Epimuscular myofascial force transmission between the levator scapulae muscle and the upper fiber of the serratus anterior or rhomboid minor muscles.

BACKGROUND: This study investigated the epimuscular myofascial force transmission between the levator scapulae, serratus anterior, and rhomboid minor muscles. METHODS: The participants included 10 healthy males (a total of 20 shoulders). Differences in the shear moduli of the levator scapulae, serratus anterior, and rhomboid minor muscles were measured in the resting and levator scapulae stretching positions using shear wave elastography. The correlation between the rates of change for each muscle was also verified. FINDINGS: The results demonstrated a notable increase in the shear modulus from the resting to stretching positions for levator scapulae (42.9 ± 17.6 kPa vs. 52.4 ± 15.2 kPa) and serratus anterior (32.8 ± 12.9 kPa vs. 58.4 ± 18.5 kPa) (P = 0.02, P < 0.01). However, there was no significant difference in the shear modulus for the rhomboid minor between the resting (44.0 ± 19.2 kPa) and stretching (41.0 ± 20.2 kPa) positions (P = 0.40). Moreover, a significant positive correlation was observed between rates of change for the levator scapulae and serratus anterior muscles (P = 0.04, r = 0.459). INTERPRETATION: These findings indicate that the shear modulus of the serratus anterior increased with the stretching of the levator scapulae, suggesting the occurrence of epimuscular myofascial force transmission between these two muscles with different muscle insertions.

Changes in blood flow in the dorsal scapular artery and relationship to shoulder joint function in rotator cuff tears.

Background: One of the pain-related factors in rotator cuff tears (RCTs) is abnormal scapular motion, which is thought to be related to the levator scapulae muscle activation. Additionally, attention has recently focused on the peak systolic velocity (PSV) as one of the causes of pain, but blood flow outside of the vessels supplying the rotator cuff has not been clarified. This study aimed to determine the difference in PSV in the dorsal scapular artery (DSA), which is the vessel that supplies the levator scapulae muscles, and the association between PSV and pain and shoulder function in patients with RCTs between the tear and nontear sides. Methods: This study included 31 patients with RCTs with tear and nontear sides. Magnetic resonance imaging and radiographic examinations included Cofield classification, Goutallier classification, thickening of the coracohumeral ligament, and measurement of the acromiohumeral interval. Clinical evaluation included an automatic range of motion (ROM) for flexion, abduction, and external rotation (ER), a visual analog scale, and the Shoulder36. PSV was evaluated using ultrasound pulsed Doppler mode to assess PSV of DSA. The PSV of DSA on the first rib was drawn in the medial aspect of the suprascapular angle in the long axis, and the maximum PSV waveform was measured three times. The average value was used for further analysis. Results: The PSV in the DSA was significantly higher (P = .04, 95% confidence interval: 0.2-7.6) on the tear (22.6 ± 7.4 cm/s) than the nontear sides (18.9 ± 6.9 cm/s). In addition, a significant negative correlation (r = -0.46, P = .0087) was found between PSV in DSA and ER on the tear side. Conclusion: This study revealed a significantly increased PSV in the DSA on the tear side in RCTs and negatively correlated with ER ROM. The results suggest that increased PSV in the DSA may contribute to ER ROM limitation in the glenohumeral joint.