P35. The effect of positional graft placement on pseudarthrosis rates in anterior cervical discectomy and fusion

BACKGROUND CONTEXT Anterior cervical discectomy and fusion (ACDF) is a common surgical treatment for cervical radiculopathy and degeneration. The procedure involves placement of an interbody graft, which may be paired with anterior plate fixation. Fusion degradation is a common outcome of ACDF, ultimately resulting in pseudarthrosis through loosening and subsequent intersegmental motion of hardware. PURPOSE The current study aims to determine an association between location of graft placement along the vertebral body and pseudarthrosis occurrence. STUDY DESIGN/SETTING Retrospective analysis of a consecutive series of patients who underwent single and multilevel ACDF between 2015 and 2021. PATIENT SAMPLE The surgeries were performed at a single tertiary academic medical center by one of four spine surgeons. The inclusion criteria consisted of patient age over 18, postoperative neutral position radiograph within the week of surgery, and flexion and extension radiograph at least 9 months after surgery but no more than 2 years post-surgery. Exclusion criteria included patients with posterior cervical brace hardware or corpectomy of two levels or more. A total of 79 patients with single (43) and multilevel ACDF (36) were included in our study. OUTCOME MEASURES Incidence of pseudarthrosis between 9 and24 months following ACDF. METHODS A dynamic mobility criteria was used to determine pseudarthrosis status by utilizing >= 4 mm superjacent interspinous motion to validate functional cervical mobility and >= 1 mm interspinous movement to indicate pseudarthrosis. Graft length and vertebral body length were measured at 175% magnification on the most recent radiograph after time of surgery. These measurements were calibrated to the flexion and extension radiographs. Flexion and extension spinous movements were measured at 150% magnification on the radiograph closest to the 2-year postoperative mark. T1 slope, cervical lordosis angle, and sagittal vertical axis length were also measured in neutral position on the flexion and extension radiographs. All measurements were determined by a single independent investigator. A multivariate logistic regression controlling for age, gender, and smoking status was used to analyze the data. RESULTS Of the 128 levels analyzed, 78 were fused and 50 were consistent with radiographic criteria for pseudarthrosis. Increases in unoccupied space posterior to the graft decreases the likelihood of pseudarthrosis (p < 0.05) on both univariate and multivariate logistic regression. Similarly, the percentage of unoccupied space posterior to the graft was also associated with decreased pseudarthrosis on univariate analysis (p 0.05). The mean posterior graft distance overall for successful fusions was 3.98 mm and 2.97 mm for pseudarthrosis (p < 0.05). CONCLUSIONS The results of this study indicate that increasingly, posterior placement of the graft increases likelihood of pseudarthrosis. Therefore, our results support positioning of grafts more anteriorly along the vertebral body to decrease the risk of pseudarthrosis following ACDF. FDA Device/Drug Status This abstract does not discuss or include any applicable devices or drugs. Anterior cervical discectomy and fusion (ACDF) is a common surgical treatment for cervical radiculopathy and degeneration. The procedure involves placement of an interbody graft, which may be paired with anterior plate fixation. Fusion degradation is a common outcome of ACDF, ultimately resulting in pseudarthrosis through loosening and subsequent intersegmental motion of hardware. The current study aims to determine an association between location of graft placement along the vertebral body and pseudarthrosis occurrence. Retrospective analysis of a consecutive series of patients who underwent single and multilevel ACDF between 2015 and 2021. The surgeries were performed at a single tertiary academic medical center by one of four spine surgeons. The inclusion criteria consisted of patient age over 18, postoperative neutral position radiograph within the week of surgery, and flexion and extension radiograph at least 9 months after surgery but no more than 2 years post-surgery. Exclusion criteria included patients with posterior cervical brace hardware or corpectomy of two levels or more. A total of 79 patients with single (43) and multilevel ACDF (36) were included in our study. Incidence of pseudarthrosis between 9 and24 months following ACDF. A dynamic mobility criteria was used to determine pseudarthrosis status by utilizing >= 4 mm superjacent interspinous motion to validate functional cervical mobility and >= 1 mm interspinous movement to indicate pseudarthrosis. Graft length and vertebral body length were measured at 175% magnification on the most recent radiograph after time of surgery. These measurements were calibrated to the flexion and extension radiographs. Flexion and extension spinous movements were measured at 150% magnification on the radiograph closest to the 2-year postoperative mark. T1 slope, cervical lordosis angle, and sagittal vertical axis length were also measured in neutral position on the flexion and extension radiographs. All measurements were determined by a single independent investigator. A multivariate logistic regression controlling for age, gender, and smoking status was used to analyze the data. Of the 128 levels analyzed, 78 were fused and 50 were consistent with radiographic criteria for pseudarthrosis. Increases in unoccupied space posterior to the graft decreases the likelihood of pseudarthrosis (p < 0.05) on both univariate and multivariate logistic regression. Similarly, the percentage of unoccupied space posterior to the graft was also associated with decreased pseudarthrosis on univariate analysis (p 0.05). The mean posterior graft distance overall for successful fusions was 3.98 mm and 2.97 mm for pseudarthrosis (p < 0.05). The results of this study indicate that increasingly, posterior placement of the graft increases likelihood of pseudarthrosis. Therefore, our results support positioning of grafts more anteriorly along the vertebral body to decrease the risk of pseudarthrosis following ACDF.