Surgical Technique-THE T-2 PLATE
Components of the T-Plate Anterior Fixation System are intended for use only with other components of the T-Plate Anterior Fixation System . The T-Plate is designed for an anterior approach to the lumbosacral spine below the bifurcation and is intended to stabilize a degenerated or painful vertebral joint (L5 through S1) in order to promote an arthrodesis.
The patient is positioned supine on a radiolucent operating table such that AP and Lateral fluoroscopic visualization of the L5 -S1 interspace is possible. Lateral fluoroscopy is utilized in planning the anterior incision to assure that the approach is inferior enough to allow visualization of the entire disc space. A standard transperitoneal or retroperitoneal approach is made to the anterior L5-S 1 interspace. The middle sacral artery and vein are controlled and the annulus is exposed as far laterally as the local vasculature will allow.
A complete discectomy is performed back to the posterior annulus. If large osteophytes are present anteriorly, these must be resected. A full posterior release of the disc space will facilitate uniform distraction of the disc space. The distraction device (Figures 1) is then placed into the disc space serially distracting to tension the lateral annular fibers. The distraction device (4200-DT11-17) is modular, allowing uniform distraction of the endplates followed by removal of the outer unit leaving the central distraction wedge centered in the disc space.
If distraction of the spondylolisthesis does not provide passive reduction of the deformity then the T-2 plate is recommended. The distraction wedges are then utilized to tension the lateral and posterior annulus as well as the posterior longitudinal ligament. This maneuver will provide a partial, passive reduction of the spondylolisthesis. The distraction will also address the foraminal stenosis thereby obviating the need for a posterior procedure (Figures 2 and 3).
Figure 2 Figure 3
Once distraction has been obtained the distraction wedges are removed and replaced with the S1 plate guide. The S1 plate guide has a component which provides distraction in the disc space. It has a second component which is a slotted burr guide on the superior/ anterior aspect of S1. With this guide in place a barrel shaped end-cutting burr is utilized to slightly burr the superior/anterior aspect of S1. The burr is then removed and the S1 plate is placed through the slot which functions as a plate holder, onto the superior/anterior aspect of S1. The S1 plate is then affixed to S1 by two screws placed through the plate into the sacral ala (Figure 4). These screw may be placed with the assistance of fluoroscopy and may obtain either unicorticle or bicorticle purchase. In the preferred arrangement they are place bicortically to maximize purchase. The S1 plate has as one of its components two stems which protrude from the S1 plate. The S1 plate guide is then removed leaving the S1 plate affixed to the superior/anterior aspect of S1 with the two stems protruding out from the S1 plate.
Figure 4 Figure 5
The spondy plate is then placed into the disc space, reproducing the disc space distraction, buttressing the inferior/anterior aspect of L5 and engaging its lower two screw holes to the stems of the S1 plate (Figure 5). The bone screws and interference screws are then placed through the spondy plate into the L5 vertebral body affixing the spondy plate to the body of L5. Nuts are then engaged into the threaded stems of the S1 plate. As the nuts are tightened to the stems the spondylolisthesis is reduced by translating the S1 vertebral body to the Spondy plate. Once the nuts are fully tightened the S1 interference screws are placed and the stems of the S1 plate are broken of at pre-stessed levels flush with the reduction nuts (Figure 6).
Figure 6 Figure 7
The position of the spondy plate serves to buttress the S1 screws to prevent back out (Figure 7). A locking plate snaps to the Spondy plate to prevent back out of the interference and bone screws in L5 and S1. Autogenous bone graft or machined femoral allograft is then placed through the plate into the disc space as supplemental interbody fixation.
Removal of the T-2 Plate Anterior Fixation Plate is performed through the same anterior incision with the patient positioned supine on a radiolucent table. A standard transperitoneal or retroperitoneal approach is made to the anterior L5-S 1 interspace. Special care should be utilized in protecting the local vasculature in the setting of a reoperation. The plate is exposed and the Locking Plate Remover (4200-LPR1) is engaged to the locking plate and the locking plate removed. The S-1 nuts are then removed with the nut driver. The screw heads will be exposed and the 3.5 mm hex head screw driver (4200-SD35) is used to remove the screws. The plate holder/remover (4200-PH02) is then engaged to the T-Plate allowing the plate to be removed. The sacral screw are then removed from the S-1 plate and the S-1 plate can then be removed.