What is rhizarthrosis?
Osteoarthritis is wear and tear of the cartilage, which may be related to the aging process, or may appear after a fracture. Rhizarthrosis is the name given to a specific location of osteoarthritis at the base of the thumb, between the1st metacarpal and the trapezium bone.
Pain is most often the first symptom. It is felt at the base of the thumb and occurs particularly when the thumb is pinched by the index finger. Certain gestures are particularly problematic: buttoning a shirt, turning a key in a door, opening a bottle. A lack of strength is common. As osteoarthritis progresses, progressive stiffening of the thumb can occur, and even deformation, which in extreme cases gives the thumb a Z-shape.
What tests are required?
X-rays are the diagnostic test of choice. Other imaging tests are generally unnecessary, except in special situations.
What treatments are available for Rhizarthrosis?
In all cases, the first stage of treatment is non-surgical.
Wearing a removable splint to stabilize the thumb and limit movement of the affected joint can alleviate pain. Some models are designed to be worn during the day, others at night.
Cortisone infiltration into the joint is performed during the consultation, and can provide temporary relief (weeks, months, even years).
Occupational therapy sessions can help alleviate pain by modifying the way certain movements are performed and strengthening thumb muscles.
Surgery is considered only after non-surgical treatment has failed.
The procedure is performed under local anaesthetic. At the end of the operation, with the arm still asleep, it is not possible to drive home.
The technique chosen depends on a number of factors, such as the extent of osteoarthritis, the patient’s age and profession, and the surgeon’s habits.
The trapezium bone is removed to avoid contact with the base of the first metacarpal. This gesture eliminates any conflict. A cast must then be worn for a month. Convalescence is relatively lengthy, requiring several months to restore pain-free mobility and strength.
The aim is to fuse the worn joint. This eliminates pain at the cost of partial loss of thumb mobility. A cast is often required for four to six weeks.
The joint can be replaced by a prosthesis, as is done for the hip or knee. Recovery is faster than with trapezectomy, since immobilization is short (less than two weeks) and mobility recovers more quickly. Sometimes, parts of the prosthesis become worn over the years and need to be replaced.
Whichever treatment is used, a check-up is carried out after surgery, and the dressing is re-dressed after a few days. Use of the thumb is limited, as pinching is forbidden for at least a month. The length of time off work depends on the profession and the surgical technique used, but usually ranges from one to three months. Sports activities involving the use of the operated hand should be suspended for around three months. Occupational therapy sessions are often necessary.
What are the possible complications?
Common to all surgeries
Infection of the wound may occur, but is usually cured by local care and the prescription of antibiotics. Surgical drainage is rare.
Hematoma corresponds to an accumulation of blood under the skin. It’s not a problem if it’s small, but if it’s larger, surgical evacuation may be necessary.
Healing problems (delayed healing, thick scars) occur more frequently in patients who smoke.
Inadvertent injury to an artery, nerve, ligament or tendon is always possible, although rare. These structures can be repaired, but recovery may be prolonged or even incomplete.
Chronic regional pain syndrome is a disproportionate inflammatory reaction of the body following surgery. It causes pain, swelling and stiffness, requiring treatment that can last several months.
Complications specific to rhizarthrosis
In the case of trapezectomy, there is a risk of conflict between the base of the thumb metacarpal and the scaphoid or trapezoid bone, which can cause pain.
In the case of arthrodesis, there is a risk of non-union (pseudarthrosis), necessitating a new operation.
In the case of prostheses, there is a risk of dislocation or displacement of the prosthesis, which may require a second operation. Wear and tear of the prosthesis occurs over the years, but the usual lifespan is estimated at around ten years.