BOSTON—Boston Celtics starting center Kendrick Perkins has undergone surgery on his left shoulder. The Celtics said Perkins had arthroscopic surgery Wednesday at New England Baptist Hospital. Also undergoing surgery was the Celtics' second-round draft pick, Bill Walker, to repair damage to his right knee. The NBA champions said both procedures were successful. Team physician Dr. Brian McKeon led both surgeries. No timetable has been set for Perkins' and Walker's off-season returns to the Celtics.