PATH-2: Platelet Rich Plasma in Achilles Tendon Healing

PURPOSE The aim of this study is to evaluate the effectiveness of treating ruptured Achilles tendon with autologous platelet rich plasma. The investigators plan to compare the outcome of traditional methods of immobilisation in a cast with the outcome of the same methods after applying platelet rich plasma to the ruptured tendon.

Spontaneous rupture of the Achilles tendon is the most common tendon injury in the human body, it accounts for approximately 20% of all major tendon ruptures. Since the 1950s, the incidence of Achilles tendon rupture has been increasing. The peak incidence of ATR is between 30 and 40 years of age. Current treatments are associated with a significant risk of rerupture for the Achilles tendon; this is up to 15%. Therapies are currently dominated by the conflicting priorities of rapid rehabilitation and a return to work versus the risk of rerupture and/or surgery. New cost effective treatments that reduce both the risk of rerupture and time to functional healing are needed to address this challenge.

Platelets are blood cells that form blood clots in the injured tissues. Platelets have evolved over millennia to deliver a combinatorial wound healing cocktail that comprises over 1100 active soluble and membrane bound components, delivered sequentially over a timeframe from minutes to the lifespan of the platelets. Platelets and platelet derived growth factors play important roles in the healthy response to injury, promoting healing of tissues, and have been proposed as therapeutic agents. Their potential for tendon repair has been demonstrated in laboratory experiments and animal models. One human investigation has been published, a small study in athletes showing accelerated return to function with platelet preparations from patients own blood after complete Achilles tendon rupture. However, there has been no scientifically sound clinical research to assess the full potential of using platelet preparations to accelerate healing of Achilles tendon.

Despite that lack of high quality trial data, PRP administration remains a potentially attractive strategy to explore given it is of relatively low cost and minimally invasive. There has been a recent steep growth in PRP use for musculoskeletal conditions. It is estimated that PRP is used to treat 86,000 tendon disorders annually in the United States and a similar number in Europe.

There is also evidence that PRP injections are being introduced in NHS clinical practice, in addition to a wider use in private medicine within the United Kingdom. The investigators surveyed the declarations of use of PRP in NHS hospitals and discovered four offering PRP for tendon injuries. Without evidence of efficacy the consequences range from the NHS incurring extra costs for a treatment with unproven clinical effects to the non deployment of an effective autologous intervention. There is therefore a pressing need to undertake this study before the use of PRP becomes widely adopted. The results of this study may inform the design of a potential future clinical trial of optimal PRP therapy versus surgical repair for ATR in restoring patient function.

The National Institute for Health and Care Excellence (NICE) review of PRP use (IPG 438) states that specialist advisers noted that this was an established practice and it is of concern that participants are being exposed to these intervention techniques without adequate clinical investigation into their efficacy and validity. NICE encourages further research comparing autologous blood injections (with or without techniques to produce PRP) against established nonsurgical methods.

The proposed trial aims are:

1. Evaluate the clinical efficacy of PRP in acute ATR in terms of mechanical muscle tendon function.
2. Evaluate the clinical efficacy of PRP in acute ATR in terms of patient reported functional recovery, pain and quality of life.
3. Determine the key components of PRP that contribute to its mechanism of action.
4. Explore the immunohistochemical response of the healing tendon to PRP at the cellular and tissue level.

STUDY DESIGN Platelet Rich Plasma in Achilles Tendon Healing (PATH-2) is a pragmatic prospective multicentre, blinded, randomised, placebo controlled trial with two sub studies embedded within the main study. The study aims to evaluate the clinical efficacy of PRP in acute ATR in terms of mechanical muscle tendon function. To achieve the goals of this study and produce high level evidence of PRP efficacy, the study is a randomised controlled trial. The randomisation will reduce the risk of bias and the control arm will help to eliminate the placebo effect. Patients and assessors are blinded to the applied treatment to reduce the risk of bias.

The PATH-2 study will take place in a minimum of 15 NHS hospitals across the UK. Participants will be identified in the orthopaedic/trauma outpatient clinic, usually following an emergency hospital attendance for an Achilles tendon rupture. The investigators anticipate the surgeon will confirm appropriateness for nonsurgical treatment and eligibility. A member of the local research team will carry out the informed consent process, baseline data collection and randomisation.

Participants will be randomised via a telephone or website randomisation service, and will be allocated to receive either 'PRP injection' or 'Imitation (placebo) injection'. Treatment will be administered by a surgeon during the outpatient visit. Those involved in treatment delivery will be aware of treatment allocation due to the nature of the intervention. Participants should remain blind to allocation throughout the study.

There are blinded outcome assessments at 4, 7, 13 and 24 weeks and 24 months after treatment. For the first three (4, 7, 13 weeks) responses will be collected over the telephone or during a hospital outpatient visit (where this coincides with local follow-up). The fourth follow-up requires a hospital attendance at 24 weeks, with a face-to-face interview and assessment by a physiotherapist/assessor. At this visit, the primary outcome (HRET) will be collected. The final follow-up (24 months) is completed by post or telephone.

The two embedded sub studies are:

1. Sub study 1: Blood component (all participants, all sites) and PRP component analyses (PRP intervention arm only). A blood sample will be taken from each participant after consent and randomisation but prior to treatment. The samples will be analysed to compare its composition by blood cell type. PRP samples will be prepared according to treatment allocation and a portion will remain after treatment. This will be sent to a central laboratory for later analysis (blood cells count, growth factors and platelets viability).
2. Sub study 2: Immunohistochemistry analysis (16 participants from selected sites only who have given consent to undergo the sample collection procedure). A needle biopsy of the healing Achilles tendon under ultrasound guidance will be taking during an outpatient visit. Samples will undergo immunohistochemistry analysis centrally in a specialist laboratory.