Novel nano-composite multilayered biomaterial for the treatment of patellofemoral cartilage lesions.

The treatment of patellofemoral articular cartilage lesions remains challenging. Aside from their inherent limited capacity to heal and their articular location, the complexity of the patellofemoral joint proves to be refractory to treatment, even though recent research has reported different treatments that give satisfactory results. The pathogenesis of patellar damage is complex and multifactorial, and a single procedure is often not enough to solve the problem. Therefore, the first step of any treatment option must be a complete and deep understanding of the causative factors that must be recognized and addressed to obtain synmptoms resolution and healing of cartilage lesions. In fact, all associated abnormalities should be treated before considering cartilage tissue damage. Small articular cartilage changes such as chondromalacia usually depend on unrecognized malalignment syndromes, and patellar realignment without regard for cartilage damage whose treatment may be sufficient to relieve symptoms. Articular cartilage abnormalities may consist of swelling and softening, and deep fissures can often be present and extend through the full thickness of the cartilage. In more severe cases the tissue may have a jelly-like consistency, and in some cases almost the entire articular surgace may have degenerated. When the cartilage defect is severe, the treatment of the etiopathogenetic factors may not be sufficient and must be combined with the cartilage damage treatment in order to obtain a satisfactory clinical outcome. Various therapeutic modalities have been used in clinical practice. Arthroscopic shaving has been proposted as a minimally invasive procedure, easy and not followes by prolonged morbidity. Shaving can be used when lesion is a circumscribed blistger and when there is articular fasciculation. In these disorders, the procedure most likely should be confined to the restoration of gross articular smoothness. Debridement consistign of excision and drilling may have some use in treating osteoarthritis, and improvement can be expected in approximately two thirds of the patients. Moreover, it may also be an alternative to shaving in the knees with basal chondromalacia. Cartilage repair, although unpredictable, does sometimes occur, and can be promoted by early motion. These methods can be used for superficial defect, but for a deeper lesion expanding to bone, deep excision through the subchondral bone is carried out with concurrent bevelling of the margin of the defect. However, this method cannot be considered an ideal solution, considering the contradictory results observed in the literature and the worsening at long-term follow-up. In cases of very extensive and deep alterations of the patellar surface, total patellectomy has also been performed. While the symptoms related to the lesion in the chondral surface were abolished, the shortcomings of this procedrue are obvious: habitual lateral gliding of the quadriceps tenedon and insufficiency of the extension mechanism due to a lack of patellar leverage. Other approaches include the insertion of periostium flaps into the debrided defects and the use of synovial tissue flaps for covering the entire articular surface of the patella. More recently, other surgical solutions have been proposed aiming to preserve a more physiologic cartilaginous superficial layer. Mosaicplasty consist of the reconstruction of the chondral defect using small, cylindrical autologous osteochondral grafts taken from non-weight-bearing areas of the joint. This technique presents several advantages: a single procedure, low cost, press-fit fixation by compressed grafts, and host bone impaction. However, despite these positive aspects, the clinical experience showed lower results with respect to femoral and tibial grafts; this may be due to the higher concentration of shear stress in this location. Regenerative techniques, such as autologous chondrocyte implantation (ACI), have emerged as a potential therapeutic option. Some studies suggest the durability of this treatment, especially at long-term follow-up, because of its ability to produce hyaline-like cartilage that is mechanically and functionally stable, and the alowance for integration with the adjacent articular surface. This approach, introduced in 1994 by Brittberg and Peterson, seems to offer good results, even with patellar lesions shown to have a less predictable outcome with lower satisfactory results compared to the treatment of femoral defects. The use of classic ACI has been associated with several limitations related to the complexity and the morbidity of the surgical procedure. This technique requires a large joint exposure and implies a higher risk of joint stiffness and arthrofibrosis; there is a frequent occurrence of periosteal hypertrophy, that occurs between 3 and 7 months after surgery in 10-25% of cases and often requires revision surgery. Some authors have shown a reoperation rate of up to 42%, due to joint stiffness, and have indicated that the use of the periosteal flap increases the risk of complications during the recovery period and produces more difficult rehabilitation. Other problems can be observed with standard ACI methods. These include the difficulty in handling a delicate liquid suspension of chondrocytes at implantation surgery, the need to make a hermetic periosteum seal using sutures, and the concerns related to the manteinance of the condrogenic phenotype in the liquid suspension. The development of the second-generation ACI, that used a tissue engineering technology to create a cartilage-like tissue in a three-dimensional culture system, allows one to address most of the concerns related to the cell culture and the surgical technique. Numerous biodegradable polymers such as hyaluronan, collagen, fibrin glue, alginate, agarose, and various synthetic polymers were developed and used as temporary scaffolds for the in vitro growth of living cells and their subsequent transplantation onto the defect site. Promising results have been obtained with this tissue engineering approach and nowadays matrix-assisted autologous chondrocyte transplantation is widely used in Europe. The results obtained are still controversial and there is no agreement about the effective superiority of this procedure to others. Moreover, despite the good potential reported, patellar lesions still present lower clinical outcome with respect to other location, and there is a worsening of the results over time even at medium term follow-up. This approach is also plagued by high cost and the need for a two-step surgery. To overcome all these problems, we developed and applied in clinical practice a new bi-composite, multilayer, biomimetic scaffold, which can mimic the osteocartilaginous anatomical structure in all of its components. This scaffold allows for the restoration of the articular surface in a one-step surgery without the need for cells and, thanks to the plasticity of the graft, even big osteochondral lesions can be treated through minor incisions.