Back braces are a recognized and effective treatment for adolescent idiopathic scoliosis (AIS), a condition involving a sideways and rotational curve of the spine that appears around puberty. Scientific evidence confirms that bracing is an important intervention that helps manage the curve’s development during the patient’s remaining growth period. The primary goal is not to eliminate the curve but to prevent its progression.
The Primary Goal of Bracing
The established goal of bracing is to prevent the curve from worsening significantly while the patient is still growing. Success is defined as reaching skeletal maturity without the curve progressing to a magnitude requiring surgical intervention, typically a Cobb angle of 50 degrees or greater.
Bracing works to alter the natural history of the condition, which often involves curve progression during rapid growth spurts. The landmark Bracing in Adolescent Idiopathic Scoliosis Trial (BrAIST) provided high-quality evidence supporting this approach. The study found that patients in the bracing group had a significantly higher success rate, with 72% reaching skeletal maturity without the need for surgery, compared to only 48% in the observation group.
This evidence demonstrated a clear “dose-response” relationship, meaning effectiveness is directly related to how many hours the brace is worn each day. Patients who wore their brace for at least 13 hours daily had a notably high success rate in preventing curve progression above the surgical threshold. The brace acts as a mechanical restraint to keep the curve stable until the adolescent reaches full skeletal maturity.
Determining Eligibility for Bracing
The decision to prescribe a brace is based on clinical measurements and the patient’s remaining growth potential. Bracing is typically recommended for moderate spinal curves, defined as a Cobb angle between 25 and 40 degrees. Curves smaller than 25 degrees are monitored, while those over 40 degrees may be considered for surgery, especially if progression is rapid.
The most important factor is skeletal maturity, which indicates how much growth remains and the risk for the curve to worsen. Specialists assess this using indicators like the Risser sign, which evaluates the ossification of the iliac crest on an X-ray. Bracing is most effective for skeletally immature patients, typically those with a Risser sign of 0 to 2, indicating significant expected growth.
For female patients, the timing of menarche is also considered, as curve progression risk decreases substantially about one year after the start of menstruation. By focusing on patients who have moderate curves and are still actively growing, doctors target the population most likely to benefit from the mechanical support of a brace.
How Braces Modify Spinal Progression
The mechanical action of most rigid braces, such as the Boston brace, relies on the three-point pressure system. This system applies pressure at three distinct points to physically push the curved spine into a straighter position. One force is applied directly to the apex of the curve, while two counter-forces are applied above and below the curve on the opposite side of the body.
This continuous force holds the spine in a corrected posture within the brace. For the growing spine, this external loading is thought to influence vertebral growth plates, a concept referred to as the Hueter-Volkmann principle. By unloading the concave side of the curve and loading the convex side, the brace encourages more symmetrical growth of the vertebrae.
More modern brace designs, like the Cheneau-type orthoses, incorporate a three-dimensional approach using expansion chambers and rotational forces to address the twisting component of scoliosis. These braces aim for active correction by moving the spine in the sideways, rotational, and front-to-back planes. Regardless of the specific design, the brace functions as a scaffold that guides the spine’s growth during skeletal development.
Different Bracing Systems and Compliance
Scoliosis braces are broadly categorized into full-time and nighttime systems, with the choice depending on the curve type and severity. Full-time braces, such as the Boston or Cheneau braces, are rigid plastic shells worn for 18 to 23 hours daily. They are recommended for patients with larger or more complex curves, particularly double curves, where constant support is necessary.
Nighttime braces, including the Providence and Charleston bending braces, are worn for a shorter duration, often eight to ten hours, exclusively while the patient is sleeping. These braces are designed to apply a stronger, over-corrective force to the spine, a force that would be difficult to tolerate while standing or moving. Nighttime bracing is often used for single thoracolumbar or lumbar curves that are smaller than 35 degrees, or when compliance with a full-time brace is a major concern.
Compliance, or the consistent number of hours the brace is worn, is the most important factor determining treatment success. Patients who fail to wear the brace for the prescribed hours are significantly more likely to experience curve progression. Once the patient reaches skeletal maturity, typically indicated by a Risser sign of 4 or 5, the brace is gradually discontinued through a structured weaning process. This slow reduction of wear time allows the spine to adjust to the lack of external support while minimizing the risk of the curve worsening after treatment ends.