6.13 Ganglia of the wrist and hand

Ganglia have featured in medical literature for over 250 years. They represent approximately two-thirds of all hand swellings and are most commonly seen between 20–40 years of age. However, they may be found in any age group. Annual incidence rates for ganglia of the wrist and hand are approximately 25 per 100 000 and 43 per 100 000 for males and females respectively

Ganglia present as smooth round swellings which vary in consistency from soft to bony hard, depending on the pressure within them. They may be single or multiloculated but are seldom attached to skin.

Histologically, the ganglion wall consists of compressed collagen fibres lined by a few flat cells. There is no true epithelial or synovial lining membrane. The typical clear mucinous fluid within the cyst contains high concentrations of hyaluronic acid, together with glucosamine, globulin, and albumin.

Several lines of evidence indicate that the contents of ganglia originate from synovial cavities (i.e. joint or tendon sheath) nearby, but it is unclear if ganglion fluid is simply synovial fluid which has escaped from the joint or if it is formed by cells in the synovium at the origin of the ganglion. Ganglion fluid closely resembles synovial fluid in its composition. Ganglia are almost exclusively found near a joint or tendon sheath, with which a communication can often be demonstrated. Arthrographic and cystographic studies have shown that dye will frequently pass from joint to ganglion but, in the few cases studied, not in the reverse direction. The classical study of Angelides and Wallace (1976) examined the capsular attachments of 64 dorsal wrist ganglia under magnification in situ. In all cases, the ganglion arose from the dorsal surface of the scapholunate ligament. After dissection of the capsular portion of the ganglion from the scapholunate ligament, a small quantity of ganglion fluid seeped from the surface of the ligament in every case. Examination of this area under magnification showed that small gaps appear between the transverse ligament fibres in dorsiflexion and close in flexion. The capsular origin of the ganglion contained many small cystic spaces that were shown by serial sections to be parts of a tortuous continuous duct that connected the ganglion cyst with the joint. The hypothesis is that synovial fluid passes from the scapholunate joint along a continuous duct that acts as a one-way valve between the scapholunate ligament and the main ganglion cyst. Whether similar mechanisms operate at other sites of ganglia is unknown. The predilection for the four typical sites in the hand and wrist has not been explained. There is no good evidence to support traumatic or inflammatory aetiologies.

Patients present with swelling which may be accompanied by pain, stiffness, or weakness of the associated joint. Variation in size over time, especially a reduction in size, is virtually diagnostic of ganglion. Large ganglia may show the sign of fluctuance and may be transilluminated.

Obscure wrist pain is sometimes caused by an occult ganglion; there is local tenderness at one of the typical sites (usually the dorsum of the wrist) but the ganglion is too small to be visible or palpable. Occult ganglia can be identified by ultrasound or magnetic resonance imaging (MRI).

Ganglia resolve spontaneously in around 40% of cases. They may produce symptoms by extrinsic compression of adjacent structures such as the ulnar nerve in Guyon’s canal and the median nerve in the carpal tunnel. Pressure on the terminal branch of the posterior interosseous nerve at the wrist may account for the pain caused by dorsal wrist ganglia.

Ganglia are most usually classified according to their site of origin (Table 6.13.1).

The most common type of ganglion arises from the wrist capsule over the dorsal surface of the scapholunate ligament. The pedicle that connects the ganglion with its articular origin may pass some distance beneath the extensor tendons before coming to the surface, so the ganglion itself may present some distance from the scapholunate area (Figure 6.13.1). When planning the removal of a ganglion that is not located in the typical site, the possibility of a connection with the scapholunate ligament should be borne in mind, so that an incision can be designed to allow access for excision of the pedicle (the key to successful surgical treatment) without leaving an unsightly scar.

Palmar wrist ganglia typically present at the proximal wrist crease between the radial artery and the flexor carpi radialis tendon (Figure 6.13.2). Two-thirds originate from the radiocarpal joint at the scapholunate interval; the remainder arise from the scaphotrapezial joint. Ganglia arising from the scaphotrapezial joint may track along the tendon sheath of flexor carpi radialis and come to the surface some distance from their origin. Palmar wrist ganglia may occur in older patients in association with scaphotrapezial osteoarthritis. In these cases, the risk of recurrence is high unless the underlying arthritis is also treated by arthrodesis or excision arthroplasty. The symptoms seldom justify surgery of this magnitude.

These ganglia may be closely related to the radial artery and require careful dissection from it. A preoperative Allen test and tourniquet release before skin closure should be considered when excising palmar wrist ganglia.

Palmar wrist ganglia may be more extensive than clinical examination suggests. An extensile surgical approach is advisable, so as to deal with possible extensions under the thenar muscles, into the carpal tunnel, and along the sheath of flexor carpi radialis tendon. Excision of palmar wrist ganglia should be approached with caution. Small subcutaneous nerve branches are prone to produce painful neuromas if injured in this region. It is not always easy to identify the pedicle of the ganglion, the scar may be unattractive, and the recurrence rate is higher than for dorsal wrist ganglia (Table 6.13.2).

A 2- to 5-mm-diameter ganglion, also known as volar retinacular ganglion or seed ganglion, commonly arises from the A2 pulley of the flexor tendon sheath at the proximal digital crease.

Patients complain of accurately localized pain when gripping objects such as the steering wheel of a car or when carrying objects. The ganglion is small, hard, and tender. It sits on the external surface of the tendon sheath in the midline or just to one side it and does not move with the tendon. The ganglion may be punctured with a fine needle inserted in the midline of the digit, so as to avoid the digital nerves, and its contents dispersed by firm massage. If the ganglion persists or recurs, it may be excised together with a small disk of tendon sheath. Care should be taken to preserve the major part of the A2 pulley. Recurrence after excision is very uncommon.

Ganglia arising from the distal interphalangeal joint are sometimes known as mucous or myxoid cysts. They occur in older individuals and are often associated with early osteoarthritis of the distal interphalangeal joint. Pressure from the ganglion on the germinal matrix may produce a furrow in the fingernail; the furrow may appear before the ganglion is evident (Figure 6.13.3).

The ganglion arises from the joint capsule between the collateral ligament and the extensor tendon, presenting just to one side of the midline, typically between the distal joint crease and the eponychium but occasionally preoximal to the distal interphalangeal joint. The overlying skin may become very thin, giving the ganglion a pearly appearance and leading to occasional discharge of clear viscous fluid.

Operative excision requires removal of the cyst in continuity with a block of joint capsule between the extensor tendon and collateral ligament. The nail matrix should be protected. A local synovectomy and removal of osteophytes may help to prevent recurrence. Small defects in the thin skin overlying the ganglion will heal spontaneously. In the rare case of a large defect, a full-thickness skin graft or dorsal advancement flap may be required. The risk of recurrence is probably less than 5%.

Intraosseous ganglia are uncommon. The most frequent site is the radial border of the lunate (Figure 6.13.4), where a communication between the lesion and the scapholunate joint is usually found. Computed tomography (CT) examination and operative exploration often show a communication that is not evident on plain radiography. The predilection of intraosseous ganglion for bones on each side of the scapholunate joint suggests that intraosseous and soft tissue ganglia share a common, as yet unknown, pathogenesis.

Intraosseous ganglia may be found in patients with wrist pain but are not always the cause of it; other causes of pain should be excluded. Operative treatment is curettage and bone grafting, but relief of pain may be incomplete

Intraneural ganglia are rare. The ganglion is usually located within the nerve sheath and may extend for some distance above and below the point at which it is clinically obvious. The cause of intraneural ganglia is not clear. One theory is that synovial fluid gains access to the epineural sheath where an articular nerve branch enters the joint capsule and runs proximally into the main nerve trunk. Mucoid degeneration and fibrous tissue metaplasia have also been proposed. Although the most common site is within the common peroneal nerve at the knee, intraneural ganglia have been reported in the radial, median, and ulnar nerves (Figure 6.13.5).

A confident diagnosis of ganglion is usually possible on the clinical features alone. If necessary, the diagnosis can be confirmed by aspiration of the typical ganglion fluid. Ultrasound can demonstrate the cystic nature of the swelling. MRI is helpful in the diagnosis of occult wrist ganglia and in delineating the site and extent of ganglia that present in unusual locations.

Plain radiography is useful in excluding other causes of wrist pain and should be performed before a ganglion is treated operatively. CT imaging may be useful in diagnosis of intraosseous ganglion and identification of a communication with an adjacent joint.

The management of ganglia is influenced by several facts: ganglia are harmless; some ganglia disappear spontaneously; recurrence is possible after aspiration or excision; and excision is not without complications.

The options for treatment of ganglia are reassurance, aspiration, and excision. Some patients are concerned about the development of a mass, but have few symptoms and are content with reassurance that the swelling is harmless.

Aspiration of ganglia requires a wide-bore needle, taking appropriate care of adjacent structures such as the radial artery. Studies of aspiration of ganglia have shown quite disparate rates of recurrence that may be explained by differences in case mix. Palmar wrist ganglia appear to have a significantly higher risk of recurrence after aspiration (Table 6.13.3). Aspiration may be accompanied by attempts to puncture the cyst wall with the needle or by instillation of steroid, or followed by immobilization. It is uncertain if these manoeuvres reduce the risk of recurrence after aspiration Ganglia that recur after aspiration tend to do so within 3 months. Flexor sheath ganglia are too small for aspiration but can be dispersed by firm pressure after puncturing the cyst wall with a needle.

Successful excision of wrist ganglia depends upon the identification of the pedicle connecting cyst to joint. The pedicle should be excised together with a disc of surrounding joint capsule. Closure of the capsular defect is difficult, unnecessary, and may restrict movement of the wrist. Contrasting evidence exists regarding the use of immobilization after surgical excision. Most authors recommend that movement should begin as soon as possible postoperatively, since immobilization may lead to stiffness.

Arthroscopic excision of dorsal wrist ganglia is no more reliable at reducing recurrence rates than open excision.

Although recurrence is much less frequent after excision than after aspiration (Tables 6.13.2 and 6.13.3), the benefits of excision must be considered against the risks. The mere presence of a ganglion is not an indication for surgery. In addition to general risks of haematoma and infection, local complications such as tender or hypertrophic scars, injury to superficial sensory nerves, and loss of wrist motion occur in up to 8% of patients. These may mar the result. The small but real risk of complications should tilt the decision away from surgery unless the ganglion is persistent and the cause of significant symptoms.