What is Kohler Disease?
Kohler disease, first identified by Alban Kohler in 1908, involves the decay or “avascular necrosis” of a specific foot bone called the navicular bone due to lack of blood supply. This condition is found only in children, with its root cause still not completely clear. It’s thought to be caused by the pressure on the navicular bone before it fully hardens, leading to irregular blood flow and eventually, avascular necrosis. Kohler disease is typically seen in boys aged 4 to 7 years old.
Usually, this condition affects just one foot, but there have been instances where it affects both feet, amounting to about 25% of all cases. Children with this condition generally experience pain on the inside of the foot, swelling of the foot’s inner edge, and/or may start to limp. When examined with simple X-ray imaging, the navicular bone shows typical signs of avascular necrosis such as hardening, splintering, and flattening.
The good news is that Kohler disease is self-limiting, meaning it will gradually resolve itself over time, and it has an excellent chance of full recovery. There hasn’t been any reported case of Kohler disease leading to long-term foot problems either clinically or as seen on X-ray.
What Causes Kohler Disease?
The navicular bone in your foot gets its blood supply from two sources. One source comes from a branch of the dorsalis pedis artery, supplying the top part of the bone, and the other comes from the medial plantar branch of the back tibial artery, supplying the underside of the bone. These blood supplies branch out to cover the inner and outer parts of the bone. However, this results in a zone in the middle third of the bone that does not receive a direct supply of blood. Tiny passages called vascular foramina help get blood to this zone, and these can be found on all sides of the navicular bone. Despite this, in a study of 100 cadaveric navicular bones, 97% of these passages were smaller than 1 millimeter in adults, suggesting that these small passages could be easily compressed, leading to decreased blood flow and potentially putting the navicular bone at risk of dying due to lack of blood, a condition known as avascular necrosis.
Kohler disease, which affects the navicular bone, is thought to be caused by abnormal strain on the bone. For children, the navicular bone is the last of the tarsal bones (the bones in the foot) to harden, a process called ossification. It hardens earlier in girls than in boys, usually between 18 and 24 months in girls and 30 to 36 months in boys. Since the navicular bone hardens slower than most of the other tarsal bones, it is weaker. As a child grows and puts on more weight, this can put pressure on the navicular bone, causing it to be squished between the other bones in the foot that have already ossified. This pressure can interrupt the blood supply in the bone, potentially leading to lowered blood and oxygen supply, also known as ischemia, and then avascular necrosis.
Risk Factors and Frequency for Kohler Disease
Kohler disease is a condition that isn’t completely understood in terms of how often it occurs. This is largely due to the fact that not everyone with Kohler disease shows symptoms. However, one study suggests that about 2% of all children have Kohler disease. It’s been observed that this condition is five times more common in boys than girls. It often appears in kids who are between 4 to 7 years old.
Signs and Symptoms of Kohler Disease
Kohler disease is a foot condition that may not always cause symptoms. However, when it does, the person usually experiences pain in the central part of the foot towards the top and inside. When examined by a doctor, the painful area of the foot, called navicular, may be tender when pressed or touched. It may also show signs of inflammation such as being warm to the touch, red, or swollen. Also, in an effort to ease discomfort, someone with Kohler disease may walk with a distinct gait where they put more weight on the outer side of their foot.
Testing for Kohler Disease
In diagnosing Kohler disease, which affects the foot, X-rays are typically used. They can show if the navicular bone (one of the bones in the foot) has become very thin or collapsed. The bone may look broken up and the natural mesh-like structure within the bone can disappear. There can also be areas within the bone appearing denser than normal. Swelling around the affected bone might be visible too.
More advanced imaging like CT scans or MRI scans isn’t usually needed to diagnose Kohler disease. However, they can be helpful if the symptoms don’t improve with the first treatment. Keep in mind that the increased density can sometimes happen in people without symptoms, so the results of the X-ray should be compared with the symptoms the patient is experiencing.
If an infection is suspected, the doctor may ask for basic blood tests. They may include a complete blood count, or checking for C-reactive protein and the erythrocyte sedimentation rate. These tests measure inflammation and infection in the body. If any of these tests show high levels, more tests might be needed.
Treatment Options for Kohler Disease
If a doctor thinks a child might have Kohler disease, which is a rare bone disorder, they will usually recommend seeing a children’s bone specialist (pediatric orthopedic surgeon) to confirm the diagnosis and manage the condition.
Treatment for Kohler disease is usually simple and done without surgery. Non-steroidal anti-inflammatory drugs (NSAIDs), which are commonly bought over the counter to treat pain and inflammation, can be used to help ease symptoms. However, it’s important to understand that these medicines won’t necessarily speed up recovery.
The child might also wear a small leg cast that allows them to walk, which is used for about 4-6 weeks. This helps to relieve symptoms faster. There has been some debate about whether a walking cast (one that the child can put weight on) is better than a non-walking cast, but what’s best often depends on the surgeon’s decision. Some people have found relief from symptoms by using offloading orthotics, which are custom shoe inserts that help distribute weight evenly across the foot. However, these orthotics are not known to quicken recovery time.
There is no need for surgery when it comes to treating Kohler disease. If the symptoms don’t start to show signs of improving, the doctor should think about other possible causes of the symptoms. Both the symptoms and X-ray images of the foot should begin to show signs of getting better after about six months.
What else can Kohler Disease be?
Kohler disease, often confused with osteomyelitis in children, can be distinguished through basic lab tests such as white blood cell (WBC) count, C-reactive protein (CRP) level, and erythrocyte sedimentation rate (ESR). If these levels are high, it could be a sign of infection. However, in Kohler disease, these inflammatory markers are typically not elevated. If infection is suspected, further tests such as a bone aspiration, bone biopsy, or blood cultures might be necessary.
What to expect with Kohler Disease
Kohler disease generally has a great outcome. So far, there have not been any reports of children with Kohler disease experiencing long-term issues or disability. Medical imaging, such as x-rays, tend to show improvement between 6 and 48 months from when the symptoms first appear. Without any sort of cast, symptoms typically clear up in about 6 to 9 months.
In review of several case reports, it was found that patients that were treated with plaster casts (which ideally prevent them from placing weight on the affected area), they typically became pain-free around the 3-month mark. Using arch support orthopedics, which are specially designed shoe inserts, was shown to lessen local pain. However, it was also found that symptoms lasted around 7 months when using this method of treatment.
