Global Sagittal Balance
Some patients need fusions.
If you need a fusion, even a small one, it is important to consider how the fused segment will affect the balance of the spine. Once the spine is fused, it is relatively permanent. Therefore, if your spine is fused out of balance, you may more or less be out of balance forever.
Global sagittal balance is an important concept in spine surgery and can profoundly affect surgical outcomes, especially in spinal fusion procedures. Global sagittal balance refers to the alignment of the spine and pelvis in the sagittal plane, which is the plane that divides the body into left and right halves. In a healthy individual, the spine and pelvis are aligned to maintain a stable and efficient posture where the head is essentially centered over the hips and pelvis. However, when this alignment is disrupted, it can lead to various spinal disorders, including chronic pain and disability.
One important concept in global sagittal balance is the cone of economy. The cone of economy is a theoretical concept that describes the ideal zone of balance for the human body. It is represented by a cone-shaped area that begins at the base of the pelvis and extends upward through the spine. The cone of economy represents the most energy-efficient position for the body, where the least amount of muscular effort is required to maintain balance.
The cone of economy is determined by several factors, including the location of the body’s center of gravity, the alignment of the spine and pelvis, and the distribution of body mass. When the body is aligned within the cone of economy most of your weight is transmitted through the bones and joints. Muscles are in their optimal position only needed for adjustments and to provide support, and the spinal curves are balanced to minimize stress on the spine.
However, when the body’s alignment falls outside the cone of economy, the muscles must work harder and harder to maintain balance, which can lead to muscle fatigue and pain. For example, if the pelvis is tilted too far forward, the body’s weight shifts forward, and the muscles in the lower back must work harder to maintain balance. This can lead to chronic lower back pain.
A simple example of what it is like to have a spine out of balance is trying to hold your arm out so it is pointing straight forward without any support. Initially it’s not too bad. Your shoulder feels fine. But if you try to hold it there for a minute, or for five minutes – by the time you’re done the shoulder muscles are screaming. That’s because the shoulder muscles are not designed to statically hold the arm up like that. Yet this is what you are asking your back muscles to do when you are trying to stand if your spine is out of balance. First the muscles fatigue and then they start to hurt until you have a severe back ache.
In conclusion, global sagittal balance and the cone of economy are important concepts in the understanding and treatment of spinal conditions. The cone of economy represents the most energy-efficient position for the body, where the least amount of muscular effort is required to maintain balance making it easier to stand, walk, and perform normal daily activities. If you feel like your spine is out of balance, talk to your doctor. We can use these concepts to design treatment plans that aim to restore the body’s alignment to within the cone of economy, reducing the risk of persistent or recurrent back pain and improving patient outcomes.