In fairness, Dave Grohl is not letting a broken leg keep him from giving his all at every Foo Fighters gig with a special light up guitar throne helping him to get through the set. But he brought further energy to their recent gig in Fenway Park, Boston when his orthopaedic surgeon, Dr. Lew Schon joined the band on stage to perform lead vocals on The White Stripes song 'Seven Nation Army'. As you do.
After carrying on a gig after breaking his leg during the second song, nothing Grohl does would surprise us so inviting his doctor on stage really isn't all that weird for him and to give credit where it's due, the doc has some set of lungs on him.