March 31, 2013

Extraction Protocol Regarding Stryker ABG II Hip Implants



When the Stryker ABG II was originally marketed it was believed to be a safe alternative to the metal-on-metal hip implants which caused so much damage to recipients. Even though the ABG II does not have the same amount of metal surface to rub together, some of the metal neck junctures have shown signs of corrosion and the metal trunnions, located on either end of the neck portion have also been subject to corrosion when body fluids become trapped underneath.  Once corrosion and fretting occur, the threat of tissue necrosis, bone loss, total implant failure and symptoms of metal toxicity can follow.

Initially surgeons were impressed with the ABG II and the Rejuvenate because of the new modular design which allowed them to choose a stem, neck, ball and cup based on the activity level and size of the individual recipient. This extra flexibility was also meant to give patients a better, longer-lasting hip implant. Unfortunately, the promise of this new design did not pan out, and soon many recipients of the ABG II began to experience inflammation and pain as well as symptoms of metal toxicity.  Those patients who experienced significant problems early on were likely advised to undergo revision surgery in order to remove the Stryker ABG II, however this is not the easy decision it might seem despite the serious adverse symptoms.

Because of the weakened bone and tissue which results from corrosion of the ABG II, there is a significant risk of dislocation following revision surgery. In many Stryker ABG II revision surgeries the femur bone will fracture from the stress of removing the stem of the implant. Revision of the ABG II is considered much riskier than the original hip replacement surgery as the process is much more complex. The ABG II revision surgery can take much longer than the original hip replacement surgery which increases risk of infection and blood loss.

There is a protocol for the removal of the Stryker ABG II which includes removal of the neck implant piece with an ABG II Modular Neck Extractor which is placed under the medial or lateral side of the base of the neck. Neck Trial Forceps are recommended as a means of “catching” the neck during the extraction; should the neck be resistant to removal it is recommended that the Neck Extractor end be tapped in a controlled manner with a mallet. The stem of the Stryker ABG II will next be removed using a Modular Stem Extractor with a connection pin which engages the stem insertion feature and incorporates a locking arm which engages the taper. The threaded locking knob will be tightened which secures the arm. Finally, the stem impactor will push the stem from where it is inserted into the femur.

Extracting the stem is likely the most difficult part of the revision surgery and some orthopedic surgeons have likened it to removing a piece of rebar from a slab of concrete. Stryker ABG II revision surgery can require extra bone material obtained from a bone bank when the stem is removed as the bone can shatter. Because of the additional recovery time, patients who undergo revision surgery to remove a defective ABG II can face exorbitant medical expenses, lost wages from their inability to return to work, short or long-term disabilities and interruptions to their daily routines for considerable lengths of time.