The thoracoscopic technic is a minimal surgical approach that minimizes the skin, muscle and ribs trauma without altering the effectiveness of the treatment.

This type of surgery has been gaining importance due to its advantages: excellent lighting, visualization and magnification. It offers an acute visual control during manipulation and dissection of delicate structures. We aim to assess the anterior release and the thoracic spine arthrodesis through thoracoscopic approach and measure the effectiveness and security of anterior thoracoscopic instrumentation in an experimental study in pigs.

The study was performed on 18 pigs which weighed between 40 and 60 kg. The surgical procedures were conducted at the Hospital Italiano in Buenos Aires. A thoracoscopic surgery was performed as an access to the spine.

The quality of the anterior release ranged significantly from cases in which the incision of the common anterior vertebral ligament could not be finished to cases in which more than 75% of the anterolateral disk circumference was released. In the subjective thoracoscopic assessment of the surgeon the screws were placed successfully in all The radiographic assessment confirmed the surgeon’s presumption, all the screws had been placed correctly. The rod presented complications in several cases.

The radiographic assessment showed that 40.6% (13 patients) of the disc spaces were pseudoarthrosic or with a delayed union. The macroscopic examination confirmed this finding and raised the number of pseudoarthrosic spaces up to 46.8% (15 patients) revealing 4 discs that still had a nucleus pulposus. The data were reinforced by histologic examination.

This histologic cuts were performed using the E & O method. The fibrous ring was clearly identified in the pseudoarthrosic cases as well as the processes of the osteochondral bone formation in its different phases of maturation.

It is very important to highlight that in our experience we had found a direct relationship between the quality of the disectomy, the fusion technique and the experience of the surgeon.

The surgical technique, the rod placement on the screws needs proper positioning and depth. The radiographic and microscopic examination confirmed that the posterior longitudinal ligaments was not damaged.

The thoracoscopic instrumentations in pigs using a rod and screws of third generation is a secure technique. It is essential the development of instrumentation which allows effective thoracoscopic distraction and compression.

We have used a culture system of human peripheral blood mononuclear cells (PBMC)as a source of osteoclast (OC) precursors and murine stromal cells to define the cytokine environment in which human OC form, and to determine the separate contributions of the stromal and haemopoietic elements. We designed a panel of reverse transcription-polymerase chain reaction (RT-PCR) primers that specifically amplify the respective murine or human mRNA species that correspond to cytokines and their receptors previously shown to promote or inhibit OC formation. Murine ST-2 cells and human PBMC were cocultured for up to 21 days in the presence of 1,25(OH) 2vitD3, dexamethasone and human macrophage-colony stimulating factor (M-CSF). OC formation was monitored by the appearance of cells that were positive for tartrate resistant acid phosphatase and able to form resorption lacunae on slices of dentine. We found that the ST-2 cells in these cultures expressed mRNA encoding a repertoire of many of the reported osteoclastogenic factors, as well as the recently described OC differentiation factor (ODF/RANKL). The stromal cells also expressed mRNA encoding osteoprotegerin (OPG), a potent inhibitor of OC formation. We found that agonists and antagonists of OC formation were expressed by both the stromal cells and the PBMC. RANK, the receptor for ODF/RANKL, was expressed only by the PBMC as were IL-1R2 and c-FMS. We identified three features of the cytokine environment that may be a characteristic of normal OC formation. Firstly, the ratio of mouse ODF:OPG mRNA was found to increase during the cocultures, consistent with a key role for ODF in the promotion by stromal cells of OC formation. Secondly, we found that mRNA encoding IL-1 and IL-17, as well as IL-6 and sIL-6R, were coordinately expressed by the PBMC. Thirdly, analysis of the culture medium showed that the PBMC secreted IL-1, IL-6 and TNF-alpha protein only in coculture with ST-2 cells during the first few days of osteoclast development. Similarly, prostaglandin E2, shown to synergise with ODF during OC development, was secreted only in cocultures. Together, these data show OC develop in a complex cytokine environment and suggest that haemopoietic cells provide signals to stromal cells during OC development. Work is in progress to extend these studies to human PBMC interacting with normal human osteoblasts.