Current incidence of adjacent segment pathology following lumbar fusion versus motion-preserving procedures: a systematic review and meta-analysis of recent projections

BACKGROUND CONTEXT Lumbar fusion surgery has been a successful option with improved patient-reported outcomes and functional status; however, it has been associated with in-hospital and postoperative complications. One particular biomechanical drawback of lumbar fusion surgery involves the impact it has on adjacent segments. Previous studies have shown lumbar fusion can result in increased range of motion (ROM) at cephalad and caudad adjacent segments, thus predisposing those segments to accelerated degenerative changes and clinically symptomatic pathology. The emergence of motion-preserving procedures (MPP) has allowed adjacent spinal segments to retain partial or full range of motion, and prevent rapid exacerbations in adjacent degenerative changes. PURPOSE In the spine literature, adjacent segment pathology (ASP) represents an umbrella term encompassing two concepts: adjacent segment degeneration (ASDeg) and clinical adjacent segment disease (ASDis). ASDeg refers to new radiographic changes at levels adjacent to a fusion construct; ASDis, on the other hand, refers to new clinical symptoms from the progressing adjacent segment pathology. The present systematic review and meta-analysis aimed to compare lumbar fusion techniques with current motion-preserving procedures with regards to ASDeg, ASDis, and reoperation rates due to ASP, as well as to provide updated incidence rates of ASP with long-term follow-up studies. STUDY DESIGN/SETTING Systematic review and meta-analysis. PATIENT SAMPLE A total of 1,751 patients (791 underwent fusion surgery and 960 motion-preserving procedures) in 19 publications were included in the final analysis. Lumbar fusion surgery procedures included: posterolateral lumbar fusion (PLF), posterior lumbar interbody fusion (PLIF), transforaminal lumbar interbody fusion (TLIF), and circumferential lumbar fusion. Motion-preserving procedures included: dynamic stabilization systems (Dynesys, Cosmic), total disc replacement, interspinous implants (Coflex), interspinous process spacer, and hybrid constructs. OUTCOME MEASURES Adjacent segment degeneration, adjacent segment disease, and reoperation rates. METHODS Following PRISMA guidelines, a systematic review and meta-analysis was conducted to find current (1/2012-12/2019) retrospective cohort studies and randomized controlled trials evaluating rates of ASDeg, ASDis, and reoperations due to lumbar ASP. A computerized literature search of relevant studies was conducted using the PubMed Medline/Central databases incorporating the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The search strategy identified all possible studies for inclusion using a combination of the following medical subject headings (MeSH): “lumbar spine,” “adjacent level pathology,” “adjacent segment pathology,” “adjacent level degeneration,” and “adjacent segment degeneration,” “total disc arthroplasty,” “interspinous spacer,” “interspinous implants” and “dynamic stabilization.” RESULTS A total of 1,751 patients (791 underwent fusion surgery and 960 motion-preserving procedures) in 19 publications were included in the final analysis. Overall incidence rates of ASDeg, ASDis, and reoperation rates were 27.84%, 7.58%, and 4.60%, respectively. Results showed no significant difference between the lumbar fusion vs MPP cohorts in incidence of ASDeg (36.44% vs 19.24%, p: 0.064), ASDis (10.74% vs 4.42%, p: 0.245), or reoperation due to ASP (7.40% vs 1.80%, p: 0.189). Fixed-effects analysis revealed patients who underwent MPP had significantly lower odds of ASDeg (OR: 2.57, CI: 1.95, 3.35, p: CONCLUSIONS Overall, our meta-analysis revealed no statistically significant difference in incidence of ASDeg, ASDis, or reoperations due to ASP for patients after lumbar fusion vs MPP. Weighted analysis, however, showed that MPP patients had significantly lower odds of ASDeg and reoperations due to ASP. Even though previous studies have shown the effectiveness of MPP in preserving adjacent level range of motion and slowing down the degenerative process, further studies are necessary to elucidate the procedure-specific effects of motion preservation on adjacent levels, patient-reported outcomes, complication rates, and inpatient/outpatient costs FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.