Zimmer NexGen Knee Replacements

Zimmer NexGen Knee Replacement system was intended to increase range of motion over other devices on the market but several of the Next Generation devices have been the subject of multiple lawsuits and resulted in a high rate of revision surgery.

zimmer nexgen knee replacement

Zimmer Holdings, Inc. is an Indiana base 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 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 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.

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

Design of Zimmer Knee Replacement Products

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 closer 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.

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.

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.

The NexGen line was reportedly 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.

Zimmer Knee Replacement Side Effects

nexgen zimmer knee side effectsHundreds of thousands of people receive knee replacements every year. As a result, knee replacements have become a routine surgery performed in the United States. However, the Zimmer prosthesis company has been dealing with lawsuits from Zimmer 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.

Zimmer 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.

Common Zimmer Side Effects

Zimmer 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, Zimmer side effects can be treated with physical therapy or simple medical procedures.

Zimmer 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

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.


Zimmer 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 Zimmer side effects from infection. Patients prescribed to 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 of 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.

Nerve Damage

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

Zimmer Side Effects of the Kneecap

Another of the Zimmer 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.

Motion Problems from Zimmer Side Effects

Some Zimmer 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.

Zimmer Knee Replacement Complications

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.

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.

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 around 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 bone surrounding the implant

Other patients may also experience events which 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

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.

NexGen CR-Flex FDA Approval

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 which 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.

NexGen CR-Flex Study

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.

NexGen CR-Flex Controversy

One of the main researchers behind the Rush University 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 by 2005.

Zimmer continued to support the NexGen CR-Flex device. The company insisted that surgical techniques and procedures were responsible for the device 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.

Zimmer NexGen LPS-Flex System

zimmer lps flex nexgenZimmer 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.

Zimmer NexGen LPS-Flex Design

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 among 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.

NexGen LPS-Flex Component Recall

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.

Zimmer NexGen LPS-Flex Complications

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 a revision surgery before two years of the initial knee replacement procedure. The study confirmed that high-flexion and weight-bearing activities tended to contribute to 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.

Zimmer NexGen MIS Tibial Components

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.

NexGen MIS Tibial Component Design

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 which 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.

NexGen MIS Tibial Component Letter

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.

NexGen MIS Tibial Component Recall

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 reportings (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 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.

Zimmer NexGen Knee Replacement Recalls and Lawsuits

Zimmer, along with three other device manufacturers agreed to pay $310 million in fines and penalties regarding claims that they paid kickbacks to surgeons for the use of their devices in 2007.  Several of the NexGen Devices have been recalled due to high failure rates, mostly related to unseating of the device implants resulting in revision surgery.

In April of 2010 Zimmer issued a safety letter regarding the high failure rate of theNexGen MIS Tibial Component urging physicians to disregard instructions for implanting of the device and conducted a relabeling campaign.  In September of 2010, this action was classified by the FDA as part of a Class II recall.  Already 68,000 components had already been implanted in patients in the US.

Another product, not part of the NexGen line, the Natural-Knee II Durasel Patella was originally manufactured by Sulzer Medica, acquired by Zimmer was also recalled by the FDA as part of a Class II recall.  The Natural-Knee product will be separate to any litigation regarding NexGen products.

Sulzer had previously paid $1 billion to settle lawsuits for some of its other implants and the Natural-Knee component had already been implanted in 110,000 US patients.

Products facing recall and lawsuits 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

Zimmer is currently facing over 1300 lawsuits regarding failed knee implants.  Federal lawsuits regarding Zimmer NexGen implants have been consolidated in multidistrict legislation (MDL) in the US District Court of Northern Illinois overseen by Judge Rebecca Pallmeyer.  The first bellweather trial involving six cases has been set for February of 2015.

Multiple rounds of additional lawsuits are expected in both federal and state courts.

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

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