Usefulness of Probing Sensor Device for Evaluating Meniscal Suture and Scaffold Implantation.

Appropriate suture tension is a key factor in successful meniscal repair. This study aimed to clarify the appropriate value of meniscal stabilization with suture repair based on a probing procedure for healthy porcine menisci and a novel meniscal scaffold. After evaluating the reliability of the probing sensor, meniscal vertical tear and partial meniscectomy models were developed, in which suture repair and meniscal scaffold implantation were performed at suture intervals ranging between 20 and 2.5 mm. The residence forces at each interval were evaluated using a probing sensor. Moreover, a tensile test was conducted to evaluate the displacement and presence or absence of gaps. We found that normal and meniscal scaffolds should be fixed within 5 mm of suture interval. The probing residence forces required were at least 1.0 N for vertical tears and 3.0 N for meniscal scaffolds. These findings may be taken into consideration to reduce suture failure following meniscal tear repair and stabilizing meniscal scaffold fixation.

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.

Biomechanical assessment of a novel meniscal scaffold compared to partial meniscectomy: A study on porcine meniscal injury.

This study aimed to investigate the appropriate size of scaffold implantation on stress distribution and evaluate its mechanical and biomechanical properties considering hydrolysis. The meniscus acts as a load distribution in the knee, and its biomechanical properties are essential for the development of the PGA scaffold. We established a novel meniscal scaffold, which consists of polyglycolic acid (PGA) covered with L-lactide-ε-caprolactone copolymer (P[LA/CL]). After 4 weeks of hydrolysis, the scaffold had a 7% volume reduction compared to the initial volume. In biomechanical tests, the implantation of scaffolds 20% larger than the circumferential and vertical defect size results in greater contact stress than the intact meniscus. In the mechanical evaluation associated with the decomposition behavior, the strength decreased after 4 weeks of hydrolysis. Meanwhile, in the biomechanical test considering hydrolysis, contact stress and area equivalent to intact were obtained after 4 weeks of hydrolysis. In conclusion, the implantation of the PGA scaffold might be a useful alternative to partial meniscectomy in terms of mechanical properties, and the PGA scaffold should be implanted up to 20% of the defect size.

Implantation of Novel Meniscus Scaffold for Irreparable Meniscal Tear.

Partial meniscectomy, which is generally used for the treatment of meniscal tears, can lead to knee joint osteoarthritis. To prevent this important complication, attempting to restore normal knee joint kinematics and biomechanical forces after partial meniscectomy is essential. Implantation of a meniscal scaffold can be useful in this regard, improving the function of the meniscus on knee joint biomechanics after partial meniscectomy. Use of meniscal scaffolds would have specific clinical merit for young patients who are at highest for developing knee joint osteoarthritis over time. Herein, we describe our novel bioabsorbable meniscal scaffold, fabricated with polyglycolic acid coated with polylactic acid/caprolactone, used after partial meniscectomy for degenerative and irreparable meniscal tears. The method of implantation of the scaffold will have a determinant effect on clinical outcomes. As the implementation technique by arthroscopy will be influenced by the stiffness and strength of the scaffold implant used, we provide a detailed description of our implantation technique, including a description of the pitfalls to consider in order to improve clinical outcomes.

Development of a Pressure-Sensitive Conductive Rubber Sensor for Analyzing Meniscal Injury in Porcine Models.

The assessment of the distribution of contact pressure on the meniscus is important in the elucidation of kinematics, etiology of joint diseases, and establishment of treatment methods. Compared with sensors widely used in recent years, pressure-sensitive conductive rubber sensors are easy to mold, flexible, durable, and resistant to shearing forces. This study is aimed at developing a rubber sensor for meniscal research and evaluating the pressure distribution after meniscal injury using porcine models. After confirming the reliability of the rubber sensor, contact pressure was obtained from the rubber sensor using the medial meniscus and femur of the porcine knee. Three test conditions of intact meniscus, radial tear, and meniscectomy were prepared, and a compressive load of 100 N was applied. After confirming the high reliability of the rubber sensor, the intact meniscus had the most uniform pressure distribution map, while the pressure in the meniscectomy model was concentrated in the resection region. The high-pressure region was significantly smaller in the intact group than in the radial tear models after 80 and 100 N (P < 0.05). The rubber sensor captured the pressure concentration specific to each examination group and was useful for evaluating the relationship between the pattern of meniscal injury and changes in the biomechanical condition of the knee.

Development of a novel meniscal sheet scaffold and its effectiveness for meniscal regeneration in a rabbit defect model.

This study evaluated the biomechanical strength of a novel two-layer meniscal sheet scaffold (MSS) consisting of polyglycolic acid and poly-Llactic acid/caprolactone and investigated meniscal healing using wrapping treatment for meniscal defect model in a rabbit. The ultimate failure load of the MSS was determined using a tensile testing machine, in vitro. A 2-mm cylindrical defects were created at the medial meniscus of rabbit knees (n = 40). Each knee was assigned to one of two groups. The defect group was not treated and the MSS group underwent wrapping treatment with MSS. Menisci were harvested at 2, 4, 8, and 12 weeks post-implantation. The regenerated meniscus and defect size were evaluated using macrophotographs. Ishida scores for regenerated tissue were determined using Safranin-O/Fast Green staining. Immunohistochemical analysis of Ki-67 for cell proliferation, anti-type I and II collagen antibodies for structure of the regenerated tissue was elucidated. Medial femoral cartilage was stained with Safranin-O/Fast Green and evaluated with Osteoarthritis Research Society International (OARSI) scores. The strength of MSS was maintained over 90% from initial time point to 4 weeks after hydrolysis and over 60% of the strength remained at 8 weeks. The surface area of the meniscus was larger and the defect size smaller in the MSS group than in the defect group at 8 and 12 weeks. Ishida scores revealed that the MSS group improved significantly compared to that of the defect group at all postsurgery time points evaluated. Ki-67 positive cell ratio was significantly higher in the MSS group. OARSI score of the defect group was significantly higher and the defect group showed progressive degeneration in the articular cartilage from 8 to 12 weeks. Overall, wrapping meniscus defects with MSS was useful for accelerating meniscal healing from an early stage and beneficial for tissue regeneration and promoting extracellular matrix maturation.

Histological Analysis of the Wrapping Treatment for Meniscal Horizontal Tears in Rabbits.

OBJECTIVE: To investigate meniscal regeneration and prevent cartilage degeneration using wrapping treatment for meniscal horizontal tears that have been difficult to repair in rabbits. DESIGN: Thirty knees from 15 Japanese white rabbits were divided into the horizontal (horizontal tears) or wrapping (horizontal tears with wrapping treatment) groups. Horizontal tears were created and wrapped with a sheet scaffold containing polyglycolic acid, polylactic acid, and polycaprolactone. The meniscus was stained with Safranin-O/Fast Green and evaluated with modified Pauli scores at 8, 12, and 16 weeks after implantation (n = 5). Cell morphology was determined with hematoxylin and eosin staining. Mature collagen was confirmed with Picrosirius Red staining. Furthermore, immunohistochemical analysis of inducible nitric oxide synthase (iNOS) for inflammation, Ki-67 for proliferation, and type II collagen for regeneration was performed. Medial femoral cartilage was stained with Safranin-O/Fast Green and evaluated with the Osteoarthritis Research Society International score at 8 and 16 weeks. RESULTS: The wrapping group had significantly better regeneration than the horizontal group, especially at 16 weeks (P < 0.05). Wrapping treatment induced fibrochondrocyte-like cells at 16 weeks. After wrapping treatment, iNOS was overexpressed at 8 weeks, Ki-67 at 8 and 12 weeks, and type II collagen at 16 weeks. Cartilage degeneration in the wrapping group did not progress significantly compared with that in the horizontal group at 16 weeks (P < 0.05). CONCLUSIONS: Wrapping treatment for meniscal horizontal tears induced meniscal regeneration as the sheet scaffold might induce intrinsic and extrinsic repair. Regaining the meniscal function by the wrapping treatment prevented cartilage degeneration.

Evaluation of Meniscal Regeneration in a Mini Pig Model Treated With a Novel Polyglycolic Acid Meniscal Scaffold.

BACKGROUND: Meniscal injury is a severe impediment to movement and results in accelerated deterioration of the knee joint. PURPOSE: To evaluate the effect of a novel meniscal scaffold prepared from polyglycolic acid coated with polylactic acid/caprolactone on the treatment of meniscal injury in a mini pig model. STUDY DESIGN: Controlled laboratory study. METHODS: The model was established with a 10-mm resection at the anterior medial meniscus on both knee joints. A scaffold was implanted in the right knee joint. The meniscal scaffold was inserted and sutured next to the native meniscus. The histological analysis was performed to determine meniscal regeneration with safranin O staining, cell proliferation with PCNA, inflammation with TNF, and collagen structure and production with picrosirius red and immunofluorescence. Cartilage degeneration was evaluated with Safranin O. Meniscal regeneration and joint fluid were evaluated with magnetic resonance imaging. RESULTS: Although compressive stress and elastic modulus were significantly lower in the scaffold than in the native porcine menisci, ultimate tensile stress was similar. Implanted scaffolds were covered with tissue beginning at 4 weeks, with increased migration of proliferating cells to the implant area at 4 and 8 weeks. Scaffolds were absorbed with freshly produced collagen at 24 weeks. Cartilage degeneration was significantly lower in the meniscus-implanted group than in the meniscectomy group. Magnetic resonance imaging results did not show severe accumulation of joint fluids, suggesting negligible inflammation. Density of the implanted menisci was comparable with that of the native menisci. CONCLUSION: Meniscal scaffold prepared from polyglycolic acid has therapeutic potential for meniscal regeneration. CLINICAL RELEVANCE: This meniscal scaffold can improve biological knee reconstruction and prevent the increase of total knee arthroplasty.