P136. PEEK versus titanium cages in transforaminal lumbar interbody fusion: A 2-year follow-up study with clinical and radiological outcomes

Abstract

<h3>BACKGROUND CONTEXT</h3> Transforaminal lumbar interbody fusion (TLIF) has evolved as a treatment option for addressing various lumbar degenerative disorders and is now an established, widely performed technique owing to high fusion rates. However, successful fusion is limited by the properties inherent to the interbody devices utilized. Despite widespread application, concern over the use of polyetheretherketone (PEEK) cages have been raised due to their intrinsic hydrophobicity and a lack of osteoconductivity. In contrast, superior rates of fusion and clinical outcomes have been reported in patient cohorts treated with titanium (Ti) cages, considering metal's bioactivity in the role of spinal fusion. Furthermore, it has been hypothesized that the increased stiffness of Ti cages may result in a higher risk of subsidence. Current studies examining the utility of metal versus PEEK cages exist but describe small sample sizes with relatively short follow-up; thus, further investigation is warranted. To justify the utilization of Ti over PEEK cages in TLIF and to confirm prior hypotheses, we must compare the revision rate, graft subsidence rate, prevalence of fusion and functional outcomes of patients treated with both cage types. <h3>PURPOSE</h3> To compare 2-year clinical and radiological outcomes of PEEK versus Ti cages in TLIF. <h3>STUDY DESIGN/SETTING</h3> Retrospective Cohort Study. <h3>PATIENT SAMPLE</h3> A total of 320 consecutive patients from 2013-2018 with a minimum follow-up of 2 years. There were 137 that underwent TLIF with a Ti cage and 183 underwent TLIF with a PEEK cage. <h3>OUTCOME MEASURES</h3> (1) Revision rate and average time to revision. (2) Graft subsidence and fusion rates. (3) Functional outcome scores including Oswestry Disability Index (ODI), Visual Analog Scale for leg (VAS-l) and back (VAS-b) pain. <h3>METHODS</h3> A retrospective review was performed to identify all patients between 2013-2018 who underwent open or minimally invasive (MI) TLIF and received either a Ti or PEEK cage with a minimum follow-up of 2 years. Demographic data was recorded and compared between both cohorts. Revision rates, time to revision, graft subsidence and fusion rates in each group were also compared. Graft subsidence was defined as cage migration into one vertebral endplate >3mm on plain radiographic measurement. Bony fusion was defined as the absence of a radiolucent gap between the cages and endplates and the presence of trabeculation and bony bridging between cages and adjacent endplates. Functional outcomes were assessed with ODI, VAS-l and VAS-b measurements at follow-up visits. All intraoperative complications were reviewed. Standard binomial and categorical comparative analyses were performed. <h3>RESULTS</h3> A total of 320 consecutive patients were included, 137 (42 open, 95 MI) in the Ti cohort and 183 (53 open, 130 MI) in the PEEK cohort. Mean follow-up of the PEEK and Ti cohorts were 44.2 and 40.8 months, respectively. Complication rates were 2.7% and 3.7% for the PEEK and Ti cohort, respectively (p= 0.04). The most common complication was durotomy. The overall revision rates were 10.4% for the PEEK cohort and 2.9% for the Ti cohort (p= 0.01). Mean time to revision was 375.4 and 346.6 days for the Ti and PEEK groups, respectively (p=0.48). The graft subsidence rate for the PEEK cohort at 3, 6, 12 and 24 months postoperatively was 2.7%, 5.5%, 7.7% and 9.8%, respectively. Subsidence in the Ti group was more favorable overall, showing 2.9%, 5.1%, 6.6% and 8.0% subsidence at the same time points. Successful spinal fusion at 24 months was 94.9% and 92.9% in the Ti and PEEK groups, respectively (p=0.5). There were 112 males and 71 females in the PEEK cohort compared to 77 males and 60 females in the Ti cohort (p= 0.4). Both groups experienced significant improvements in their functional outcome scores (ODI, VAS-leg, VAS- back) compared to their preoperative values. There were no statistically significant differences in complication rate, revision rate, graft subsidence, or spinal fusion rates between minimally invasive and open techniques within groups. <h3>CONCLUSIONS</h3> The Ti cohort in this study demonstrated a higher rate of fusion, lower rates of revision and subsidence, and similar improvements in functional outcome scores as the PEEK cohort at the 2-year timepoint. Further studies should consist of randomized controlled trials with blinded assessments to definitively conclude the advantages of Ti cages for TLIF. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.