Background: Platelet rich plasma [PRP] contains several growth factors which can improve functional outcomes in
tendinopathies, especially tennis elbow. However, there have been no reports on the clinical use of PRP injection in patients who have had previous corticosteroid injections.

Objective: PRP injection can improve elbow function in patients with elbow tendinopathy who have a history of previous corticosteroid injection.

Materials and Methods: Sixteen lateral epicondylitis (tennis elbow) patients who had recurrent symptoms or treatment failure with previous corticosteroid injection therapy were included in the present study. Autologous PRP was injected into the extensor carpi radialis brevis [ECRB] origin of each patient to the ECRB under ultrasound guidance to improve the accuracy of the injection. Follow-up time, Visual Analog Scale [VAS] score, Disabilities of the Arm, Shoulder and Hand [Quick
DASH] score, Mayo elbow score, and patient's satisfaction score were comprehensively collected both before and after PRP injection to evaluate functional outcomes.

Results: Three patients were lost to follow-up; 13 patients were analyzed in this case series. Mean follow-up time was 16.94 months. VAS score, Quick DASH score, and Mayo elbow score were significantly improved after treatment (8.78 versus 1.78, 47.35 versus 5.48, and 65.42 versus 96.25 respectively, p<0.0001). All patients were satisfied with treatment as demonstrated by the patient satisfaction scores. There were no complications from skin allergies after PRP injection.
Interestingly, no patients had undergone surgery as of the last follow-up.

Conclusion: Ultrasound-guided PRP injection can improve functional outcomes in lateral epicondylitis patients who have had prior corticosteroid injections.

Keywords: Platelet rich plasma, Recalcitrant lateral epicondylitis, Recurrent lateral epicondylitis, Corticosteroid, Ultra-sound-guided injection