Unilateral Expandable Interbody Cage Placement in Minimally Invasive Midline Fusion
Unilateral Expandable Interbody Cage Placement in Minimally Invasive Midline Fusion
Ishani Sharma, BS1, Michael Krzyskowski, PA,2 Nitin Khanna, MD, FAAOS2
1Indiana University School of Medicine, 2Orthopaedic Specialists of Northwest Indiana
Abstract
Introduction
Minimally invasive midline approach utilizing cortical screws has grown in popularity due to its familiar anatomy, limited dissection, and associated decreased morbidity. This approach is well-suited for bilateral “inline” cage placement after bilateral facetectomies. Many surgeons prefer to utilize a single cage, TLIF, for midline fusions to optimize time, decrease exposure, and lower costs. This novel study assessed cage position for a unilateral cage utilizing the minimally invasive midline approach.
Methods
Retrospective chart and radiograph review was performed on 25 consecutive patients who underwent a midline lumbar fusion utilizing a single expandable interbody cage. Post-operative radiographs were examined to determine cage position relative to the vertebral bodies. Cage positioning was graded A, B, or C based on its midline position relative to the medial, middle, or lateral third of the superior vertebral body.
Results
Surgeries were performed by a fellowship-trained orthopaedic spine surgeon. 25 patients (48% male; 26 cages, n=26) underwent a lumbar fusion utilizing a single, expandable interbody cage using a midline approach. 24 patients had one-level fusions, while 1 patient had a two-level fusion. 18 devices were graded "A"; 8 devices were graded "B". None received a grade of "C."
Conclusion
Ideal cage position for midline lumbar fusion is the middle-third of the superior vertebral body to allow for symmetric distraction and load sharing. This can be difficult to accomplish when utilizing a single cage, as it can be difficult to maintain the necessary 30-45-degree insertion angle in order to position the cage. With technical modifications to disc preparation, retractor considerations, and facetectomy we can obtain the necessary angles for cage placement without the need to increase exposure. The cage position was further optimized through radiographic imaging prior to the expansion of the lordotic oblique cage, highlighting another advantage to the expandable technology with this procedure.