Guided bone tissue regeneration using a hollow calcium phosphate based implant in a critical size rabbit radius defect

Mellgren Torbjörn,Trbakovic Amela,Ekman Stina,Jensen-Waern Marianne,Öhman-Mägi Caroline,Hammarström Johansson Petra,Ley Cecilia,Hedenqvist Patricia,Thor Andreas

doi:10.1088/1748-605x/abde6f

Abstract

Long bone fractures are common and sometimes difficult to treat. Autologous bone (AB), bovine bone and calcium phosphates are used to stimulate bone growth with varying results. In the present study, a calcium phosphate cement (CPC) that previously showed promising grafting capabilities was evaluated for the first time in a long bone defect. A radius defect of 20 mm was created in 20 rabbits. The defect was filled by either a hollow CPC implant that had been manufactured as a replica of a rabbit radius through indirect 3D printing, or by particulate AB as control. Defect filling and bone formation was evaluated after 12 weeks by combining micro computed tomography (μCT) and scoring of 3D images, together with histomorphometry and histology. The μCT and histomorphometric evaluations showed a similar amount of filling of the defect (combining graft and bone) between the CPC and AB group, but the scoring of 3D images showed that the filling in the CPC group was significantly larger. Histologically the AB graft could not be distinguished from the new bone. The AB treated defects were found to be composed of more bone than the CPC group, including reorganised cancellous and cortical bone. Both the CPC and AB material was associated with new bone formation, also in the middle of the defect, which could result in closing of the otherwise critically sized gap. This study shows the potential for an indirectly 3D printed implant in guided bone regeneration in critically sized long bone defects.

Highlights

There are conditions in which the body’s own bonegenerating abilities are insufficient to heal a fracture or to fill a bone void
In a recent study, using a sinus lift model in rabbits, the same calcium phosphate cement (CPC) formulation was evaluated in a granular form with promising results of bone formation [13]
It would be of interest to investigate if this CPC formulation could be used for bridging of critical size defects in long bones

Summary

Introduction

There are conditions in which the body’s own bonegenerating abilities are insufficient to heal a fracture or to fill a bone void. The complication rate of long bone fractures together with the high incidence of complications puts urgency on developing better treatments. All calcium phosphate materials do not behave in the same manner, and large efforts have been carried out to optimize properties such as phase composition, substitute ions, porosity, drug delivery and implant design [8,9,10]. In a recent study, using a sinus lift model in rabbits, the same calcium phosphate cement (CPC) formulation was evaluated in a granular form with promising results of bone formation [13]. The other losses were unrelated to the animal model; one rabbit died before the study start (endotoxemia) and one during anesthesia before onset of surgery (cardiac arrest).

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Conclusion