The results of our study demonstrate that 17.9% of patients develop deep vein thrombosis after knee arthroscopy (most being either proximal or extensive). It is reasonable to perform a randomized trial to determine whether the incidence of deep vein thrombosis can be safely reduced in patients undergoing knee arthroscopy.

Anterior cruciate ligament (ACL) injuries occur at an annual rate of 120 000 in the USA, and many need reconstructive surgery. We report successful results at 1-13 months following implantation of bioengineered ACL (bACL) in goats. A bACL has been developed using autologous ACL cells, a collagen matrix and bone plugs. The extremities of the bACL were fully integrated into the femur and tibia of the host. Vascularisation of the grafts was extensive 1 month post-surgery and improved with time. At 6 months postgrafting, histological and ultrastructural observations demonstrated a highly organised ligamentous structure, rich in type I collagen fibres and fibroblasts. At the implants' insertion sites, characteristic fibrocartilage was observed having well aligned chondrocytes and collagen fibrils. After a year, mechanical rupture of the grafts demonstrated a major gain in strength. Eventual applications of this new technology in humans include multiple uses in orthopaedic, dental and reconstructive surgeries.

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The anterior cruciate ligament (ACL) is often the target of knee trauma. This ligament does not heal very well, leading to joint instability. Long-term instability of the knee can lead to early arthritis and loss of function. To develop efficient strategies to stimulate posttraumatic ACL regeneration in vivo, a good healing model is needed in vitro. Such a model must remain as simple as possible, but should include key features to provide relevant answers to precise questions about the clinical problem addressed. Here, we report tissue-engineered type I collagen scaffolds developed to establish an ACL healing model in vitro and a potential ACL substitute in vivo. Such scaffolds were used to evaluate ACL cell growth, migration, and the capacity to synthesize and assemble collagen fibers for up to 40 days in vitro and up to 180 days in vivo. They were anchored with two bone plugs to allow their static stretching in culture and to facilitate their surgical implantation in knee joints. Our results have shown that living ACL fibroblasts can attach, migrate, and colonize this type of scaffold. In vitro, the cells populated the scaffolds and expressed mRNAs coding for the prolyl-4-hydroxylase, involved in collagen fibers' assembly. In vivo, acellular implants were vascularized and populated with caprine cells that migrated from the osseous insertions toward the center of the grafts. This model is a very good tool to study ACL repair and identify the factors that could accelerate its healing postsurgery.

Fibroblasts isolated from skin and from anterior cruciate ligament (ACL) secrete type I and type III collagens in vivo and in vitro. However, it is much easier and practical to obtain a small skin biopsy than an ACL sample to isolate fibroblasts for tissue engineering applications. Various tissue engineering strategies have been proposed for torn ACL replacement. We report here the results of the implantation of bioengineered ACLs (bACLs), reconstructed in vitro using a type I collagen scaffold, anchored with two porous bone plugs to allow bone-ligament-bone surgical engraftment. The bACLs were seeded with autologous living dermal fibroblasts, and grafted for 6 months in goat knee joints. Histological and ultrastructural observations ex vivo demonstrated a highly organized ligamentous structure, rich in type I collagen fibers and cells. Grafts' vascularization and innervation were observed in all bACLs that were entirely reconstructed in vitro. Organized Sharpey's fibers and fibrocartilage, including chondrocytes, were present at the osseous insertion sites of the grafts. They showed remodeling and matrix synthesis postimplantation. Our tissue engineering approach may eventually provide a new solution to replace torn ACL in humans.

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The anterior cruciate ligament (ACL) of the knee joint is one of the strongest ligaments of the body and is often the target of traumatic injuries. Unfortunately, its healing potential is limited, and the surgical options for its replacement are frequently associated with clinical issues. A bioengineered ACL (bACL) was developed using a collagen matrix, seeded with autologous cells and successfully grafted and integrated into goat knee joints. We hypothesize that, in order to reduce the cost and simplify the model, an acellular bACL can be used as a substitute for a torn ACL, and bone plugs can be replaced by endobuttons to fix the bACL in situ. First, acellular bACLs were successfully grafted in the goat model with 18% recovery of ultimate tensile strength 6 months after implantation (94 N/mm2 vs. 520). Second, a bACL with endobuttons was produced and tested in an exvivo bovine knee model. The natural collagen scaffold of the bACL contributes to supporting host cell migration, growth and differentiation in situ post-implantation. Bone plugs were replaced by endobuttons to design a second generation of bACLs that offer more versatility as biocompatible grafts for torn ACL replacement in humans. A robust collagen bACL will allow solving therapeutic issues currently encountered by orthopedic surgeons such as donor-site morbidity, graft failure and post-traumatic osteoarthritis.