Flat Back Syndrome (FBS) is a spinal condition defined by the reduction or complete loss of the natural inward curve (lordosis) in the lower back. This loss creates a state of sagittal imbalance, misaligning the spine along the front-to-back plane. The body’s center of gravity shifts too far forward over the hips, forcing the person to compensate by using their hip and leg muscles excessively to maintain an upright stance.
The Role of Spinal Curvature
A healthy human spine features a gentle, S-shaped curve when viewed from the side. This structure includes three distinct curves that provide balance and flexibility: lordosis (inward curve) in the neck and lower back, and kyphosis (outward curve) in the middle and upper back. This natural, alternating curvature acts as a shock absorber, distributing mechanical forces evenly during movement. An appropriate curve keeps the head, torso, and pelvis stacked in alignment, centering the body’s weight efficiently over the hips. Loss of any curve disrupts this harmony, leading to a front-to-back imbalance that affects the entire posture.
Common Reasons for Developing Flat Back
The most frequent cause of Flat Back Syndrome is a previous spinal fusion surgery, especially procedures performed decades ago for conditions like scoliosis. Older surgical techniques, such as the use of Harrington rods, often involved straightening the spine without adequately restoring the necessary lumbar lordosis. This misalignment, known as iatrogenic flat back, often led to symptoms years later as discs below the fused segment began to degenerate.
Degenerative conditions are another common cause, contributing to a gradual loss of the natural lumbar curve over time. Degenerative disc disease causes intervertebral discs to lose height, reducing lordosis and shifting the spine forward. Vertebral compression fractures, often linked to osteoporosis, can also flatten the curve by causing the front of a vertebral body to lose height. Inflammatory diseases like ankylosing spondylitis can cause vertebrae to fuse, resulting in a rigid, straight, or forward-bent spine.
Symptoms and Daily Life Impact
The loss of lumbar lordosis forces the body to constantly fight gravity. Individuals with FBS often experience chronic lower back pain resulting from the muscle strain required to maintain an upright position. This muscular effort causes fatigue, which tends to worsen progressively throughout the day.
A hallmark of the condition is the inability to stand fully upright, leading to a noticeable stooped or forward-leaning posture. To prevent falling forward, a person must often tilt their pelvis backward and flex their hips and knees. This compensatory posture places abnormal stress on the hips and thighs, sometimes leading to pain in those areas. The sensation of falling forward and the pain make simple daily activities, such as standing or walking for long periods, increasingly difficult.
Managing and Correcting the Condition
The initial approach to managing Flat Back Syndrome involves non-surgical treatments aimed at pain relief and improving function. Physical therapy is a cornerstone of conservative care, focusing on strengthening the core muscles to support the misaligned spine and improve posture. Pain management may include anti-inflammatory medications, muscle relaxants, or targeted procedures like epidural steroid injections.
For temporary relief, some patients use a lumbar corset or bracing, though long-term reliance can weaken supportive muscles. If the deformity is severe or conservative measures fail, surgical correction may be necessary to restore lumbar lordosis and re-establish sagittal balance.
Surgical Correction
Surgical procedures often involve complex osteotomies—controlled cuts and realignments of the spinal bones to restore the natural curve. Techniques like the Pedicle Subtraction Osteotomy (PSO) involve removing a wedge of bone from a vertebra to create the necessary backward bend. Following the osteotomy, a spinal fusion is performed using screws, rods, and bone grafts to stabilize the corrected alignment. A thorough diagnostic workup, typically involving full-length standing X-rays, is performed beforehand to measure the degree of sagittal imbalance and determine the patient’s specific needs.