Review Question - QID 219984

A 21-year-old minor league baseball pitcher presents as a referral from the team's head athletic trainer with progressive pain along the posterior elbow that worsens throughout the throwing motion, particularly with follow-through at the end of a pitch. Advanced imaging shows the findings demarcated in Figure A, and the patient elects to undergo an arthroscopic surgery to treat his pathology. He initially does well after the procedure, but returns after beginning an accelerated return-to-throwing program with new pain along the posteromedial elbow, a negative "arm bar" test, a positive milking maneuver, and the findings in Figures B and C. Which of the following is the most likely reason for his initial treatment failure?