BONE GRAFTING FOR SPINAL FUSION

There is no established small animal approach model for the strict simulation of lateral lumbar interbody fusion (LLIF) surgery.

This study aims to establish a reliable LLIF rabbit model that strictly simulates the procedure and to preliminarily evaluate the differences in fusion outcomes with different graft materials.

A controlled laboratory.

Fifty-four 4-month-old white New Zealand female and male rabbits were selected and divided into five groups: Group A (dissection group) consisted of 9 rabbits, Group B (normal approach group) consisted of 9 rabbits, Group C (autogenous iliac bone group) consisted of 12 rabbits, Group D (BMP-2 carrier material group) consisted of 12 rabbits, and Group E (allograft bone group) consisted of 12 rabbits. Based on data from Group A, a novel titanium metal fusion device was designed. Postoperatively, at the 12-week mark, manual palpation was employed to compare the interbody fusion status among Groups B, C, D, and E. Specimens from Groups C, D, and E were subjected to Micro-CT scanning to compare various parameters such as trabecular bone volume (BV), bone volume fraction (BV/TV, BVF), and bone surface area (BS). Furthermore, a tissue histopathological examination was performed to observe the structure and morphology of newly formed bone within the fusion mass as well as the remodeling of the graft in each group.

Based on the measurements obtained from the dissection group, we designed a U-shaped interbody fusion device with dimensions of 10 mm in length, 2.5 mm in width, and 1.3 mm in height. In Group B, 9 cases exhibited intervertebral mobility. In Group C, 1 case showed non-fusion. In Group D, all cases achieved fusion. In Group E, 4 cases did not achieve fusion. Additionally, the Micro-CT results showed that the interbody fusion index scores were 4.64±0.50 in Group C, 4.33±0.65 in Group D, and 3.36±0.81 in Group E. There was no statistically significant difference in fusion index scores between Groups C and D (p=.853). Notably, Groups C and D had higher scores than Group E (p<.001). The trabecular bone volume (BV) in Groups C and D also showed no significant difference but was significantly higher than in Group E (p<.001). Furthermore, the histopathological results revealed that the specimens from Group E had less newly formed cartilage and bone compared to Groups C and D.

This study successfully established a strict simulation of the clinical LLIF procedure in a rabbit model. Moreso, we conducted a preliminary validation indicating that the BMP-2 carrier material achieved interbody fusion outcomes similar to autogenous iliac bone.

The findings of this investigation from animal models provide a theoretical basis for the clinical use of BMP-2 to promote early spinal fusion in LLIF procedures. Importantly, the study provides a small animal model foundation for research related to LLIF surgery.

Healthy peri-implant tissue with sufficient quality and quantity is among the determining factors of implant success and survival. Accordingly, reconstruction of deficient peri-implant tissues may be an essential treatment prior to implant insertion. Routinely, conventional techniques are implemented to meet this demand however, these techniques are associated with pitfalls such as morbidity in obtaining bone grafts or limited available sources. These limitations have led to use of other potential sources and techniques such as stem cells, growth factors, and scaffolds to further enhance bone regeneration around implants and promote the osseous integration. This chapter aims to review and challenge the conventional approaches applied in this field and will further discuss the novel methods and assumptions incorporated in peri-implant tissue regeneration.

Bone graft substitute mechanical and architectural properties maintain a critical role in cellular mechanotransduction and are fundamental design features regulating the migration, lineage, and growth of mesenchymal progenitors and neovascular networks. It is essential that novel bone graft substitutes are designed, fabricated and administered with rigorous consideration for the complex relationships between construct material properties and the transmission of local mechanobiological cues to the regenerative niche. Remarkably, a consensus in the field on even an approximate range of suitable bone implant mechanical properties has not been reached. Consequently, there is a continuum of graft substitutes under active investigation with elastic moduli encompassing seven orders of magnitude. The purpose of this chapter is to examine the state of biomaterial platforms for the treatment of bone defects and to motivate dialog to define appropriate mechanobiological criteria for future bone graft substitute research and development. First, a brief summary of the physiological process of bone regeneration is outlined. Second, material approaches for bone graft substitutes including FDA device classifications and testing considerations are reviewed. Finally, we review in vitro and in vivo evidence elucidating how bone regeneration is regulated by the mechanical environment across multiple length scales.

Degeneration of the cervical discs is a frequent indication for surgical intervention. Anterior cervical discectomy and fusion has consistently demonstrated clinical success; however, concerns for adjacent segment disease have driven investigators to consider alternatives. Overall, 7 cervical devices have been approved in the United States for disc arthroplasty. The data collected has created a benchmark in spine surgery and has served as a critical assessment of both anterior cervical discectomy and fusion as well as anterior cervical disc arthroplasty. Longitudinal follow-up is beginning to differentiate between the outcomes that may be achieved with arthrodesis in comparison to disc arthroplasty.