The Efficacy,Complications And Finite Element Analysis Of Oblique Lateral Interbody Fusion In Lumbar Degenerative Diseases

Objective:To compare the efficacy and complications of OLIF and TLIF in the treatment of lumbar degenerative diseases.And to investigate the biomechanical differences of OLIF combined with different internal fixation.Methods:From January 2016 to April 2018,25 patients with oblique lateral interbody fusion(OLIF)and transforaminal lumbar interbody fusion(TLIF)were collected.The gender,age,bone mineral density(BMD),body mass index(BMI),fusion segment,preoperative and postoperative visual analog scale(VAS)and dysfunction index(ODI),operation time,intraoperative bleeding volume,hospital stay and complications were compared between the two groups.The data of preoperative and postoperative intervertebral disc height,intervertebral foramen height,intervertebral foramen area,spinal canal diameter,spinal canal area,fusion cage subsidence and fusion rate were also collected.Finite element model of OLIF L3-5 under five different fixed modes was established by finite element analysis software:(1)posterior bilateral pedicle screw fixation,(2)lateral single screw rod fixation,(3)lateral double screw rod fixation,(4)lateral single screw rod+ipsi lateral articular process screw fixation,and(5)lateral single screw rod+contralateral articular process screw fixation.To observe the stress distribution of screw in different motion states of spine and compare the stability of five fixation methods.Results:The operation was successfully completed in both groups.There was no significant difference in gender,age,BMD,BMI,fusion segment,preoperative VAS and ODI between the two groups.There was no significant difference in operation time,intraoperative bleeding volume and hospitalization days between the two groups(P>0.05);in cage sinking,there were more sinking cases in OLIF group,but there was no statistical significance compared with TLIF group;in perioperative complications,there was one case in OLIF group had incision fat.Fatty acid liquefaction was recovered after active dressing change.Skin temperature of lower extremity was changed in one patient.Sympathetic chain injury was considered during operation,and muscle strength of hip flexion or knee flexion was decreased in two patients.In TLIF group,1 patient had incision infection,and 1 patient had numbness and fatigue of healthy lower limbs.The VAS and ODI scores of the two groups were significantly improved after operation and the last follow-up,but there was no statistical difference between the two groups.In preoperative and postoperative intervertebral disc height,intervertebral foramen height,intervertebral foramen area,spinal canal diameter,spinal canal area,OLIF group after surgery data were significantly higher than before,the difference was statistically significant.In the distribution of vertebral stress,bilateral posterior pedicle screw fixation has the lowest stress,but in the distribution of upper and lower endplate stress,the lateral single screw rod+ipsilateral articular process screw is similar to the posterior bilateral pedicle screw.Therefore,from the distribution of end plate stress,the lateral single screw rod+ipsilateral articular process screw does not increase the risk of fusion device sinking.In the stress distribution of internal fixation,the stress mainly distributed at the tail of the screw,the middle of the connecting rod and the junction of the superior and inferior articular processes,among which the stress distribution of bilateral pedicle screw fixation was the smallest.On the displacement of the fixed segment,the lateral single screw rod displacement is larger in all directions;the lateral double screw rod displacement is smaller in lateral bending and rotation,but still larger in flexion and extension;the lateral single screw rod+ipsilateral articular process screw and bilateral posterior pedicle screw displacement is smaller in all directions.Conclusions:Overall,OLIF is suitable for patients with good bone quality,mild lumbar spinal stenosis and mild lumbar spondylolisthesis.On the premise of strict selection of suitable indications and careful operation during operation,OLIF can exert its greatest technical advantages and achieve similar therapeutic effects as TLIF.However,there are also some complications,such as sinking of fusion cage,decrease of lower limb muscle strength and sympathetic feeling after operation.Chain damage.Lateral single screw rod plus ipsilateral articular process screw can achieve the same fixation effect as posterior bilateral pedicle screw in OLIF.The clinical operation is simple and the surgical injury is relatively small.It may become an alternative fixation method for posterior bilateral pedicle screw.