Table 4.

Relevant animal studies of Zn-based biodegradable materials as potential orthopaedic implants.

Zn-Based Metals	Designed Implants	Control	Surgeries	Animal Species	Major Findings	Ref.
Zn-Mn	Scaffold	Pure Ti	Insertion into femoral condyle	Rats	The new bone tissues at the bone defect sites gradually increased with time in both groups, and numerous new bone tissues were observed around the Zn-0.8Mn alloy scaffold	[70]
Zn-1Mg, Zn-1Ca, Zn-1Sr	Intramedullary nails	NA	Insertion into femoral marrow medullary cavity	Mice	There was no inflammation observed around the implantation site and no mouse died after operation. The new bone thickness of Zn-1Mg, Zn-1Ca and Zn-1Sr pin groups are significantly larger than the sham control group.	[51]
Zn-HA	Pin	Pure Zn	Insertion into femoral condyle	Rats	There was new bone formation around the Zn-HA composite, and the bone mass increased over time. With prolonged implantation time, the Zn-HA composite was more effective than pure Zn in promoting new bone formation.	[55]
Zn-0.05Mg	Pin	Pure Zn	Insertion into femoral condyle	Rabbits	No inflammatory cells were found at the fracture site, and new bone tissue formation was confirmed at the bone/implant interface, proving that the Zn-0.05Mg alloy promoted the formation of new bone tissue.	[46]
Zn-(0.001% Mg 2.5%, 0.01% Fe 2.5%)	Screw and plate	PLLA, Ti-based alloys	Mandible fracture	Beagles	The new bone formation in the Zn alloy group and the titanium alloy group was significantly higher than that in the PLLA group. In addition, the new bone formation in the Zn-based alloys group was slightly higher than that in the Ti-based alloys group. The degradation of Zn implants in vivo would not increase the concentration of Zn2+.	[97]
Zn-X (Fe, Cu, Ag, Mg, Ca, Sr, Mn, Li)	Intramedullary nails	Pure Zn	Insertion into femoral marrow medullary cavity	Rats	Pure Zn, Zn-0.4Fe, Zn-0.4Cu and Zn-2.0Ag alloy implants showed localized degradation patterns with local accumulation of products. In contrast, the degradation of Zn-0.8Mg, Zn-0.8Ca, Zn-0.1Sr, Zn-0.4Li and Zn-0.1Mn was more uniform on the macroscopic scale.	[24]
Zn-0.8Sr	Scaffold	Pure Ti	Insertion into femoral condyle	Rats	Zn-based alloys promote bone regeneration by promoting the proliferation and differentiation of MC3T3-E1 cells, upregulating the expression of osteogenesis-related genes and proteins, and stimulating angiogenesis.	[36]
Zn-0.8Li-0.1Ca	Scaffold	Pure Ti	Insertion into radial defect	Rabbits	The Zn-0.8Li-0.1Ca alloy has a similar level of biocompatibility to pure titanium, but it promotes regeneration significantly faster than pure Ti.	[33]
Zn-0.4Li	Screw and plate	Ti-6Al-4V	Femoral shaft fracture	Rabbits	Plates and screws made of Zn-0.4Li alloy showed comparable performance to Ti-6Al-4V in fracture fixation, and the fractured bone healed completely six months after surgery.	[25]
Zn-1Mg-nvol%β-TCP (n = 0, 1)	Columnar samples	Zn-1Mg	Specimens in lateral thighs.	Rats	Zn-1Mg alloy and Zn-1Mg-β-TCP composites had no significant tissue inflammation and showed good biocompatibility.	[56]