![]() Sheep were chosen for this study as they provide a good model regarding bone remodeling as their bones biomechanically share similarities to human bone. These sheep were 3–5 years old and had body weight of 56–87 kg. Twelve skeletally mature female Texas/Gotland breed sheep were purchased from local farmer. We hypothesized that ABM/P-15 graft material had similar or improved fusion rates compared with traditional allograft in an ovine uninstrumented PLF model. As described, this model indicates other challenges when compared to other bone grafting models. This preclinical evaluation is essential prior to using the ABM/P-15 graft for PLF in clinic. The aim of this prospective randomized study was to evaluate early spinal fusion rates using ABM/P-15 bone graft compared with allograft in a two-level uninstrumented PLF model in sheep. To this point, no studies have evaluated ABM/P-15 in a flex formula in a PLF model. ![]() It has gained CE approval in Europe and is used today in humans as i-Factor™. ABM/P-15 has had comparable fusion rates as allograft in an interbody ovine fusion model and in humans. ABM/P-15 induces bone formation comparable to allograft in critical sized defects and implant fixation sheep models and also improves bone formation in rat osteoporotic models. The potential of ABM/P-15 on bone formation has been previously shown in preclinical and clinical studies. The binding of α2β1-integrins to P-15 initiates natural intra- and extracellular signaling pathways and induces production of growth factors, bone morphogenic proteins, and cytokines. Its osteoinduction (P-15) occurs by providing binding site for α2-β1 integrin on the surface of bone forming cells. ABM/P-15 bears osteoconductive and osteoinductive properties its osteoconduction (ABM) occurs by providing a three-dimensional matrix for bone ingrowth and by releasing necessary minerals. This composite material has been proven to stimulate bone formation. P-15 has an identical sequence as found in the cell-binding domain in collagen type-1 (α-chain). ABM/P-15 is a recently investigated composite material, which consists of anorganic bovine-derived hydroxyapatite matrix (ABM) combined with a synthetic 15 amino acid sequence (P-15). New graft materials that resemble today’s gold standard but are without the risks and limitations associated with autograft or allograft are needed, and several composite materials have been investigated. Literature reporting lumbar fusion rates when using autograft or allograft is inconsistent with a range of 40–93%. This is because of the freezing procedure for storage after harvesting. Allograft possesses a conductive property and a partial osteoinductive property but no osteogenic property. Allograft is the most often used surrogate graft material today and is considered a gold standard second only to autograft for lumbar fusion. Because of limited availability in harvesting autograft and patient donor site morbidity such as pain and bleeding, using alternative materials garners high interest. Traditionally, autograft from the iliac crest has been the gold standard, as autograft possesses osteoinductive, osteoconductive, and osteogenic properties. To achieve solid bone formation between vertebral bones, graft materials are used. This is due to lack of external support in fixating graft material and large defect size for novel bone formation. PLF is the most commonly used fusion model and also the most challenging model in regard to novel bone formation and graft properties. In this study, a posterolateral lumbar fusion (PLF) model was used. Many different approaches have been tried, and posterior, anterior, and interbody fusion between vertebral bodies are commonly used. The aim of fusion is to segmentally impair movement and stabilization, and the procedure may be performed with or without instrumentation. Spinal fusion is a procedure where bone graft material is used to facilitate novel bone formation between two adjacent vertebral bones. Between 20, 79% to 86% of total interbody fusions were posterior/transforaminal lumbar fusions this number is estimated to have increased since 2010. Over the last decade, the number of spinal fusion procedures has increased significantly, and in 2008 more than 400,000 fusions were performed annually in the USA. Spinal fusion is a commonly used procedure in spinal surgery worldwide and is indicated in the surgical management of different spinal disorders such as degenerative disorders, pain, tumor, deformity, and trauma.
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