Polyethylene Fractures Prompt Stryker Ankle Replacement Warning

Published on November 18, 2019 by Laurie Villanueva

Patients who’ve received a STAR Ankle Replacement System should be alert for signs of polyethylene fracture, following a recent warning from Stryker.

About the STAR Ankle Replacement System

The STAR Ankle Replacement System was developed by a prominent surgeon in Sweden, and is the first and only three-piece mobile bearing ankle implant approved for use in the United States.

STAR Ankle Replacements consist of three components:

  • Talar Component: Covers up the talus or lower bone of the ankle joint.
  • Tibial Plate: Covers up the bottom of the tibia (shinbone).
  • Mobile Bearing: Made from a medical-grade plastic called polyethylene, the bearing is designed to move in between the metal parts as the patient moves their ankle.

The total ankle replacement system was initially marketed by Small Bone Innovations, which was acquired by Stryker in 2014.

STAR Ankle Replacements and Polyethylene Fractures

In a letter to sent to doctors last month, Stryker warned that certain STAR Ankle Replacements were associated with a higher than expected rate of polyethylene fracture.

“This Safety Communication is based on identifying a13.79% polyethylene fracture rate at the eight-year follow-up in the STAR Total Ankle Replacement Post-Approval Study (PAS) for the device, and over 100 polyethylene fractures reported in the FDA (Medical Device Reporting) MDR database, both of which occurred substantially more often than comparable total ankle replacement and with fixed bearing total ankle replacements,” the October 11th letter stated.

The high fracture rate may be due to polyethylene oxidation, either before or after implantation, or implant geometry. Additional contributing factors may also include component malalignment, surgeon learning curve, and reduced insert thickness.

The issue affects STAR Ankle Replacement Systems distributed before August 2014. Because these components had a shelf-life of five years, they could have been implanted as recently as July 2019.

STAR Ankle Replacement Fractures: Symptoms and Monitoring

A STAR Ankle Replacement polyethylene fracture could lead to:

  • Significant pain that’s newly developed and/or persistent over a long period of time.
  • Inflammatory response, newly developed and/or persistent over a long period of time.
  • Blistering and other soft tissue injuries
  • Loss of mobility in the affected ankle.
  • Possible damage to the ankle’s metal components, resulting in revision surgery to replace the entire STAR ankle system

Patients who underwent STAR Ankle Replacement surgery in July 2019 or earlier should inform their doctor if they experience.

  • Inability to bear weight on the affected ankle.
  • Onset of grinding or other noises in the operated ankle.
  • Worsening instability in the replaced ankle.

However, because symptoms of a polyethylene fracture are often subtle and can go unnoticed, doctors are advised closely monitor these patients as well. Those experiencing problems should undergo a detailed examination, including x-rays, to determine if all components are working as designed. However, CAT scans and other specialized imaging studies may be needed to determine if the polyethylene bearing has fractured.

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