Abstract
Introduction
The need for regeneration and repair of bone presents itself in a variety of clinical situations. The current gold standard of treatment is autograft harvested from the iliac crest or local bone. Inherent disadvantages associated with the use of autogenous bone include limited supply, increased operating time and donor site morbidity. This study utilized a challenging model of posterolateral fusion to evaluate the in vivo response of an engineered collagen carrier combined with nano-structured hydroxyapatite (NanOss Bioactive 3D, Pioneer Surgical) compared to a collagen porous beta-tricalcium phosphate bone void filler (Vitoss BA, Orthovita).
Materials and Methods
A single level posterolateral fusion was performed in 72 adult rabbits at 6, 12 and 26 weeks (8 per group per time point). Group 1: nanOss Bioactive 3D + bone marrow aspirate (BMA) + autograft, Group 2: Vitoss BA + BMA and Group 3: Autograft + BMA were compared were compared using radiographic (X-ray and Micro-computed tomography (μCT), biomechanics (manual palpation and tensile testing at 12 and 26 weeks) and histology.
Results
Radiographic grading and μCT demonstrated progressive increases in radiopacity at the transverse processes and at the middle of the developing fusion for Groups 1 and 3. New bone formation was noted for Group 2 only at the transverse processes (not in the middle of the fusion site).
In this challenging model, manual palpation revealed comparable fusion rates in Groups 1 and 3 (43% and 38%, respectively). None of the animals from Group 2 were fused by manual palpation. Group 3 outperformed Group 2 (P<0.05) while the results were similar to Group 1. Histology on the transverse processes at 6, 12, and 26 weeks demonstrated an osteoconductive response with woven bone formation and subsequent remodeling for all groups. Histology in the middle of the fusion mass (between the transverse processes) also demonstrated an osteoconductive response with remodeling and the development of marrow spaces in the Groups 1 and 3 at 6, 12, and 26 weeks. Bone formation in the middle of the fusion was negligible at 6, 12 and 26 weeks for Group 2.
Discussion
Posterolateral fusion models represent an extremely challenging biological site to evaluate bone graft materials and provide insight into clinical performance. Group 1 (nanOss Bioactive 3D + Autograft + BMA) performed well in the current model providing an osteoconductive scaffold that supported new bone formation on the transverse processes as well as in the middle of the fusion mass and that remodeled with time based on all endpoints. The graft materials had yet to completely resorb by 26 weeks in the current model. Group 2 performed well on the transverse processes in terms of new bone formation however new bone in the middle of the fusion mass was negligible at 6, 12, and 26 weeks. Group 3 (Autograft + BMA) performed well with new bone formation and remodeling on the transverse process and in the middle of the fusion mass as well as is consistently reported with this model.
