One of the Boston Marathon’s defending champions has pulled out of this year’s race because of an injury, according to the Boston Athletic Association. American Susannah Scaroni, the defending women’s wheelchair champion, has withdrawn from the Professional Women’s Wheelchair Field because of a shoulder injury, the B.A.A. said. Scaroni's race in 2023 was memorable. She was forced to pull over to the side of a Natick street and tighten an axle in the middle of the race.Despite the delay, Scaroni went on to win her first Boston Marathon with a final time of 01:41:45.Men’s wheelchair division champion Marcel Hug, who set a course record of 1:17:06 in 2023, will return to defend his title in Boston.Runner Hellen Obiri, who almost didn't race in 2023, won the women's division of the race with a time of 2:21:38.Evans Chebet, the first runner to win consecutive Boston Marathons in more than a decade, is returning to defend his men’s title. Race director: How hard is it to repeat in Boston Marathon?