Introducing Double Shell Cups

Following successful clinical trials, conducted by several surgeons, we are introducing a modified acetabular cup for general use. All reports on the modified “Double Shell” cup have been positive.

These cups are compatible with the existing instrumentation and implants. The changes are intended to improve the clinical performance of the cup. The main clinical difficulty we hope to improve on is aseptic loosening.

Innovations:

• The double shell cup isolates the polyethylene from the bone and fully supports the polyethylene inlay.
• The mechanical properties of the outer, titanium, perforated, and plasma coated shell are, now, not in any way affected by the inlay; the inner shell is also produced from pure titanium, anodized (different colors for different cup sizes) and press-fit into the outer shell.
• The recesses spaced around the equator are now visible from the cup opening side. The recesses are deeper and dimensioned to allow use of tangential, interference cortical bone screws of 2.7mm. These screws are optional – if used, we strongly recommend titanium screws. The drill guide for 2.0mm drill bit from the KYON TTA and ALPS systems (04.20.12/06.40.03) will properly fit into these recesses. It is no longer possible to use a central 4.0 screw.
• The inner shape of the polyethylene inlay is not spherical, but designed and machined so as to distribute the contact against the femoral head on a ring shaped area around the central recess which is still used to control the orientation of the cup at impaction. Extensive studies have shown reduced friction, reduced contact stresses and ultimately reduced rate of wear by factor three when compared to a conventional inlay. The reduction of wear is due to both reduced stresses and improved lubrication.

The double shell and Fossa cup have been developed in collaboration with Scyon Orthopedics, both are patent pending and KYON has exclusive rights for use in veterinary surgery. Scyon Fossa cups have been used in human patients. A radiostereometry analysis (RSA) study has shown perfect incorporation at one year post op.