Michelangelo's statue David may be clean in time for his 500th birthday this year, but experts are concerned that his left ankle may not be strong enough to keep him standing forever. A team of experts at Bologna University has begun analysing tiny cracks in the marble masterpiece's left ankle since restoration work began on the statue last September. "The ankle is weak," said Franca Falletti, director of Florence's Galleria dell'Accademia, where the statue is housed. "It's a problem we need to watch closely." Analysts are able to study the exact size and depth of the cracks now that more than a century of grime and wax deposits have been gently brushed and sucked out of the statue's "skin". David's melancholy pose, with his left leg bent at the knee, makes his left ankle perhaps the only design fault in this figure of male perfection, clearly strained by the 5,572kg of marble above. Most of the cracks are thought to have developed before 1873, when the statue was brought indoors after standing for more than 350 years in Florence's Piazza della Signoria. Although the cracks do not pose an immediate threat, digital analysis will help to determine whether scientists can intervene in future to help strengthen David's weakest points. Meanwhile David's hair, which had been encrusted with black deposits left by pigeons over the centuries, has