Osseointegration of autograft versus osteogenic protein–1 in posterolateral spinal arthrodesis: emphasis on the comparative mechanisms of bone induction

• Published in: The spine journal 2002-01, Vol.2 (1), p.11-24
• Main Authors: Cunningham, Bryan W, Shimamoto, Norimichi, Sefter, John C, Dmitriev, Anton E, Orbegoso, Carlos M, McCarthy, Edward F, Fedder, Ira L, McAfee, Paul C
• Format: Article
• Language: English
• Subjects: Animal model; Animals; Biomechanical Phenomena; Biomechanics; Bone morphogenetic protein; Bone Morphogenetic Protein 7; Bone Morphogenetic Proteins - pharmacology; Bone Transplantation; Decalcification Technique; Dogs; Histology; Models, Animal; Osseointegration; Posterolateral osseointegration; Radiography; Recombinant Proteins - pharmacology; Spine - cytology; Spine - diagnostic imaging; Spine - physiology; Spine - surgery; Transforming Growth Factor beta; Transplantation, Autologous
• ISSN: 1529-9430; 1878-1632
• DOI: 10.1016/S1529-9430(01)00170-X

Background context: Recent studies have documented increased fusion success afforded by bone morphogenetic proteins versus autogenous graft for posterolateral spinal arthrodesis. Purpose: The current study was designed to investigate the time-course maturation processes of lumbar posterolateral arthrodeses performed with Osteogenic Protein–1 (Stryker Biotech, Inc., Hopkinton, MA, USA) (rhOP-1) versus “gold standard” autograft. Study design: The primary focus of this study was to compare the histologic mechanisms of posterolateral osseointegration produced by “hot topic” growth factors. Methods: A total of 36 coonhounds were equally divided into one of four postoperative time periods of 4, 8, 12 and 24 weeks (nine animals per period). Posterolateral arthrodesis treatments included 1) autograft alone, 2) autograft plus rhOP-1, or 3) rhOP-1 alone. The treatments and animals were divided such that a value of n=6 was obtained for each treatment group per time period and no one animal received the same treatment at both operative sites. Functional spinal unit (FSU) fusion status was assessed using radiographic analysis, biomechanical testing and undecalcified histopathologic and histomorphometric analyses. Results: Radiographic differences in fusion maturation between the treatment groups were evident as early as the 4-week time interval and continued through the 24-week time period. The Osteogenic Protein–1 treatments demonstrated an accelerated rate of radiographic fusion by 4 weeks, which plateaued after the 8-week time period (22% autograft, 88% autograft/rhOP-1 and 66% rhOP-1). In contradistinction, the so-called “gold standard” autograft alone treatments reached a maximum of 50% fusion by the 6-month interval. Biomechanical testing of the FSUs indicated lower flexion-extension and axial rotation range of motion levels for both rhOP-1 treatments versus autograft alone at the 8- and 12-week time periods, respectively (p.05), and histopathology indicated no significant histopathologic changes. The most distinctive finding in this study deals with the mechanisms of posterolateral ossification. Based on plain and polarized light microscopy, bone induction and development for the rhOP-1 treatments, with and without autograft, was the result of intramembranous ossification, whereas the process of osseointegration for autograft