426 - Use of OsteoAMP in Lumbar Spine Fusion Results in Higher Fusion Mass a...

#426 Use of OsteoAMP in Lumbar Spine Fusion Results in Higher Fusion Mass and Adjacent Vertebral Body Density as Compared to Autograft and rh-BMP-2

Lumbar Therapies and Outcomes

Poster Presented by: J. Roh

Author(s):

J. Roh (1)
E. Broadaway (2)

(1) Orthopedics International, Kirkland, WA, USA
(2) Radiographer, Huntington Beach, CA, USA

Abstract

Purpose: Spine fusion assessment is often done without taking into account the quality of bone formation or the effect of the bone graft used on the adjacent vertebral bodies. Often, the resulting bone from a supposedly successful fusion is not of high load bearing capacity. In addition, the changes in the adjacent vertebral bodies may have detrimental long term effects on construct integrity. In this study, we analyze a cohort of patients treated with interbody spine fusions for spondylolisthesis and/or stenosis. Computed tomography (CT) imaging was performed to assess quality of bone formation and resulting adjacent vertebral body densities.

Methods: 43 consecutive patients (54 levels) received TLIF or LLIF spine fusions after diagnosis of spondylolisthesis and/or stenosis. Average follow-up time was 310.5 days. Patients were treated with autogenous bone, OsteoAMP® (Advanced Biologics, Ladera Ranch, CA), and/or rhBMP-2 (Infuse®, Medtronic, Memphis, TN) inside the PEEK spine fusion cage. CT was used to monitor progress towards spine fusion. A blinded independent radiographer measured and reported bone density of each of the fusion masses at each level and adjacent vertebral bodies, reporting density in Hounsfield Units (HU). Four 3.1mm2 fusion mass density ROI measurements within the PEEK cage were averaged and reported as fusion mass density. Adjacent vertebral body density was measured in the center of the vertebral body using a 12.6mm2 ROI measurement.

Results: The use of rhBMP-2 in combination with autograft resulted in the lowest density of fusion masses (465.1 ± 191.6 HU) as well as the lowest adjacent vertebral body densities (195.5 ± 63.1 HU). When OsteoAMP® was added to the treatment anterior to the fusion cage as an extender (ie, rhBMP-2 and autograft inside the cage), there was a marked increase in fusion mass density (597.2 ± 135.5 HU) and adjacent vertebral body density (215.8 ± 88.8 HU). When OsteoAMP® was used in the absence of rhBMP-2, the highest density fusion masses and adjacent vertebral body densities were observed (650.7 ± 99.9 HU and 290.5 ± 50.8 HU, respectively). As a reference point, when only autogenous bone was used inside the fusion cage, an intermediate fusion mass density and adjacent vertebral body density was observed (499.7 ± 129.2 HU and 271.8 ± 88.3, respectively).

Conclusion: The use of OsteoAMP® resulted in higher density fusion masses than rhBMP-2 (p< 0.03) or autograft (p< 0.02). Even in the subgroup of patients treated with rhBMP-2 + autograft + OsteoAMP (outside cage), the resulting fusion mass inside the cage was higher than rhBMP-2 + autograft alone (p< 0.05). Perhaps the additional BMPs (aside from just BMP-2) as well as angiogenic and mitogenic growth factors contained within OsteoAMP® aided in the formation of more mature and robust fusion masses. The increased osteogenesis may extend beyond the intervertebral space to provide additional support to the adjacent vertebrae. Future study is needed to determine if the use of OsteoAMP® will be of particular value to help reduce cage subsidence or screw loosening, especially in patients with low bone mineral density.