9:34 Comparison of impacted femoral ring allografts, threaded cortical bone dowels and titanium cages in lumbar fusion

Abstract

Purpose of study: To test the efficacy of recombinant human bone morphogenic protein (rhBMP-2), we compared clinical and radiographic outcomes in patients who underwent a single-level anterior lumbar interbody fusion (ALIF) and were treated with impacted femoral rings and autogenous bone graft, threaded cortical allograft dowels or titanium cages. Patients who received dowels or titanium cages were randomized to receive either BMP-soaked collagen sponges or autogenous iliac crest bone graft.Methods used: At 22 investigational sites, 387 patients with symptomatic, single-level degenerative lumbar spondylosis that was unresponsive to nonoperative treatment were enrolled in this prospective, randomized, nonblinded study. All patients had a single-level stand-alone ALIF through an open approach. Patients who received dowels or cages were randomized into two groups to receive autogenous iliac crest bone graft or rhBMP-2 on a collagen sponge carrier (InFUSE). All 62 patients who received impacted femoral rings were treated with autogenous bone graft, 46 patients received bone dowels (24 with BMP and 22 with autograft) and 279 patients received the LT-CAGE interbody fusion device (143 with BMP and 136 with autograft). Patients' average age at surgery was 42 years, average weight was 173 pounds and 34% used tobacco products. Clinical outcomes were assessed using the Oswestry Low Back Pain Disability Questionnaire. Anteroposterior, lateral, flexion-extension lateral radiographic views and computed tomography scans, used to evaluate the progression of fusion at 6, 12 and 24 months, were interpreted by two independent, blinded radiologists.of findings: at 24 months, there were no adverse events related to the use of rhBMP-2. At all follow-up visits, all groups showed statistically significant improvements in their Oswestry scores compared with their preoperative scores. Patients in the bone dowel/BMP and LT-CAGE fusion device groups showed greater improvement than the bone dowel/autograft and femoral ring groups. Of patients in the bone dowel/BMP group, 71% showed an improvement of at least 15 points in their Oswestry scores at 3 months after surgery. At all follow-up intervals, the bone dowel/BMP group and both LT-CAGE groups had greater improvements in Oswestry scores than the bone dowel/autograft and femoral ring groups. At 3, 6, 12 and 24 months, the differences in improvement were statistically significant (p=.032, p=.0389, p=.039 and p=.039, respectively). At 24 months, the mean improvement in Oswestry scores was 33.5 points in the bone dowel/BMP group and 29.3 points in the LT-CAGE groups. At 24 months, 84% of the bone dowel/BMP and LT-CAGE patients improved more than 15 points compared with 58% of the bone dowel/autograft and femoral ring groups. At 6 months after surgery, more than 90% of patients in both LT-CAGE groups and the bone dowel/BMP group had evidence of fusion compared with 65% of patients in the bone dowel/autograft group (p=.067) and 10% in the femoral ring group. At 24 months, more than 94% of patients in the two BMP groups had evidence of fusion. The LT-CAGE/autograft fusion rate decreased to 90%, the bone dowel/autograft fusion rate was 68% and the femoral ring fusion rate was 50%.Relationship between findings and existing knowledge: The use of BMP improves clinical outcomes and fusion rates of ALIF over previous standard of care spinal implants.Overall significance of findings: Overall, the groups in which BMP was used showed faster clinical improvement and higher rates of success than the autograft and impacted femoral ring allograft groups. No adverse events related to the use of BMP and the collagen sponge carrier occurred.Disclosures: Devise or Drug: LT-CAGE. Status' approved. Device or Drug: bone dowel. Status: approved. Device or Drug: rhBMP2. Status: approved.Conflict of interest: Kenneth Burkus, consultant for Medtronic Sofamor Danek.