Cementless non modular locked stem in THA revisions

Locked femoral stems were developed in the late 80s in parallel with the use of transfemoral approaches for the removal of implants in place. In the case of severe femoral loosening, the realization of a femoral flap reduces the risk of false routes or intraoperative fractures, and in this case the distal locking allows an immediate axial and rotational stabilization of the stem, promoting secondary osseointegration. The femoral flap is also essential in cases of difformity, unextractable cementless stem or in the presence of a long cement plug. In the event of destruction of the femoral isthmus, locking is the only guarantee for distal fixation of the revision stem. Finally, in peri-prosthetic fractures, such as Vancouver B2 and B3, these locked stems combine the advantages of nailing and prosthetic revision. The screws initially used, which were subject to a risk of breakage, were quickly replaced by keys with a larger diameter. These stems are easy to use provided that a reliable ancillary is available, allowing to lock the stem after prosthesis reduction, controlling length and anteversion. Biomechanical studies have insisted on the respect of a safety distance between the distal end of the flap and the first locking hole, on the importance of having a range of stem diameters allowing contact with the cortical bone and on the importance of systematically locking the first hole of the stem. In a retrospective study (1) of 725 cases of revisions with a locked femoral stem, it was shown that the functional results and long-term stem stability were better when using a curved anatomical stem with an extended coating along the entire length. An important prognostic factor was the metaphyseal filling index, favored by a femoroplasty and/or a medial osteoclasia to bring the bone to the prosthesis. In a more recent study (2) with a modern stem, mainly focusing on femoral loosening (60%) and peri-prosthetic fractures (30%), we were able to confirm osseointegration of the implant in 95% of cases, deploring no migration or implant rupture. The survival rate of implants, taking as an end-point the surgical revision of any reason, was 95% at 5 years. The results published in the literature are also favorable with survival rates ranging from 91% at 15 years of follow-up, to 100% at 4 years of folow-up.

1-Patrice Mertl, Remy Philippot, Philippe Rosset, Henri Migaud, Jacques Tabutin, Denis Van de Velde. Distal locking stem for revision femoral loosening and peri-prosthetic fractures. International Orthopaedics, 2011,35, 275-282.
2- Lou Lequeuche, Az-Eddine Djebara, Yassine Bulaid, Massinissa Dehl, Antoine Gabrion, Patrice Mertl. Clinical and radiological results after THA revision with distal locking stem : A cohort study of 44 patients. OTSR 108 (2022) 103267.