Monolithic Dual Mobility Cup Total Hip Arthroplasty Has High Complication Rates With Surgical Fixation in Elderly With Femur Neck Fracture

Dual-Mobility Cups in Primary Total Hip Arthroplasty

Dual-mobility cups (DMCs) were introduced in France more than 40 years ago and are increasingly used not only in hip revision but also primary hip arthroplasty. Due to a simulated large-head articulation and increased jumping distance, DMCs can contribute to a high range of motion in the hip joint and reduce the risk of instability. Numerous studies have reported low dislocation rates and high survival rates in the mid-term follow-up. Nevertheless, long-term data, especially on primary hip replacement, remain limited, and the effect of recent designs and material innovations is still unclear. Therefore, primary DMCs are mainly proposed in patients at high risk for dislocation (i.e. pelvitrochanteric insufficiency, compromised spinopelvic mobility, neuromuscular disorders, obesity and femoral neck fractures). Based on a review of recently published studies referring to these indications, the current study discusses the advantages and disadvantages of DMCs.

Comparing Outcomes of Total Hip Arthroplasty for Displaced Neck of Femur Fractures in Elderly Patients Utilizing Dual Mobility Cups and Conventional Implants: A Single Center Retrospective Study of 129 Patients

Introduction

Studies comparing the use of total hip arthroplasty (THA) with conventional implants and hemiarthroplasty for displaced femoral neck fractures (DFNF) have reported better patient satisfaction scores and outcomes in the former, but also significant dislocation rates (6.9-13%).The total hip arthroplasty with dual mobility cup (THA-DMC) design is mechanically proven to increase the hip range of motion and jump distance to dislocation relative to conventional implants. Despite its potential benefit, clinical studies analyzing the use of THA-DMC in the treatment of DFNF in comparison to conventional THA within the Asian population are still limited. Our study aims to compare the rate of complications and functional outcomes between the 2 implants in the treatment of DFNF.

Materials and Methods

This was a retrospective cohort study conducted in a single tertiary care institution. From January 2015 to May 2020, data from 129 consecutive patients who satisfied the inclusion criteria and underwent either a THA or THA-DMC for DFNF were collected and divided into 2 groups. All patients received a standardized post-operative treatment and follow-up regime. Both groups of patients were assessed for post-operative complications such as dislocation, peri-prosthetic fractures, surgical site infections, medical complications. Their functional outcomes as well as patient-reported outcome scores were also assessed via the SF-36 score and Oxford hip score questionnaires at 6 months and 1 year.

Results

A total of 42 patients with dual mobility implants and 87 patients with conventional implants were recruited. There was no dislocation in the THA-DMC group while there were 4 cases (4/87, 4.6%) of dislocation in the THA group. Regarding post-operative function, both groups had comparable functional outcomes. There were no statistically significant differences between the patient-reported outcome scores (Oxford hip score and SF-36) at 6 months and 1 year.

Conclusion

We report promising short-term outcomes utilizing dual mobility implants in total hip arthroplasty for the treatment of DFNFs.

Does the Dual Mobility Cup Reduce Dislocation After Primary Total Hip Arthroplasty in Elderly Patients at High Risk of Dislocation?

OBJECTIVE

The dual mobility cup (DMC) is designed to extend the longevity of the prosthesis by improving stability, enhancing the range of motion, and decreasing impingement without increasing wear. We hypothesized that DMC would reduce the risk of dislocation in elderly patients. This study aimed to investigate the clinical and radiographic outcomes of DMC-total hip arthroplasty (THA) in elderly patients at high risk of dislocation.

METHODS

From June 2016 to March 2020, 94 patients with a mean age of 77.7 years (97 hips) who underwent a posterolateral approach for DMC-THA in our department were followed up for at least one year. Preoperative and postoperative pelvic tilt angles (PTA) and DMC orientation were prospectively collected for all patients. Intraoperative and postoperative complications were recorded. A parametric test was used for normal distribution, and a non-parametric test was used for non-normal distribution.

RESULTS

Abduction and anteversion angles of the cup were 42.4 and 18.0° in the supine position immediately postoperative. The average PTA for patients in the supine and standing positions were 26.5 and 34.5°, respectively. When moving from the supine to the standing position, patients experienced a mean posterior pelvic tilt of 9°. No intraoperative acetabular-related complications were recorded. Postoperative complications included early infection in one patient (1.0%) and dislocation in one patient (1.0%).

CONCLUSION

Our study demonstrates that DMC-THA provides satisfactory short-term outcomes in elderly patients at a high risk of dislocation, regardless of the change in PTA resulting from postural transition.

Total Hip Arthroplasty (THA) for Femoral Neck Fractures: Comparison between Standard and Dual Mobility Implants

The purpose of this retrospective study is to compare the short-term clinical and radiological results between standard and dual mobility THA for femoral neck fractures (FNF) in older patients. The hypothesis is that the dual mobility cup (DMC) has the same outcomes but a lower dislocation rate than the standard THA. The study population included 56 patients (mean age 77.7 years, range 71–85) that underwent THA for displaced FNF. Patients were divided in two comparable groups for baseline characteristics (age, sex and comorbidities): 28 patients underwent THA with a standard cup (SC) and 28 THA with DMCs. The clinical records and radiograms were reviewed to search relevant data in their postoperative history. Two postoperative dislocations occurred in the SC group and none in the DMC group. At an average follow up of 23 months (12–40), 48 patients were available for the final evaluation. The WOMAC score for all patients averaged 6.26 (0–46) and was slightly better in the DMC group (4.94 vs. 7.58; p-value = 0.41); scores were significantly better in presence of neurological comorbidities (p-value = 0.04), in the absence of diabetes (p-value = 0.04) and in the case of psychiatric disorders (p-value = 0.02). Radiographic evaluation at one year showed signs of osteointegration in 42/48 (87.5%) acetabular components (20 DMCs, 22 SC). According to our experience, DMCs proved to be a valid option for the treatment of displaced FNF in older patients, since it allowed them to achieve short-term outcomes comparable to conventional THA, while decreasing the incidence of postoperative dislocations.