LYNN – A 58-year-old wheelchair bound Lynn woman suffered a broken bone Tuesday after she and the wheelchair somehow fell onto the commuter rail tracks near the Broad Street parking garage, firefighters said.According to Fire Lt. Joe Cariette, the woman was sitting on the wheelchair when it went over the platform and landed in the pit of the tracks around 5:30 p.m. for an unknown reason.Firefighters from the Fayette Street fire station were at the scene for 40 minutes, 20 of which were used to load the woman onto a backboard and stokes basket to extricate her from the tracks, the lieutenant said.”The guys did a good job as usual,” Cariette said. “It’s something out of the ordinary that we don’t do on a daily basis.”He said the unidentified victim was taken to Salem Hospital with a broken ankle and dislocated knee.