Surgery with THR for arthritis and other hip disorders has long been one of the most successful orthopedic surgical treatments. The majority of the patients gain pain relief and experience improved hip function. In 2017, a total of 10,691 THRs were implanted in Denmark (annual report 2018).~Hip dislocation is a known complication after THR. It is a painful condition which may have far-reaching consequences for the patient, who may experience both physical and mental discomfort. Ultimately, multiple hip dislocations may result in reoperation.~In the literature, the incidence of hip dislocation is reported at 2-6 %, and a more recent review reports a risk of 0.5-10 %.~In Denmark, recurrent hip dislocation is the cause of 21 % of the reoperations per year according to The Danish Hip Arthroplasty Register. According to the British National Joint Registry (NJR) and the Australian register (AOANJRR), hip dislocation is the cause of 15.5 % and 21 %, respectively, of the reoperations.~The best method to avoid reoperation due to instability is to choose the correct implant for the individual patient and thereby spare the patient of having to endure a painful complication and yet another procedure. There are multiple risk factors for instability after THR, and increased use of dual mobility cups (DMC) is already documented.
The general purpose of this study is to examine whether the dual mobility cup (Novae® Serf) reduces the number of hip dislocations after total hip replacement, both early dislocation (≤1 year) and late dislocation (>1 year) after primary THR compared with a conventional cup design (Trabecular MetalTM Modular Acetabular System).