OMNI's modular Apex K2 Hip System provides a wide variety of options for surgeons to provide the best fit for patients during surgery. But modular devices like the Apex K2 may also be more prone to failing, requiring a second surgery to correct problems. Studies show the Apex K2 may fail within one year of implanting, and some patients may choose to file lawsuits against OMNI.
The Apex K2 Modular Hip System is manufactured by OMNI, a medical device company based in Massachusetts. The company began as Apex Surgical in 1999, and in 2004, OMNIlifescience, Inc. bought the comapny. In 2014, the device manufacturer rebranded itself to OMNI. The U.S. Food and Drug Administration originally cleared the Apex K2 device for sale in 2004. The total hip replacement system is made up of a stem, neck and head that can be altered to find the right fit for each patient, since each person’s body is different. According to OMNI, the Apex K2 provides 96 different combinations for the neck and head, allowing surgeons to create the best match for each patient’s body type.
Some of the FDA-approved indications include rheumatoid arthritis, correction of congenital deformity, osteoarthritis and fractures. Surgeons also use the K2 to replace other faulty implants during revision surgery. Surgeons implant the Apex K2 using minimally invasive, bone preserving techniques. Doctors can also choose to assemble the implant prior to implantation or during the surgery.
The titanium K2 stem fits inside the thigh bone. Then, a small metal piece called the neck attaches to the stem, followed by the ball or head. The metal or ceramic head replaces the original head of the femur and rotates against the hip socket allowing a person to walk.
Modular hip systems are made up of many pieces that surgeons mix and match, unlike monoblock systems which come in one piece. While these systems provide a better fit, the problem with some of these designs is that the neck, the smallest part of the system, can break and cause painful dislocation or bone fracture. When this happens, patients have no choice but to undergo revision surgery to replace the implant.
Like many other hip implants the FDA cleared the Apex K2 using the 510(k) premarket process. In this process, manufacturers do not have to test a device if they can compare it to one already on the market. This means the Apex K2 did not undergo rigorous safety testing prior to sale, and some patients may be suffering from injuries caused by the implant. Some may file lawsuits against OMNI.
Apex K2 Hip Complications
OMNI claims the Apex K2’s patented Dual Press Hip Stem Technology makes the connection between the stem and neck stronger and also creates less friction by eliminating extra space at the junction of these two components, making the implant safer. But with any metal-on-metal device there is a chance that the two metal pieces rubbing together may release small metal particles into the surrounding tissues and into the bloodstream.
These particles irritate the surrounding tissue and travel to other parts of the body causing a condition called metallosis, a type of metal poisoning. Metallosis can cause pain, swelling and even weakening of the joint and bone. Eventually it leads to loosening of the implant and device failure which leads to revision surgery.
Symptoms of metallosis include:
- Auditory impairment that may lead to deafness
- Cardiomyopathy (heart problems), including heart failure
- Cognitive impairment
- Implant loosening
- Nerve problems
- Noise coming from the hip
- Skin rashes
- Thyroid problems
- Visual impairment that may lead to blindness
Surgeons treat metallosis with revision surgery and replace the metal implant with one that uses ceramic or plastic surfaces. In some cases, the symptoms will improve after revision. However, some patients are left with pain and loss of mobility for the rest of their lives.
In addition to metallosis, modular hips stems are more prone to breaking at the neck. When this happens, patients must be scheduled for emergency surgery. Fractures of the femur also occur around the stem. Similar problematic stems include the Stryker Rejuvenate and ABG II. In one patient, the metal particles from the implant weakened the bone and tissue surrounding it, causing the femur to break during revision surgery.
Stryker recalled these components in 2012 after it received dozens of adverse event reports. So far, OMNI has made no move to recall the Apex K2. But in Australia, the device is already considered problematic enough to remove from the market.
Device Pulled from Australian Market
In 2012, the Australian equivalent of the FDA, the Australian Register of Therapeutic Goods (ARTG), removed the Apex K2 from the market because it had “a higher than expected revision rate.” The Australian National Joint Replacement Registry (NJRR) collected data on the Apex K2 since 2006.
According to the NJRR’s 2012 annual report, the revision rate for OMNI’s system was 5.5 percent after one year and 9.3 percent after three years. The average acceptable rate of revision is 1.6 percent at one year and 2.8 at three years after implantation.
Another study published in the Journal of Arthroplasty from October 2015 quoted the “unfavorably high early revision rate” of 9.3 percent in three years. This means about 9 out of 100 implants could fail. It also found “potentially concerning subsidence (gradual caving in) of both stems and is the first to describe corrosion (wearing down) at the neck-stem interface.”
Study authors found patients had a reaction in the tissues surrounding the implant called aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL). This condition causes pseudotumors (non-cancerous lesions and swelling) and milky discharge in nearby tissues.
The ARTG recommended that surgeons conduct annual examinations of these patients and monitor them for problems. Unlike the U.S., the Australian government has a national joint registry to track devices after they are sold. This allows them to determine which devices might not be as safe.
In the U.S., the FDA has not released any guidelines for this implant, and it has no way of tracking the devices. However, attorneys began investigating the likelihood that OMNI’s Apex K2 systems may be faulty and expect to file lawsuits on behalf of injured patients.