The spine’s natural and healthy curvatures make it stronger, more flexible, and better able to absorb/distribute mechanical stress. For the spine to function optimally, it has to maintain its natural curves, so when there is a sagittal imbalance, effective treatment has to address its underlying cause.
The term sagittal imbalance means a front-to-back imbalance in the spine, which disrupts the spine’s natural and healthy curvatures. Measurements taken during X-ray determine the degree of sagittal imbalance, and effective treatment is guided by causation.
Before getting to the specifics of sagittal imbalance, let’s explore the concept of anatomical planes so we can fully break down the term.
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Medical professionals commonly use anatomical planes in reference to sections/parts of the body; think of the planes as imaginary vertical or horizontal lines drawn through an upright body.
The planes are used to specify sections of the body, and specific anatomical terms are used to further specify location and body parts within those sections.
The general anatomical planes include the coronal (frontal) plane, the sagittal (lateral) plane, and the axial (transverse) plane.
The coronal plane divides the front and back half of the body, so imagine a vertical line drawn down the middle of the body. The sagittal plane would also be shown by a vertical line drawn down the middle of the body but would separate the left and right halves of the body. The axial plane is shown by a horizontal line that separates the top and bottom halves of the body.
In addition to the anatomical planes, there are anatomical terms such as anterior, posterior, medial, lateral, inferior, superior etc., that specify locations within the body.
To break down the term, we know that sagittal refers to the lateral plane of the body, meaning the left and right halves of the body, and imbalance means unequal or out of harmony.
Now that we’ve explored the anatomical planes and broken down the term sagittal imbalance as a front-to-back imbalance in the spine, let's touch on how sagittal imbalance is measured.
In a healthy spine, there are two soft front-to-back curves. The lumbar spine (lower back) has an inward curve known as lordosis, as does the cervical spine (neck); the thoracic spine (middle back) has an outward curve known as kyphosis.
When these curves are within a healthy range, they work together to maintain the body’s alignment and center of gravity over the hips and pelvis, but if one of those curves becomes over-or under-pronounced, the spine will develop a front-to-back imbalance.
While there is a natural and healthy curvature-degree range when a curvature falls beyond that normal range, that is when problems occur involving the imbalance related to uneven forces.
In addition, there are different types of sagittal imbalance:
In flatback syndrome, the lumbar spine has lost its normal lordosis, meaning the lower back has lost its inward curve, pushing the body’s center of gravity excessively forward.
Kyphosis refers to the natural outward spinal curvature and is used interchangeably with the term hyperkyphosis in reference to conditions where there is an over-exaggerated kyphotic curve.
When the thoracic spine’s kyphosis becomes over-pronounced, the back can develop a pitched-forward or hunched appearance.
Chin-on-chest syndrome is a type of severe kyphosis.
So now that we have explored the different types of sagittal imbalance the spine can develop, let’s talk about how to measure sagittal imbalance.
How to Measure Sagittal Imbalance
Just as there are different natural curvature-degree ranges, there are different ranges of unnatural curvatures, which is why measuring sagittal imbalance is important for determining condition severity and guiding the design of effective treatment plans moving forward.
X-ray imaging shows what is happening in the spine and how far out of alignment it is to determine the degree of sagittal imbalance.
Often, it’s an upright scan that I use, as this shows the entire length of the spine in a single image.
I can also recommend additional diagnostic procedures for more-detailed images of the spine, if needed, such as magnetic resonance imaging scans (MRI) and/or computed tomography scans (CT).
While there are different techniques for assessing the degree of sagittal imbalance, the most common and widely-used method is the C7 plumb line and sagittal vertical axis (SVA).
This measurement is performed by drawing a vertical line from the center of the C7 vertebral body (seventh cervical vertebra in the neck) and should pass through the superior endplate of S1 (first fused vertebra of the sacrum); the sacrum is the triangular-shaped bone that sits between the hip bones of the pelvis.
The line should pass through the S1, or be within 5 mm. This is considered a normal range for sagittal balance, but as patients age, or when other spinal conditions come into play, their posture can shift forward to facilitate more positive sagittal alignment.
If the line does not pass through the S1 vertebra, and/or is not within that normal range, there is a sagittal imbalance, and how far it is from that ideal range is measured in degrees.
In addition, the position of the C7 plumb line can be classified as positive, neutral, or negative.
What is Negative Sagittal Imbalance?
The position of the plumb line and its location in relation to the S1 vertebral body further specifies the level/degree of sagittal imbalance and helps to classify the condition.
The term negative balance refers to when the plumb line passes more than 2cm behind a portion of the S1 vertebra. While positive balance involves the plumb line passing more than 2cm in front of a portion of the S1 vertebra, neutral balance means the plumb line passes within 2 cm of a portion of the S1 vertebra.
So now that we know how sagittal imbalance is measured and what constitutes a normal vs. abnormal range let’s discuss how to treat it.
When it comes to treatment options for correcting a sagittal imbalance, while no treatment results can be guaranteed, the first step is determining the underlying cause of the imbalance.
Treatment plans must be customized to address important patient and condition characteristics such as age and overall health, etiology, location, and condition severity.
Reestablishing spinopelvic alignment is key to reducing the uneven forces introduced to the spine and body.
If the underlying cause of the misalignment is the presence of a spinal condition like scoliosis, for example, scoliosis has to be proactively treated to reestablish spinopelvic alignment.
Through a combination of physical therapy, corrective bracing, and condition-specific chiropractic care, here at the Scoliosis Reduction Center, I can help my scoliosis patients work towards a reduction of the unhealthy spinal curvature in an effort to restore the spine’s alignment.
As the condition is impacted on a structural level, adjusting the tilted vertebrae back into alignment with the rest of the spine means the uneven forces exposed to the spine and body are being reduced alongside the unnatural spinal curve.
When hyperkyphosis is the source of the sagittal imbalance, the type of kyphosis will guide treatment; Scheuermann’s, congenital, and postural are the most common forms.
Scheuermann’s is the most complex to treat because it’s a structural condition, meaning there is a structural abnormality within the spine itself, so I would use a combination of chiropractic care to adjust the vertebrae on a structural level and realign the spine and physical therapy to strengthen the abdominal and back muscles, so the spine is better supported and stabilized.
For cases of congenital kyphosis, patients are born with the condition due to an issue with how the spine formed and developed in-utero, and it tends to progress with age.
As congenital kyphosis is also a structural condition, treatment has to involve impacting it on a structural level. While there are unique challenges associated with treating this age group, I can modify treatment to address these challenges, and when necessary, bracing can help support, stabilize, and work towards corrective results when possible.
In cases of postural kyphosis, the imbalance is not structural in nature, meaning it’s not permanent and can be reduced with changes of position, proper posture, lifestyle guidance, and therapeutic exercises that improve body posture and positioning; this form is the simplest to treat.
The body’s center of gravity is defined as the balance point in the body: where the body’s upper and lower body weight is balanced.
When there is a sagittal imbalance, there is a front-to-back imbalance in the spine, which disrupts the body’s center of gravity and overall symmetry.
When the spine is exposed to uneven forces, such as those that are introduced when there is the loss of a natural spinal curve, the body’s center of gravity shifts to compensate, which can cause a number of problems.
There are different causes associated with sagittal imbalance. When the cause is the presence of another spinal condition, such as scoliosis or hyperkyphosis, it’s the condition that needs to be proactively addressed as the imbalance’s underlying cause.
While surgical treatment can be recommended for some severe forms of sagittal imbalance, here at the Scoliosis Reduction Center, many cases of sagittal imbalance can be treated nonsurgically through a conservative chiropractic-centered approach that combines corrective bracing, custom-prescribed home exercises, physical therapy, and chiropractic care.