“High Flex” Dr. Han Study Reports High Rate of Zimmer Knee Failure
Many patients who have experienced Zimmer knee problems, up to and including Zimmer knee failure and the need for revision surgery, were recipients of one of Zimmer’s “high flex” artificial knee models, which were designed to offer patients a greater range of motion than standard models used in total knee replacement (TKR). An experienced Zimmer knee lawyer knows, however, that these “high flex” knees often pose the highest risk of Zimmer knee failure.
Zimmer knee failure in flexible implant devices
Zimmer’s “high flexion” roster of artificial knees include the CR Flex, the LPS Flex, the MIS Flex, and the Gender Solutions model, the last of which is specifically designed to accommodate the slightly discrepant joint anatomy of women. High Flexion knees are meant to allow patients to engage in deep knee bending of greater than 120 degrees, and up to a maximum of 155 degrees.
As a comparison, the standard degrees of flexion associated with normal daily activities include: 70 degrees for walking, 90 degrees for climbing stairs, 90 degrees for sitting, and 110 degrees to get up from sitting.
When patients who had received high flexion Zimmer knees began to report Zimmer knee problems such as lack of expected range of motion, excruciating joint pain, immobility, device loosening and revision surgery following total Zimmer knee failure, many clinical studies were launched to discover exactly how common Zimmer knee failure was.
One such study from Korea in 2007 analyzed the post-surgery stability of over 70 NexGen LPS Flex knees. Lead researcher Dr. H.S. Han reported that while flexion was indeed greater in the LPS Flex than in the standard models (a range of 111-165 degrees of in the LPS Flex vs. 110-120 degrees in non-flex devices), there was also a high incidence of Zimmer knee problems such as premature device loosening. Specifically, 38% of the artificial knees showed signs of loosening by 32 months after initial implantation. Over half of these cases required revision surgery by an average time of 2 years after initial surgery.
High flexion Zimmer knee problems
A Zimmer knee lawyer will point out that Zimmer claims that its high flexion knees are meant to last approximately 15 years in patients with active lifestyles.
The Han study states, “Several [physicians] have expressed concern that relatively small gains in maximum knee flexion achieved by making changes in the design may substantially reduce the stability of the prosthesis and increase the stresses on the component.”
Dr. Han additionally concluded that the higher degree of flexion afforded by the LPS Flex was not necessarily due to the design of the knee, but simply attributable to the fact that the knee had loosened.
Patients who received the LPS Flex knee and subsequently experienced less flexion than expected, other disabling Zimmer knee problems, or even total Zimmer knee failure can contact a Zimmer knee lawyer to see if their injuries make them eligible for compensation.