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 cause adverse local tissue reaction (ALTR). In this report, we presented a 34 years woman with a history of THR eight years ago, presenting with acute pain and limping. The radiographic assessment revealed stem-head dislocation for which a revision hip surgery was planned. Surprisingly, we observed pseudotumor and tissue necrosis resulting from the body's reaction to cobalt-chromium alloy. The revision surgery entailed pseudotumor debridement and replacing the femoral head with a new metal head (size 36, long). Due to the separation of the femoral head on a stem, we fixed it on a stem using bone cement. The stem (Omnifit®, Stryker®) was well-fixed and retained to avoid fractures and infection 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 THR with subsequent ALTR.