High rate of fracture in the cementless modular Extrême™ (Mark I) femoral prosthesis in revision total hip arthroplasty: 33 cases at more than 5 years’ follow-up

SummaryIntroductionThe modular concept has been recommended in femoral revision surgery with extensive bone loss, but entails mechanical complications: disassembly and fracture. The present retrospective study assessed the Mark I Extrême™ modular prosthesis at a minimum 5 years’ follow-up.HypothesisA cementless modular femoral stem facilitates revision in case of extensive bone loss, providing satisfactory results without risk of junction failure.Materials and methodsThirty-three prostheses presenting aseptic loosening, including 3 with periprosthetic fracture, in 23 female and 9 male patients, with a mean age of 65 years (range, 49–83 years), were reviewed at a mean 6.3 years’ follow-up (range, 5–9 years). Bone loss was assessed on the SOFCOT (17/33 grade 3 or 4) and Paprosky classifications (19/33 grade III or IV). One patient died; another was lost to follow-up, leaving 31 hips for analysis. Clinical assessment comprised Postel Merle d’Aubigné (PMA) and Harris Hip scores (HHS); radiological assessment used the Engh score and corticomedullary index (CMI).ResultsThere were 15 complications requiring surgery: 9 (27%) unrelated to the implant (1 hematoma, 2 infections, 2 dislocations, 1 femoral non-union, 3 asymptomatic trochanteric non unions) and 6 (18%) implant-related (four 3-level fractures and 2 epiphyseal-metaphyseal disassemblies, requiring 3 total exchanges and 3 proximal component replacements). PMA and HHS scores showed significant improvement, PMA rising from 10.4 (6–18) to 14.4 (11–18) and HHS from 50 (19–88) to 80.9 (52–100). Bone regrowth was “certain” on the Engh classification in 11 cases (44%). There was no diaphyseal component subsidence, even in case of fracture or dissociation. CMI at the 3 junctions between the 4 quarters of the stem showed no significant change: 32.9 and 32.7, 41.2 and 38.7, and 41.6 and 39.9 respectively. Six-year survivorship was 81% (95% CI: 68–94%).DiscussionIn other series for the same type of implant, the rates of fracture (always metaphyseal-diaphyseal) were much lower: 0.8–3.8%. This stem ensures diaphyseal fixation in case of extensive bone loss, but incurs excessive risk of disassembly and fracture.Level of evidenceLevel IV, retrospective study.