The second-order nonlinear polarization properties of fibrillar collagen in various rat tissues (vertebrae, tibia, tail tendon, dermis, and cornea) are investigated with polarization-dependent second-harmonic generation (P-SHG) microscopy. Three parameters are extracted: the second-order susceptibility ratio, R = [Formula: see text] ; a measure of the fibril distribution asymmetry, |A|; and the weighted-average fibril orientation, <δ>. A hierarchical organizational model of fibrillar collagen is developed to interpret the second-harmonic generation polarization properties. Highlights of the model include: collagen type (e.g., type-I, type-II), fibril internal structure (e.g., straight, constant-tilt), and fibril architecture (e.g., parallel fibers, intertwined, lamellae). Quantifiable differences in internal structure and architecture of the fibrils are observed. Occurrence histograms of R and |A| distinguished parallel from nonparallel fibril distributions. Parallel distributions possessed low parameter values and variability, whereas nonparallel distributions displayed an increase in values and variability. From the P-SHG parameters of vertebrae tissue, a three-dimensional reconstruction of lamellae of intervertebral disk is presented.

While it is well known that the presence of lymphocytes and cytokines are important for fracture healing, the exact role of the various cytokines expressed by cells of the immune system on osteoblast biology remains unclear. To study the role of inflammatory cytokines in fracture repair, we studied tibial bone healing in wild-type and Rag1 −/− mice. Histological analysis, µCT stereology, biomechanical testing, calcein staining and quantitative RNA gene expression studies were performed on healing tibial fractures. These data provide support for Rag1 −/− mice as a model of impaired fracture healing compared to wild-type. Moreover, the pro-inflammatory cytokine, IL-17F, was found to be a key mediator in the cellular response of the immune system in osteogenesis. In vitro studies showed that IL-17F alone stimulated osteoblast maturation. We propose a model in which the Th17 subset of T-lymphocytes produces IL-17F to stimulate bone healing. This is a pivotal link in advancing our current understanding of the molecular and cellular basis of fracture healing, which in turn may aid in optimizing fracture management and in the treatment of impaired bone healing.

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Breast cancer patients commonly develop metastases in the spine, which compromises its mechanical stability and can lead to skeletal related events. The current clinical standard of treatment includes the administration of systemic bisphosphonates (BP) to reduce metastatically induced bone destruction. However, response to BPs can vary both within and between patients, which motivates the need for additional treatment options for spinal metastasis. Photodynamic therapy (PDT) has been shown to be effective at treating metastatic lesions secondary to breast cancer in an athymic rat model, and is proposed as a treatment for spinal metastasis. The objective of this study was to determine the effect of PDT, alone or in combination with previously administered systemic BPs, on the structural and mechanical integrity of both healthy and metastatically involved vertebrae. Human breast carcinoma cells (MT-1) were inoculated into athymic rats (day 0). At 14 days, a single PDT treatment was administered, with and without previous BP treatment at day 7. In addition to causing tumor necrosis in metastatically involved vertebrae, PDT significantly reduced bone loss, resulting in strengthening of the vertebrae compared to untreated controls. Combined treatment with BP + PDT further enhanced bone architecture and strength in both metastatically involved and healthy bone. Overall, the ability of PDT to both ablate malignant tissue and improve the structural integrity of vertebral bone motivates its consideration as a local minimally invasive treatment for spinal metastasis secondary to breast cancer.

Object. The goal of this study was to quantify volumetrically cement fill and leakage in patients with osteoporotic and metastatic vertebral lesions undergoing percutaneous vertebroplasty and to establish whether these factors have any clinical significance at follow up.Methods. Digital computerized tomography data were retrospectively collected from all cases at the authors' institution in which percutaneous vertebroplasty was performed for osteoporosis or metastatic disease. Patient selection was based on the consensus of a multidisciplinary team consisting of an orthopedic surgeon, an oncologist, and a neuroradiologist. A semiautomated thresholding technique was used to measure vertebral body volume, the volume of cement injected directly into the vertebra, and the volume of cement leakage. Pain-related scores were collected at four early stages of treatment, and all clinical complications were recorded.Cement leakage was found in 87.9% of vertebrae treated with percutaneous vertebroplasty. In osteoporotic vertebrae it occurred mainly in the disc, whereas in metastatic lesions, it was found in multiple areas. Irrespective of leakage, both patients with osteoporotic and metastatic disease experienced significant immediate pain relief postoperatively.Conclusions. Although there was no correlation between cement fill or cement leakage and pain relief, there exists a risk of serious complications due to cement leakage. KEY WORDS • cement • vertebroplasty • osteoporosis • metastasis • spine • painP J. Neurosurg: Spine / Volume 99 / July, 2003 Abbreviations used in this paper: CT = computerized tomography; VB = vertebral body.

This proof of concept study demonstrates the technical feasibility of a smartwatch device and supervised machine learning approach to more easily monitor and assess the at-home adherence of shoulder physiotherapy exercise protocols.

VCF is an important adverse effect following SBRT. Risk factors have been identified to guide the selection of high-risk patients. Evidence-based algorithms with respect to patient selection and intervention are needed.

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