[Measurement and evaluation of the quadriceps muscle mass in young men based on magnetic resonance imaging].

OBJECTIVE: To investigate the correlation between the quadriceps cross-sectional area (CSA) and quadriceps muscle volume (QMV) at different horizontal levels from the upper edge of the patella, and to determine the best observation position. METHODS: Thigh magnetic resonance imaging (MRI) images of 22 Chinese young men [age: (29±6) years] with anterior cruciate ligament (ACL) rupture were examined. The CSA was measured at 18, 15, and 12 cm above the upper edge of the pate-lla (denoted by CSA-18, CSA-15 and CSA-12 respectively), and the QMV and CSA were determined by semiautomatic segmentation. A curve model was established to estimate QMV. Bland-Altman analysis was performed to determine the confidence limits of the volumes. RESULTS: On the unaffected side, the mean QMV was (1 944.45±323.77) cm3. The quadriceps CSA at the upper edge of the patella at 18, 15, and 12 cm was (80.80±12.16) cm2, (77.53±12.03) cm2, and (72.68±10.51) cm2, respectively. The coefficients of determination (R2), ascertained using curve estimation models, for the 3 positions were 0.819, 0.755, and 0.684 (P < 0.001), and the standard deviations of the volume estimated value (SEE) were 7.4%, 8.7%, and 9.8%. The fitting equations of the three horizontal positions were all good, but the fitting degree of CSA-18 was the highest. The Bland-Altman scatter plot showed that the arithmetic means of the QMV at 18, 15 and 12 cm from the upper edge of the patella 0.8 cm3, -1.1 cm3, and 0.9 cm3 and 95% limits of agreement (LoA) were (-268.8, 270.5), (-315.2, 313.1), and (-355.7, 357.5), respectively. The estimated QMV was in good agreement with the measured value. The difference between the estimated CSA-18 and measured values was the smallest. The results on the affected side were consistent. CONCLUSION: The correlation between QMV and CSA in the young men with the upper edge of patella as baseline was reliable and consistent. Among them, CSA-18 had the highest correlation with the QMV. However, different observation sites could be selected for different injuries of the quadriceps.