The term “hunchback” describes excessive forward rounding of the upper back, which medical professionals refer to as hyperkyphosis. The thoracic spine naturally has a gentle outward curve, but when this curve exceeds 50 degrees, it is classified as abnormal. Its origin varies widely, falling into categories that are either genetic and developmental or acquired later in life.
Hereditary and Developmental Forms of Kyphosis
Certain forms of hyperkyphosis are structural, involving a fixed abnormality in the vertebral bodies linked to genetics or embryonic development. One recognized type is Scheuermann’s disease, or juvenile kyphosis, which manifests during adolescent growth spurts. This condition has a strong hereditary component, often suspected to be autosomal dominant.
Scheuermann’s disease structurally alters the vertebrae, causing the front of the bone to grow slower than the back. This results in a distinct wedge shape instead of the normal rectangular block. For a diagnosis, at least three adjacent vertebrae must show this wedging of five degrees or more, creating a fixed, rigid curvature that cannot be corrected by simply standing straight. The prevalence of this condition is estimated to be between 1% and 8% of the adolescent population.
Another structural type is congenital kyphosis, which is present at birth due to errors that occur during the first six to eight weeks of fetal development. This developmental error results in a malformation of the vertebral column, either through a failure of the vertebrae to fully form (Type I) or a failure of the vertebral segments to separate (Type II). While not always strictly inherited, a genetic component is sometimes suggested, and the resulting deformity is fixed and often progresses as the child grows. Kyphosis can also appear as a feature of broader genetic disorders, such as Marfan syndrome or Ehlers-Danlos syndrome, where defects in connective tissue lead to spinal instability and curvature.
Acquired Causes of Excessive Spinal Curvature
Many cases of hyperkyphosis are acquired later in life, unrelated to inherited or congenital defects. The most common form is postural kyphosis, which is a non-structural and flexible curvature often seen in adolescents and young adults. This type is attributed to muscle imbalances and prolonged poor habits, such as slouching, which stretch the ligaments and weaken the muscles supporting the spine. Since the curvature is not fixed by bony changes, the spine will typically straighten when the individual consciously corrects their posture or lies down.
In older adults, degenerative conditions are the primary acquired cause, leading to what is sometimes called senile kyphosis. Osteoporosis, a condition causing weakened bones, is a common contributor because it can lead to vertebral compression fractures. These fractures cause the front of the vertebral body to collapse into a wedge shape, which forces the spine to curve forward.
Additionally, the natural aging process causes intervertebral discs to flatten and shrink, which further destabilizes the spinal column and contributes to an increased forward curvature. Kyphosis can also be acquired through external factors like trauma and infection. A severe spinal injury, such as from a car accident, can lead to post-traumatic kyphosis if the vertebral bodies are fractured or destabilized. Infections like spinal tuberculosis, historically known as Pott’s disease, can destroy the bone tissue of the vertebrae, causing them to collapse and result in a sharp, angular spinal deformity.
The Diagnostic Process for Determining the Cause
Determining the cause of hyperkyphosis is necessary because the underlying origin dictates the management plan. The diagnostic process begins with a physical examination, where the medical professional assesses the flexibility of the spinal curve. If the curvature corrects itself when the patient lies flat or attempts to stand tall, the diagnosis points toward flexible postural kyphosis. Conversely, a curve that remains rigid and fixed suggests a structural issue, such as Scheuermann’s disease or a congenital defect.
Imaging techniques are essential for confirming the diagnosis and identifying the specific structural changes. A standing lateral X-ray is the standard tool used to measure the spinal curve angle, known as the Cobb angle, with a measurement exceeding 50 degrees confirming hyperkyphosis. X-rays are also used to look for characteristic signs like vertebral wedging in Scheuermann’s disease or compression fractures associated with osteoporosis.
A detailed patient history provides the initial distinction between developmental and acquired causes. Information regarding the age of onset, family history of spinal conditions, and any history of trauma or underlying systemic disease is collected. In complex cases, or when nerve involvement or infection is suspected, a Computed Tomography (CT) scan or Magnetic Resonance Imaging (MRI) may be used to provide detailed images of the bone structure, spinal cord, and soft tissues.