Scoliosis is defined by the lateral, or sideways, curvature of the spine, which also involves a rotational twist of the vertebral column. While mild cases typically do not affect health, severe scoliosis, particularly when located in the thoracic (chest) area, can significantly compromise lung function. This spinal deformity physically alters the structure of the chest cavity, directly influencing the mechanics of breathing. Understanding this connection involves examining how the abnormal curvature restricts space, the resulting functional impairment, how severity is measured, and the medical strategies available for management.
How Spinal Curvature Restricts Breathing
The scoliosis deformity disrupts the normal anatomical relationship between the spine, rib cage, and lungs. The condition involves not only the sideways curve but also the rotation of the vertebrae. This rotation pulls the attached ribs, causing a physical distortion of the entire thoracic cage structure.
This distortion reduces the total volume available for the lungs to fully expand during inhalation. The chest wall becomes stiffer, known as decreased chest wall compliance, which physically restricts the movement needed for a deep breath. Breathing becomes a greater physical effort because the respiratory muscles are placed at a mechanical disadvantage by the altered shape of the rib cage. The resulting issue is a physical restriction of the chest wall itself, not a primary disease of the lung tissue.
Types of Respiratory Impairment
The primary functional consequence of the chest wall restriction is restrictive lung disease. This impairment means the lungs are unable to fully inflate, leading to a reduction in total lung capacity and vital capacity. The chest wall’s stiffness and reduced range of motion are the direct causes of this restriction.
This restriction differs from obstructive lung diseases, such as asthma, where airflow is blocked within the airways. In scoliosis-related restriction, the air tubes remain open, but the mechanical “bellows” of the chest cannot move adequately. A secondary complication of this reduced capacity is difficulty in clearing secretions from the lungs, which can increase the risk of recurrent respiratory infections, such as pneumonia. Severe restriction can also lead to chronic respiratory failure.
Measuring Risk and Severity
The risk of lung impairment is strongly correlated with the magnitude of the spinal curve, measured using the Cobb angle on an X-ray. This angle is the primary tool for assessing severity and predicting potential respiratory issues. Lung function decline often becomes detectable once the thoracic curve exceeds 50 to 60 degrees.
Respiratory compromise becomes more pronounced in curves greater than 70 degrees. Severe impairment and a significant risk of respiratory failure are associated with curves over 100 to 110 degrees. However, the risk is complex and also depends on the curve’s location, the number of vertebrae involved, and the age of the patient when the curve developed. Earlier onset scoliosis, particularly before age five, carries a worse respiratory prognosis due to impaired lung development during growth.
Diagnostic tools like Pulmonary Function Tests (PFTs) are used to assess the degree of impairment. These tests measure lung volumes, most importantly the Forced Vital Capacity (FVC), which is the total amount of air a person can forcibly exhale after a maximal inhalation. A significantly reduced FVC is the hallmark of restrictive lung disease and helps physicians track the curve’s impact on breathing capacity over time.
Management of Scoliosis-Related Lung Issues
Management strategies focus on either preventing the curve’s progression or correcting the deformity to improve thoracic volume. In growing patients with moderate curves, bracing may be used to halt curve progression and prevent the worsening of chest wall restriction. This proactive measure aims to preserve existing lung function by maintaining thoracic dimensions.
For severe curves, typically those above 40 to 50 degrees that are progressing or causing significant restriction, surgical intervention such as spinal fusion may be considered. The goal of surgery is to correct the spinal deformity, which restores space within the chest cavity for the lungs to expand more fully. This correction can prevent further decline in lung function and may improve respiratory capacity.
Non-surgical management includes respiratory rehabilitation programs involving structured breathing exercises and physical therapy. These exercises are designed to maximize current lung capacity and strengthen the respiratory muscles. For patients experiencing severe nocturnal breathing issues, noninvasive ventilation, such as using a BiPAP machine during sleep, may be utilized to ensure adequate oxygen and carbon dioxide exchange.