Femoral Stem Dislocation Caused by Trunnionosis Along with Adverse Local Tissue Reaction: A Case Report and a New Technique of Head to Cone Cementing

In total hip replacement (THR), fretting and corrosion at the modular head-neck junction (trunnionosis) may causeadverse local tissue reaction (ALTR). In this report, we presented a ۳۴ years woman with a history of THR eight yearsago, presenting with acute pain and limping. The radiographic assessment revealed stem-head dislocation for whicha revision hip surgery was planned. Surprisingly, we observed pseudotumor and tissue necrosis resulting from thebody’s reaction to cobalt-chromium alloy. The revision surgery entailed pseudotumor debridement and replacing thefemoral head with a new metal head (size ۳۶, long). Due to the separation of the femoral head on a stem, we fixedit on a stem using bone cement. The stem (Omnifit®, Stryker®) was well-fixed and retained to avoid fractures andinfection risk. This technique revealed an acceptable outcome without recurrence of ALTR after a one-year follow-up.Our findings suggest that stem dislocation secondary to trunnionosis might be a long-term complication after THRwith subsequent ALTR.Level of evidence: V