That feature (Defringe sliders) was introduced in ACR 7.1 for Photoshop CS6 (and Lightroom 4.1). It isn't available in any ACR version under Photoshop CS5.
Chromatic aberration has always been a single checkbox.
(Actually "defringe" corrects axial chromatic aberration, while "chromatic aberration" takes care of the lateral variety).