Complex sentence: A week before he was to go pro in 1997, while serving to Andre Agassi during a 1997 practice session in North Carolina he suffered a spiral fracture of the humerus bone in his right arm.
Split into simpler sentences: A week before he was to go pro in 1997, he broke his arm. However, serving to Andre Agassi during a 1997 practice session in North Carolina he suffered a spiral fracture of the humerus bone in his right arm.