Author(s): YANASE, K., OKUDA, Y., Institution: DOSHISHA UNIVERSITY, Country: JAPAN, Abstract-ID: 2476

INTRODUCTION:
Shortening of the pectoralis minor is often a concern as it can lead to abnormal position and movement of scapula. In clinical practice, the distance between the posterior border of the acromion and the table (DistanceAT) is used to assess the length of pectoralis minor (1). An increase in the DistanceAT indicates the pectoralis minor shortening. Only a caliper is needed to measure this distance, hence, the measurement is highly practical in the rehabilitation field. However, this method does not directly measure the pectoralis minor length, therefore, it is unclear whether the measurement can measure the pectoralis minor length accurately. The purpose of this study was to clarify the validity between DistanceAT and shear modulus of pectoralis minor muscle.
METHODS:
Twenty-seven healthy young males participated in this study (21.4 ± 2.2 years, 173.4 ± 4.9 cm, 67.7 ± 8.1 kg). In the measurement of DistanceAT, they lay in a supine position with both arms placed alongside their body. One examiner confirmed their acromion of scapula by palpation, and measured the distance from the posterior border of the acromion to the table using a caliper. The validity was assessed against ultrasonic shear wave elastography (the gold standard), and shear moduli of the pectoralis minor and pectoralis major muscles (clavicular, sternal, and abdominal regions) were measured in supine position. The DistanceAT and the shear modulus were measured both left and right sides. Pearson correlation coefficient or Spearmans rank correlation coefficient were used to determine the association between the DistanceAT and the shear moduli of all muscles.
RESULTS:
The average values and standard deviations for each data were as follows: DistanceAT (left: 5.7±1.3cm, right: 5.8±1.7cm), shear modulus of pectoralis minor (left: 7.4±2.9kPa, right: 7.9±3.8kPa), shear modulus of pectoralis major (clavicular) (left: 20.1±6.1kPa, right: 17.3±3.7kPa), shear modulus of pectoralis major (sternal)(left: 16.8±4.6kPa, right: 15.8±3.7kPa), and shear modulus of pectoralis major(abdominal) (left: 15.7±4.3kPa, right: 15.2±4.1kPa). No significant correlations were found between the DistanceAT and the shear moduli of all muscles.
CONCLUSION:
The findings of this study suggest that the DistanceAT cannot estimate pectoralis minor shortening. The DistanceAT is probably influenced by various factors, such as muscle mass and skeletal size. Therefore, further research is necessary to adjust for these factors.