Method

Fourty healthy rnu/rnu rats were randomly assigned to four treatment groups: (i) untreated control, (ii) BP only, (iii) PDT only and (iv) PDT following BP. BP treatments were administered on day 0 via subcutaneous injection of zoledronic acid. PDT was administered on day 7 via an intravenous injection of BPD-MA photosensitizer. A flat-cut optical fiber was inserted percutaneously adjacent to lumbar vertebra L2. After a 15-minute drug-light interval, 75J of light energy was delivered from a 690nm laser. Six weeks later, animals were euthanized. Structural properties of excised L2 vertebral bodies were quantified through semi-automated analysis of micro-CT images. In of the specimens, mechanical properties were evaluated by loading the L2 vertebral body to failure in axial compression. The remaining L2 vertebrae were analyzed for morphology, osteoid formation and osteoclast activity using histological methods.

Method

Intervertebral disc (IVD) degeneration was enzymatically induced in L2-L3 and L4-L5 lumbar levels in 10 Yorkshire boars using chondroitinase ABC (n=20 discs). An additional three animals served as healthy controls (n=6 discs). Following a four-week degradation period, the TMHA/EP solution (250microL in a 3:1 weight ratio) was injected into the degenerate NP of 16 discs by one of two MIS techniques: A direct 18G needle injection or a modified kyphoplasty technique (MKT) in which a balloon angiocatheter was inserted through an 11G trocar into the IVD and inflated to create a cavitary defect that was then filled with the hydrogel. Excised motion segments were tested in axial compression under a load of 400N and in axial rotation (AR), lateral bending (LB) and flexion/extension (FE) at 5Nm. Range of motion (ROM), neutral zone (NZ) length, NZ stiffness (NZStiff) and axial compressive stiffness (ACStiff) were quantified.

Method

Mixed spinal metastases were developed via intra-cardiac injection of canine Ace-1 luciferase transfected prostate cancer cells in a 3 week old rnu/rnu rat. Two sequential MR images of the L1-L3 vertebral motion segments were acquired using a 1H quadrature customized birdcage coil at 60 m isotropic voxel size followed by CT imaging at a 14m isotropic voxel size. The first MR image was T1 weighted to highlight the trabecular structure to ensure accurate registration with the CT image. The second MR image was T2 weighted to optimize differentiation between bone marrow and osteolytic tumour tissue. Samples were then processed for undecalcified histology and stained with Goldners Trichrome to identify mineralized bone and unmineralized new bone formation.

All images were resampled to 34.9 m and manually aligned to a global axis. This was followed by an affine registration using a Quasi Newton optimizer and a Normalized Mutual Information metric to ensure accurate registration. The whole individual vertebrae and their trabecular centrums were then segmented from the CT images using an extended version of a previously developed atlas based registration algorithm. An intensity-based thresholding method was used to segment the regions corresponding to osteoblastic tumor predominantly attached to the outside of the cortical shell. The whole vertebral segmentation from the CT was warped around the T2 weighted MR to define the bone boundaries. An intensity-based thresholding approach was then applied to the T2 weighted MR segment the osteolytic tumor.

Method

The location of the PF and T were digitized under direct visualization with a three-dimensional scribe on ten, fresh-frozen cadaveric right femora (two male, eight female) by three fellowship trained orthopaedic surgeons. To estimate inter- and intraobserver reliability of the direct measurements, an intraclass correlation coefficient was calculated with a minimum of two weeks between measurements. Under navigation, each specimen was draped and antero-posterior (AP) and lateral radiographs of the proximal femur were taken with a c-arm and image intensifier. The c-arm was positioned in a neutral position (0 for AP, 90 for lateral) and rotated in 5 increments, yielding a range of acceptable images. Images, in increments of 5, within the AP range (with a neutral lateral) were loaded into a navigation system (Stryker, MI). A single surgeon digitized the T and PF directly based on conventional fluoroscopy, and again directed by navigation, yielding two measurements per entry point per specimen. This was repeated for the lateral range. Hierarchical linear modelling and a Wilcox rank test were used to determine differences in accuracy and precision, respectively, in the identification of PF and T using computer navigation vs. conventional fluoroscopy.

Method

Femoral head surfaces were created bilaterally for thirty patients through semi-automatic segmentation of reconstructed CT data and used to map bone density, by shrinking them into the subchondral bone and averaging the grey values (linearly related to bone density) within five millimeters of the articular surface. Density maps were then oriented with the center of the head at the origin, the femoral mechanical axis (FMA) aligned with the vertical, and the posterior condylar axis (PCA) aligned with the horizontal. Twelve regions were created by dividing the density maps into three concentric rings at increments of thirty degrees from the horizontal, then splitting into four quadrants along the anterior-posterior and medial-lateral axes. Average bone density within each region was then calculated using histogram analysis. All analysis was performed with AmriaDEV 5.2.2 image analysis software (Visage Imaging, Carlsbad USA).