Why does bone mineral density reduce more drastically in the femoral neck compared to the lumbar spine under prolonged microgravity conditions?

💡 Explanation

The femoral neck experiences diminished weight-bearing stress under microgravity because the hip joint reaction forces are significantly decreased, leading to reduced bone remodeling stimulus. This contrasts with the lumbar spine, which still experiences loading from muscle contractions and internal organ weight; therefore, bone mineral density loss is greater in the femoral neck rather than in the lumbar spine.

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