A double blind randomised control trial investigating the efficacy of platelet rich plasma versus placebo for the treatment of greater trochanteric pain syndrome (the HIPPO trial): a protocol for a randomised clinical trial

The source of recruitment will be from their main care provider (GP, orthopaedic surgeon, rheumatologist or extended-scope practitioner). Following the first interview and consent to enter the trial, eligibility checks (Table 1) will be repeated for each participant on the day they attend for treatment, to ensure that participants are not randomised in error. The participant will receive confirmation of their inclusion in the trial, which will also be recorded in their medical notes. Their GP will be informed.

The data collected from the trial will be entered into a trial database. The database will be agreed and set up by our information technology (IT) technician, statistician and PI. The database will be stored securely on our computer systems in the hospital. During the interim analysis, the database will be frozen to ensure data collected after this point are not included in the interim report. Access to the data will be limited to those only directly involved in the trial and who are part of the research team. The data will be anonymised in terms of participant identifiable data and will only contain demographic details. Identifiable participant data will be held on a separate database in our secure computer network in the hospital. Each participant will have a unique participant code so their outcome data can be matched with their personal identifiable data if required. All physical data will be stored in the Research and Development Office, North Tyneside General Hospital in a locked cabinet. The office is secured by a code-operated lock and is only accessible by the research team. All computer data will be stored on our secure password-protected National Health Service (NHS) Trust computers. Data will be archived in accordance with the Research and Development Department, Northumbria Healthcare NHS Foundation Trust guidance. A data monitoring committee will be formed and will convene for this trial.

Platelet-rich plasma (PRP) is an autologous blood product, which has a higher concentration of growth factors postulated to provide enhanced healing and anti-inflammatory properties. There have been numerous studies on the efficacy of PRP in musculoskeletal soft tissue conditions with similar pathology to GTPS, with varying results, the most promising being in plantar fasciopathy and patellar tendinopathy. Corticosteroids are the established second-line treatment, but do not always work long term. PRP may be a suitable alternative to corticosteroid in GTPS, with longer-term effects; however, there are very few reports discussing its efficacy. Lee et al. in 2016 [26] prospectively studied the efficacy of intra-tendinous PRP injections as treatment for chronic recalcitrant gluteus medius tendinopathy. They found ultrasound-guided intra-tendinous PRP injections to be a safe and effective treatment option for chronic recalcitrant gluteus medius tendinopathy due to moderate to severe tendinosis. A second report by Ribeiro et al. from Brazil [23] was published in 2016 comparing the efficacy of PRP against corticosteroids. They concluded that during the first 2 months, which was the study period, the PRP has no influence on pain relief and functional improvement in trochanteric syndrome. Again in 2016 a third report from the USA compared ultrasound-guided percutaneous tendon fenestration to PRP injection for treatment of GTPS [27]. The report concluded that both ultrasound-guided tendon fenestration and PRP injection are effective for treatment of gluteal tendinosis, showing symptom improvement in both treatment groups. Large effect sizes were evident in these studies. We calculated these based on Cohen’s test, taking some statistical assumptions into account, given that all data were not available. The effect sizes in the study of Lee et al. were 1.303, 1.052, 0.883 and 1.677 for the mHHS, Hip Outcome Score (HOS) activities of daily living, HOS sport and HOT-33, respectively. The effect sizes in the study of Ribeiro et al. were 1.155, 1.371 and 1.509 for the Facial Expressions Scale for Pain at follow up of 10, 30 and 60 days.

Prior to these reports, Mautner et al. conducted a study in 2013 [28] to assess whether ultrasound-guided PRP injections are an effective treatment for chronic tendinopathies. The study included 180 patients of whom16 had gluteus medius tendinopathy. The majority experienced significant improvement in symptoms, evidenced by 82% of patients reporting at least moderate improvement of their symptoms. A similar satisfaction rate of 85%was also found, respectively, demonstrating that the improvement in symptoms likely resulted in patient satisfaction. There are no randomised trials in the current literature and all these published reports were based on short follow up periods and small numbers of patients.

This paper describes the rationale and design for the first randomised trial that aims to determine the effectiveness of PRP in the treatment of greater trochanteric pain syndrome. No previous trials have assessed PRP against placebo or measured clinical outcomes beyond 6 months. The HIPPO trial will make a significant contribution to the evidence base available to support effective conservative management of GTPS.