Plantar Fibroma

Summary

A plantar fibroma is the most common reason for a lump to develop on the arch of the foot. These are often small (less than half an inch), but can grow steadily to reach sizes of 2 inches or more. They may occur as a single lesion or may present as multiple lesions typically along the medial border of the plantar fascia.  They are benign and are composed of dense, fibrous tissue.  Many patients with plantar fibromas do not have any symptoms and when they do it is often only a vague discomfort from “walking on a lump”. These masses can be treated non-surgically with a custom or soft accommodating prefabricated (over the counter) orthotic. However, if they grow larger or are a persistent source of discomfort they should be removed surgically.

History

Patients with plantar fibromas will usually report that they just noticed the mass one day. Occasionally they will have a history of a similar mass in the palm (Dupytren’s Contracture). As the mass gets larger they may report increasing discomfort with prolonged standing

Physical Examination

Plantar fibromas are usually located on the inside of the arch of the foot. They usually feel smooth and rubbery. They are not usually tender to touch although they may become irritated with prolonged walking.

Imaging Studies

X-rays

X-rays are often negative, although if the x-rays are taken in such a way as to highlight the soft-tissues an outline of a mass may be seen.

MRI

An MRI will show a smooth, consistent (homogenous) mass that is affiliated with the plantar fascia. An MRI will confirm the diagnosis and allow differentiation of other causes of masses in the foot such as lipomas, ganglions, neuromas, herniations of the plantar fasica, and tumors (very rare).

Treatment

Non-Operative Treatment

Plantar fibromas are typically treated non-operatively until they become uncomfortable on a regular basis.
Non-operative treatment includes anti-inflammatory medications, shoe modifications and  the use of a soft-accommodating or well molded custom-made shoe insert.

Operative Treatment

Operative treatment is typically avoided due to the high recurrence rate and difficulty with obtaining clear margins.  Operative treatment involves excising (cutting out) the mass. This is typically done through an incision in line with the length of the foot. The mass is then sent to be examined by the pathologist to confirm the diagnosis.

Potential complications of surgery

Surgery to remove a plantar fibroma can be associated with the usual array of potential complications including:

Recurrence:  These lesions typically involve the overlying skin and dermis as well as the plantar fascia and obtaining clean margins is difficult.  As a result, they have a high recurrence rate and in many cases, recur rapidly.  Some authors advocate complete removal of the plantar fascia to reduce the rate of recurrence.  Surgical margins should approach 2 cm.  Adjuvant radiation therapy may be indicated to reduce the incidence of recurrence.

Wound healing problems: Wound complications are surprisingly common in this type of surgery as the lesions typically involve the overlying epidermis and dermis(3-30+% depending on the size of the mass).  Patients should be aware that skin grafting may be necessary.  The larger the mass the greater the likelihood of a wound problem. A painful scar is always a possibility with surgery on the sole of the foot although it happens uncommonly.

Infection: 2-5% although it may be higher if a wound problem develops

Nerve injury: 2-5% may have injury or irritation to the nerve on the inside of the sole of the foot (medial branch of the plantar nerve)

Blood clot (DVT): These are quite uncommon unless there is a specific risk factor for blood clotting.

Pulmonary Embolism: Potentially very serious, but very uncommon unless there is a specific risk factor for blood clotting

Edited by Matt Buchanan, MD on Dec 12, 2012