This study evaluates the effect of platelet-rich plasma (PRP) use during needling of the extensor carpalis radialis brevis tendon, after failure of proper reeducation including focal extra-corporal shockwave therapy (ESWT). Half of the patients with receive PRP and needling, and half of the patients will receive needling alone.

During the reeducation, the clinical evaluation will be monitored and reported as in a case series.

The conservative management of lateral epicondylitis is known to be a difficult-to-treat annoying condition. The first-line conservative management includes physical therapies with adjuvant painkillers and orthotics, and usually extracorporal shockwave therapy (ESWT). In clinical practice, infiltrative therapies a performed either before or after shockwave therapies. In the author's point of view, they represent a second-line conservative treatment.

The success rate of ESWT for lateral epicondylitis depends mainly of the protocol used. Especially, poor results were observed with too low energy. Both radial and focal ESWT are effective, and focal ESWT has been showed as being as effective as surgical tenotomy.

Concerning infiltrative therapies, it has been well established that corticosteroids are efficient in short-term but deleterious in long-term, likely for degenerative purposes. Prolotherapy, autologous blood, and botulinic toxin injections and others infiltrative therapies are less studied and therefore nowadays not clearly supported by the literature. Stem cells might be an alternative in the future.

Platelet-rich-plasma (PRP) is nowadays widely used, but the results of clinical trials are discordant. Even if the superiority of PRP over corticosteroids is well established, the superiority of PRP on tendon needling or peppering is still controversial. Martin et al. 2019 found in a partially blinded randomized controlled trial (RCT) involving 71 patients no clinical differences at 6 months of follow-up between 2 sessions of peppering with saline + local anesthetic and PRP + local anesthetic. In a similar unblended RCT involving 50 patients, Schöffl et al. 2017 found no clinical differences at 6 months of follow-up. Montalvan et al. 2016 found in a RCT involving 50 patients between 2 infiltrations of PRP and saline no clinical differences at 6 months of follow-up. Rehabilitation was not allowed during the trial and the tendon was not peppered. Mishra et al. found in a blinded RCT involving 119 patients a positive clinical effect of PRP on saline solution, using a single injection with peppering. Behera et al. found similar results in a small RCT on 25 patients.

Some factors has been advocated to influence the outcomes. The most relevant are: direct mechanic action of the needle and fenestration (peppering) technique, number of PRP injections, cells count (platelets, white blood- and red blood cells), activation of the platelets, concomitant local anesthetic use, peri-interventional use of NSAIDs and corticosteroids, concomitant rehabilitation or a contraria immobilization. Whether the positive results observed into the previous selected studies are due to either PRP, peppering, or any of the confounding factors described above remains to debate.

The first aim of this study is to determine the proportion of patients, which would need an infiltrative technique after a proper rehabilitation protocol involving physical therapies, orthotics and ESWT. Our second aim is to establish whether PRP as adjuvant therapy to peppering would increase clinical outcomes.

Details of sample size calculation (58 overall, 29 per group):

58 patients are required to have a 95% chance of detecting, as significant at the 5% level, an increase in the primary outcome measure from 50 in the control group to 60 in the experimental group, considering a standard deviation of 10% and a dropout rate of 10%. After the inclusion of 40 patients, the standard deviation will be re-evaluated and the sample size corrected accordingly if necessary.

Inclusion Criteria:

• Lesion of the ECRB tendon on ultrasonography ([hypoechogenic area during rest OR hypoechogenic area during active contraction, OR compressibility of the tendon OR doppler signal] AND [positive sonopalpation])
• Failure to rehabilitation program including shockwave therapy defined as the need for the patient undergoing additional therapies

Exclusion Criteria:

• Presence on ultrasound of an isolated lesion of the superficial epicondylar tendons as described above, with intact ECRB
• Presence on ultrasound of any of: radiohumeral synovial material; interruption of the lateral collateral ligament; radial nerve entrapment, i.e. under the arcade of Frohse; osteochondral lesion; joint effusion. Note: calcic enthesophytes are not considered as an exclusion criteria
• Clinical presence of cervicobrachialgia, or pain irradiating into the hand
• Corticosteroids: oral intake or infiltration on the last 3 months
• Proximal radius fracture history
• Active inflammatory rheumatic disorders
• Diabetes mellitus
• Immunocompromized status
• Allergy to local anesthetics
• Bleeding disorders or current anticoagulation therapy
• Other clinically significant concomitant disease states (e.g., renal failure, hepatic dysfunction, cardiopulmonary significant insufficiency, etc.)
• Known or suspected non-compliance, drug or alcohol abuse
• Inability to follow the procedures of the study, e.g. due to language problems, psychological disorders, dementia, etc. of the participant
• Participation in another study with investigational drug within the 30 days preceding and during the present study
• Previous enrolment into the current study
• Enrolment of the investigator, his/her family members, employees and other dependent persons

All patients will have blood puncture. Then, the research coordinator will prepare either an opaque syringe of saline solution or of PRP. At the end of the needling procedure, the investigator will inject the content of the opaque syringe.