Patient Information - Foot

Cartiva SCI is a medical device that is intended to improve pain and function in patients with osteoarthritic joints. The most common site in the foot is at the base of the big toe. This joint, called the metatarsophalangeal, or MTP joint is subjected to a great deal of stress and bending with each of the thousands of steps we take each day. This condition is also known as hallux rigidus and is a chronic and incurable condition.

Because osteoarthritis is a progressive condition, motion becomes increasingly limited, making walking or even standing difficult and painful. With limited motion, the big toe will not propel the body forward and other joints of the body will need to compensate, putting more strain through the rest of the foot and lower extremity. Over time, the decrease in motion will lend to jamming of the joint. As the joint undergoes constant trauma in this way, the bone becomes stimulated and extra bone growth known as bone spurs occur over the top of the joint worsening the condition.

Hallux rigidus usually develops in adults between the ages of 30 and 60 years. While the true cause of hallux rigidus is unknown, risk factors include family history, prior injury to the toe that damages the articular cartilage, and differences in foot anatomy that increase stress on the joint.

Articular cartilage is the smooth, white tissue that lines the bony surface of joints such as the knees, toes, ankles and elbows. Its function is to provide a low friction surface enabling the joint to withstand weight bearing through the range of motion needed to perform activities of daily living as well as athletic endeavours. Those daily activities include walking, stair climbing and work-related activities. In other words, articular cartilage is a very thin shock absorber.

Articular cartilage injuries can occur as a result of athletic activity, traumatic injury or daily wear and tear. Unlike bone and other connective tissue types, articular cartilage has no direct blood supply, thus it has little or no ability to repair or regenerate itself. Left untreated, cartilage damage can progressively worsen and lead to chronic conditions such as osteoarthritis. Injured, inflamed or damaged cartilage can cause symptoms such as stiffness, decreased range of motion, joint pain and swelling.

Symptoms

  • Pain in the joint when you are active, especially as you push-off on the toes when you walk
  • Swelling around the joint
  • A bump, like a bunion or callus that develops on the top of the foot
  • Stiffness in the great toe and an inability to bend it up or down

Existing Treatment

When damage to the joint is severe, arthrodesis, or fusion, is the Gold standard of care. In this procedure, the damaged cartilage is removed and pins, screws or a plate are used to fix the joint in a permanent position. Gradually, the bones grow together.

The main advantage of this procedure is that it is a permanent correction with elimination of the arthritis and pain. The major disadvantage is the restriction of movement of the big toe and the resulting limitations on certain daily and sport activities. You may also have difficulty wearing a shoe with a heel higher than one inch.

CARTIVA SCI

Cartiva Synthetic Cartilage Implant (SCI) is a revolutionary implant that is designed to replace the damaged cartilage surface. Cartiva SCI is made from polyvinyl alcohol (PVA), a material that has been used in a number of medical device applications for more than 20 years. Through a proprietary manufacturing process, Cartiva SCI is designed to mimic the properties of natural cartilage. Cartiva SCI has been approved for use in Europe, Canada, Turkey and Brazil since 2002. Over 3,000 implants have been used to date.

Property Articular Cartilage Cartiva SCI
Water Content 60-80% 60%
Compressive Modulus 0.3-0.8 MPa 2.5-3.2 MPa
Coefficient of Friction <0.01-0.05 0.04-0.07

Cartiva® SCI is an organic polymer-based biomaterial comprised of 40% polyvinyl alchohol (PVA). PVA is a synthetic polymer derived from polyvinyl acetate through partial or full hydroxylation. Depending on the degree of polymerization and hydrolysis, the physical characteristics, chemical properties and mechanical properties can be customized to define functional requirements. The properties of PVA can be further modified by crosslinking, a process whereby individual polymer chains are connected to yield a tough and physically stable matrix. Crosslinking of PVA produces a material that is inert, viscoelastic and lubricious attractive properties for medical device applications. A crosslinked PVA matrix is no longer water soluble, but can be swollen to produce a hydrogel, a gel where the swelling agent is water. PVA hydrogels and membranes have been developed for biomedical applications such as contact lenses, artificial pancreases, hemodialysis and synthetic vitreous humor. It is an attractive material for these applications because of its biocompatibility and low protein adsorption properties resulting in low cell adhesion compared with other hydrogels. PVA’s properties also make it a good biomaterial for simulating natural tissues inside the body, such as cartilage replacement. Cartilage, typically comprised of 60-80% water with a mass balance primarily of collagen, is the prototypical, biologic hydrogel.

With a high water content similar to surrounding healthy cartilage and its elastic and compressive mechanical properties, the physical properties of Cartiva SCI make it an excellent replacement for damaged articular cartilage. The material has been shown to resist compression and shear with exceptional wear characteristics. Stringent control of the PVA composition and a proprietary manufacturing process results in compressive properties (aggregate modulus and creep) and wear resistance similar to native cartilage. The manufacturing process results in a viscoelastic implant engineered to withstand the repetitive loading associated with the physiologic conditions of the knee and the first metatarsophalangeal joint.

The finished device is cylindrical in shape and is for use during a single surgical procedure, where its placement allows for addressing focal articular defects. Due to the similar osmotic, physical, and frictional properties of Cartiva SCI to native cartilage, joint resurfacing repairs using this implant does not require replacement of the opposing articular surface. Consequently, joint resurfacing with Cartiva SCI is simple, does not require significant removal of healthy tissue or its replacement with a durable bearing surface, and thus typically results in nominal surgical trauma and rapid recovery.

Cartiva Feature Benefit
Synthetic No risk of viral bacterial transmission associated with human or animal derived materials
Biocompatible Composed of saline and an organic polymer.
No systemic irritation in 10+ years of clinical use
Biostable Does not degrade
Durable Mechanical and physical properties similar to native cartilage.
Capable of withstanding repetitive loading typical of MTP, knee, talus and other joints
Compliant Suppleness and flexibility allows for ease of handling and implantation
Slippery Low coefficient of friction aids joint articulation and mobility

 

Surgery

During a simple outpatient procedure lasting approximately 25 minutes, your surgeon exposes the MTP joint by making a small, 4-5cm incision. After removing any bone spurs, the damaged cartilage on the metatarsal head is removed and replaced with a press-fitted Cartiva SCI implant to provide a smooth, load-bearing joint surface.

Unlike a fusion procedure, you may begin weight bearing immediately as tolerated. Likewise, range of motion exercises should begin immediately to avoid stiffness. Many patients achieve relief from their arthritis symptoms immediately after the procedure, but normal soft tissue pain or discomfort may persist beyond 4-10 weeks as the wounds heal after surgery.