Flat back syndrome overview


In flat back syndrome, also called fixed sagittal imbalance, the normal curvature of the lumbar spine decreases or disappears. The main symptom is difficulty standing for a long time.

Flat back syndrome can be congenital, due to degeneration or injury, or as a result of spinal surgery. Treatment often includes physical therapy, fixation, or surgery.

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The spine usually has two curves that maintain balance and the center of gravity, which provides better biomechanics of movement.

The lumbar spine curves inward at its intersection with the pelvis, as does the cervical neck . These are lordotic curves. The thoracic spine bends outward, which is a kyphotic curvature.

The lordotic and kyphotic curves are part of the natural alignment of your spine. When these curves taper, it can be difficult for you to stand up straight and lean forward, especially towards the end of the day. It may appear that you are falling forward. You may also need to bend your hips and knees and adjust your pelvis to stand straight .

Generally, when looking at the body from the side, the sagittal axis (front to back) should be no more than 5 millimeters (mm) from vertical. In flat back syndrome, the center of mass shifts forward and the axis deviates from vertical by more than 5 mm.

When you are out of the center, you will find it difficult to walk and do other daily activities, and you may feel tired from the strain of trying to keep your balance.

The body compensates for flat back syndrome by pushing the head and neck forward, which can cause tension and chronic pain in the neck, upper back, and shoulders.


Flat back syndrome can be caused by a variety of problems.

Some reasons include :

Flat back syndrome can occur after spinal surgery such as a laminectomy. In the past, surgically implanted devices used to correct scoliosis tended to flatten the lumbar spine and lead to flat back syndrome, especially with age. Updated surgical techniques have reduced this complication.


The diagnosis of flat back syndrome begins with a medical history that includes your spinal deformities or back surgery.

Your healthcare provider will also perform a physical exam, which includes a musculoskeletal exam and a neurological exam . A gait test is an assessment of your gait that may have changed to compensate for the loss of spinal curvature.

An X-ray of the spine can visualize its sagittal alignment. Your doctor will consider other possible sources of symptoms before confirming the diagnosis.

Watch out

Conservative treatment for flat back syndrome begins with exercise and physical therapy, which includes stretching and strengthening exercises to improve posture.

A common strategy is to use exercises to restructure muscle imbalances so that the lower back remains flat. Hamstring and abdominal stretches are key in this process.

Exercises to strengthen your core, glutes, back, neck, and rear shoulders include .

A gentle, sustained hamstring stretch , held for about 30 seconds at a time, repeated three to five times in a row (once or twice a day) is a good way to restore proper alignment of the lumbar spine.

Your physical therapist can evaluate you and recommend exercise and other forms of treatment. This can include spacers for better support .

In some cases, surgical correction may be necessary to restore alignment.

Operations that can be considered include:

  • Polysegmental wedge osteotomy
  • Pedical subtraction osteotomy
  • Resection of the back of the spine
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