Resident Physician Barrow Neurological Institute Phoenix, Arizona, United States
Introduction: Lateral lumbar interbody fusion (LLIF) is well established in the literature to result in high rates of arthrodesis, ranging from 75 to 92%. Prior publications have described the use several fusion substrates in these procedures, including autograft, calcium triphosphate, and demineralized bone matrix. In this study, we investigated our own rates of fusion and pseudarthrosis following LLIF utilizing a cellular allograft (Osteocel, Nuvasive Inc.), as the sole fusion substrate.
Methods: We performed a retrospective analysis of LLIFs performed by a single surgeon at our institution. 1-year computed tomography (CT) scans were independently assessed for pseudarthrosis by a fellowship-trained neuroradiologist. Patients were determined to have developed pseudarthrosis if they were classified as Lenke C or D, or if they required re-operation for symptomatic pseudarthrosis prior to their 1-year CT scan.
Results: 95 patients with 191 levels of LLIFs were included. 19 levels (9.9%) developed pseudarthrosis – 4 of these were discovered prior to the 1-year CT scan and required operative revision. 2 of the remaining 15 levels went on to require surgical revision; the other 13 remained asymptomatic. Significant predictors of pseudarthrosis were age (70.9 vs. 68.4, p = 0.01), BMI (32.2 vs. 27.4, p < 0.001), L1 Hounsfield units (114.6 vs. 160, p < 0.001), ratio of implant area to inferior endplate area (0.39 vs. 0.46, p = 0.005), and cage material (14.2% pseudarthrosis with PEEK vs. 2.8% with titanium, p = 0.012).
Conclusion : LLIF using cellular allograft results in a high rate of fusion, comparable to the literature standard. We observed a combined clinical and radiographic pseudarthrosis rate of 9.9% (19/191 levels) at 1 year post-surgery. 31% (6/19 levels) of these cases required operative intervention. Risk factors for developing pseudarthrosis included increased age, higher BMI, lower bone mineral density, lower ratio of implant surface area to endplate surface area, and PEEK graft.
