Sternal nonunion refers to the failure of the breastbone, or sternum, to heal properly after a surgical procedure that involves dividing it. The failure of the sternum to fuse can lead to discomfort and other health concerns. Various approaches exist to manage and treat this condition, with established pathways for diagnosis and intervention.
Understanding Sternal Nonunion
Sternal nonunion occurs when the two halves of the breastbone do not reunite after a sternotomy, a common surgical incision. A sternotomy involves vertically dividing the sternum to access organs like the heart or lungs for procedures such as coronary artery bypass grafting or valve repair. After this incision, the sternum is typically reapproximated and secured, often with surgical wires, to facilitate bone healing.
The normal healing process for the sternum usually takes 6 to 12 weeks, during which the bone segments fuse. Sternal nonunion is diagnosed when this fusion fails within this timeframe, resulting in persistent separation or instability of the bone fragments.
Factors Contributing to Nonunion
Several factors contribute to sternal nonunion, categorized as patient-related characteristics and surgical considerations. Patient factors include underlying health conditions that impair bone healing, such as diabetes mellitus, which can compromise blood flow and immune function. Obesity increases risk due to greater mechanical stress on the healing sternum and poorer tissue quality.
Other patient factors include chronic lung disease, which can lead to excessive coughing and strain on the chest, and malnutrition, which deprives the body of essential nutrients for bone repair. Smoking hinders healing by reducing oxygen supply to tissues and altering cellular functions necessary for bone regeneration. Advanced age and osteoporosis also contribute due to reduced bone density and slower healing capabilities. Surgical factors include inadequate sternal fixation, such as improperly placed or insufficient wires, which can allow excessive movement at the surgical site. Postoperative infection can disrupt the healing process, while excessive tension on the sternum during closure or wire breakage also impedes proper fusion.
Associated Health Risks
Sternal nonunion can lead to various health risks and complications that impact a patient’s well-being. Chronic pain is a prevalent issue, ranging from a dull ache to sharp, debilitating sensations, often exacerbated by movement or breathing. This persistent pain can severely reduce a patient’s quality of life and ability to perform daily activities.
Chest wall instability, sometimes called “flail chest” in severe cases, is another significant risk, with sternal segments moving independently during respiration. This instability can compromise respiratory mechanics, leading to difficulty breathing and reduced lung function. Patients may experience shortness of breath, especially during exertion, and a decreased capacity for physical activity.
Nonunion also increases the risk of serious infections, such as sternal osteomyelitis (an infection of the sternal bone). In severe instances, infection can spread to the mediastinum (the space between the lungs), causing mediastinitis. Mediastinitis is a life-threatening condition requiring prompt medical intervention, including surgical debridement and prolonged antibiotic therapy. These infections can delay healing and necessitate complex, often multiple, surgical procedures.
Identification and Treatment Options
The identification of sternal nonunion typically begins with a clinical examination, where a healthcare provider may note palpable movement, tenderness, or a clicking sensation around the sternum. Patients often report persistent pain, particularly with coughing, sneezing, or movement of the upper body. Imaging studies are crucial for confirming the diagnosis and assessing the extent of the nonunion.
X-rays can provide initial insights into the sternal alignment and presence of gaps, but computed tomography (CT) scans offer more detailed views, clearly showing the lack of bony union and any associated complications like infection. Magnetic resonance imaging (MRI) may be used in specific cases to evaluate soft tissue involvement or complex infections. Treatment approaches vary depending on the severity of symptoms and the degree of nonunion.
Conservative management, including pain medication and activity modification to reduce stress on the sternum, may be considered for mild, less symptomatic cases. However, surgical intervention is often necessary for significant pain, instability, or confirmed infection. Surgical options include debridement to remove infected or non-viable tissue, followed by sternal refixation using techniques like specialized plates, screws, or additional wires. In some instances, bone grafting may be performed to promote healing and bridge gaps in the sternum. The primary goal of treatment is to stabilize the sternum, alleviate pain, and prevent further complications, improving the patient’s functional recovery.