Table 1 Study objectives and endpoints

Primary:

• Evaluate the clinical efficacy of platelet-rich plasma (PRP) in acute Achilles tendon rupture (ATR) recovery in terms of muscle-tendon function

At 24 weeks post treatment:

• Limb Symmetry Index of work capacity during heel-rise endurance test (HRET); maximum heel-rise height and repetitions during HRET will be reported as secondary outcomes

Secondary:

• Evaluate the clinical efficacy of PRP in acute ATR in terms of participant-reported functional recovery, pain and quality of life

During the first 2 weeks post treatment:

• Visual analogue scale pain daily diary [15]

At 4, 7, 13 and 24 weeks post treatment:

• Achilles Tendon Rupture Score [16]

• Patient-Specific Functional Scale [17, 18]

• SF-12 (acute) [19]

Exploratory (sub-studies):

• Determine the key components of PRP that contribute to its mechanism of action

• Further understand, in an immunohistochemical sub-study, the mechanisms of PRP that may account for its clinical efficacy

• Identify the histological pathways that PRP may alter to exert its effects; using these results and those from the PRP biological component sub-study, inform future targeted manipulation of PRP properties to maximise its efficacy in tendon healing

At baseline (sub-study 1)

• Blood sample for PRP component analysis (cell count, relevant tendon active growth factors, concentrations and platelet activation); all PRP group participants

• Whole blood analysis for cell count and concentrations; all participants.

At 6 weeks post treatment (sub-study 2):

• A needle biopsy of the healing Achilles tendon under ultrasound guidance during an outpatient visit for immunohistochemistry analysis (n = 16)