Friday, August 12, 2011

Comparing the Depuy Pinnacle attributes to the Depuy ASR (recalled) device


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 metal-on-metal design is one of the factors that likely called  DePuy to recall the ASR device, as patients experienced pain and infection   when the femoral head could not move freely through the cup causing very small pieces of metal to flake off the device.  It also resulted in higher  projected rates of revision than normal.
  • 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.
(Some of this explanation was taken from the  Zoll, Frank and Brogess site but modified some of the excerpts. Just thought some of the points were interesting.)

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