Modular Hip Implant Complications Result in ‘Watch’, Call for Further Research

Some orthopedic experts are raising concerns about the potential risks associated with hip replacement systems that feature modular head-neck components. 

The components are designed to be adjusted so that surgeons can account for different limb lengths and other factors, but a “watch” article published in The Journal of Bone and Joint Surgery‘s JBJS Case Connector last week questions how long doctors will see the benefits from head-neck modularity, also referred to as trunnions, and whether the risk of modular hip implant complications is justified.

The concerns come following reports of patients experiencing complete head-neck dissociation anywhere from seven to 14 years after receiving a modular hip implant. A number of these incidents have been detailed in previous JBJS Case Connector articles.

The JBJS Case Connector researchers said there have been enough incidents and questions to identify this type of implant as one that needs to be watched closely by the medical community.

“While this system is not statistically conclusive and may or may not be supported by other published case reports or registry data, the intention is to sharpen the focus of clinicians on the potential for similar problems and thereby enhance clinical outcomes and patient safety,” the researchers wrote. “The ‘Watch’ designation may also encourage others to report related difficulties and enlist the orthopaedic community to either demonstrate that these are isolated, unrelated cases or sharpen the focus further on rigorously evaluating the intervention.”

The article said that they may identify brands, models or implant lots when they deem it appropriate. It also cites a number of advantages to the hip implants, including the ability to adjust version, as well as limb length and offset. They can be used to help increase the functioning and longevity of a hip implant.

Problems with Modular Hip Replacement Systems

Several different specific types of hip replacement systems that involve modular designs have been linked to reports of problems in the past, including the Stryker Rejuvenate, Stryker ABG II and some Wright Profemur designs.

These designs involve modular femoral neck-stems, where two metal pieces are placed inside each other, allowing the femoral component of the hip replacement system to be adjusted.

Problems with the Wright Profemur hip have involved a fracture of the titanium modular neck. As a result, the manufacturer faced a number of product liability lawsuits alleging that design defects made it prone to degrade, fret and ultimately fracture. An updated version of the Wright Profemur modular neck was introduced in 2010, which the manufacturer has suggested in stronger than the titanium version.

In July 2012, a Stryker Rejuvenate and ABG II hip recall was issued after thousands of these modular implants were implanted into patients throughout the U.S. The action was taken after the manufacturer acknowledged that the implant may be prone to catastrophically fail as microscopic metal debris is released from the modular components rubbing together over time.

Following several years of litigation, the manufacturer agreed to pay substantial Stryker Rejuvenate settlements to resolve most cases where individuals required revision surgery after the modular implant failed. However, as individuals continue to experience complications from the recalled modular hip implant, it is expected that the manufacturer will continue to face litigation over the modular design.