An injectable calcium sulfate-based bone graft putty using hydroxypropylmethylcellulose as the plasticizer.

Bone graft substitutes are essential in orthopedic and reconstructive surgery for filling defects and promoting new bone growth. Calcium sulfate is a well-known material in this field due to its osteoconductive properties and biodegradability. However, its handling characteristics can be limiting, especially in complex or large defects. Traditional calcium sulfate paste often lacks the consistency needed for uniform filling and injection. This limitation has motivated researchers to explore alternative formulations. Plasticizers have been proposed to improve the workability of synthetic bone grafts. Despite prior studies on calcium sulfate, the long-term effectiveness of a putty form compared to paste remains unclear. The canine model is frequently used in preclinical studies to assess bone repair due to its anatomical and physiological similarities to humans. Yet, few studies have directly compared injectable putty and paste forms of calcium sulfate in large defects. This gap in knowledge highlights the need for a detailed comparative analysis.

This research aimed to evaluate a novel calcium sulfate-based bone graft putty formulation with hydroxypropylmethylcellulose as the plasticizer. The goal was to determine if this putty could match the performance of conventional calcium sulfate paste in repairing large bone defects. The study focused on injectability, handling, and long-term biocompatibility. Researchers sought to assess whether the putty could be uniformly distributed in defects and resorb at a similar rate as the paste. They also wanted to confirm if the putty would support new bone growth comparable to the conventional paste. The canine model was selected for its relevance to human bone repair studies. By comparing radiographic and clinical outcomes over time, the study aimed to validate the putty’s effectiveness in a clinically relevant setting.

The study used a canine model with surgically created large medullary bone defects. Two groups were compared: one implanted with calcium sulfate putty and the other with conventional calcium sulfate paste. Radiographic imaging was performed at regular intervals to track resorption and new bone formation. The plasticizer used in the putty was hydroxypropylmethylcellulose, chosen for its ability to improve workability. The injectability of the putty was assessed based on ease of application and defect filling. Clinical evaluations included monitoring for adverse reactions and healing progress. The area fraction of new bone and remaining implant material was quantified at 13 and 26 weeks post-implantation. Statistical analysis was used to compare the outcomes between the two groups and determine significance.

Both the calcium sulfate putty and paste showed similar progressive resorption and new bone formation in the canine model. Radiographic assessments at 13 and 26 weeks revealed no significant differences in the area fraction of new bone between the groups. The putty demonstrated comparable injectability and defect-filling capabilities to the paste. Hydroxypropylmethylcellulose did not interfere with the resorption rate of calcium sulfate. The putty was found to be biocompatible, with no adverse reactions observed in the study. The new bone formation in putty-treated defects reached similar levels to those treated with conventional paste. The resorption timeline for both materials aligned closely, indicating equivalent degradation rates. These findings suggest the putty is as effective as the paste in promoting bone regeneration.

The study concluded that the calcium sulfate-based putty with hydroxypropylmethylcellulose is as effective as conventional calcium sulfate paste in repairing large bone defects. The putty showed similar resorption rates and new bone formation over 26 weeks. The plasticizer did not hinder the material’s biocompatibility or performance. The putty’s handling characteristics were improved without compromising its osteoconductive properties. The results suggest that the putty could be a viable alternative to traditional paste in clinical settings. The researchers propose that the putty’s injectability and workability make it suitable for complex surgical applications. The study supports further investigation into the putty’s long-term outcomes in human trials. The findings align with the authors’ hypothesis that the putty could match the paste in effectiveness.