Acetabular reconstruction using porous metallic material in complex revision total hip arthroplasty: A systematic review.

Bone defects during acetabular revision of total hip arthroplasty raise a problem of primary fixation and of durable reconstruction. Bone graft with direct cemented fixation or in a reinforcement cage was long considered to be the gold standard; however, failures were reported after 10 years' follow-up, especially in segmental defect of the roof or pelvic discontinuity. In such cases, metallic materials were proposed, to ensure primary fixation by a roughness effect with added screws, and especially to avoid failure due to bone resorption in the medium term. We report a systematic literature analysis, addressing the following questions: (1) What materials are available and can be used with dual mobility (DM) designs? Apart from Trabecular Metal™ (TM), in which a DM cup can be cemented for sizes≥56mm, 4 other porous metals are available (Tritanium™, Trabecular Titanium™, Conceloc™, Regenerex™ and Gription™) although only the first 3 can be associated to DM. (2) Can the cost of these materials be estimated and compared to allograft with reinforcement cage? Considering simply the cost of the implant itself, compared to reconstruction by graft+cage+cemented cup (€2100), TM incurs an extra cost of €534, but with €1434 not covered by the French healthcare insurance. The cost of custom implants (apart from hemi-pelvis) ranges between €4200 and €8500, with only €4749 cover. (3) Do metallic materials ensure better survival than allograft+cage, according to severity of bone loss? Metallic reconstruction is claimed (with a low level of evidence) to reduce the risk of iterative loosening, but with a higher rate of dislocation, probably due to the lack of DM in many series. (4) What are the advantages and drawbacks of modular and custom metallic reconstructions? Modular reconstructions do not require 3D preoperative planning, but incur the risks of complications inherent to modularity. Custom implants can deal with more extensive defects, but require 5 to 8 weeks' production and are difficult to implant for the larger ones and/or when revision is limited to the acetabulum. (5) In what indications are these materials irreplaceable? Prior failure of allograft+cage in Paprosky type III defect with or without pelvic discontinuity shows the greatest benefit from metallic reconstruction, conditional on certain technical tricks. Only reconstructions using TM have more than 10 years' follow-up; other materials will need close monitoring. Failures in allograft with reinforcement cages occurred after about 10 years, and TM will need longer follow-up to prove its effectiveness. The high risk of dislocation should enable DM to be used, especially for small-diameter metallic reconstructions.