Several of the distinctions between the Depuy Pinnacle and the Depuy ASR:
- The ASR cup is made up of one solid piece of metal and the Pinnacle is made up of a cup and liner. As mentioned in a previous post, the Pinnacle cups and liners are available in different types of materials, which allow for three different combinations:
metal -on-metal, metal-on-polyethylene or ceramic-on-polyethylene.
- The ASR’s cup was sub-hemispheric and it was theorized that it was too shallow for the head and thus the system would edge-load, causing the ball to hit the edge of the cup and pieces of metal to flake off. The Pinnacle’s cup, on the other hand, was designed as a full hemisphere, giving it greater depth and allowing the femoral head to move more accurately within the socket.
- There is no way to visually determine if the ASR socket is completely seated in the pelvis, since it lacks any holes in the device. The Pinnacle includes a dome hole that allows surgeons to see how well it fits. The fitting is also facilitated by screws that allow the device to be permanently attached to the pelvic bone.
- The ASR did not require screws, which gave surgeons no way to fix the device to the body; the success of the design depended on the bone growing around and into the device.