Using allogeneic cortical graft preserved in glycerin as spacer in the advancement of tibial tuberosity in 34 dogs

ABSTRACT: Cranial cruciate ligament is the main responsible for knee stability by preventing cranial tibial displacement regarding the femur. Deficiency in this ligament (CCLD) may cause subluxation of the tibia and dysfunction of the pelvic member due to overloading. Tibial osteotomies are among the more current surgical techniques for treating CCLD in dogs and they proportionate the dynamic stability by means of modifying bone geometry and the distribution of forces acting on the articulation. The objective of this work is to describe the use of the allogeneic cortical bone graft conserved in glycerin as a spacer on the tibial tuberosity advancement (TTA) for treating the CCLD. In order to do that, 34 dogs submitted to TTA surgery correction were evaluated, being 23 males (67.35%) and 11 females (32.35%). Surgical procedures happened from May 2011 to October 2015. Regarding the surgical procedure after osteotomy of the tibial tuberosity, a disk of allogeneic cortical disk, sawn wedge-hapsed, conserved in glycerin, proportions of 2x1mm was applied as spacer, enabling TTA. Advancements from 3 to 12 mm were executed, depending on the need of the patient. For animals with patella dislocation, trochleoplasty and TTA were executed in order to correct the deviation. The mean ± SD age of animals was 6.67±3.58 and weight was 15.16±12.97 kg. Mongrel dogs, Poodles and Yorkshire terriers were the most affected ones. From the 36 evaluated knees, 11 (30.56%) were associated with some traumatic process and in 25 (69.44%) there was no relation with previous trauma. From those wounds, 20 (55.56%) happened in the right limb and 16 (44.44%) in the left limb and two animals had CCLD bilaterally. Animals had continuous support, discreet drawer movement and negative tibial compression 15 days after surgery. At 30 days, 26 cases (72.22%) had firm support (FS); at 45 days, 24 cases (66 test at 7 and 67%) had FS and eight cases (22.22%) without claudication (WC). During subsequent radiographic evaluations the progressive incorporation of the graft and osteotomy union were observed. In this study, most of the diagnosed CCLD occurred in males diverging from results obtained by other authors that found greater frequency in females. Support without claudication it was observed in most of the cases of implants at 60 days. We concluded that the conserved allogeneic cortical bone graft was able to promote bone union in TTA of dogs with CCLD. None of the animals had signs of contamination, infection of the surgical wound or rejection related with the presence of the graft, demonstrated by the complete graft-bone incorporation observed early at 45 days in some animals. The glycerin was a good conservation medium for those fragments intended for grafting because, besides being of low cost, it kept bone fragments free of contamination, reducing antigenicity and preserving the functions of osteoinduction and osteoconduction. The possibility of molding the graft to the animal need is a characteristic favorable to executing the modified technique that could be molded according to the size of the animal, allowing perfect adaptation to the osteotomized local in different breeds. Intercurrences commonly observed in TTA with patellar dislocation, meniscal lesions, tibial crest fracture and displacement were not found in the animals of this study, probably due to the better distribution of forces between the pass screw in TT and the TTA plate confirming that it has good adaptation to the technique conferring to the modified TTA advantages regarding the conventional TTA.