Intraprosthetic Dislocation of Dual-Mobility Total Hip Arthroplasty: The Unforeseen Complication

Malseated Liner in Modular Dual Mobility Total Hip Replacement: A Report of Three Cases

Modular dual mobility total hip arthroplasty (THA) can be associated with complications if the liner is malseated, which can be unappreciated intraoperatively. A meticulous surgical technique is needed to ensure that the liner is perfectly seated. In addition, a malseated liner can be missed if the postoperative films are not carefully reviewed by the surgeon. We present three cases of THA associated with a malseated modular dual mobility liner. In one case, the malpositioned liner was appreciated intraoperatively, but it was wedged in place and could not be removed. The entire shell needed to be revised. In two other cases, malseating was not detected intra-operatively. Both were appreciated postoperatively, and early revision surgery was needed.

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.

A Missed Diagnosis of Intraprosthetic Dislocation in a Dual-Mobility Bearing Following Closed Reduction

Dual-mobility bearings have been found to reduce the rate of dislocation following both primary and revision total hip arthroplasty. Their unique design involves two articulating surfaces which increases construct stability but also leaves them susceptible to a unique complication known as intraprosthetic dislocation (IPD). We report the case of a 33-year-old female who sustained an IPD following closed reduction. Following a missed radiographic diagnosis, the patient experienced pain and mechanical symptoms secondary to her implant failure. Surgical removal of the dislodged liner with component revision was required. This case highlights several crucial steps in the management of patients with dislocated total hip arthroplasties including implant identification and careful review of postreduction radiographs. We also discuss several strategies to properly diagnose, manage, and avoid IPD.

Dual Mobility Cups as the Routine Choice in Total Hip Arthroplasty

Background and Objectives: Total hip arthroplasty (THA) is considered the most successful surgical procedure in orthopedics. However, dislocation remains the main indication for surgical revision. New designs of dual mobility cups (DMC) have lowered the classical complications and have extended the indications of DMC in elective surgeries. Our aim is to assess the trend of DMC indications in THA as well as the incidence of their dislocation. Materials and Methods: We retrospectively reviewed all patients undergoing THA with DMC during the years 2015 and 2021. The original indication for DMC included patients sustaining neck of femur fractures (NOF#) and associated risk factors for dislocations. Five years later, DMC was considered our standard of care in total hip arthroplasty. The approach (anterolateral or posterolateral) was chosen by the surgeon according to his/her preferences, as was the implant. Data collected included patients' demographics, diagnosis, admission time, surgical approach, cup models, and inclination and complications. Patients sustaining a hip dislocation were prospectively reviewed and assessed for treatment received, new dislocations, and need for surgical revision. Two groups were created for the analysis according to the presence or absence of dislocation during follow-up. Results: In the analysis, 531 arthroplasties were included (mean age 72.2 years) with a mean follow-up of 2.86 years. The trend of indications for DMC increased from 16% of THA in 2015 to 78% of THA in 2021. We found a total of 8 dislocations (1.5%), none of them associated with elective surgery. Closed reduction was unsatisfactory in four cases (50%). There was one case of intraprosthetic dislocation. Dislocations were associated to smaller heads (22 mm) (1.5% vs. 25%, p = 0.008) and cups (51.2 mm vs. 48.7 mm, p = 0.038) and posterior approach (62.5% vs. 37.5%, p = 0.011). Conclusion: Dual mobility cups are a great option to reduce the risk of dislocation after a THA both in the neck of femur fractures and elective cases. The use of an anterolateral approach in THA after a neck or femur fracture might considerably decrease the risk of dislocation.