Base of Thumb OA

by Mr Mike Hayton
FRCS(Trauma and Orth) FFSEM (UK)
Consultant Orthopaedic Hand Surgeon

Other common names

 - Thumb Carpo-metacarpal joint OA, (CMCJ OA)
 - Thumb Trapezio-metacarpal joint OA (TMCJ OA)
 - Saddle joint OA

Who does it affect?

Osteoarthritis of the base of the thumb is a very common condition.

Approximately 40% of post-menopausal females have radiographic changes at the base of the thumb, 10% seek medical treatment and 1% are severely afflicted.

Base of thumb OA is more common in females over 50 years. It occasionally occurs in men but usually as a result of a previous fracture.

Why does it occur?

Abnormal loads across the joint cause the articular cartilage (slippy ends of bones) to wear away, leaving bone on bone ends rubbing together. In women we often do not know the cause, but in men, following a fracture into the joint, there may be sharp bone surfaces that wear the joint away.

Symptoms

Well-localised pain at the base of the thumb is the most common sympton. Provoking activities include the unscrewing of jars, and pinch grip using the thumb can also cause pain.

Clinical Examination

Bony swelling is apparent in advanced cases and local palpation at the base of the thumb is tender. Specific tests include the Axial Grind Test, whereby the thumb is pushed along its long axis towards the base of the thumb. Reduction Relocation test involves pressing the base of the thumb joint with one hand whilst circumducting the end of the thumb with the other hand.

Investigations

X-rays of the thumb reveal the typical features of loss of joint space and osteophyte (extra bone) formation.

Non-operative treatment

 - Rest, pain killers (analgesia) and avoidance of provoking activities.
 - Resting night splint
 - Intra-articular steroid injection.

Approximately half the patients I see have joints that are easy to palpate and I inject them in clinic. However the other half are more difficult and require the injection to be performed under X-ray control. I only perform one or two injections before considering surgery.

Operative treatment

Non-operative techniques have been tried and have not given long-lasting benefit some patients may elect to undergo surgery. 

The aim of surgery is to prevent the two ends of the bone from rubbing against each other.

The options are :

  • Trapeziectomy - remove the trapezium bone and allow the space to fill with scar tissue
  • Thumb CMCJ Fusion - fuse the trapezium and thumb metacarpal bones to make a solid joint 
  • Thumb CMCJ replacement - remove the ends of the bone and insert a new artificial joint replacement

 

The decision about which particular surgery is the most appropriate for an individual patient is made having considered the functional demands of the patient and the preoperative X-ray.

Surgery is performed under general anaesthetic or regional anaesthesia (only the arm is made numb). Each of the surgeries listed above take between 30 and 40 minutes. 

The skin is sutured with absorbable buried stitches and an immobilised with a half  Plaster of Paris slab applied.

Post-operative rehabilitation

The patient is fit to go home soon after the operation usually on the same day. Simple analgesia usually controls the pain postoperatively and should be started on discharge. The hand should be elevated as much as possible for the first 5 days to preventswelling in the hand and fingers. Gently bend and straighten the fingers from day 1. The back slab Plaster of Paris is removed in the first week when the wound is cleaned, redressed and a therapy made splint (cast) is applied.

The sutures are usually dissolvable and buried under the skin.  The splint (cast) is kept for approximately 6-8 weeks. Therapy exercises will commence to regain mobility and strength. Patients usually notice that the arthritic pain has gone within 8 weeks but the results improve between 6 and 12 months as the thumb strengthens.

Return to activities of daily living

Keep your splint (cast) dry.

Return to driving: The hand needs to have full control of the steering wheel and left hand the gear stick. It is probable advisable to delay return to driving until you are pain free and can control a car in an emergency. This may be between 8 and 12 weeks, although everyone is different and some patients feel safe to drive within a few weeks.

Return to work: Everyone is involved in different working environments. Return to heavy manual labour should be prevented for approximately 8weeks. Please ask your surgeon for advice on this.

Complications

Overall, greater than 85% are happy with the result. However complications can occur.

There are complications specific to thumb surgery and also general complications associated with hand surgery.

General complications:

Infection (Less than 1%), 
Neuroma (Less than 1%, a coiled painful nerve bundle),
Numbness,

Chronic regional pain syndrome  (1-2% rare reaction to surgery with painful stiff hands - this can occur with any hand surgery from a minor procedure to a complex reconstruction).

Specific complications:

Failure to completely resolve the symptoms (this may be due to arthritis in adjacent joints, this should be rare but may require further surgery).
The thumb will be weaker on the opposite side, which should improve with time, but will never be normal.

Proximal migration of the thumb metacarpal (5%).​ This can occur after a trapeziectomy when the thumb metacarpal drops down into the space left once the trapezium has been removed. It can be improved using a sling type procedure to hold up the thumb or the thumb be fused.

Non union (5-10%). This is only relevant to a thumb CMCJ fusion, when the bone ends do not join. Occasionally this is painless and can be left alone. If painful revision surgery may be needed repeating the operation using bone graft or alternatively performing a trapeziectomy 

Dislocation (5% - 10% when an implant is used), occasionally, when an implant is used there is the risk of dislocation, but the theoretical benefit is of a stronger thumb. If it dislocates it may need to be removed and the space dealt with as in other operations.