Final answer:
Lordosis is the spinal condition known for an abnormally increased anterior concavity or posterior convexity in the lumbar region, often related to obesity or pregnancy.
Step-by-step explanation:
The spinal condition that involves an abnormally increased anterior concavity, also known as posterior convexity, is lordosis. This condition manifests as an excessive anterior curvature in the lumbar region of the vertebral column. Often associated with obesity or pregnancy, lordosis results from an anterior shift in the body's line of gravity due to accumulated weight in the abdominal region, which leads to an anterior tilt of the pelvis and a pronounced lumbar curve. Unlike lordosis, scoliosis is characterized by an abnormal lateral bending of the spine, and kyphosis is described as excessive posterior curvature of the thoracic region. Spondylolisthesis is a condition where one vertebra slips forward over the one below it and is not primarily characterized by a curvature.