Osteopathic Clinical Practice and Research 1
SHOULDER IMPINGEMENT SYNDROME: THE EFFECT ON SERRATUS ANTERIOR, UPPER TRAPEZIUS AND DELTOID DURING SHOULDER ABDUCTION
BY ANDREW MCLEOD
PROJECT SUPERVISORS: DR SANDRA GRACE AND DR ZAC CROWLEY
Shoulder impingement is one of the most common conditions affecting the shoulder. According to Neer (1972), shoulder impingement accounts for between 44-65% of all cases of shoulder pain. Whilst its occurrence is common, shoulder impingement is also commonly misunderstood and difficult to diagnose (Cools et al., 2003). The term ‘shoulder’ will be described in detail in the anatomy section of the body of this paper. In short, it refers to the shoulder joint complex, which comprises three separate joints, being the scapulothoracic, acromioclavicular and glenohumeral joints and their respective skeletal, ligamentous, muscular, vascular and nervous components. The term ‘impingement’ in the context of the shoulder usually refers to compression and mechanical abrasion of various components of the shoulder during certain types of movement, such as elevation (Neer, 1972). This, however, is not the only meaning of impingement. Other meanings of impingement identified in the literature include tension overloading, friction and abrasion of the various shoulder tendons. Neer (1972) coined the term ‘impingement syndrome’ as a means of describing the full range of rotator cuff disorders, which could not be differentiated by clinical signs alone (Papadonikolakis et al., 2011).
There exists a vast amount of research on the topic of shoulder impingement, with a Google Scholar search returning some 28,000 articles, spanning a broad range of disciplines including osteopathy, physiotherapy and exercise physiology. It is apparent from the literature that the term ‘shoulder impingement’ covers a broad range of symptoms and pathologies (Papadonikolakis et al., 2011) (Bandholm et al., 2006). Causes of shoulder impingement identified in the literature include both extrinsic factors, such as glenohumeral instability and acromioclavicular joint degeneration; and intrinsic factors, such as muscle weakness / imbalance, rotator cuff or biceps pathology and scapular dyskinesis. (Cools et al., 2007).
The frequent appearance of shoulder impingement across a variety of disciplines of clinical practice highlights the growing need to understand, diagnose and treat this complex disorder. A thorough understanding of the anatomy and shoulder kinematics is crucial in managing this condition.
There is a general consensus in the literature that overhead sports and occupations requiring repetitive overhead motion are some of the leading causes of impingement syndrome (Chang, 2004). The literature supports the hypothesis that the repetitive movements performed in those types of activities can cause attritional changes in the supraspinatus tendon due to its poor blood supply. Ludewig & Cook (2000) support this concept, stating that the vast majority of people with impingement syndrome relate their symptoms to athletic activities or occupations requiring frequent overhead use. Ludewig & Borstad et al., (2003) validate this statement by suggesting construction workers who are exposed to overhead work have high rates of shoulder pain and predisposed to functional loss and impingement syndrome.
There is a common concept that has been frequently highlighted across the band of literature. Many authors have furnished the concept that rotator cuff muscle activation and scapulothoracic timing, which contribute to shoulder kinematics, are incongruent with impingement syndrome and develop irregular and/or dysfunctional firing patterns. The objective of our study is to shed light on abnormal scapular mechanics with concomitant rotator cuff deficiencies and the effect this has on...