Influences of different cage implantation techniques on posterior lumbar interbody fusion

English Keywords:Lumbar interbody fusion  Cage implantation methods  All pedicle screw system  Intervertebral bone graft  Fusion rate

English Abstract:

  【Abstract】 Objectives: To explore the influence of the cage implantation methods on lumbar fusion. Methods: Two-hundred patients underwent the L4/5 or L5/S1 single-level lumbar interbody fusion from June 2010 to June 2014 were reviewed. According to the cage implanted methods, the patients were divided into oblique implantation group(100 cases) and transverse implantation group(100 cases). The age, sex, bone mineral density(BMD), body mass index(BMI) and operative level of the two groups were recorded. Oswestry disability index(ODI) and visual analog scale(VAS) score were recorded before operation, postoperation and at the last follow-up. The X-ray and CT examinations were performed at 1 week, 6 months, 12 months and last follow-up after operation. The height of intervertebral space was measured preoperatively, 1 week after operation and at the last follow-up. The area of bone graft and the distance between the cage and the edge of the vertebral body were measured at 1 week and the last follow-up after operation. Reform Brantigan scores were used to evaluate intervertebral fusion at 6 months, 12 months and the last follow-up after operation. The breakage of screws and rods and recurrent back pain during follow-up were recorded. Results: There were no statistical differences in age, gender, BMD, BMI index and surgical segments between the two groups(P>0.05). Preoperative intervertebral space height, ODI and VAS scores were not significantly different between the two groups(P>0.05). All patients were followed up for more than 24 months. In both group, the ODI and VAS scores at the last follow-up were significantly improved compared with those before the operation(P<0.05). There was no statistical difference in the height of cage between the two groups(P>0.05), and there was no statistical difference in the height of intervertebral space after operation compared with that before operation(P>0.05). One week after operation, the average area of bone graft in transverse implantation group(322.26±32.36mm2) was larger than that in oblique implantation group(198.40±22.08mm2)(P<0.05). In oblique implantation group, the distance between the fusion cage and the left and right sides of the vertebral body were 8.5±1.2mm and 21.2±1.5mm respectively, and the distance from the posterior margin of the vertebral body was 4.2±0.5mm. In transverse implantation group, the distance between the fusion cage and the left and right sides of the vertebral body were 13.1±1.8mm and 14.2±1.4mm, and the distance from the posterior margin of the vertebral body was 9.8±0.8mm. There was significant difference between the two groups(P<0.05). The fusion rate in transverse implantation group(90%) was higher than that in oblique implantation group(71%) at 6 months after operation(P<0.05), but there was no significant difference between the two groups at 12 and 24 months follow-up(P>0.05). At the last follow-up, the loss of intervertebral space height in transverse implantation group(1.8±1.6mm) was lower than that in oblique implantation group(2.6±1.7mm), the bone graft area in transverse implantation group(423.56±23.29mm2) was larger than in oblique implantation group(299.64±21.68mm2), and there was significant difference between the two groups(P<0.05). During follow-up, 4 patients in the oblique group had screw and rods breakage, 5 patients had back pain recurred; there was no screw or rods breakage in the transverse group, and 2 cases had back pain recurred. There was significant difference between the two groups(P<0.05). Conclusions: Both transverse and oblique implantation methods of cage in posterior lumbar interbody fusion can achieve satisfactory clinical results. However, transverse implantation can better maintain the height of the intervertebral space, and the early fusion rate is higher, which can reduce postoperative screw or rods breakage, recurrence of back pain and other complications.