Optimising the Investigation of Interventional Treatments in Lateral Elbow Tendinopathy

Abstract

Background and Aim Lateral Elbow Tendinopathy (LET) is a common, painful condition, predominantly affecting working age people. Although numerous studies have been conducted assessing a multitude of therapeutic interventions, fundamental information regarding outcome measure choice, treatment delivery techniques, and trial feasibility have not been explored. This thesis aims to optimise the investigation of interventional therapies in lateral elbow tendinopathy by furthering the foundational knowledge from which future researchers can inform their study design. Methods A portfolio of studies was undertaken to explore three main themes: the choice of patient-centred outcome measure, the rationale for injection therapy technique and the feasibility and acceptability of a randomised controlled study methodology in Platelet-Rich Plasma (PRP) injection therapy. Seven studies addressing these themes were undertaken: a three-phase systematic review and standardised evaluation of patient-centred clinical rating systems in elbow pathology, a validation study of outcome measures in a UK population of lateral elbow tendinopathy patients, a cadaveric assessment of elbow injection distribution, a Delphi consensus study of PRP injection use and a feasibility randomised controlled trial of PRP versus surgery for chronic LET. Results The systematic review identified 72 clinical rating systems used in elbow pathology, 15 of which had a history of validation in lateral elbow tendinopathy patients. Standardised comparative assessment found that only four reached the minimum threshold for recommendation (QDASH, DASH, OES and PRTEE). The correlation between the frequency of clinical rating systems use and their performance was r = 0.35. Cross-culturally specific validity of these rating systems in a UK population was limited to 20 patients embedded in mixed pathology cohorts. Evaluation of the psychometric properties of the highest performing clinical rating systems was performed in 50 tendinopathy patients recruited across general practice, physiotherapy and secondary care settings, with all instruments achieving adequate internal consistency (Cronbach's alpha >0.87), reliability (intraclass correlation coefficient >0.85) and responsiveness (effect sizes >0.46). The cadaveric evaluation found no statistical difference between the intratendinous distribution of lateral elbow injections between 1ml and 3ml or between single shot or fenestrated injection techniques. The Delphi consensus study on the application of platelet-rich plasma injections found poor levels of agreement amongst experts on the technical preparation and application of this treatment. The feasibility randomised control trial found that a randomised controlled trial is technically feasible (86% recruitment rate, 8% drop-out and 8% cross-over). Qualitative interviews with these patients identified very high levels of procedural injection pain. Conclusion This research improves upon the knowledge base from which future evaluations of interventional treatment in lateral elbow tendinopathy can be constructed. It is the first one to identify the wide choice and disparate utility of patient-centred outcome measures in elbow pathology. It can recommend the QDASH, DASH, OES or PRTEE for use in the English language and provides evidence of the validity and reliability of these instruments in the UK. Injection methodology should be rationalised to low volume single-shot injections, and research priorities should be allied to areas identified as lacking expert consensus. Though feasible and acceptable, future parallel group studies should quantify and report procedural pain.