The Effects of Thoracic Spine Manipulation in Subjects with Signs of Shoulder Impingement

Abstract

Shoulder impingement is the most common cause of shoulder pain. It is often described as mechanical irritation of the tendons of the rotator cuff or long head of the biceps due to compression against either the structures of the subacromial arch or the glenoid and glenoid labrum. Various treatment options exist to address impingement, and recent studies suggest thoracic spine manipulation may be a useful option. The purpose of this study was to assess changes in range of motion (ROM), pain and shoulder function both immediately post- and 7 to 10 days after receiving thoracic spine manipulations. We also attempted to identify changes in scapular kinematics and shoulder muscle activity associated with thoracic spine manipulation in subjects with shoulder impingement. Thirty subjects between the ages of 18 and 45 with signs of shoulder impingement participated in this repeated measures study. All subjects received both a mid-thoracic spine and a cervicothoracic junction manipulation. Changes in pain were assessed using an 11 point numeric pain rating scale. Subjects reported pain with performance of provocative testing (Jobes Empty Can, Hawkins-Kennedy and Neer's tests for impingement) as well as with performance of cervical rotation, thoracic spine flexion and extension and weighted humeral elevation. Shoulder elevation force production pre- and post- manipulation was assessed using hand-held dynamometry. Additionally, subjects completed the Penn Shoulder Score (PSS) and the Sports and Performing Arts Module of the Disabilities of the Arm, Shoulder and Hand (DASH) Questionnaire to assess shoulder pain and function 7 to 10 days post thoracic spine manipulation. Electromagnetic sensors tracked three-dimensional scapular and clavicular kinematics as well as cervical, thoracic and humerothoracic ROM. Surface electromyography data were collected from the infraspinatus, serratus anterior, and the upper, middle and lower trapezius muscles with loaded humerothoracic elevation. A repeated measures analysis of variance (ANOVA) was used to compare scapular orientation and muscle activity at 30, 60, 90 ad 120 degrees of humerothoracic elevation before and after spinal manipulation. Paired t - tests revealed significant decreases in pain [(Jobes 2.6 ± 1.1, Neer's 2.6 ± 1.3, Hawkins-Kennedy 2.8 ± 1.3; p<0.001 for all three tests) (weighted shoulder elevation 2.0 ± 1.5, p<0.001; cervical rotation 0.4 ± .9, p=0.039)] as well as improvements in shoulder function (Force production 5.5±3.1, PSS 7.7 ± 9.4 and DASH 16.4 ± 13.2; p<0.001 for each). No significant changes in any of the ROM assessments were observed. No changes in scapular or clavicular kinematics were observed, with the exception of small decrease in scapular upward rotation (p = .04). A small but significant increase in middle trapezius activity (p = .03) was detected; however, no other significant differences in muscle activity were observed following manipulation. Moreover, paired t-tests revealed no significant differences in muscle onset times after manipulation. The findings of this study indicate that thoracic spine manipulation may be an effective intervention to treat pain associated with shoulder impingement; however, the improvements associated with thoracic spine manipulation are not likely explained by changes in scapular kinematics or shoulder muscle activity. Thoracic spine manipulation did not substantially alter scapular kinematics or motor control at the shoulder.