Ex-Formula 1 driver Alex Zanardi has undergone a third operation lasting five hours on the serious head injuries he sustained last month.

The former F1 and CART racer collided with a vehicle while participating in a handbike race in Italy on June 19 and underwent emergency neurological surgery upon his arrival to the Santa Maria alle Scotte hospital in Siena.

Zanardi was subsequently placed in a medically-induced coma before further neurological surgery took place on June 29.

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The hospital confirmed the 53-year-old Italian spent five hours in surgery “aimed at cranio-facial reconstruction and stabilisation of the areas affected by the trauma”.

"The patient has undergone a new surgery, performed by the professionals of the maxillofacial and neurosurgery, aimed at cranio-facial reconstruction and stabilisation of the areas affected by the trauma,” the latest medical bulletin read.

Professor Paolo Gennaro, director of the hospital’s maxillofacial surgery unit, said “the fractures were complex”.

“This required careful programming that made use of computerised, digital and three-dimensional technologies made to measure for the patient,” he added.

“The complexity of the case was rather singular, even if it is a type of fracture that we routinely face in our centre.”

The four-times Paralympic gold medalist’s condition otherwise remains unchanged.

“His condition remains stable from the cardio-respiratory and metabolic point of view, [and] severe from the neurological point of view,” the bulletin concluded.

The hospital has already confirmed that updates will only be provided when there is a significant update or change to Zanardi's condition. 

Ferrari raced with the message ‘Forza Alex’ on both its cars during Sunday’s Austrian Grand Prix, the opening round of the revised 2020 F1 season.