Table 2.

Current status of bone adhesive materials.

Bone-Adhesive Material			Current Status
Bone adhesives composed of natural polymers	Proteinaceous bone adhesives	Fibrin-glue based bone adhesives	•Well-known in clinical practice. •Mostly limited to fixation of comminuted fractures of non-load bearing bones and osteochondral fractures.
		Gelatin-based bone adhesives	•Gelatin-resorcinol-formaldehyde systems are associated with toxicity and not widely used anymore. •Other relatively recent investigations are still in early phase research.
		Other proteinaceous bone adhesives	•Only a few examples present. •Mostly still in early research phase.
	Polysaccharide-based bone adhesives	Chitosan- based bone adhesives Starch- based bone adhesives Dextran- based bone adhesives	•Chitosan seems to be the most popular choice among polysaccharide-based materials. •Most of the studies focus on measuring adhesive strength. •Only a limited number of preclinical studies have been reported.
Bone adhesives composed of synthetic polymers	Bone adhesives composed of unmodified synthetic polymers	Polyurethanes	•Previous failures of clinical attempts due to complications. •Other relatively recent investigations are still in early phase research. •Concerns related to toxicity.
		Polycyanoacrylates	•Methyl-2-cyanoacrylate and ethyl-2-cyanoacrylate show toxicity. •Preclinical studies indicate metallic plates and screws show superior performance compared to N-butyl-2-cyanoacrylate. •Recent studies on 2-octyl-2-cyanoacrylate reported unfavorable outcomes.
		Polymethyl methacrylates and copolymers	•No specific interaction with bone, only mechanical interlocking. •PMMA itself is not degradable. •Biodegradable PMMA copolymers require elaborate studies regarding biocompatibility and functional performance.
	Bone adhesives composed of chemically modified synthetic polymers	Bone adhesives composed of polymers modified with synthetic bone adhesive groups	•Some studies present high bone adhesion strengths relevant for clinical practice. •There is need for more detailed preclinical and clinical investigations regarding safety and performance.
		Bone adhesives composed of polymers modified with bioinspired animal-derived bone adhesive groups	•Relatively low bone adhesion strengths when compared to conventional synthetic adhesives. •Still in early phase research where most of the studies focus on measuring adhesive strength to bone ex vivo. •Only a limited number of preclinical studies are present, need for elaborate studies to assess safety and performance. •No clinical study yet.
Bone adhesives composed of inorganic cements		Calcium phosphate cements	•Lacks strong adhesion to bone. •Brittle structure. •Calcium phosphate cements modified with phosphoserine show high bone adhesion strength relevant for clinical practice. Present research shows promise, however there is need for more detailed clinical investigations regarding safety and performance.
		Magnesium phosphate cements	•Relatively better features compared to calcium phosphate cements. •Need for elaborate studies regarding safety and performance.
		Glass ionomer cements	•Brittle structure. •Risk of toxicity due to aluminium. Recent trend is development of aluminum-free versions. •Need for elaborate studies regarding toxicity.