Bone density loss after SCI

Question 1

When does bone mass occur following SCI?

Answer 1

occurs most rapidly in the first 4 months, and typically reaches a level approx. 2/3 that of pre-injured (able bodied values) within 16-24 months
-starts decreasing rapidly and then levels off
-much harder to increase bone density than muscle

Question 2

SCI may affect different bones to varying degrees:

Answer 2

Femur BMD may decline to 60-75% of able bodied values
-Tibia BMD may decline to 40-50% (the tibia has most of the weight of the body, so it loses the most bone density)
-radius BMD may decline to 75% in those with tetraplegia

Question 3

What is hypercalcemia?

Answer 3

abnormally high calcium levels in the blood
leads to nausea, vomiting, fatigue, weakness, cardiac arrhythmias, kidney failure

Question 4

What is spontaneous (pathological) fracture?

Answer 4

-incidence of 2-6% in individuals with SCI

Question 5

What are the mechanisms behind bone loss after SCI?

Answer 5

1. loss of weight bearing on bones: important but not the only factor as ASIA A and ASIA D have been shown to have similar BMD, BMD after SCI is far worse than that seen after immobilization studies or bed rest
2. reduction in the blood flow to bone (interosseous circulation)
3. drug therapies associated with SCI:
   spasticity and weight bearing activities (standing frame, long leg braces) may or may not have a positive effect on BMD after SCI
   bones need blood and oxygen, this will have an impact on bone density

Question 6

What is heterotopic Ossification after SCI?

Answer 6

The spontaneous formation of bone in muscle or connective tissue (most commonly in the hips, knees or elbows)
-incidence between 16-53% after SCI
-usually appears 1-4 months after SCI and matures 12-18 months later
-may restrict joint movement, cause pain and pressure sore development (may require surgery)
-the cause is unknown