Ectopic Bone Formation and the Medtronic Controversy

Ectopic refers to an object or human tissue that forms or is located where it does not belong. Ectopic bone formation is the laying down of new bone material (via a process called ossification) in areas, again, where this material does not belong. This ossification process is performed by cells called osteoblasts.

Doctor showing patient a spine x-ray on a tablet
Cecilie_Arcurs / Getty Images

The word ectopic comes from Ancient Greek, in which it means “away from a place.” Its antonym, which is “orthotopic”—also derived from Greek—refers to bone that is formed in its correct anatomical location, according to an article by Scott et al. entitled “Brief Review of Models of Ectopic Bone Formation" published in 2012 in the journal Stem Cells Development.

Ectopic bone formation can be present at birth, be due to genetics, or arise as a complication of a number of medical conditions, such as paraplegia or traumatic injury. Scott et. al. say that ectopic bone formation is thought to be caused by local inflammation followed by a gathering of skeletal progenitor cells. According to the Boston Children’s Hospital, a progenitor cell is much like a stem cell, except that it is more limited in terms of the types of cells it can become as it divides. Progenitor cells come from stem cells but are not adult stem cells.

Ectopic Bone Formation Due to Spinal Surgery

Scott et al. say that up to 10% of patients who undergo invasive surgery—and back surgery falls into this group—will develop ectopic bone formation.

In the spine, the term "ectopic bone formation" is sometimes used to describe unwanted bone tissue that gets laid down in the spinal canal. In 2002, the FDA approved a bone protein manufactured by Medtronic called Infuse for use in lumbar spine surgery. The use criteria specified by the FDA was very specific: it was approved as a bone graft for single-level anterior lumbar interbody fusion, or ALIF, within the lumbar tapered fusion device system (LT-Cage).

But soon after the approval, many surgeons began to use the material “off-label,” which means for purposes other than what’s been approved by the FDA. Off-label uses included cervical spine surgery that resulted in a number of adverse events being reported to the FDA. Ectopic bone formation was one of the adverse events, but the list included other very serious issues, such as arachnoiditis, increased neurological deficits, retrograde ejaculation, cancer, and more. Not pretty.

Medtronic Controversy

The Milwaukee Journal Sentinal Watchdog Report, which has followed this story, says that within weeks of the first clinical trial for Infuse, ectopic bone formation was found in 70% of the study’s patients. Some of these patients required one or more surgeries to correct the unwanted bone or the medical complications that arose from it.

A review of evidence published in the 2013 issue of Surgery Neurology International compared the 13 industry-fueled studies to other studies subsequently published in journals, as well as to FDA documents and information located in databases. The author reported finding “originally unpublished adverse events and internal inconsistencies” with the Infuse studies. She also noted that 40% of the adverse events were attributable to Infuse being used in ACDF (a type of neck surgery), adding that some of these events were life-threatening.

Meanwhile, the Milwaukee Journal Sentinel reports that Medtronic either under-reported or did not report at all these adverse effects to the FDA in a 2004 study written by Medtronic-funded doctors. MJS says the “doctors who wrote the 2004 paper would go on to receive millions of dollars in royalties and other payments from Medtronic.”

In May of 2014, the Milwaukee Journal Sentinel followed up this story with another saying Medtronic had agreed to pay $22 million to settle 1,000 claims against Infuse. The story mentioned that Medtronic is setting aside another $140 million to cover “expected claims.”

Despite these issues, Infuse has been shown in several studies to be one of the most effective bone fusion products ever created.

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  • Boston Children's Hospital. What are Progenitor Cells? Adult Stem Cells 101 page. Boston Children's Hospital website.

  • Epstein, N. Complications due to the use of BMP/INFUSE in spine surgery: The evidence continues to mount. Surg Neurol Int. 2013.

  • Fauber, J., Infuse cited in patients' painful bone overgrowth. Side Effects. A Journal Sentinel Watchdog Report. Journal Interactive. June 2011.

  • Fauber, J. Medtronic to pay $22 million to settle legal claims over spie product. Watchdog Reports. Milwaukee Wisconsin Journal Sentinel. May 6, 2014.

  • Scott, M., A., Levi, B., ASkarinam, A., Nguyen, A., Rackohn, T., Ting, K., Soo, C., Brief Review of Models of Ectopic Bone Formation. Stem Cells Dev. 2012 Mar 20; 21(5): 655–667.