Evaluation of ABM/P-15 versus autogenous bone in an ovine lumbar interbody fusion model

Abstract

A prospective, randomized study was performed in an ovine model to compare the efficacy of an anorganic bovine-derived hydroxyapatite matrix combined with a synthetic 15 amino acid residue (ABM/P-15) in facilitating lumbar interbody fusion when compared with autogenous bone harvested from the iliac crest. P-15 is a biomimetic to the cell-binding site of Type-I collagen for bone-forming cells. When combined with ABM, it creates the necessary scaffold to initiate cell invasion, binding, and subsequent osteogenesis. In this study, six adult ewes underwent anterior-lateral interbody fusion at L3/L4 and L4/L5 using PEEK interbody rings filled with autogenous bone at one level and ABM/P-15 at the other level and no additional instrumentation. Clinical CT scans were obtained at 3 and 6 months; micro-CT scans and histomorphometry analyses were performed after euthanization at 6 months. Clinical CT scan analysis showed that all autograft and ABM/P-15 treated levels had radiographically fused outside of the rings at the 3-month study time point. Although the clinical CT scans of the autograft treatment group showed significantly better fusion within the PEEK rings than ABM/P-15 at 3 months, micro-CT scans, clinical CT scans, and histomorphometric analyses showed there were no statistical differences between the two treatment groups at 6 months. Thus, ABM/P-15 was as successful as autogenous bone graft in producing lumbar spinal fusion in an ovine model, and it should be further evaluated in clinical studies.

Figures

Fig. 1

CT scans of the same level at both time points. Large amount of new bone formation outside of the PEEK rings in both treatments can be seen starting at 3 months post-surgery. All treatments appear to have solid bone formation inside the PEEK rings at 6 months

Fig. 2

The micro-CT images show dense bone matrix within and outside of the PEEK rings of both treatments. The sagittal plane views show bone formation bridging the intervertebral space. The residual ABM/P-15 can be seen in the top images within the PEEK rings as a hyper-opacity

Fig. 3

Histology images showing elaborate, dense bone formation inside of the PEEK rings bridging the intervertebral space and proving successful interbody fusion. The ABM/P-15 treatment on the right also reveals some residual ABM/P-15 within the PEEK ring shown as the green stain