Evaluation of Surgical Technique and Clinical Results of a Procedure-Specific Fixation Method for Tibial Tuberosity Transposition in Dogs: 37 Cases.

OBJECTIVE: The aim of this study was to describe the use of a procedure-specific fixation method for tibial tuberosity transposition and report clinical outcome. STUDY DESIGN: This is a multi-institutional case series, evaluating 37 cases that were treated surgically for medial patellar luxation (MPL) and in which the tibial tuberosity transposition (TTT) was performed using the Rapid Luxation Plating System (RLPS). Surgical technique, implants, clinical outcome, and complications are reported. RESULTS: Surgery was successfully performed in dogs weighing 2.5 to 36.2 kg. Postoperative minor complications occurred in 13 cases (35%) and major complications occurred in 3 cases (8%). No implant-related complications or tibial tuberosity avulsions or fractures were seen. Outcome related to surgery was good or excellent in all cases. CONCLUSION: The RLPS for TTT provides a feasible technique in a large range of patients with MPL and lowers the occurrence of implant-related complications and tibial tuberosity avulsion or fracture.

Gene expression profiling of early intervertebral disc degeneration reveals a down-regulation of canonical Wnt signaling and caveolin-1 expression: implications for development of regenerative strategies.

INTRODUCTION: Early degeneration of the intervertebral disc (IVD) involves a change in cellular differentiation from notochordal cells (NCs) in the nucleus pulposus (NP) to chondrocyte-like cells (CLCs). The purpose of this study was to investigate the gene expression profiles involved in this process using NP tissue from non-chondrodystrophic and chondrodystrophic dogs, a species with naturally occurring IVD degeneration. METHODS: Dual channel DNA microarrays were used to compare 1) healthy NP tissue containing only NCs (NC-rich), 2) NP tissue with a mixed population of NCs and CLCs (Mixed), and 3) NP tissue containing solely CLCs (CLC-rich) in both non-chondrodystrophic and chondrodystrophic dogs. Based on previous reports and the findings of the microarray analyses, canonical Wnt signaling was further evaluated using qPCR of relevant Wnt target genes. We hypothesized that caveolin-1, a regulator of Wnt signaling that showed significant changes in gene expression in the microarray analyses, played a significant role in early IVD degeneration. Caveolin-1 expression was investigated in IVD tissue sections and in cultured NCs. To investigate the significance of Caveolin-1 in IVD health and degeneration, the NP of 3-month-old Caveolin-1 knock-out mice was histopathologically evaluated and compared with the NP of wild-type mice of the same age. RESULTS: Early IVD degeneration involved significant changes in numerous pathways, including Wnt/ß-catenin signaling. With regard to Wnt/ß-catenin signaling, axin2 gene expression was significantly higher in chondrodystrophic dogs compared with non-chondrodystrophic dogs. IVD degeneration involved significant down-regulation of axin2 gene expression. IVD degeneration involved significant down-regulation in Caveolin-1 gene and protein expression. NCs showed abundant caveolin-1 expression in vivo and in vitro, whereas CLCs did not. The NP of wild-type mice was rich in viable NCs, whereas the NP of Caveolin-1 knock-out mice contained chondroid-like matrix with mainly apoptotic, small, rounded cells. CONCLUSIONS: Early IVD degeneration involves down-regulation of canonical Wnt signaling and Caveolin-1 expression, which appears to be essential to the physiology and preservation of NCs. Therefore, Caveolin-1 may be regarded an exciting target for developing strategies for IVD regeneration.

Design, synthesis, imaging, and biomechanics of a softness-gradient hydrogel nucleus pulposus prosthesis in a canine lumbar spine model.

A hydrogel nucleus pulposus prosthesis (NPP) was designed to swell in situ, have intrinsic radiopacity, and restore intervertebral disc height and biomechanical functionality. These features were examined using an ex vivo canine lumbar model. Nine NPPs were implanted in five spines and their visibility was assessed on radiography, computed tomography (CT), and magnetic resonance imaging (MRI). The NPPs were visible on all imaging modalities and 8/9 NPPs stayed intact and in situ. Six other NPPs were tested biomechanically in six canine lumbar spines. Removal of the nucleus pulposus (nuclectomy) caused significant changes in biomechanical parameters. After implantation and swelling of the NPP, values were not significantly different from the native state for range of motion (ROM) of flexion-extension (FE) and lateral bending (LB), the neutral zone (NZ) of all motion directions, and the NZ stiffness (NZS) of FE. Biomechanical restoration by the NPP compared with the nuclectomized state was significant for the ROM of FE and axial rotation, the NZ of FE and LB, and the NZS of FE and LB. Disc height was significantly restored and 6/6 NPPs stayed intact and in situ. In conclusion, the NPPs swell in situ, have intrinsic radiopacity and restored disc height and aforementioned biomechanical properties.