Osteoarthritis of the base of the thumb or rhizarthrosis

doctor checking out someone's hand

Dr. Grégoire Chick

Hand surgery Genolier Clinic, Genolier

August 6, 2022

So what’s rhizarthrosis? It’s a type of arthritis that affects the thumb or rather a trapeziometacarpal joint of the hand. This condition also mainly affects women. It’s 20 times more likely for this to occur to elderly women. One of the main symptoms is constant pain at the base of your thumb, swellness, difficulty while using your thumb, and more. There are no specific treatments for osteoarthritis of the base of the thumb, however, there are surgeries that can be performed to help the issue. 

Want to learn more? Keep reading the article by Dr. Grégoire Chick.

Rhizarthrosis is a very common, often well-tolerated condition that affects 20% of women. It corresponds to chronic wear of the cartilage covering the trapezium and the first metacarpal at the base of the thumb.

The multiple clinical and radiological presentations of this degenerative condition illustrate the complexity of the trapeziometacarpal joint. It is a key joint in the thumb column, which allows the thumb to be oriented in opposition to the other fingers (pollici-digital pincer) for fine gripping movements. This joint is closed by a joint capsule whose reinforcements constitute the ligaments which ensure its stability with the neighbouring muscles. Rhizarthrosis is the prerogative of women aged between 50 and 60 years old, and is most often found on both sides of the joint, at different clinical and radiological stages. It is an essential osteoarthritis (unknown cause). Rarely, osteoarthritis is the consequence of a fracture, rheumatism or infection. Pain is most often the first symptom, either spontaneously or in certain everyday gestures using the pollici-digital forceps such as turning a key, peeling fruit or opening a jar. The lack of strength is revealed when picking up large objects. The evolution is by painful attacks, over a period of 7 to 10 years, leading to a progressive deformation of the thumb. The end result is a closure of the first commissure (space between thumb and index finger), with a deformation of the thumb column into an M shape (thumb adductus). The pain fades and is replaced by stiffness.

The assessment is based on specific radiographic incidences, which allow the clinical diagnosis to be confirmed, the extent of joint destruction to be assessed, a certain amount of bone volume to be preserved and a search for arthrosic damage to neighbouring joints (peri-trapezial arthrosis). Inflammatory flare-ups are either very painful and precipitate the need for treatment, or they are perfectly tolerated until the patient complains of difficulty in grasping large objects.

INITIALLY, THE TREATMENT IS ALWAYS MEDICAL FULFILLING 2 OBJECTIVES:

To reduce pain and preserve joint range. It combines rest, anti-inflammatory medication, analgesic physiotherapy and a custom-made thermoformed splint that keeps the thumb in a spread position when worn at night. This allows normal use of the thumb during the day, if necessary facilitated by a functional soft orthosis. Corticosteroid infiltration may help to overcome the hyperalgesic inflammatory period. Repeated use of corticosteroids may alter the capsulo-ligamentary system, which will complicate a possible surgical procedure.

When medical treatment of sufficient duration (6 months to 1 year) becomes insufficient to relieve pain (10% of patients), or when closure of the first commissure or deformation of the thumb column occurs, surgical treatment can be considered. It aims to resolve a triple demand: indolence, mobility and strength.

In the early stages of osteoarthritis, the joint can be preserved either by stabilising it (ligamentoplasty), reorienting the joint surfaces (osteotomy), or removing the nerves to the joint (denervation). At the stage of more advanced osteoarthritis, 2 main types of intervention are proposed. The choice will depend on age, professional activity (hard work), the extent of joint destruction, the size of the trapezium, the damage to neighbouring joints and the surgeon’s habits.

● Trapeziectomy consists of removing the diseased bone (trapezium). To stabilise the thumb and maintain the height of the thumb column, a neighbouring tendon is interposed (ligamentoplasty).

● The trapezium-metacarpal prosthesis resembles a mini hip prosthesis, with a spherical metal head that articulates in a polyethylene or metal trapezium cup. The fixation of the prosthetic parts in the bone uses either bone regeneration (unsealed prostheses) or cement (sealed prostheses).

The results of these two types of operation are good in terms of pain and mobility. Strength is often reduced in trapezectomies and the thumb column is often shortened with a long period of indolence (6 months). Prostheses require a limitation of force activity to avoid mechanical complications. With recent models, the life span of the implants is 12 to 15 years. This does not cut off the bridges to a trapezectomy in case of failure.

The trapezium-metacarpal arthrodesis (definitive blocking of the joint) must remain an occasional indication given the difficulties of adjustment, the long immobilisation (2 to 3 months) with a bone fusion difficult to obtain.

Even if the surgical treatment of rhizarthrosis is controversial in the literature, the results prove that surgery is effective for the main symptoms with complications that remain rare. It is necessary to bear in mind that the results are less good if surgery is proposed too late. The management of rheumatoid arthritis requires optimal coordination between the various players (general practitioners, internists, rheumatologists, physiotherapists, occupational therapists and hand surgeons).

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