KÖHLER DISEASE
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Köhler disease is a self-limiting avascular necrosis of the tarsal navicular. It is usually unilateral and most often affects boys around age 4 and also girls around age 5. The navicular is located at the apex of the longitudinal arch of the foot, where it is subjected to repetitive compressive forces during weight bearing. Normally, the navicular is the last bone in the foot to ossify, and irregular ossification is not uncommon, especially in boys. The navicular ossifies later in boys than in girls, and delayed ossification appears to make the navicular more vulnerable to compressive damage.
It has been speculated that compression
of the spongy ossification center of the navicular at a critical phase in its growth
causes the irregular ossification. The compressive forces can occlude the vessels
of the soft ossification center, rendering it avascular. Histologic studies
show the typical changes of avascular necrosis: areas of necrosis, resorption of
dead bone, and formation of new bone.
Clinical Manifestations. The child with Köhler disease walks with a painful
limp, shifting weight to the lateral edge of the foot to relieve pressure on the
longitudinal arch. Pain, tenderness, and swelling develop in the region of the tarsal
navicular.
Radiographic Findings. In most patients, the navicular appears on
radiographs as a thin wafer of bone with patchy areas of sclerosis and rarefaction
and loss of its normal trabecular pattern. These radiographic findings produce the
appearance of navicular collapse. In some patients, the navicular maintains its
normal shape, although with a uniform increase in density and minimal
fragmentation. This may represent a normal, sometimes familial, variant of ossification
that is occasionally seen on the opposite, asymptomatic foot in children with Köhler
disease as well as in asymptomatic individuals.
Treatment and Prognosis. Because the disease is self-limiting, the prognosis
is excellent and no long-term disability or deformity results. The vascularity of
the navicular is adequately supplied by a circumferential leash of vessels, allowing
rapid revascularization. The affected navicular regains its normal shape before
the foot completes growth, and normal ossification is usually completed in 2 years.
Symptomatic treatment is needed for the pain and swelling. Soft, longitudinal arch
supports, a medial heel wedge, and limitation of strenuous activity usually relieve
the symptoms. If the pain is severe or persists, a short-leg walking cast may be
used for 4 to 6 weeks, followed by use of a stiff-soled shoe.
