- FDA on Monday issued a safety communication alerting patients and providers to a higher-than-expected risk of fracture in the plastic component of the STAR total ankle replacement device recently acquired by Colfax from Stryker.
- The agency said its analysis of post-approval study data and adverse event reports showed fractures occurring as early as three to four years after implant, which was unexpected. Long-term follow-up data showed the plastic component fractured at a rate of 13.8% eight years after implantation.
- Patients younger than 55 or who have osteoarthritis or a more active lifestyle may have a higher risk of the plastic component breaking. The fracture could require surgery to repair or replace the device.
At least 1,841 adverse event reports have been received for the STAR ankle device since 2009, with about 300 of the reports describing fractured plastic components, FDA said. But the agency cautioned that the prevalence of plastic fractures cannot be determined from the reporting system alone.
FDA also reviewed data from the manufacturer on 244 STAR ankle implants that were removed showing 72 plastic component fractures. The breaks were seen more frequently in thinner components, and most of the fractures showed material oxidation degradation after three to four years of implantation.
The agency said the higher-than-expected fracture rate found in the long-term post-approval study may be underestimated because two plastic fractures were not diagnosed until surgery. The "higher fracture rate and earlier than expected occurrence are concerning when compared with other comparable total ankle replacement devices," according to FDA.
The regulator said the fractures may be due to multiple factors, including device design, material, surgical factors, and patient factors such as higher activity levels. In 2014, changes were made to the product's foil packaging to limit material degradation of the plastic component.
Stryker's divestiture of the STAR ankle business to Colfax subsidiary DJO Global was key to the device maker obtaining U.K. regulatory approval for its $4 billion acquisition of Wright Medical. Wright specializes in both upper and lower extremities, which Stryker has characterized as among the fastest-growing segments in orthopaedics. Overlap in the ankle market also was an area of concern for U.S. antitrust regulators.
Stryker in October disclosed it entered into a definitive agreement for the divestiture to Colfax of its STAR total ankle replacement product and related assets, as well as finger joint replacement devices. With regulators' concerns finally addressed, Stryker in November completed the Wright Medical acquisition, first announced one year earlier.
Colfax, an industrial conglomerate that has quickly built up its medtech portfolio through a series of acquisitions including the STAR ankle line, announced last week that it plans to separate its medical device and fabrication technology businesses into two independent public companies. The split is expected to be completed by the first quarter of 2022. The medtech business was projected to generate sales of about $1.4 billion this year.
FDA said the STAR ankle product remains appropriate for some patient populations, such as older patients with lower activity levels. But those with more active lifestyles have a greater-than-expected risk of the plastic component breaking. The risk of device fracture exists for all of the ankle devices regardless of date of manufacture or distribution, the agency said.
Worsening pain, inability to bear weight, a new grinding or other noise, or instability in the ankle are signs the plastic component may be fractured.