How does a spinal cord injury affect your body? Part 4 of 4.
Fourth of a series. Read part one (mobility, spasms, skin), part two (bowel, bladder, sex), and part three (heart, blood pressure, breathing).
This post will deal with musculoskeletal issues: muscles and bones. In addition to problems with mobility, not being able to use all four limbs has its other medical complications.
Overuse
Humans are meant to get around using the lower limbs. The hip is a stable but mobile ball-and-socket joint made for bearing weight and supporting the rest of the body. But with the loss of lower limb mobility, the upper limbs have to take over. The shoulder, unlike the hip, is not made for bearing weight. It is designed for helping you reach for stuff in all directions – above your head, behind your back, up in front. Instead of a ball-and-socket, the upper arm (humerus) meets the shoulder blade (scapula) in a very shallow cup in order to give the joint more range of motion in many directions. To compensate for this shallow cup, muscles and ligaments help stabilize and hold the shoulder joint together. These muscles have to work extra hard, because aside from the usual stabilizing the joint and reaching for things, they also have to do double duty to wheel a wheelchair or use crutches/walkers/canes and help with mobility. Because of this, people with SCI are prone to overuse injuries of the upper limbs – more often in shoulders and wrists.
How to prevent overuse? Strength training for the muscles involved is one way. Education about the correct way to propel a wheelchair and transfer in and out of the wheelchair also helps. A properly fitted wheelchair facilitates correct posture and biomechanics (efficient movements that generate enough force to move the chair, with the least amount of injury risk) can reduce overuse injury.
Osteoporosis
Osteoporosis is a medical condition in which bone becomes brittle and fragile (put another way, it is a decrease in bone density), making it prone to fractures. It often occurs when there is a deficiency in vitamin D or calcium, or due to hormonal changes. Many people are familiar with age-related osteoporosis – as we get older, bones become more fragile. But people with SCI lose bone density not just due to age, but also due to the inability to use their limbs and bear weight on them.
One of the things we learn in medical school is “form follows function” when it comes to bones. With walking and bear weight, you encourage bony tissue to form in response to the use of your limbs – your bones – to keep you upright. This is the reason why weight-bearing exercise is important in preventing osteoporosis, in addition to taking calcium and vitamin D supplements.
With SCI, a person usually cannot do weight-bearing exercises like walking, so bone does not have the reason to form stronger tissue (bone does not have reason to increase bone density). This, along with hormonal changes, put the person with SCI at risk for osteoporosis and fractures.
This educational page from the University of Washington has a good information and a video about osteoporosis, treatment and prevention (in case you don’t want to read!).
