‘Radio City Christmas Spectacular’ starring the Rockettes

To parphrase ZZ Top, the Rockettes have legs…and they know how to use them. So it’s not surprising that the 18 leggy dancers were the stars of the “Radio City Christmas Spectacular,” which opened Friday night at the Rosemont Theatre. Displaying no first-night jitters, the Rockettes lived up to showman Russell Markert’s dream of forming a chorus line that moved and behaved as one dancer.