Modular porous tantalum acetabular cup: clinical and radiological experience

Introduction Acetabular aseptic loosening is the main cause of failure in prosthetic hip surgery and the first cause of revision. Uncemented hemispherical cups are widely used and different biomaterials have been developed to obtain primary and secondary stability through osteointegration. Porous tantalum’s structure is similar to cancellous bone and presents with mechanical and biological characteristics aimed to enable rapid and complete osteointegration and improve the survival of the prosthesis. Materials and methods From May 2004 to June 2007 one hundred TMT modular acetabular components were implanted in 97 patients for primary THA. For this study we assessed 89 prostheses in 86 patients with 56 months (42–77 months) follow-up, both clinically and radiographically. Results At the last follow-up no implant appeared mobilized. Harris Hip Score changed from 52.75 points preoperatively to 95.72 postoperatively (p\0.0001). Oxford Hip Score improved from 37.16 to 14.78 points (p\0.0001). Gaps at the bone-prosthesis interface were documented at the immediate postoperative X-rays in 51 implants (57%), mostly in zone II. At the last radiographic assessment they appeared completely filled in 87% of the cases (mean time to fill 1 year), partially filled in 10%, leaving less than 1 mm gap, while in 2 cases they remain unchanged. Osteointegration signs according to Moore and McAuley were also considered: at least three signs were present in all cases indicating complete osteointegration of the implants. There was no evidence of radiolucent lines at last follow-up. One dislocation occurred in one case at 21 months and it was reduced in narcosis with no recurrence. Discussion Medium-term results of this cup are comparable with those reported in literature for porous tantalum monoblock components. The presence of the titanium layer in the metal-back of the modular component, that theoretically could affect the biomechanical characteristics of the cup, does not seem to affect host bone biological response when compared to the monoblock socket. Thanks to its mechanical characteristics and excellent osteoconduction, this biomaterial provides a good primary stability and excellent osteointegration of the component. Conclusions The results reported suggest that this cup represents at a medium-term follow-up a good implant for acetabular arthroplasty.