Treatment of Adjacent Segment Disease Associated with Lumbar Fusion

Background: Spondylosis, or arthritis of the spine, is an increasingly common finding in the segments adjacent to the site of prior spinal fusions on long-term follow up. A clinically significant subset of these patients with spondylosis will become symptomatic, a condition referred to as adjacent segment disease (ASD). Current operative interventions for ASD most commonly include decompression of the involved segment with extension of the prior fusion to include the diseased segment (Sears et al., 2011). However, there is limited consensus among current operative treatment modalities. The conventional approach is caudal/cephalad extension of prior posterior spinal fusion (PSF) for the treatment of lumbar ASD. Other approaches involve the addition of an interbody fusion or a stand-alone interbody cage, with the fusion device inserted in the intervertebral space. Successful outcomes have been reported for the surgical management of a multitude of disease processes, but there is limited data comparing these various surgical approaches for ASD (Palejwala et al., 2014). Purpose: To determine the utility of interbody fusion as an acceptable surgical option in the treatment of adjacent segment disease. Method: We identified adults who underwent two lumbar spinal fusion procedures with the subsequent being for adjacent segment disease. Subjective measurements of pain, neurological deficit, and functional limitation were recorded before and after each operation. Post-operative measures were compared to the pre-operative baseline at the first, second, and third post-op visits. Results: A total of 57 patients were included in this review, consisting of 19 PSF, 8 interbody fusions, and 30 PSF/interbody combination fusions. Patients who underwent PSF with interbody fusion had better short-term outcomes compared with patients who underwent standalone PSF procedures. At the first post-op visit, patients who underwent the PSF/interbody combination fusion were significantly more likely to have improvement in pain (77% v. 33%, p<0.01) and neurological deficit (33% v. 16%, p<0.01) than patients who underwent the PSF alone. There was no significant difference in functional status improvement (43% v. 47%, p=0.879) or the average length of stay following the surgery (6 days v. 8 days, p=0.190). Conclusion: These findings suggest that the combination of a PSF with an interbody fusion may have better subjective outcomes following surgery for ASD when compared to the conventional approach of using a PSF alone. Our future goals are to correlate these findings with more objective measures, including surgery time, blood loss, cost, etc. and to stratify the data by the type of approach used for interbody placement, as some approaches are more minimally invasive with decreased rates of morbidity and revision dissections.