Calzaghe was made to work very hard by his awkward opponent

But the 34-year-old Welshman was given a thorough working over by the unheralded Cameroonian fighter in a scrappy and brutal encounter.

Calzaghe has now made 19 successful defences - six short of heavyweight legend Joe Louis' all-time record.

But Calzaghe, undefeated in 42 bouts, will not forget Bika in a hurry after a hard night in Manchester.

Interview: Boxing promoter Frank Warren

The Welsh star impressed the judges enough to claim a 117-110 (twice), 116-111 verdict but he had to cope with a badly-cut left eye from the fourth round onwards after a head-butt.

Bika's raw but muscular approach paid plenty of dividends as he continually knocked Calzaghe out of his usually elegant stride.

I'm disappointed with the performance but a win is a win Joe Calzaghe

So dominant against the previously unbeaten Jeff Lacy seven months ago, Calzaghe was made to look a little ragged at times by the aggressive Bika, who was docked a point in the fifth for using his head illegally.

Calzaghe was frequently pushed back by his opponent's powerful right, had blood pouring down his face from his cut eye and was winded by a low blow in a wild final round.

But by then he had seen plenty of that kind of thing from the 27-year-old Bika, who had given WBC champion Markus Beyer plenty of problems before another butt forced a technical draw in their bout in Germany in May.

That performance alone suggested Bika - who arrived with a record of 20 wins and one defeat from his 23 fights - would give Calzaghe plenty to think about.

The Welshman's superb win over Lacy has attracted American acclaim and the bout was beamed back to the United States.

"I went into the fight with no real sparring so it was a bit of a gamble," said a relieved Calzaghe afterwards.

"I'm disappointed with the performance but a win is a win. I wanted to put on a spectacle. I was too keen to impress and was looking for an early knockout."

Calzaghe's promoter, Frank Warren, said: "I am upset with him, especially when he was showboating and dropping his hands - I don't like that.

"Joe is a tremendous boxer but he was hampered by that cut. One thing you can't doubt with Joe Calzaghe is he has a fighter's heart."

Warren is planning to line up a major fight for Calzaghe next spring, with WBA and WBC champion Dane Mikkel Kessler a possible opponent.