CORR Insights^®: Tantalum Components in Difficult Acetabular Revisions Have Good Survival at 5 to 10 Years: Longer Term Followup of a Previous Report

Where Are We Now?

Acetabular revision probably is the most challenging aspect of THA. While the majority of acetabular revisions can be performed using a conventional uncemented hemispherical cup with or without additional dome-screw fixation, patients with severe acetabular deficiencies and poor bone quality require more-complex implants to achieve sufficient primary stability and allow for osteointegration [12].

Tantalum cups can be very handy for these more-complex revisions. The increased porosity, the high coefficient of friction, and the low elastic modulus of porous tantalum compared with traditional titanium or cobalt chromium acetabular components allow for greater primary implant stability, bone ingrowth potential, and host bone preservation [6]. The use of trabecular metal cups in acetabular revision has yielded excellent mid-term clinical and radiological results [7].

The authors of the current study found durable fixation of tantalum cups in THA revisions with severe acetabular bone deficiency, showing a 92% survival free from aseptic loosening at 10 years. An important finding of this study was the high rate of dislocations, with 10% of hips requiring reoperation for joint instability.

Where Do We Need To Go?

There is great potential for further improvement of our surgical techniques and implant technology in the management of difficult acetabular revisions. Custom porous-coated triflange cages, cup-cage constructs, and acetabular distraction technique [1] are considered reasonable alternatives to tantalum acetabular cups (with or without augments) and are currently under clinical investigation.

Nevertheless, the current study causes me to believe the real opportunity before us would be to focus on the high morbidity associated with this challenging surgery. Dislocation and infection are the two most-common complications after revision THA [8, 14]. Dual-mobility constructs are increasingly used to maximize the joint stability in non-constrained revision THAs. A recent award-winning paper [4] showed a substantially lower risk of dislocation and subsequent revision for dislocation when dual-mobility constructs were compared to large-diameter bearings. Also, the Swedish Hip Arthroplasty Register reported a reduction of risk of dislocation following revision THA when dual-mobility components were used [11]. The early observations of dual-mobility constructs used for hips with high-risk of dislocation are encouraging, but long-term results are still needed [13].

The fight against periprosthetic joint infection continues, with emerging technologies targeting biofilm formation, and methods to prevent adhesion and proliferation of micro-organisms to the metallic surfaces like megaprostheses with silver ion-doped ceramic nanopowder coating of titanium implants [2, 3, 10], and iodine coatings for titanium hip implants [5, 9]. Thus far, preliminary studies report no toxicity associated with the silver-or iodine-coated implants, as well as favorable antibacterial activity and biocompatibility with the iodine coatings.

Even with these advancements, a number of questions remain. Will we be able to reduce the risk of dislocation and minimize the incidence of periprosthetic joint infection in difficult acetabular revisions with poor bone stock using these emerging technologies without jeopardizing primary implant stability and osteointegration? Will a dual-mobility construct coated with silver or iodine yield superior clinical and radiological outcomes than tantalum cups with conventional bearings?

How Do We Get There?

Of course, randomized, multicenter trials would be ideal for enrolling a sufficient number of patients presenting with severe acetabular bone stock deficiencies. But more realistically, high-volume institutions could carry out prospective comparative series of revision THAs using different techniques, but the same methodology for patient selection and bone stock assessment. This option seems more feasible, given the variety of surgical methods and implants that call for clinical validation.