Use of a Dual mobility cup to prevent hip early arthroplasty dislocation in patients at high falls risk

Hip fracture is a common serious injury that occurs mainly in elderly. Dual-mobility hip arthroplasty or bipolar emiarthroplasty for its treatment remains a controversial decision. Co-morbidities and risk of fall represent additional aspects to be considered. The aim of our study was to determine the rate of mechanical complications for these two types of implants related to fall risk status of patients.

Our study is a retrospective clinical trial of patients operated with a biarticular hemiarthroplasty or a dual-mobility total hip arthroplasty. Primary outcome was dislocation rate and need for any revision procedure. Patients were treated in a single center from January 2013 to March 2017. In all cases Morse Fall Scale (MSF) was calculated at patient admission to evaluate the risk of postoperative fall. Inclusion criteria to the study were: subcapital or femoral neck fracture of non-pathologic nature, patients with neuromuscular disorders or cognitive dysfunction, age > 75 years with MFS ≥ 45. The patients were reviewed postoperatively at 8 weeks, 6 months, 12 months, and then annually. Patients had clinical (Harris hip score) and radiological assessment.

The mean duration of the follow-up was 283 months. There were five dislocations in Group A (5,6%) and no dislocations in Group B (0%). All dislocations occurred within the first 6 months after surgery. The mean Harris Hip score was 81,7 in Group A patients and 79, 8 in Group B patients.

Treatment of hip fractures on non-cooperative patients still represents a dilemma. Falls and runaway motions represent high risk factors of dislocation. Use of dual-mobility cup has been found to be associated with a not statistically proved decrease of dislocation compared to traditional cups.

Dual-mobility cups might be considered a valuable option to prevent postoperative dislocation but further study is needed before extending the indications for dual-mobility following a fracture of the femoral neck, to assess the potential cost and complications of a longer procedure. So far, despite a lower dislocation risk, the authors actually cannot recommend widely use of a dual-motility cup instead of emiarthroplasty in high falls risk patients.