The typical imaging hallmarks are destruction and subsequent obliteration of the sacroiliac joints, followed by bony bridging of the vertebral bodies to produce the characteristic “bamboo spine.” When this change becomes apparent, the pain usually subsides, but the patient by then has little motion of the back and neck. An unusual additional feature, almost unique to this condition, is an extreme dilatation of the lumbar thecal sac. Ankylosing spondylitis may also be accompanied by the Reiter syndrome, psoriasis, and inflammatory diseases of the intestine (see also Chap. 42). The great risk in this disease is fracture dislocation of the spine from relatively minor trauma, particularly flexion–extension injuries.
Occasionally ankylosing spondylitis is complicated by destructive vertebral lesions. This complication should be suspected whenever the pain returns after a period of quiescence or becomes localized. The cause of these lesions is not known, but they may represent a response to nonunion of fractures, taking the form of an excessive production of fibrous inflammatory tissue. When it is severe, ankylosing spondylitis may involve both hips, greatly accentuating the back deformity and disability.
Rheumatoid arthritis of the spine may be confined to the cervical region and creates risk of fracture–dislocation; it is considered again further on in this chapter.
Neoplastic and Infectious Diseases of the Spine (See Also Chap. 42)
Metastatic carcinoma (breast, bronchus, prostate, thyroid, kidney, stomach, uterus), multiple myeloma, and lymphoma are the common malignant tumors that involve the spine. The primary lesion may be small and asymptomatic, and the first manifestation of the tumor may be pain in the back caused by metastatic deposits. The pain is constant and dull; it is often unrelieved by rest and is generally worse at night, interrupting sleep. Radicular pain may be added if the metastasis extends laterally. A fracture of a vertebral body in an otherwise healthy young or middle-aged person should alert the physician to the possibility of an underlying metastasis. At the time of onset of the back pain, there may be no radiographic changes on plain radiographs; when such changes do appear, they usually take the form of destructive lesions in one or several vertebral bodies with little or no involvement of the disc space, even in the face of a compression fracture. However, the changes are evident on CT and MRI or radioactive isotope scan that detects areas of osteoblastic activity caused by neoplastic or inflammatory disease.
Infection of the vertebral column, osteomyelitis, is usually caused by staphylococci and less often by coliforms and mycobacteria. The patient complains of subacute or chronic pain in the back, which is exacerbated by movement but not materially relieved by rest. Motion becomes limited, and there is percussion-induced tenderness over the spine in the involved segments and pain with jarring of the spine, as occurs when the heels strike the floor. Often these patients are afebrile and do not have a leukocytosis. The erythrocyte sedimentation rate and C-reactive protein are elevated as a rule. CT and MRI characteristically demonstrate involvement of both the vertebral body and the adjacent intervertebral disc, and the finding of a breached disc space with involvement of two adjacent vertebral bodies is one of the features that differentiates infectious from neoplastic diseases of the spine. A paravertebral mass is often found, indicating an abscess, which may, particularly in the case of tuberculosis, drain spontaneously at sites quite remote from the vertebral column. We have also encountered a number of patients with subacute bacterial endocarditis who complained of severe midline thoracic and lumbar back pain but had no evident infection of the spine.
Tuberculous spinal infection and the resultant kyphotic deformity (Pott disease) represent a special condition that is common in developing countries (see Chaps. 31 and 42).