Zimmer NexGen CR
Zimmer NexGen CR-Flex
Zimmer NexGen LPS
Zimme NexGen LPS-Flex

The Zimmer NexGen knee replacement story is a sad one. The supposedly revolutionary knee implant was designed to give patients more range of motion and brought hope to senior runners, golfers and gardeners, and young athletes too. But numerous incidents where the knee devices came loose subjected thousands of patients to painful revision surgery, or worse. Our defective medical device lawyers at Searcy Denney are experienced in cases involving Zimmer NexGen knee implants.

Zimmer Holdings, Inc. introduced the first metal and plastic knee replacement device in 1973, and, since 1995, a total of more than 1.45 million knee systems have been implanted in American patients. U.S. sales in 2009 alone totaled more than a billion dollars. With 27% of the market share, Zimmer remains the most successful manufacturer, primarily because of its popular “NexGen” models.

Products in the Zimmer NexGen knee replacement family all have three basic components:

  • A metal femoral component that curves around the top of the femur (the thigh bone) and is grooved so that the kneecap can move up and down as the knee bends and straightens.
  • A plastic articular surface component, made of polyethylene, which attaches to a tibial base plate (at the top of the shin bone) and serves as artificial cartilage;
  • A metal tibial base plate that replaces the tip of the shin bone, usually attached by way of a stem inserted into the center of the tibia for stability.

There are several different members of this family of devices, each of which has distinct qualities appropriate for specific patient situations:

  • NexGen CR and NexGen CR-Flex knees are used when a patient’s cruciate ligaments are sufficiently strong for joint stability. Cruciate ligaments are any paired sets of ligaments that cross over each other; in the case of the knee, the crossing of anterior (front) and posterior (rear) cruciate ligaments helps stabilize forward and backward motion of the knee.

The difference between the NexGen CR knee and NexGen CR-Flex knee is the amount of flexion that a patient can gain. Flexion is ability to bend at the knee. Generally, about 90 degrees of knee flexion is required to go up and down stairs, and between 90 and 110 degrees of flexion is required to sit and stand. Zimmer NexGen CR offers up to 120 degrees of flexion, while NexGen CR-Flex offers as much as 155 degrees of flexion.

  • NexGen LPS and LPS-Flex knee replacement models refer to what Zimmer calls “Legacy Posterior Stabilized” devices. Both LPS models provide thickened posterior condyles for patients with weak posterior cruciate ligaments. A condyle is a rounded projection at the end of a bone that anchors muscles and ligaments and articulates with another bone to form a joint that flexes and bends – in this case, a joint between the femur and the tibia.

As with the NexGen CR models, NexGen LPS and NexGen LPS-Flex devices differ in the amount of flexion that they offer. NexGen LPS provides up to 120 degrees of flexion, and NexGen LPS-Flex offers up to 155 degrees of flexion. In addition, the NexGen LPS-Flex model includes a larger, deeper anterior (front) cutout on the articular surface.

Your Florida product liability attorney says recent evidence indicates that these NexGen knee replacement models can fail to adhere to a patient’s bones, whether the device is cemented into place or not. There are also documented failures of Zimmer’s Gender Solutions High-Flex Knee, made especially to fit the anatomical shape of a woman’s knee, and in knee replacement devices implanted using Zimmer’s Minimally Invasive Solution (MIS) system, which involves smaller incisions and less blood loss, and can mean shorter rehabilitation time for the patient.

In the past few years, patients with Zimmer’s NexGen knee replacement are finding themselves back on the operating table because connections between their bones and knee devices have come loose. Zimmer’s posture has remained primarily one of denial. Unfortunately, there are no independent sources of corroboration when disputes arise about the safety of orthopedic devices – because no one tracks their performance. Zimmer’s FDA approval was gained through a fast-track process known as 510k, which does not require medical device manufacturers to prove safety or efficacy prior to marketing a product. Human trials are not required although some manufacturers do perform them.

The NexGen Complete Knee Solution was approved by the FDA in 1995 without having to provide studies affirming the device’s safety or effectiveness. The NexGen LPS-Flex knee was approved in 1999 and the NexGen CR-Flex knee in 2003 – both by the same fast-track process. So when orthopedic specialists voiced suspicions of design defects that were causing early loosening, Zimmer dismissed these findings.

One surgeon who spoke out, however, was Dr. Richard A. Berger, who designed artificial joints for Zimmer for years and trained hundreds of surgeons to use Zimmer products. In March 2010, Dr.Berger went public with a study that suggested Zimmer’s NexGen knees were failing prematurely. At a joint conference of the American Academy of Orthopaedic Surgeons and the American Association of Orthopaedic Surgeons, Dr. Berger and his colleagues presented results of their investigation of 146 Zimmer NexGen knee devices implanted in 2005.

Within a year of implantation x-rays showed cases where, the NexGen knees had not fused, and were loosening. 36% of the NexGen knees in Dr. Berger’s study loosened, and 9.3% of these cases required revisions. (Revisions are further surgery to combat infection, correct defects, and/or remove the knee replacement device entirely.)

Zimmer disagreed with Dr. Berger’s findings, and fired him. But Dr. Berger’s allegations opened the door to further examination of the efficacy of the NextGen implants:

  • In 2008, adverse event reports began to surface in the FDA’s database of knee pain, polyethylene wear, and variance in the sizes of implant components.
  • In 2009, Robert L. Barrack, MD, published in the Journal of Arthroplasty results of his study of 237 first-time revisions of total knee replacement surgeries. 18.6% of the revisions involved Zimmer’s MIS system. He found that failures occurred in a shorter time among patients who had undergone MIS compared to patients with standard knee arthroscopy. Dr. Barrack concluded that, “High prevalence of MIS failures occurring within 24 months is disturbing and warrants further investigation.”
  • The January 2011 Journal of Arthroplasty published results of a study by Jared R.H. Foran, MD, and colleagues, which included 460 patients with implants containing NexGen MIS tibial components. Dr. Foran and his colleagues noted substantial early loosening of devices and radiographic (x-ray) signs of device failure. The authors discontinued their use of the MIS system pending determination of the etiology (causation) of the high failure rate.

In June 2009, the FDA weighed in with a Class 2 recall of the Zimmer NexGen Legacy (LSD) knee. Your Florida product liability lawyer explains Class 2 recalls indicate that a medical device is “potentially dangerous.” This was the first of a list of recalls of Zimmer NexGen knee implants:

  • June 25, 2009 Class 2 Recall, Legacy Knee: Implant surface not polished adequately, causing wear and possible polyethylene debris.
  • June 30, 2009 Class 2 Recall, Natural Knee System Modular Cemented Tibial Baseplate: Tibial spacer does not affix to distal (outer) surface of the base plate, as intended.
  • July 6, 2009 Class 2 Recall, Zimmer Femoral System: Threads on screw incomplete/non-functional.
  • November 13, 2009 Class 2 Recall, Gender Solutions Natural Knee Flex System: Surgeons may have difficulty inserting the polyethylene into tibial baseplate, resulting in damage to the device.
  • September 13, 2010, Class 2 Recall, NexGen MIS Tibial Components: Locking screws and stem extensions are associated with loosening of device, requiring revision surgery.
  • December 2, 2010 Class 2 Recall, NexGen LPS and LPS Flex Gender Femoral Components: Nonconforming internal CAM radius. (A cam is a rotating piece to allow movement from rotary to linear motion.)
  • April 14, 2011 Class 2 Recall, Posterior Referencing Sizer: Black coating break down with possible effect on surgical sites.

The defects in Zimmer’s NexGen Total Knee Replacement products have taken a human toll: Thousands of patients excited about “new” knees to increase their mobility instead have suffered pain, and, in some cases, additional surgery.

A typical knee replacement lasts about 15 years, but many patients with Zimmer NexGen knee replacement devicesfind their knee replacements failing often within just a few years. Some of the symptoms associated with failure of these devices include:

  • Loosening of the attachment between the bone and artificial device, which occurs in both cemented and uncemented artificial joints
  • Painful stiffness or infection
  • Fractures near the artificial joint
  • Instability
  • Wear and tear on plastic parts
  • Breakage, especially metal breaks from constant weight-bearing stress

The potential complications of revision surgery are themselves painful and debilitating, and can result in permanent damage or even death:

  • Complications from anesthesia
  • Thrombophlebitis (blood clots in the legs)
  • Infection
  • Myositis ossificans (calcium deposits in soft tissue around the knee joint, causing inflammation of muscles where they meet the bone)
  • Loosening where a metal component or cement meets the bone
  • Incision complications
  • Bone fractures during surgery
  • Dislocation of the new prothesis
  • A difference in leg length because of the artificial knee
  • More or faster loss of bone tissue

Many medical experts have concluded that the problems with Zimmer NexGen knee replacement products stem from the high flexion of these devices, which puts higher pressure on the knee; cementless insertion, which results in less initial stability; and the MIS system, which does not give the surgeon a good view of the knee and often results in poor fixation of the device. A number of patients who have suffered pain, infection, and/or revision have filed lawsuits against Zimmer, which are expected to be consolidated as mass torts at federal and state levels for discovery purposes.

Defective Medical Device Lawyers Conclude

People considering knee replacement should be very careful about the medical devices they allow surgeons to place in their bodies. Just because the FDA allows a manufacturer to sell a product does not mean the product is safe. Before undergoing any joint replacement surgery, ask your surgeon what type of device they intend to implant in your body. Do your own research. Finally, have a candid conversation with your surgeon about your concerns and make sure both you and your surgeon feel confident that the implant that will be placed in your body is safe for you.

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