Most spinal fusions are held together with metal plates, screws, and bone graft material. During the healing process, the body fills in and around the fusion site with additional, fresh bone. The initial graft material placed at the fusion site during the procedure is usually an autograft.
Autograft means the bone was taken from the patient. The most common place to harvest bone for the graft is from the patient’s pelvic bone. But there are two major drawbacks to this type of autograft. One is the fact that it requires a second surgery. The second is the fact that sometimes the patient’s bone quality isn’t that good.
Bone graft material can be obtained from a bone bank (donated by someone else). Donor graft material comes with its own set of risks and problems. Scientists are actively seeking alternative ways to provide a strong fusion without bone grafting. One of the methods that has been developed over the last few years is the process of using osteogenic proteins. Osteogenic means bone producing. And that’s exactly what these bone proteins do.
But the process is new enough that it’s still unknown whether bone protein works as well or better than autografts or donor bone. In this study, two groups of spinal fusion patients were compared. One group received the standard autograft harvested from the patient’s pelvic bone. The second group had a graft made up of a bone protein called osteogenic protein-1 (OP-1) mixed with bone from the spine that was removed as part of the procedure.
Everyone was followed for a year. The main measure used to test the results was a CT scan assessing the strength of the fusion. Patients were also given a test called the Oswestry Disability Index (ODI) to measure pain, function, and perceived disability. Complications and problems that developed as a direct result of the fusion technique were also compared.
For those who are interested, the authors provided a detailed description of the preparation of the bone graft substitute as well as the surgical technique used during the fusion. For those who want to cut to the chase and find out what the results were, here’s what they discovered.
First of all, it should be said that the characteristics of the patients in the two groups (male vs. female, age, diagnosis) were basically the same. The length of time in surgery and number of days in the hospital were the same between the two groups. There were no statistically significant differences for outcome measures between the two groups. In other words, rate of fusion, pain levels, and ability to perform daily activities were pretty much the same for all the patients.
Adverse events were about the same between the two groups (very minimal). As expected, the autograft patients reported pain along the pelvic crest where the donor bone was harvested. The OP-1 group had no such problems. And that’s the main advantage of using bone growth proteins. OP-1 combined with bone removed from the fusion site was found to be a safe and effective alternative to autograft from the pelvic crest.
The authors make note of the fact that this was a fairly small (pilot) study of only 36 patients. It was the first time autograft from the pelvis was compared directly to using bone growth proteins in a single-level lumbar spine fusion. This group of patients will be followed for the next 10 years to see if the good results last as long as the autograft group.
Future studies are needed to compare the use of autograft vs. bone protein when applied to various levels within the lumbar spine. Larger numbers of patients need to be evaluated in just the same way this first pilot study was done. Getting the same results with a larger number of people in a repeated study is an important part of proving the process is safe and effective.