ULTRASOUND VERIFICATION OF SAFE NEEDLE EXAMINATION OF THE RHOMBOID MAJOR MUSCLE

Introduction: Palpation of a thoracic rib is a common method for reducing the risk of pneumothorax during electromyographic examination of the rhomboid major muscle, but its accuracy is unknown. Methods: Two physicians palpated healthy subjects to attempt to identify the center of a rib located beneath the rhomboid major muscle. The identified location was examined with ultrasonography to examine its accuracy and the subject's anatomical depths. Results: Forty-four subjects (88 ribs) were studied. Palpation demonstrated a 66.3% accuracy rate, with significantly more incorrect palpations seen with greater muscle thickness (P=0.004) and body mass index (P=0.037), but not adipose thickness, age, or skin thickness (P> 0.05). Discussion: Palpation of the ribs in an attempt to avoid inadvertent pneumothorax while examining the rhomboid major may be inaccurate, primarily in patients with large muscle bulk. We suggest a brief ultrasound evaluation before electromyography to gauge correct needle depth.