Effects of Thoracic Spinal Manipulative Therapy on Thoracic Spine and Shoulder Kinematics, Thoracic Spine Flexion/Extension Excursion, and Pressure Pain Sensitivity in Patients with Subacromial Pain Syndrome

EFFECTS OF THORACIC SPINAL MANIPULATIVE THERAPY ON THORACIC SPINE AND SHOULDER KINEMATICS, THORACIC SPINE FLEXION/EXTENSION EXCURSION, AND PRESSURE PAIN SENSITIVITY IN PATIENTS WITH SUBACROMIAL PAIN SYNDROME By Joseph R. Kardouni, Ph.D., PT A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy, at Virginia Commonwealth University. Virginia Commonwealth University, 2013. Major Director: Lori A. Michener, PhD, PT, ATC, Professor, Department of Physical Therapy In patients with shoulder pain, the use of manual therapy directed at the spine and shoulder have been reported to provide superior outcomes to exercise based interventions or usual care without the use of manual therapy. Clinical trials have also reported improved pain and disability after thoracic spinal manipulative therapy (SMT) as a stand-alone treatment for shoulder pain. Although clinical efficacy is reported for the use of thoracic SMT for the treatment of shoulder pain, the mechanisms underlying the clinical benefits are not well understood. This limits the directed use of SMT. The benefits could be due to changes in spine or shoulder motion or neurophysiologic mechanisms of pain modulation. Elucidating the mechanism of manual therapy will aid the directed use of thoracic SMT for treating patients with shoulder pain. The research described in chapters 3 and 4 was performed to assess the effects of thoracic SMT in patients with subacromial pain syndrome with regard to biomechanical changes at the thoracic spine and shoulder and effects on central and peripheral pain sensitivity. Subjects with shoulder impingement pain symptoms were randomly assigned to receive 1 visit of thoracic SMT or sham SMT, applied to the lower, middle, and upper (cervicothoracic junction) thoracic spine. A 3-dimensional electromagnetic tracking system was used to measure thoracic and scapular kinematics during active arm elevation, and thoracic excursion at end-range of flexion and extension pre- post-treatment. Pressure pain threshold (PPT) was measured at the painful shoulder (deltoid) and unaffected regions (contralateral deltoid and bilateral lower trapezius areas) immediately pre- and post-treatment. PPT measures at the painful shoulder were used to assess peripheral and/or central pain sensitivity, and PPT at unaffected regions measured central pain sensitivity. Patient-rated outcomes measures of pain (Numeric Pain Rating Scale-NPRS), function (Pennsylvania Shoulder Score-Penn), and global rating of change (GROC) were used to assess changes in clinical symptoms following treatment. No significant differences were found between treatment groups for the thoracic kinematics or excursion, shoulder kinematics, PPT measures, or patient-rated outcomes. No differences were noted pre- to post-treatment in either group for thoracic kinematics or excursion or PPT measures. In both groups, there was a decrease in mean scapular external rotation over time during ascending arm elevation, but the change was less than measurement error. Outcome measures of NPRS, Penn and GROC indicated clinical improvements in both groups following treatment, but there were no differences between the thoracic SMT or sham SMT groups. There were no meaningful correlations between thoracic and scapular kinematics or thoracic excursion with the outcome measures of NPRS, Penn, or GROC. There was a significant positive correlation (r=0.52 , p=0.009) between change in PPT at the lower trapezius on the unaffected side and baseline Penn scores. Biomechanically, thoracic spine extension and excursion did not change following thoracic SMT, and the SMT group had no greater changes in shoulder kinematics or patient-rated pain and function than the sham SMT group. Additionally, thoracic SMT did not improve peripheral or central pain sensitivity as measured by PPT. Furthermore, improvements in patient-rated outcomes were not found to be related to changes in thoracic spine mobility, or shoulder kinematics with SMT. The single correlation between change in PPT and baseline Penn may indicate a neurophyciologic effect of SMT in patients with higher baseline function scores, but the since no other significant relationships between PPT and outcome were seen, the implications of this finding are limited. Overall, alterations in thoracic spine mobility and pressure pain sensitivity do not appear to be responsible for improved outcomes in patients with subacromial pain syndrome. Future studies should explore the effects of SMT using other measures of thoracic spine motion and experimental pain modalities, as well as greater dosing of SMT over a longer follow-up.