A bone infarct is a medical condition where an area of bone tissue within the marrow dies due to a disruption in its blood supply. This interruption prevents the bone from receiving the necessary oxygen and nutrients. It is a form of osteonecrosis, which broadly refers to the death of bone tissue.
Understanding Bone Infarcts
A bone infarct involves localized tissue death within the medullary cavity, the inner part of the bone containing marrow. This occurs when the blood supply to a section of bone is interrupted, leading to ischemia and cellular death. Unlike avascular necrosis, which typically affects the subchondral bone near joints, a bone infarct is usually located away from the joint surface in the metaphysis or diaphysis of long bones, such as the femur or tibia. The affected area develops a central necrotic core surrounded by a reactive zone. This condition often remains asymptomatic, meaning it causes no noticeable symptoms.
Causes and Risk Factors
Various factors can disrupt the blood flow to bone, leading to an infarct. Trauma, such as fractures or dislocations, can directly damage blood vessels.
Certain medical conditions also increase the risk, including sickle cell disease, which can cause abnormal red blood cells to block small vessels. Conditions like Gaucher’s disease, systemic lupus erythematosus, and pancreatitis are also associated with bone infarcts.
Long-term use of corticosteroids is a significant risk factor, possibly due to their effects on lipid metabolism. Lifestyle factors, such as excessive alcohol consumption and smoking, can also impair blood supply to bones. Decompression sickness, often seen in divers, can cause nitrogen bubbles to block blood vessels, and treatments like radiation therapy and chemotherapy may also contribute.
Recognizing the Signs
Many bone infarcts are discovered incidentally during imaging studies, as they often do not cause symptoms. When symptoms occur, pain is the primary sign, typically localized to the affected bone.
This pain can range from mild to severe and may be constant or activity-related. Pain might be experienced in the thigh, shin, or upper arm if long bones are affected.
Symptoms are more likely to arise if the infarct is large, located in a weight-bearing bone, or progresses to affect the subchondral bone near a joint. Early symptoms might include intermittent pain and stiffness.
Diagnosis and Identification
Medical professionals identify bone infarcts through patient history and advanced imaging studies. A physical examination often does not reveal specific signs.
X-rays may show changes like sclerosis or calcification in later stages, but they often appear normal in early phases.
Magnetic Resonance Imaging (MRI) is the most sensitive and definitive imaging technique for detecting bone infarcts early. MRI can reveal characteristic patterns in the bone marrow, such as a “double-line sign” on T2-weighted images.
Computed Tomography (CT) scans provide more detail than X-rays, showing the extent of bone sclerosis and calcification, but are less sensitive than MRI for early detection.
Treatment Approaches
For asymptomatic bone infarcts, specific treatment is often unnecessary, though regular monitoring may be recommended. When symptoms are present, managing pain is a primary goal, involving over-the-counter pain relievers or prescription medications.
Addressing underlying causes is also important, which might include managing conditions like sickle cell disease or discontinuing corticosteroids if possible.
Conservative measures like rest and physical therapy can help maintain joint function.
Surgical options are rarely needed for pure bone infarcts. Surgery is typically reserved for cases that progress to avascular necrosis or cause significant symptoms or joint damage, and may include procedures like core decompression, bone grafting, or joint replacement.
Bone Infarcts vs. Avascular Necrosis Explained
While both involve bone tissue death from interrupted blood supply, bone infarcts and avascular necrosis (AVN) differ significantly in their location and clinical progression.
Bone infarcts, occurring within the medullary cavity, are often asymptomatic and typically remain stable without leading to structural collapse or joint destruction.
In contrast, AVN affects the subchondral bone beneath a joint’s cartilage. AVN is often symptomatic, causing pain and potentially progressing to joint surface collapse.
This can lead to degenerative arthritis and may require surgical intervention. While a bone infarct can sometimes precede AVN, many do not progress to affect the joint surface or cause severe complications.