Histological response to cylinders of a low modulus titanium alloy (Ti‐13Nb‐13Zr) and a wear resistant zirconium alloy (Zr‐2.5Nb) implanted in the rabbit tibia

Abstract

AbstractTo assess new and existing materials for total joint arthroplasty, the authors performed a comprehensive histomorphologic and morphometric analysis of bone to cylinders implanted transversely in the proximal tibia of mature New Zealand white rabbits. Four sterile, cylindrical implants measuring 6.1 × 3.8mm were manually inserted through drill holes in both tibiae with a „line‐to‐line fit.”︁ The materials tested included: ASTM F‐75 cast cobalt‐chrome‐molybdenum alloy, commercially pure titanium wrought zirconium‐2.5 niobium alloy, zirconium oxide coated zirconium‐2.5 niobium alloy, wrought titanium‐13 niobium‐13 zirconium alloy, and nitrogen diffusion hardened titanium‐6 aluminum‐4 vanadium alloy. Control animals with or without drill holes were included. The animals were killed by barbiturate overdose 6 months postoperatively. The upper tibiae were harvested and processed for undecalcified histologic sections that were stained with toluidine blue. The sections were examined by an investigator blind to the identity of the implanted materials. A full necropsy was also performed.A collar of lamellar bone, of variable length and thickness, continuous with the original cortex formed a buttress around the implants. There was no evidence of foreign body or inflammatory reaction. The marrow was slightly fatty, but cells of allthree hematopoietic lines were identifiable. The materials investigated had the following ranking in decreasing order of bone contact: Ti‐13Nb‐13Zr > nitrogen hardened Ti‐6Al‐4V > C.P. titanium > Zr 2.5Nb >ZrO2 coated Zr‐2.5Nb > cast CoCr alloy. The difference between the groups was statistically significant (p = 0.05). For the variable „average bone layer thickness”︁ the ranking in decreasing order was: nitrogen hardened Ti‐6Al‐4V alloy = C.P. titanium > Ti‐13Nb‐13Zr > ZrO2/Zr‐2.5Nb > Zr‐2.5Nb > cast CoCr alloy (p = 0.19). For the variable „average bone layer thickness in bone contact regions,”︁ the ranking of the values, in decreasing order were: nitrogen hardened Ti‐6Al‐4V > C.P. titanium > ZrO2 coated Zr‐2.5Nb > Ti‐13Nb‐13Zr >Zr‐2.5 Nb > cast CoCr alloy (p = 0.02). The final necropsy reports of the animals identified no adverse findings that were concentrated to any particular implant group. The new, lower modulus materials Ti‐13Nb‐13Zr and Zr‐2.5 Nb, and nitrogen hardened Ti‐6Al‐4V appear to have a similar or superior bone response to CoCr alloy when implanted in the rabbit tibia model. © 1993 John Wiley & Sons, Inc.