Rare radiograph finding: Kohler disease

A previously healthy 3-year-old male presented to the emergency department with one day of refusal to bear weight secondary to left foot pain. No known trauma. No fever or recent illness. On physical examination, he had point tenderness over the proximal dorsal left foot with minimal swelling. No erythema or warmth. He would only crawl, which was abnormal per his mother. Plain radiographs of the left foot revealed a thin, fragmented and sclerotic navicular bone (Figures 1,2).

Figure 1 Oblique view of left foot. Arrow pointing to flatten and sclerotic navicular bone.

Figure 2 Lateral view of left foot. Arrow pointing to flatten and sclerotic navicular bone.

The patient received a diagnosis of Kohler disease. Kohler disease is a condition impacting the pediatric population that is characterized by idiopathic avascular necrosis of the navicular bone (1,2). Kohler disease was first described by radiologist Alban Kohler in 1908 (2,3). Children with Kohler disease typically present with limping, reluctance to apply pressure to the foot, pain and swelling without a history of injury or infectious signs. Radiographs demonstrate sclerosis, flattening, and fragmentation of the navicular bone. Kohler disease is most commonly seen in males ages 4 to 7 years old (2,3). Our patient was 3 years old, suggesting this pathology is possible in a younger population as well.

It has been hypothesized Kohler disease may be secondary to repetitive trauma inflicted on the navicular bone by the adjacent tarsal bones, compromising the vascular supply (1,2). The navicular is the last tarsal bone to ossify and thus is vulnerable to getting squished between the harder, already ossified talus and cuneiforms (1,3). As a result, the blood vessels supplying the navicular bone are compressed, which interrupts blood supply and leads to ischemia of the central spongy bone. The navicular bone ossifies later in males than females (18 to 24 months old in females, 30 to 36 months old in males), which explains the increased incidence of Kohler disease in males (1). The dual blood supply of the navicular bone likely also contributes to disease development (3). The medial tarsal branch of the dorsalis pedis artery supplies the medial aspect of the navicular. The medial plantar branch of the posterior tibial artery supplies the lateral aspect of the navicular. In the central navicular, there is a region of watershed blood supply. This zone of relative hypovascularity results in an increased risk of ischemia and thus avascular necrosis as seen in Kohler disease and has also been described in prior literature in association with navicular stress fractures and poor healing (3,4).

Kohler disease is managed nonoperatively (1). Once diagnosed, patients should be referred to pediatric orthopedics for further management. Non-steroidal anti-inflammatory drugs (NSAIDs) can be used for pain relief but do not shorten the duration of the disease (3). Literature has demonstrated earlier symptomatic improvement in patients who were treated with immobilization in a short leg walking cast (5). Further investigations are necessary to determine the efficacy of weight-bearing casts compared to non-weight-bearing casts in regards to shortening the duration of Kohler disease. Offloading orthotics, such as soft arch supports, can also be used to provide symptomatic relief as either the sole therapy modality or preceding and/or proceeding treatment with a short leg cast (3).

Kohler disease has a very favorable prognosis. Both symptoms and radiographs should start to show improvement in around six months from onset (3). All patients recover excellent function in the foot and have complete radiographic resolution in an average of two to three years (3). There are no reports to date of chronic symptoms or disability resulting from Kohler disease (1,3,5). Significant pain persisting longer than 6 months despite proper treatment likely suggests a separate or adjacent underlying condition, for example, tarsal coalition, and would necessitate further work up such as computed tomography (CT) or magnetic resonance imaging (MRI).

Pediatric orthopedics placed our patient in a walking boot for six weeks. At follow-up, the patient was pain free and ambulating at baseline. Kohler disease is rare but should be considered in the differential diagnosis for children with refusal to bear weight, especially in cases without preceding injury and without evidence of infection or malignancy. Recognition of this diagnosis may prevent additional unnecessary tests in an emergency department or clinic setting.

Acknowledgments

Funding: None.

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References

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