The aim of the study was to measure the cross-sectional area of the psoas major muscle (P-ACSA) in high school athletes and to produce a P-ACSA index independent of body size using an allometric modeling approach to examine the differences in gender and sport specialization. The subjects were 254 female (16.8±0.8 yrs) and 540 male (16.9±0.8 yrs) high-level high school athletes from 17 different sports. Fat-free mass (FFM) was measured by the Bod Pod system (LMI) and P-ACSA was determined by magnetic resonance imaging at the center of the L4-L5 transverse level. Since the power function model fit the data better than a simple linear model in the correlation between FFM and P-ACSA, and the power exponent parameter was almost equal to the theoretically anticipated 2/3 in both genders, the P-ACSA per FFM^2/3 as well as the absolute P-ACSA was calculated. Both of the absolute P-ACSA and P-ACSA per FFM^2/3 were significantly different according to gender and the sport specialization. While volleyball and badminton players and canoeists showed smaller P-ACSA, in accordance with the previous studies on senior sprinters, high school sprinters also showed predominant development of P-ACSA regardless of gender. These results suggested that regular involvement in sprinting activity could affect the size of the psoas major muscle in high school athletes.

In the present study, we examined the sex-related differences and cross-sectional age-related changes in the cross-sectional area of the psoas major muscle. The cross-sectional area was corrected for fat-free mass (FFM-corrected), which was calculated as the 2/3rd power of the total fat-free mass. A total of 240 adults (114 men, 126 women, age: 20-81 years) were included in the study. The cross-sectional area of the psoas major muscle was measured by 0.2T magnetic resonance imaging (MRI), and the total fat-free mass was measured by air displacement plethysmography. We demonstrated that the FFM-corrected cross-sectional area of the psoas major muscle was greater in males than females across all age groups. Furthermore, we examined the mean FFM-corrected cross-sectional area of the psoas major muscle across different age groups and demonstrated that it decreased with age. Our findings, when combined with previous results, show a peak in the 20s, which declined with age. Our study revealed sex-related differences and cross-sectional age-related changes in the FFM-corrected cross-sectional area of the psoas major muscle. Our findings also suggest that it is important to define reference values and ranges that take into account age- and sex-related differences when assessing the psoas major muscle by FFM-corrected cross-sectional area.

A premature boy was born after 35 weeks gestation (1,561 g in weight) with a diagnosis of anomalous origin of the right pulmonary artery from the ascending aorta (AORPA) and perimembranous ventricular septal defect (VSD). The fourteenth day after birth, banding of the right pulmonary artery was performed as a palliative operation. At the age of 5 months (3.9 kg in weight), the right pulmonary artery branched from the ascending aorta, and was anastomosed to a flap made by the lateral wall of the main pulmonary artery with pericardial patch augmentation. VSD patch closure was performed concomitantly. Severe stenosis of the right pulmonary artery compressed by the ascending aorta and left pulmonary hypertension were revealed 3 weeks after the repair. At the age of 11 months, a surgical relief of the right pulmonary artery stenosis was performed. Transection of the ascending aorta provided an excellent exposure of the right posterior pulmonary artery. After patch plasty of the stenotic pulmonary artery, the divided ascending aorta was restored using a strip form patch on 4/5 circle of its posterior wall to extend the aorta and widen the space for the right pulmonary artery. This technique preserves growth potential of the ascending aorta. There are few reports of surgical repair of AORPA with VSD in low birth weight infants. We presented here a case with surgical relief of post-operative right pulmonary artery stenosis. Long term observation of repaired right pulmonary artery, and requiring residual slight hypertension of the left pulmonary artery.