Risk factors and treatment strategies for cage migration following posterior lumbar interbody fusion

English Keywords:Lumbar interbody fusion  Cage  Complication  Revision surgery

English Abstract:

  【Abstract】 Objectives: To investigate the incidence of cage migration(CM) and its related risk factors and corresponding management strategies after open posterior lumbar interbody fusion(PLIF). Methods: A retrospective analysis was conducted on 970 patients(423 males and 547 females) underwent PLIF in the lumbar spine group of our hospital from January 2016 to December 2017. CM was defined as the posterior edge marking line on lumbar lateral X-ray moved more than 3mm compared with the first postoperative measurement, and the CM group was then screened out. A control group of 100 patients without CM was randomly selected. Parameters were compared between the two groups, including: general data [age, sex, body mass index(BMI)], subcutaneous lumbar spine index(SLSI), estimated blood loss, preoperative and postoperative lumbar lordosis, preoperative and postoperative mean disc height, preoperative and postoperative posterior disc height, preoperative and postoperative range of motion of the disc space, endplate injury, osteoporosis, depth of screw, shape of disc space, and cage depth. The parameters of univariate analysis with statistical significance were analyzed by Logistic regression to find the independent risk factors for CM. Results: The mean follow-up time was 43.4±18.2 months(6-66 months). 22 cages in 21 patients(2.16%) had CMs. The age, preoperative and postoperative mean disc height, postoperative intervertebral range of motion, the proportion of male patients, the proportion of osteoporosis patients, the proportion of screw loosening, and the proportion of pear-shaped disc space in the CM group were all higher than those without CM(P<0.05), while other factors showed no significant difference between the two groups(P>0.05). Logistic regression analysis showed screw loosening (OR=5.020, 95%CI 1.026-24.564, P=0.046), osteoporosis(OR=8.116, 95%CI 1.503-43.841, P=0.015), and pear-shaped disc space(OR=28.031, 95%CI 1.850-424.748, P=0.016) were independent risk factors for CM. Among the patients with CM, 12 cases(1.24%) had cage retropulsion(CR) which was defined as the movement of the posterior margin of the cage into the spinal canal. Among the 12 CR patients, 8 cases were asymptomatic and received conservative treatment, and successful fusion were acquired at the last follow-up(mean 52.4±7.6 months); 3 cases(0.31%) had significant low back pain and/or lower limb pain and failed to conservative treatment, whose symptoms were relieved after revision surgery; 1 case had the indication of revision surgery but the patient refused, and CM did not progress and successful fusion was acquired at the last follow-up(55 months). Conclusions: Osteoporosis, pear-shaped disc space, and screw loosening were independent risk factors for CM. Conservative treatment and close follow-up were feasible for patients with CM without obvious symptoms, and revision surgery should be performed for those with obvious neurological symptoms or instability.