gms | German Medical Science

Objectives: Dislocation continues to be a major complication of THA, as evidenced by European register findings. In British National Register 2012, risk of revision for instability for uncemented THA is 1.37% during first year, independently of closed reductions. In 2010 Swedish register, 35% of revisions during first year after implantation are due to instability. More specially, published studies have found that three-quarter of hip dislocation occur within one year of the procedure. Dual mobility cups were first introduced in France 40 years ago with a dual purpose : to provide prosthetic stability through retention and to reduce wear, by reducing constraints in order to increase its longevity. Various publications have confirmed the achievement of the first goal (dislocation rate < 2%). We wanted to evaluate efficacy of the latest generation cup in preventing early dislocation.

Methods: A dual mobility cup having a pure hemispherical shape was implanted by 7 different surgeons at 5 facilities for arthritis (77%), fractures (13%), necrosis (6%) or others (4%) (prospective, continuous, multicentre study). Antero lateral (16%) or posterior (84%) were used. Cementless fixation occurs through a bilayer coating of porous titanium underlayer that is covered by a hydroxyapatite layer. Between May 2012 and December 2013, 643 cups were implanted during primary THA in 631 patients (73 years old, 66% women). All were reviewed at 1 year.

Results and Conclusion: A the latest follow up, Oxford score was good: 15.6. There were no acetabular component revisions and only one dislocation (0.16%) ; fracture case), which is less than registers datas.. Three early complications occurred: one paralysis of sciatic nerve and two site infections. One late complication occured: one haematoma in a patient taking anti-coagulants. Geometry of this new dual mobility cup does not limit joint range of motion and avoids impingement and wear of the retaining collar. It is an effective option for preventing early dislocation after total hip arthroplasty, in comparison of standard uncemented cups, regardless of surgical approach.