Lateral Lumbar Interbody Fusion (LLIF) is an effective, minimally invasive option to decompress the neural elements; however, subsidence remains a risk postoperatively. The objective of this study is to analyze the effect of lateral plate screw placement techniques on postoperative subsidence. A retrospective review was conducted at two quaternary referral centers from 2014-2022. Radiographic subsidence, bony fusion, and screw length were measured on follow-up imaging. Continuous and categorical variables were compared with two-sided independent-samples T-tests and Chi-squared/Fisher’s exact test, respectively. Multiple logistic regression was conducted to analyze factors associated with subsidence risk. A total of 144 patients with 218 operative levels were included. Mean age was 69 ± 11, 59% of the cohort was female, and 10% were active smokers. Median imaging follow-up was 13 IQR: 11-29 months. Of the 218 operative levels, 27 (12%) experienced grade I or II subsidence. On univariate analysis, there was a statistically significant difference in subsidence rates based on cage material type (p = 0.033), presence of lateral plating (p = 0.012), number of operative levels (p = 0.034), and lateral plate screw type (p = 0.023). On multivariate analysis, bicortical screws (OR: 0.291 95% CI: 0.087-0.803, p = 0.016) reduced odds of subsidence, while unicortical screw (OR: 0.402, 95% CI: 0.098-1.267, p = 0.125) did not reduce odds of subsidence compared to no lateral plating. Based on these results, bicortical screw placement may be a protective factor against subsidence.
Wakelin et al. (Fri,) studied this question.
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