Prediction of thigh skeletal muscle mass using dual energy x-ray absorptiometry compared to magnetic resonance imaging after spinal cord injury.

A rapid decline in lean mass (LM), fat-free mass (FFM) and increased intramuscular fat (IMF) predispose persons with spinal cord injury (SCI) to chronic medical conditions including dyslipidemia, insulin resistance, type 2 diabetes mellitus and cardiovascular disease. (1) To determine the relationship between dual energy x ray absorptiometry (DXA) and gold standard magnetic resonance imaging (MRI) LM values; (2) to develop predictive equations based on this relationship for assessing thigh LM in persons with chronic SCI. Cross-sectional predicational design. Clinical research medical center. Thirty-two men with chronic (>1 y post-injury) motor complete SCI. Participants completed total body DXA scans to determine thigh LM and were compared to measurements acquired from trans-axial MRI. MRI was used to measure whole muscle mass (MM), absolute muscle mass (MM) after excluding IMF, and knee extensor muscle mass (MM). DXA was used to measure thigh LM (LM) and (FFM). To predict MM LM was multiplied by 0.52 and yielded LM. LM predicted MM [= 0.90, standard error of the estimate (SEE) = 0.23 kg,  < 0.0001] and MM ( = 0.82, SEE = 0.28 kg, < 0.0001). LM predicted MM ( 0.78, SEE = 0.16 kg, < 0.0001). DXA measurements revealed an acceptable agreement with the gold standard MRI and may be a viable alternative for assessing thigh skeletal muscle mass after SCI.