Humeral Head Translation After a Suprascapular Nerve Block

Abstract

Subacromial impingement syndrome is the most common shoulder disorder. Abnormal superior translation of the humeral head is believed to be a major cause of this pathology. The first purpose of the study was to examine the effects of suprascapular nerve block on superior translation of the humeral head and scapular upward rotation during dynamic shoulder elevation. The secondary purpose was to assess muscle activation patterns during these motions. Twenty healthy subjects participated in the study. Using fluoroscopy and electromyography, humeral head translation and muscle activation were measured before and after a suprascapular nerve block. The humeral head was superiorly located at 60 degrees of humeral elevation, and the scapula was more upwardly rotated from 30 to 90 degrees of humeral elevation after the block. The differences were observed during midrange of motion. In addition, the deltoid muscle group demonstrated increased muscle activation after the nerve block. The study’s results showed a compensatory increase in humeral head translation, scapular upward rotation, and deltoid muscle activation due to the nerve block. These outcomes suggest that increasing muscular strength and endurance of the supraspinatus and infraspinatus muscles could prevent any increased superior humeral head translation. This may be beneficial in reducing shoulder impingement or rotator cuff tears over time.

Translational movement within the glenohumeral joint at different rotation velocities as seen by cine MRI

“…An advantage of MR scanning for the assessment of the humeral translation in this study is the non-invasive nature of the instrument and no need to prepare for the analysis. In fluoroscopic studies (Matsuki et al 2012 ; San Juan et al 2013 ), a biplane radiographic study (Bey et al 2008 ) and a motion capture study (Dal Maso et al 2015 ), the number of subjects was restricted due to radiation exposure (Bey et al 2008 ; Matsuki et al 2012 ; San Juan et al 2013 ) or to markers mounted into bone (Dal Maso et al 2014 , 2015 ). A three-dimensional (3D) MRI study attempted to scan continuous shoulder elevation (Pierrart et al 2014 ).…”

Electromyographic Activity of Shoulder Girdle Muscles in Patients With Symptomatic and Asymptomatic Rotator Cuff Tears: A Systematic Review and Meta‐Analysis

“…Furthermore, de Witte et al [21] suggested that decreased abduction torque by the supraspinatus and infraspinatus in the presence of a tear may be compensated for by increased deltoid activity, which, in turn may be associated with increased superior glenohumeral translation. Greater relative add uctor activity during isometric abd uction (lower AR) could be a compensatory strategy by the adductors to reduce the upwards, cranial humeral head translation evident with loss of rotator cuff function [20,38]. Cadaveric studies [39,40] suggest that latissimus dorsi, teres major, and pectoralis major are strong depressors of the glenohumeral head, along with the rotator cuff and long head of biceps brachii.…”

The effects of exercise type and elbow angle on vertical ground reaction force and muscle activity during a push-up plus exercise

“…This result is in accordance with Sciascia et al [ 32 ] while subjects performed the PUP exercise. During humeral elevation in the scapular plane, infraspinatus activity has been reported to be between 10% - 25% MVC [ 29 , 38 ]. Conversely, it has been shown that sidelying external rotation exercise and prone external rotation can elicit a great amount of EMG activity equal to 62% and 63% MVIC, respectively [ 32 , 39 ].…”