47. Does the use of interbodies in lumbar fusions affect the reoperation rate for adjacent segment disease (operative ASD)? Data from the Kaiser Permanente National Spine Registry

Abstract

BACKGROUND CONTEXT Circumferential lumbar fusions combine anterior column support using an anterior approach (anterior lumbar interbody fusion, ALIF), a lateral approach (lateral lumbar interbody fusion, LLIF) or a posterior approach (posterior lumbar interbody fusion, PLIF/transforaminal lumbar interbody fusion, TLIF), with posterior support with pedicle screw fixation (PS). Circumferential fusions have shown biomechanical advantages compared to posterolateral fusion (PLF) with pedicle screw fixation, including restoration of lordosis, indirect foraminal decompression, and reduction of the slip via ligamentotaxis. However, they may increase the stiffness of the spine due to anterior column support and loading. Although several small comparative studies reporting radiographic adjacent segment degeneration (ASD) and meta-analyses on adjacent segment disease (ASDis) have been published, to our knowledge, there are currently no large-scale studies that report ASDis. PURPOSE To assess the incidence of and risk for operative adjacent segment disease (ASDis) after circumferential lumbar fusion, by surgical approach, vs PLF. STUDY DESIGN/SETTING Retrospective cohort study using integrated health care data from the Kaiser Permanente Spine Registry. PATIENT SAMPLE A final retrospective cohort study using integrated health care data from the Kaiser Permanente Spine Registry, consisting of 5,521 patients with lumbar fusions completed between 01/01/2009 and 12/31/2018. OUTCOME MEASURES Five-year incidence rate of ASDis requiring reoperation. METHODS A total of 5,521 patients aged ≥18 who underwent primary elective lumbar fusion (L3-S1) for degenerative disc disease (2009-2018). Five-year incidence rates of validated, operative ASDis were calculated by fusion type (PLF, ALIF/LLIF+PS, and PLIF/TLIF+PS) and fusion level (1-2 levels). Covariate-adjusted time-dependent multivariable Cox-Proportional Hazards regression was used to evaluate reoperation rates with using PLF as the reference group. RESULTS Fifty percent of fusions were PLIF/TLIF+PS (N=2,821), more than one-third were PLF+PS (N=2006), and the remaining were ALIF/LLIF+PS (N=694). Average cohort age was 61.8 years (SD±12.7) and average follow-up was 4.8 years (SD±3.1). Five-year incidence rates of operative ASDis were 7.0% (95% confidence interval [CI] =6.4-7.7). Five-year incidence of operative ASD was similar in PLF and PLIF/TLIF+PS (7.7, 95% CI=6.6-9.0 and 7.1% 95% CI=6.2-8.1, respectively) but slightly lower in ALIF/XLIF+PS (5.3%, 95% CI=3.8-7.3). Highest 5-year incidence rates were seen in 2-level circumferential PLIF/TLIF (8.3%, 95% CI=6.0-11.11). After adjustment, there were no significant differences in operative ASDis risk by fusion type compared to PLF (ALIF/XLIF+PS: HR=0.7, 95% CI=0.5-1.1); PLIF/TLIF+PS: HR=1.0, 95% CI=0.8-1.2). CONCLUSIONS Analysis from a large cohort of over 5000 lumbar fusion patients found no differences in operative ASDis comparing circumferential fusions to posterolateral fusion at 5 years. This information is useful in informed consent for the patient. Further research for risk of operative ASDis with larger numbers of patients undergoing an anterior approach, as well as a longer follow-up period, is warranted. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.