Born in Clermont-Ferrand, Puy-de-Dôme, Pladner won a gold medal at the 1925 European Amateur Boxing Championships, and made his professional debut in January 1926 with a win over Rene Boriello.

He suffered the first defeat of his career in December 1927 when he lost a points decision to Johnny Hill at the National Sporting Club in London.

In 1932 Pladner travelled to Canada for a series of fights, including a tournament to find a challenger for world champion Panama Al Brown.

Pladner won five of these fights, the last a win over Newsboy Brown, with one drawn, and in September 1932 faced the world champion at Maple Leaf Gardens in Toronto.

Over the next two years, Pladner lost only two fights (to Perez and Kid Francis), a period that included successful defences of his French bantamweight title against Joseph Decico, Frank Harsen, and Huat.