Rotator cuff tendinopathy: an investigation of extrinsic and intrinsic mechanisms using ultrasound imaging

Rotator cuff (RC) tendinopathy is a common cause of shoulder pain, and can result in significant and prolonged pain and disability in adults. Surgical interventions to treat RC tendinopathy are costly and invasive, with conservative management primarily involving exercise therapy demonstrating at least equivalent effectiveness. However, conflicting opinions and evidence regarding the aetiology of this disorder has led to a lack of specificity of rehabilitation programmes or surgical approaches. Proposed mechanism of RC tendinopathy are: extrinsic mechanisms, which describes external compression of the RC tendons from the coracoacromial arch; or intrinsic mechanisms, which includes factors directly influencing tendon health such as loading, genetics and ageing. This thesis examined the interaction between two factors i.e. acromiohumeral distance (AHD), and supraspinatus tendon (SsT) thickness, representing extrinsic and intrinsic factors respectively. Chapter 2 of this thesis describes a series of methodological studies, examining reliability and validity of these measures. These studies demonstrated that ultrasound imaging can be used to undertake reliable and valid measures of AHD and reliable measures of SsT thickness in both RC tendinopathy and painfree populations. As part of a study examining the validity of AHD measurement, a novel shoulder ultrasound phantom was developed which has potential to act as a training tool for shoulder ultrasound examinations and/or injections. The studies in Chapter 3 examined differences in AHD and SsT thickness in a group of people with RC tendinopathy compared to painfree controls, both cross-sectionally and also in response to a bout of fatigue loading. Acromiohumeral distance is not significantly reduced in those with painful RC tendinopathy (without RC tears) compared to controls. However, the SsT was found to be thicker in those with moderately or severely painful RC tendinopathy, potentially indicating primary intrinsic tendon changes. Additionally, the thickened tendon led to an overall increased subacromial occupation ratio, which may contribute to secondary extrinsic tendon compression. In RC tendinopathy, fatigue loading results in a prolonged (>6hours) reduction in AHD and an increase in SsT thickness, compared to findings of a transient change in AHD (<6 hours) and miminal reduction in tendon thickness in painfree controls. While undertaking research to provide evidence for practice is critical to building the knowledge base in physiotherapy, a further important consideration is how this knowledge is translated to, and used in, clinical practice. Chapter 5 of this thesis describes the delivery and evaluation of a Community of Practice (CoP) within Primary Care physiotherapists, focused on improving evidence-based knowledge translation in shoulder pain. This qualitative study found that the CoP therapists gained multiple benefits from their involvement including peer support, increased use of research evidence, and increased confidence in their clinical practice and research utilisation skills. The CoP project also resulted in the production of a website (www.shouldercommunity.com) designed to provide evidence-based information about shoulder pain to therapists and patients. In conclusion, this thesis provides further evidence supporting intrinsic tendinopathy as a mechanism of RC tendinopathy. Potential interactions with extrinsic mechanisms are explained through changes in the subacromial occupation ratio. The findings of the fatigue loading study provide guidance to clinicians on exercise prescription in RC tendinopathy. The CoP provided a successful means of improving knowledge transfer to clinical practice for Primary Care physiotherapists, which could be transferred to other practice areas and settings.