Fabrication of customized implants based on patient bone defect characteristics is required for successful clinical application of bone tissue engineering. Recently a new surgical procedure, tibial tuberosity advancement (TTA), has been used to treat cranial cruciate ligament (CrCL) deficient stifle joints in dogs, which involves an osteotomy and the use of substitutes to restore the bone. However, limitations in the use of non-biodegradable implants have been reported. To overcome these limitations, this study presents the development of a bioceramic customized cage to treat a large domestic dog assigned for TTA treatment. A cage was designed using a suitable topology optimization methodology in order to maximize its permeability whilst maintaining the structural integrity, and was manufactured using low temperature 3D printing and implanted in a dog. The cage material and structure was adequately characterized prior to implantation and the in vivo response was carefully monitored regarding the biological response and patient limb function. The manufacturing process resulted in a cage composed of brushite, monetite and tricalcium phosphate, and a highly permeable porous morphology. An overall porosity of 59.2% was achieved by the combination of a microporosity of approximately 40% and a designed interconnected macropore network with pore sizes of 845 μm. The mechanical properties were in the range of the trabecular bone although limitations in the cage's reliability and capacity to absorb energy were identified. The dog's limb function was completely restored without patient lameness or any adverse complications and also the local biocompatibility and osteoconductivity were improved. Based on these observations it was possible to conclude that the successful design, fabrication and application of a customized cage for a dog CrCL treatment using a modified TTA technique is a promising method for the future fabrication of patient-specific bone implants, although clinical trials are required.

Distraction osteogenesis is a surgical technique widely used in orthopedic surgery for treatment of various pathological skeletal conditions, namely correction of limb-length discrepancies, angular deformity and treatment of distal and severely comminuted fractures, or bone defects through bone transport. The basic principle consists on the gradual distraction of two bone segments, previously submitted to a corticotomy and promptly fixated generally using of circular external skeletal fixation. New bone tissue is generated in the bone gap between the two segments. This review aims to describe the biological fundaments and principles of this technique, the surgical steps performed to attempt distraction osteogenesis, and its possible complications with main focus on its application in companion animals.Bone Grafts 2 latency period will be applied, and (iv) the distraction rate (DR) must be appropriate for the level and type of bone in which osteogenesis is being performed [5].After the separation of both segments, three temporal phases of DO can be defined: latency period, distraction period, and consolidation period [3]. Osteotomy and corticotomyThe DO procedure begins with the transverse section at a diaphyseal or metaphyseal level of the long bone to be elongated. Ilizarov described three methods to create fractures, including osteotomy, corticotomy, and osteoclasis. The osteogenic potential of the osteotomy or corticotomy depends on three main factors: the localization in bone, the type of technique used, and the latency period subsequently applied [6, 7].Regarding the localization, some researchers in the past referred that the bone lengthening should be performed in the middle of the diaphysis of the long bone, and when necessary elongation was obtained, a bone graft from the ilium crest could be applied on the distraction focus to promote its consolidation. Later, Ilizarov recognized the metaphysis as the ideal site for the osteotomy, due to its massive trabecular bone area, rich in collateral vascularization, and higher potential for fracture recovery. Other researchers compared the regenerated bone quality at the diaphysis and metaphysis after DO, while using different latency periods. In the metaphysis, latency periods of 0 and 7 days allowed a greater osteogenesis and a faster remodeling and consolidation, when compared to the diaphysis elongation. A latency period of 14-21 days was associated with a premature consolidation in both regions. Bone mineralization of the newly formed tissue was faster at the metaphysis than at the diaphysis. Curiously, when there was no latency period, the distraction was successful and the consolidation faster. The latency of 7 days did not reveal the risk of premature consolidation; however, the consolidation and bone formation were slower than where there was no latency period. Post mortem torsion and bending test revealed that the bone tissue elongated on the metaphysis was tougher and more resistant. Histologically, the osteogenesis is observed to be based on intra-mem...