In Reply to the Letter to the Editor Regarding “Workforce Trends in Spinal Surgery: Geographic Distribution and Primary Specialty Characteristics from 2012 to 2017”

To compare outcomes of three-dimensional–printed porous titanium (Ti) versus polyetheretherketone (PEEK) cage implantation for stand-alone lateral lumbar interbody fusion (SA-LLIF) in treatment of symptomatic adjacent segment degeneration.Between October 2016 and July 2020, 44 patients (59 levels) underwent stand-alone lateral lumbar interbody fusion with Ti or PEEK cages. The primary outcome was cage subsidence. Secondary outcomes included revision and/or recommendations for revision surgery, back and/or leg pain severity, changes in disc and/or foraminal height, and global and/or segmental lumbar lordosis.The study included 44 patients (21 females) with a mean age at surgery of 61.8 ± 11.5 years, mean radiological follow-up of 12.5 ± 8.2 months, and mean clinical follow-up of 11.0 ± 7.1 months. Overall subsidence rate was significantly less in the Ti versus PEEK group (20% vs. 58.8%, P = 0.004). Revision was recommended to none of the patients in the Ti group and 3 patients in the PEEK group (P = 0.239). Patients in the Ti group showed significantly better improvement in back pain numeric rating scale score (P = 0.001). Disc height (P < 0.001) and foraminal height restoration (P = 0.011) were statistically significant in the Ti group, whereas only disc height restoration was significant in the PEEK group (P = 0.003).In patients undergoing stand-alone lateral lumbar interbody fusion to treat adjacent segment degeneration, Ti cages had a significantly lower overall subsidence rate compared with PEEK cages. Furthermore, Ti cages resulted in fewer recommendations for revision surgery. Whether greater pain reduction in the Ti group is associated with earlier or higher fusion rates needs to be further elucidated.