Scientists planning the world’s first head transplant say they are one step closer to starting human trials.

The neurosurgeons have already performed the controversial operation on a corpse but now, Italian Sergio Canavaro and Xiaoping Ren, from China, claim to have repaired “irreversible” spinal cord injuries in animal experiments.

Two studies, published this week, show monkeys and dogs were able to walk again after their spinal cords were severed and successfully repaired.

The pair said their new findings are “unprecedented” and should pave the way for the first human trials.

Canavaro told USA Today the findings “completely reject the view… that a severed spinal cord cannot be mended in any way, a mantra uncritically repeated over and over.”

Human trials “next step”

Xiaoping said the breakthrough is proof that human trials should be given the go-ahead.

The studies, the findings of which are published in the journal Surgical Neurology International, took place at Harbin Medical University in China.

In 2015, Canavaro announced he wanted to transplant the head of a paralyzed man, Valery Spiridonov, onto the body of a dead donor.

The procedure, he explained, would involve cooling the bodies to a state of deep hypothermia, before severing the spinal columns using a diamond blade.

The next step would be to reattach the blood vessels and nerves, connecting those from Valery’s head to those of the dead donor’s body.

“For too long nature has dictated her rules to us. We’re born, we grow, we age and we die. We have entered an age where we will take our destiny back in our hands. It will change everything,” Canavaro said.

“The first human transplant on human cadavers has been done. Everyone said it was impossible, but the surgery was successful. A full head swap between brain dead organ donors in the next stage.

“And that is the final step for the formal head transplant for a medical condition, which is imminent.”

“Gory, Frankenstein” operation is “criminal”

Canavaro’s plans to perform the first human op on Spiridonov was dealt a blow when the 33-year-old Russian announced last year he was no longer on board.

He dropped out after his wife gave birth to the couple’s “miracle” son.

And Canavaro and Ren’s work has been met with harsh criticism by the scientific and medical community.

Professor Jan Schnupp, from the University of Oxford, said the procedure conjures up “gory, Frankenstein imagery” and described the proposals as “disturbing.”

“The chances that a person who has their head transplanted onto another body will be able to gain any control over it, or benefit from that grafted body are completely negligible,” he said.

“The expected therapeutic value for the patient would be minimal, while the risks of graft rejection-related side effects, or simply death as a consequence of a mishap during the operation, are huge.

“Attempting such a thing given the current state of the art would be nothing short of criminal. As a neuroscientist, I would really like the general public to be reassured that neither I nor any of my colleagues think that beheading people for extremely long-shot experiments is acceptable.”

Dr. James Fildes, of the University of Manchester, said the idea is “morally wrong” if the scientists cannot first prove the procedure improves the life of a large animal.

Professor Catherina Becker, from the University of Edinburgh, said: “Actual success of a head transplant must be measured by long term survival of head and body with the head controlling motor function. This can obviously not be assessed in a corpse and for all we know, would also not occur in a living human.”