Corticosteroid injection and physiotherapy are common treatments of lateral epicondylalgia, clinically prescribed in isolation or combination. In an era where evidence based practice is paramount, it is apparent that questions regarding the true efficacy of corticosteroid injection and the potential superiority of a combined intervention of injection and physiotherapy are currently unanswered. In addition, the aetiology of this condition is not completely understood, in particular the mechanisms underlying pain and disability, and prognosis. Investigation of sensory, motor and psychological factors have mostly been limited to small, isolated cross-sectional studies. Study of a larger cohort with longitudinal follow-up may facilitate improved knowledge of the relationship between these factors and help identify mechanism-based treatments for individuals at risk of poorer recovery. The aims of this thesis were to investigate the clinical efficacy of corticosteroid injection, physiotherapy or both, in the treatment of lateral epicondylalgia and improve our understanding of the potential mechanisms underlying pain and disability, and prognosis.
Systematic review of high quality published trials evaluating injections (including corticosteroid) for tendinopathy was performed. For lateral epicondylalgia, corticosteroid injection demonstrated large benefits at four weeks but worse outcomes at six and 12 months compared to many conservative interventions, including physiotherapy. However significant heterogeneity was found for studies with a placebo injection comparison. The main focus of this thesis was a randomised controlled trial with one year follow-up of 165 participants with lateral epicondylalgia. A factorial design was used to investigate the efficacy of corticosteroid injection relative to placebo injection, as well as the ability of physiotherapy to optimise injection. In comparison to a blinded injection of normal saline, corticosteroid injection resulted in greater success in the short term but lower success at six and 12 months and was associated with significantly higher recurrence. Contrary to our hypothesis, addition of physiotherapy to an injection did not change success or recurrence rates or any other outcomes at one year. However, physiotherapy (plus placebo injection) reduced the use of analgesic and anti-inflammatory medication and resulted in greater short term success compared to placebo injection alone. On the basis of these two studies, we recommend that corticosteroid injection be avoided in the routine management of lateral epicondylalgia.
Cross-sectional studies were undertaken to investigate whether physical and psychological characteristics differed between mild, moderate and severe lateral epicondylalgia and healthy controls. Whilst some features, such as pain-free grip impairment and widespread mechanical hyperalgesia were evident regardless of severity, others were present only in participants with more severe pain and disability, including bilateral cold hyperalgesia, unilateral heat hyperalgesia. Anxiety, depression and kinesiophobia did not differ between mild, moderate and severe lateral epicondylalgia subgroups. Small deficits of elbow extensor and flexor strength were also evident in individuals with lateral epicondylalgia in comparison to healthy controls. Positive manual examination was more common in lateral epicondylalgia than controls, at C4-7 cervical levels both ipsilateral and contralateral to the side of injury. The multisensory hyperalgesia displayed in individuals with severe lateral epicondylalgia may implicate a combination of central, peripheral and sympathetic nervous system processes and help explain the poorer outcomes found in patients with severe lateral epicondylalgia.
Post-hoc analysis of data from the randomised controlled trial was undertaken to study the predictive capacity of physical and psychological characteristics on pain and disability, and two characteristic features of lateral epicondylalgia - mechanical hyperalgesia and pain-free grip. Short term pain and disability was predicted by greater cold hyperalgesia and baseline pain and disability, the latter also predicting a poorer long term prognosis. Short and long term mechanical hyperalgesia as measured by pressure algometry at the elbow, was predicted by a combination of cold hyperalgesia, female sex and baseline pressure pain threshold. In addition, cervical spine manual examination and fear-related activity avoidance predicted persistent long term mechanical hyperalgesia. Lower pain-free grip was found in females with lower baseline pain-free grip, and in the long-term positive cervical spine examination. These findings suggest cold hyperalgesia may assist in the early identification of patients at risk of persistent symptoms, and warrant greater attention toward the cervical spine and kinesiophobia.
The studies in this thesis may be used to inform clinical practice guidelines on the utility of corticosteroid injection and physiotherapy. Furthermore a unique insight into the physical and psychological factors associated with pain and disability and prognosis may offer novel direction for future research and ultimately improve the outcomes in patients with lateral epicondylalgia.