Exploring Spinal Alignment in individuals without back pain
The alignment of the spine as a whole is referred to as the global sagittal balance (GSB). The assessment of regional and global sagittal spinal alignment is crucial in clinical evaluations and surgical procedures to reduce the risk of complications, including adjacent-segment disease, pseudarthrosis, sagittal imbalance, and the progression of deformities.
Having a fundamental knowledge of the global sagittal balance (GSB) is advisable to attain biomechanical stability of the spine. Literature has attempted to incorporate and merge recent measures to define the boundaries between the balanced and unbalanced types.
To evaluate the global sagittal balance (GSB) of the spine in people who have no symptoms and those who do, several measurements are used, including the spino-sacral angle (SSA), which is the angle between the center of the C7 vertebra and the center of the S1 endplate, and the sagittal vertical axis (SVA), which is the horizontal distance between the C7 plumb line and the posterior superior S1 corner.
When the C7 plumb line is in front of the posterosuperior corner of the sacrum, it is known as SVA positive, and when the C7 plumb line is behind the posterosuperior corner of the sacrum, it is called SVA negative. Regarding the SVA measurement, a positive value indicates a kyphotic curve, while a negative value indicates a lordotic curve.
Apart from these metrics, the T1 pelvic angle (TPA, measured in degrees) is also used to determine the angle between the line running from the femoral head to the centroid of T1 and the line running from the femoral head to the middle of the S1 endplate.
- The T1 spinopelvic inclination (T1SPI, measured in degrees) is the angle formed between the vertical plumb line and the line extending from the vertebral body centroid of T1 to the centroid of the bi-coxo-femoral axis.
- The Barrey index, also known as the C7/sacro femoral distance ratio, is calculated by dividing the distance from the midpoint of the C7 vertebra to the posterior superior corner of the sacrum along the plumb line by the sacro-femoral distance.
- The odontoid hip axis (OD-HA, measured in degrees) is determined by calculating the angle between the vertical line and the line that connects the highest point of the odontoid to the midpoint of the bi-coxo-femoral axis.
- The Full Balance Index (FBI) is composed of three distinct parameters, namely the C7-translation angle, the femoral obliqueness angle, and the pelvic compensation angle.
Determining the ideal sagittal shape and establishing optimal parameter values for GBS can be challenging as there is no definitive standard. Having a comprehensive understanding of what constitutes a normal GSB is crucial when evaluating and treating patients with spinal pathologies.
Currently, no systematic reviews have been conducted to evaluate the evidence pertaining to GSB parameters in asymptomatic individuals. On the other hand, there are no universally accepted values in the existing literature for evaluating GSB parameters in this particular population.
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I am Vedant Vaksha, Fellowship trained Spine, Sports and Arthroscopic Surgeon at Complete Orthopedics. I take care of patients with ailments of the neck, back, shoulder, knee, elbow and ankle. I personally approve this content and have written most of it myself.
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