Interventional procedure overview of synthetic cartilage implant insertion for first metatarsophalangeal joint osteoarthritis (hallux rigidus)

Indications and current treatment

Osteoarthritis is a common condition in which the surface of the joint becomes worn and the adjacent bone thickens and forms osteophytes. It can affect the metatarsophalangeal (MTP) joint at the base of the big toe, which may become painful and stiff (hallux rigidus).

Conservative treatments include exercise, physiotherapy, orthotics, analgesics, non-steroidal anti-inflammatory tablets and cream, and steroid injections into the joint. Severe first MTP joint osteoarthritis that does not respond to conservative measures may need surgery. If an osteophyte on the surface of the joint is the only problem, it can be trimmed (cheilectomy). The main surgical options for treating the whole joint are fusion, osteotomy, joint replacement or rarely excision arthroplasty.

What the procedure involves

Synthetic cartilage implant insertion for first MTP joint osteoarthritis (hallux rigidus) is usually done under general or regional anaesthesia. A moulded cylindrical implant made of polyvinyl alcohol (a soft plastic-like substance) and saline is used with specifically designed single-use instruments. A small incision is made over the top of the big toe joint and a drill is used to remove enough bone to make an appropriately-sized hole for the implant. The implant is then placed into the hole in the bone and left slightly raised, providing a smooth and slippery surface in the area of the cartilage defect. Once the implant is in place, the incision is closed with sutures. Weight bearing can typically resume immediately after the procedure. The aim is to reduce pain and improve the toe's range of motion.

Outcome measures

Foot and Ankle Ability Measure

The Foot and Ankle Ability Measure (FAAM) is a validated outcome measure with 29 items made up of sports and activity of daily living (ADL) subscores. Responses are scored from 4 to 0 ranging from 'No difficulty at all' to 'Unable to do'. Patients may also respond 'Not applicable' if an activity in question is limited by something other than their foot or ankle. The score total ranges from 0 to 84 for the ADL subscale and 0 to 32 for the sports subscale, which is converted to a percentage score. Higher scores represent higher levels of function with 100% representing no dysfunction. The reported minimal clinically important difference is 9 points for the sports score and 8 points for the ADL score.

Manchester Oxford Foot/Ankle Questionnaire

The Manchester Oxford Foot/Ankle Questionnaire (MOXFQ) is a validated measure of health-related quality of life. It has 3 domains: pain, walking or standing, and social interaction, with a maximum score of 100 in each domain. Higher scores signify poorer quality of life.