Outcomes of Dual Mobility Acetabular Cups in Total Hip Arthroplasty Patients.

BACKGROUND

Instability can account for over 20% of all revision total hip arthroplasties (THAs). Although a number of surgical techniques have been developed to limit the number of dislocations, prevention still remains a challenge. More recently, dual mobility (DM) cups have been developed to potentially target this problem. Although this implant design has been shown to have a number of potential advantages in the revision setting, there is limited data in the literature on the use of modular dual mobility (MDM) implants for primary THAs. Therefore, the purpose of this study was to evaluate cup survivorships, patient satisfaction outcomes, and complications of this device used for primary THA.

MATERIALS AND METHODS

A total of 143 consecutive hips (131 patients) who underwent primary THA using DM prostheses by a high-volume academic surgeon were longitudinally followed up for a minimum of five years (mean: 6 years, 11 months; range, 6 years 3 months to 7 years 5 months). There were 77 women (54%) and 66 men (44%) who had a mean age 65 years (range, 34 to 90 years; SD, 11 years), and the mean body mass index (BMI) was 32 kg/m2 (range, 22 to 52; SD, 8 kg/m2). Patient demographics, (gender, BMI), as well as clinical outcomes were analyzed. Kaplan-Meier analysis was performed to determine aseptic, septic, and all-cause cup survivorship. Additionally, clinical outcomes based on Harris Hip Scores (HHS) and other modalities, as well as complications, were tabulated. Institutional review board (IRB) approval was received prior to initiating this study.

RESULTS

Septic survivorship was found to be 99.3% (95% CI: 0.98 to 1.0), while all-cause survivorship was 98.6% (95% CI: 0.97 to 1.0). There were a total of two revision surgeries; however, these were not related to the MDM cup. Specifically, one patient had femoral stem loosening, while another patient had a late deep infection treated with a two-stage procedure. At most recent follow up, both patients were progressing well and had HHS scores of 85 and 92 points. The mean total HHS score was 95 points (range, 64 to 100) at most recent follow up. Other complications affecting patient outcomes included two patients who presented with concerns for deep vein thrombi, which were both medically managed, as well as one patient who had a non-fatal pulmonary embolism, which was also medically managed. The final HHS scores for these three patients were 83, 100, and 96 points.

CONCLUSION

DM cups were designed with the intent of reducing hip instability. Most studies on these cups have reported on revision THA, where the problem of instability may be more paramount; however, fewer studies have reported on the use of this cup for primary THA. The findings from this study indicate excellent survivorship and overall clinical and patient satisfaction results using this construct. These five-year results are very encouraging and hopefully will portend excellent further survivorship with longer follow up.