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Modular Dual Mobility

Mobile Bearing Hip System

Dislocation is one of the most common causes of THA failure in both primary and revision procedures.1-4 Modular Dual Mobility (MDM) is designed to help prevent dislocation and assist your operative goals of stability, longevity, and advanced fixation for fractures, primary or revision total hip arthroplasty cases.

Stryker’s MDM consists of a modular cobalt chrome liner, a large diameter X3 polyethylene insert, and a femoral head. The highly polished modular cobalt chrome liner can be assembled into any of Stryker’s acetabular shells utilizing the Trident Locking Mechanism. Together these components result in a dual mobility device with two points of articulation – one between the X3 polyethylene insert and metal liner (external bearing), and the other between the X3 polyethylene insert and the femoral head (internal bearing). Primary motion occurs at the inner bearing while the outer bearing moves in cases of extreme range of motion, which may minimize wear, reduce frictional torque, and increase stability.5-6

Key benefits


Jump distance (mm) measured with a 54mm shell at 45° of inclination and 20° of anteversion

*Although resurfacing type shells have lower jump heights, they have the greatest ROM which is needed when the native femoral neck is retained.

The X3 polyethylene inserts of the MDM system are available in large sizes offering increased jump distance – the distance the femoral head must travel to dislocate.1 The greater the jump distance, the greater the stability of the hip.7

When compared to a conventional THA with a 36mm femoral head, MDM offers a 59% increase in jump distance.5,8



MDM is a versatile bearing option, as its indications include both primary and revision cases.1-4 MDM utilizes the Trident Innerchange Locking Mechanism, allowing surgeons intraoperative flexibility.

MDM X3 is compatible with Trident, Trident II and Restoration Anatomic acetabular components, offering surgeons a choice of fixation surfaces and screw hole configurations.


MDM X3 Advanced Bearing Technology is designed to minimize the risk of wear, which may prolong the life of the implant and offer your patients greater implant longevity.6,9 X3 precisely engineered polyethylene’s patented manufacturing process of sequential crosslinking uses three separate gamma irradiation doses with an annealing step after each. Our patented process creates a polyethylene that is strong and intrinsically resistant to wear and oxidation.10-12


MDM can reduce cost by decreasing the risk of dislocations.13-16 Compared to conventional total hip arthroplasty, Dual Mobility total hip arthroplasty for primary procedures showed “absolute dominance” with lowered accrued cost and higher accrued utility.13

Clinical evidence

Modular Dual Mobility (MDM), the most studied modular dual mobility implant in literature.

“Dual Mobility demonstrated improved PROMS and lower rates of dislocation, readmission and revision.”

In a 27-center retrospective study of 664 dual mobility vs. 218 fixed bearings, dual mobility demonstrated improved PROMs and lower rates of dislocation, readmission and revision18

“4x reduced incidence of dislocation.”

In a retrospective review of 267 patients who underwent revision, even with a selection bias of using dual mobility for patients at high risk of instability, patients who received an MDM bearing had a 4x reduced incidence of dislocation (2.1%, vs. 8.7% for conventional polyethylene single bearing, P=0.067) at the mean follow-up of 37.8 months19

“Excellent clinical outcomes and patient-reported outcomes at seven-years minimum follow-up (7 - 8.5 yrs.) with zero cup failures in a cohort of 143 patients.”

Excellent clinical outcomes and patient-reported outcomes at seven-years minimum follow-up (7 - 8.5 yrs.) with zero cup failures in a cohort of 143 patients17


Listen to Dr. Geoffrey Westrich talk about the economic value and applications for Modular Dual Mobility.