At what level of the thoracic spine is the apex of thoracic kyphosis typically located?

Apex of Thoracic Kyphosis

The apex of thoracic kyphosis is typically located at the T6-T7 vertebral level in normal asymptomatic individuals. 1

Anatomical Location and Variations

The thoracic spine naturally forms a kyphotic curve (posterior convexity) in the sagittal plane. Based on recent research:

• The apex of thoracic kyphosis is most commonly found at the T6-T7 vertebral level 1
• T7 tends to be horizontally oriented (neutral tilt), regardless of the overall kyphosis angle or patient age 1
• Cumulative kyphosis analysis confirms that the apex is located at the T6-T7 junction 1
• More recent studies have found the apex may be slightly lower, around T8-T9, depending on the individual's spinal morphotype 2

Distribution of Kyphosis

The thoracic kyphosis is not a simple circular arc but has specific distribution characteristics:

• Thoracic kyphosis can be divided into two arches:

  • Upper thoracic kyphosis (UTK)
  • Lower thoracic kyphosis (LTK)

• In asymptomatic adults, these arches are unequal:

  • Upper thoracic kyphosis averages 25.8°
  • Lower thoracic kyphosis averages 19.8° 2

• The distribution pattern varies with the magnitude of kyphosis:

  • In individuals with low thoracic kyphosis, approximately 2/3 of the kyphosis is located in the upper part
  • As thoracic kyphosis increases, the distribution becomes more symmetric around T7 1

Clinical Significance

Understanding the normal location of the thoracic kyphotic apex is important for:

1. Evaluating pathological conditions such as Scheuermann's kyphosis, where increased posterior rounding of the thoracic spine occurs with structural deformity of vertebral elements 3

2. Surgical planning for corrective procedures:

   • Relocation of the apex after corrective surgery affects outcomes in conditions like ankylosing spondylitis 4
   • Patients with a postoperative apex at T8 or above tend to have better sagittal vertical axis correction 4

3. Bracing considerations:

   • For conditions like Scheuermann's kyphosis, understanding the normal apex location helps in designing effective braces 3

Biomechanical Considerations

The location of the thoracic kyphosis apex has biomechanical implications:

• T7 typically serves as a neutral vertebra (horizontal orientation) that divides the upper and lower segments of thoracic kyphosis 1
• Changes in the apex location affect the center of gravity and load distribution through the spine 5
• In pathological kyphosis (>50°), wedge-shaped vertebral bodies at or near the apex increase the flexion-bending moment acting on the spine 5

Understanding the normal apex location at T6-T7 provides a reference point for evaluating both normal variations and pathological conditions affecting thoracic spine alignment.