Large studies have reported high dislocation rates (7 to 24%) following revision total hip arthroplasty (THA), particularly when the revision is undertaken in the presence of pre-existing instability. We retrospectively reviewed the clinical and radiographic outcome of 155 consecutive revision THA's that had been performed using an unconstrained dual-mobility acetabular implant. It features a mobile polyethylene liner articulating with both the prosthesis head and a metal acetabular cup, such that the liner acts as the femoral head in extreme positions. It can be implanted in either a press fit or cemented manner. Mean follow-up was 40 months (18–66) and average age 77 (42–89). Uncemented (n=122) and cemented (n=33) implants with a reinforcing cage, were used. Indications were aseptic loosening (n=113), recurrent instability (n=29), periprosthetic fracture (n=11) and sepsis (n=2). Three of the 155 cases (1.9%) dislocated within 6 weeks of surgery and were successfully managed with closed reduction. The 3 dislocations occurred in the groups revised for recurrent dislocation and periprosthetic fracture. There were no cases of recurrent dislocation and no revisions for implant failure. Despite a pantheon of options available, post-operative dislocation remains a challenge especially in patients with risk factors for instability. The use of large diameter heads is proven to improve stability but there are concerns regarding wear rates, metal toxicity and recurrent dislocation in the presence of abductor dysfunction. With constrained liners there are concerns regarding device failure and aseptic loosening due to implant overload. Our dislocation rates of 1.9% and survivorship to date compare favourably with alternative techniques and are also in line with studies from France using implants of a similar design. In our hands, where there are risk factors for dislocation, the use of a dual-mobility implant has been very effective at both restoring and maintaining stability in patients undergoing revision THA.

Introduction: Tantalum Monoblock Acetabular cup was designed to reduce backside wear and stimulate osseo-integration of cup with bone. The cup has peripheral fit to improve the initial stability and further stability and longevity depends on the osseointegration of cup with acetabulum. The revision cup was intended to give added stability with screws in case of defective rim or large acetabulum. The aim of this study is to assess the radiological outcome following tantalum monoblock revision cup in total hip replacement.

Methods: Between 1999 and 2000, 32 Tantalum mono-block revision acetabular cups was used in 31 patients. Standard hip radiographs were performed during post op, at three months, six months and then annually. X rays were assessed for loosening in De Lee and Charnley zones and for migration of cup.

Results: At a minimum follow-up of 2 years (range 2 to 5 years), 31 hips in 30 patients were assessed. The average age of the patient was 62.4 years (39–78 years). Three Brookers type 1 and one type 2 heterotrophic ossification was seen. There was a gap of 2–5mm in Zone 1(6 patients), 1–5mm in Zone 2 (8 Patients) and 5mm in Zone 3 of one patient. At final follow up, all the gaps were filled, except for one, where 5mm gap was persistent. There was no migration of cup or problems with screws. All the patients were satisfied with the operation.

Conclusion: Short term radiological result following uncemented revision tantalum monoblock acetabular cup in total hip replacement is highly encouraging. However, similar results from other centres and long term follow up studies are necessary to confirm the efficacy of the revision cups.