Identifying and Assessing Inter-Muscular Fat at the Distal Diaphyseal Femur Measured by Peripheral Quantitative...

Inter-/intramuscular fat can be assessed with peripheral Quantitative Computed Tomography (pQCT) and is of interest as an indicator of "muscle quality." Typical pQCT scan sites (forearm, lower leg) have a low amount of inter-/intramuscular fat, however distal diaphyseal femur scan sites with conspicuous inter-/intramuscular fat have been identified as potentially more prudent scan sites, even in healthy adolescents. However, current state of the art analysis methods require labor-intensive manual segmentation of the scan. The purpose of the present study was to evaluate the reliability of a novel open source automated enclosing convex polygon approach (source code https://github.com/tjrantal/pQCT, commit cec9bce) to quantify inter-/intramuscular fat from femoral pQCT scans in healthy adults.

The distal diaphyseal femur (25% of tibial length from the knee joint towards the hip) of 27 adults aged 18-50 yr were scanned twice, 1 wk apart, using pQCT. Subcutaneous fat, muscle, inter-/intramuscular fat, and marrow areas, and corresponding densities were evaluated using a method we have reported previously, as well as the novel enclosing convex polygon method.

The session-to-session reliability of the assessments was fair to excellent using the previously reported method as indicated by intraclass correlation coefficient (ICC_2,1) ranging from 0.45 to 1.00, while the novel method produced excellent reliability (ICC_2,1 0.78-1.00).

Distal diaphyseal femur appears to be a potentially informative and prudent scan site for inter-/intramuscular fat evaluation with pQCT.