Digital Mucoid Cysts
What is a Digital Mucoid Cyst?
A Digital Mucoid Cyst is a subtype of ganglion cyst located specifically on the distal interphalangeal joint of the finger, which is the joint closest to the finger tip. It is found on the back of the hand, on the lateral edge of the joint, never in the midline. Some digital cysts can extend into the fingernail bed. Underneath, the cyst is connected to the joint by a stalk. Digital Mucoid Cysts are filled with a thick, gelatinous fluid which consists mainly of hyalouronic acid, and are benign growths.
What causes a Digital Mucoid Cyst?
While the exact cause of Digital Mucoid Cysts is unknown, there is a strong association with degenerative joint disease of the affected joint. Osteoarthritis and Rheumatoid Arthritis are two conditions which may cause degeneration of a joint. Repeated trauma to the joint may also be a factor.
What are the symptoms of a Digital Mucoid Cyst?
A digital mucous cyst appears as a small, non-mobile, soft to firm, round bump at the joint nearest to the fingertip. Any finger can be affected, but the most common finger involved is the index finger. The cyst may appear suddenly, or more frequently, increase slowly in size. Smaller cysts may not cause any symptoms, while larger cysts may be tender or cause pain with activities of daily living. If the cyst is located next to the fingernail bed, it may cause a deformity of the shape of the fingernail, such as a notch or a ridge. Irritation of the overlying skin on the finger can occur, and if the skin breaks open, the cyst can rupture, releasing the thick, viscous fluid within. Care must be excised with these open wounds as the cyst complex extends into the underlying joint, and infection could potentially spread to the bones of the hand.
How is a Digital Mucoid Cyst diagnosed?
A careful history and thorough physical exam are the first step in determining if a Digital Mucous Cyst is present. Imaging studies such as X rays, ultrasound, CT, or MRI are often utilized to assess the cyst and examine the condition of the affected joint. Since this condition is almost always associated with degenerative changes in the joint, it is important that the joint be evaluated so that the underlying degeneration can be addressed, and the best treatment method employed.
How is a Digital Mucoid Cyst treated?
There are both non-surgical and surgical options for the treatment of a Digital Mucoid Cyst.
Non-surgical options for the treatment of Digital Mucoid Cysts are plentiful. Many patients with these cysts present to their Primary Care Provider, Dermatologist or Plastic Surgeon for initial treatment. Depending on the specialty, needling, or serial lancing, of the cyst to drain the fluid is common. Cryosurgery, or freezing the lesion with liquid nitrogen, is also used. More recently, lasering the cyst with a CO2 laser has found some success. Injection of of a corticosteroid into the cyst may be used. The rate of recurrence with these techniques is high, because they do not address the underlying bone spur from the associated degenerative joint disease so often present with the Digital Mucoid Cyst.
In contrast, a hand surgeon is able to remove the cyst surgically as well as address the bone spur at the distal interphalangeal joint, greatly reducing the risk of recurrence. Through an incision over the cyst and distal interphalangeal joint, the surgeon is able to remove the cyst and its stalk, or pedicle, along with any osteophytes, or bone spurs, present which may have been the root cause of cyst formation.
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Learn more about surgery to remove Digital Mucous Cysts, click video below.
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