Image Quiz

A Vertebral Complication Associated with Pancreatitis in a Fifty-Year-Old Woman (continued)

Answer: Vertebral osteonecrosis.

A technetium-99m-methylene diphosphonate bone scan showed areas of intensely increased activity in the body of the twelfth thoracic vertebra (Fig. 1). Orthopaedic consultation was sought, and magnetic resonance imaging of the spine was performed (Figs. 2-A and 2-B). An area of altered signal intensity was observed in the posterior part of the twelfth thoracic vertebra. The signal intensity was low on T1-weighted images and high on T2-weighted images. These signal changes were consistent with increased water content but were rather nonspecific otherwise. An open biopsy of the twelfth thoracic vertebra was performed, and a clear liquid with free-floating fatty droplets was aspirated. Cultures of the fluid specimens demonstrated no growth of microorganisms, including Mycobacterium tuberculosis. The amylase level in the aspirate was measured to be 32,000 IU/L (normal, <128 IU/L), and no malignant cells were found. Histologic evaluation of the biopsy specimen showed fat necrosis of the bone marrow (Fig. 3). The low-back pain worsened after the biopsy. A repeat magnetic resonance imaging scan showed progression of the primary pathologic changes and slight displacement of the spinal cord, with signal changes in the twelfth thoracic, first and second lumbar, and first sacral vertebrae. Endoscopic retrograde cholangiopancreatography and cannulation of the accessory pancreatic duct were performed. Cytologic evaluation of the pseudocystic aspirate revealed malignant cells. The decision was made to perform a pancreatoduodenectomy (a Whipple operation). Pathologic investigation of the resected material revealed adenocarcinoma of the dorsal portion of the pancreas. The patient's condition deteriorated, and she died eleven days after the operation. No autopsy was performed.


Fig. 1		 Fig. 1 Technetium-99m-methylene diphosphonate bone scan showing intensely increased activity in the T12 vertebra. There is also increased activity around the left ankle and around both knee joints.

For larger view, click on image

Fig. 2-A
Fig. 2-B		 Figs. 2-A and 2-B Sagittal magnetic resonance images of the thoracolumbar spine, acquired with use of a 0.5-T superconducting magnet. On the T2-weighted spin-echo image (Fig. 2-A), an area of high signal intensity is observed in the posterior part of the body of the twelfth thoracic vertebra. On the nonenhanced T1-weighted spin-echo image (Fig. 2-B), the same area has low signal intensity. After intravenous administration of a gadolinium chelate, a slight enhancement was seen (not shown). This area represents the fatty marrow being replaced by necrosis. In the remainder of the twelfth thoracic vertebra, the signal intensity is rather low, which is consistent with edema; the increased water content is better appreciated on the T1-weighted image than it is on the T2-weighted image.

For larger view, click on image

Fig. 3		 Fig. 3 Photomicrograph of a section of bone marrow from the twelfth thoracic vertebra, showing areas of nonvital ghost adipocytes, consistent with intraosseous fat necrosis (hematoxylin and eosin, ×350).

For larger view, click on image

Discussion

Disseminated fat necrosis is a well-known complication of acute, chronic, and traumatic pancreatitis as well as pancreatic cancer. It often is associated with osteolytic lesions in the metaphysis or diaphysis of long bones as well as in the calcaneus and talus. The clinical presentation of disseminated fat necrosis in patients with pancreatic disease is often in the form of panniculitis, polyarthritis, and bone lesions. Intraosseous fat necrosis in patients with pancreatic disease may or may not be painful and may present as a pathologic fracture. The pathogenesis of disseminated fat necrosis has been debated and is poorly understood; it may be more complex than a simple cause-and-effect relationship between circulating pancreatic enzymes and fat tissue. Pancreatic lipase has been implicated, with the pancreatic phospholipase A initiating the process and the resident adipocyte lipases taking an active part, stimulated by the increased norepinephrine and low insulin levels that are usually associated with pancreatitis. High levels of alpha1-antitrypsin have been found in the serum of patients with disseminated fat necrosis, and a defect in that protein, or another as yet unidentified protease or lipolytic inhibitor, could help to explain the uninhibited fat necrosis.

Back pain is often associated with both chronic and acute pancreatitis, typically in conjunction with abdominal pain. The pain may radiate to the middle part of the back or to the scapula, and it may be relieved by leaning forward or sitting upright. Visceral disease, including pancreatitis, accounts for about 2% of all cases of low-back pain.

The history of our patient suggests a spinal etiology of the low-back pain. The tumor had grown into the celiac plexus and therefore may have contributed to low-back pain. Idiopathic vertebral necrosis without vertebral body collapse also may be associated with back pain. One can only speculate, therefore, about the origin of low-back pain; in the case of our patient, however, the pain was attributed to necrosis of the vertebral body. One would expect the rate of progression of the osteonecrosis to be related to the progression of the pancreatic disease, but reliable markers to monitor the progression of osteonecrosis do not exist. Our patient had back pain when she was admitted for pancreatitis for the second time in three months. The biopsy that was performed on both occasions, and after magnetic resonance imaging had been carried out, excluded conditions such as vertebral osteomyelitis, spinal tuberculosis, metastatic tumor, and multiple myeloma of the spine.

The osteolytic complications of pancreatic disease should be kept in mind as a possible cause of protracted and atypical low-back pain in patients with pancreatitis, and clinicians should have a low threshold for acquiring a magnetic resonance imaging scan. We believe that it is important for the general orthopaedic surgeon as well as for the spinal surgeon to be aware of these complications and their management because orthopaedic surgeons are often consulted regarding osteolytic lesions, irrespective of etiology.

Reference

1. Sigmundsson FG, Andersen PB, Schroeder HD, Thomsen K. Vertebral osteonecrosis associated with pancreatitis in a woman with pancreas divisum. A case report. J Bone Joint Surg Am. 2004;86:2504-8.