Wait, how does that work?

https://metro.co.uk/2020/02/10/boy-4-hand-reattached-sliced-off-lawn-mower-12215998/

Shaurya Undre’s left hand was completely severed while playing with his father Mukesh’s lawn mower in India. The little lad was rushed to hospital where surgeons painstakingly reattached it at the wrist – matching up the veins and arteries – during a six-hour operation. He’s now out of hospital and expected to make a full recovery.

Specialist micro-vascular surgeon Dr Abhishek Ghosh used skin and vein grafts from Shaurya’s leg to reattach the hand.

Dr Ghosh said: ‘The child had suffered an avulsion amputation of his left hand when it got accidentally stuck in a grass cutting machine. ‘His left hand was completely avulsed with part of the bones attached to the body while the hand skin and muscle got detached.’ He added that it was ‘very difficult’ to rejoin the hand, including muscle, blood vessels and soft tissue, but continued: ‘Seeing the young age of the child it was decided to attempt to salvage the hand.

‘The patient was taken up for surgery immediately and given anaesthesia.’

Dr Ghosh explained: ‘(A) tiny blood vessel was then joined to the main artery of the forearm with the help of a long vein graft taken from the leg. ‘The circulation of the hand started and the veins were then painstakingly joined under the microscope.’

Shaurya stayed in hospital for a week to recover and will be given physiotherapy to help him learn how to use his hand again.