Metallosis, Trunnionosis, and Head-stem Dissociation of the Exeter v40 Stem in a Metal-on-Metal Hip: A Unique Case.

Introduction: In this article, we report a unique case of head-stem dissociation in a metal-on-metal total hip replacement which utilized an Exeter stem. Although metallosis and pseudotumor formation are well recognized complications of metal-on-metal hip replacements, head-stem dissociations are rare with few being reported in literature. To the best of our knowledge, this case report is the first to report this occurrence in an Exeter stem.

Case Report: A 76-year-old male presented to the emergency department with pain and discomfort in his left hip triggered by a twisting movement while getting into bed. The patient described a "pop" in his hip upon turning and reported mild ongoing discomfort in his left hip for the past 4 weeks before this acute presentation. X-rays and Metal artifact reduction sequence magnetic resonance image (MARS) revealed head-stem dissociation along with pseudotumor formation. The patient successfully underwent a two stage revision with no perioperative complications.

Conclusion: This case report, to the best of our knowledge, is the first to report catastrophic failure of a metal-on-metal hip caused by trunnionosis and subsequent head-stem dissociation. We report successful management of this unique case and hope to highlight the complexities and challenges associated with metal-on-metal THR. This case report is aimed at raising clinical awareness of this rare complication which requires expert management for a successful outcome.