Since last year, Medtronic Inc. has suffered some declines in their stocks related to concerns regarding their Infuse Bone Graft System.

Medtronic Inc. is the maker of the Infuse Bone Graft System, a device designed to help perform spinal fusion surgery. In spinal fusions, surgeons join together two of the bones of the spine to help strengthen them when their spinal discs fail.

Part of the Infuse Bone Graft System is a bioengineered gel designed to encourage the bones to grow together. In older spinal fusion surgeries, surgeons had to harvest bone from elsewhere in the patients body to fuse the bones together, but the Infuse Bone Graft System was designed to get around this problem by using the bioengineered gel instead of redundant bone. However, there have been concerns related to the device’s safety, damaging Medtronic’s stock value.

Several allegations have surfaced regarding the safety of the Infuse Bone Graft System. There have been inconclusive studies related to cancer risks associated with Infuse, and Medtronic is looking into further study on this front. However, the bulk of the alleged problems with Infuse stem from alleged off-label usage and bone overgrowth.

Several studies have suggested that the Infuse Bone Graft System can cause uncontrolled bone growth in the spine. Since the spine is rich in nerves, muscle attachment points, and other sensitive tissue, uncontrolled bone growth could invade healthy tissue and cause serious harm. Damage to nerves can produce symptoms like tingling, numbness, pain, and even paralysis.

Allegedly, some of Medtronic’s actions may have compounded the issue. The various Infuse lawsuits filed against Medtronic have alleged that the company embarked on a clandestine campaign of off-label marketing. This means that the company hired doctors and medical researchers to promote the device—while not acknowledging the fact that they were on Medtronic’s payroll.

The various articles and conferences allegedly published and promoted uses for the Infuse Bone Graft System beyond the device’s U.S. Food and Drug Administration (FDA) approval. Under U.S. law, a doctor can use a medical device like the Infuse Bone Graft System for a purpose other than the ones approved by the FDA, but it is illegal for the device’s manufacturer to actively promote this kind of use. It is at the very least ethically questionable, and possibly illegal to promote this use on the behalf of such a company for money without declaring the conflict of interest.

According to a 2013 report by Bloomberg News, concerns over the safety of the Infuse Bone Graft System has impacted Medtronic’s stock. Additionally, the thousands of lawsuits facing Medtronic over the Infuse Bone Graft System has further exacerbated the decline in their stock value as the company deals with the legal action of their medical implant.