Intraoperative blood loss volume increases due to soft tissue injury or excessive traction generated by extensive approach including posterior fusion or posterior lumbar interbody fusion, leading to the occurrence of complication and delay in postoperative recovery, On the other hand, MI-TLIF minimizes injuries in soft tissue and surrounding muscle by approaching between multifidus muscles and longissimus dorsi after separating them, and reaching intervertebral disc from lateral vertebral foramen. The advantages of this surgical procedure are minimization of muscle or soft tissue injuries incurred by lateral approach, reduction of surgically related muscle damage, and decrease of postoperative blood loss. However, The size of cages are limited by transforaminal approach in MI-TLIF, eventually it could be difficult to maintain the correction of deformity(disc height, segmental and lumbar lordosis). Recently, DLIF(Direct lateral interbody fusion) is developed to improve the disadvantages of TLIF. DLIF allows to insert larger cage than TLIF, as a result larger cage have a advantage to maintain correction of disc height and lordosis because it can support both apophyseal rings of endplates. However, Transpsoas approach is essential for DLIF, so we need to understand the anatomy lumbosacral plexus in psoas, because nerve injury during the transpsoas approach is the most common and potentially the most devastating complication of the DLIF procedure. And many authors reported that various frequency of nerve injury according to surgeon’s skill. Therefore, surgeon’s skill and accurate understanding about the procedure are important factors to prevent the complications of DLIF.

Purpose
The purpose of this study is to decrease the frequency of the perioperative complication and improve the clinical outcomes of multilevel lumbar degenerative disease by multilevel minimally invasive transforaminal lumbar interbody fusion.
Materials and Methods
317 patients(Minimally invasive transforaminal lumbar interbody fusion : 161, Conventional open surgery : 156) were followed up for more than 1 year. The age of each patient, the amount of intraoperative blood loss, the postoperative drainage, the transfusion requirement, surgery time, using of Intensive care unit, ambulation day, admission day and perioperative complications were investigated and analyzed.
Results
Minimally invasive transforaminal lumbar interbody fusion was found to have a less blood loss, less using of Intensive care unit. And as the levels of union increase, disparities were increased(p<0.05). But, surgery time of Minimally invasive transforaminal lumbar interbody fusion was longer, and as the levels of union increase, disparities were increased(p<0.05).
Conclusions
Multilevel Minimally invasive transforaminal lumbar interbody fusion can be the better way, If surgery time of Multilevel Minimally invasive transforaminal lumbar interbody fusion can be reduced.