Flatback syndrome was initially described in patients who had been treated with Harrington spinal instrumentation. This was the earliest spinal implant (instrumentation) to correct scoliosis. This instrumentation had a tendency to flatten the normal sway or lordosis in the lumbar spine, particularly when the fusion was taken down into the lower lumbar spine (L4 or L5).
This system was utilized from the 1960s to the 1980s. With modern scoliosis implant systems and techniques, this problem is much less common. Patients treated with Harrington rods often do well for years or even decades. The spine can compensate for the "flattening" of lordosis with normal discs below the fusion. Eventually, as the discs below the fusion wear out (degenerate), the patient loses the ability to stand upright and develops pain.
When viewing the spine from the side (sagittal plane), we find the spine has 2 naturally occurring curves:
Spinal curves are measured in degrees. The normal range for kyphosis is 20-45 degrees; lordosis is 30-65 degrees.
Sagittal Plane Anatomy (showing natural Kyphosis (20-45°) and Lordosis (30-65°)
Flatback syndrome develops from a straightening of the normal lordosis (inward sway) in the lumbar spine; it becomes more kyphotic.
At first, the unfused spinal segments compensate for the straightening effects, but eventually the discs degenerate and wear down. The patient develops back pain, difficulty standing upright, and experiences limitations when walking. Eventually, the problem requires a spinal realignment procedure with an osteotomy such as a pedicle subtraction osteotomy.
Please note the gravity line falls far forward in the flatback patient making it difficult to stand upright.
X-rays Showing Flatback Syndrome
A 61-year-old female 30-years after Harrington rod implantation with flatback. Please note the gravity line arrows before and after surgery. The patient is hunched forward prior to surgery and restored to normal posture after surgery.
Remember, Harrington rods aren't used anymore to address scoliosis. However, if you had a Harrington rod implanted before, you may develop flatback syndrome. Be sure to report any pain, trouble standing upright, difficulty walking, or other symptoms to your doctor. It is possible to surgically correct flatback syndrome.
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