A More Precise Electromyographic Needle Approach for Examination of the Rhomboid Major

Abstract

BackgroundSafe and accurate needle access to the rhomboid major (RM) during electromyography is challenging due to the overlying trapezius muscle and the risk of pneumothorax. ObjectiveTo investigate the RM anatomy associated with the trapezius using ultrasonography and to determine a safe and accurate needle insertion point for needle electromyography of the RM. DesignDescriptive study. SettingDepartment of physical medicine and rehabilitation of a tertiary clinic center. ParticipantsParticipants between 23 and 71 years of age without any diseases (N = 25; 13 men, 12 women; 50 scapulae) were included. InterventionsUltrasonography of the RM and trapezius muscles around the scapula. Main Outcome MeasuresThe point at which the lateral margin of the trapezius crosses the medial border of the scapula (point A) was determined. The probe was positioned at the level of the midpoint (point M) between point A and the inferior angle of the scapula. The horizontal distance from the point at which the RM was the thickest (point X) to point M was measured. At point X, the depth of the RM, RM thickness, and the depth of the pleura were measured. ResultsThe mean age and body mass index were 37.4 ± 12.0 years and 22.3 ± 2.1 kg/m2, respectively. Point M was located at a mean distance of 3.9 ± 0.6 cm proximal to the inferior angle of the scapula. The mean distance between point X and point M was 1.0 ± 0.2 cm. At point X, the RM was at a mean depth of 9.7 ± 3.1 mm from the skin and had a mean thickness of 9.9 ± 1.8 mm. The pleura was observed at a mean depth of 28.4 ± 3.8 mm from the skin. ConclusionNeedle electromyographic examination of the RM can be performed easily and safely through the lower part of the RM that is not covered by the trapezius. Level of Evidencenot applicable.