Management of Rib Avascular Necrosis Complicated by Osteomyelitis in a Patient With Sickle Cell Anemia

Avascular necrosis of bone is the death of osseous tissue because of a blood supply interruption. Several etiologies have been identified to cause osseous tissue necrosis, including trauma, chemotherapy, thermal injury, smoking, alcohol, and intraosseous compression. Sickle cell anemia is another disease known to cause bone necrosis. Avascular necrosis of bones occurs at different rates and magnitudes throughout the body; the knee and hip joints are the most common regions affected by avascular necrosis.^[1] Rib necrosis is considered rare, with a paucity of cases reported. Radiotherapy is a common etiology that has been reported to cause rib necrosis.^[2–4]

Chest pain is a dreadful presentation that includes serious differentials like myocardial infarction, aortic dissection, and esophageal rupture.^[5] Appropriate diagnosis and identification are crucial for the management of chest pain. Cardiac enzymes, electrocardiograms, and imaging modalities like x-ray or computed tomography (CT) are important tools that can rule out or confirm the pain's etiology.^[5] Furthermore, history-taking can create a complete picture for the management team.

Red blood cells in sickle cell disease are predisposed to clumping and blocking blood vessels. A single nutrient artery usually supplies bones; any compromise to the blood supply will result in avascular necrosis.^[6] Regardless of the site, surgical debridement of necrotic tissue remains the mainstay of management in symptomatic cases, and then, depending on the site, a bone graft might be added to give structural support.

The necrosed bone will act as a foreign body, which creates a suitable environment for different kinds of bacteria to inhabit and hence predisposes to osteomyelitis.^[7] Bone can get infected through bacteremic seeding from a distant source of infection (hematogenous route), contiguous spread from nearby tissue, or direct inoculation of bone from trauma or surgery.^[7] In susceptible individuals, avascular necrosis can progress to osteomyelitis, rendering management more difficult. Complete infected tissue debridement and postsurgical patient monitoring are essential for smooth patient recovery, prevention of reinfection, and avoidance of major complications. Herein, we present the rare presentation and management of rib osteonecrosis.

The study was reviewed and approved by the Institutional Review Board at King Faisal Specialist Hospital in Riyadh, Saudi Arabia. Written informed consent was obtained from the patient for publication of this case report and accompanying images.

A 45-year-old man known to have sickle cell anemia presented with left lateral chest wall pain that he had experienced for the past 2 weeks. The pain was followed by swelling, fever, and tenderness over the area of the left sixth rib for 1 week. He was initially seen in the outpatient clinic, and because the patient had no history of trauma, radiotherapy, or malignancy, infection was considered the primary etiology of the pain. He was then prescribed an oral antibiotic; however, the patient did not show improvement.

CT imaging (Fig. 1) showed a 91 × 61 × 71-mm soft tissue structure at the left anterolateral chest wall, centered over the anterior aspect of the sixth rib with bony destruction and a sixth rib fracture. The structure also expanded to the subcutaneous tissue and the pericardial fat pad. It was seen in close contact with the pericardium, surrounded by fat stranded with a few tiny air bubbles within. These findings were in line with inflammation and infection, greatly suggestive of osteomyelitis and rib necrosis.

The patient was taken to the operating room, placed supine under general anesthesia, and underwent endotracheal intubation. A skin incision was made over the swelling. When the underlying muscle was reached, malodorous pus was released in large amounts, which was then aspirated for microbiologic studies (Fig. 2). In the surgical field rib avascular necrosis was clear, and the surgeon decided on the debridement of all necrotic tissues in addition to removing the affected segment of the sixth rib. The affected area was irrigated thoroughly with normal saline and hydrogen peroxide. Patient hemostasis was secured, and a silicon drain was left in the operated-on area. The surgery was concluded with closure with Vicryl 1 for the muscle and skin staplers. Microscopic histopathology revealed suppurative inflammation with abscess formation in muscle. Fat necrosis with necrotic bone was also present and was negative for malignancy. There was no visible thrombosis on the histologic slide. The patient's postoperative recovery was smooth, and he started becoming afebrile. The drain was removed on the third day after the surgery. The patient was started on linezolid 600 mg for 2 weeks postoperatively.

Rib avascular necrosis is rare, and secondary osteomyelitis has rendered its management more difficult. Because the patient showed no improvement on antibiotics and because of the presence of necrotic bone on imaging, surgery was indicated. From a differential diagnosis point of view and given the history of sickle cell anemia with no cardiovascular risk factors, acute chest syndrome is the number one differential.^[8] However, the CT scan successfully ruled out acute chest syndrome. Furthermore, a tumor like Ewing sarcoma was suspected on imaging because of the lytic nature of the lesion; however, because of the patient's presentation, pyrexia, and risk factors, it was ruled out. Unlike the x-ray, the CT showed a better view of the bone in relation to the inflammatory tissue. Furthermore, it was the superior modality for diagnosis. A definitive diagnosis was made when the pathology report showed suppurative inflammation and abscess formation along with fat and bone necrosis. Although radiotherapy was reported as the most common cause of rib necrosis, there is a paucity of literature on the susceptibility of rib necrosis in patients with sickle cell anemia.

The surgical management of rib avascular necrosis differs from that of necrosed bones at other sites. No bone grafts or core decompression are required in treating the disease due to the anatomic position and structure of the rib; rib resection and necrotic tissue debridement were sufficient.

Secondary osteomyelitis could be managed by both conservative and surgical approaches. Conservative management involves using antibiotics empirically if an infecting agent is suspected or definitively if a culture is present.^[9] Surgical management is indicated when the osteomyelitis is refractory to antibiotic treatment and requires debridement of necrotic bone, when an abscess is formed, after trauma to fix fractures, to remove an infected prosthetic device if present, or when in need of revascularisation due to poor blood supply.^[9,10]

In conclusion, rib avascular necrosis is a very rare disease that thoracic surgeons treat. The lack of distinct clinical indicators and low occurrence can lead to misdiagnosis and mismanagement. Rib osteonecrosis is a rare pathology and must be included in the differential diagnosis of chest pain. In this case, the superimposed osteomyelitis and history of sickle cell anemia rendered it difficult to manage. We found that surgical debridement of necrotic bone and close postsurgical follow-up were important for successfully managing the disease.