Updating IFU’s for Stryker’s 3D Tritanium Implant

On November 28, 2018, Stryker Corporation’s Howmedica Osteonics subsidiary issued a Class 2 recall regarding its 3D-printed Tritanium PL lumbar cage.

As part of the recall, Stryker updated the Instructions for Use (IFU) for its 3D-printed cage as follows:

1. “Do not twist, cantilever or rotate to achieve final position. This may result in damage to the implant,” and it included three color illustrations. The original IFU didn’t have a warning that twisting, cantilevering, or rotating the device during insertion could cause problems. Two spine surgeons told us that twisting, cantilevering, and rotating actions are normal procedure when inserting solid titanium cages.
2. The company added two pages with instructions to surgeons regarding sizing the disk space for the implant.
3. The instructions for distraction of the implant space was also changed.
   1. For example, the original IFU said: “Minimal distraction may be required to insert the interbody implant.” (It then goes on to list tools used for distraction but has no warnings.) The updated IFU now says: “Effective distraction aids in removal of the superior articular process, decompression of the neuroforamen, preparation of the disc space and insertion of the Tritanium PL Cage.”
   2. Furthermore, in a highlighted callout, the updated IFU says: “Note: Always assess the need for distraction, even if minimal, to evaluate the disc space.” And, “Particularly in patients with less than ideal bone quality, it might be useful to size the interspace with paddle distractors, reamer distractors or trials before locking the distraction down through the pedicle screws. Interspace distraction helps provide a sense of restoration of annular tension and helps to avoid pedicle screw pre-loading (which may cause post-operative loosening).”
   3. Finally, in another callout, the updated IFU says: “Precaution: Do not use the implant as the sole method for distraction, as this may cause damage to the implant.”
4. Stryker also changed the procedure for intra-operative removal if necessary, adding a note saying that distraction should be done again if already withdrawn, using instruments other than the device itself.

Is This a “Canary in the Coal Mine” Moment?

Are porous 3D-printed (a.k.a. additive-manufactured) implants in general strong enough, and is the Food and Drug Administration (FDA)-required testing sufficient? Do breakage reports signal a larger issue regarding porous 3D implants, or was this situation simply a matter of surgeons not taking steps which weren’t in the original Instructions For Use (IFU) but should have been?

The recall arose because some Tritanium PL cages were fracturing or even crumbling into pieces during implantation and afterward. The recall was not of the device, but solely of the original IFU.

In checking with surgeons who use 3D-printed spinal implants, we were told by one that if a broken piece didn’t impinge on nerves or blood vessels, he’d be inclined to leave it there and let bone grow over it because of the risks of harm to the patient when removing it.