[Experimental implantation of hydrogel into bone]

Area of Science:

• Biomaterials Science
• Orthopedic Surgery
• Tissue Engineering

Background:

• Developing bone substitutes with maximal resemblance and compatibility to natural bone tissue remains a challenge.
• Hydrophilic gels (hydrogels) are explored as potential bone tissue substitutes due to their tunable properties.

Purpose of the Study:

• To evaluate the application possibilities and biocompatibility of insoluble hydrogels as bone substitutes.
• To assess the behavior of hydrogels in both spongious and compact bone environments.
• To investigate the influence of porosity and chemical modification on hydrogel integration with bone tissue.

Main Methods:

• Poly(hydroxyethyl methacrylate) (polyHEMA) hydrogels with varying monomer:water ratios were synthesized to achieve different porosities.
• Macroporous, sintered HEMA hydrogels with modified surfaces were created to achieve 'double porosity'.
• Implants were surgically placed in rabbit femurs, followed by macroscopic, histological, and radiographic evaluation at intervals up to 6 months.

Main Results:

• Hydrogel biocompatibility increased with higher porosity; non-porous and microporous hydrogels showed poor compatibility.
• Sintered macroporous hydrogels were surrounded by a thin fibrin membrane, indicating high compatibility.
• Addition of methacrylate acid to hydrogels enhanced macrophage adhesion and led to polymer degradation, particularly in spongious bone.

Conclusions:

• Macroporous hydrogels, especially sintered variants, are biocompatible bone substitutes.
• Porosity is a critical factor influencing hydrogel integration and host response.
• Chemical modification (e.g., adding methacrylate acid) affects degradation rates and inflammatory responses, with vascularization playing a role in degradation.