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Objective : Oblique lumbar interbody fusion (OLIF) is a surgical technique that utilizes a large interbody cage to indirectly decompress neural elements. The position of the cage relative to the vertebral body could affect the degree of foraminal decompression. Previous studies determined the position of the cage using plain radiographs, with conflicting results regarding the influence of the position of the cage to the degree of neural foramen decompression. Because of the cage obliquity, computed tomography (CT) has better accuracy than plain radiograph for the measurement of the obliquely inserted cage. The objective of this study is to find the correlation between the position of the OLIF cage with the degree of indirect decompression of foraminal stenosis using CT and magnetic resonance imaging (MRI).Methods : We review imaging of 46 patients who underwent OLIF from L2-L5 for 68 levels. Segmental lordosis (SL) was measured in a plain radiograph. The positions of the cage were measured in CT. Spinal canal cross-sectional area (SCSA), and foraminal crosssectional area (FSCA) measurements using MRI were taken into consideration.Results : Patients’ mean age was 69.7 years. SL increases 3.0±5.1 degrees. Significant increases in SCSA (33.3%), FCSA (43.7% on the left and 45.0% on the right foramen) were found (p<0.001). Multiple linear regression analysis shows putting the cage in the more posterior position correlated with more increase of FSCA and decreases SL correction. The position of the cage does not affect the degree of the central spinal canal decompression. Obliquity of the cage does not result in different degrees of foraminal decompression between right and left side neural foramen.Conclusion : Cage position near the posterior part of the vertebral body increases the decompression effect of the neural foramen while putting the cage in the more anterior position correlated with increases SL.

BACKGROUND Endoscopic spine surgery is an alternative to the traditional treatment of lumbar disc herniation. However, the traditional technique of interlaminar endoscopic approach is challenging and risky in patients with concomitant spinal stenosis. OBJECTIVE To report a modified technique called hybrid interlaminar endoscopic lumbar decompression as an effective treatment. METHODS Patients with combined lumbar disc herniation and lateral recess stenosis undergoing full-endoscopic interlaminar lumbar discectomy were retrospectively studied. The hybrid interlaminar endoscopic discectomy technique, as well as the use of 2 endoscopes with different diameters, is described in detail. The large endoscope is used for the laminotomy procedure, while the small endoscope is used for the discectomy procedure. The demographics and clinical outcomes of the patients are presented. RESULTS A total of 19 patients were included in this study. The mean age was 46.7 yr. The visual analog scale for back and leg pain improved from 5.6 ± 3.4 and 7.5 ± 2.3 to 1.8 ± 1.3 and 1.8 ± 1.6, respectively (P &lt; .001). The mean Oswestry Disability Index improved from 59.9 ± 21.2 preoperatively to 18.2 ± 8.5 postoperatively (P &lt; .001). The follow-up was 8.2 mo on average. No major complications occurred, but 2 patients reported mild postoperative paresthesia. One patient had an early recurrence and underwent repeat endoscopic discectomy. CONCLUSION Full-endoscopic lumbar discectomy provides excellent access to the intracanalicular herniation site of an intervertebral disc. By using the endoscopic technique presented here, surgeons can safely and efficiently achieve adequate decompression in patients with lumbar disc herniation combined with spinal stenosis.