Australia - Former MotoGP champion Jorge Lorenzo was rushed to a Melbourne hospital for emergency plastic surgery after one of his fingers was severely injured in a crash during morning practice.The sickening injury to the Spaniard's finger on his left hand forced him to miss the race and ultimately concede the championship to Australian Casey Stoner, who won his fifth straight home Grand Prix at Phillip Island.Lorenzo crashed at the exit of turn 12 on his final lap of the 20-minute session, high-siding off the bike and coming to rest on the edge of the circuit.He walked away from the site shaking his hand and was ruled unfit to start the race by the circuit's medical centre."When I saw Jorge's crash I thought it was just a small crash," Stoner told reporters after his victory."I thought it might be just a small graze or something like that."Then I saw the replay and saw what actually happened and everyone was out there looking for the end of his finger."And it sort of made me feel a little bit sick because I'm a racer, I know what it's like to go through these things and you can't really wish them upon anyone."GRIM DAY FOR YAMAHAA team spokesman said later that Lorenzo had not lost part of his finger in the crash, but that the top of his finger was badly injured and the full extent of the injury would not be disclosed until after the surgery on Sunday night."He is currently undergoing surgery ... We will release a statement once we have a full medical report," he said.The injury put paid to Lorenzo's slim hopes of staying in the championship hunt as Stoner took an unassailable lead over the Spaniard with two races left in the championship.It was a grim day all round for Yamaha who were also forced to scratch Ben Spies, while British rider Cal Crutchlow also retired after slipping in the wet late in the race.The American Spies had qualified seventh despite receiving a knock to the head during a high-speed crash in the session, but was also ruled unfit to race.