Sagittal Plane Deformity

The human body functions best when it is aligned or balanced both from the front and side such that the head remains centered over the pelvis in both planes. This alignment allows ambulation and other functions with a minimum of energy expenditure. The coronal plane views the body from the front and the sagittal plane views the body from the side. Of the two, sagittal alignment is more important for proper functioning of the body. Walking in the “bent over” position is not only very tiresome but is also a cause of significant low back pain.

There are many causes of sagittal plane deformity. Probably the most common is that of aging itself. As we age, disc height is lost and back muscles become weak leading to the “stooped” posture often seen in the older person. Another common cause is “lumbar flatback” which may occur following low back surgery. The removal of bone (laminectomy) to decompress the nerves may weaken the spine and allow it to fall forward. Also, fusing the lumbar spine in a flattened position causes a loss of lumbar lordosis which prevents the patient from standing erect thus causing sagittal plane deformity. Other less frequent causes of sagittal plane deformity include fracture, infection or tumor.

Treatment of sagittal plane deformity depends upon the severity of the imbalance. Mild cases may be treated with bracing to help hold the patient erect. More severe cases often require surgery to realign the spine. This usually consists of removing a portion of the spine to “loosen up” the spine followed by the placement of screws and rods to correct the sagittal plane deformity and restore normal lumbar lordosis. After this, the spine is fused in the corrected position to hold it permanently in place. How much bone is removed to loosen up the spine depends upon the severity of the deformity. For moderate deformities a Smith Petersen Osteotomy or SPO will suffice. For more severe deformities a Pedicle Subtraction Osteotomy or PSO is often required.