# Effect of Contralateral Cervical Glide on the Suprascapular Nerve: An In Vitro and In Vivo Study
## 3 Results
### In Vivo Study  
In all the videos analyzed, a significant difference was recorded between the displacements of the movement point and the control point, which confirmed that nerve movement was indeed detected. All movement values were provided with 95% non-parametric confidence intervals using bootstrapping methods. This approach was chosen because the assumption of normality was not validated (\(p\)-values below the significance level \(\alpha=0.05\)), and the sample size was not large enough to rely on parametric methods. Bootstrapping allowed us to estimate a more robust measure of the observed nerve displacement. All statistical analyses were performed using Minitab statistical software (version 21, Minitab LLC, State College, PA, USA).  
The presence of a vertical displacement value suggested that aligning the ultrasound head longitudinally with the nerve was not feasible. Considering the anatomy and course of the SNe, it was not possible to rectify this error. Therefore, it was decided to analyze and supply information on both horizontal and vertical displacements, as both motion components were recorded.  
The CLCG resulted in a proximal glide of the SNe toward the spine, both at SNo level and at SGN level. In Video S1, recorded at SNo level, a CLCG resulted in a horizontal medial movement of 1.18 mm of the SNe toward the spine and a vertical cranial movement of 0.39 mm (see Figure 4 and detailed values in Table 1). In Video S3, the same maneuver moved the SNe horizontally and laterally toward the SGN by 1.65 mm, and vertically and cranially by 0.34 mm at the infraspinous fossa level (see Figure 5 and detailed values in Table 1).  
Figure 4: A CLCG observed at SNo by ultrasound. 1: scalene muscles; 2: ombyoid muscle; 3: suprascapular  
nerve; CLCG: contralateral cervical glide. 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 CLCG. This example of Video S1 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. Vertical lines are provided from the top image to show the displacement of the points between captures. Specifically, in this example, the control point not only showed a lower magnitude of movement than the nerve points, but it also moved in the opposite direction.  
The isometric infraspinatus muscle contraction resulted in a distal glide of the SNe toward the infraspinatus fossa, registered at the SNo level. In Video S2, an isometric external rotation contraction resulted in a horizontal lateral movement of 1.34 mm of the SNe and a vertical caudal movement of 0.75 mm (see Figure 6 and detailed values in Table 1).  
Figure 5: A CLCG observed at the infraspinous fossa by ultrasound. 1: scalene muscles; 2: omohyoid muscle; 3: suprasecapular nerve; CLCG: contralateral cervical glide. 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 CLCG. This example of Video S3 was recorded on a left shoulder. The directions of the infraspinous muscle and the SGN are indicated by red and purple, 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 at least one of the nerve points toward the SGN.  
Ultrasound imaging did not confirm the presence of the anatomical variation detected during dissection.