Reba Golden hurt her back after falling two floors while building an addition to her house in Honduras. But when she returned to Seattle for a routine spinal surgery, she suffered blood clots, severe bleeding and died in 2007 on the operating table. Joan Bryant’s back had bothered her since a 1990 car accident, so in 2009 she sought help from a Seattle spinal surgeon, but she bled out on the operating table and could not be revived. Like at least three spinal-surgery patients before them, Golden and Bryant died after their doctor injected bone cement into their spine and...