Kohler's disease is a rare phenomenon occurring in the navicular bone of the foot. It was first described in 1908 by radiologist Alban Kohler.
Typically, this problem develops in children. Various sources give an age range of five to ten years of age. It occurs more commonly in boys then girls in a ratio of six to one. When it does occur in girls it is typically at a younger age then boys and is thought that is due to the fact that bones ossify at a younger age in girls compared to boys. In the vast majority of cases the disease occurs in only one foot.
It falls under the category of avascular necrosis, also referred to as osteochondroses and osteonecrosis, which is destruction of bone due to a decrease in blood supply to that bone. There is no definitive explanation for why this phenomenon occurs, but one put forward is that the navicular bone, being the last bone of the foot to ossify (fully develop), may be pressed against the adjacent bones, the talus and cuneiform bones. As the child ages and becomes heavier, this compression increases and the blood supply to the navicular is thus cut off, resulting in the inability of the navicular bone to fully form.
SYMPTOMS OF KOHLER'S DISEASE
Typically the parent will notice that their child is limping. Upon questioning the child, there will be no history of trauma, although trauma can certainly play a role in the onset of Kohler's disease. Examination of the foot will reveal swelling and tenderness in the area of the navicular bone, which is on the top inside portion of the foot near the top of the arch.
DIAGNOSING KOHLER'S DISEASE
In instances where there is no history of trauma, in a child, Kohler's disease has to be suspected based on the location of pain. Confirmation of the condition is usually through an x-ray. It is recommended that x-rays of both feet be taken, in order to compare the appearance of the navicular bone in each foot.
Looking at the yellow arrow on the x-ray one can see how different the navicular bone appears compared to the same bone on the other foot. The growth of the affected bone has been delayed. The affected bone itself is irregular in appearance. Parts of the bone may be sclerotic (more dense in appearance) and there may also be small fractures in the bone.
Serial x-rays, taken over a period of several months can be very helpful in observing the progress of the healing process.
TREATMENT OF KOHLER'S DISEASE
Kohler's disease is thought to be a self limiting condition meaning that with proper treatment the problem will resolve. The purpose of the navicular bone with the tibialis posterior tendon inserting into it is to support the arch. The collapsing of the arch can be one of the causative factors in the onset of this condition. Treatment, therefore, is to relieve the stress on the navicular bone. In mild cases nothing more than a soft orthotic may be necessary to support the navicular bone and allow it to heal. Parents need to warn their children that the orthotic has to be worn all the time. Running around the house barefoot, for example, will only worsen the symptoms.
In more severe cases anti-inflammatory medication may be given on an as needed basis. More severe cases may also require a cast rather than an orthotic. The cast needs to be applied in such manner to force the foot into mild supination in order to take the strain off of the navicular. This can be a weightbearing cast. Treatment is usually for six to eight weeks.
In cases where the pain has not resolved after a couple of months, an MRI may be necessary to rule out other conditions such as a tarsal coalition. Bone scans are generally of no value in this condition as there are too many false positives due to the ossification centers in the developing bones. Kohler's disease is generally not a surgical problem.