Scoliosis Research Society (SRS)
Scoliosis Research Society (SRS)
An International Organization Dedicated to the Education, Research and Treatment of Spinal Deformity
Our Mission is to Foster Optimal Care for All Patients with Spinal Deformities


Fixed Sagittal Imbalance

Types of Sagittal Imbalance

Sagittal imbalance is either fixed or flexible. “Flexible” means the patient can stand up straight if they work at it (with their hips and knees straight), while “fixed” suggests they cannot. Similarly, the imbalance can be either compensated or decompensated. “Compensated” means the body can adapt (usually by flexing the knees and hips), while “decompensated” implies they cannot (see below). The problem leading to the imbalance is either local (a few vertebra causing significant tilt), regional (many vertebra causing a slow forward bend), or a mix of the two (see below).
Compensated vs. Decompensated Imbalance   Types of Fixed Sagittal Imbalance (FSI):
Compensated vs. Decompensated Imbalance
A) Compensated imbalance - A woman with traumatic lumbar kyphosis that compensates by extending her thoracic spine. Her weight-bearing (C7 plumb) line passes through S1.
B) Decompensated fixed sagittal imbalance – the C7 plumb line is well anterior to S1.
  Types of Fixed Sagittal Imbalance (FSI):
FSI can be caused by a local problem involving a few vertebra, a global problem involving many vertebra, or a mix of the two.


Congenital Scoliosis
Early Onset Scoliosis
About Early Onset Scoliosis
Infantile Idiopathic Scoliosis
Thoracic Insufficiency Syndrome
Juvenile Idiopathic Scoliosis
Idiopathic Scoliosis