Primary Total Hip Arthroplasty

THA comprises the replacement of the damaged bone and cartilage with prosthetic components. The proximal end of the femur is replaced with a stem and ball/head, while the acetabulum is most commonly replaced with a unipolar cup (UP) that consists of a liner inside of a metal shell. UP cups are associated with risks of dislocations, especially in elderly and female patients, as well as in patients with lumbar stiffness or operated for femoral neck fractures. In fact, one of the most common reasons for early revision of UP cups are dislocations. Dual-mobility (DM) cups were introduced in the 1970s by the French surgeon Gilles Bousquet, as an alternative to UP cups. They are made up of two articulations, a femoral head moving inside a mobile polyethylene liner, which in turn moves inside a metal shell. This design allows for a greater jump distance and range of motion (ROM) compared to UP cups, thus resulting in reduced rates of dislocation. A recent systematic review that evaluated 5 case-control studies (549 DM cups vs 649 UP cups) and 3 registry studies (5935 DM cups vs 217362 UP) found that in case-control studies, the dislocation rates were 0.2% for DM cups versus 7.1% for UP cups (p=0.009). Furthermore, in registry studies the revision rates due to dislocation were 0.2% for DM cups versus 0.5% for UP cups (p=0.050). Nonetheless, there have been some concerns associated with the use of DM cups, including intra-prosthetic dislocations (IPD), polyethylene wear, and iliopsoas impingement. Since the early 2000s, new improvements in the design of DM cups have nearly eliminated the risk of IPD, and the use of ultra-high molecular weight polyethylene (UHMWPE) has greatly reduced wear rates, even in young and active patients. Lastly, although some studies have reported iliopsoas impingement with DM cups, the impingement is usually against the optional fixations, and not against the mobile polyethylene insert. The hypothesis of the present interventional randomised controlled trial (RCT) is that THA using DM cups will not provide inferior outcomes compared to THA using UP cups, in terms of hip awareness measured using the forgotten joint score (FJS).

This is a prospective randomized control trial comparing two collared and collarless femoral implants used in primary total hip arthroplasty. The specific aims of this trial are to: SA1: Prospectively assess clinical outcomes in patients undergoing primary total hip arthroplasty with a collared versus collarless femoral stem of the same design. SA2: Evaluate serial radiographs to quantify differences in subsidence between collared and collarless implant groups. SA3: Report and compare incidence rates of intraoperative and postoperative periprosthetic fractures and aseptic loosening following primary total hip arthroplasty with use of either a collared or collarless stem. Hypothesis: The addition of a collar to the same designed triple-taper primary hip stem will lead to a reduction in subsidence and incidence of perioperative and periprosthetic femur fractures.