Tarsal boss is characterized by a painful prominence on the top of the midfoot. It is often aggravated by constrictive footwear. The underlying problem is a prominent bone spur that may form in response to arthritis in one of the midfoot joints. Treatment is usually non-operative aimed at avoiding pressure overlying the prominent bone. Taking care to ensure that the tongue of the shoe is not tied tightly and that there is an associated soft padding over the boney prominence can greatly improve symptoms. In addition, stiff soled shoes can be helpful with respect to symptoms. Occasionally, surgical removal of the bone spur or even fusion of the underlying arthritic bone joint may be necessary.
A painful lump on the top of the foot is the main symptom of a tarsal boss. The lump is usually located over the mid part of the foot. It may create pain with constrictive footwear. It may also be associated with an aching pain in the mid foot as there is a correlation between the presence of a prominent tarsal boss and midfoot arthritis.
An examination will demonstrate a lump on the top (dorsal aspect) of the midfoot. This lump is often hard from the underlying bone. This differentiates a tarsal boss from a ganglion, which is a lump that is softer due to the fluid filled sac that causes it.
Plain x-rays of the foot will usually reveal a bone spur in the top part of the midfoot. (figure 1)
Figure 1-Foot X-Ray showing Tarsal Boss (midfoot Bone Spur)
This is usually associated with the tarsal-metatarsal joint. There may also be some wear and tear arthritis of this joint (midfoot arthritis), which leads to the bone spur. Essentially, the bone spur creates the prominence, which leads to the localized discomfort from the constrictive shoe.
Most tarsal boss presentations can be treated non-operatively. Creating a soft area in the shoe, and not tying shoes quite as tightly over this area will often lead to resolution of these symptoms, although the prominence on the top of the foot will not be fully resolved. In addition, shoes with an associated stiff sole can be helpful as this will put less force through the mid part of the foot.
Occasionally the prominence of the bone spur or the associated pain from the underlying midfoot arthritis the arthritis of the tarsal-metatarsal joint will necessitate surgical intervention. In this instance, there are two surgical procedures that can be preformed:
Removal of the prominent dorsal bone spur
A fairly straight forward operation can be preformed to identify the bone spur and remove it. This is associated with a relatively quick recovery time. However, usually the underlying reason why the bone spur occurred (wear and tear in the tarsal-metatarsal joint) is not addressed. And therefore, there is a higher likelihood that the bone spur will reoccur over time.
Fusion of the midfoot joints
If the bone spur is a product of significant of midfoot arthritis, which is also symptomatic, a fusion of this joint (midfoot arthrodesis) may be beneficial. This involves preparing the joint, fixating it with screws or a plate, and keeping off the foot for a 6-8 week period, until adequate fusion has occurred. This type of surgery is much more involved than a simple removal of the bone spur and may be associated with the typical complications that can occur with fusion surgery.
Updated by Stephen Pinney, MD on May 11th, 2013