Dr Iain Duncan

Iain Duncan October 2015

PRP (platelet-rich plasma) therapies have been used for over a decade for a whole number of clinical problems (see PRP wikipedia entry). PRP is blood plasma that has been enriched with platelets and contains (and releases through degranulation) several different growth factors and other cytokines that stimulate healing of bone and soft tissue. It is a great concept but how should it be used? The research on PRP has suffered a common problem seen in clinical medicine. Researchers and clinicians have a new treatment/test/technology and hope to find a use but don’t know how to choose the right group of patients/problems/complaints/ or phenomena to test it with or which varSyringeiables to manage/control. It is surprising that we make much headway as the constraints and variables are numerous.

In musculoskeletal medicine it has been used for many purposes  but I will focus on its use in tendon injuries.

In the case of PRP therapy and tendon conditions there is little homogeneity between the studies. The evidence for PRP (platelet-rich plasma)  therapy in tendinopathies is mixed and is summarized in the paper by Kaux et al in the JSRM[i].  Overall the literature on PRP therapy is generally neutral or positive but the variables and study designs make it difficult to either refute or confidently endorse the use of PRP for a given clinical scenario.

If you look only at studies which were of level 1 evidence , had a followup period of at least  6 months and used ultrasound guidance (3 lateral epicondylitis studies, 2 rotator cuff  (not including the study below), 3 patellar tendon)  then there is substantial evidence that a subgroup of patients do very well with PRP.

In particular I have been impressed by the, as yet unpublished, study of Dr. Francesco Arrigoni at the University of L’Aquila, Italy, that was presented at RSNA Chicago in 2014, and later featured by auntminnie.com online. In a retrospective study of 240 patients they found that ultrasound-guided PRP injection of the supraspinatus tendon significantly outperformed the use of medical and physical therapy alone.

Arrigoni and colleagues evaluated the effectiveness of ultrasound-guided PRP injection (2 injections 21 days apart) of the supraspinatus tendon by comparing it with medical and physical therapy alone. Patients were included in the study if they had a diagnosis of tendinosis or small focal tear of the supraspinatus tendon (< 1 cm). They followed up all patients with MRI up to four years.

After 4 years the results are summarized in table 1:

  MRI Better MRI same MRI worse Pain better Function better
PRP Rx 32% 48% 20% 75% 56%
Physical Rx 3% 34% 63% 16% 9%

He acknowledged a number of limitations to the study. Patients were not divided by age, and the medical and physical therapy was not standardized. It should also be noted that they did not quantify the degree change of the tendinopathy on MRI and the medical therapy was not standardized.

Who are these PRP responders? It is not clear from the published studies as a whole, as patient selection is highly variable and based on clinical features that almost certainly represent a variety of different pathologies. What is lateral epicondylitis or plantar fasciitis? The clinical syndromes are associated with a variety of imaging findings. The mechanisms of pain in any tendinopathy may be multiple it it seems likely that PRP is an appropriate treatment where the mechanism of pain is linked to a failure of healing associated with a tendon or (plantar) fascia tear*. Therefore if I can demonstrate this failure using ultrasound then it makes sense that this group of patients are potential responders. The first of my selection criteria involve persistent pain linked to an unhealed tear demonstrable on scanning (how one knows a tear is unhealed is the subject for another day and uses technology not yet available on standard ultrasound machines).From the literature and my own observations I have made the following conclusions to assist me in my own practice and so as to use PRP in a consistent and reproducible way (and hopefully deliver maximum benefit).

My criteria for selecting patients that may benefit from injection with PRP are as follows:

The patients should meet these clinical and scan criteria:

  1. Small unhealed partial thickness or split tears of the tendon confirmed with ultrasound or MRI and supported by ultrasound elastography where possible
  2. Symptomatic for > 6months
  3. Functional limitation

The PRP injection:

  1. Must have a platelet concentration 3-4 x blood
  2. Have small numbers of white cells
  3. Have no red cells
  4. Must not be directly mixed with local anaesthetic or corticosteroids
  5. Will be directed into the abnormal tendon with smallest gauge needle possible

The patients having PRP:

  1. Should avoid anti-inflammatories and aspirin from one week prior until three weeks after the injection
  2. Should rest the tendon for several days followed by an isometric strengthening program for the affected part

Ideally all patients treated should be followed up both with ultrasound and clinically as the evidence suggests the benefits are not immediate. The clinical trails often showed the biggest differences at 6-12 months and beyond post injection.

[i] Kaux JF, Drion P, Croisier JL, Crielaard: Tendinopathies and platelet-rich plasma (PRP): from pre-clinical experiments to therapeutic use. JSRM 2015; 11: 7-17.

* For a complete review of treatment review of plantar fascia injection therapy evidence see here. Though not stated in the abstract  the article states “PRP had the highest probability of being the best treatment [for plantar fasciitis] in the medium term.”


Iain Duncan Update September 2017

I have reviewed the data on 50 cases of PRP therapy (from 2015-2016) that fulfilled the above criteria. Thanks to those who responded to my emails. The data is shown below in graphical format. The responses are based on 4-6 month follow-up data. 55% had at least a moderate improvement with 27% an excellent response -remembering that virtually all these patients had failed all other therapies. Unfortunately 24% did not respond significantly. Most of these patients had plantar fascia, elbow tendon, or achilles tendon tears.


PRP Response rate 2016_50 cases

PRP Response rate 2016: 50 cases 6mth follow-up