The Midline Approach:
Posterior spine fusion with screw fixation is a common and reliable method of instrumentation of the spine for a variety of spine pathologies when the ultimate aim of surgery is the fixation of the spine to allow bony fusion. The mainstay of this kind of surgery has been the use of pedicle screw fixation. The trajectory of pedicle screws aims to transverse the pedicle down its anatomical axis, with a screw specifically designed for fixation in cancellous bone. More recently, Santoni et al., in 2009 proposed using an alternative trajectory, a cortical bone based fixation technique, which utilizes a different path down the pedicle with the aim of maximizing the contact between screw and cortical bone.
Posterior lumbar spine fusion using the cortical based trajectory has advantages over traditional pedicle screw techniques including reduced dissection and tissue trauma, increased biomechanical stability in both high and low quality bone and is thereby a valid alternative to traditional techniques.¹