"Twenty-four hours after the operation the patient's clinical condition is unchanged while his neurological development is stable and remains serious", said the Santa Maria alle Scotte in Siena in a statement.
On Monday, the Siena University Hospital issued a bulletin in which it confirmed that Zanardi had undergone a second surgery following the results of a CT scan.
He remains in a medically induced coma.
The 53-year-old Zanardi, who lost both of his legs in an auto racing crash almost 20 years ago, has been on a ventilator since he crashed his handbike into an oncoming truck near the Tuscan town of Pienza on June 19 during a relay event.
The hospital reported that Zanardi's condition "remained stable from the cardio-respiratory and metabolic point of view, serious from the neurological point of view".
Roberto Gusinu, the hospital medical director, said, "The operation that was done represents a step that was foreseen by the medical team". "Our professionals will evaluate the situation day by day".
In accordance with Zanardi's family, the next health bulletin will be issued in about 24 hours.
On Tuesday, it was announced that the Ferrari F1 racing team would carry the message "Forza Alex" on their cars during the Austrian Grand Prix this weekend.
Zanardi, who lost his legs in an Indy vehicle crash while racing in Germany in 2001, crashed his handbike into an oncoming truck on June 19 during an event in of Pienza, Italy.
The latest surgery took place ten days after Zanardi, who won two golds at both London 2012 and Rio 2016 in para-cycling, crashed on a descent while competing in a national handcycling road race.