Ganglion cysts are synovial cysts that are filled with gelatinous mucoid material and commonly encountered in orthopedic clinical practice. Although the exact etiology of the development of ganglion cysts is unknown, they are believed to arise from repetitive microtrauma resulting in mucinous degeneration of connective tissue. They are the most common soft tissue mass found within the hand and wrist, but they are also commonly encountered in the knee and foot. Although the majority of ganglion cysts are asymptomatic, patients may present with pain, tenderness, weakness, and dissatisfaction with cosmetic appearance. Both non-operative and surgical treatments are available, but a high recurrence rate has historically plagued non-surgical treatment. Surgical excision can provide resolution of patients' symptoms, but an understanding of the underlying anatomy adjacent to the cyst is crucial to avoid injuring neurovascular structures within proximity to the cyst.
Numerous theories have been presented in the past regarding the etiology of ganglion cysts with no present consensus. One theory introduced by Eller in 1746 is that ganglion cysts are the result of the herniation of synovial tissue from joints. Another theory postulated by Carp and Stout in 1926, which forms the basis of most modern belief, suggests that ganglion cysts result from mucinous degeneration of connective tissue secondary to chronic damage. Currently, most authors agree that ganglion cysts arise from mesenchymal cells at the synovial capsular junction as a result of the continuous micro-injury. Repetitive injury to the supporting capsular and ligamentous structures appears to stimulate fibroblasts to produce hyaluronic acid, which accumulates to produce the mucin "jelly-like" material commonly found in ganglion cysts.
Ganglion cysts account for 60% to 70% of soft-tissue masses found in the hand and wrist. Although they can form at any age, they are most commonly found in women between the ages of 20 to 50. Women are three times more likely to develop a ganglion cyst than men. These cysts are also frequently encountered amongst gymnasts, likely secondary to repetitive trauma and stress of the wrist joint.
Ganglion cysts are mucin filled synovial cysts containing paucicellular connective tissue. They may be filled with fluid from a tendon sheath or joint. Ganglion cysts are most commonly found (70%) on the dorsal aspect of the wrist arising from the scapholunate ligament or scapholunate articulation. Approximately 20% of ganglion cysts are located on the volar aspect of the wrist arising from the radiocarpal joint or scaphotrapezial joint. The remaining 10% of ganglion cysts can arise from multiple areas of the body including the volar retinaculum of the wrist, distal interphalangeal joint, ankle joint, and foot. Wrist volar retinacular cysts arise from herniated tendon sheath fluid that protrudes out. Ganglion cysts arising from the dorsal DIP joint are called mucous cysts and are associated with Herbeden's nodules. They are commonly found in women between the ages of 40 and 70 with osteoarthritis.
Biopsies of ganglion cysts are not routinely indicated because of their inherently benign nature. Typical histopathological appearance is a mucin-filled synovial cell lined sac without a true epithelial lining. Ganglion cysts can be single or multiloculated. When examined under electron microscopy, their walls contain sheets of collagen fibers arranged in multidirectional layers with intermittent flattened cells resembling fibroblasts. The thick mucinous material present in the majority of ganglion cysts is highly viscous, which is attributed to a high concentration of hyaluronic acid and mucopolysaccharides.
The majority of ganglion cysts are asymptomatic, but patients may seek treatment because of their unsightly cosmetic appearance. Patients may present with pain, tenderness, or weakness that is exacerbated by wrist motion. Ganglion cysts usually present as firm, well circumscribed, freely mobile masses approximately 1 cm to 3 cm in size. They are often fixed to deep tissue and not to the overlying skin. Patients with volar wrist ganglion cysts less commonly may present with carpal tunnel syndrome or a trigger finger secondary to compression of the median nerve or intrusion on the flexor tendon sheath. Volar wrist ganglion cysts can also cause ulnar nerve neuropraxia and compression of the radial artery leading to ischemia. Ganglion cysts will usually transilluminate on the exam.
Radiographs may be ordered to rule out any related intraosseous manifestation, but will generally be unremarkable. MRI is usually not indicated for ganglion cysts unless there is a concern for a possible solid tumor. MRI will show a well-circumscribed mass with uniform fluid intensity on T2 weighted imaging. Ultrasound can be used to differentiate a cyst from a vascular malformation and to avoid accidental puncture of the radial artery during needle aspiration of a cyst.
Asymptomatic patients can be observed and reassured that ganglion cysts are benign and may spontaneously regress. Non-surgical treatment may be attempted depending on the location of the cyst. Dorsal wrist ganglion cysts can be aspirated, but there is a much higher recurrence rate than with surgical excision. Aspiration of volar wrist ganglion cysts is not generally performed due to their proximity to the radial artery. Surgery is indicated for patients with continuing symptoms who have failed conservative management. Surgical excision is usually performed as an outpatient procedure. Dorsal wrist ganglion cysts are approached through a transverse incision made directly over the cyst. Careful dissection is performed to expose the pedicle of the cyst and to avoid rupturing it, which would make excision of the capsular attachments more difficult. The pedicle and capsular attachments should be detached as close to the scapholunate ligament as possible without disrupting the integrity of the ligament. Failure to resect the pedicle of the ganglion cyst, its capsular attachments, and part of the capsule has been associated with a high rate of recurrence. Volar wrist ganglion cysts are often close to the radial artery or sometimes may surround the vessel. Blunt dissection should be used to mobilize the artery from the cyst with care taken to avoid injuring the vessel. The palmar cutaneous branch of the median nerve arises 5 cm proximal to the wrist joint and is also at risk with volar wrist ganglion cyst excision. The most common complication of surgical excision is a recurrence, and volar wrist ganglion cysts have a higher recurrence rate than dorsal wrist ganglion cysts. Ganglion cysts have a recurrence rate of approximately 15% to 20%.