Feasibility and Efficacy of Bone Marrow PRP Injection in Refractory Fissure Tendinopathies of the Lateral Epicondylar Tendons

• Bone Marrow-Derived PRP (Procedure): Participants receive a platelet-rich plasma (PRP) injection prepared from bone marrow aspirate obtained from the posterior iliac crest. After processing, the PRP is injected under ultrasound guidance into the affected lateral elbow tendon.
• Peripheral Blood-Derived PRP (Procedure): Participants receive a platelet-rich plasma (PRP) injection prepared from peripheral venous blood. After processing, the PRP is injected under ultrasound guidance into the affected lateral elbow tendon.

Primary outcomes

• Change in QuickDASH score from baseline to 3 months [Baseline and 3 months after injection]: The primary outcome is the change in the Quick Disabilities of the Arm, Shoulder and Hand (QuickDASH) score between baseline and 3 months. The QuickDASH is a patient-reported questionnaire assessing upper-limb disability and symptoms. Scores range from 0 to 100, with higher scores indicating greater disability.

Secondary outcomes

• Change in QuickDASH score at 6 and 12 months [Baseline, 6 months, and 12 months after injection]: Change in QuickDASH score over time. Scores range from 0 to 100, with higher scores indicating greater disability.
• Change in PRTEE score [Baseline, 3 months, 6 months, and 12 months after injection]: Change in the Patient-Rated Tennis Elbow Evaluation (PRTEE) score. The PRTEE assesses pain and functional limitations related to lateral elbow tendinopathy. Scores range from 0 to 100, with higher scores indicating worse symptoms and disability.
• Change in MEPS score [Baseline, 3 months, 6 months, and 12 months after injection]: Change in the Mayo Elbow Performance Score (MEPS). The MEPS evaluates pain, range of motion, stability, and function of the elbow. Scores range from 0 to 100, with higher scores indicating better elbow function.
• Proportion of patients achieving a clinically meaningful improvement [3 months, 6 months, and 12 months after injection]: Proportion of participants achieving the minimal clinically important difference (MCID), defined as an improvement of at least 16 points in the QuickDASH score (Scores range from 0 to 100, with higher scores indicating greater disability).
• Change in common extensor tendon tear size measured by ultrasound [Baseline, 3 months, 6 months, and 12 months after injection]: Change in the size of the common extensor tendon tear measured by ultrasound in longitudinal and transverse planes. Tear size is recorded in millimeters (mm).
• Rate of surgical treatment during follow-up [Up to 12 months after injection]: Proportion of participants requiring surgical treatment for lateral elbow tendinopathy during the 12-month follow-up period.
• Time to surgery [Up to 12 months after injection]: Time between study inclusion and surgical intervention for lateral elbow tendinopathy.
• Time between study inclusion and surgical intervention for lateral elbow tendinopathy. [From injection to 12 months]
• Participant recruitment rate [Throughout study completion (up to 12 months)]: Number of participants enrolled divided by the number of eligible participants screened during the recruitment period.
• Presence of tendon hypervascularization on ultrasound [Baseline, 3 months, 6 months, and 12 months after injection]: Presence or absence of hypervascularization at the common extensor tendon insertion assessed by Doppler ultrasound.
• Presence of local effusion on ultrasound [Baseline, 3 months, 6 months, and 12 months after injection]: Presence or absence of local effusion at the common extensor tendon insertion assessed by ultrasound.
• Participant retention rate [Up to 12 months after injection]: Proportion of randomized participants who complete the 12-month follow-up.
• Treatment adherence [From intervention to study completion (12 months)]: Proportion of participants who receive the allocated intervention and complete study procedures according to the protocol.
• Completeness of study data collection [Up to 12 months after injection]: Proportion of expected study data collected during follow-up visits.

Sex: All, ages: 18 Years to any

Inclusion Criteria:

* Diagnosis of chronic lateral epicondylitis with partial-thickness tendon tear of the common extensor tendon confirmed by ultrasound.
* Symptoms persisting despite appropriate conservative treatment for at least 3 months.
* Indication for platelet-rich plasma (PRP) injection established by the treating physician.
* Ability to understand the study procedures and comply with follow-up requirements.
* Written informed consent obtained prior to participation.
* Affiliation to a health insurance system (as required by French regulations).

Exclusion Criteria:

* Full-thickness tear of the common extensor tendon.
* Previous surgery of the affected elbow.
* PRP injection in the affected elbow within the previous 6 months.
* Corticosteroid injection in the affected elbow within the previous 3 months.
* Current treatment with medications incompatible with PRP preparation according to study procedures.
* Active infection at the injection site or systemic infection.
* Known hematologic disorder affecting platelet function or coagulation.
* Current anticoagulant therapy that cannot be interrupted according to study requirements.
* Pregnancy or breastfeeding.
* Participation in another interventional clinical trial that could interfere with study outcomes.
* Any medical, psychiatric, or social condition that, in the investigator's opinion, could compromise participant safety or compliance with study procedures.