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Figurę 9-3. A, Thoracolumbar scoliosis. B, Spondylolisthesis (arrow indicates step-off). (B, From Rothman RH, Simeone FA. The Spine, 3rd ed. Philadelphia, WB Saunders, 1992, p 925.)

or subcutaneous tissue of the lumbar region that may indicate underlying spinał abnormalities. A lumbar lipoma> an abnormal hair patclt, or a port winę stain may be associated with spina bifida or even myelomeningo-cele. Large tan patches known as cafe au lait spots and nodular skin swellings may indicate ncurofibromatosis, a condition that may causc secondary deformity of the spine.

Step-Off Deformity. Severe degrees of spondylolisthesis may produce a visible step-off deformity of the lumbar spine. Normally, the tips of the lumbar spinous processes should protrude posteriorly about the same amount, pro-ducing a smooth hollow in the lumbar spine. When spondylolysis occurs, the spinous process and associated posterior elements of the involvcd vertebra are dctached from the rest of the vertebra. In this setting, the body of the involved vertebra and the rest of the spine above it may slide forward, producing a spondylolisthesis. Spondylolisthesis is most likely to occur between L5 and

SI. When the amount of spondylolisthesis is severe, an abrupt displacement or step-off is visible (see Fig. 9-3B). Less severe step-offs may only be palpable.

Lateral Aspect

Vievving the patient from the lateral aspect allows the examiner to judge the sagittal alignment of the spine. The lumbar spine is normally lordotic, that is, concavc postc-riorly. A normal lumbar lordosis should exactly comple-ment the thoracic kyphosis and cervical lordosis, so that the base of the occiput rests directly above the sacrum (Fig. 9-4A).

The normal lumbar lordosis, which averages about 60\ is important in order to maintain hcalthy Iow back biomechanics. Several possible departures from normal lordosis may be seen, including hyperlordosis, decreased lordosis, lumbar flatback deformity, and gibbus deformity. Hyperlordosis. Hyperlordosis is usually a flexible pos-tural deformity (see Fig. 9-4B). This deformity, also