Background:Jobe revolutionized the treatment of medial ulnar collateral ligament (MUCL) tears with his reconstruction technique. However, not all MUCL injuries require operative management; Rettig showed that 42% of MUCL injuries respond to conservative management. This was improved by Podesta, who showed that augmentation of nonoperative management with platelet-rich plasma (PRP) and magnetic resonance imaging (MRI) for detecting partial MUCL tears resulted in significantly higher success rates. Their series used a single injection of leukocyte-rich PRP. However, to our knowledge, no study has established optimal dosing and composition of PRP for augmentation of soft tissue healing. We present a series of patients with partial MUCL tears of the elbow treated with a series of 2 leukocyte-rich PRP injections, bracing, physical therapy, and a structured return-to-throwing protocol.Hypothesis:Nonoperative management of acute or subacute partial MUCL tears of the elbow with a formal treatment protocol will allow the injured ligament to heal without surgery and will permit a rapid return to sport.Study Design:Case series; Level of evidence, 4.Methods:Patients with symptomatic MUCL instability and magnetic resonance arthrography demonstrating grade 2 MUCL tears at the proximal or distal aspect were treated with varus-loading elbow bracing, activity restriction, and physical therapy, supplemented by 2 injections of PRP. The injections were separated by 2 weeks. Two weeks after the second injection, a repeat examination and magnetic resonance arthrogram were obtained to evaluate the response to treatment.Results:A total of 25 athletes (23 baseball athletes, 2 softball athletes [1 participant also danced]) underwent PRP injections and guided rehabilitation. Of these patients, 23 were diagnosed with primary grade 2 injuries of the MUCL; 22 patients with primary injuries (96%) demonstrated stability of the MUCL after treatment and returned to play at the same or higher level of competition without further intervention. Repeat MRI demonstrated reconstitution of the ligament in all patients, although 2 patients demonstrated only partial reconstitution. Patients were released to play at 6 weeks; due to vagaries of sports seasons, the mean time to return to competitive play was 82 days. Two of the 25 patients had undergone prior surgery (1 MUCL reconstruction and 1 repair). These patients remained unstable and symptomatic on examination after this treatment regimen, did not show complete reconstitution of the ligament on subsequent MRI, and required MUCL reconstruction.Conclusion:Ouf of 23 primary injury patients who received PRP injections and nonoperative measures, 22 (96%) were able to return to play and demonstrated reconstitution of the MUCL on MRI. Two of the 3 patients for whom PRP therapy failed had undergone previous MUCL surgery. We conclude that a 2-injection regimen of leukocyte-rich PRP is a safe and effective treatment for partial MUCL tears, but it appears to be less effective in patients with previous surgery for MUCL repair or reconstruction.