Dave Grohl is clearly very happy with the surgeon who mended his broken leg after a stage fall last month — and saved the Foo Fighters' North American tour in the process.

As a show of thanks for Grohl's doctor, the Baltimore-based Lew C. Schon of MedStar Union Memorial Hospital Orthopaedics and Sports Medicine, the Foos brought him onstage during their Boston tour stop on July 19 — and not just to take a bow. As you can see in the fan-shot footage above, Schon came out for the band's cover of the White Stripes' "Seven Nation Army," stepping up to the mic to contribute some surprisingly solid lead vocals (and show off a few moves while he was at it).

As previously reported, Grohl returned to active duty with the help of a custom-made throne that allows him to rock and recline without, as he put it, "[sitting] on a stool like Paul Simon." What these tour dates lack in frontman mobility, he insists they've gained in added energy.

"What seemed like a setback at the time has turned into this beautiful blessing in disguise, where this throne and these crutches and these audiences make us play longer and harder than we ever have," Grohl explained last week. "It’s this whole new energy in the show."

He'll be further along in the recovery process once the Foo Fighters resume their tour next month — now that the band has completed its two-night stand in Boston, they're off the road for a few weeks before they pick things up again on Aug. 12 in Edmonton, Canada.

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