In our experience this type of cup finds a perfect indication in patients over the age of 75, or in younger patients with heavy risk of instability (alcoholism, neuropathic or psychiatric cases, 10 cases in the present series).

The cup used is a Cobalt Chromium alloy made, Double Mobility, pure Press-fit and double coated Cup. Following the Bousquet’s philosophy of the Double Mobility Cup we developed the concept with these improvements:

• A peripheral press-fit, avoiding ischiatic and pubic pins which affect the internal polished surface accelerating the polyethylene mobile liner degradation;

• External Vacuum Plasma Spray double coating in Titanium covered with Hydroxylapathite.

• Modified design of the retentive mobile liner, with bevelled edge and different sizes of radius, all devised to improve the head retention, the ROM of the stem and the mobility of the liner, reducing neck impingement, friction and thereby, the risks of wear and tear on the PE.

In this series the 2M Double Mobility system was systematically coupled with a cemented stem of the Charnley Kerboull type with stainless 22mm steel heads, or 28mm for the larger sizes (over 56 mm).

The Instrument Set is designed to allow a minimally invasive approach, for this series we used the Moore postero lateral approach with an average incision length of 10,5 cm (min. 8,5, max. 12,5).

We used an angled reamer handle and impaction was made after reaming from size to size. A good peripheral contact with the trial cup always resulted in an excellent press fit with the final component, obtained by the external design of the cup, conceived to assure excellent primary fixation and enhancing secondary osteo-integration by the coating.

In almost thirty cases of this series an own bone graft was also associated with the acetabular cup, to either make up for an underlying bone defect (protrusions) or a partial defect of the roof , without compromising the primary stability of the implant.

All the patients were examined after 2 months post-operatively and yearly. None of the implants presented any signs of fixation faults (edging or loosening) primary or secondary.

The clinical results were good depending on the general condition of the patient.

We had to drain two haematomas collected at day 21 and day 30 linked to the splitting open of posterior stitches in overindulgent patients, without consequence for the final result. No dislocations took place, whether exterior or interior to the prosthesis.

These short term results are promising, and the Lima 2M Double Mobility system seems to be an excellent therapeutic alternative for elderly patients or those at heightened risk of dislocation. For this reason, since March 2008 we have been routinely using this system in the above mentioned indication (456 cups up to November 2009).

The design of the 2M Cup, the mobile liner and the dedicated Instrument Set perfectly meet the requirements of a primary double mobility cup.