Evaluation of a new formulation of demineralized bone matrix putty in a rabbit posterolateral spinal fusion model

BACKGROUND CONTEXT: Alternatives to autologous bone graft (ABG) with osteoconductive, osteoinductive, and osteogenic potential continue to prove elusive. Demineralized bone matrix (DBM) however, with its osteoconductive and osteoinductive potential remains a viable option to ABG in posterolateral spine fusion. PURPOSE: To compare the efficacy of a new formulation of DBM putty with that of ABG in a rabbit posterolateral spinal fusion model. STUDY DESIGN: Efficacy of a new formulation of DBM was studied in an experimental animal posterolateral spinal fusion model. METHODS: Twenty-four male New Zealand White rabbits underwent bilateral posterolateral spine arthrodesis of the L5-L6 intertransverse processes, using either ABG (control group, n = 12) or DBM (DBM made from rabbit bone) putty (test group, n = 12). The animals were killed 12 weeks after surgery and the lumbar spines were excised. Fusion success was evaluated by manual palpation, high resolution X-rays, microcomputed tomography imaging, biomechanical fourpoint bending tests, and histology. RESULTS: Two animals were lost because of anesthetic related issues. Manual palpation to assess fusion success in the explanted lumbar spines showed no statistical significant difference in successful fusion in 81.8% (9/11) of DBM group and 72.7% (8/11) of ABG group (p = .99). Reliability of these assessments was measured between three independent observers and found near perfect agreement (intraclass correlation cofficient: 0.92 and 0.94, respectively). Fusion using high resolution X-rays was solid in 10 of the DBM group and 9 of the ABG group (p = .59). Biomechanical testing showed no significant difference in stiffness between the control and test groups on flexion, extension, and left lateral and right lateral bends, with p values accounting for .79,.42,.75, and .52, respectively. The bone volume/total volume was greater than 85% in the DBM treated fusion masses. Histologic evaluation revealed endochondral ossification in both groups, but the fusion masses were more mature in the DBM group. CONCLUSIONS: The DBM putty achieved comparable fusion rates to ABG in the rabbit posterolateral spinal fusion model. (C) 2014 Elsevier Inc. All rights reserved.