What is characterized by a posterior curvature of the thoracic spine, often resulting in a hunchback?

Kyphosis is characterized by an excessive posterior curvature of the thoracic spine, which can lead to the appearance of a hunchback or rounded shoulders. This condition can result from various factors, including poor posture, osteoarthritis, or degenerative disc disease. In a healthy spine, the thoracic curvature is present, but in kyphosis, this curve is exaggerated, leading to a noticeable deformity.

Understanding the specific conditions of the other options can clarify why kyphosis is the focus here. Lumbar lordosis refers to an excessive inward curvature of the lumbar spine, which is the opposite of what occurs in kyphosis. Flat back posture presents a diminished lumbar curve and tends to flatten both thoracic and lumbar segments, rather than causing a pronounced curvature. Swayback posture involves a displacement of the pelvis that affects lumbar curvature but does not directly cause the thoracic deformity seen in kyphosis. Thus, the defining feature of a posterior thoracic spinal curvature is what distinctly aligns with kyphosis.