The Rossoneri announced the signing of the 26-year-old on their official website just before the close of the transfer window on August 31 only to issue a statement hours later disclosing that the transfer had been called off.
It was reported at the time that the deal had collapsed because of Milan defender Cristian Zaccardo's inability to agree personal terms with Parma over a proposed move in the other direction.
However, Leonardi has now disclosed that Milan's medical team discovered that Biabiany had cardiac dysrhythmia and that the Frenchman is now facing an indefinite spell on the sidelines.
"I speak on behalf of the club, the player and his representatives," the Parma director told the club's official website.
"Biabiany went for a medical exam on July in Parma and was declared fit. Subsequently, though, on September 1, during his medical carried out in Milan, there was the appearance of an irregular heartbeat that had never been previously detected.
"After returning to Parma, he was subjected to further tests and, based on these, it was felt that the best thing to do at this time would be to take a break from competitive activity for a limited period of time, during which the player will be monitored and subjected to further investigation to establish the eventual return to action."
Leonardi also expressed his hope that Biabiany will not have to continue his career with a question mark over his health or fitness.
"Jonathan could play as he is fit," he declared. "We could put him on the field. But until we have certainty [over the severity of the problem], he will not be used.
"It's terrible to put a label on the boy. I strongly hope that it's just a minor problem."
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