Lumbar Interbody Fusion Performed Using Hydroxyapatite Coated Screws with a Cortical Trajectory: A Retrospective Case-Series Reviewing 75 Patients

Abstract

Research Question: In treating patients that need lumbar interbody fusion surgeries, did the usage of hydroxyapatite (HA) coated Solera Spinal System screws in addition to a cortical trajectory surgical approach provide greater stability as measured by the number of post-operative complications compared to the usage of standard, uncoated pedicle screws in both a traditional trajectory and a cortical trajectory surgical approach?

Background, Significance, and Rationale for the Question: Lumbar interbody fusion (LIF) procedures are indicated for several spinal pathologies including degenerative disc disease, disc prolapse, disc herniation, and/or spondylolisthesis. Advancements such as hydroxyapatite (HA) coated pedicle screws and cortical bone insertion trajectory continue to innovate the procedure. We report on the outcomes of a 75-patient lumbar interbody fusion cohort using HA coated pedicle screws inserted using a cortical trajectory.

Material and Methods: We performed a retrospective review of 75 patients operated on by one surgeon over a 6-year period. Consecutive subjects that were at least 18 years of age and underwent either a transforaminal lumbar interbody fusion (TLIF) or posterior lumbar interbody fusion (PLIF) using HA coated pedicle screws inserted using a cortical bone trajectory were deidentified and included. Demographic and post-op Visual Analog Scale (VAS) pain data were recorded. Fusion was established radiologically by the operating surgeon and the subject’s record was reviewed for follow-up mention of spinal instability. To describe continuous variables, we calculated mean and standard deviation and generated frequency distributions for categorical data. We evaluated distributional assumptions using box-plots and histograms. Spearman rank correlation was calculated to describe association between continuous variables. We used the mixed-effects regression model to study the trend in VAS over time.

Results: All 75 patients resulted in stable fixation. We did not find any significant association between age and VAS over time (p>0.40). Similarly, there was no significant association between BMI and VAS at baseline and the subsequent 5 follow-up periods (p>0.11). Our mixed-effects regression model showed 0.37-point decrease on average in VAS per month. However, this finding was not statistically significant (p=0.23) at alpha 0.05.

Conclusion: The use of HA coated pedicle screws and insertion using the cortical trajectory demonstrated stable fusion. However, no significant relationship between patient demographic factors and the post-operative pain experienced could be established.