Collo MIS is a new short stem created to achieve minimal metaepiphyseal invasiveness, to respect the joint physiology, to get optimal primary stability and osteointegration.

This stem needs a subcapital osteotomy to respect and preserve the physiologic anteversion of the femoral neck; the technique provide compactation of the cancellous bone of the greater trochanter using just compactors and not rasps during the femur preparation and the stem has to match the calcar curvature to get the right position.

This stem has been designed with a lateral wedge to ensure a great primary stability in the femoral neck.

Since November 2008 at Niguarda Hospital we have implanted 350 prosthesis in cooperation with Frankfurt Hospital.

Patients age varies form 26 to 80 years old with a mean age of 61 y.o.

This stem has to be implanted in patients with good bone quality to achieve the compactation of the cancellous bone.

We have operated patients affected mostly by coaxrthrosis and just in few cases by dysplasia (Crowe 1); contraindications are represented by a CCD angle less than 120° and more than 140° because of the stem morphology, severe osteoporosis, dymorphism, and dysplasia (Crowe 2,3,4).

We have evaluated the offset and CCD angle pre and post op that resulted mostly increased after surgery (average CCD angle +6,15°, offset + 5.95 mm).

In the post-op we normally give partial weight bearing after 1 day and the full weight bearing after 20 days.

The mean HSS score before surgery was of 57.5 points and after 1 year of 98 points.

The complications we have found in these study were: 11 cases of dysmetrias less than 1 cm, 6 cases of neck fissuration. No infection, mobilization, neck impingemen, subsidence, radiolucency have been evaluated.