1571. Expandable Versus Static Cages in Posterior and Transforaminal Lumbar Interbody Fusion: A Systematic Review and Meta-Analysis

Authors: Malia McAvoy; Paola Calvachi, MD, MSc; Christian Cerecedo-Lopez, MD; Alexander Hulsbergen; Rania Mekary; William Gormley; Hassan Zaidi, MD (Boston, MA)

Introduction: This study aimed to compare outcomes among patients who underwent posterior or transforaminal lumbar interbody fusion with static cages versus expandable cages. Methods: A systematic search of PubMed, Embase, Cochrane and Web of Science was carried out in accordance with the PRISMA guidelines from January 2000 to June 2018 to identify studies reporting Oswestry Disability Index (ODI), Visual Analog Scale (VAS), neuroforaminal height, disc height or fusion rate among patients with posterior or transforaminal lumbar interbody fusion. Using the random-effects model, pooled standardized mean differences (SMD) were calculated for the main continuous outcomes. Fusion rate at 12 months and pooled estimates of secondary outcomes including length of stay, operating room time, and blood loss were also calculated. Results: Twenty articles with 1604 patients met inclusion criteria. Mean ODI score was significantly different between the two groups (Expandable: SMD: 4.87 (3.24-6.49), I2=97.6%; Static: mean: 7.66 (5.67-9.66), I2=94.1%; p-interaction=0.03). There was no significant difference in fusion rate (Expandable: n=8 studies, mean: 0.91 (0.82-0.95), Static: n=5, mean:0.92 (0.87-0.96); p=0.54), neuroforaminal height (Expandable: n:6, mean: 0.76 (0.27-1.26); Static: n:2, mean: 0.86 (-0.04-1.76); p=0.85), disc height (Expandable: n:8, mean: 1.17 (0.70-1.63); Static: n:4, mean: 0.88 (0.20-1.56); p=0.49), and VAS score (Expandable: n:5, mean: 1.54 (0.96-2.11); Static: n:5, mean: 1.83 (1.23-2.42); p=0.49) between expandable and static groups. For the same comparison, random-effects analysis for mean age (E: 61.54(46.22-76.88), S: 31.99(18.1-45.89), p<0.01), blood loss (E: 187.54 (76.28-298.80), S: 325.92 (229.09-422.76), p=0.07), length of stay (E:3.13(0.09-6.17), S:6.96(5.09-8.83), p=0.04) and OR time (E:151.2 (123.99-178.40), S: 135.6 (115.71-155.49), p=0.36) were performed. Conclusion: The use of expandable interbody implants was not associated with inferior results when compared with static cages in terms of fusion rate, disc height, neuroforaminal height, pain and disabilities scores. However, expandable cages may be associated with less blood loss and length of stay.