Analysis of Bone Healing with a Novel Bone Wax Substitute Compared to Bone Wax in a Porcine Bone Defect Model

Background Bone wax is used in surgery as a hemostatic device for bone. Despite its good functional capacity as a bone hemostat, Bone wax materials often have very poor long-term interactions with bone. This study describes a novel composite of hydroxyapatite (HA) and biodegradable poly-lactic acid (PLA) with wax-like handling properties (OsteoStat). The goal was to compare qualitative and quantitative measures between OsteoStat versus Bone wax. Methods The porcine critical size defect model was chosen in this study. OsteoStat and Bone wax were introduced into separate critical size defects located in the femur and humerus of a single porcine specimen. After a duration of 6 weeks, the defect sites were harvested for clinical, histological, and histomorphometric analysis. Results Both groups had effective hemostatic action when introduced into the defects. Analysis of the histomorphometric data revealed that the amount of new bone was significantly greater at 6 weeks in the OsteoStat group (38.05%) versus the Bone wax group (11.88%), p=0.028. OsteoStat also demonstrated less soft tissue and less test material remaining in the defect sites; however, this was not statistically significant. Conclusions We speculate that the incomplete biodegradation of Bone wax as well as its intrinsic inflammatory properties may have retarded osseous regeneration and promoted fibrosis. In contrast, well known biodegradation pathways for PLA combined with the HA component of OsteoStat may have accounted for the positive results of OsteoStat compared to Bone wax. It is important that bone hemostat substances have biocompatible, osteoconductive, hemostatic, as well as good handling properties.


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Since Bone wax is comprised of paraffin wax and esterified fatty acids, it is highly 67 hydrophobic. This enables Bone wax to serve as a physical barrier against blood, occluding the 68 bleeding channels and achieving hemostasis by a tamponade and blood stasis effect. However, 69 this hydrophobic property in conjunction with limited enzymatic degradation of waxes in the 70 human body prevents appreciable rates of absorption and/or excretion post-surgical application..

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It is well documented that Bone wax impairs optimal bone formation and healing of 72 sternotomies, 3,5 which could be due to, in part, physical inhibition of osteoblast and osteocyte 73 migration to the site of bony injury. Furthermore, the nature of Bone wax which makes it highly 74 resistant to degradation has also been linked with infection, 6,7 although large randomized studies 75 have found the infection link to be inconclusive. 8 Since intraoperative bone bleeding can be 76 heavy, physicians must weigh the benefits of bone hemostasis using Bone wax versus the risk of 77 decreased bone healing and other complications such as infection.

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It is important that Bone wax like substances have biocompatible, osteoconductive, 80 hemostatic, as well as good handling properties. Several alternative materials have been reported 81 in the literature such as PEG/collagen, 9 polyorthoester, 10 fibrin-collagen, 11 chitin-based 82 material, 12 , and gelfoam. 13 However, none of these alternative materials have yet seen 83 widespread adoption, suggesting that a material which meets the effective hemostatic qualities of 84 Bone wax together with good osseous integration and affordability has not been met. bone, and exhibits good osteoconductivity. 14

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A porcine bone defect model was used for this study. One female young adult Landrace pig 104 weighing 52.8 kg was used for this study, with an acclimation period of 7 days. Two groups of 105 holes were drilled into the femur and humerus and filled with either OsteoStat or Bone wax.

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After a period of 6 weeks, qualitative (clinical and histology) and quantitative 107 (histomorphometry) analyses were performed on the drilled sites. The animal was prepared for operation under general anesthesia. Intraperitoneal 110 pentobarbital sodium was administered and the field of operation was then sterilized and selected 111 6 at the right humerus and contralateral left femur. Tissue dissection was performed, exposing the 112 underlying periosteum at these respective sites. Four test sites were chosen for the bone defect, 2 113 holes located in the right diaphyseal humerus and 2 holes located in the left diaphyseal femur.

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All test sites were drilled to have standardized intraosseous defects with a circumference of 3cm     (Fig. 1). In the Bone wax sites, fibrous soft tissue stroma was the predominating 158 component. Some new bone can also be seen, and there is also the presence of undegraded test 159 material. The amount of new bone appears visually less than in the OsteoStat sites (Fig. 2).   (Fig. 3). Bone wax sites show a large amount of fibrous 173 tissue and some new bone is also present, but as immature bony trabeculae (Fig. 4).   trabeculae. Osteocytes are also present in the bony matrix. No osteoclasts are seen (Fig. 5). 185 Similarly, the Bone wax site (Fig. 6) shows osteoblast activity lining the bony trabeculae, with 186 no osteoclasts. The variation in sections at the x400 magnification is inherently greater.   Table 1). The difference in bone area fraction between the OsteoStat group 204 (38.05%) and the Bone wax group (11.88%) was significant (p = 0.028) ( Table 2). The soft 205 tissue area fraction in the OsteoStat group (49.64%) was also less than the Bone wax group 206 10 (72.04%); however, this result was not statistically significant (p = 0.089). Similarly, the amount 207 of test material remaining in the OsteoStat group (12.31%) was less than the Bone wax group 208 (16.08%) and was also not statistically significant (p = 0.421).     properties.