Study protocol: Effectiveness of dual-mobility cups compared with uni-polar cups for preventing dislocation after primary total hip arthroplasty in elderly patients - design of a randomized controlled trial nested in the Dutch Arthroplasty Registry. - Van Beers LWAH; Van Der Wal BCH; Van Loon TG; Moojen DJF; Van Wier MF; Klaassen AD; Willigenburg NW; Poolman RW (Acta orthopaedica, 2020)