PARIS — It was as if menswear designers had used a scalpel instead of pencil.

Off with the coat sleeves! Cut away the collar! Snip at pants until they morph into shorts! Split the seams and close them with zippers!

Radical surgery on regular menswear was the message of the Paris summer 2011 season that ended Monday. There was even a hospital vibe about streamlined tunics, shorn of any details, and worn with drop-crotch pants, which are entering the mainstream.

The big fashion picture included the return of high-button, double-breasted jackets; a vogue for silk, whether giving a sheen to cashmere or puckered into seersucker; and flashes of color, bright and muted, like orange, grass green, turquoise and lavender.

The leading fashion surgeon is Raf Simons, who celebrated 15 years in menswear by going back to his roots and making the sleeveless tunic/jacket and wide-legged pants look fresh. His early inspiration from a fellow Belgian designer, Martin Margiela, was absorbed into a show that had less of the precise tailoring that has dominated the designer’s recent collections. Instead, anything from a suit jacket to sportswear was sliced by a bright zipper at the back, covered by a free-flying patterned necktie.