The Risk of Subsidence in Standalone Oblique Lumbar Interbody Fusion: A 12-Month Follow-Up Prospective Study

Background data: The incidence of interbody cage subsidence in oblique lumbar interbody fusion (OLIF) is 8 e 9.5%. It occurs mainly secondary to osteoporosis or end-plate damage during disk space clearance. An anatomical study correlated the surface area contact and position between the cage and the disk space to the incidence of subsidence. Studies have concentrated on the optimal place in the disk space to place the cage to obtain less incidence of subsidence, as it was reported that the central part of the disk space, called the epiphyseal ring, is the toughest part. Subsidence is usually noted in the superior vertebral end plate. Until now, there has been a lack of data regarding the main cause of subsidence. Study design: This is a prospective, clinical case study. Objective: This study aims to assess the subsidence rate in patients undergoing standalone (SA)-OLIF for degenerative lumbar diseases. Patients and methods: Patients with adult degenerative scoliosis following speci fi c inclusion criteria underwent SA-OLIF. The following data were all analyzed and compared statistically: preoperative and postoperative clinical data; back and leg pain visual analog score (VAS) and Oswestry disability index; radiological data; spinopelvic parameters, segmental Cobb ' s angle and anterior disk height, and intraoperative data; operative time; the amount of blood loss; complications (intraoperative or postoperative); and hospital stay. Results: A total of 28 patients and 30 levels were operated on by SA-OLIF, with a mean age of 50.54 ± 6.05, including 14 males and 14 females. The mean operative time/min, blood loss, and hospital stay/day was 91.29 ± 14.23, 195.54 ± 42.299, and 2.78 ± 0.875, respectively. The mean of back pain VAS, the mean of leg pain VAS, and Oswestry disability index changed from preoperatively 7.36 ± 0.98, 6.36 ± 0.911, and 53.71 ± 18.9 to 4.07 ± 1.01, 2.07 ± 0.9, and 45.25 ± 18.76 in 1 year, respectively. Fusion rates were assessed at 6 and 12 months by multislice computed tomography. During the 6-month follow-up period, 83.3% (25 levels) of grade I and grade II fusion was interpreted as solid fusion and 6.6% as cage subsidence (two levels), and during the 12-month follow-up, 89.9% (27 levels) as grade I and grade II fusion and 6.6% cage subsidence (two levels). Conclusion: Subsidence in SA-OLIF highly contributed to end-plate injury during the surgery and osteoporosis; consequently, posterior instrumentation is advised in these patients along with OLIF to decrease the subsidence rate.