Ganglia are the commonest lumps referred to the Foot and Ankle Service. The commonest sites are the dorsolateral aspect of the foot; a few are related to the great toe or the ankle. They are commoner in women, with 55-83% reported in different series. They may occur at any age; the average age is about 40 years, slightly older than in the wrist.
The aetiology and pathogenesis of ganglia remains a controversy unencumbered by evidence.
Pain is commoner in reported series of pedal ganglia than in wrist ganglia: 70-84% compared with 26-55%. In studies of pedal ganglia, 8-18% presented with concerns about "the lump" compared with 66% in Westbrook et al’s study of wrist ganglia. However, Westbrook’s series was the only prospective study to investigate patient perceptions and it may be that such a study in the foot would produce different findings to those quoted.
The published reports of treatment of pedal ganglia are all retrospective reports. None report the criteria for inclusion or treatment allocation. None use outcome measures other than "recurrence" and reported complications, or identify the status of the person who determined outcome. Indeed, in one series outcome was determined from chart review only and in all others it is likely that this was the review method.
No study has reported the outcome of non-treatment of pedal ganglia. At other sites spontaneous resolution has been reported, especially in children.
Aspiration alone is reported in only one study but the results are combined with those of aspiration and injection and are incomplete. In the hand and wrist the recurrence rate is about 50% after simple aspiration.
Aspiration and steroid injection are reported in 4 studies. The recurrence rate was 25-62% (in total 39 recurrences in 91 ganglia – 43%). Kliman and Freiberg noted that one of their 4 recurrences resolved after a second aspiration/injection and none of the others required further treatment. Pontious et al reported 25 recurrences, of which 13 underwent surgery but the further course of the others was not reported. It seems that even recurrence of a ganglion does not necessarily require surgery. Therefore, recurrence and need for further treatment should be reported as separate outcome measures and the indications for further treatment should be clearly described.
Paul and Sochart randomised patients with wrist ganglia to have aspiration and either hyaluronidase followed by steroid, or steroid alone. The recurrence rates were 11% and 43% respectively. Prior instillation of hyaluronidase has not been reported in the foot and it would be worth repeating this study for pedal ganglia.
An additional purpose of aspiration is to make a diagnosis. No published series has examined this. In Blackburn we have identified 5 "ganglia" where aspiration failed. Four were excised surgically – one was a leiomyosarcoma, one a tuberculous abscess, one a lipoma and one a ganglion (the other patient declined aspiration after an ultrasound scan showed a typical lipoma).
None of these conservative studies reported any infections, steroid-induced tissue atrophy or any other complications.
Surgical excision of pedal ganglia was reported in three studies. The recurrence rate was 11-43% (in total 21 recurrences in 100 ganglia – 21%). In addition, among 67 patients where complications were reported, there were 6 nerve injuries and one superficial infection.
There seems no justification for primarily excising pedal ganglia. The commonest treatment is aspiration and steroid injection but this and the alternatives require fuller evaluation. We tend not to inject smaller ganglia due to concerns about leakage of steroid out of the ganglion. Surgical excision can be offered for recurrence after conservative treatment but the patient must be warned of the risks of recurrence and nerve injury.
Aspiration of a ganglion would seem to be within the capabilities of a primary care doctor, podiatrist, nurse specialist or physiotherapist. However, any such policy should be carefully audited before widespread application.