What is thumb base arthritis?

Arthritis (joint inflammation) at the base of the thumb (CMC joint) is a very common condition. Studies of X-rays have shown that over 70% of ladies over the age of 75 will suffer from this. This does not mean they will all have symptoms but there will be X-ray changes. Men are less often affected. The typical symptoms are of gradually increasing pain, stiffness and deformity centred at the base of the thumb. Occasionally will start quite suddenly, particularly following a fall.  That will not have caused the arthritis per se but will have made the underlying arthritis symptomatic in a way that it was not before.  Patients are usually most troubled by the pain. The stiffness typically comes on gradually without much functional limitation and most patients do not complain of it. The pain may radiate to the middle joint of the thumb and in some cases that is the prime site of pain which can be confusing in making the diagnosis. The pain causes limitations in day to day activities especially pinching smaller objects when both pain and reduced strength can cause considerable problems. Often gripping larger objects is less troublesome. Some patients are woken at night by pain but this is fortunately infrequent. Although the symptoms start on one side most patients have symptoms on both sides often to very similar degrees.

Why does it occur?

The pathology i.e. the abnormality is wear of the cartilage lining of the joint at the base of the thumb. The joint is shaped like the saddle used for horse riding. Thus it is very dependent upon its alignment. In middle age and beyond the ligaments stabilising the base of the thumb seems to fail and one bone slides on the other bone, leading to incongruence and abnormal wear. This is a gradual process occurring over decades although the symptoms themselves may present more quickly.  Arthritis itself simply refers to inflammation of a joint.  Once the cartilage lining of the joint wears enough there will be bone rubbing on bone. This is not, of necessity, painful but can be with use, particularly heavy use such as strong pinch. The pain is probably related to some inflammation in the joint hence the term “arthritis” meaning joint inflammation. The local bones will try to adapt to these changes often producing a little more bone at the margins and there may be some further slippage of one bone on the other, giving an abnormal contour to the base of the thumb.  It does not particularly seem to be more common in association with heavy work other than as opposed to light work. There appear to be no other linked factors and it is not particularly linked with any other forms of wear and tear arthritis in the body.

What happens if nothing is done?

(This is referred to as the natural history i.e. what happens if Nature runs its own course.) In most people there is a gradual increase in symptoms initially but in time they adapt either by doing less, changing job/retiring or using various devices to help and often reach a tolerable steady state. They are not completely free of pain but generally are not too trouble and elect to have nothing done. Many other people’s symptoms gradually increase and eventually require treatment. The key is treating the patient’s symptoms rather than being lead too strongly by their X-ray changes.

Making the diagnosis

The Hand specialist who sees the patient will ask questions about their symptoms, when they started, how they progressed, what treatment (if any) they have had and other questions relevant to the problems. They will then examine the patient looking at the wrists and hands and in particular the thumbs. Stressing i.e. pushing on the affected joint is usually painful. It is necessary to demonstrate some tenderness to confirm the site of the symptoms but this should not be too painful.

What test(s) might be performed?

Tests (also known medically as Investigations) include X-rays, scans, blood tests and particularly in the hand electrical tests (known as EMGs or Neurophysiology). These may be used to help make or confirm a diagnosis after a patient has described their symptoms and been examined.

In thumb base arthritis the diagnosis is usually obvious after listening to and examining a patient. Other causes of pain in that area are wrist arthritis, De Quervain’s tenovaginitis and radial nerve entrapment or injury.

Most Hand specialists will order an X-ray to demonstrate the bone and joint changes and guide treatment. Nonetheless the X-ray changes do not correlate well with patient’s symptoms. Thus they may have little change on X-ray but a lot of pain and vice versa.


What are the non-operative treatments?

Treatment should start with non-operative options. Patients will be given advice about activity modifications, i.e. reducing heavy or repetitive pinch.  Examples include using a fatter pen to reduce the pinch pressure and using the opposite thumb for some activities, where possible.  Pain-killers can help, particularly anti-inflammatory pain-killers, such as Ibuprofen or Diclofenac.  These can be administered as gels or taken orally, provided there is no history of indigestion. Sometimes splints are used but in our experience if they are large enough to be helpful they tend to be too cumbersome to be practical for day to day use.  If this is insufficient then a steroid injection would usually be recommended. An injection is given of a long-acting steroid, such as Depomedrone or Triamcinolone, with some local anaesthetic into the joint at the bottom of the thumb.  The body naturally produces steroids to help dampen down inflammation. This appears to be one of the actions at this site.  Success cannot be guaranteed but in 70-80% of patients there is some significant benefit.  How long this lasts is unpredictable.  Some people only have a few weeks or months of benefit.  Others may have years or even life-long benefit such that they do not require further treatment, although may still have some mild on-going symptoms.  If one injection provides only short term benefit then it may well be repeated.  Patients often ask how many injections can be given.  There is no set rule about this. Typically, however, a second injection will work a little less well than the first (although this is not inevitable).  By the time three injections have been given, if this is over a shortish period, i.e. less than 1 year, then it is unlikely the third injection will be successful and most surgeons would recommend an alternative approach.  If, however, injections are only required infrequently, perhaps once every 2-3 years, then having a fourth or fifth injection would, in themselves, be a lot safer than having an operation, and if they give benefit this is reasonable.  There are risks. The biggest risk is of failure. There are risks of some pain for a few days, although that is usually minimised by taking pain-killers, starting while the area is still numb from the local anaesthetic.  In theory there is a risk of infection, but this seems very rare and has not occurred in our Practice in over 10 years.  The main other risk is some thinning of the skin. This can present with some pallor and a little less bulk at the site and occasionally an increased tendency to bleeding if the area is knocked.  This is not common with this injection but is common with some other injections.  If it does occur then that is a relative contra-indication to further injections, i.e. the patient’s surgeon would probably decide not to go ahead with further injections because of the risks of further local damage.

What does the operation involve?

If the non-operative means fails then surgery would be recommended. The most common and well established operation is called a trapezectomy or trapeziumectomy. The small bone at the near end of the joint (bottom of the thumb is removed leaving a scar joint). The aim of the operation is to alleviate pain and, thus, improve function, including pinch strength. The operation also aims to maintain and, hopefully, improve the movement at the base of the thumb.  The operation is typically performed under a general anaesthetic although increasingly under some form of local anaesthetic. A band, like a blood pressure cuff, is placed around the top of the arm. It is inflated (tightened) during the operation to reduce bleeding, which makes the operation easier and safer.  It can be a little uncomfortable if under local anaesthetic. Then two tourniquets are use sequentially and are almost always well tolerated for the 30 mins or so that that they inflated (this happens just before the surgeons starts the operation). Before that the arm is painted with an antiseptic with a pink dye in it. This is used to help minimise the risk of infection. A curved incision is made over the side and front at the region of the base of the thumb.  It normally measures around 2-3cm.  The nerves are protected and dissection is carried down to the bone which is removed completely. This creates a space which nature will fill with scar. There are various techniques described to optimise this space and reduce the risk of the base of the thumb abutting on the local bones and causing long term pain. None of these techniques has been shown reliably to be better than any of the others. We typically favour passing two stout wires from the thumb metacarpal (long bone at its base) into the index metacarpal to maintain the space for approximately 4 weeks or so.  This is not essential.  The deep tissues are closed and the skin is closed normally with an absorbable suture. Dressings and a plaster cast are applied.

The total time in hospital is usually 3-4 hours.

Recently we have started to perform semi joint replacements with encouraging early results. This may be a very important advance for this common problem but the role of this operation it is not yet clear.

What happens in the next few weeks?

The care of the hand in the post-operative period is very important in helping to ensure a good result. Initially the aims are comfort and elevation. These are met by keeping the hand up (elevated) especially in the first few days and by use of a long acting local anaesthetic (Bupivicaine). The local anaesthetic lasts at least 12 hours and sometimes 48 hours. Patients should start taking painkillers before the pain starts i.e. on return home and for at least 24 hours from there. This way most of our patients report little or any pain. At the first post-operative visit at 10-14 days following surgery the plaster will be changed for a snugger-fitting lightweight one, once the initial swelling has been allowed to settle. Typically dissolvable stitches are used so they should not require to be removed. The lightweight plaster cast will be removed to between 4-5 weeks when the wires will also be removed in the clinic. This is a little uncomfortable but not typically painful.  Local anaesthetic is not normally used but patients are usually advised to take pain-killers prior to that visit to reduce discomfort.  Then patients are encouraged to gradually use the thumb. Sometimes they will need a splint as a step down from coming out of plaster and occasionally they will require physiotherapy, although this is not typical.  This is, however, an operation that will leave the patient sore for at least 3 months and, like many, takes a good year to optimise.

Most patients return to work in 4-5 weeks, but this varies with occupation; heavy manual work usually takes at least 6 weeks and sometimes as much as 3 months. The wound should be massaged by the patient 3 times a day with a bland soft cream for 3 months once the wound is well healed (typically after 2 weeks). This reduces the scar sensitivity which can be a nuisance. If this is marked a physiotherapy may be organised to help reduce the scar tenderness but this is rarely required. Patients should avoid pressing heavily on the scar for 3 months following the operation as this will be quite painful. Examples of activities to avoid are using the palm to grip/twist a heavy or tight object or use the palm to help get out of a chair.

What are the results of the operation?

Typically around 85% of patients are very happy.  Only a few are absolutely and completely pain-free with all activities but most patients only have pain with the heaviest of pinching.  Their pinch strength is improved over that prior to surgery, although it never returns to the strength of their youth.  Of the remaining 10-15% the majority will have some but lesser benefit and will typically be pleased with having had the operation although perhaps a little disappointed not to have achieved a better result. A few, of the order of 1-2%, will be no better and may be worse.  Sometimes revision surgery is undertaken but this is less reliable than the first time operation.

Are there any risks?

All interventions in medicine have risks. In general the larger the operation the greater the risks. For trapezectomy the risks include:

  • The scar may be tender, in about 20% of patients.  This usually improves with scar massage, over 3 months.
  • Aching at the base of the thumb is typical for many months but generally settles.  Grip and in particular strength can also take some months to reach its best but it is never normal.
  • Stiffness may occur in particular in the fingers. This is usually short-term and only infrequently requires physiotherapy. But it is very important that it is resolved quickly to avoid permanent stiffness. This occurs rarely but can do associated with CRPS (see below)
  • There is a risk of nerve injury, particularly to the local branches of the radial nerve which supply the sensibility on the back of the thumb and index finger and the web space between them.  Almost inevitably these will require to be dissected out at the time of surgery and often there is some altered sensibility in this area which may last several months. Occasionally this will give long term ache and numbness which probably accounts for some of the poorer long term results in the 10-15% of patients who are unhappy with results. Rarely will this give very marked pain and might lead to CRPS (see below).
  • Wound infections occur in about 1% of cases.  These usually quickly resolve with antibiotics.
  • Sometimes there will be an imbalance in the thumb, such that the middle joint of the thumb will tip back.  If there is a significant risk of this then the surgeon will often stabilise this at the time of the primary operation, although this is infrequent, of the order of perhaps 1-2% only.  Occasionally the instability cannot be anticipated and a second operation to stabilise the middle joint of the thumbmay be required. This is rare (less than 1%).
  • Recurrent pain at the base of the thumb has been reported but in our experience if the patient achieved good results initially then they do not ever require further treatment although this cannot be guaranteed.
  • The wires may give problems in the hand and can even break which may require a small second operation to resolve. This is rare.
  • Chronic Regional Pain Syndrome “CRPS”.  This is a rare but serious complication, with no known cause or proven treatment.  The nerves in the hand “over-react”, causing swelling, pain, discolouration and stiffness, which very slowly improve.
  • Any operation can have unforeseen consequences and leave a patient worse than before surgery.