DePuy is the world’s second largest manufacturer of artificial knee implants. Unfortunately, some of the company’s knees can lead to complications.
DePuy knees are manufactured by DePuy Orthopaedics, part of the DePuy Synthes family of companies. In 2010, DePuy secured $923.5 million in knee implant sales with a 22.7 percent share of the market.
DePuy Knee Replacement Products and Technology
DePuy’s most well-known knee replacement products include the Sigma and LCS Complete line of products. The company introduced its LCS (low contact stress) knee system in 1977, and after years of testing, the device gained U.S. Food and Drug Administration (FDA) approval in the early 1980s.
DePuy designed the LCS system to closely resemble the mechanics of the human knee. To date, it has been used in more than 700,000 knee replacement surgeries worldwide. In the late 1990s, DePuy introduced an LCS product for full knee replacements and revision surgeries, which prompted the line’s name change to LCS Complete.
According to Johnson & Johnson, doctors have implanted the Sigma Knee System in an estimated 1.7 million patients. The company markets the Sigma knee’s ability to reduce pain and improve range of motion, as well as function, in the knees. DePuy also manufactures software called TruMatch Personal Solutions that allows customization for Sigma Knee implants.
DePuy knee systems feature interchangeable components for doctors to choose from, and come in several varieties to fit each patient’s unique needs:
Fixed Bearing Knees
Fixed bearing knees are the most widely used in the United States. In this type of device, the bearing remains in a fixed position and cannot move. DePuy claims that fixed bearing implants remain in 99.6 percent of recipients after five years.
Rotating Platform Knees
Rotating platform knees are designed to provide more natural movement, which allows the bearing to rotate in the same manner as the anatomical knee. Rotating knees are designed to reduce stress and wear on the implant by 94 percent.
High Flexion Knees
DePuy also markets high flexion technology for some of its knee replacement products. This allows the implant to flex up to 155 degrees, well beyond the range of traditional implants. According to the company, high knee flexion movement occurs every time a person kneels, squats or crosses their legs.
DePuy markets high flexion knees to people who participate in social, cultural, religious and exercise activities that would be painful or impossible with traditional implant designs.
Total Knee Replacements
In total knee replacement surgery, surgeons use several implant components to restore the function of a severely damaged knee. During the procedure, also known as arthroplasty, surgeons resurface the bones at the bottom of the femur (thighbone) and the top of the tibia (shinbone) in order to attach implants made of materials such as plastic, ceramic or metal.
DePuy markets several total knee replacement systems with a variety of interchangeable components.
|DePuy Total Knee Replacements:|
|Fixed Bearing Models||Rotating Platform Models|
|Sigma Fixed Bearing Knee System||Sigma Rotating Platform Knee System|
|CR150 High Flex Knee System||Sigma RP-F Knee System|
|LCS Complete Knee|
|CR150 High Flex Knee System|
Partial Knee Replacements
Surgeons often perform partial knee replacement surgery in early intervention cases where only one or two parts of the knee are diseased. DePuy manufactures Sigma High Performance Partial Knee components that can replace any of the damaged parts individually.
Partial knee replacement surgery is less invasive than a total knee replacement and allows patients to retain more of their original knee. Patients also generally recover faster from partial knee replacement surgery.
DePuy Revision Components
Knee replacement revision surgery is a follow-up procedure that is required when one or more components from a past knee surgery fails. In the revision procedure, surgeons remove the faulty device or component and replace it with a new, specialized prosthesis.
About 50,000 knee revision surgeries are performed in the United States every year. The procedure is often required after a patient suffers from an infection, an implant malfunction (loosening or instability) or loss of bone. DePuy offers a variety of implant systems to address the medical needs of patients with failed knee implants.
|DePuy Knee Revision Products:|
|LPS Limb Preservation System (Knee)||PFC Sigma Revision Knee System|
|LCS Complete Revision Knee System||S-ROM Noiles Rotating Hinge Knee System|
TruMatch Personalized Solutions
DePuy created TruMatch Personalized Solutions to help surgeons accurately place knee implants and complete the procedure more efficiently. It includes a custom set of surgical instruments and a computer software system that allows them to customize the procedure according to the patient’s specific anatomy.
TruMatch is only available with fixed bearing knee models. It works by using a 3D scan of the legs to make guides that improve the surgeon’s ability to position and align the knee implants.
TruMatch Works in Four Steps:
- Step 1: Doctors take a CT scan of the patient’s leg
- Step 2: That image is sent to DePuy Orthopaedics, where a special team reviews the image and develops a 3D model of the patient’s knee
- Step 3: DePuy creates personalized guides for the surgery that are customized to fit the shape of the patient’s knee
- Step 4: The guides are sent to the surgeon performing the knee surgery, who uses them to help position and place the new knee implant
According to DePuy, positioning and alignment that is off by as little as three degrees can lead to uneven wear and possible malfunctioning in a knee replacement. TruMark Personalized Solutions uses a personalized approach to surgery that improves the placement, performance and longevity of prosthetic knees.
In August 2010, the FDA issued a warning letter to DePuy because the company broke federal regulations by marketing TruMatch without proper approval. However, one year later the FDA cleared TruMatch as safe through the 510(k) submission process.
DePuy Knee Complications and Product Recalls
In January 2012, DePuy Orthopaedics voluntarily pulled a number of its custom devices from the market, including components from the PFC Sigma Knee Systems product line.
The FDA warned DePuy that it had failed to seek FDA approval for commercial sales on these items:
- PFC Sigma Knee System with titanium components
- PFC Sigma Knee System components, sizes 2.5, 7 and 8
- PFC Sigma Knee System 30mm – 40mm thick inserts
- Femoral heads that include a 14/16 taper
- Femoral heads with offsets greater than +12
Gaining FDA approval is a crucial step for manufacturers because, ideally, it ensures the safety of the devices when implanted in patients. In DePuy’s product information, the company warns that knee replacement performance can vary depending on the patient’s age, weight and level of activity.
With any knee arthroplasty, there is the possibility of certain side effects, including:
- Change in the position of the components
- Implant loosening
- Bending, cracking, fracture or wear of one or more components
- Decreased range of motion
- Leg lengthening or shortening
- Fracturing of the femur or tibia
- Tibial subsidence (implant sinks into softer bone tissue within the tibia)
High flex knee implants remain controversial, with numerous studies reporting unsatisfactory improvements in range of motion and a higher risk for complications like implant loosening. Several reports describe complications with DePuy’s Sigma knee.
As a tradeoff to accommodate a greater range of motion, the DePuy PFC Sigma RP-F knee has design features that require more bone loss during knee surgery. One study comparing the clinical outcomes of patients fitted with the Sigma knee and the LCS Complete knee explains that these Sigma design features result in excessive wear, joint problems, knee instability and significant bone loss if revision surgery is required.
In another study evaluating the results of 77 patients given one or more PFC Sigma knees, researchers observed some complications after an average follow-up of about 12 years. Radiographic imaging revealed minor non-progressive bone loss in 10 out of 25 knees observed. Two revision surgeries were required after 10 years, one for instability and another for polyethylene wear.
Class I Recall for LPS Diapyseal Sleeve
In February 2013, the FDA issued DePuy an Urgent Medical Device Recall informing hospitals and surgeons to stop using and distributing a component called the LPS Diaphyseal Sleeve. The sleeve component, part of DePuy’s LPS Limb Preservation System, allows surgeons to correct defects in the knee’s soft tissue and bones.
The FDA alert revealed that the Diaphyseal Sleeve may not be able to support the stress patients place on the device during normal activities like walking. This can result in fractures or infections in the knee and bones that could lead to loss of function in the limb, loss of the limb itself, soft tissue damage or death.
The FDA says it received several reports of patients suffering from fractures and device loosening with the Diaphyseal Sleeve. The component in question was manufactured between 2008 and July 2012.