ABM/P-15 Versus Allograft in Non-Instrumented Lumbar Fusion - 10 Year Follow-Up of a Double Blind Randomized Controlled Trial

Study Design: Double blind randomized clinical controlled trial Objective: To compare long-term outcomes and re-operation rates in patients who underwent decompression and non-instrumented fusion for lumbar degenerative spondylolisthesis with either ABM/P-15 or Allograft. Summary of Background Data: Lumbar degenerative spondylolisthesis is a common cause of disability and decreased function in the elderly. In some patients, fusion in combination with decompression is preferred to maintain segmental stability at the decompressed level. The optimal graft material to achieve fusion with minimal complications continues to be debated. Methods: Patients with degenerative spondylolisthesis scheduled for decompression and fusion over one- to two-levels were enrolled in a clinical controlled trial and randomized 1:1 to either ABM/P-15 or Allograft. Patient reported outcome measures (PROMs) and re-operation rates were collected at 1-, 2-, 5- and 10-year follow-up visits. PROMs included the Oswestry Disability Index (ODI), Visual analogue scale (VAS) for back- and leg pain, and EuroQol-5D (EQ-5D-3L). Results: Of 101 patients enrolled, 78 were alive at 10-year follow-up; complete follow-up data was available from 57 (73%) patients, 30 from the ABM/P-15 and 27 from the Allograft group. There were significant improvements in PROMs in both groups from baseline to ten-year follow up. There were no differences in ODI (22.8 vs. 28.5, P =0.337), the primary outcome measure, between the ABM/P-15 and Allograft group at 10-year follow-up. Fifteen patients required re-operations, 4 in the ABM/P-15 and 11 in the Allograft group, which was not statistically significantly different ( P =0.063). Conclusions: There was no difference in PROMs between the ABM/P-15 and Allograft group at 10-year follow up. The incidence of re-operations in the ABM/P-15 group was lower than for the Allograft group, which may be associated with cost savings.