Baastrup Disease/Interspinous Bursitis

Baastrup disease (BD), an uncommon back pain syndrome, is characterized by pathologic approximation of adjacent spinous processes on a sagittal plane image. BD occurs most commonly at the lumbar L4-L5 level and tends to be more common in the elderly. The etiology is not precisely known, but BD may develop secondary to chronic active inflammatory facet arthropathy, leading to interspinous osteophytes and approximation of the adjacent spinous processes. Clinically, BD should be considered in the differential diagnosis of back pain if there is (1) midline back pain reproduced with palpation of the spinous process and exacerbated by extension of the lumbar spine and (2) direct contact of adjacent spinous processes on the lateral view of a plain x-ray image. Magnetic resonance imaging is more sensitive in detecting interspinous inflammation and the formation of bursa and new bone. Major differential diagnoses of BD include proliferative hyperostosis of the lumbar spinous processes, degenerative disease of the spine, sclerotic bone metastases to the spine, and ankylosing spondylosis. BD can be managed initially with nonsteroidal antiinflammatory drugs, a short-term steroid dose pack, and physical therapy. Injection of a local anesthetic to the inflamed spinous process and associated interspinous ligaments may be diagnostic, and injection of a local anesthetic/corticosteroid combination may be therapeutic. Surgery is reserved for patients with refractory BD. Surgical options include interspinous process decompression devices and excision of the affected spinous processes.