Background: Traditional techniques for the treatment of isthmic spondylolisthesis pass a fibular dowel graft across the L5-S1 disc by using the anterior portion of the L5 body.
Objective: To introduce a technique for the treatment of isthmic spondylolisthesis in the setting of multilevel degenerative disc disease in adults. Our modified technique allows us to traverse the L5-S1 disc via the L4-5 disc space thereby treating the degenerated disc at L4-5 simultaneously.
Methods: A standard anterior discectomy was performed on L4-5. Using biplanar fluoroscopy, a Kirschner wire was placed beginning at the anterior third of the L5 superior endplate and ending at S1. An anterior cruciate ligament reamer was used to make a channel for the fibular allograft. Then, a femoral ring allograft was placed in the disc space at L4-5, and standard anterior lumbar interbody fusions were performed at any additional cephalad level(s). Afterward, posterior instrumented fusion was performed to complement the anterior fusion procedure (except at L5), and wide decompression followed.
Results: All patients presented with isthmic spondylolisthesis and all had multilevel fusions. The mean slip angle was 32.6 degrees (37.8 degrees preoperatively), and mean lumbar index was 67%. After the procedure, the average endplate-to-dowel angle was 107.1 degrees compared with 134 degrees. All patients had clinical and radiographic evidence of solid fusion without the need for revisions.
Conclusion: The proposed advantage of our modified technique is twofold. The graft is placed nearly perpendicular to the L5-S1 interface, as it will behave more efficiently with respect to interfragmental compression. Also, surgeons gain access to fuse L4-5 anteriorly and posteriorly.