Background
Minimally invasive transpsoas or antepsoas lateral lumbar interbody fusion (MI-LLIF) has been reported as an effective surgical option for various lumbar diseases. Many researchers reported high fusion rate and clinical excellence of LLIF with the use of bone morphogenic protein (BMP). However, there have been paucity of studies regarding LLIF without the use of BMP. Therefore, this study aimed to analyze radiologic and clinical results of patients who underwent minimally invasive lateral lumbar interbody fusion without the use of BMP. Furthermore, a further analysis was conducted regarding the frequency of cage subsidence and its impact on the radiologic and clinical outcome.
Materials and Methods
Fifty patients and 109 levels treated by MI-LLIF with postoperative follow-up of at least 2 years were included. Radiologic evaluation included intervertebral disc height, segmental lordosis, lumbar lordosis, fusion rate, cage subsidence grade, and the bone mineral density. Radiologic fusion was determined by modified Bridwell’s grade, and cage subsidence by Marchi’s grade. Clinical outcome was evaluated by VAS of low back pain (LBP) and leg pain, and ODI score. The above clinical and radiologic variables were analyzed statistically for comparison of cage subsidence and nonsubsidence groups.
Results
There were 20 male and 30 female patients with the average age of 69 years. Average follow-up period was 29.6 months(24-42 months). Graft material used for PEEK cage was autogenous bone only in 9 levels, autogenous bone and DBM in 19 levels, and DBM only in 81 levels. Twelve patients received surgery on 1 level, 20 patients on 2 levels, 17 patients on 3 levels, and 1 patient on 4 levels, respectively. Operated levels were L1-2 in 7 cases, L2-3 in 27, L3-4 in 41, and L4-5 in 34, respectively. Mean low back pain (LBP) VAS decreased from preoperative 5.5 to 2.2 at the final follow-up, leg pain from 6.1 to 1.7, and ODI score from 25.6 to 13.7, with statistical significance (p<0.001). Mean disc height increased from preoperative 5.9 mm to postoperative 11.5 mm, and subsequently decreased to 9.6mm at the final follow-up. Average lumbar lordosis increased from preoperative 18.6 degrees to postoperative 37.0 degrees, and 35.9 degree at final follow-up. Radiologic union rate was 90.8%. Cage subsidence was observed in 6 levels (5.5%) on immediate postoperative radiographs; and in 20 levels (18.3%) at final follow-up. Comparison between cage subsidence and non-subsidence groups revealed no significant difference in age and BMD. Immediate postoperative segmental lordosis was considered as a risk factor of cage subsidence (p=0.005, odds ratio 0.813, CI 0.703~0.940). Furthermore, the preoperative and the final follow-up measurement of disc height, VAS score of LBP and leg pain, and ODI score were not different between the two groups. However, pseudoarthrosis rate was higher in subsidence group.
Conclusions
Minimally invasive LLIF was an effective surgical option with high fusion rate even without the use of BMP. Although cage subsidence also increases the frequency of pseudarthrosis, it does not significantly deteriorate the lumbar lordosis correction and clinical outcome.

Purpose
Spinal fusion is useful method of treatment of degenerative lumbar diseases, and is divided into anterior and posterior surgery. Each approach has advangages and disadvantages. Recently, minimally invasive lateral lumbar interbody fusion (LLIF) supplemented disadvantages of anterior and posterior surgery is interested. We introduce LLIF and present about application and indication of LLIF.
Materials and Methods
A 76-year-old female was diagnosed by degenerative disc disease on L2-3. A 66-year-old male was diagnosed by central spinal stenosis on L2-3-4-5. A 86-year-old female was diagnosed by foraminal stenosis on L3-4-5 and degenerative scoliosis. A 73-year-old male was diagnosed by spinal stenosis on L3-4-5 and spondylolisthesis. A 70-year-old male was diagnosed nonunion on L4-5. On past history, the patient was operated by fusion because of L2 burst fracture. A 75-year-old female was diagnosed by infective spondylodiscitis on L3-4.
Results
Degenerative disc disease, severe central and foraminal spinal stenosis, degenerative scoliosis, spondylolisthesis and infective spondylodiscitis were application and indication of LLIF.
Conclusions
LLIF merges the advantages and covers the disadvantages of anterior and posterior surgery. However, approach-related lumbar plexus injury and L5-S1 approach were remained obstacles.

Lumbar fusion surgery for lumbar degenerative diseases has increased in the past several decades and many techniques for fusion surgery have been introduced. Recently lateral lumbar interbody fusion with minimally invasive technique was introduced and accepted as a useful method for various lumbar degenerative disease. It can produce good correction for sagittal and coronal imbalance with relatively decreased morbidity. The advantage of lateral lumbar interbody fusion is that it can avoid injury to the abdominal large vessels and neural structures which is more common during posterior approaches. However various complications had been reported. Complications related with lateral lumbar interbody fusion include neurologic complications including thigh pain and numbness, vascular complications including arterial injury, cage related complication such as cage subsidence and vertebral body fractures. Therefore special care should be taken to avoid possible complications in lateral lumbar interbody fusion surgery.

Many techniques have been introduced and performed, with different strengths and benefits. The lateral lumbar interbody fusion techniques (direct lateral lumbar interbody fusion [DLIF] and oblique lateral interbody fusion [OLIF]) have yielded good results for elderly patients. These are useful options for elderly patients with high risk of complications with traditional approaches.

A 77-year-old female suffering from severe degenerative scoliosis, spinal stenosis and lumbar disc herniation underwent Direct lateral lumbar interbody fusion (DLIF) at L2-4. On the 3rd postoperative day, she complained of severe back pain without any trauma history. Simple radiograph revealed L3 vertebral fracture and cage subsidence. Pain was subsided after conservative treatment including TLSO and medication. Radiographic union was achieved at fractured vertebra after 3 months. Solid fusion was observed at operated level after 6 months. Patient has visited our clinic without any pain. DLIF is one of novel minimally invasive spine procedures available today. It is designed to maximize benefits and minimize risks of other traditional techniques such as anterior approach and posterior approach. However, there can be some risk of cage subsidence and vertebral fracture after DLIF. Therefore, care should be taken to avoid cage subsidence during the operation.

Introduction
Recently, minimally invasive lateral approach for the lumbar spine is revived and getting popularity under the name of XLIF or DLIF by modification of mini-open method using sequential tubular dilator and special expandable retractor system. Purposes: The purposes of this study were to introduce the mini-open lateral approach for the anterior lumbar interbody fusion (ALIF), and to investigate the advantages, technical pitfalls and complications & to provide basic knowledge on XLIF or DLIF
Materials and Methods
Seventy-four patients who underwent surgery by the mini-open lateral approach from September 2000 to April 2008 with various disease entities were included. Blood loss, operation time, incision size, postoperative time to mobilization, length of hospital stay, technical problems and complications were analyzed.
Results
With this approach, we can reach form T12 to L5 subdiaphragmatically. The blood loss and operation time of patients who underwent simple ALIF were 61.2 ml and 86 minutes for one level, 107 ml and 106 minutes for two levels, 250 ml and 142.8 minutes for three levels, and 400 ml and 190 minutes for four levels of fusion, respectively. The incision sizes were on average 4.5cm for one level, 6.3 cm for two levels, 8.5 cm for three levels and 10.0 cm for four levels of fusion. The complications were retroperitoneal hematoma in two cases, pneumonia in one case and transient lumbosacral plexus palsy in three cases.
Conclusion
The mini-open lateral approach is simpler & safer than XLIF or DLIF with very short learning curve. Trial of mini-open lateral approach would be helpful before trial of XLIF or DLIF. However, special attention is required to complications such as transient lumbosacral plexus palsy.