This is a pocket filled with viscous fluid from a wrist or finger joint, or from a tendon sheath. The most common locations are the wrist, either on the dorsal surface or where the pulse is palpated, and the back of the fingertips. The onset of cysts is more often spontaneous with no triggering factor, although some cysts may appear after an accident or be linked to the presence of osteoarthritis (wear and tear of articular cartilage). The cyst may be painful to palpate and when the wrist is mobilized. This lesion is always benign.
What tests are required?
In most cases, the patient’s description of symptoms and examination of the hand are sufficiently typical to make the diagnosis. Ultrasound may be necessary to confirm the diagnosis and pinpoint the location of the cyst in certain situations where it does not appear on the outside, but remains deep inside.
What treatments are available for synovial cysts?
This is the most common treatment. When the injury originates in the wrist, wearing a removable splint for a few days or weeks can relieve the pain. After this period, the cyst often diminishes in size and becomes painless. Short courses of anti-inflammatory medication can alleviate pain wherever the cyst is located.
When the cyst is painful and not relieved by splinting, it can be reduced by puncture and infiltrated with a little cortisone to prevent recurrence. Cysts of the finger flexor tendon sheath can be punctured if they are troublesome. Recurrence is rare in these cases, unlike puncture of other cysts.
Surgery is necessary in some cases, but always after non-surgical treatment has failed. This involves removing the entire cyst right down to its origin, whether articular or tendinous. It should be noted, however, that the recurrence rate is fairly high (7-15%). The procedure lasts around thirty minutes and is performed on an outpatient basis, under local anesthetic (hand and forearm). A splint is worn for a few days, before the wrist can be mobilized. The fingers should be mobilized as normally as possible. Sutures are removed after two weeks (unless they are absorbable).
Heavy lifting, extreme wrist movements and sports activities involving the operated hand should be avoided for four to six weeks. While an office job allows you to return to work in as little as two weeks, a manual job requires you to take four to six weeks off work. Physiotherapy or occupational therapy may be indicated in cases of stiffness, particularly flexion, which can take a long time to return.
What are the possible complications?
- Non-surgical treatment
There are no known complications from leaving a cyst in place, even if it causes pain.
Puncture of a cyst may exceptionally injure a nerve, artery or tendon.
- Surgical treatment
Common to all surgeries
Infection of the wound may occur, but is usually cured by local care and the prescription of antibiotics. Surgical drainage is rare.
Hematoma corresponds to an accumulation of blood under the skin. It’s not a problem if it’s small, but if it’s larger, surgical evacuation may be necessary.
Healing problems (delayed healing, thick scars) occur more frequently in patients who smoke.
Inadvertent injury to an artery, nerve, ligament or tendon is always possible, although rare. These structures can be repaired, but recovery may be prolonged or even incomplete.
Chronic regional pain syndrome is a disproportionate inflammatory reaction of the body following surgery. It causes pain, swelling and stiffness, requiring treatment that can last several months.
Complications specific to synovial cysts
Recurrence occurs in around 7-15% of cases, after a period that can vary from a few months to several years. If pain returns, further surgery may be necessary.
The wrist often becomes stiff after surgery, i.e. its mobility is reduced. This can take several months to recover and may require physiotherapy treatment. In rare cases, full mobility is never regained.