Osteoporosis plays a significant role in causing spinal deformities in older adults by weakening the bones of the spine, making them more fragile and prone to fractures. This condition is characterized by a reduction in bone mass and deterioration of bone tissue structure, which leads to porous, brittle bones that cannot support normal mechanical loads effectively. The vertebrae, which are the individual bones making up the spine, become especially vulnerable to compression fractures. These fractures occur when the front part of a vertebra collapses or flattens due to pressure, causing a loss of height in the vertebra and altering the spine’s natural alignment.
As osteoporosis progresses, the repeated occurrence of these vertebral compression fractures leads to a gradual collapse of multiple vertebrae. This collapse causes the spine to curve forward abnormally, resulting in a hunched posture often referred to as kyphosis or a “dowager’s hump.” This curvature not only changes the appearance but also affects the biomechanics of the spine, increasing stress on the surrounding muscles, ligaments, and other spinal structures. The altered spinal shape can reduce overall height and impair mobility, balance, and respiratory function in older adults.
The underlying mechanism of osteoporosis involves an imbalance between bone breakdown and bone formation. Normally, bone tissue is constantly remodeled through the coordinated actions of cells called osteoclasts, which break down old bone, and osteoblasts, which build new bone. In osteoporosis, osteoclast activity outpaces osteoblast activity, leading to net bone loss. Factors such as aging, hormonal changes (especially decreased estrogen after menopause), and deficiencies in calcium and vitamin D contribute to this imbalance. The weakened bone matrix becomes less dense and more fragile, increasing the risk of fractures even from minor stresses like coughing, twisting, or bending.
In addition to bone weakening, muscle degeneration around the spine also contributes to spinal deformities in older adults with osteoporosis. The muscles that support and stabilize the spine, particularly the paravertebral muscles like the multifidus and erector spinae, tend to lose mass and strength with age. This muscle atrophy is often accompanied by fat infiltration, which further reduces muscle quality and function. As these muscles weaken, their ability to maintain proper spinal alignment diminishes, placing more mechanical load on the vertebrae and passive spinal structures such as ligaments and discs. This creates a vicious cycle where spinal instability leads to more fractures and deformities, which in turn exacerbate muscle degeneration.
The combination of fragile vertebrae and weakened spinal muscles results in a spine that is less able to withstand normal forces and maintain its natural curves. Vertebral compression fractures cause localized pain and stiffness, which can limit movement and lead to further disuse and muscle weakening. Over time, the cumulative effect of multiple fractures and muscle deterioration leads to significant spinal deformities, including increased kyphosis and sometimes scoliosis (sideways curvature). These deformities can impair posture, reduce lung capacity, and increase the risk of falls and further fractures.
Furthermore, the altered spinal mechanics caused by osteoporosis-related deformities can affect nerve roots and the spinal cord, potentially causing neurological symptoms such as pain radiating to the legs, numbness, or weakness. The deformities also increase the mechanical burden on the remaining healthy vertebrae and spinal joints, accelerating degenerative changes and contributing to chronic back pain.
In summary, osteoporosis contributes to spinal deformities in older adults primarily by weakening the vertebrae and making them susceptible to compression fractures. These fractures cause vertebral collapse and abnormal spinal curvature. Muscle degeneration around the spine further compromises spinal stability and exacerbates deformities. Together, these changes lead to a hunched posture, reduced height, pain, and impaired function, profoundly affecting the quality of life in the elderly population.