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 particularly over the age of 50 years.
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 than males and is usually starts over 50 years of age. usually as a result of a previous fracture.
Why does it occur?
There are two types of OA. Primary and Secondary.
Primary OA is the most common cause and is simple wear and tear. Abnormal loads across the joint cause the articular cartilage (slippy ends of bones) to wear away, leaving bone on bone ends rubbing together.
Secondary OA occurs often after a fracture into the joint causing a sharp bone surfaces to rub and wear the joint away.
Symptoms
Well-localised pain at the base of the thumb is the most common symptom. Provoking activities include the unscrewing of jars, and pinch grip and turning a key using the thumb often cause pain.
Clinical Examination
Bony swelling is apparent at the base of the thumb in more 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.
We often obtain three X-ray views : a thumb CMCJ AP (Robert view) and a AP and lateral Wrist. The lateral wrist helps me look at the alignment of the wrist bones and in particular the lunate bone to make sure there is no co existing scapho-lunate ligament attenuation in the wrist. The Robert AP CMCJ view is the best view to see the joint and notice the abnormal surfaces.
Non-operative treatment
- Rest, pain killers (analgesia) and avoidance of provoking activities.
- Resting night splint prescribed by a hand therapist
- 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 ultrasound or X-ray control. I only perform one or two injections before considering surgery. The risks associated with steroid injection are small but include, failure to give long lasting benefit and a small risk of causing a skin reaction with altered skin pigmentation or in severe cases thinning of the fat under the skin.
Operative treatment
If 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.
Mike would always discuss the options available and these may be guided by the patients age and functional demands.
The main 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 preventing the painful bones rubbing on each other
- 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.
The surgeries will be discussed below including post operative complications but can also can be found by clicking here
Trapeziectomy
In the past having removed the trapezium Mike used to a perform ligament reconstruction, fill the space with rolled up tendon or perform a sling type procedure. However having reviewed the literature he now simply removes the trapezium and repairs the joint capsule and does not perform a sling procedure. The space that is left seems to fill with scar tissue and the results in his practice shows no difference with the sling / reconstruction type procedures.
One of the main risks of trapeziectomy is proximal migration of the thumb metacarpal. If this occurs it can very difficult to stabilise the thumb and ultimately may require a procedure to fuse the thumb metacarpal to the index metacarpal which is a difficult operation.
Proximal migration would be a major concern in a younger individual and in such cases most people would prefer a thumb CMCJ fusion or a total joint replacement.
Thumb CMCJ fusion
Mike tends to prefer a thumb CMCJ fusion in physically high demand patients often under 50 yrs of age. The ends of the bone are removed with a small saw and then compressed together and held with two staples. Over the next 6 weeks or so the bone grows across the joint and abolishes any movement and hence pain that was present at the joint. The thumb is somewhat stiffer than normal and patients will not be able to contour the flat against a table. Most do not consider this a problem and are happy that the thumb is pain free and strong.
Thumb CMCJ replacement
Thumb CMCJ replacement is now becoming more common in the UK with good results supported in the medical literature. The ends of the bone are removed and a new joint is inserted very similar to a mini hip replacement. The results are very good and Mike is increasingly offering this as an alternative.
There are additional risks with this procedure and these include fracture of the surrounding bones, dislocation and subluxation of the joint, loosening and wear of the joint. Salvage of a failed thumb CMCJ replacement is a trapeziectomy often leaving the metacarpal stem in place if well fixed and buried.
Please click on this link to view an actual operation showing how the joint moves.
Post-operative rehabilitation
The patient is fit to go home soon after the operation 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 prevent swelling 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
The wounds should be kept covered and dry for the first 10 days until the wound has healed.
The splint or cast should be kept dry and this can be gradually removed with the supervision of my hand therapist.
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.
Please look at my general hand complications page by clicking here but also see below for some specific complications
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. 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. 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. 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.
Wear and Loosening. When a joint replacement is performed there is a risk that the joint can wear out and loosen and need revising, usually to a trapeziectomy.
Fracture. There is a small risk of a fracture occurring when inserting the implant.The majority are very small cracks that heal without issue. Extremely rarely the trapezium can break on impacting the trapezium cup and requires revising to a trapeziectomy.