Intraprosthetic dislocation of dual-mobility total hip arthroplasty implant.

Dual-mobility total hip arthroplasties were developed to decrease the risk of dislocation and instability seen with traditional fixed-bearing total hip arthroplasties. However, dual-mobility constructs, notably the first-generation design, come with a risk of intraprosthetic dislocation (IPD). These dislocations occur when the polyethylene femoral head component is dislodged, causing direct articulation between the inner ceramic femoral head and the metal acetabular shell. This is different than a polyethylene liner dislocation in a standard total hip arthroplasty. Causes of IPD include polyethylene wear and iatrogenic dislocation from closed reduction attempts. Timely identification is essential to reduce the risk of soft tissue metallosis, raised cobalt and chromium levels, and the need for major revisions. This complication can be seen on imaging, but radiologists must be aware of the various components and mechanisms of failure to recognize this unique complication. We present a case of a dual-mobility construct with IPD between the femoral head components, illustrated on radiographs and CT and subsequently confirmed at the time of surgery.