Study urges spine surgeons to counsel male patients on risk of infertility with BMP fusion procedure


Spine surgeons should counsel their male patients who are considering a particular spinal fusion procedure about the risk of infertility, say the authors of a new study. The findings are published in the June 2011 issue of The Spine Journal, the international multidisciplinary scientific journal of the North American Spine Society (NASS).

“While we have always known there is a risk of male infertility with some spine surgeries, the risk when performing a spinal fusion with a particular biological bone growth factor appears to be greater than was originally reported in industry-sponsored publications,” said Eugene J Carragee, a professor at the Stanford School of Medicine.


Carragee is division chief of spinal surgery, the lead author of this study and also serves as The Spine Journal’s editor in chief. “In my opinion, it is important that men who are considering having children have the opportunity to weigh the risks of the various available procedures so that they can make their best-informed decision.”


The study, “Retrograde ejaculation after anterior lumbar interbody fusion using rhBMP-2: a cohort controlled study,” offers a retrospective analysis of prospectively gathered outcomes data on consecutive patients having anterior lumbar interbody fusion (ALIF). These procedures were performed with and without the use of rhBMP-2 — a commercially available synthetic bone morphogenetic protein — at a high-volume university practice. When rhBMP-2 was not used, a local bone or iliac crest bone graft from the patient’s own body was used.


After spinal fusion surgery, retrograde ejaculation events were recorded and its incidence was compared. Some men with retrograde ejaculation may become permanently infertile.


The Stanford study found higher incidence of retrograde ejaculation in male patients undergoing one or two-level ALIF surgery with rhBMP-2 (7.2%) when compared with those without rhBMP-2 (0.6%).


In the single-level ALIF surgeries, there was a 6.7% and 0% rate of retrograde ejaculation in the rhBMP-2 versus control groups, respectively. These data closely match the rates found in the Food and Drug Administration (FDA) trial of the rhBMP-2 product and available in the FDA documents.


The Stanford researchers concluded that their study corroborates those previous FDA findings of a higher rate of retrograde ejaculation in ALIF procedures using rhBMP-2 and an anterior spinal fusion approach. Those previous FDA findings have not been widely reported in the medical literature.


In an accompanying commentary on this study in The Spine Journal, James Kang, University of Pittsburgh School of Medicine, USA, wrote that “there is no question that the introduction of rhBMP-2 has added a significant overall cost and is now a major contributor ($4,500 per kit) of the increased dollars spent on spine care…Carragee et al. has now provided further evidence that rhBMP-2 is associated with increased rates of retrograde ejaculation, thereby adding to the growing list of potential complications being reported as a direct consequence for using rhBMP-2.” Kang also concluded, “there is no convincing data that demonstrates it [rhBMP-2] has significantly improved patient-based outcome measures.”


In a second commentary, Tomislav Smoljanovich, and Ivan Bojanic, both from the University Hospital Center, Zagreb, Croatia, noted how closely the Stanford findings matched the FDA data from the original Medtronic-sponsored trials, but was concerned that the industry-sponsored publications did not report the apparent association of this complication with rhBMP-2.


Smoljanovich wrote, regarding previous publications, that the industry-sponsored authors “nonetheless categorically denied any relationship between the rhBMP-2 use and the onset of RE. In our opinion this categorical denial was not credible.”


FDA documents already recognise that the rate of this complication (retrograde ejaculation) is higher in patients receiving this product and those documents clearly state that the rate is higher in patients receiving rhBMP-2. This effect is noted in the FDA labeling of this product but is not widely known in the surgical community.


“The availability of bone graft alternatives such as rhBMP-2 may be of great benefit to certain patients who have serious problems in healing bone,” said Carragee from the Stanford group. “This is an important option in the small group of patients considering spinal fusion who could not otherwise heal their spine. Despite the growing list of complications associated with the product, for these patients an effective alternative the patients own bone may be a life saver.”


The use of rhBMP-2 has been associated with various early inflammatory reactions, including soft-tissue swelling and sterile cyst formation. In the neck, rhBMP-2 use in spinal fusion has been associated in life-threatening complications. In bone, rhBMP-2 may cause early osetolysis and can be associated with infection, implant dislodgement, subsidence and loss of alignment.