Bone Graft as an Adjunctive Treatment for Delayed Union and Non-Union of Fractures in Dogs: Systematic Review.

Abstract
The cases of non-union or delayed union are the main diagnoses related to complications of orthopedic fractures within the veterinary surgery of companion animals, mainly dogs. Bone graft transplantation is a growing competence as an adjuvant treatment in these cases. The study reveals its use through the evaluation of the data obtained in an advanced research on the topic referring to the main scientific databases, resulting in a systematic review, in addition to proving its means of extraction and conservation. Although there is the possibility of performing autograft and xenograft, among other substitute materials, a choice on the part of the veterinarian must make a tiny assessment of each case. However, this therapeutic approach requires greater professional, structural and, consequently, financial investment by veterinarians and hospital doctors. As well as, the realization of scientific works with the objective of contributing to the evolution of this method of associated treatment and bringing more and more benefits to the orthopedic patient.


Abstract
The cases of non-union or delayed union are the main

Introduction
Orthopedic traumas are part of the clinical routine of pets in veterinary medicine, among common for this treatment. However, the intention to reestablish a function of the evolve limb cannot be caused, due to complications, such as delayed union or non-union, mainly in the canine species. That is, when the healing time exceeds the expected bone healing process time [1]. Thus, studies are being followed alternative and adjuvant procedures to obtain greater success from surgical procedures for the treatment of fracture complications in dogs.
Along with surgical fracture reduction, the use of bone grafts as in adjuvant treatment is increasing every year. It is estimated that during 2006 worldwide, the number of bone grafts exceeded 2.2 million [2]. Since, the results obtained are satisfactory and often this is the right bet for cases with a history of several unsuccessful surgical procedures.
The union delay and the non-union bone have a multifactorial cause, but by definition it is considered as the partial of complete cessation of the reparative processes of bone healing [3]. The probable causes cited are: bone instability due to the proposed treatment method and vascular injury, that compromises the healing process [4]. Temporal, clinical and radiological parameters are used to diagnose in define the condition. The American Food and Drug Administration (FDA) defines the condition as "established when a minimum period of nine months has passed since the injury and the fracture shows no visible progressive sign of healing for three months". However, there are marked temporal variations about this parameter in the literature [5,6].
As regarding to the situation of non-union, it is classified in two aspects, viable and non-viable, according to the osteogenic capacity and characteristic of vascular supply [6]. Characterized as viable non-unions, which competes for biologically active fractures with varying degrees of proliferative bone activity, with interposed cartilaginous and fibrous tissue. In addition, they can be subclassified Still, the sum of the clinical, radiographic and temporal discretion provides variations regarding the consensus on diagnostic definition [7].
The bone graft, in addition to being used to treat fractures with non-union or delayed union, is in option as in adjunctive treatment for the correction of bone loss due to neoplastic involvement, arthrodesis and as in inducer of bone filling after removing plates and screws, in which says orthopedic surgery.
Furthermore, due to the versatility of its therapeutic application, it has also been used in veterinary dental procedures [3][4][5][6].
According to the origin, the bone grafts is classified as: Autogenous, a portion of bone tissue extracted from one location and transplanted into another, by the same individual. Homologous, when the transplant is carried out between different individuals of the same species. Or even heterologous, when performed between different animal species [8,9].
The choice of the type of graft to be used must be evaluated on a case-by-case, essential considering material availability, combability, immunogenicity, morbidity and costs. Thus, so-called autografts

Materials and Methods
This systematic review was carried out through a bibliographic survey of original articles, review articles and cases reports obtained from the NCBI, Science Direct, BIREME and Scielo databases. The Keywords used to carry out the research were: Bone grafts, bone non-union, bone union delay, dogs.
The following filters were used as inclusion criterion: Languages: English and Portuguese; Species: dogs; Types of articles: originals, reviews and case reports; Period of publication of articles: 2010 -2020. Articles that contain less than four keywords; Articles published before 2010.
Another refinement was made after Reading and evaluating the abstract of the remaining publications, excluding with did not need the theme based on the criterion already mentioned. Therefore, were left 5 articles consistent with the objective or the review.  The use of external fixators should be evaluated, due to its complications. In cases of delayed union or non-union autologous bone transplantation using a minimally invasive technique has proven effective

Results and Discussion
The bone graft proved to be inefficient through its application along with a minimally invasive surgical procedure [10], since the authors report only the invasive method for bone transplantation. Thus, its application did no correspond with the objective of the work. However, PALMER et al [14]

Conclusion
This article highlights the wide range of valid efficiency alternatives that contribute to the use of bone transplantation in orthopedics within the veterinary medicine of pets. Assigning visibility to methods of obtaining, processing and conservation.
As well as, therapeutic applicability of these methods.