Accessory Navicular Syndrome
In the child, the bones of the foot
occasionally develop abnormally and an extra bone called an accessory
navicular is present towards the inside of the foot, in front of
the ankle. This bone is present in approximately 10% of the general
population but not large enough to cause symptoms in the majority
of these individuals.
||The pictures above are XR's of
the foot in an adolescent with an accessory navicular.
The extra bone is circled in red in the XR on the right.
The extra bone lump present in childhood can be quite uncomfortable
because it rubs on shoes. In addition, the feet associated with
the accessory navicular are invariably flat. The flat-footedness
associated with the accessory navicular usually brings the child
If the child is active and involved in various athletic activities,
this will aggravate the inflammation of the tendon that attaches
to the accessory navicular. This tendon is called the posterior
tibial tendon and is responsible for maintaining the strength of
the arch of the foot. Treatment of the accessory navicular begins
with rest. Rest may include activity modification or temporary immobilization
in a boot or a brace.
Once the inflammation subsides the foot needs to be supported. The
support consists of a specially designed orthotic arch support.
Occasionally, the orthotic will often dig into the edge of the accessory
navicular bone under the arch of the foot. This is very uncomfortable.
For this reason the orthotic support needs to be carefully made.
The orthotic support will help control (but not cure) the flat foot
and will often decrease the inflammation on the navicular.
Once the navicular inflammation has lessened it is not necessary
to perform surgery unless the foot becomes progressively flatter
or continues to be painful. For these children, surgery can completely
correct the problem by removing the accessory navicular bone and
tightening up the posterior tibial tendon that attaches to the navicular
bone. The strength of this tendon is integral to the success of
this surgery as well as the arch of the foot. Following surgery
the child is able to begin walking on the foot (in a cast) at approximately
two weeks. The cast is worn for an additional four weeks. A small
soft ankle support brace is then put into the shoe and worn with
activities and exercise for a further two months.