Introduction
Avascular necrosis of the foot's navicular bone is how Alban Kohler first described Kohler disease in 1908. Only pediatric individuals are affected with Kohler disease. Although the exact cause is unknown, it is believed that the navicular bone's compression before ossification is to blame. Avascular necrosis results from irregular blood flow caused by this. Males between the ages of four and seven are the ones most likely to have Kohler illness.
Although Kohler disease is mainly unilateral, one study in the literature discovered that 25 percentage of cases are bilateral. Patients frequently complain of medial-sided foot pain, medial foot edema, and a limp. The navicular will display the typical signs of avascular necrosis (AVN), such as sclerosis, fragmentation, and flattening, on plain films. With a good prognosis, Kohler disease is a self-limiting condition.
Sometimes Kohler disease has no symptoms. Yet, patients frequently complain of dorsomedial midfoot pain when they visit their pediatrician. The patient may exhibit point discomfort over the navicular during a physical examination, along with or without redness, warmth, and edema. The patient may exhibit an antalgic limp ( an abnormal pattern of walking secondary to pain) when asked to walk, walking on the outside of their foot.
What Is the Etiology of Kohler Disease?
The navicular bone has two blood vessels feeding it. The dorsal aspect of the bone is supplied by a branch of the dorsalis pedis artery, and the medial plantar branch of the posterior tibial artery provides the plantar blood supply. The medial and lateral thirds of the bone are supplied by branches that emerge from the navicular, where the dorsal and plantar blood supplies enter.
This results in an avascular zone in the center third of the bone.
On the dorsal, plantar, medial, and lateral surfaces of the navicular bone, there are vascular foramina that assist in supplying blood to this avascular region. Yet, 97% of adult vascular foramina measured less than one millimeter in a study of 100 cadaveric navicular bones. Theoretically, any compression of these tiny vascular foramina could cause a reduction in blood flow and increase the risk of avascular necrosis in the navicular bone.
The navicular is hypothesized to be under aberrant tension in Kohler disease. The navicular bone in children ossifies last among the tarsal bones. It ossifies between the ages of 18 and 24 months in girls and 30 to 36 months in boys. According to this view, the navicular bone is weaker than the other tarsal bones because of its delayed ossification. The navicular might become crushed as the kid develops and gains weight between the already osseous talus and cuneiform bones. The core spongy bone's perforating arteries are compressed due to the compression of the non-ossified navicular, which may cause ischemia and, eventually, avascular necrosis.
What Is the Epidemiology of Kohler Disease?
Because only some Kohler disease patients exhibit symptoms, the condition's incidence still needs to be fully understood. According to one study, Kohler illness affects two percent of all children. Males are five times more likely than females to have Kohler illness, which most frequently affects kids between the ages of four and seven.
What Is the Histopathology of Kohler Disease?
A bone biopsy is not necessary to diagnose Kohler disease and is not advised unless it is required to rule out infection or cancer. Histologically, Kohler disease resembles other types of avascular necrosis. Avascular necrosis is characterized histologically by dead trabeculae with empty lacunae that will stain more deeply than healthy bone. There will be cystic alterations and enlargement of the lacunae. The marrow of the bone, which exhibits fat necrosis and calcium deposits, is known to be a more sensitive avascular necrosis indication than the bone itself.
How Is Kohler Disease Evaluated?
The preferred imaging method for diagnosing Kohler disease is plain radiography pictures. With the bone collapse, the navicular will appear paper-thin. The lack of the trabecular pattern will cause the bone to seem fractured. Bone sclerosis will seem spotty, and radiodensity will rise. Soft tissue edema can also be visible on plain radiographs surrounding the afflicted navicular bone. Although advanced imaging tests like CT (Computed Tomography) and MRI (Magnetic Resonance Imaging) are unnecessary for diagnosis, they can be if the patient's symptoms do not improve after treatment. While navicular sclerosis in asymptomatic patients may be congruent with a normal variety, it's crucial to link radiographic results to clinical suspicions.
Basic labs like a complete blood count, C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR) are required when an infection is suspected. It is necessary to conduct additional diagnostic tests if any of these are elevated.
What Is the Treatment for Kohler Disease?
Patients should be referred to a pediatric orthopedic surgeon for additional assessment if Kohler disease is suspected. Kohler disease is managed conservatively. Although it has not been demonstrated that NSAIDs can shorten the duration of illness symptoms, they can be used to lessen symptoms. Patient's discomfort can be reduced by immobilizing them for four to six weeks in a short-leg walking cast. It is unknown and frequently depends on the surgeon how weight-bearing versus non-weight-bearing casts affect a patient. Offloading orthotics for symptom reduction has been mentioned in some reports.
Nevertheless, it doesn't seem like orthotics reduce the length of the symptoms. Surgery is not warranted in Kohler illness. Medical professionals should investigate a different diagnosis if symptoms do not get better.
What Is the Differential Diagnosis for Kohler Disease?
In children, osteomyelitis is frequently misdiagnosed as Kohler disease. White blood cells, CRP, and ESR are simple blood tests that can assist in distinguishing between the two diagnoses. A high index of suspicion for infection should be held if a youngster has increased ESR or CRP levels. Elevated inflammatory markers are not expected in Kohler disease, and they are also not expected in pediatric patients. Bone aspiration, bone biopsy, or blood cultures can be necessary if an infection is suspected.
What Is the Prognosis for Kohler Disease?
The prognosis for Kohler illness is excellent, and there have been no reports of long-term symptoms or disability in children with Kohler disease up to this point. In the six to forty-eight months following the onset of symptoms, radiographs will improve. Symptoms usually go away without casting in six to nine months. A review of case reports revealed that patients wearing plaster casts experienced pain relief on average after three months. Orthopedics with arch support was reported to reduce local discomfort. However, the average duration of symptoms was seven months.
Conclusion
An interprofessional team is the best option for Kohler disease management. Although the primary care physician may initially identify the issue, an orthopedic surgeon will ultimately manage it. A radiologist, physiatrist, and orthopedic nurse can be on the team. The illness is often treated conservatively with regular monitoring.
