ANALYSIS OF RECRUITMENT OF THE SUPERFICIAL AND DEEP SCAPULAR MUSCLES IN PATIENTS WITH CHRONIC SHOULDER OR NECK PAIN, AND IMPLICATIONS FOR REHABILITATION EXERCISES BIRGIT CASTELEIN Thesis submitted in fulfillment of the requirements for the degree of Doctor in Health Sciences Ghent University, 2016 PROMOTOR Prof. Dr. Ann Cools Ghent University, Ghent, Belgium CO-PROMOTOR Prof. Dr. Barbara Cagnie Ghent University, Ghent, Belgium SUPERVISORY BOARD Prof. Dr. Lieven Danneels Ghent University, Ghent, Belgium Prof. Dr. Erik Achten Ghent University, Ghent, Belgium EXAMINATION BOARD Prof. Dr. Lori Michener University of Southern California, Los Angeles, USA Prof. Dr. Filip Struyf University of Antwerp, Antwerp, Belgium Dr. Katie Bouche Ghent University Hospital, Ghent, Belgium Prof. Dr. Damien Van Tiggelen Ghent University, Ghent, Belgium Prof. Dr. Jessica Van Oosterwijck Ghent University, Ghent, Belgium TABLE OF CONTENTS GENERAL INTRODUCTION .................................................................................................................. 1 1. The role of the scapula in normal upper limb function ................................................................... 4 2. Scapulothoracic muscle recruitment during arm elevation .............................................................. 6 2.1 Superficial lying scapulothoracic muscles ................................................................................. 6 2.2 Deeper lying scapulothoracic muscles ...................................................................................... 7 3. Scapular dyskinesis and its contributing factors ................................................................................ 9 4. Scapular dyskinesis and altered muscle recruitment in relation to shoulder and neck pain ........ 13 4.1 Alterations in scapulothoracic (muscle) function in patients with shoulder pain ........................ 13 4.2 Alterations in scapulothoracic (muscle) function in patients with idiopathic neck pain ............. 16 5. Outcome of scapula focused rehabilitation programs .................................................................... 18 6. Scapulothoracic muscle recruitment during exercises .................................................................... 20 7. Outline and aims .............................................................................................................................. 23 8. Bibliography ..................................................................................................................................... 25 PART I: SCAPULOTHORACIC MUSCLE RECRUITMENT IN PATIENT POPULATIONS WITH SHOULDER OR NECK PAIN .................................................................................................... 35 [Chapter 1] Optimal normalization tests for muscle activation of the Levator Scapulae, Pectoralis Minor, and Rhomboid Major: An electromyographic study using Maximum Voluntary Isometric Contractions. ……………………………………………………………………………………………………………………….37 [Chapter 2] Scapulothoracic muscle activity during elevation tasks measured with surface and fine wire EMG: a comparative study between patients with subacromial impingement syndrome and healthy controls. ....................................................................................................................................... 53 [Chapter 3] Analysis of scapular muscle EMG activity in patients with idiopathic neck pain: a systematic review. ..................................................................................................................................... 69 [Chapter 4] Are chronic neck pain, scapular dyskinesis and altered scapulothoracic muscle activity interrelated?: A case-control study with surface and fine-wire EMG. .................................................. 101 PART II: SCAPULOTHORACIC MUSCLE RECRUITMENT DURING DIFFERENT EXERCISES, COMMONLY USED IN SCAPULAR REHABILITATION PROGRAM ............... 119 [Chapter 5] Superficial and deep scapulothoracic muscle EMG activity during different elevation exercises in the scapular plane. .............................................................................................................. 121 [Chapter 6] Serratus Anterior or Pectoralis Minor: which muscle has the upper hand during protraction exercises? ............................................................................................................................. 141 [Chapter 7] Modifying the shoulder joint position during shrugging and retraction exercises alters the activation of the medial scapular muscles. ...................................................................................... 159 GENERAL DISCUSSION ....................................................................................................................... 173 1. Summary and discussion of the results ......................................................................................... 175 2. Clinical implication of the results .................................................................................................. 184 3. Strengths and limitations ................................................................................................................ 188 4. Considerations for future research ................................................................................................ 190 5. Bibliography ................................................................................................................................... 192 SUMMARY ................................................................................................................................................ 199 NEDERLANDSE SAMENVATTING……………………………………………………………………………………..203 APPENDICES………………………………………………………………………………………………………………………..207 LIST OF ABBREVIATIONS .................................................................................................................. 217 General Introduction 1 GENERAL INTRODUCTION General Introduction 2 General Introduction 3 Chronic shoulder pain and neck pain are among the three most prevalent musculoskeletal disorders in the general population. Shoulder pain affects 22.3% of people, with a significant detrimental impact on health-related quality of life and physical functioning.51 Neck pain is a common musculoskeletal complaint with a 12-month prevalence of 30-50% in the adult population.52,53,54 Although examinations of patients with shoulder or neck pain typically focus on impairments of structures in the local region, structures distant from the shoulder and neck are generally recognized to also have an impact on these regions. The central linking structure between the shoulder and neck is the scapula and its surrounding scapular muscular system plays a major role in providing stability and mobility. The introduction of this dissertation will describe the function of the scapula and its surrounding (both superficial and deeper lying) muscles. In addition, altered scapulothoracic muscle recruitment in relation to shoulder and neck pain will be described. This introduction will mainly focus on scapular function during elevation of the arm. Humeral elevation is a functional movement during which the scapula plays an important role as it has to create a stable base for the glenohumeral joint. Also, an overview of the effect of scapula focused rehabilitation programs, performed in patients with shoulder pain and neck pain, will be given, followed by the current knowledge of scapulothoracic muscle recruitment during exercises, commonly used in those scapular rehabilitation programs. The last part of the introduction will present the aims of this dissertation. General Introduction 4 1. The role of the scapula in normal upper limb function The scapula functions as a bridge between the shoulder complex and the spine and connects the upper limb to the trunk. It articulates with the humerus to form the glenohumeral joint and with the clavicle forming the acromioclavicular (AC) joint. As no actual bony articulation exists between the scapula and the thorax, the scapulothoracic joint is one of the least congruent joints in the body. This allows mobility in many directions including translation movements (protraction/retraction and elevation/depression), and rotational movements (upward/downward rotation, anterior/posterior tilt and internal/external rotation) (Figure 1 and Figure 2). FIGURE 1. Motions of the clavicle: (A) protraction-retraction (superior view right shoulder), with ghosted image representing increased protraction (B) elevation-depression (anterior view right shoulder), with ghosted image representing increased elevation (C) anterior-posterior rotation (lateral view right shoulder) with ghosted image representing posterior rotation. Figure adapted from Ludewig et al.76 FIGURE 2. Kinematics of the scapula: (A) Internal-External rotation (superior view right shoulder), with ghosted image representing increased internal rotation (B) Upward-Downward Rotation (posterior view right shoulder), with ghosted image representing increased upward rotation, (C) Anterior-Posterior Tilting (lateral view right shoulder), with ghosted image representing increased posterior tilting. Figure adapted from Ludewig et al.76 General Introduction 5 It is widely recognized that the scapula is important as it has to create a stable base for centering the humeral head and channeling force production during daily activities and sport participation performed with the upper quadrant. During humeral