Thumb Arthritis (Basal)

What is it?

The joint at the base of the thumb is between a small bone called ‘Trapezium’ and the first bone of the thumb, called the ‘metacarpal’. The mobility of our thumb gives us the ability to oppose the thumb and bring it across the palm towards the little finger. This is an evolutionary progression from apes in whom the thumb is less mobile and is like a finger. As the design of our thumb joint allows for swivel and pivoting motions it is one of the most mobile joints and so very prone to be affected by arthritis with normal use. In osteoarthritis, the cartilage which allows bones to glide smoothly wears out and the smooth surfaces roughen. The bones rub against one another resulting in pain.

What is the cause?

Osteoarthritis is related to age. Osteoarthritis of the thumb is three times more common in women and becomes symptomatic around the age of 50. The condition frequently develops on both sides. The condition is also associated with previous thumb fractures and in patients who have joint laxity.

What are the symptoms and how is the condition diagnosed?

Symptoms and signs are variable and depend on the severity of the condition. Arthritis at the base of the thumb will cause pain on activities that load this joint the most. These activities will involve gripping, grasping, pinching an object between the thumb and forefinger or applying any force. (i.e. unscrewing jars, turning a key in a lock, peeling vegetables).

With time the thumb will become deformed and the base of the thumb will become prominent (see picture below). The area will be tender and the patient may notice a gritty sensation. Due to pain the soft tissues around the joint will contract, thumb span will become reduced and the thumb may eventually become fixed in a position in front of the palm (thumb in palm deformity). Secondary deformities may develop in the thumb joint which is further away from the trapezio-metacarpal joint.

Prominence at the base of the thumb

Will further tests or investigations be needed?

An x-ray is advised to confirm and stage the arthritis

First metacarpal and Trezium

What is the treatment?

Treatment depends on the stage or extent of the arthritis, such as the thumb deformity, age and functional demands of the patient.

  1. Activity modification and splints worn with activities that aggravate the symptoms may be useful. Splints will limit thumb movement and give the thumb some rest. Pain killers will help to relieve discomfort.
  2. A local injection of steroid may relieve symptoms. The injection very occasionally cause some thinning or colour change of the skin at the site. Improvement is variable and can be temporary. My preference is to inject the affected joint under x-ray control.
  3. Surgery is indicated if the above measures fail. Various surgical options can be considered depending on stage of the arthritis, age of the patient, functional demands, quality of bone stock and thumb deformity.
    1. Trapeziumectomy (with or without ligament reconstruction): This is the most common procedure advised. This procedure involves complete removal of the trapezium bone which is one of the eight carpal bones in the wrist. It is the procedure of choice, especially when both sides of the trapezium are arthritic. After excising the bone the base of the thumb may appear slack and I may harvest a part of a tendon from the forearm to create a ligament to stabilize the joint. This creation of a new ligament is not always needed. Because a bone is taken out from the base of the thumb, and a gap left, it is possible that the thumb may shorten and result in weaker grip and reduced dexterity.
    2. Joint replacement: A replacement of the trapeziometacarpal joint can also be considered. New designs, concepts and material have stimulated interest in the joint replacement of the basal thumb joint. These type of joint replacements are still evolving and short to medium term results are encouraging. Two types of joint replacements can be considered. First, a hemiarthroplasty in which only one side of the joint is replaced (usually the base of the metcarpal). Second, a total joint replacement in which both sides of the joint are replaced with a hydroxyapatite coated ball and socket joint replacement. The advantage of this procedure is that the length of the thumb is maintained as no bone is excised.
    3. Joint Fusion: In unusual cases fusion or arthrodesis of the joint can be considered. This is usually reserved for young patients who have developed post-traumatic arthritis in the joint and need a stable thumb for high power manual work. The fused joint can bear load without pain but has no flexibility

My standard procedure is to perform trapeziumectomy. I may supplement it with a ligament reconstruction depending on stage or grade of the condition. I will also consider performing a total joint replacement and have performed about 30 such total joint replacements. My indications for a total joint replacement are very specific and I will discuss the rationale of these with the patient.

This patient had the trapezium bone excised on the left and the joint replaced on the right.
This patient had the trapezium bone excised on the left and the joint replaced on the right.

All the procedures described above are carried out under regional or general anaesthesia. After the operation your hand will be protected in a bulky supportive cotton-wool dressing which includes a plaster slab. The wound is checked at about 10-12 days and the supportive dressing is converted to a lighter splint. Hand therapy is initiated and you should expect to wear the splint for 4-6 weeks. After removal of the splint, hand therapy for progressive mobilization and strengthening exercises is advised for 6 weeks.

What happens if it is not treated?

It is likely that over a number of years the arthritis will burn out and the pain will become manageable. However it is most likely that contractures will develop around the joint causing the thumb to draw into the palm. Later the next joint further out from the thumb will stretch out and bend backwards resulting in a Z-shaped thumb.

What is the success of surgical treatment?

All the above operations are successful in achieving the primary aim of providing effective pain relief and I would expect that to be the outcome in more than 95% of cases. 

After the trapeziumectomy operation, the thumb may shorten in the long term. This is unlikely to affect function or grip in relatively old patients but may be of some concern to patients who have had excision of the trapezium at a relatively younger age. This problem can be addressed by a total joint replacement. However in the long term, joint replacements will fail in which case the replacement will have to be removed.

What are the complications of surgical treatment?

  1. The surgical scar may be tender for 6-8 weeks. However it is seldom troublesome in the longer term.
  2. Infection of the wound is possible and in the early stage can be successfully treated with antibiotics. If pain increases after surgery infection needs to be ruled out.
  3. Stiffness of the finger joints is possible and hence the need to exercise them soon after surgery.
  4. Severe complex regional pain syndrome (CRPS) is a rare but serious complication after hand surgery. Unfortunately it is not possible to predict this problem but needs to be monitored and treated (usually with physiotherapy) if it develops.   
  5. If patients have had a joint replacement then it is possible for the joint replacement to dislocate. In the long term joint replacement will become loose and fail.
  6. Any surgical intervention has the risk of developing complications that are unpredicted. These complications may have the potential to leave the patient worse than before surgery.

Is there anything I can do to improve outcome?

After surgery keep the hand up so as to help reduce swelling. I would advise against wearing rings on the operated hand for 6 weeks following surgery. Start exercising your fingers immediately after surgery (Make a fist, and then stretch your fingers out). This will help avoid finger swelling and stiffness.

Keep the wound and dressing dry. The scar can be massaged regularly with a soft non-perfumed cream for a couple of months. Hand therapy instructions should be followed. 

When can I do various activities?

  1. Return to work depends on many factors including the nature of the job and hand dominance. Generally patients can return to a desk job within 3 weeks if they are happy to use the splint and work and perform reasonable tasks with the hand. Manual work should be avoided for 6-12 weeks depending on the procedure performed.
  2. Driving should be possible within 4-6 weeks of the operation. This will depend on which thumb has been operated on and whether the car to be used is an automatic or manual.
  3. Certain activities should be avoided in the long term i.e. weight bearing on the thumb / wrist or holding a dog lead with the thumb which has had the joint replaced.