Meniscus Replacement: From Allograft to Tissue Engineering

Meniscal Salvage: Where We Are Today

The menisci are fibrocartilaginous semilunar structures in the knee that provide load support. Injury to the meniscus alters its load sharing and biomechanical profile. Knee arthroscopy with meniscus débridement is the most common orthopaedic surgical procedure done in the United States. The current goals of meniscal surgery are to preserve native meniscal tissue and maintain structural integrity. Meniscal preservation is critical to maintain the normal mechanics and homeostasis of the knee; however, it is not always feasible because of the structure's poor blood supply and often requires removal of irreparable tissue with meniscectomy. Efforts have increasingly focused on the promotion of meniscal healing and the replacement of damaged menisci with allografts, scaffolds, meniscal implants, or substitutes. The purpose of this article was to review current and future meniscal salvage treatments such as meniscus transplant, synthetic arthroplasty, and possible bioprinted meniscus to allow patients to maintain quality of life, limit pain, and delay osteoarthritis.

Polyurethane Meniscal Scaffold for the Treatment of Partial Meniscal Deficiency: 5-Year Follow-up Outcomes: A European Multicentric Study

BACKGROUND

A biodegradable polyurethane scaffold was developed to treat patients with the challenging clinical condition of painful partial meniscal defects.

HYPOTHESIS

The use of an acellular polyurethane scaffold in patients with symptomatic partial meniscal defects would result in both midterm pain relief and improved function.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

A total of 155 patients with symptomatic partial meniscal defects (101 medial and 54 lateral) were implanted with a polyurethane scaffold in a prospective, single-arm, multicentric study with a minimum 5-year follow-up. Clinical outcomes were measured with the visual analog scale for pain, International Knee Documentation Committee subjective knee evaluation form, Lysholm knee scale, and Knee injury and Osteoarthritis Outcome Score at baseline and at 2- and 5-year follow-ups. Magnetic resonance imaging (MRI) was used to evaluate the knee joint, meniscal implant, and meniscal extrusion. Kaplan-Meier survival analysis was also performed. Removal of the scaffold, conversion to a meniscal transplant, and unicompartmental/total knee arthroplasty were used as endpoints.

RESULTS

Eighteen patients were lost to follow-up (11.6%). The patients who were included in this study showed significant clinical improvement after surgery as indicated by the different outcome measures (P = .01). However, the clinical improvement tended to stabilize between 2 and 5 years of follow-up. MRI scans of the scaffolds in 56 patients showed a smaller-sized implant in the majority of the cases when compared with the native meniscus with an irregular surface at the 5-year follow-up. During the follow-up period, 87.6% of the implants survived in this study. At 5 years of follow-up, 87.9% of the medial scaffolds were still functioning versus 86.9% of the lateral scaffolds. In total, 23 treatments had failed: 10 removed scaffolds because of breakage, 7 conversions to meniscal allograft transplantation, 4 conversions to unicompartmental knee arthroplasty, and 2 conversions to total knee arthroplasty.

CONCLUSION

The polyurethane meniscal implant was able to improve knee joint function and reduce pain in patients with segmental meniscal deficiency over 5 years after implantation. The MRI appearance of this scaffold was different from the original meniscal tissue at the midterm follow-up. The treatment survival rates of 87.9% of the medial scaffolds and 86.9% of the lateral scaffolds in the present study compared favorably with those published concerning meniscal allograft transplantation after total meniscectomy.

Materials and structures used in meniscus repair and regeneration: a review

Meniscus is a vital functional unit in knee joint. It acts as a lubricating structure, a nutrient transporting structure, as well as shock absorber during jumping, twisting and running and offers stability within the knee joint. It helps in load distribution, in bearing the tensile hoop stresses and balancing by providing a cushion effect between hard surfaces of two bones. Meniscus may be injured in sports, dancing, accident or any over stressed condition. Any meniscal lesion can lead to a gradual development of osteoarthritis or erosion of bone contact surface due to disturbed load and contact stress distribution caused by injury/pain. Once injured, the possibilities of self-repair are rare in avascular region of meniscus, due to lack of blood supply in avascular region. Meniscus has vascular and avascular regions in structure. Majority of the meniscus parts turn avascular with increase in age.

Purpose of this review is to highlight advances in meniscus repair with special focus on tissue engineering using textile/fiber based scaffolds, as well as the recent technical advances in scaffolds for meniscus recon- struction/ regeneration treatment.

Modern treatment of meniscal tears

The complex ultrastructure of the meniscus determines its vital functions for the knee, the lower extremity, and the body.

The most recent concise, reliable, and valid classification system for meniscal tears is the International Society of Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine (ISAKOS) Classification, which takes into account the subsequent parameters: tear depth, tear pattern, tear length, tear location/rim width, radial location, location according to the popliteal hiatus, and quality of the meniscal tissue.

It is the orthopaedic surgeon’s responsibility to combine clinical information, radiological images, and clinical experience in an effort to individualize management of meniscal tears, taking into account factors related to the patient and lesion.

Surgeons should strive not to operate in most cases, but to protect, repair or reconstruct, in order to prevent early development of osteoarthritis by restoring the native structure, function, and biomechanics of the meniscus.

Currently, there are three main methods of modern surgical management of meniscus tears: arthroscopic partial meniscectomy; meniscal repair with or without augmentation techniques; and meniscal reconstruction. Meniscus surgery has come a long way from the old slogan, “If it is torn, take it out!” to the currently accepted slogan, “Save the meniscus!” which has guided evolving modern treatment methods for meniscal tears. This last slogan will probably constitute the basis for newer alternative biological treatment methods in the future.

Cite this article: EFORT Open Rev 2018;3 DOI: 10.1302/2058-5241.3.170067.

Treatment of Painful, Irreparable Partial Meniscal Defects With a Polyurethane Scaffold: Midterm Clinical Outcomes and Survival Analysis

BACKGROUND

A biodegradable polyurethane scaffold was designed to fulfill a challenging clinical need in the treatment of patients with painful, irreparable partial meniscal defects.

HYPOTHESIS

The use of an acellular polyurethane scaffold for new tissue generation in irreparable, partial meniscal defects provides both midterm pain relief and improved functionality.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

A total of 44 patients with irreparable, partial meniscal defects (29 medial and 15 lateral) were implanted with a polyurethane scaffold in a prospective, single-arm proof-of-principle study with a minimum 5-year follow-up. Clinical outcomes were measured with the visual analog scale (VAS) for pain, International Knee Documentation Committee (IKDC), and Knee injury and Osteoarthritis Outcome Score (KOOS) at baseline and at 2- and 5-year follow-up. Magnetic resonance imaging (MRI) was used to evaluate the meniscal implant and cartilage status of the index compartment. Kaplan-Meier time-to-treatment failure distributions were also performed. Removal of the scaffold, conversion to a meniscal transplant, or unicompartmental/total knee arthroplasty was used as endpoints.

RESULTS

Seven patients were lost to follow-up (15.9%). The patients who participated in this study showed significant clinical improvement after surgery (mean [±SD] at baseline, 2 years, and 5 years: 56.2 ± 21.6, 24.6 ± 22.7, and 19.3 ± 26.9, respectively [VAS]; 206.5 ± 79.7, 329.8 ± 108.9, and 333.6 ± 112.2, respectively [total KOOS]). MRI of the scaffolds showed a smaller sized implant when compared with the native meniscus with an irregular surface at 2- and 5-year follow-up. A stable cartilage status of the index compartment at 5-year follow-up was demonstrated in 46.7% of patients compared with the baseline status. During the follow-up period, 62.2% of the implants survived. At final follow-up, 66.7% of the medial scaffolds were still functioning versus 53.8% of the lateral scaffolds.

CONCLUSION

A polyurethane meniscal implant can improve knee joint function and significantly reduce pain in patients with segmental meniscus deficiency up to 5 years after implantation. A stable cartilage status of the index compartment at 5-year follow-up was demonstrated in 46.7% of patients, calling into question the chondroprotective ability of the implant. In addition, a relatively high failure rate was noticed. Long-term and randomized controlled studies are mandatory to confirm the initial results and the reliability of this procedure.

Cryogel-PCL combination scaffolds for bone tissue repair

The present work describes the development and the evaluation of cryogel-poly-ε-caprolactone combinatory scaffolds for bone tissue engineering. Gelatin was selected as cell-interactive biopolymer to enable the adhesion and the proliferation of mouse calvaria pre-osteoblasts while poly-ε-caprolactone was applied for its mechanical strength required for the envisaged application. In order to realize suitable osteoblast carriers, methacrylamide-functionalized gelatin was introduced into 3D printed poly-ε-caprolactone scaffolds created using the Bioplotter technology, followed by performing a cryogenic treatment which was concomitant with the redox-initiated, covalent crosslinking of the gelatin derivative (i.e. cryogelation). In a first part, the efficiency of the cryogelation process was determined using gel fraction experiments and by correlating the results with conventional hydrogel formation at room temperature. Next, the optimal cryogelation parameters were fed into the combinatory approach and the scaffolds developed were characterized for their structural and mechanical properties using scanning electron microscopy, micro-computed tomography and compression tests respectively. In a final part, in vitro biocompatibility assays indicated a good colonization of the pre-osteoblasts and the attachment of viable cells onto the cryogenic network. However, the results also show that the cellular infiltration throughout the entire scaffold is suboptimal, which implies that the scaffold design should be optimized by reducing the cryogel density.

Scaffolds for partial meniscal replacement: an updated systematic review

INTRODUCTION

Meniscectomy, a most common orthopaedic procedure, results in increased contact area of the articular surfaces of tibia and femur leading to early osteoarthritis. We systematically review the literature on clinical outcomes following partial meniscal replacement using different scaffolds.

SOURCES OF DATA

We performed a comprehensive search of Medline, CINAHL, Embase and the Cochrane Central Registry of Controlled Trials. The reference lists of the selected articles were then examined by hand. Only studies focusing on investigation of clinical outcomes on patients undergoing a partial meniscal replacement using a scaffold were selected. We then evaluated the methodological quality of each article using the Coleman methodology score (CMS), a 10 criteria scoring list assessing the methodological quality of the selected studies (CMS).

AREAS OF AGREEMENT

Fifteen studies were included, all prospective studies, but only 2 were randomized controlled trials. Biological scaffolds were involved in 12 studies, 2 studies investigated synthetic scaffolds, whereas 1 remaining article presented data from the use of both classes of device. The mean modified CMS was 64.6.

AREAS OF CONTROVERSY

Several demographic and biomechanical factors could influence the outcomes of this treatment modality.

GROWING POINTS

Partial replacement using both classes of scaffolds achieves significant and encouraging improved clinical results when compared with baseline values or with controls when present, without no adverse reaction related to the device.

RESEARCH

There is a need for more and better designed randomized trials, to confirm with a stronger level of evidence the promising preliminary results achieved by the current research.

Meniscal scaffolds: early experience and review of the literature

INTRODUCTION

Meniscal scaffold implants support the in-growth of new "meniscus like" tissue with the aim of alleviating post-meniscectomy knee pain and preventing further articular cartilage degeneration.

PATIENTS AND METHODS

Twenty-three patients underwent meniscal scaffold implantation (14 medial, 9 lateral) with either the Menaflex (ReGen Biologics) (n=12) or Actifit (Orteq) (n=11) scaffolds. Minimum follow-up was 1 year with a mean of 24.1 months (18-27) for the Menaflex and 14.7 months (12-18) for the Actifit groups. Mean age at surgery was 35 years (17-47) with a mean Outerbridge grade of 1.9 in the affected compartment. Eight (36%) underwent concurrent osteotomy, ligament reconstruction or microfracture of the tibial plateau. KOOS, Lysholm, Tegner activity and IKDC scores were collected pre-operatively and at six-month interval post-surgery. Assessment of the reconstruction was obtained with MRI scanning and arthroscopy. One scaffold tore and was revised at 19 months post-operatively.

RESULTS

Twenty-one out of 23 (91.3%) had a significant improvement in knee scores when compared to pre-surgery levels at latest follow-up. Second-look arthroscopy in 14 at 1-year post-implantation showed variable amounts of regenerative tissue. There was no progression in chondral wear noted on repeat MRI scanning.

CONCLUSION

Treatment with meniscal scaffold implants can provide good pain relief for the post-meniscectomy knee following partial meniscectomy. Longer follow-up is required to ascertain whether they also prevent the progressive chondral wear associated with a post-meniscectomy knee.

Successful treatment of painful irreparable partial meniscal defects with a polyurethane scaffold: two-year safety and clinical outcomes

BACKGROUND

A novel, biodegradable, polyurethane scaffold was designed to fulfill an unmet clinical need in the treatment of patients with painful irreparable partial meniscal defects.

HYPOTHESIS

The use of an acellular polyurethane scaffold for new tissue generation in irreparable partial meniscal defects provides both pain relief and improved functionality.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Fifty-two patients with irreparable partial meniscal defects (34 medial and 18 lateral, 88% with 1-3 previous surgeries on the index meniscus) were implanted with a polyurethane scaffold in a prospective, single-arm, multicenter, proof-of-principle study. Safety was assessed by the rate of scaffold-related serious adverse events (SAEs) and the International Cartilage Repair Society articular cartilage scoring system comparing magnetic resonance imaging (MRI) at 24 months to MRI at baseline (1 week). Kaplan-Meier time to treatment failure distributions were performed. Clinical outcomes were measured comparing visual analog scale, International Knee Documentation Committee, Knee Injury and Osteoarthritis Outcome Score (KOOS), and Lysholm scores at 24 months from baseline (entry into study).

RESULTS

Clinically and statistically significant improvements (P < .0001) compared with baseline were reported in all clinical outcome scores (baseline/24 months): visual analog scale (45.7/20.3), International Knee Documentation Committee (45.4/70.1), KOOS symptoms (64.6/78.3), KOOS pain (57.5/78.6), KOOS activities of daily living (68.8/84.2), KOOS sports (30.5/59.0), KOOS quality of life (33.9/56.6), and Lysholm (60.1/80.7), demonstrating improvements in both pain and function. The incidence of treatment failure was 9 (17.3%) patients, of which 3 patients (8.8%) had medial meniscal defects and 6 patients (33.3%) had lateral meniscal defects. There were 9 SAEs requiring reoperation. Stable or improved International Cartilage Repair Society cartilage grades were observed in 92.5% of patients between baseline and 24 months.

CONCLUSION

At 2 years after implantation, safety and clinical outcome data from this study support the use of the polyurethane scaffold for the treatment of irreparable, painful, partial meniscal defects.

Tissue ingrowth after implantation of a novel, biodegradable polyurethane scaffold for treatment of partial meniscal lesions

BACKGROUND

A novel, biodegradable, aliphatic polyurethane scaffold was designed to fulfill an unmet clinical need in the treatment of patients with irreparable partial meniscal lesions.

HYPOTHESIS

Treatment of irreparable partial meniscal lesions with an acellular polyurethane scaffold supports new tissue ingrowth.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Fifty-two patients (with 34 medial and 18 lateral lesions) were recruited into a prospective, single-arm, multicenter, proof-of-principle study and treated with the polyurethane scaffold. The scaffold was implanted after partial meniscectomy using standard surgeon-preferred techniques for suturing. Tissue ingrowth was assessed at 3 months by dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and at 12 months by gross examination during second-look arthroscopy, in the course of which a biopsy sample from the inner free edge of the scaffold meniscus was taken for qualitative histologic analysis.

RESULTS

Tissue ingrowth at 3 months was demonstrated on DCE-MRI in 35 of 43 (81.4%) patients. All but one 12-month second-look (43 of 44 [97.7%]) showed integration of the scaffold with the native meniscus and all biopsy specimens (44) showed fully vital material, with no signs of cell death or necrosis. Three distinct layers were observed based on morphologic structure, vessel structure presence or absence, and extracellular matrix composition.

CONCLUSION

The DCE-MRI demonstrated successful early tissue ingrowth into the scaffold. The biopsy findings demonstrated the biocompatibility of the scaffold and ingrowth of tissue with particular histologic characteristics suggestive of meniscus-like tissue. In conclusion, these data show for the first time consistent regeneration of tissue when using an acellular polyurethane scaffold to treat irreparable partial meniscus tissue lesions.

Multilayered silk scaffolds for meniscus tissue engineering

Removal of injured/damaged meniscus, a vital fibrocartilaginous load-bearing tissue, impairs normal knee function and predisposes patients to osteoarthritis. Meniscus tissue engineering solution is one option to improve outcomes and relieve pain. In an attempt to fabricate knee meniscus grafts three layered wedge shaped silk meniscal scaffold system was engineered to mimic native meniscus architecture. The scaffolds were seeded with human fibroblasts (outside) and chondrocytes (inside) in a spatial separated mode similar to native tissue, in order to generate meniscus-like tissue in vitro. In chondrogenic culture in the presence of TGF-b3, cell-seeded constructs increased in cellularity and extracellular matrix (ECM) content. Histology and Immunohistochemistry confirmed maintenance of chondrocytic phenotype with higher levels of sulfated glycosaminoglycans (sGAG) and collagen types I and II. Improved scaffold mechanical properties along with ECM alignment with time in culture suggest this multiporous silk construct as a useful micro-patterned template for directed tissue growth with respect to form and function of meniscus-like tissue.