1 – Why do I need a prosthesis?
- Rhizarthrosis is osteoarthritis of the thumb root, destroying the trapeziometacarpal joint (and sometimes the overlying scaphotrapezotrapezoid joint).
This junction at the base of the thumb is the key joint for orienting the thumb towards the other fingers, facilitating the pinching gesture and ensuring gripping ability.
- Rhizarthrosis leads to painful sensations, reduced power and, ultimately, (usually permanent) deformation of the thumb structure. Although mildly annoying at first, it gradually becomes more limiting, and steadily progresses towards deterioration over the years, leading to increasing stiffness and deformity of the thumb: the gap between thumb and index finger narrows, and gripping ability becomes complicated.
- In the early stages of the disease, there are options other than surgery for moderately developed forms: rigid orthoses to be worn at night or semi-flexible orthoses to be worn during the day, corticosteroid or hyaluronic acid injections. These methods offer temporary pain relief, but only delay the need for surgery, as osteoarthritis continues to progress.
- If these medical approaches are unsuccessful, or in the presence of significant thumb deformity, surgery becomes unavoidable.
- Complementary examinations: a simple X-ray is usually sufficient. In some cases, a CT scan may be useful.
2 – The intervention process
- Anaesthesia: In most cases, local anaesthesia is used for the hand and forearm.
- Technical procedure: A 3 cm incision is made at the base of the thumb. The arthritic deformity of the joint is removed, followed by implantation of a modular prosthesis comprising 3 elements (impacted, screwed or cemented). This prosthesis comprises a cup in the trapezium bone, a stem in the first metacarpal and an intermediate element called the “head-neck”, whose variable size enables the tension of the surrounding ligaments and tendons to be adjusted.
- Circumstances that can disrupt the operation: In the event of unforeseen and unexpected situations, such as the discovery of non-sterile instruments or partially available surgical implants at the start of the operation, your surgeon may decide to interrupt the procedure and not continue with the operation, even after anesthesia.
Incidents during surgery: It is possible to injure a sensory nerve (radial nerve) or an artery (radial artery), but this does not usually lead to serious problems. Fractures of the first metacarpal and particularly the trapezium may occur during implant insertion, especially if the bone is weakened by osteoporosis. This complication, which cannot be predicted, may require the surgeon to modify his or her surgical approach, as it may not always be possible to use the prosthesis originally planned.
3 – Follow-up and expected results :
- Normal recovery periods: After a two- to four-week period of immobilization of the wrist and thumb, the hand can regain normal use for everyday movements.
The operation is effective, eliminating pain and restoring the ability to pinch the thumb without discomfort. The expected lifespan of these prostheses is around 15 years.
Wear and tear of the prosthesis, and its eventual detachment, are more likely to occur early if the thumb is subjected to intense mechanical stress.
- Longer-term complications of the procedure:
- The risks inherent in any surgical procedure include the development of algodystrophy (hand enlargement, increased temperature, pain and limited finger mobility) and infection.
- Nerve damage with hypersensitive scarring and sometimes temporary loss of sensation on the dorsal surface of the thumb and index finger may occur.
- Secondary tendonitis (de Quervain’s type) may occur.
- Dislocation or misalignment of the prosthesis may occur, especially in the first few months, sometimes necessitating further surgery.
- Stiffness of the prosthesis due to ossification is rare.
- Incomplete correction of thumb deformity may be observed in cases of long-standing rhizarthrosis.
- Implants may sink in when the bone is particularly fragile, as in the case of osteoporosis.
- An allergic reaction to the metal of the prosthesis may exceptionally occur, causing pain and reddish scarring: it is important to report any previous reaction to costume jewelry, which may necessitate the use of nickel-free prostheses.
4 – Your intervention in practice :
- Preparation : no specific preparation required.
- Hospitalization: The procedure is performed on an outpatient basis or may require a one-day hospital stay.
- Returning home:A splint is used to immobilize the wrist and thumb for three weeks. Thereafter, the operated hand can be reused for activities such as eating, writing and driving. However, it is advisable to wait until the end of the second month before resuming activities requiring strength.
- Avoid: Avoid resuming activities involving vibration for at least two months.
