Kohler Disease


Background

In 1908, Köhler first described the disease named in his honor. [1 This clinical entity belongs to a group of conditions called osteochondroses, which have been reported since 1903. Approximately 40 different osteochondroses have been described in the literature. In these self-limited diseases, there is avascular necrosis (AVN) of primary or secondary centers of ossification; almost all of the epiphyses, apophyses, and small bones can be implicated. [2 In Köhler disease, AVN of the navicular bone occurs.

The etiology of these conditions is not well known, but vascular accidents, coagulation anomalies, and heredity have been implicated. [3 The most common osteochondroses are KienbockFreiberg, and Panner diseases.

Surgery is not indicated for Köhler disease; treatment is nonoperative (see Treatment).

Pathophysiology

Vascularization of the navicular bone occurs in two ways and is identical in adults and in children. A branch from the dorsalis pedis artery crosses the dorsal surface of the navicular and gives off three to five branches. Some small branches come from the medial plantar artery to supply the plantar surface. These blood vessels create a dense network around the bone and come from the perichondrium toward the center of the cartilage. Less commonly, a single dorsal or plantar artery is found in anatomic specimens.

Köhler suggested that the changes in this disease might be the result of an abnormal strain that acts on a weak navicular, but a definitive explanation has not been found. Of the theories put forward to explain the nature of this lesion, a more satisfactory one is a mechanical basis that is associated with a delayed ossification. [4]

The navicular is the last tarsal bone to ossify in children. This bone might be compressed between the already ossified talus and the cuneiforms when the child becomes heavier. Compression involves the vessels in central spongy bone, leading to ischemia, which then causes clinical symptoms. Thereafter, the perichondral ring of vessels sends the blood supply, allowing rapid revascularization and formation of new bone. The radial arrangement of the vessels of this bone is of great importance in explaining why the prognosis of this lesion is always excellent.

In his original paper, Köhler also reported a single instance of an osteochondrosis of the primary patellar ossification center; this clinical entity has been rarely reported in the years since. Dharamsi and Carl reported a case of isolated bilateral Köhler disease of the patella in a male athlete aged approximately 7 years. [5]

Etiology

The etiology of Köhler disease, like those of the other osteochondroses, is unknown, but the condition is thought to result from compressive stress-related injury at a critical time of growth. [6Vascular insults, retarded bone age, and genetic predilection have also been implicated. [7]

Epidemiology

Köhler disease is a rare condition thought to occur in less than 2% of the population. [6However, no accurate epidemiologic figures are currently available for this condition. The disorder can begin very early, after age 2 years, but it is more frequent in children aged 5-10 years. Köhler disease is far more common in boys than in girls; however, girls with this condition are often younger than boys with the disease are. This is probably due to the onset of ossification in girls, which occurs at age 18-24 months, whereas in boys, ossification occurs at age 24-30 months.

Prognosis

The evolution of the x-ray appearance in Köhler disease is variable. Normal x-rays may be obtained 6-18 months following onset. At adulthood, the navicular bone is expected to be normal. Patients recover excellent function. 


History and Physical Examination

In this uncommon condition, children present with an antalgic limp and local tenderness of the medial aspect of the foot over the navicula. The child can walk with an increased weight on the lateral side of the foot. Frequently, there is swelling and redness of the soft tissues.



Medical Therapy

A walking short leg cast with toe extension is recommended. Total cast time is approximately 6-8 weeks. The cast is better in moderate varus (10-15º) that is associated with moderate equinus (10-20º). In this position, the navicular is relaxed from posterior tibialis strain. Arch supports can be prescribed after the cast period and used for an average of 6 months. In mild cases, soft arch supports may be the only treatment necessary.

Surgery is not indicated for Köhler disease. 

Complications

In 1984, Ertel and O'Connell reported a case of acquired talonavicular coalition that followed avascular necrosis (AVN) of the tarsal navicular bone. [14This complication is very rare.

Long-Term Monitoring

In treated patients, symptoms may last less than 3 months. [10 In untreated patients, symptoms may be present for 15 months. Because immobilization in a short leg cast decreases the duration of symptoms, treating all patients for at least 6 weeks is recommended.

If pain persists after a 6-week period of casting, a new cast must be applied for 6 supplementary weeks. [15 If pain does not disappear after the cast period, other causes of foot pain, including talar coalition or an accessory navicular, should be investigated. 

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