Dual Mobility Cups as the Routine Choice in Total Hip Arthroplasty

Abstract

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.

Keywords: arthroplasty; dual mobility; hip; replacement.

Figure 1

Trend in the indications for total hip replacements with dual mobility cups in our department as a comparison with the total amount of total hip replacements performed. The line shows the proportion.

Figure 2

Case number 7. Intraprosthetic dislocation. (A) Emergency department X-ray. (B) Control X-ray after closed reduction maneuvers. (C) CT Scan after closed reduction maneuvers. Note the displacement of the head, eccentric within the acetabular cup. (D) Post-op control after revision surgery.

Figure 3

Intraoperative photographs show the dislocated liner (A) and the reduced head in the acetabular cup (B). An attempt to introduce manually the head in the liner to check for an abnormal weakness or defect was performed but was not possible (C).