Myxoid cyst

Management Strategy

Myxoid cysts contain gelatinous material that has escaped from the distal interphalangeal joint. Treatment can involve evacuation combined with measures to prevent further escape from the joint. Simple drainage through an incision can achieve the first, but normally there is recurrence within a few weeks. Measures to prevent the further accumulation of fluid are directed at reducing joint pathology or blocking the pathway of escape of fluid. The first category includes the use of injected triamcinolone, which might reduce synovial inflammation and the pressure of fluid within the joint, and surgery for osteophytes. Osteophytes appear to weaken the joint capsule and possibly contribute to joint pathology and synovial fluid production. Their removal is associated with resolution of the myxoid cyst but at the risk of alteration of joint function.

Blockage of the path of fluid escape is achieved by a range of traumatic and scarring procedures. The challenge is to produce an effective scar over the joint without excess morbidity or a long-term nail dystrophy.

A practical compromise of morbidity, complexity of treatment, and efficacy is to employ cryosurgery in the first instance. This is best used with a distal block using lidocaine or bupivacaine. The cyst is then incised and drained. Two freezes of between 10 and 20 seconds with liquid nitrogen are given, with a complete thaw in between. Over the next 2 weeks the wound is dressed. This results in success in about 50% of cases involving fingers. Those that fail can be retreated in the same way or proceed to surgery. Morbidity is least when there is precise surgery to the path of fluid escape. This can be identified and then ligatured following methylene blue injection into the joint and then raising a flap in a distal-to-proximal path, containing the cyst in the roof of the flap. In many instances it is possible to gain the same benefit without preliminary dye injection. The flap is sutured back in place, and success is reported as 94% in the fingers. In some instances, patient preference or medical considerations may mean that surgery is the first-line therapy.

Transillumination is a useful clinical aid. Dermoscopy can be used, but rarely improves on transillumination. Where there is diagnostic doubt, simple incision can be helpful to demonstrate the gelatinous material. Alternatively, high-resolution ultrasound or MRI can be employed. The first can only help define whether the structure is cystic or not. The latter provides better anatomic definition and in over 80% of cases allows location of the pedicle communicating between the cyst and joint. Plain X-ray may reveal osteophytes of osteoarthritis, but this will not usually alter treatment.