Abstract
BACKGROUND CONTEXT
Metals from spinal implants are released into surrounding tissues by various mechanisms.
Metal ion release has been associated with clinical implant failure, osteolysis, and
remote site accumulation with adverse events. Significant corrosion and associated
metal ion release has been described with currently used spinal implant alloys. A
novel metal alloy, Molybdenum-47.5Rhenium alloy (MoRe®), was approved for use in medical
implants in 2019 by the FDA.
PURPOSE
To evaluate the metal ion release profile of MoRe alloy after immersion in both a
stable physiologic, as well as in an inflammatory environment.
STUDY DESIGN
In vitro study.
METHODS
The ion release profile of the MoRe alloy was comprehensively evaluated in-vitro after
prolonged immersion in physiologic and inflammatory environments. Ion concentration
analyses were then conducted using inductively coupled plasma-mass spectrometry (ICP-MS)
methods. Comparative testing of titanium (Ti-6Al-4V) and cobalt chromium (Co-28Cr-6Mo)
was also performed.
RESULTS
Under baseline physiologic conditions, the MoRe alloy demonstrates very low molybdenum
and rhenium ion release rates throughout the 30-day test period. During the first
time interval (day 0–1), low levels of molybdenum and rhenium ions are detected (<0.3
μg/cm2 day) followed by a rapid reduction in the ion release rates to <0.05 μg/cm2 day during the second time interval (days 1–3) followed by a further reduction to
very low steady-state rates <0.01 μg/cm2 day during the third time interval (days 3–7), which were maintained through 30 days.
In the inflammatory condition (H2O2 solution), there was a transient increase in the release of molybdenum and rhenium
ions, followed by a return to baseline ion release rates (days 2–4), with a further
reduction to low steady-state rates of ∼0.01 μg/cm2 day (days 4–8). The measured molybdenum and rhenium ion release rates in both steady
state (<0.01 μg/cm2 day), and inflammatory environments (0.01 μg/cm2 day) were far below the established FDA-permitted daily exposure (PDE) of 1,900 μg/cm2 day for molybdenum and 4,400 μg/cm2 day for rhenium. In contrast, titanium and cobalt chromium approached or exceeded
their established PDE values in an inflammatory environment.
CONCLUSIONS
The novel biomaterial MoRe demonstrated a lower metal ion release profile in both
a physiologic and inflammatory environment and was well below the established PDE.
Comparative testing of the cobalt-chromium and titanium alloys found higher levels
of ion release in the inflammatory environment that exceeded the PDE for cobalt and
vanadium.
Keywords
Abbreviations:
MoRe (Molybdenum-47.5Rhenium), ASTM (American Society for Testing and Materials), H2O2 (Hydrogen Peroxide)To read this article in full you will need to make a payment
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Article info
Publication history
Published online: January 24, 2023
Accepted:
January 18,
2023
Received in revised form:
January 2,
2023
Received:
September 21,
2022
Footnotes
FDA device/drug status: approved (EUROPA® Pedicle Screw System with Molybdenum Rhenium [MoRe®] Rods).
Author disclosures: JM: Royalties: MiRus (D); Consulting: MiRus (E). KP: Royalties: K2M (D), Stryker (C), Camber Spine (B); Consulting: Stryker (D), Medtronic/MAZOR (C), Spinal Elements (B), Camber Spine (B); Speaking/Teaching Arrangements: Stryker (B), Medtronic/MAZOR (B), Bioventus/Siemens (B); Trips/Travel: Bioventus (A), Stryker (A), Medtronic (B), Augmedics (B); Board of Directors: Augmedics (0 shares), MiRus (0 shares). KA: Royalties: MiRus (D); Consulting: MiRus (B). MM: Consulting: MiRus (D). JC: Royalties: MiRus (D); Consulting: MiRus (B). RH: Royalties: DePuy (E), Globus (none), SeaSpine (none); Consulting: DePuy (none), Globus (C), Medtronic (C), Allosource (A), SeaSpine (C), PropioVision (B), Orthofix (none); Speaking/Teaching Arrangements: DePuy (none), Globus (none). JB: Nothing to disclose. PC: Nothing to disclosue. IS: Nothing to disclose. PS: Grants: Mirus, LLC (C, Paid directly to institution); Consulting fee or honorarium: Mirus, LLC (C). JY: Nothing to disclose.
The present study was supported by funding from MiRus, LLC.
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