Mucous cysts of the fingers are very common. They are most commonly seen on the backs of the fingers on one side or other of the finger over the last joint of the finger. They often cause irregular growth of the nail (ridging or "dishing" of the nail).
I like to describe mucous cysts as a symptom of a underlying disease rather than a disease in themselves.
The underlying cause of mucous cysts of the fingers is osteoarthritis of the underlying joint.
Osteoarthritis of the smallest joints in your fingers is very common. It can be a condition inherited from your mother or father or it can be the result of wear and tear over the years or a specific traumatic incident such as a broken bone or injury to the joint of that finger.
When you have arthritis in one of these small joints, over time the cartilage covering of the bone is worn away. This leaves the underlying bone exposed so that you have bone on bone contact at either side of the joint as your finger joint moves. This bone on bone contact causing irriatation of the bone forming cells which can make a small bone spur (we call this an osteophyte). Osteophytes are irregular spiky lumps of bone .You may be able to feel them on the backs of the joints involved.
This osteophyte can wear away the covering, stabilising tissues on the back of the joint (the joint capsule) so that a tiny hole develops. When this occurs some of the lining tissue of the joint (the synovium) can poke out through this hole forming a "mucous cyst".
The normal job of this lining tissue of the joint (the synovium) is to make the joint fluid (synovial fluid) so even though it is now outside the joint capsule it continues to make this fluid and thus the cyst can grow bigger.
Often the cysts increase and decrease in size. What is happening when this occurs is that some of the cyst fluid empties back into the joint (and the cyst gets smaller or disappears for a while) but it slowly increases in size again and more fluid is produced.
The ridging of the nail occurs because all this happens in a very confined space and if the cyst is pressing down on the nail bed (base of the nail) over months as the nail grows a "pressure related" ridge or irregularity develops. Is you remove the cyst and the pressure is no longer there the ridge goes away and the new nail grows out over months.
We have a range of non surgical and surgical treatments to offer for mucous cysts of the fingers.
Because we do not have a cure for the underlying condition cauing mucous cysts that osteoarthritis we try to avoid operating on them.
Often the best treatment is no treatment. If the cyst is not painful and not causing other symptoms it is often best left alone.
In some cases we can aspirate the cyst and inject a medicine into the cyst cavity which irritates the internal surfaces of the cyst. This aims to make the internal layer of the cyst "sticky" so they stick to each other and scar up preventing recurrence.
In a small number of cases surgery is indicated usually because the patient is finding the cyst painful.
If surgery is required it is normally a Day procedure performed at the hospital.
The surgery is performed under local anaesthetic with intravenous sedation so that you do not require a general anaesthetic for this condition. The added benefit of the local anaesthetic is that is provides excellent post operative pain control.
The surgery itself requires removal of the cyst, opening of the joint to make sure all of the cyst is removed, removal of the bone spur (osteophyte), repair of the joint capsule and replacement of the skin where the cyst existed either with a local flap of tissue or a skin graft .
After the surgery you will have a bandage and a splint of that finger only. All your other fingers will be left free. You will notice the day after surgery all of your other fingers are puffy and swollen. This will settle.
You will have a dressing on the operated finger fro 2-4 weeks following surgery.
Risks: Any surgery however minor has risks. Fortunately major issues following surgery for mucous cysts is very rare.