical Practice? A Systematic Review of the Literature.

The aim of this PRISMA review was to assess whether the CMI and Actifit scaffolds, when used in clinical practice, improve clinical outcomes and demonstrate the ideal biological and biomechanical properties of scaffolds: being chondroprotective, porous, resorbable, able to mature and promote regeneration of tissue. This was done by only including studies that assessed clinical outcome and used a scale to assess both integrity of the scaffold and its effects on articular cartilage via MRI. A search was performed on PubMed, EMBASE, Scopus and clinicaltrials.gov. 2457 articles were screened, from which eight studies were selected: four used Actifit, three used CMI and one compared the two. All studies reported significant improvement in at least one clinical outcome compared to baseline. Some studies suggested that the scaffolds appeared to show porosity, mature, resorb and/or have possible chondroprotective effects, as assessed by MRI. The evidence for clinical translation is limited by differences in study methodology and small sample sizes, but is promising in terms of improving clinical outcomes in the short to mid-term. Higher level evidence, with MRI and histological evaluation of the scaffold and articular cartilage, is now needed to further determine whether these scaffolds exhibit these useful properties.

Editorial Commentary: Polyurethane Meniscal Scaffold: A Perfect Fit or Flop?

The goal of using a synthetic scaffold to establish a biomechanically functioning meniscus or provide an equivalent meniscus substitute is not achieved by the polycaprolactone-polyurethane Actifit scaffold. Recent research, that did not include a control group, shows that the revision rate is significant, and any improvements in patient outcomes could reflect the associated reconstructive surgery. Based on these data and similar published reports, it is premature to conclude that this implant is clinically indicated. The technique is currently more flop than fit.

Magnetic Resonance Imaging and Functional Outcomes After a Polyurethane Meniscal Scaffold Implantation: Minimum 5-Year Follow-up.

PURPOSE: To report the magnetic resonance imaging (MRI) and clinical outcomes at a minimum 5-year follow-up in a series of patients with postmeniscectomy syndrome and treated with a polyurethane scaffold. METHODS: All consecutive patients operated on from September 2008 to February 2011 for either persistent medial or lateral joint line compartmental pain receiving a polyurethane scaffold due to a previous partial meniscus resection with a minimum 5-year follow-up were included. Functional scores (Knee Injury and Osteoarthritis Outcomes Score, International Knee Documentation Committee, Lysholm, and Tegner) were assessed preoperatively and at the last follow-up. The state of the scaffold as well as postoperative scaffold extrusion and the total remaining meniscal volume was also evaluated in MRI. RESULTS: Thirty-two patients were included. The mean follow-up was 70.8 ± 7.5 months. The functionality of the knees improved in all the scores used (P < .001) except for the Tegner score that stayed steady. Most of meniscal implants showed extrusion of 2.4 mm (95% confidence interval [CI], 1.1-3.7) were smaller and a hyperintensity signal was seen in the MRI. Three scaffolds were resorbed at the last follow-up. The meniscal volume, determined by MRI, was 1.14 cm3 (95% CI, 0.96-1.31) preoperatively and 1.61 cm3 (95% CI, 1.43-1.7) at the last follow-up. No differences were presented. CONCLUSIONS: The use of a polyurethane meniscal scaffold in patients with a symptomatic meniscus deficit had a good functional outcome at 5 years after surgery. However, the implanted scaffolds did not present normal meniscal tissue with MRI, and the implant volume was considerably less than expected. The fact that most of patients included received different concomitant procedures during scaffold implantation introduces a degree of performance bias into the results. LEVEL OF EVIDENCE: Level IV, case series.

Successful anterior cruciate ligament reconstruction and meniscal repair in osteogenesis imperfecta.

A case of anterior cruciate ligament (ACL) reconstruction with meniscal repair in an osteogenesis imperfecta patient is reported. A 24-year-old female with osteogenesis imperfecta type 1a suffered from a valgus extension injury resulting in tear of ACL and medial meniscus. She underwent an arthroscopic-assisted ACL reconstruction and medial meniscus repair. Meniscal tear at the menisco-capsular junction of the posterior horn of medial meniscus was repaired with three absorbable sutures via inside-out technique. ACL reconstruction was then performed with a bone-patellar tendon-bone allograft. The patient was followed up for 1 year with intact ACL grafts and healed medial meniscus. This case report showed that successful ACL reconstruction and meniscal repair is possible in an osteogenesis imperfecta patient.Level of evidence V.

Similar clinical outcomes following collagen or polyurethane meniscal scaffold implantation: a systematic review.

PURPOSE: The purpose of this systematic review is to evaluate the current literature in an effort to assess specific clinical outcomes following meniscal scaffold implantation using the two available scaffolds: Collagen Meniscal Implant (CMI) and the Actifit polyurethane meniscal scaffold. METHODS: A systematic review was performed by searching PubMed, Embase, and Cochrane Library to find studies evaluating clinical outcomes of patients undergoing meniscal scaffold implantation. Search terms used were "meniscus", "meniscal", "scaffold", and "implant". Studies were evaluated based on scaffold type, treatment failure rates, patient-reported outcome scores, concomitant procedures, and radiological findings. Radiological findings were recorded using the Genovese scale to assess morphology and signal intensity and the Yulish score to assess articular cartilage. RESULTS: Nineteen studies (1 level I, 1 level II, 17 level IV evidence) were identified that met inclusion criteria, including a total of 658 patients (347 Actifit, 311 CMI). The overall average follow-up was 45 months. Treatment failure occurred in 9.9% of patients receiving the Actifit scaffold at a mean follow-up of 40 months and 6.7% of patients receiving CMI at a mean follow-up of 44 months (n.s.). However, the rate of failure ranged from 0 to 31.8% amongst the included studies with a variable definition of failure. Additionally, overlapping patients and presence of concomitant surgeries such as anterior cruciate ligament reconstruction (ACLR) and high tibial osteotomy (HTO) may have a significant influence on these results. Outcomes for the Visual Analog Scale (VAS) for pain, Lysholm knee score, and Tegner activity score improved from preoperatively to latest follow-up in both groups, while the Knee Injury and Osteoarthritis Outcome Score and International Knee Documentation Committee scores improved from preoperatively to latest follow-up for Actifit scaffold patients. Overall, patients receiving CMI scaffolds had higher grades for Genovese morphology and signal intensity when compared to Actifit scaffold patients. CONCLUSION: Patients undergoing meniscal scaffold implantation with either CMI or Actifit scaffold can both be expected to experience improvement in clinical outcomes when used in association with concomitant procedures such as ACLR and HTO. LEVEL OF EVIDENCE: IV, systematic review.

Polyurethane meniscal scaffolds lead to better clinical outcomes but worse articular cartilage status and greater absolute meniscal extrusion.

PURPOSE: Implantation of polyurethane (PU) meniscal scaffolds has become a popular procedure to provide a scaffold for vessel ingrowth and meniscal tissue regeneration in patients with partial meniscal defects. However, it is unclear whether PU meniscal scaffolds lead to better clinical and magnetic resonance imaging (MRI) outcomes post-operatively. This meta-analysis compared the clinical and MRI outcomes in patients with partial meniscal defects treated with PU meniscal scaffolds. METHODS: This meta-analysis reviewed all studies that assessed Lysholm score, International Knee Documentation Committee (IKDC) score, visual analogue scale (VAS) for pain, Tegner score, Knee Injury and Osteoarthritis Outcomes Score (KOOS), articular cartilage (AC), absolute meniscal extrusion (AME), morphology and size (MS), signal intensity (SI) of meniscal implant, and interface of the implant-residual meniscus complex (IIRMC) in patients with partial meniscal defects treated with PU meniscal scaffolds. RESULTS: Eighteen studies were included in the meta-analysis. The proportion of patients who evaluated MS (OR 0.71, 95% CI 0.38-1.33; n.s.), SI (OR 1.07, 95% CI 0.53-2.18; n.s.), and IIRMC (OR 1.00, 95% CI 0.33-3.06; n.s.) did not differ significantly between baseline and final follow-up. However, AC (OR 0.31, 95% CI 0.11-0.84; P = 0.02) and AME (OR 0.05, 95% CI 0.01-0.18; P < 0.00001) worsened between baseline and final follow-up. Conversely, Lysholm score (95% CI -1.87 to -1.07; P < 0.00001), IKDC score (95% CI -2.19 to -1.08; P < 0.00001), VAS for pain (95% CI -2.29 to -1.07; P < 0.00001), Tegner score (95% CI -0.76 to -0.15; P = 0.003), and overall KOOS (95% CI -29.48 to -23.17; P < 0.00001) were significantly greater at final follow-up when compared to baseline. CONCLUSION: This meta-analysis found no significant differences in the tested MRI parameters, including MS, SI, and IIRMC. However, AC and AME worsened between baseline and final follow-up. Conversely, patients treated with PU meniscal scaffolds showed significant functional improvement and pain relief when compared with baseline scores. Thus, PU meniscal scaffolds appear to be a viable alternative for patients with partial meniscal defects, although further studies are needed to determine whether worsened AC and AME are clinically relevant. In particular, precise measurement of PU meniscal scaffolds in combination with thorough investigation of the baseline articular cartilage status and meniscal defect size may be effective for pain relief or functional improvement in patients with PU meniscal scaffold implantation. LEVEL OF EVIDENCE: III.

The effect of tissue surface modification with collagenase and addition of TGF-ß3 on the healing potential of meniscal tears repaired with tissue glues in vitro.

The aim of the current in vitro study was to investigate if tissue surface modification with collagenase and addition of the TGF-ß3 can increase the number of cells present in meniscus tears repaired with the use of newly developed tissue adhesives based on isocyanate-terminated block copolymers. Cylindrical explants were harvested from the inner part of bovine menisci. To simulate a full-thickness tear, the central core of the explants was removed and glued back into the defect, with or without incubation in collagenase solution prior to gluing. The repair constructs were then cultured with or without addition of TGF-ß3, and assessed for their histological appearance. The histological staining of the constructs confirmed that both developed adhesives were not cytotoxic. After 28 days, meniscus cells were present in direct contact with the glues. The addition of TGF-ß3 to the culture medium resulted in the presence of cells that formed a sheath inside the simulated tear and in increased cell numbers at the edges of annulus of the explants. In the group in which the tissue was incubated in collagenase and cultured in medium containing TGF-ß3, thicker layers of cells were observed. These results suggest that repairing the torn meniscus with tissue adhesives after pre-treatment of the tissue with collagenase and stimulation with TGF-ß3 is a very promising treatment method, especially when treating the inner avascular part of the meniscus. Nevertheless, longer-term in vitro and in vivo studies are needed to confirm the beneficial effects of this combination therapy.

Polyurethane-based cell-free scaffold for the treatment of painful partial meniscus loss.

PURPOSE: The aim of this study was to document, at mid-term follow-up, the clinical and MRI outcome of a polyurethane-based cell-free scaffold implanted to treat painful partial meniscus loss. METHODS: Eighteen consecutive patients were enrolled and treated with arthroscopic polyurethane meniscal scaffold implantation and, in case of other comorbidities, with concurrent surgical procedures: 16 patients (9 men and 7 women, mean age 45 ± 13 years, mean BMI 25 ± 3, 12 medial and 4 lateral implants) were prospectively evaluated with the subjective and objective IKDC and the Tegner scores at 24, 36, 48, 60, and 72 months of follow-up. Eleven patients were also evaluated by 1.5-T MRI at the final follow-up. RESULTS: The IKDC subjective score showed a significant improvement from baseline to 24 months (45.6 ± 17.5 and 75.3 ± 14.8, respectively; p = 0.02) and subsequent stable results over time for up to 72 months (final score 75.0 ± 16.8). The Tegner score improvement between pre-operative status and final follow-up was also significant (p = 0.039). Nevertheless, the final score remained significantly lower than the pre-injury sports activity level (p = 0.027). High-resolution MRIs documented the presence of abnormal findings in terms of morphology, signal intensity, and interface between the implant and the native meniscus. Implant extrusion and bone oedema at the treated compartment were also observed in most of the cases, even though no correlation was found between imaging findings and clinical outcome. CONCLUSIONS: The present study reports satisfactory clinical outcomes at mid-term follow-up after polyurethane-based meniscal cell-free scaffold implantation. The treatment was effective both in cases of isolated partial meniscal lesions and in complex cases requiring the combination with other surgical procedures. On the other hand, a high rate of altered MRI aspects was documented. However, no correlation was found between the altered imaging parameters and the overall positive clinical findings, thus supporting the use of this procedure to treat painful partial meniscus loss. LEVEL OF EVIDENCE: Case series, Level IV.

[Indication and limitations of meniscus replacement]. / Indikation und Grenzen des Meniskusersatzes.

BACKGROUND: Meniscal lesions are among the most important musculoskeletal disorders and are the most common indication for knee joint arthroplasty. However, the structural integrity and function is rarely retained, and a loss of tissue results. Thus, there is a huge demand for meniscal replacement options. CURRENT PROCEDURES: Autografts were used in the past but did not fulfill expectations. Meniscus allografts have been developed to be a viable treatment option. However, availability is limited and evidence of a long-term chondroprotective effect scarce. Artificial scaffolds made from either collagen or PCU foam are available, which aid the regeneration of meniscal tissue and are rather intended as a partial replacement with an intact peripheral rim. Those implants thus have a limited spectrum of indication. While they seem to be symptomatically effective, it remains unclear whether they can reduce secondary cartilage damage. Newer developments aim at a permanent replacement of lost meniscal tissue. LIMITATIONS: In summary, there is currently no meniscal replacement available for a broad range of indications and with a solid scientific foundation. Prophylactic use should be limited to cases with a high chance of progression to osteoarthritis, like a lateral total meniscectomy. Otherwise meniscal replacement should be considered in younger, symptomatic patients with mild to moderate secondary changes. Potential causes of the initial meniscal injury like instability or deformities should be carefully assessed and addressed. In many cases, osteotomy might be a viable alternative to meniscus replacement.

Tissue adhesives for meniscus tear repair: an overview of current advances and prospects for future clinical solutions.

Menisci are crucial structures in the knee joint as they play important functions in load transfer, maintaining joint stability and in homeostasis of articular cartilage. Unfortunately, ones of the most frequently occurring knee injuries are meniscal tears. Particularly tears in the avascular zone of the meniscus usually do not heal spontaneously and lead to pain, swelling and locking of the knee joint. Eventually, after a (partial) meniscectomy, they will lead to osteoarthritis. Current treatment modalities to repair tears and by that restore the integrity of the native meniscus still carry their drawbacks and a new robust solution is desired. A strong tissue adhesive could provide such a solution and could potentially improve on sutures, which are the current gold standard. Moreover, a glue could serve as a carrier for biological compounds known to enhance tissue healing. Only few tissue adhesives, e.g., Dermabond(®) and fibrin glue, are already successfully used in clinical practice for other applications, but are not considered suitable for gluing meniscus tissue due to their sub-optimal mechanical properties or toxicity. There is a growing interest and research field focusing on the development of novel polymer-based tissue adhesives, but up to now, there is no material specially designed for the repair of meniscal tears. In this review, we discuss the current clinical gold standard treatment of meniscal tears and present an overview of new developments in this field. Moreover, we discuss the properties of different tissue adhesives for their potential use in meniscal tear repair. Finally, we formulate recommendations regarding the design criteria of material properties and adhesive strength for clinically applicable glues for meniscal tears.

Midterm follow-up after implantation of a polyurethane meniscal scaffold for segmental medial meniscus loss: maintenance of good clinical and MRI outcome.

PURPOSE: The preservation of meniscal structure and function after segmental meniscal loss is of crucial importance to prevent early development of osteoarthritis. Implantation of artificial meniscal implants has been reported as a feasible treatment option. The purpose of this study was to assess the clinical and magnetic resonance imaging (MRI) results 4 years after implantation of a polyurethane scaffold for chronic segmental medial meniscus deficiency following partial medial meniscectomy. METHODS: Eighteen patients received arthroscopic implantation of an Actifit(®) polyurethane meniscal implant (Orteq Sports Medicine, London, UK) for deficiency of the medial meniscus. Patients were followed at 6, 12, 24, and 48 months. Clinical outcome was assessed using established patient-reported outcome scores (KOOS, KSS, UCLA Activity Scale, VAS for pain). Radiological outcome was quantified by MRI scans after 6, 12, 24, and 48 months evaluating scaffold morphology, tissue integration, and status of the articular cartilage as well as signs of inflammation. RESULTS: Median patient age was 32.5 years (range 17-49 years) with a median meniscal defect size of 44.5 mm (range 35-62 mm). Continuing improvement of the VAS and KSS Knee and Function Scores could be observed after 48 months compared to baseline, whereas improvement of the activity level according to UCLA continued only up to 24 months and decreased from there on. The KOOS Score showed significant improvement in all dimensions. MRI scans showed reappearance of bone bruises in two patients with scaffold extrusion. No significant changes in the articular cartilage could be perceived. CONCLUSION: Arthroscopic treatment for patients with chronic segmental meniscal loss using a polyurethane meniscal implant can achieve sustainable midterm results regarding pain reduction and knee function. LEVEL OF EVIDENCE: IV.