Mineralization in a Critical Size Bone-Gap in Sheep Tibia Improved by a Chitosan-Calcium Phosphate-Based Composite as...

Bone regeneration remains a challenge in orthopedic surgery, particularly for large defects that do not heal spontaneously. Prior research has shown that injectable biomaterials can support tissue repair, but long-term mineralization outcomes remain unclear. This gap motivated the development of new composite materials to enhance bone healing. No prior work had resolved the comparative effectiveness of deacetylated chitin derivatives in this context. Researchers have proposed that these materials may influence bone formation through their structural and biochemical properties. However, the mechanisms by which they affect tissue regeneration are not fully understood. Existing products have demonstrated some efficacy, but their limitations in promoting mineralization are well documented. This uncertainty drives the need for alternative injectable composites that can improve healing outcomes. The study addresses this need by evaluating a new chitosan-calcium phosphate composite in a large animal model.

The aim of this study was to assess the bone regeneration potential of a chitosan-calcium phosphate-based composite in a critical size defect. Researchers compared BoneReg-Inject™ with an existing product, chronOS Inject®. The specific problem addressed was the lack of long-term data on injectable composites for large bone defects. The motivation for this comparison was to determine whether the new product could improve mineralization. The study focused on a sheep tibial model, which mimics human bone healing processes. By using a 12-week and 13-month live phase, the researchers aimed to capture both short- and long-term effects. The primary outcome was the amount of new bone formation within the implant. The secondary outcomes included the presence of cartilage and fibrous tissue. This study provides insights into the comparative efficacy of injectable bone grafts.

The study used a bilateral sheep tibial model with critical size drill holes. Holes of 8 mm diameter and 30 mm length were created in the proximal tibia. BoneReg-Inject™ and chronOS Inject® were injected into the right and left holes, respectively. X-ray micro-CT was used to assess bone formation and resorption in vivo. Histological evaluation provided additional insights into tissue composition. The 12-week live phase allowed for initial healing assessment. A 13-month follow-up evaluated long-term mineralization. The study design ensured that each animal served as its own control. Data were analyzed for differences in new bone, cartilage, and fibrous tissue. The methods enabled a direct comparison of the two injectable products. The use of a large animal model increases the relevance of findings to human applications.

BoneReg-Inject™ produced significantly more new bone within the implant than chronOS Inject® (p < 0.001). Cartilage tissue was more pronounced in BoneReg-Inject™ samples (p = 0.003). Fibrous tissue was less prominent in the new product (p < 0.001). These findings suggest a more favorable healing environment with BoneReg-Inject™. Mineral content increased significantly at 13 months postoperative (p < 0.001 for the implant core). The rim of the implant also showed increased mineralization (p < 0.05). These results indicate sustained bone regeneration over time. The data support the hypothesis that deacetylated chitin derivatives enhance mineralization. The 13-month follow-up provides strong evidence for long-term efficacy. The study demonstrates that the new composite outperforms the predicate device in key metrics.

The study demonstrates that BoneReg-Inject™ promotes greater bone formation than chronOS Inject® in a critical size defect. The authors propose that the chitosan-calcium phosphate composite supports a more favorable healing environment. The presence of cartilage tissue suggests an endochondral ossification pathway. The reduction in fibrous tissue indicates better integration with host bone. The increase in mineral content over 13 months supports long-term efficacy. These findings suggest that the new composite may be a viable alternative to existing products. The study does not claim that BoneReg-Inject™ is the only effective treatment. The results are specific to the sheep tibial model used. The data support the potential of deacetylated chitin derivatives in bone regeneration. The authors do not suggest broader clinical applications beyond the study’s scope.