Femoral Orthopedic Implants in Dogs with Titanium - Mechanical Evaluation

ABSTRACTBackground: Orthopedic implants are commonly used for different types of surgical procedures to gain optimal function and to provide stability to both bones and tendon structures. When inserting these implants, the characteristics of the material are important for surgical success, and the ideal implant must be biocompatible and nonallergenic. However, when molding an implant to the bone structure, its resistance can change significantly. Implants can be temporary or permanent in the body, and metal possesses properties that make it acceptable for bone repair. In biomedical implants, 2 types are most common, commercially pure (CP)-Ti and Ti-6A1-4V. They both provide stable fixation and low risk of loosening. Implants made with the same material and composition can perform differently if the material has been altered by processing techniques for different scenarios. Stress, strain and elastic modulus are the primary metrics used in the description of implant materials. They can be calculated based on mechanical tests of specimens with defined geometry, most commonly tensile, bending and torsional tests. In order to better evaluate those changes, we compared the mechanical characteristics of titanium bone plates, before and after they were molded to the bone, to verify and quantify the loss of stiffness and resistance after molding the plate.Materials, Methods & Results: The study was prospective. Orthopedic implant made of commercially pure titanium (CP-Ti) were divided into 2 groups, one group without plate molding and the other with plate molding to a dog femora bone. Thirty-six plates of different sizes (5.0, 6.5, 8.0, 9.0, 10.0 and 11.0-mm diameter) were divided into 6 groups containing 6 plates of each size and submitted to the 4-point flexion test of resistance, using a piece of dog femur (weights of 5, 10, 15, 20 and 25 kg) as the bone in which the molding was performed. The evaluations were tabulated and analyzed using the program GraphPad Prism version 5.0. Corrections of the normal distribution curve were made using the Bartlett test. After the corrections, one-way analysis of variance (ANOVA) was performed with P < 0.05. Assessments were made within the group and between groups. Subsequently, the Newman-Keuls test was performed, adopting P < 0.05. For analyses in 2 groups, Student's t-test was performed as a post-test, also with P < 0.05. When the plates were compared between equal sizes of groups 1 and 2, the non-molded plate group (G1) obtained the best results in the flexural stiffness and structural flexion tests. However, in the flexural resistance test, most plates obtained similar results and the plates with diameters of 8 mm, 9 mm and 10 mm of the molded plate group (G2) obtained the best results.Discussion: Our results show that the implants had adequate mechanical characteristics, but the unmolded plates had greater flexural and structural stiffness than the molded plates. This difference was significant, thus demonstrating a large loss of stiffness in relation to the original conformation. However, when we tested the flexural resistance, no significant differences were observed, and although without significant statistical changes, there was an increase in the resistance of the plate with the new conformation obtained by molding. In the results of the mechanical tests, we observed that after the molding, the implants gained greater resistance, although the difference was not statistically significant. This suggests that the architecture of the implants should have slight curvature in the medial direction of the bone, since this would lead to a better adaptation to the anatomy of the bone, and possibly greater resistance, as indicated by the new configuration after molding.Keywords: bone implants, titanium, orthopedic implants, femur, dogs

New Technique for Intrathoracic Implantation of Extraluminal Spiral Prostheses in the Trachea

Background: Extraluminal surgical procedures for intrathoracic tracheal collapse in dogs are not routinely performed. The patients are normally treated with different drugs or by intraluminal stents. However, in more severe cases, drug treatment does not always have good outcomes, and intraluminal prostheses can be correlated to several postoperative problems. In order to obtain better results, we aimed to develop a surgical technique for implantation of a new extraluminal helical prosthesis in the thoracic segment of the trachea through cervical access, associated with pneumatic mediastinoscopy for certification of the technique and minimization of possible complications.Materials, Methods & Results: Seven canine corpses (CCs) from non-traumatic death, weighing between 2 and 7 kg, were used. A ventral cervical approach to the trachea was associated with blunt mediastinal dissection. Trans cervical pneumatic mediastinoscopy was used for evaluation of the dissection and location of the implant. These were compared with the necropsy findings by the exact Wilcoxon two-sample test, with P < 0.05. The results of necropsy and mediastinoscopy did not present significant differences at P < 0.05. During the examinations, the presence of some mediastinal visceral lesions caused by the prosthesis, the integrity of the mediastinum and possible lesions to RLN and blood vessels (BV) were analyzed. We also investigated the location of the distal part of the prosthesis in the thoracic segment of the trachea and its dissection. To evaluate the technique, statistical comparison was made between mediastinoscopy and necropsy findings. The data were compared by the Wilcoxon test at 5% probability. The tracheas of all CCs were efficiently dissected, but in some cases problems that can happen during the procedure were noticed. This was checked by mediastinoscopy and confirmed by necropsy. The median of the scores was 1 (good dissection and visualization), with variance of zero for mediastinoscopy and 0.14 for necropsy. In the mediastinoscopy of one CC, the prosthesis crossed the tracheal bifurcation, involving the posterior vessels of this region, which was confirmed by necropsy. However, the dissection showed no vascular lesions. The integrity of the mediastinum was assessed only by mediastinoscopy. There was no impairment caused by any of the procedures performed. This resulted in a median score of 1 (integrity) with zero variance. When the positioning of the prosthesis was evaluated in relation to the tracheal bifurcation, identical values were obtained by both methods. The median score was 1, with variance of 0.62. No statistical differences were found between the two evaluation methods for the analyzed variables. This demonstrates the strong potential of the proposed evaluation techniques.Discussion: Our results show that the execution of the technique is possible, but some complications may occur. Mediastinoscopy as an evaluation procedure can pose some complications, these considerations are important, but by using technique proposed in this study, these factors are minimized due to the ease of technical implantation of the extraluminal tracheal stent, without the need for several instruments competing in the inflated mediastinal space. We concluded that the technique is viable and a safe method with minimal invasion for investigation and treatment of mediastinal diseases, presenting low impairment of the paratracheal structures, and that mediastinoscopy can be used as a transoperative evaluation method to minimize complications

Femoral Orthopedic Implants in Dogs with Titanium - Mechanical Evaluation

ABSTRACTBackground: Orthopedic implants are commonly used for different types of surgical procedures to gain optimal function and to provide stability to both bones and tendon structures. When inserting these implants, the characteristics of the material are important for surgical success, and the ideal implant must be biocompatible and nonallergenic. However, when molding an implant to the bone structure, its resistance can change significantly. Implants can be temporary or permanent in the body, and metal possesses properties that make it acceptable for bone repair. In biomedical implants, 2 types are most common, commercially pure (CP)-Ti and Ti-6A1-4V. They both provide stable fixation and low risk of loosening. Implants made with the same material and composition can perform differently if the material has been altered by processing techniques for different scenarios. Stress, strain and elastic modulus are the primary metrics used in the description of implant materials. They can be calculated based on mechanical tests of specimens with defined geometry, most commonly tensile, bending and torsional tests. In order to better evaluate those changes, we compared the mechanical characteristics of titanium bone plates, before and after they were molded to the bone, to verify and quantify the loss of stiffness and resistance after molding the plate.Materials, Methods &amp; Results: The study was prospective. Orthopedic implant made of commercially pure titanium (CP-Ti) were divided into 2 groups, one group without plate molding and the other with plate molding to a dog femora bone. Thirty-six plates of different sizes (5.0, 6.5, 8.0, 9.0, 10.0 and 11.0-mm diameter) were divided into 6 groups containing 6 plates of each size and submitted to the 4-point flexion test of resistance, using a piece of dog femur (weights of 5, 10, 15, 20 and 25 kg) as the bone in which the molding was performed. The evaluations were tabulated and analyzed using the program GraphPad Prism version 5.0. Corrections of the normal distribution curve were made using the Bartlett test. After the corrections, one-way analysis of variance (ANOVA) was performed with P &lt; 0.05. Assessments were made within the group and between groups. Subsequently, the Newman-Keuls test was performed, adopting P &lt; 0.05. For analyses in 2 groups, Student's t-test was performed as a post-test, also with P &lt; 0.05. When the plates were compared between equal sizes of groups 1 and 2, the non-molded plate group (G1) obtained the best results in the flexural stiffness and structural flexion tests. However, in the flexural resistance test, most plates obtained similar results and the plates with diameters of 8 mm, 9 mm and 10 mm of the molded plate group (G2) obtained the best results.Discussion: Our results show that the implants had adequate mechanical characteristics, but the unmolded plates had greater flexural and structural stiffness than the molded plates. This difference was significant, thus demonstrating a large loss of stiffness in relation to the original conformation. However, when we tested the flexural resistance, no significant differences were observed, and although without significant statistical changes, there was an increase in the resistance of the plate with the new conformation obtained by molding. In the results of the mechanical tests, we observed that after the molding, the implants gained greater resistance, although the difference was not statistically significant. This suggests that the architecture of the implants should have slight curvature in the medial direction of the bone, since this would lead to a better adaptation to the anatomy of the bone, and possibly greater resistance, as indicated by the new configuration after molding.Keywords: bone implants, titanium, orthopedic implants, femur, dogs