Zimmer M/L Taper & Kinectiv Hip Implants

Maine Hip Implant Failure Lawyer

Recent studies and adverse event reporting indicates that a growing number of patients implanted with M/L Taper and Kinectiv hip components manufactured by Zimmer, Inc. are suffering early failure of their devices due to taper corrosion and fretting.

When fretting and corrosion damage occurs, cobalt and chromium ions wear off the metal components. The metal debris and corrosion byproducts are deposited in the hip joint and can enter a patient’s blood system. Tissue and bone surrounding the hip implant is damaged causing pseudotumors, adverse tissue reaction, significant pain, difficulty walking, loosening of the components, and the need for revision surgery.

Total Hip Replacement

Hip replacement surgery traditionally consists of several stages. First, the orthopedic surgeon removes the top of the femur or thighbone. Next, the orthopedic surgeon hollows out a portion of the top of the femur and inserts a metal femoral stem into the remaining femur bone. The surgeon then uses a hammer to strike a femoral head or ball typically made of a metal alloy onto the top end of the femoral stem. Next, the surgeon reams out the patient’s hip socket and inserts a metal acetabular cup in the resulting space. In some hip implant systems, a metal, plastic or ceramic liner is then fitted inside the acetabular cup. Finally, the surgeon fits the ball-shaped femoral head into the liner of the acetabular cup where it should move easily, without friction or pain to the patient.

The Zimmer M/L Taper & Kinectiv Components

Both the M/L Taper and Kinectiv are titanium alloy femoral stems. At the top end of each stem is a 12/14 trunnion or tapered angle which is slightly wider in its proximal than distal diameter. A corresponding taper angle which is wider in its distal than proximal diameter is located within the bore (the hollow portion of the inside of the ball). When the two components are affixed together during surgery, the trunnion of the femoral stem compresses the walls within the bore allowing for an interference fit or “cold weld” between the two components. The contact area between the inside of the bore of the femoral head (the female taper) and the trunnion of the femoral stem (the male taper) is called the taper interface.

Hundreds of thousands of M/L Taper and Kinectiv femoral stems were implanted in patients around the United States. Both femoral stems were most commonly implanted with the Versys femoral head which is made of cobalt-chrome. When the Versys femoral head is used, the juncture between the M/L Taper or Kinectiv femoral stem and the Versys femoral head is metal-on-metal or more precisely titanium-on-cobalt/chrome.

Why Are M/L Taper & Kinectiv Hip Implants Failing?

In designing the M/L Taper and Kinectiv components, Zimmer knew that the use of dissimilar metal alloys as well as taper angle mismatch, trunnion surface finish, and flexural rigidity contribute to causing fretting and corrosion at the femoral head-femoral stem taper interface.

Although the taper interface is designed to prevent movement of the femoral stem within the femoral head when assembled, micromotion can develop over time at a malfunctioning taper interface. When micromotion occurs, metallic debris rubs off and the passivation layer between the components is worn down. Joint fluid then enters the taper interface leading to corrosion of the underlying metal.

Additionally, the trunnions of the M/L Taper and Kinectiv stems contain microgrooves which look like microscopic screw threads or the ridges of a vinyl record. The microgrooves were added to the trunnions to meet manufacturing requirements for when the stems are used with ceramic femoral heads. The microgrooves channel fluid into the taper interface and create a crevice-like environment which facilitates a corrosion process releasing metal ions, particularly cobalt and/or chromium, off the components.

A recent epidemiological study determined that the M/L Taper femoral stem had a greater prevalence (4.9%) of mechanically assisted crevice corrosion than all other Zimmer femoral stem types employing a 12/14 trunnion combined. Additionally, the study found that patients undergoing total hip arthroplasty between 2009 and 2012 with metal-on-polyethylene hip devices manufactured by Zimmer, Inc. also had a significantly higher prevalence of mechanically assisted crevice corrosion. Hussey, et al., Ten-Year Cross-Sectional Study of Mechanically Assisted Crevice Corrosion in 1352 Consecutive Patients With Metal-on-Polyethylene Total Hip Arthroplasty, The Journal of Arthroplasty (March 18, 2017).

Injuries Associated with M/L Taper & Kinectiv Hip Implants

A well-functioning hip implant should not cause metallosis to a patient in which it is implanted. Increasing reports show that a malfunctioning juncture between dissimilar metal components may be susceptible to failure resulting in tissue damage and other significant health complications, including:

Cobalt and Chromium Toxicity: The poisonous buildup of cobalt and chromium ions in the hip tissue and bloodstream.
Pseudotumor: Soft tissue growths that occur when metal debris causes severe inflammation to the hip tissue.
Revision Surgery: A corrective procedure where failed components are exchanged for new components typically made from different materials.
Osteolysis: The degradation of bone due to metal debris deposition in the hip joint.
Pain & Suffering

If you underwent hip replacement surgery utilizing a M/L Taper or Kinectiv femoral stem, and now have elevated cobalt levels in your blood or abnormal MRI findings, or have had to undergo a revision surgery to remove the original components, you may be entitled to substantial compensation for your injuries.

Maine Hip Implant Lawsuit

If you or someone you love has suffered complications from a M/L Taper or Kinectiv hip implant or another hip device, you may be entitled to significant compensation for your injuries.

To speak with an experienced, Maine hip implant lawyer, contact Fitzgerald Law Group at (844) FITZ-LAW or (844) 348-9529, or complete the contact form on this website for a free, confidential, case assessment.