The Effect of Positional Graft Placement on Pseudarthrosis Rates in Anterior Cervical Discectomy and Fusion

Study Design. Case Control Study Objectives. To examine the relationship between interbody graft position along the vertebral body and pseudarthrosis rates in patients undergoing anterior cervical discectomy and fusion (ACDF). Summary of Background Data. ACDF is the most common surgical treatment for cervical degenerative conditions. A common postoperative complication is fusion degradation, which can progress to pseudarthrosis through implant loosening and subsequent intersegmental motion. Pseudarthrosis remains a leading cause of postoperative pain and reoperations. Material and Methods. The study included 118 patients who underwent single-level (45) or multi-level (73) ACDF, comprising a total of 221 individual levels. A dynamic mobility criterion was used to determine pseudarthrosis and validate functional cervical mobility from radiographs. Graft position was dichotomized into anterior or posterior position. Multivariable logistic regression considering patient demographics, surgical factors, and implant characteristics was conducted to associate radiologic parameters with pseudarthrosis. Levels with anterior or posterior positioned grafts were matched 1:1 on the propensity score using a nearest neighbor algorithm. Results. Of the 221 levels, 137 levels (61.99%) were fused, and 84 levels (38.01%) were consistent with radiographic criteria for pseudarthrosis. The average free space posterior to the graft was significantly larger in the fused group (3.41±2.50 mm) than the pseudarthrosis group (2.41±2.36 mm) ( P =0.005). On multivariable regression analysis, increased free space posterior to the graft (OR=0.839,95% Confidence Interval=0.715-0.978, P =0.027) was associated with decreased pseudarthrosis. After propensity score matching, 124 levels with common support were identified. In the matched cohort, the anterior positioned graft group consisted of 29.03% levels with pseudoarthrosis compared to 51.61% in the posterior positioned graft group ( P =0.017). Conclusion. Posterior graft placement during ACDF increases the likelihood of pseudarthrosis. Therefore, anterior placement of the interbody graft in single and multi-level ACDF may reduce the risk of pseudarthrosis. Further studies incorporating patient reported outcomes are warranted to clarify the clinical significance of graft positioning. Level of Evidence. Level IV