The human spine has natural curves when viewed from the side, but it should appear straight from the back. Scoliosis is a three-dimensional deformity defined by an abnormal lateral curvature of the spine that also includes a rotational component. This sideways bending can cause the spine to resemble a “C” or an “S” shape. Affecting an estimated two to three percent of the U.S. population, the severity of this spinal deviation can progress, especially during periods of rapid growth.
Understanding Double Curve Scoliosis
Double curve scoliosis, also known as double major scoliosis or an S-curve, is a specific pattern where the spine develops two distinct, opposing curves. This configuration differs from the more common single C-shaped curve, which involves only one major deviation. In the double curve pattern, the spine bends in one direction and then reverses in a different region, forming the characteristic “S” shape.
For a curve pattern to be classified as true double major scoliosis, both curves must be structural, meaning they are fixed and inflexible. Typically, one curve is located in the upper or middle back (thoracic spine), and the second curve is in the lower back (lumbar spine). The thoracic curve often bends right while the lumbar curve bends left, or vice versa, creating a complex spinal alignment challenge. This dual-curve pattern complicates treatment because intervention must address both curves to maintain central balance. The double major pattern is less common than the single curve, accounting for approximately 13 percent of diagnosed scoliosis cases.
Recognizing the Physical Indicators
The presence of double curve scoliosis often leads to several observable physical asymmetries. One common indicator is uneven shoulder height, where one shoulder appears noticeably higher than the other. This imbalance is often accompanied by the prominence of one shoulder blade, which may stick out due to the rotational twist in the rib cage.
The asymmetry extends down the torso, frequently causing unevenness in the waistline or hips. A person might appear to lean slightly to one side, or one hip may look higher or more prominent when standing. A significant physical cue is the presence of a “rib hump,” which becomes evident during Adam’s Forward Bend Test. When the patient bends forward, the rotation of the vertebrae causes the ribs on one side to push out, creating a noticeable hump. These signs prompt a medical evaluation but do not constitute a formal diagnosis.
Confirming the Diagnosis
The confirmation and precise characterization of double curve scoliosis require a thorough diagnostic workup, beginning with a full-spine standing X-ray. This imaging provides a complete view of the spine and allows specialists to accurately measure the degree of curvature using the Cobb angle.
For a double curve pattern, two separate Cobb angles must be measured: one for the thoracic curve and one for the lumbar curve. This dual measurement is essential to classify the curve as double major and determine the severity of each component. The diagnostic process also includes identifying the curve type, such as adolescent idiopathic scoliosis, or less frequent types like congenital or neuromuscular scoliosis. To differentiate between a fixed structural curve and a flexible, non-structural compensatory curve, a flexibility assessment using bending films is often performed. These side-bending X-rays help determine if the curves partially correct themselves when the patient bends, which is a key factor in planning treatment.
Treatment Pathways
The management of double curve scoliosis is tailored to the patient’s age, skeletal maturity, and the magnitude of the Cobb angles. For mild curves, defined as those less than 25 degrees, the standard approach is observation and regular monitoring. Patients are seen periodically for physical exams and X-rays to ensure the curve is not progressing, especially during growth spurts.
When the curve progresses to a moderate range (25 to 45 degrees in a growing adolescent), bracing is often recommended to prevent further progression. A custom-fitted brace applies corrective pressure to both the thoracic and lumbar apices of the S-curve. The goal of bracing is to hold the curvature steady until the patient reaches skeletal maturity, not to correct the existing curve.
Surgical intervention is reserved for severe curves, usually those exceeding 45 or 50 degrees, or for curves that continue to progress despite bracing. The procedure involves instrumentation and fusion, using metal rods, screws, and hooks to straighten the spine and permanently fuse the vertebrae. The complexity of a double major curve requires balancing both the upper and lower curves to ensure the head and torso are properly centered over the pelvis after fusion.