Base of Thumb OA

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

Surgery is performed under general anaesthetic or regional anaesthesia (only the arm is made numb). The surgery takes between 30 and 40 minutes. A tourniquet is used; which is like a blood pressure cuff around the upper arm that prevents blood from obscuring the surgeons view. The trapezium (arthritic) bone is removed, leaving a space. There are a number of variations to stabilise this space:

• Leave it as a space with or without a temporary wire to hold the joint stable.
• Fill it in with a rolled up ball of tendon (Anchovy)
• Use a spare half tendon as a suspension sling to stabilise the joint (My choice in most patients)
• Joint replacement (Offers a stronger pinch but has the risk of dislocation).
• Fusion (My choice in young high demand manual workers)

The skin is sutured and an immobilising Plaster of Paris slab applied.

Post-operative rehabilitation

The patient is fit to go home soon after the operation, either the same day or the next 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 on day 2-4, 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 approximatelyr 4 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.

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 Trapeziectomy and also general complications associated with hand surgery.

General complications:

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

Reflex Sympathetic Dystrophy - RSD (2% bad 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.
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.