Histomorphometric Assessment of Thoracoscopically Assisted Anterior Release in a Porcine Model

Abstract

A retrospective study using histomorphometric analysis to quantify the percentage of discectomy following thoracoscopic anterior release and fusion in a porcine model. To investigate the safety and completeness of disc and endplate removal with respect to the learning curve of the surgeon in a porcine thoracoscopic anterior fusion model. The thoracoscopic approach has been used to perform an anterior release and fusion before an open posterior instrumentation, however, there is concern that the technique may not provide sufficient visualization or exposure to perform safely and completely. A total of 32 pigs (160 discs) were assigned to 2 groups (early experience, n = 16; late experience, n = 16), and underwent 5 level thoracoscopic anterior release followed by anterior instrumentation and fusion from T5 to T10. At 4 months after surgery, the spines were harvested, and each discectomy disc was histomorphometrically analyzed to determine the percentage of disc excision and amount of endplate removal. There were no significant differences in the percent disc excision between the early (67% +/- 11%) and late groups (69% +/- 10%). Greater than 50% of the disc was excised in 151 of 160 discectomies (94%). Both superior and inferior endplates were resected in 92 of 160 disc levels (57%). The amount of endplate removal had improved over time in both early and late groups (P < 0.0001). The histologic examination revealed no evidence for posterior longitudinal ligament disruption or spinal canal encroachment in any disc. Video-assisted thoracoscopic discectomy is safe and allows for a significant amount of disc material excision. This study did not demonstrate a learning curve with respect to the amount of disc material excised, but a learning curve was seen for endplate excision.