Review Question - QID 210090

A 12-year-old female presents to the emergency room after she fell and sustained the injury seen in Figures A and B. On examination, her skin is closed and she is neurovascularly intact. The on-call orthopedic surgeon is unavailable for the next 8 hours due to multiple emergent operative cases. The emergency room performs a closed reduction followed by application of a long arm splint at 90 degrees. Post reduction films are seen in Figure C and D. She is treated nonoperatively with her splint removed at 4 weeks in the orthopedic department. At four months the patient is noted to have loss of elbow extension. Which of the following explains her loss of motion?