Normal Spinal Column and Flatback Syndrome
In the frontal plane (looking at the individual straight on), the spine should be straight. In the sagittal plane (looking at the patient from the lateral or side view), the spine has a series of curves. In the neck (cervical spine) and the lower back (lumbar spine) are inward curves or sway known as lordosis. In the thoracic spine, there is an outward curve or kyphosis. For the individual to have an economical stance and gait (i.e. not requiring excessive energy), the curves in the sagittal plane must be well-balanced. The gravity line should fall through the head and cervical spine and behind the sacrum and the center of the hips (Figure 1). In this way, the individual has to invest minimum energy to stand upright and walk.
When these curves fail to be balanced, such as may occur with excessive kyphosis in the thoracic spine or loss of normal lordosis in the lumbar spine, the patient may experience symptoms. The latter condition, a loss of lumbar lordosis or actual kyphosis in the lumbar spine that produces symptoms is termed flatback syndrome.
Symptoms of Flatback Syndrome
The main symptoms are difficulty standing upright with low back and often thigh and groin pain. The patient's symptoms typically will worsen as the day progresses with a sense of fatigue and increasing difficulty in the ability to achieve erect posture. Patients flex or bend their hips and knees to allow them to obtain an upright position. This is often exhausting as the day progresses. Some patients also have symptoms of sciatica and spinal stenosis with leg pain and weakness exacerbated by walking. Some individuals will have neck and upper back pain as they strain to align themselves. These symptoms often become disabling, requiring narcotic medications, and limiting the individual's ability to perform routine daily activities.
Causes of Flatback Syndrome
Flatback syndrome was initially described in a series of patients who had been treated with Harrington spinal instrumentation. This was the earliest type of spinal implant to correct scoliosis. This type of 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 did very well for years or even decades. Their spine could compensate for the "flattening" of lordosis with normal discs below the fusion. Eventually, as the discs below the fusion wore out (degenerated), the individual lost the ability to stand upright and developed pain.
Other causes of flatback syndrome include the entities listed below:
Degenerative Disc Disease: The normal aging process results in wear and tear or degeneration of the intervertebral discs, the shock absorbers of the spine. In the lumbar spine, these discs contribute to normal lordosis. As the discs degenerate, the spine stiffens and lordosis lessens. The patient has progressive difficulty in achieving upright posture.
Vertebral Compression Fractures: A collapse of a single or multiple vertebra, the building blocks of the spine, often due to osteoporosis, may result in loss of lordosis and flatback.
Ankylosing Spondylitis: A chronic inflammatory arthritic disease involving the spine causing stiffness and loss of lordosis.
Post-Laminectomy Syndrome: In some patients, following laminectomy to decompress the spinal nerves, loss of lordosis and instability may occur.
Diagnosis of Flatback Syndrome
The diagnosis is made first by the history. Patients have the typical presentation of difficulty standing upright associated with back pain. They may have a history of prior surgery or a disease process predisposing them to the syndrome as described above.
Next, full-length standing x-rays of the spine are obtained. The lateral view is particularly helpful (Figure 2). With the patient standing and the knees straight, the posture is found to be stooped forward. This is depicted by the gravity line (plumb line) falling in front of the sacrum. Finally, MRI, CT scan, and sometimes a myelogram are utilized to provide information about the integrity and health of the discs and the vertebrae and the patency of the spinal canal (i.e. whether or not compression of the spinal nerves exists).
Standing long lateral x-ray in a 55 year old woman who underwent prior
Harrington rod instrumentation for idiopathic scoliosis 20 years earlier.
Note the loss of normal lordosis or sway in the lower spine and the patient's stooped-forward posture.
Non-Operative Treatment of Flatback Syndrome
Patients may initially be treated with physical therapy and non-steroidal anti-inflammatory medication. A conditioning and endurance exercise program may provide symptomatic relief; however, if the structural problem is significant enough, non-operative management is destined to fail.