Randomized trials of complex , non-pharmacologic interventions implemented in home and community settings , such as the University of Southern California ( USC ) - Rancho Los Amigos National Rehabilitation Center ( RLANRC ) Pressure Ulcer Prevention Study ( PUPS ) , present unique challenges with respect to ( @ ) participant recruitment and retention , ( @ ) intervention delivery and fidelity , ( @ ) randomization and assessment , and ( @ ) potential inadvertent treatment effects .