Study designBiomechanical cadaveric study ObjectiveTo compare biomechanical properties of a single stand-alone interbody fusion and a single-level pedicle screw construct above a previous lumbar pedicle fusion.Summary of background dataAdjacent segment disease (ASD) is spondylosis of adjacent vertebral segments after previous spinal fusion. Despite the consensus that ASD is clinically significant, the surgical treatment of ASD is controversial.MethodsLateral lumbar interbody fusion (LLIF) and posterior spinal fusion (PSF) with pedicle screws were analyzed within a validated cadaveric lumbar fusion model. L3-4 vertebral segment motion was analyzed within the following simulations: without implants (intact), L3-4 LLIF-only, L3-4 LLIF with previous L4-S1 PSF, L3-4 PSF with previous L4-S1 PSF, and L4-S1 PSF alone. L3-4 motion values were measured during flexion/extension with and without axial load, side bending, and axial rotation.ResultsL3-4 motion in the intact model was found to be 4.7 ± 1.2 degrees. L3-4 LLIF-only decreased motion to 1.9 ± 1.1 degrees. L3-4 LLIF with previous L4-S1 fusion demonstrated less motion in all planes with and without loading (p < 0.05) compared to an intact spine. However, L3-4 motion with flexion/extension and lateral bending was noted to be greater compared to the L3-S1 construct (p < 0.5). The L3-S1 PSF construct decreased motion to less than 1° in all planes of motion with or without loading (p < 0.05). The L3-4 PSF with previous L4-S1 PSF constructs decreased the flexion/extension motion by 92.4% compared to the intact spine, whereas the L3-4 LLIF with previous L4-S1 PSF constructs decreased motion by 61.2%.ConclusionsStand-alone LLIF above a previous posterolateral fusion significantly decreases motion at the adjacent segment, demonstrating its utility in treating ASD without necessitating revision. The stand-alone LLIF is a biomechanically sound option in the treatment of ASD and is advantageous in patient populations who may benefit from less invasive surgical options.

Background: The purpose of this study was to determine if oblique magnetic resonance imaging (MRI) sequences affect the surgical treatment recommendations for patients with cervical radiculopathy. Methods: In this cohort study consecutive clinical cases of persistent cervical radiculopathy requiring surgical intervention were randomized, blinded, and reviewed by 6 surgeons. Initially each surgeon recommended treatment based on the history, physical examination, and axial, coronal and sagittal preoperative magnetic resonance (MR) images; when reviewing the cases the second time, the surgeons were provided oblique MR images. This entire process was then repeated after 2 months. Change in surgical recommendation, interobserver and intraobserver reliability and the average number of levels fused was determined. Results: The addition of the oblique images resulted in the surgical recommendation being altered in 49.2% (59/ 120) of cases; however, the addition of oblique images did not substantially improve the interobserver reliability of the treatment recommendation (j ¼ .57 versus.57). Similarly, the overall intraobserver reliability using only traditional MRI sequences (j ¼ .64) was only slightly improved by the addition of oblique images (j ¼ .66). Lastly, the addition of oblique images did not change the average number of levels fused (traditional MRI ¼ 1.38, oblique MRI ¼ 1.41, P ¼ .53), or the total number of 3-level fusions recommended (6 versus 6, P ¼ 1.00) Conclusions: The additional oblique images resulted in a change to the surgical plan in almost 50% of cases; however, it had no substantial effect on the reliability of surgical decision making. Further studies are needed to see if this alteration in treatment affects clinical outcomes.

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