DePuy Knee Replacement Problems and Complications
While total knee replacement (TKR) surgery can be the ultimate solution to problems associated with knee pain and deterioration because of disease or trauma, there does not exist any completely suitable replacement for the body’s own anatomical structures.
And because orthopedic companies strive to outdo one another for market share by constantly introducing innovative products and procedures, the potential for adverse effects related to total knee replacement continues to be something that patients should be aware of.
Knee replacement complications may result in pain, discomfort, or partial or total failure of a knee replacement. Severe injuries may occur and/or the need for a knee revision operation and additional rehabilitation. Revision knee surgery is much more difficult than initial implantation and is often complicated by bone loss. It is estimated that about 22,000 knee revision operations are performed in the United States each year; over half of them are done within two years of the patient’s original TKR.
Common Knee Implant Complications And Problems
Loosening Of The Knee Implant
The most common complication of total knee replacement surgery is a gradual loosening of the implant. About 10 percent of all knee joint implants loosen each year. Knee prostheses can come loose for one of two reasons. The first is mechanical and is related to the fact that the knee joint bears a great deal of weight when a person is walking, running, or simply standing.
The metal part of a knee implant must be inserted into the upper part of the tibia after the surgeon has removed the bone’s upper surface. The bone tissue that receives the metal implant is softer than the bone that was removed, which means that the metal implant may sink into the softer bone and gradually loosen.
The second reason for loosening of a knee prosthesis is related to the plastic part of the device which is made of a material called polyethylene. Over time, polyethylene can form small particles of debris as a result of wear. If a patient has an uneven gait, the debris particles may form at a faster rate because one side of the prosthesis will tend to pull away from the bone and the other side will be pushed further into the bone.
These tiny fragments of plastic are absorbed by tissue cells around the knee joint, which becomes inflamed. The inflammatory response begins to dissolve the bone around the prosthesis, a process called osteolysis. As the osteolysis continues, bone loss accelerates and the prosthesis eventually comes loose.
Swelling
Another complication, which may affect some knee replacement patients, is swelling. Swelling generally comes from inflammation of the knee lining or synovium, which, in turn, causes increased production of fluid as a response to irritation. When the body cannot absorb the amount of fluid produced, the effusion, or accumulation of fluid, causes swelling. Swelling can be caused by infection of the knee joint, by overwork or strain to the joint or by osteolysis.
Breakage of Components
Various parts of knee implants can break for an assortment of reasons. Polyethylene components connected to the tibia have been prone to breakage, especially those that have been sterilized by gamma irradiation, which increases the oxidation rate of the substance. Medical device manufacturers stopped using gamma irradiation and moved to ethylene oxide or gas plasma as the sterilization process.
Also, tiny metal fragments detaching from a faulty implant, or because of uneven wear or corrosion, may release cobalt or chrome ions from the joint, which can migrate into the lymphatic system, and from there into the blood supply, causing blood poisoning, or in some cases, malignancies.
Unstable Knee
This complication has been found to occur in about 1 percent of all cases. It can be aggravated by a patient’s weight gain and can lead to total knee failure.
Fractures
Fractures may occur in the bones around the knee prosthesis. About 0.1 percent of all patients will suffer fractures.
Vessel Damage
This is rare complication wherein blood vessels are damaged during surgery. Patients who have undergone previous knee surgeries are more prone to vessel damage.
Peroneal Nerve Damage
The peroneal nerve is a branch of the sciatic nerve, which supplies movement and sensation to the lower leg, foot and toes. Signs of peroneal damage include tingling and/or numbness. In some cases patients may find it hard to move or stretch their leg.
Rigidity
Rigidity occurs when scar tissue forms around the knee joint and limits movement. To counter rigidity, surgeons may try to move the implanted joint to a more desirable angle in order to break the scar tissue formation.
Heat or Warmth in the Knee
This is a normal sensation for several months after knee surgery, but if it persists or comes back, it may indicate a problem.
Pain
This may manifest as a minor soreness or it can be an acute, severe pain that presents itself upon motion or as a constant throbbing.
The FDA Warns DePuy
In August 2010, a warning letter was sent to David Floyd, then president of DePuy Orthopaedics, Inc. by Timothy A. Ulatowski, Director of the Office of Compliance at the Center for Devices and Radiological Health of the Food and Drug Administration (FDA). The letter said the company was marketing its TruMatch Personalized Solutions System, without the required marketing clearance or approval, in violation of the Federal Food, Drug and Cosmetic Act.
TruMatch is a surgical instrumentation and computer software system designed by DePuy to aid in knee implant positioning and procedure efficiency. It was developed after researchers found that even a misalignment as slight as three degrees can lead to uneven wear, instability and increased risk of revision surgery following a knee replacement.
In August 2011, DePuy received an FDA 510(K) clearance for TruMatch Solutions for use with its Sigma Fixed-Bearing Knee System. According to a company press release, the FDA clearance was based in part on “mechanical and alignment accuracy testing.”
Generally, the 510(K) “premarket approval” is issued to a product that is “substantially equivalent” to products already approved and is often criticized for allowing manufacturers to escape the long years of clinical trials usually required of new products presenting a sufficiently unique design. Absent from DePuy’s press release is what preexisting product the company claims TruMatch is substantially equivalent to.
