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.
