Hyaluronic acid
Sodium hyaluronate has been found present in the synovial fluid of all species studied. In humans it is also found in other soft connective tissues such as skin, umbilical cord, and vitreous humour as well as being present in lung, kidney, brain, and muscle tissues. Scientific understanding of the underlying properties of sodium hyaluronate started in 1934, when it was isolated from bovine vitreous humour Since the 1950s, the litterature concerning the potential therapeutic use of sodium hyaluronate in humans has grown.
The viscoelastic properties of synovial fluid in the joint are known to due to its sodium hyaluronate content. Changes in the lubricating properties of synovial fluid, lead to significant pain and loss of function.
In pathological conditions, due to acute and chronic inflammation, the synovial fluid no longer exhibits its normal rheological properties that protect the synovial tissue and cartilage from mechanical stress.
The concentration and molecular size of sodium hyaluronate decreases in the synovial fluid, and consequently there is decreased viscosity and elasticity of the fluid. Within the normal adult knee, there is approximately 2 mL of synovial fluid with a sodium hyaluronate concentration of 2.5 to 4.0 mg/mL and molecular weight of 5 to 7 × 106 Da.
The concept of Visco supplementation, using externally administered sodium hyaluronate, arose from increased understanding of the importance of sodium hyaluronate to the normal rheological properties of synovial fluid. In the earliest studies employing this approach clinically, the main objective was to increase the sodium hyaluronate concentration above that of the pathological state
In studies, sodium hyaluronate used for medical purposes has been extracted from a variety of sources, such as umbilical cord, rooster comb or bacterial cultures and then purified and separated from any pyrogenic, inflammatory, immunogenic or chemotactic fractions.
Visco supplementation with sodium hyaluronate entered clinical use in Japan and Italy in 1987, in Canada in 1992, in Europe in 1995, and in the United States in 1997. It is now a widely used approach for the treatment of a variety of joint conditions, particularly osteoarthritis.
Numerous Visco supplementation formulations of sodium hyaluronate are commercially available in the EU. Synvet-50 is intended to be injected intra-articularly. Hyaluronate molecules are long chains which form a filter matrix interspersed with normal cellular fluids to supplement the visco-elastic properties of joint fluid.
The vial/syringe is intended for single use. The contents of the vial must be used immediately once the container has been opened. The injection solution containing 20mg/mL sodium hyaluronate.
Synvet-50 is to be used as Visco supplementation in adults, for the indication “pain and restricted mobility in degenerative and traumatic changes of the knee joint and other synovial joints”. The device will have temporary contact with articular tissue upon injection into the joint space.
As with any intra-articular procedure, proper injection site disinfection should be performed, and care should be taken not to scratch the cartilage surface with the injection needle.
