Recipients of a Stryker ABG II hip implant device can suffer serious health issues as a result of a recalled device. The ABG II, along with the Rejuvenate, was recalled in July of 2012 due to the potential for fretting and corrosion. When fretting and corrosion occur, tiny metal particles can shear away from the implant, burrowing into surrounding tissues or entering the bloodstream. When shards of cobalt and chromium lodge into the hip tissue, it can result in pain, immobility, tissue degradation and death, bone loss, fracturing bones and loosening of the device, and even total hip failure. When such failure occurs, revision surgery will be necessary to remove the ABG II implant and replace it with a ceramic or polyethylene hip implant device.
Revision of the ABG II differs from other metal-on-metal implant extractions and is riskier than the original hip replacement surgery because the procedure is much more complex. In many cases extra bone will be necessary and must be obtained from a bone bank. Muscle surrounding the hip may have deteriorated to the point that the strength of the joint will be compromised following revision surgery. Because the surgery takes longer than initial hip replacement surgery, normal surgical risks and complications are increased as well.
The protocol for extracting the Stryker ABG II requires removal of the neck implant with an ABG II Modular Neck Extractor. The Neck Extractor is placed under the medial or lateral side of the base of the neck with Neck Trial Forceps recommended to “catch” the neck during the extraction. Should the neck resist removal, it is recommended that the end of the Neck Extractor be tapped in a controlled manner with a mallet. To remove the stem of the Stryker ABG II, a Modular Stem Extractor with a connection pin is utilized. This connection pin engages the stem insertion feature and incorporates a locking arm which engages the taper. The threaded locking knob is tightened, securing the arm then the stem impactor pushes the stem out of the femur. Removing the femoral stem has been described by one orthopedic surgeon as “trying to remove a 1” piece of rebar from a slab of concrete.”
There is a risk of dislocation following the surgery due to the weakened bone and tissue, and in some cases the femur bone can fracture during the extraction process. Because the recovery time is substantially longer following an ABG II revision surgery, patients who have undergone ABG II revision can face extremely high medical expenses, lost wages, long-term disabilities and significant interruptions to their daily lives. Even though the ABG II is not a true metal-on-metal hip implant, the design implemented metal trunnions located on either end of the neck portion which were subject to corrosion as fluids became trapped beneath the trunnions. Although the levels of metal shear from the ABG II are unlikely to reach the same levels as those from the all-metal hip implants any amount of cobalt and chromium in the body above the normal levels of 0.5 parts per billion likely point to corrosion of the implant.
Once corrosion has occurred, the threat of tissue necrosis, bone loss, metal toxicity and implant failure increase. Even those patients who are most severely affected by the corrosion from the Stryker ABG II can have a difficult decision to undergo revision surgery. Many patients may not have even had time to properly heal from the initial hip replacement surgery and now face a difficult and potentially traumatic second surgery. Even in the face of metal ions circulating in the bloodstream and the rapid progression of tissues and muscle deterioration, the decision to undergo revision surgery is one that can be very stressful. The patient’s age, general health and activity levels can have significant effect on the outcome of the revision surgery.