Treatment of hamstring injury using PRP

In sports and exercise medicine, there is growing attention on interventions that provide endogenous growth factors directly to the injury site. These growth factors are claimed to facilitate healing and speed up the return to play (RTP) after musculoskeletal injury. The most popular ‘biological’ therapy of the past decade is a PRP injection—derived from autologous whole blood using centrifuge separation systems to provide growth factor release from platelets. The growth factors are assumed to stimulate myoblast proliferation and accelerate myofibre regeneration. Prior to my PhD project, the efficacy of PRP had not been studied in a randomised controlled trial (RCT).

The role of MRI in predicting prognosis and guiding RTP decision-making

MRI is more readily available than ever before and is being used increasingly, especially in elite athletes. Despite this, the clinical relevance of MRI for predicting prognosis and for RTP decision-making was unknown.

The Hamstring injection therapy (HIT) study

This study was the first RCT examining the efficacy of PRP injections in athletes with acute hamstring injury. In a three-centre, randomised, double-blind, placebo-controlled trial, we randomly assigned 80 athletes with acute hamstring muscle injuries to PRP (intervention group) or isotonic saline placebo injections (control group). Both groups performed the same standardised criteria-based rehabilitation programme.1 ,2 The primary outcome measure was the time to RTP. Reinjuries were assessed as a secondary outcome measure.

Determining the role of MRI in the RTP decision-making process

We determined the prognostic value of clinical and MRI parameters for the time needed to RTP3 and the reinjury risk4 using a prospective follow-up study with multivariate analysis and blinding of athletes (from the HIT study) and decision-makers to RTP.

We studied MRI findings of hamstring muscles in 108 athletes (from the HIT study and a cohort from Qatar), who had clinically recovered from an acute hamstring injury, and had been cleared to RTP.5 ,6

PRP did not accelerate RTP nor did it improve any RTP outcomes for athletes recovering from acute hamstring injury

At 1 year postinjection we found no benefit of intramuscular PRP compared to placebo injections in patients with acute hamstring injuries in the time to RTP, reinjury rate and alterations of subjective, clinical or MRI measures.1 ,2

MRI provided no additional benefit to guide the RTP decision-making process

Findings at MRI within 5 days of sustaining an hamstring injury were not associated with the time to RTP,3 or with the risk of reinjury.4 Approximately 90% of athletes had intramuscular oedema, and 40% had signs of newly formed fibrosis at the time they were cleared to RTP.5 Having fibrosis at RTP was not associated with a higher risk of reinjury within a year after RTP.6