Embodiments of a surgical access system useful for single or limited port procedures comprise a trocar comprising a fixation cannula, a retractor, and a gel cap removably coupled to the retractor. The gel cap comprises a gel pad that acts as an artificial body wall, through which instruments may be inserted into a body cavity, either directly or through one or more trocars. The fixation cannula comprises a retainer and a bolster, which together, capture the artificial body wall therebetween, thereby fixing the trocar thereto. The gel pad permits flexible instrument placement, as well as translational and angular degrees of freedom for the instruments while maintaining a gas tight seal.