We consider the Schatten spaces in the framework of operator space theory and for any , we characterize the completely -complemented subspaces of . They turn out to be the direct sums of spaces of the form , where are Hilbert spaces. This result is related to some previous work of Arazy and Friedman giving a description of all -complemented subspaces of in terms of the Cartan factors of types 1-4. We use operator space structures on these Cartan factors regarded as subspaces of appropriate noncommutative -spaces. Also we show that for any , there is a triple isomorphism on some Cartan factor of type 4 and of dimension which is not completely isometric, and we investigate -versions of such isomorphisms.