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Promising preliminary results using injectable hydrogels for nucleus replacement
Researchers cite no complications, expect more nucleus pulposus replacement trials to begin soon.
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Discectomy often leads to instability. To overcome that critical problem, researchers are now looking to use injectable solutions as nucleus replacements with the hope of decreasing pain and preventing future herniations.
Investigators conducting early trials using hydrogels as full or partial nucleus replacements say the materials show promise. Douglas Wardlaw, FRCS, the lead investigator of the BioDisc Nucleus Pulposus Replacement (CryoLife Inc.) study, told Orthopedics Today that initial data on the polymerizing protein hydrogel revealed good results and no device-related complications at 6-month follow-up.
“The results up to that point were very good and we’re hopeful that this is going to progress to a useful treatment as an addition to acute disc herniation with the thought that it would reduce recurrent herniation and minimize or reduce the incidence of long-term back pain due to secondary loss of disc height and degenerative disc disease,” he said.
Earlier results also pointed to decreased pain and increased function. In a poster presented at this year’s Britspine meeting, Wardlaw and colleagues found preoperative visual analog pain scores for patients dropped 4.23 points at three months postop. Oswestry scores also showed a mean decrease of 41.56 points (P=.012) during the same period. The study included nine patients with mild to moderate disc narrowing with a mean age of 44. Participants underwent a standard discectomy and received hydrogel injections in the L4-5 or L5-S1 disc levels.
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Image: CryoLife Inc. |
Once injected, the BioDisc treatment bonds with tissue inside the disc. The material fills the space created by removal of the nuclear material which is larger than the hole of the annulotomy, reducing the chance of leakage. Wardlaw expects to present further follow-up data on the study next year.
Researchers conducting preliminary studies using NuCore (Spine Wave Inc.), a synthetic recombinant protein hydrogel, also cite promising results. “We’ve not have any complications or safety issues,” Scott H. Kitchel, MD, the principle investigator for the investigational device exemption (IDE) pilot study, told Orthopedics Today. “We’ve been able to inject a volume of the NuCore approximately equivalent to the amount of the nucleus that was removed and the patients, clinically, are doing quite well.”
The safety study will include 10 patients undergoing lumbar microdiscectomy for acute disc herniation. Researchers will follow patients for a minimum of 2 years and expect to gather 10-year follow-up data. “The outcomes measures that are being looked at are the usual ones of pain and clinical outcomes in terms of the patient disability and activity, but then we’ll also be looking at the maintenance of disc height,” Kitchel said.
Surgeons involved in the U.S.-study arm of the research have performed three procedures using the material, which transforms from an injectable liquid into a gel. They have not had any cases of extrusion, Kitchel said. “There’s a couple of points to speak to that,” he said. “One is that the NuCore material both chemically and physically binds and bonds to the annulus itself, so it tends to prevent extrusion and, the second is that, there is a seal that is put in at the time of the injection to prevent the injection from extruding or going beyond the confines of the disc itself.” Kitchel anticipates that the hydrogel will reach the U.S. market in four years.
Although researchers are beginning to explore the benefits of hydrogels, Wardlaw said that these materials could make a substantial impact in disc care. “I think there is potential for this type of replacement in the future,” he said. “At the moment I see this particular material [BioDisc] as a partial replacement because it’s not aimed in this treatment situation to replace the whole nucleus. But I’m in no doubt that there is a big future for nucleus replacements.”
Kitchel agreed that there is a continued interest in nucleus replacement and expects more trials involving these products. “There are at least six different projects that are currently in the stages of being evaluated or starting their Food and Drug sanctioned trials, so I think it’s still a promising area because it allows an earlier treatment of this degenerative process and perhaps can avoid or at least delay the need for the much more invasive and much more disabling surgeries of either disc replacement or fusion,” Kitchel said.
For more information:
- Orthopedics Today was unable to determine whether Dr. Wardlaw has a direct financial interest in the products discussed in this article or if he is a paid consultant for any companies mentioned.
- Singhal V, MacEachern CF, Craig NJA, et al. Early clinical results of an in situ polymerizing protein hydrogel nuclear repair system. Poster presented at Britspine 2006. April 26-28, 2006. Cardiff, Wales.