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Typical examples of synovium histology of the implant group. a) Haematoxylin eosin (HE) stained section showing macrophages (white arrow) and a giant cell (#) containing brown debris and two fibrous fragment cross-sections with a diameter of approximately 20 μm (*) surrounded by a giant cell. b) Acid phosphatase section showing weak positive staining of the fiber-surrounding giant cell (black arrow). c) Perl’s Prussian blue section, which is positive at the location of the brown debris visible in a) and b). d) Polarized light HE section showing birefringent fragments in the occasional macrophages and giant cells.
Source publication
Purpose:
Since the treatment options for symptomatic total meniscectomy patients are still limited, an anatomically shaped, polycarbonate urethane (PCU), total meniscus replacement was developed. This study evaluates the in vivo performance of the implant in a goat model, with a specific focus on the implant location in the joint, geometrical inte...
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Objective
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Purpose
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Methods...
Purpose
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Citations
... Potential host tissue fusion Failure in orthopedics [73] Poly(vinyl alcohol) Biocompatibility Non-toxicity Non-carcinogenicity Easy forming ability Easy manufacturing capability Low protein adsorption [74,75] Polyethylene oxide Limited cytotoxicity Fast degradation [76] promote ECM deposition, and accelerate mechanical improvement. Multiple attempts have been made to reproduce the anisotropy of the natural meniscus using synthesis methods like weaving [77], electrospinning [78], and 3D printing [79]. ...
... Additionally, the PCU implant did not exhibit any additional material loss from the 3-month study (A. C. Vrancken et al., 2015), attributed to the nonlinear compressive creep behaviour of the material. A. C. T. Vrancken et al. (2017) hypothesise that the maximum compression of the posterior horn was reached upon 3 months. ...
... An initial study of PCU meniscal implants (Figure 3 (c)) in a goat model were investigated by A. C. Vrancken et al. (2015). However, this implant failed mechanically when the suture came apart in the goat knees during the threemonth implantation period. ...
... Earlier studies have shown promising results when using PCU as FKRI or meniscus replacement in 3 and 6 months in vivo animal studies, respectively. [11][12][13] The clinical success of osteochondral implants depends significantly on the properties of the artificial bearing material, including surface chemistry and roughness. 7 Limiting friction between the implant and the opposing cartilage prevents wear, deformation, and damage to both the implant and the cartilage. ...
The clinical success of osteochondral implants depends significantly on their surface properties. In vivo, an implant may roughen over time which can decrease its performance. The present study investigates whether changes in the surface texture of metal and two types of polycarbonate urethane (PCU) focal knee resurfacing implants (FKRIs) occurred after 6 and 12 months of in vivo articulation with native goat cartilage. PCU implants which differed in stem stiffness were compared to investigate whether the stem fixating the implant in the bone influences surface topography. Using optical profilometry, 19 surface texture parameters were evaluated, including spatial distribution and functional parameters obtained from the material ratio curve. For metal implants, wear during in vivo articulation occurred mainly via material removal, as shown by the significant decrease of the core‐valley transition from 91.5% in unused implants to 90% and 89.6% after 6 and 12 months, respectively. Conversely, for PCU implants, the wear mechanism consisted in either filling of the valleys or flattening of the surface by dulling of sharp peaks. This was illustrated in the change in roughness skewness from negative to positive values over 12 months of in vivo articulation. Implants with a softer stem experienced the most deformation, shown by the largest change in material ratio curve parameters. We therefore showed, using a detailed surface profilometry analysis, that the surface texture of metal and two different PCU FKRIs changes in a different way after articulation against cartilage, revealing distinct wear mechanisms of different implant materials.
... Compressive mechanical tests showed that scaffolds with higher porosity displayed lower mechanical strength, based on the calculated compressive modulus value obtained from the stress-strain curve in Fig. 2B. The mechanical property of scaffolds with 25% porosity (0.25 mm diameter in average) was very close to that of the goat meniscus, which has been reported to be close to human meniscus [2,44]. ...
Background
The poor regenerative capability and structural complexity make the reconstruction of meniscus particularly challenging in clinic. 3D printing of polymer scaffolds holds the promise of precisely constructing complex tissue architecture, however the resultant scaffolds usually lack of sufficient bioactivity to effectively generate new tissue.
Results
Herein, 3D printing-based strategy via the cryo-printing technology was employed to fabricate customized polyurethane (PU) porous scaffolds that mimic native meniscus. In order to enhance scaffold bioactivity for human mesenchymal stem cells (hMSCs) culture, scaffold surface modification through the physical absorption of collagen I and fibronectin (FN) were investigated by cell live/dead staining and cell viability assays. The results indicated that coating with fibronectin outperformed coating with collagen I in promoting multiple-aspect stem cell functions, and fibronectin favors long-term culture required for chondrogenesis on scaffolds. In situ chondrogenic differentiation of hMSCs resulted in a time-dependent upregulation of SOX9 and extracellular matrix (ECM) assessed by qRT-PCR analysis, and enhanced deposition of collagen II and aggrecan confirmed by immunostaining and western blot analysis. Gene expression data also revealed 3D porous scaffolds coupled with surface functionalization greatly facilitated chondrogenesis of hMSCs. In addition, the subcutaneous implantation of 3D porous PU scaffolds on SD rats did not induce local inflammation and integrated well with surrounding tissues, suggesting good in vivo biocompatibility.
Conclusions
Overall, this study presents an approach to fabricate biocompatible meniscus constructs that not only recapitulate the architecture and mechanical property of native meniscus, but also have desired bioactivity for hMSCs culture and cartilage regeneration. The generated 3D meniscus-mimicking scaffolds incorporated with hMSCs offer great promise in tissue engineering strategies for meniscus regeneration.
Graphical Abstract
... Total meniscus replacements currently in development have used sutures for fixation in large animal models. Sutures connected to the anterior and posterior horns of the implant were passed through transosseous tunnels in the tibia and tied distally with a knot or endobutton™ [4,16,37,38]. However, in vivo data reported implant extrusion and fixation ruptures with such fixation systems. ...
Purpose
Meniscal surgery is one of the most common orthopaedic surgical interventions. Total meniscus replacements have been proposed as a solution for patients with irreparable meniscal injuries. Reliable fixation is crucial for the success and functionality of such implants. The aim of this study was to characterise an interference screw fixation system developed for a novel fibre-matrix-reinforced synthetic total meniscus replacement in an ovine cadaveric model.
Methods
Textile straps were tested in tension to failure ( n = 15) and in cyclic tension (70–220 N) for 1000 cycles ( n = 5). The textile strap-interference screw fixation system was tested in 4.5 mm-diameter single anterior and double posterior tunnels in North of England Mule ovine tibias aged > 2 years using titanium alloy (Ti6Al4Va) and polyether-ether-ketone (PEEK) screws ( n ≥ 5). Straps were preconditioned, dynamically loaded for 1000 cycles in tension (70–220 N), the fixation slippage under cyclic loading was measured, and then pulled to failure.
Results
Strap stiffness was at least 12 times that recorded for human meniscal roots. Strap creep strain at the maximum load (220 N) was 0.005 following 1000 cycles. For all tunnels, pull-out failure resulted from textile strap slippage or bone fracture rather than strap rupture, which demonstrated that the textile strap was comparatively stronger than the interference screw fixation system. Pull-out load (anterior 544 ± 119 N; posterior 889 ± 157 N) was comparable to human meniscal root strength. Fixation slippage was within the acceptable range for anterior cruciate ligament graft reconstruction (anterior 1.9 ± 0.7 mm; posterior 1.9 ± 0.5 mm).
Conclusion
These findings show that the textile attachment-interference screw fixation system provides reliable fixation for a novel ovine meniscus implant, supporting progression to in vivo testing. This research provides a baseline for future development of novel human meniscus replacements, in relation to attachment design and fixation methods. The data suggest that surgical techniques familiar from ligament reconstruction may be used for the fixation of clinical meniscal prostheses.
... Another synthetic polymer that should be addressed is polycarbonate urethane (PCU). PCU is a flexible, biocompatible, biostable and wear-resistant material that can be incorporated in 3D-printed, porous structural scaffolds (Williams et al., 2015;Abar et al., 2020). In addition, as a hydrophilic material, PCU can mimic the lubrication mechanism in native synovial joints (Wan et al., 2020). ...
Knee menisci are structurally complex components that preserve appropriate biomechanics of the knee. Meniscal tissue is susceptible to injury and cannot heal spontaneously from most pathologies, especially considering the limited regenerative capacity of the inner avascular region. Conventional clinical treatments span from conservative therapy to meniscus implantation, all with limitations. There have been advances in meniscal tissue engineering and regenerative medicine in terms of potential combinations of polymeric biomaterials, endogenous cells and stimuli, resulting in innovative strategies. Recently, polymeric scaffolds have provided researchers with a powerful instrument to rationally support the requirements for meniscal tissue regeneration, ranging from an ideal architecture to biocompatibility and bioactivity. However, multiple challenges involving the anisotropic structure, sophisticated regenerative process, and challenging healing environment of the meniscus still create barriers to clinical application. Advances in scaffold manufacturing technology, temporal regulation of molecular signaling and investigation of host immunoresponses to scaffolds in tissue engineering provide alternative strategies, and studies have shed light on this field. Accordingly, this review aims to summarize the current polymers used to fabricate meniscal scaffolds and their applications in vivo and in vitro to evaluate their potential utility in meniscal tissue engineering. Recent progress on combinations of two or more types of polymers is described, with a focus on advanced strategies associated with technologies and immune compatibility and tunability. Finally, we discuss the current challenges and future prospects for regenerating injured meniscal tissues.
... Recently, studies have shown that a synthetic artificial meniscal implant could overcome the constraints associated with the use of meniscal allografts (Vrancken et al. 2013;Zur 2011). The mechanical factors that influence the performance of the meniscal implants include the size and shape of the implant (Donahue et al. 2004;Vrancken 2014;Shriram et al. 2019a;Vrancken et al. 2015;Sommerlath et al. 1992), material properties (Sommerlath et al. 1992;Meakin et al. 2003;Linder-Ganz et al. 2010;Shriram et al. 2017) fit and fixation type (Vaquero and Forriol 2016;Alhalki et al. 1999;Paletta et al. 1997), and implant placement (Sekaran et al. 2002;Wajsfisz et al. 2013). The biomechanical effects that these implant parameters may have on the knee joint need to be evaluated comprehensively before implementation in the clinical setting. ...
... The biomechanical effects that these implant parameters may have on the knee joint need to be evaluated comprehensively before implementation in the clinical setting. The influence of implant geometry, material properties, and fit and fixation type on the knee joint biomechanics have been reported in several studies (Vaquero and Forriol 2016;Donahue et al. 2004;Vrancken 2014;Shriram et al. 2019aShriram et al. , 2017Vrancken et al. 2015;Sommerlath et al. 1992;Meakin et al. 2003;Linder-Ganz et al. 2010;Alhalki et al. 1999;Paletta et al. 1997). Predicated on these studies, it has been determined that an anatomical shaped polycarbonate urethane (PCU) meniscal implant with a stiffness of 11 MPa and with extensions for horn attachments recuperates the normal functioning of the knee joint. ...
... Predicated on these studies, it has been determined that an anatomical shaped polycarbonate urethane (PCU) meniscal implant with a stiffness of 11 MPa and with extensions for horn attachments recuperates the normal functioning of the knee joint. While the significance of geometry and other structural properties of the meniscal implant on the knee joint biomechanics have been discussed in detail (Donahue et al. 2004;Shriram et al. 2019aShriram et al. , 2017Vrancken et al. 2015;Sommerlath et al. 1992;Meakin et al. 2003;Alhalki et al. 1999), no studies in the literature have reported the significance of the anatomical meniscal implant placement on the knee joint biomechanics. ...
Non-anatomical placement may occur during the surgical implantation of the meniscal implant, and its influence on the resulting biomechanics of the knee joint has not been systematically studied. The purpose of this study was to evaluate the biomechanical effects of non-anatomical placement of the meniscal implant on the knee joint during a complete walking cycle. Three-dimensional finite element (FE) analyses of the knee joint were performed, based on the model developed from magnetic resonance images and the loading conditions derived from the gait pattern of a healthy male subject, for the following physiological conditions: (i) knee joint with intact native meniscus, (ii) medial meniscectomized knee joint, (iii) knee joint with anatomically placed meniscal implant, and (iv) knee joint with the meniscal implant placed in four different in vitro determined non-anatomical locations. While the native menisci were modeled using the nonlinear hyperelastic Holzapfel-Gasser-Ogden (HGO) constitutive model, the meniscal implant was modeled using the isotropic hyperelastic neo-Hookean model. Placement of the meniscal implant in the non-anatomical lateral-posterior and lateral-anterior locations significantly increased the peak contact pressure in the medial compartment. Placement of the meniscal implant in non-anatomical locations significantly altered the tibial rotational kinematics and increased the total force acting at the meniscal horns. Results suggest that placement of the meniscal implant in non-anatomical locations may restrain its ability to be chondroprotective and may initiate or accelerate cartilage degeneration. In conclusion, clinicians should endeavor to place the implant as closest as possible to the anatomical location to restore the normal knee biomechanics.
... Cushion form bearings based on polycarbonate-urethane (PCU) mimic the natural synovial joint more closely by promoting fluid-film lubrication (Elsner et al., 2010). PCU has superior biostability and a higher resistance to hydrolysis, environmental stress cracking and oxidative stability, and has been investigated as a bearing material in orthopaedic prostheses (Elsner & McKeon, 2017;Elsner et al., 2011;Vrancken et al., 2015;Zur et al., 2011). The wear rate of PCU against CoCr alloy is much lower than that of conventional UHMWPE and at least 24% lower than that of HXLPE (St. ...
Basic theory and principles of engineering tribology are outlined, with particular reference to artificial joints, in Section 2.1. Important concepts relating to bearing surfaces, contact mechanics, friction, lubrication and wear are reviewed in this section. A comprehensive summary and discussion then follows for both theoretical (Section 2.2) and experimental (Section 2.3) tribological studies of artificial joints, including hip implants with different bearing surfaces such as a polyethylene cup (conventional and cross-linked) against a metallic or ceramic head, metal-on-metal and ceramic-on-ceramic material combinations, as well as other novel combinations, including ceramic-on-metal and ceramic-on-polyetheretherketone (PEEK). Knee implants are included. Issues of tribology in artificial joints are also discussed, together with a summary and section on future developments in Section 2.4. Section 2.5 contains where to find further information on this topic.
... The relative success of an implant to achieve long-term durability is provided with three significant factors in combination: geometry (anatomically shaped without remodeling and shrinkage), material properties (especially compressive properties; elasticity, anisotropy, inhomogeneity, lubrication), and attachments (material properties, geometry, insertion sites). Among these determining factors behind the relative success of a meniscal replacement, the material properties of the meniscus tissue are of importance (Donahue et al. 2003;Vrancken et al. 2015;Shriram et al. 2017;Makris et al. 2011). As such, a quantitative understanding of the meniscus mechanics has been of interest in important medical applications such as tissue engineering or computational modeling of the whole knee joint. ...
... In particular, finding a suitable menisci replacement has been the subject of the previous studies extensively. As yet, the only practical treatment for clinical use is the allograft implantation (with well-known limitations, e.g., size matching and availability) (Vrancken et al. 2015;Chambers and El-Amin 2015). To offer an alternative for meniscal allograft, several synthetic and natural materials have been served in tissue engineering aiming at finding a long-term meniscal scaffold (Chambers and El-Amin 2015;Murphy et al. 2018). ...
... As an evolving field for meniscal replacements, numerous investigations have been performed to develop an ideal prosthesis for mimicking the native tissue behavior. Although none have been completely able to preserve the functional integrity of the biologic meniscus tissue, the consequences confirmed promising mechanical improvements associated with polycarbonate urethane (PCU) and polyvinyl alcohol hydrogel (PVA-H) implants (Vrancken et al. 2015;Shemesh et al. 2014;Kobayashi et al. 2005). The significant advantage of this class of replacements is its computer-aided designing and manufacturing procedures which involve an accurate patient-specific 3D geometry of the meniscus to mimic anatomical criteria. ...
Menisci are fibrocartilaginous disks consisting of soft tissue with a complex biomechanical structure. They are critical determinants of the kinematics as well as the stability of the knee joint. Several studies have been carried out to formulate tissue mechanical behavior, leading to the development of a wide spectrum of constitutive laws. In addition to developing analytical tools, extensive numerical studies have been conducted on menisci modeling. This study reviews the developments of the most widely used continuum models of the meniscus mechanical properties in conjunction with emerging analytical and numerical models used to study the meniscus. The review presents relevant approaches and assumptions used to develop the models and includes discussions regarding strengths, weaknesses, and discrepancies involved in the presented models. The study presents a comprehensive coverage of relevant publications included in Compendex, EMBASE, MEDLINE, PubMed, ScienceDirect, Springer, and Scopus databases. This review aims at opening novel avenues for improving menisci modeling within the framework of constitutive modeling through highlighting the needs for further research directed toward determining key factors in gaining insight into the biomechanics of menisci which is crucial for the elaborate design of meniscal replacements.
... The meniscus prosthesis consists of a stiff core embedded in a soft flexible (polymer) body. Based on cadaveric and animal experiments, proper materials for the meniscus prosthesis were selected [19][20][21]. The composite structure of the meniscus prosthesis allows for flexible articulations, while simultaneously constraining excessive prosthesis deformation. ...
... The prosthesis polymeric horns can pivot around metallic posts to minimize torque loads to the prosthesis horns [22]. Several studies have been performed to improve the geometry, material properties, and fixation technique of the meniscus prosthesis [17][18][19][20][21]23]. ...
Despite all the efforts to optimize the meniscus prosthesis system (geometry, material, and fixation type), the success of the prosthesis in clinical practice will depend on surgical factors such as intra-operative positioning of the prosthesis. In this study, the aim was therefore to assess the implications of positional changes of the medial meniscus prosthesis for knee biomechanics. A detailed validated finite element (FE) model of human intact and meniscal implanted knees was developed based on a series of in vitro experiments. Different non-anatomical prosthesis positions were applied in the FE model, and the biomechanical response during the gait stance phase compared with an anatomically positioned prosthesis, as well as meniscectomized and also the intact knee model. The results showed that an anatomical positioning of the medial meniscus prosthesis could better recover the intact knee biomechanics, while a non-anatomical positioning of the prosthesis to a limited extent alters the knee kinematics and articular contact pressure and increases the implantation failure risk. The outcomes indicate that a medial or anterior positioning of the meniscus prosthesis may be more forgiving than a posteriorly or laterally positioned prosthesis. The outcome of this study may provide a better insight into the possible consequences of meniscus prosthesis positioning errors for the patient and the prosthesis functionality.
Graphical abstract
