Zimmer NexGen Knee Replacement

Who Is Zimmer?

Zimmer Holdings, Inc. is an Indiana-based orthopedics company.  They manufacture medical products including joint and skeletal replacement systems and surgical tools as well as biologics designed to assist in joint replacement surgeries.

Zimmer reported 2011 sales of over $4.4 billion, with $2.4 of that attributed to the Americas.  Knee implant products provide the bulk of revenue with worldwide sales of $1.82 million.  They are the largest knee implant manufacturer in the world with a 26 percent share of the worldwide knee implant market.

Zimmer announced the acquisition of another joint replacement device company, Biomet in April of 2014 for $13.35 billion which made Zimmer the second-largest orthopedics manufacturer in the US once the sale was finalized.

When Did Zimmer Start Manufacturing Knee Replacement Devices?

Zimmer developed its first non-hinged total knee replacement device in 1968 and followed in 1973 with a metal-plastic total knee product.  The NexGen devices were introduced in 1995 with the Next Generation Complete Knee Solution System.  This was followed by a number of NexGen, High Flex devices which were intended to increase the range of motion over that of other devices on the market.

Despite its intent to improve the knee implant market, several of the NexGen products are the subject of multiple lawsuits due to a high rate of revision surgery required from failing implants.

What Is Zimmer’s NexGen Knee Replacement System?

Zimmer manufactures a number of knee replacement devices including total knee systems, unicompartmental systems, femoral, tibial, and patellar implants, and cemented and non-cemented components. They also manufacture gender-specific knee systems and components that are designed to closely mimic the female anatomy.

The NexGen system is one of the implant manufacturer’s main product lines.  It originally offered 120 degrees of flexion which is the closest that manufacturers were able to get to the natural knee flexion of 160 degrees.

When Was the Zimmer NexGen Knee Replacement Approved?

The Food and Drug Administration approved the NexGen LPS-Flex Fixed-Bearing Knee in 1999 which offered 155 degrees of flexion.  The device was approved through the shorter 510(k) approval process, which allows the manufacturer to be exempt from the normal Premarket Approval (PMA) application process.  The PMA process requires that manufacturers submit data from clinical studies performed in humans that prove efficacy and safety.

What Is the 501(k) Approval Process?

The 510(k) process allows the manufacturers to avoid costly and lengthy clinical trials by claiming that the device is substantially similar to a device that is already on the US market.  The PMA process may have identified future failure potential in clinical studies that the 510(k) process did not identify. 510(k) approvals require only post-market surveillance which is based largely on voluntary reports of adverse events.

Who Is the Zimmer NexGen For?

The NexGen line was reported to be the first of its kind by Zimmer and was marketed towards younger and more active patients along with those whose cultural backgrounds, religious beliefs, or employment required extensive kneeling for prayers or spending a good deal of time on the knees.

What Is the Zimmer NexGen CR-Flex Knee System?

Zimmer specializes in developing and manufacturing personalized joint replacements for consumers. Zimmer was among the first companies to play a role in the popularization of knee replacements, or knee arthroplasty. It developed its first total knee replacement device in 1968. Zimmer has grown to become one of the leading companies in this market. It is estimated that Zimmer generates roughly $4 billion in sales each year.

While it has found great success in this market, Zimmer also faces issues from defective devices. A number of patients are filing claims against the company for products such as the Zimmer NexGen CR-Flex knee replacement system. Patients experienced a number of debilitating side effects such as severe pain, infection, bone fracture, and failure of the Zimmer NexGen CR-Flex device. Many patients are forced to undergo revision surgery to correct problems caused by the Zimmer NexGen CR-Flex system.

When Was the Zimmer NexGen CR-Flex Approved?

The Zimmer NexGen CR-Flex system was approved using the 510(k) Premarket Notification process. Through this process, drugs and devices may receive expedited approval if the manufacturer can prove a significant similarity to a product that has already received FDA approval. As a result, the 510(k) process allows for the approval of products that are not yet backed with extensive clinical testing. This means that manufacturers and the FDA become aware of specific product issues only after it has been approved and used by consumers.

Zimmer motioned that the NexGen CR-Flex system was similar to the original NexGen knee replacement product line. This system received FDA approval in 1994. However, the NexGen CR-Flex system is significantly different in that it does not use fixative or cement to attach the components. Instead, the system uses the NexGen CR-Flex Porous Femoral Component.

This component is coated with a porous liner that caps the thigh bone’s connection with the tibia. The porous liner helps to encourage osseointegration or bone growth. It also eliminates the use of cement, which may pollute nearby tissue and enter the bloodstream. While the Zimmer NexGen CR-Flex is beneficial for preventing these issues, many patients have experienced loosening due to incomplete fusion.

What Is the Zimmer LPS-Flex Knee Replacement System?

Zimmer manufactures a number of personalized orthopedic products that specialize in joint replacement technology. Products like the Zimmer NexGen LPS-Flex knee replacement system were designed to provide innovation in knee replacement devices. Marketing for the Zimmer NexGen LPS-Flex device claimed that patients would have greater mobility than with other knee replacement implants.

However, this superior design caused complications for a number of patients. In 2010, Zimmer recalled several lots of the NexGen LPS-Flex Gender Femoral Component due to manufacturing flaws. As a result, several lawsuits have been filed against Zimmer by patients who experienced side effects such as persistent pain and device loosening.

How Is the Zimmer LPS-Flex Designed?

The Zimmer NexGen LPS-Flex knee replacement system was designed to give patients a greater range of motion. The industry standard for knee replacement devices is roughly 120 degrees of flexion. Flexion is the ability to bend the knee. The Zimmer NexGen LPS-Flex boasted 155 degrees of flexion for patients. By marketing the Zimmer NexGen LPS-Flex this way, Zimmer made promises of superior performance.

When the knee bends, three main components are required. The femur, or thighbone, extends from an individual’s pelvis to the knee. During movement, the femur rolls and slides atop the tibia. The tibia is the bone extending from the individual’s knee to the ankle. The patella, or kneecap, slides over the femur during movement.

The Zimmer NexGen LPS-Flex was designed to provide better contact between the patient’s femur and tibia. This would provide greater flexion and comfort when the knee is heavily bent. In order to accomplish this, the Zimmer NexGen LPS-Flex system featured an extended roundness on the artificial femur component. Additionally, the Zimmer NexGen LPS-Flex uses a deep cut-out that allows greater clearance for the patellar tendon. The patella component may then properly cover the patient’s femur during knee bending.

What Is the Zimmer MIS Tibial Component?

Zimmer Holdings, Inc. manufactures a number of products for knee replacement procedures. As part of its NexGen knee replacement line, the company made the Zimmer NexGen MIS Tibial Component. This component was created for use in minimally-invasive surgery (MIS). The Zimmer NexGen MIS Tibial Component is used to replace the patient’s tibia, or shinbone. There are two bones that extend from the knee to the ankle: the tibia and fibula. The tibia is the larger of these.

The Zimmer NexGen MIS Tibial Component is used during knee replacement procedures that involve a smaller incision in order to insert the knee replacement device. As a result, less of the patient’s tendon and muscle are cut during the knee replacement procedure. The Zimmer NexGen MIS Tibial Component was recalled in 2010 due to increased incidences of device loosening when the component was used. A number of patients who received the Zimmer NexGen MIS Tibial Component have experienced complications as a result.

How Is the Zimmer MIS Tibial Component Designed?

The Zimmer NexGen MIS Tibial Component features two main design features that were made to benefit both surgeons and patients. The first is a drop-down stem extension that measured 45 millimeters or 75 millimeters. This stem extension allowed the surgeon to elongate the component after it was already placed inside the bone marrow canal in the patient’s tibia. As a result, a better fit could be accomplished in the event that the bone marrow canal was misshapen due to injury or disease.

The other main feature of the Zimmer NexGen MIS Tibial Component was a broader, shorter keel that locked into the densest part of the patient’s bone. The keel helps the implant to stay fixed and inside the patient’s bone. It is made of fins on the sides of the implant. The ability of the implant to lock into the patient’s bone eliminated the need for cement to fix the implant in place. As a result, cement-related complications could be avoided.

What Are the Side Effects of the Zimmer NexGen?

Hundreds of thousands of people receive knee replacements every year. As a result, knee replacements have become routine surgery performed in the United States. However, the Zimmer prosthesis company has been dealing with lawsuits from the Zimmer NexGen’s side effects associated with knee replacement surgery. Approximately one-third of knee replacement surgeries that were performed with Zimmer knee replacements have either caused health problems to the patient or malfunctioned shortly after surgery.

What Causes the NexGen’s Side Effects?

The Zimmer NexGen’s side effects are mostly caused by a malfunction of the knee replacement, infection to the area, or dislocation of the prosthesis. Many Zimmer side effects also develop after a length of time when the knee replacements become loosened or worn. These complications can become serious without medical attention.

What Are the Most Common Side Effects of the Zimmer NexGen?

The Zimmer NexGen’s side effects have impacted many lives. They can become very painful and inconvenient for patients and in many instances require additional surgery to resolve the issue. In other cases, the Zimmer NexGen’s side effects can be treated with physical therapy or simple medical procedures.

The Zimmer NexGen’s side effects include:

• Severe pain
• Swelling
• Reduced range of motion
• Loosening of device
• Failure of device
• Bone fracture
• Nerve damage
• Joint instability
• Dislocated joint
• Infection
• Blood clot
• Uneven leg length
• Joint stiffness
• Ligament instability
• Dislocated kneecap
• Heart attack
• Stroke

Can the Zimmer NexGen Cause Blood Clots?

Patients may develop blood clots in a leg vein after knee replacement surgery. This can be one of the dangerous Zimmer side effects if blood flow is blocked from the leg to the heart. Blood clots can also migrate into the lungs and cause problems. Blood clots are more common in the elderly and people who are overweight. Past problems with blood clots and cancer are also risk factors.

Can the Zimmer NexGen Cause Infections?

The Zimmer NexGen’s side effects from infection are rare if patients are healthy. Health problems like diabetes, chronic liver disease, or rheumatoid arthritis will increase the likelihood of NexGen’s side effects from infection. Patients prescribed corticosteroids are also at risk. Patients may require antibiotics or additional surgery if infections are deep within the joint. Sometimes it is also necessary to remove the knee replacement.

The infection is more difficult to remove the longer it is present or if it occurs months to years after surgery. In this case, a “staged surgery” is usually required. This process involves removing the implant, washing the implant and soft tissues of the knee, and lining the area with an antibiotic spacer. IV antibiotics are also used for this process.

Can the Zimmer NexGen Cause Nerve Damage?

In rare cases, nerve damage from NexGen side effects may occur near the surgery site. Nerve damage from NexGen’s side effects can cause tingling, numbness, and coordination difficulty. This is often resolved after a few months as the nerve tissue heals.

What Happens if the Patella Is Dislocated?

Another of the NexGen side effects is dislocation of the patella, or kneecap. When this happens, the kneecap moves to the side of the knee. It can often move back into place by flexing the knee but this problem causes discomfort and a feeling of instability in the leg. Kneecap dislocation also interferes with the quadriceps muscles on the front of the leg. Surgery is usually required and sometimes the entire knee replacement must be redone.

The kneecap can also fracture if patients fall or over-strain themselves. This is a visible problem when the patient bends the knee. Doctors can usually treat the fractured kneecap without performing additional surgery.

Can the Zimmer NexGen Cause Mobility Problems?

Some NexGen side effects can develop as a result of scar tissue or other complications. These can interfere with the knee’s ability to flex. Special exercises or physical therapy can help to resolve the stiffness. Severe cases are called arthrofibrosis, or “stiff knee syndrome,” and may need medical treatment to remove the scar tissue.

Are There Complications from the Zimmer NexGen Products?

The original Zimmer knee replacement products had a normal revision rate and were quite reliable. The original design was quite stiff, only offering the normal 120 degrees of flexion.  Subsequent products were intended to offer 155 degrees of flexion but were approved through the 510(k) process and were not required to be tested.  Patients who received these products were implanted with an unproven and untested device.

Which Zimmer NexGen Products Can Cause Complications?

There are three systems that have been under scrutiny due to side effects and failure. These systems include the NexGen Cruciate Retaining Flex (CR-Flex), NexGen Lateral Posterior Stabilization Flex (LPS-Flex), and the NexGen Minimally Invasive Solutions (MIS) Tibial Component.

What Complications Can Zimmer NexGen Cause?

Zimmer knee replacement side effects are mild in most cases but can be serious in others and likely require knee revision surgery due to failure:

• Bruising and swelling of the knee
• Severe pain in the knee
• Poor motion or stiffness of the knee
• Mild side effects may resolve but may become permanent.

More severe effects of Zimmer knee replacement focus mainly on dislocation and loosening of the component from natural bone.  These will often require revision surgery and include:

• Persistent or increasing knee pain
• Nerve and blood vessel damage which may be permanent
• Knee replacement failure resulting in dislocation and severe pain
• Periprosthetic fractures in the bone surrounding the implant

Other patients may also experience events that are rarer in Zimmer knee replacement products but are also severe and may require knee revision such as:

• Infection with fever or chills
• Blood clots creating pain in the lower leg
• Particle shedding from device structure that is deposited into surrounding tissue
• Osteolysis or necrosis (bone dissolution or tissue death) caused by shed particles

Did the FDA Warn About Zimmer’s NexGen Devices?

After numerous studies, the U.S. Food and Drug Administration (FDA) and British Medical Journal (BMJ) identified problems associated with metal-on-metal devices. According to the BMJ, metal-on-metal devices resulted in higher rates of revision therapy, as opposed to metal-on-polyethylene implants. This contrasts with many medical device manufacturers’ claims of increased durability by using metal-on-metal components with materials such as titanium alloy, chromium, and cobalt. In addition to increased rates of revision therapy, the BMJ reported increased chances of hip dislocation and elevated concentrations of metallic ions within the bloodstream.

Patients with the following criteria should not receive a metal-on-metal implant:

• Metal allergy or sensitivity
• Being of or near child-bearing age
• Coping with a suppressed immune system
• Experiencing kidney problems, or with a history of kidney problems
• Using large doses of corticosteroids

Have Any Zimmer NexGen Devices Been Recalled?

Zimmer has recalled some of its NexGen knee replacement devices, including the LPS-Flex and the MIS Tibia Component. However, the company initially stood by the NexGen CR-Flex. That, too, was recalled in 2018, however. The devices facing recall include:

• NexGen MIS Tibial Components
• NexGen TM Tibial Trays
• NexGen LPS-Flex GSF Femoral Component
• NexGen MIS Modular Tibial Plates and Keels
• Natural-Knee II Durasel Patella

What Problems Were There With the NexGen CR-Flex?

The lack of cement in the Zimmer NexGen CR-Flex line has created issues for both surgeons and patients. In 2010, doctors from the Rush University Medical Center in Chicago presented their study results at the American Academy of Orthopedic Surgeons conference. The study discussed the failure rate of high-flex total knee replacements.

In the presentation, the team primarily discussed the Zimmer NexGen CR-Flex system. It noted that more than nine percent of patients who received a NexGen CR-Flex implant required revision surgery due to device loosening and associated pain. Additionally, the study revealed that 36 percent of the 108 participants experienced loosening of the device’s porous femoral component. Researchers observed that this failure rate was not related to the surgeon, surgical approach, or patient type.

What Was the NexGen CR-Flex Controversy?

One of the main researchers behind the Rush University study was Dr. Richard Berger. Nearly a decade prior, Berger was a paid consultant for Zimmer. During his time working with Zimmer, Berger was paid more than $8 million for his services. By 2005, Berger implanted the Zimmer CR-Flex knee system in 125 patients. Within a year of implantation, Berger reported to Zimmer that a number of his patients experienced loosening and severe pain caused by failure of the femoral component to properly fuse to the patients’ bone. Berger stopped using the product in 2005.

Zimmer continued to support the NexGen CR-Flex device. The company insisted that surgical techniques and procedures were responsible for the device’s failure. In June 2010, the New York Times published an article that discussed the dispute between Berger and Zimmer. This brought Zimmer’s public relations issue into the national spotlight.

Why Was the NexGen LPS-Flex Recalled?

In December 2010, the company issued a voluntary recall for certain lots of the Zimmer NexGen LPS-Flex Gender Femoral Component. This component was created specifically for females who need total knee replacement surgery. The recall affected components that were distributed all over the world. According to the FDA, distribution countries included Germany, France, Spain, Bulgaria, and several other countries.

Prior to the recall, Zimmer sent out an “Urgent Device Correction and Removal” notice to distributors, sales associates, surgeons, and risk managers. Those who still had inventory were instructed to return them. Surgeons were not asked to take action but were advised to take notice for future reference.

This Zimmer NexGen LPS-Flex component recall took place due to issues with the device’s cam. The cam is a special bar in the femoral component. In a standard knee device, an internal post located in the cushion of the tibial component is made to fit into the cam. However, the recalled femoral components exhibited a nonconforming cam radius within the device. These nonconforming geometry issues jeopardized the integrity of the knee replacement devices. To avoid widespread complications, Zimmer recalled the components from these specific lots.

What Complications Did the NexGen LPS-Flex Cause?

Many patients experienced premature loosening of their Zimmer NexGen LPS-Flex knee replacement. In 2007, a published study observed 47 patients who received a Zimmer NexGen LPS-Flex knee replacement. Of the 47 patients, 27 experienced device loosening within three years of having the initial knee replacement procedure. Fifteen patients required revision surgery within two years of the initial knee replacement procedure. The study confirmed that high-flexion and weight-bearing activities tended to contribute to the loosening of the Zimmer NexGen LPS-Flex knee replacements.

Studies also show that patients who received a Zimmer NexGen LPS-Flex knee replacement experienced fractures around the implant. One patient in a 2010 study exhibited failure of the knee’s muscle group known as the extensor mechanism. Two patients from the same study experienced instability in the knee.

What Problems Were There With the MIS Tibial Component?

In April 2010, Zimmer responded with an “Urgent Device Correction” letter that was sent to surgeons.

The letter urged surgeons to ensure that they achieve adequate access and visualization during an MIS procedure. Due to the nature of an MIS knee replacement, the surgeon’s view is often restricted during the insertion process. This can cause less optimal placement, which may in turn lead to device failure. The letter also advised surgeons to use a drop-down stem extension when the Zimmer NexGen MIS Tibial Component was used.

Other instructions for surgeons included the need for full cementing during the implantation process. Additionally, the posterior and anterior surfaces of the tibial component were to be pressurized. The bone cement application was to be used according to the manufacturer’s instructions. To accomplish this, Zimmer instructed that previous surgical technique versions were destroyed or disregarded.

Why Was the MIS Tibial Component Recalled?

In September 2010, the FDA issued a Class II recall for the Zimmer NexGen MIS Tibial Component. The recall was in response to 114 medical device reports (MDRs). In these MDRs, patients reported that they experienced device loosening and the need for revision surgery to remove and replace the failed device.

The recall affected the worldwide distribution of the device. It was recalled from more than ten of the United States. Additionally, the Zimmer NexGen MIS Tibial Component was recalled from more than 21 countries, including France, Germany, India, Korea, and Thailand.

What Zimmer NexGen Lawsuits Are There?

All of the 1300 Zimmer NexGen lawsuits have, as of 2022, been settled confidentially. Because of that confidential status, it’s unknown exactly how much each plaintiff received. Zimmer did have to pay out $310 million in fines on top of whatever the company owed to the plaintiffs. This was because the company had received penalties due to claims it had paid kickbacks to surgeons to encourage the use of their devices in 2007.

Notwithstanding claims relating to this product, the drug/medical device remains approved by the U.S. FDA.