The Spine Lifecycle

By Edward S. Pratt, M.D., M.B.A.

Our spines have a lifecycle just like we do. Although the spine changes profoundly through life, its primary roles do not. Those roles are; first, to support the head, neck, upper body, upper extremities, and trunk; and second, serve as a protective conduit for the spinal cord and nerves as they pass from the brain to their final destinations in the body.

When young, the spine is growing and very flexible. The discs are soft, fluid and thick with a very strong outer wall (annulus). The bones are often not fully developed and are still partly made of growth cartilage. At this age the spine can be deformed by trauma to an amazing degree, then recoil back into position and not break. Subsequently, athletes can sustain injuries with great temporary deformity, pinch nerves (stinger) or strain muscles without any obvious injury on X-ray. This hyper flexibility during growth can also permit progressive abnormal curves such as scoliosis and kyphosis to develop. These conditions unless very extreme, progress and change only during the adolescent growth years when the spine is flexible and growing. It is also during these early growing years that most primary tumors develop in the spine. Each of these problems cause back pain, and unlike adults with baseline arthritic changes or issues of secondary gain, young people with back pain, more often than not, have a diagnosable problem that should be addressed. The take home lesson here is, “Don’t ignore back pain in children and adolescents. In this age group, when there is smoke there is usually fire.”

Once growth is complete and our bones are fully mature many of the childhood spinal diseases stabilize. College age young adults usually continue to be active, but often begin to develop the kind of health habits that will get them into trouble later. Late nights in front of the TV or computer, hunched over preparing a term paper, causes fatigue in those muscles that support the neck and upper body. In an effort to keep the eyes steady while reading, great effort is required by the upper trunk and neck to keep the head motionless in space. Stiffness, fatigue, and muscle soreness can develop even in a young healthy spine as the areas under pressure are excluded from natural blood supply. Poor posture habits can begin to create significant mechanical dysfunctions even at this age.

By the time the spine is thirty years old, it is beginning to show the first signs of age. MRI (Magnetic Resonance Imaging) studies begin to show the first signs of disc arthritis at this age. People begin to become more sedentary and the confluence of poor posture, early arthritis and poor muscular conditioning begin to become evident. Activities that “were no problem” ten years before, now might cause several days or weeks of back or neck pain. These acute strains or sprains resolve in over 90% of cases, but the mechanical issues that precipitated them are still at work, making recurrence very likely. At this age, the discs also remain plump and fluid. Weaknesses or failures of the outer annular wall can allow disc material to flow out into the spinal canal impinging passing nerve roots, a condition known as a ruptured or herniated disc. As degeneration of the spine continues to progress, the peak load to failure of each tissue begins to decrease. In other words, they become weaker and easier to injure. It becomes ever more important to warm up and stretch before any major physical activity. More pliable muscles and joints will give more during activities, creating less stress and decreasing the chance of injury. Multiple small injuries some even unnoticed become additive, leading to advancing degenerative disease.

Once the resiliency of youth is behind us, our spines begin to take on a new character. The spine is considerably stiffer in older individuals. This stiffness allows the spine to satisfy its primary functions of body support and nerve protection despite the progressive degeneration of joints and bone. As the discs begin to age they lose the ability to attract water and begin to dehydrate. As a result they shrink and flatten, accelerating arthritic degeneration. This degeneration leads to increasing stiffness, bone spur formation and joint thickening. All of which can begin to compress passing nerves, a condition known as spinal stenosis. It can also lead to decreased body height. This progressive degenerative change can also lead to joints becoming unstable and moving in abnormal directions. Abnormal curvatures and instability develop in this age group more commonly than at any other age. Age also has a direct negative effect on the strength of the bones in our backs. Bone mass usually peaks in the mid thirties, and then gradually decreases throughout the rest of life. If extreme, this condition, known as osteoporosis, can lead to multiple fractures, pain, deformity, senescence and premature death.