# Effect of Contralateral Cervical Glide on the Suprascapular Nerve: An In Vitro and In Vivo Study
## 4 Discussion  
This study investigated the mechanical behavior of the suprascapular nerve (SNe) using both cadaveric dissection and in vivo ultrasound imaging. Previous MRI-based simulations have shown that the SNe shifts from contacting the superior transverse scapular ligament (STSL) in the neutral arm position to the inferior portion of the suprascapular notch (SNo) during 90\({}^{\circ}\) abduction [17], although these findings were based on a single shoulder. This research showcased improved measurement accuracy through MRI, enabling precise investigation of the SNe location in relation to its bony structure. While a downward vertical shift of the SNe was demonstrated during shoulder abduction, no estimates were provided regarding its extent. Considering the SNe course, shoulder abduction might be viewed as a distal glide. This research demonstrated that the SNe distal glide during isometric contraction of the infraspinatus muscle, analyzed via ultrasound, also exhibited a caudal vertical component. In addition, this study confirmed the SNe glide by ultrasound in a larger sample, offering new insights into nerve mobility at the SNo. Comparing the findings of the current study with other dissection studies was challenging. The cadaveric study performed to investigate the joint movement combinations that increase the strain on the SNe, while validating the movement elements applicable both proximally and distally, did not provide data on the possible SNe glide or its direction [23]. Figure 6: An isometric infraspinous contraction observed at the SNo by ultrasound. 1: scalene muscles; 2: ombyoid muscle; 3: suprascapular nerve. The image shows two full screenshots of the ultrasound; the image on top was taken in the rest position, while the image on the bottom was captured at the end of the infraspinatus muscle contraction. This example from Video S2 was recorded on a left shoulder. The directions of the spine and the SNo are indicated by a light blue and yellow arrow, respectively. Three points were tracked: the blue and green points on the SNe and the pink point on the tissues surrounding the nerve. The image on top shows the rest position, and the image on the bottom shows the end of the maneuver position. Vertical lines are provided from the top image to show the displacement of the points between captures. The control point showed a lower magnitude of movement than the nerve points, while the nerve points showed a mean horizontal displacement of 1.34 mm toward the spine. Additionally, the current dissection phase had considerable limitations. The primary constraint was found in the examination of distal gliding since it is unfeasible to reproduce genuine muscle tone or contraction in cadavers. Furthermore, the sample size is limited, and it was essential to expose almost the entire nerve course for its examination. However, the existence and the direction of SNe proximal and distal glide were fully confirmed. To analyze whether the magnitude of movement recorded on the CLCG maneuver by dissection could be used as a guide, it was compared with those obtained in other studies of cervical movement in dissection. In this study, a contralateral lateral cervical glide (CLCG) produced greater SNe displacement than that reported for the median nerve during a similar cervical movement (2.25 mm vs. 0.71 mm) [39]. This difference may be due to variations in nerve length, anatomical path, and dissection methods. Unlike previous studies on the median nerve, our approach required full exposure of the SNe from the omohyoid level to the infraspinatus, potentially affecting its natural constraints. While the extent of movement noted in this study during its dissection phase must be interpreted with care, particularly the information gathered from the maneuver of approximating the origin and insertion of the infraspinatus muscle, the observation of the nerve gliding and its direction present new research opportunities.