A Rare Dissociation at the Neck–Stem Interface

The authors report a case of dissociation at the neck–stem interface without hip dislocation that occurred during walking, and discuss strategies to avoid and treat this complication of THA.  Introduction Modular femoral components have the advantages of: •Reducing the need to stock numerous stem and head sizes  •Allowing the final choice of neck length and head size to be made after stem implantation  With moduar femoral components, neck orientation can also be changed after implantation, which is a well-known cause of early dislocation. The incidence of postoperative dislocation of modular total hip arthroplasty (THA) varies from 0.5% to 4% [1]. Dissociation at the neck–stem interface is rare. To the best of our knowledge, only three case reports have been published [2-4], but they pertained to dissociation at the neck–head interface. We report a case of dissociation at the neck–stem interface without hip dislocation that occurred during walking, and we discuss the causes of dissociation as well as strategies to avoid and treat this complication.