61SProceedings of the NASS 24th Annual Meeting / The Spine Journal 9 (2009) 1S–205S

OUTCOME MEASURES: The radiological outcome was evaluated on

anteroposterior, lateral, and flexion-extension radiographs. Fusion was de-

termined when bony trabecular continuity between the vertebral bodies

was present. Pain was graded using Visual Analog Scale (VAS) scores

(score range 0-10, with 0 reflecting no pain) and functional outcomes were

measured with Oswestry Disability Index (ODI) scores and return-to-work

status.

METHODS: The medical records and radiographs of patients who under-

went LIF with either anterior (ALIF) or transforaminal approach (mini-

TLIF) were reviewed retrospectively. In our study, the definition of ASD

included symptomatic and radiologic ASD. ASD with radiographic evi-

dence on plain X-rays without clinical symptoms was defined as radiologic

ASD, whereas newly developed and aggravated ASD with clinical symp-

toms requiring operation, it was symptomatic ASD.

RESULTS: Radiologic ASD was found in 7 out of 82 patients (8.5%): 2

(4.3%) patients at L4-5 level and 5 (13.9%) patients at L5-S1 level after

mean follow-up periods of 69.5 months and 66.4 months respectively.

Symptomatic ASD was found in 1 (2.2%) patient at L4-5 level and 1

(2.8%) patient at L5-S1 level. Within the patients treated L4-5 level, one

had asymptomatic ASD such as spinal stenosis with angular instability,

and the other one showed symptomatic ASD such as disc collapse with in-

stability at caudal level but refused to fuse. In patients treated L5-S1 level,

one patient showed symptomatic ASD such as spinal stenosis without in-

stability and he underwent decompressive laminectomy. The other 4 pa-

tients d who had angular instability, retrolisthesis, disc collapse, and

degenerative scoliosis d had no clinical symptoms related with radiologic

ASD. Comparing to the reported rate of developing ASD after spinal fu-

sion for degenerative disc disease, which varies 14% to 100%, the rate

of developing ASD with isthmic spondylolisthesis is found lower.

CONCLUSIONS: ASD is a relatively common finding associated with in-

strumented lumbar fusion. However, our results suggest that ASD may

happen in a relatively lower incidence with adult low-grade isthmic spon-

dylolisthesis compared to other degenerative lumbar spinal disease and it is

less likely to affect the adjacent segment unlike degenerative disease.

FDA DEVICE/DRUG STATUS: This abstract does not discuss or include

any applicable devices or drugs.

doi: 10.1016/j.spinee.2009.08.143

118. Radiographic Outcomes of the DLIF/XLIF Technique in

Comparison to Other Fusion Techniques for the Treatment of

Degenerative Lumbar Scoliosis

Niraj Patel1, Gilad Regev, MD2, William Taylor, MD2, Yu-Po Lee, MD2,

Steve Garfin, MD3, Choll Kim, MD, PhD2; 1University of California, San

Diego, La Jolla, CA, USA; 2University of California, San Diego, San

Diego, CA, USA; 3UCSD Medical Center, Dept of Orthopaedics, San

Diego, CA, USA

BACKGROUND CONTEXT: The direct lateral approach to the lumbar

spine (DLIF/XLIF) is a relatively new minimally invasive method for per-

forming anterior fusion. Similar to traditional open interbody fusion, this

technique can correct scoliotic deformity by restoring disc height and

alignment of the disc space. A comparison of scoliosis correction using

this less invasive procedure and other anterior and posterior fusion tech-

niques has not been reported on to date.

PURPOSE: Assess the effectiveness of the XLIF/DLIF procedure in cor-

recting lumbar degenerative scoliosis and compare outcomes with postero-

lateral fusion (PLF), anterior lumbar interbody fusion (ALIF) and

transforaminal lumbar interbody fusion (TLIF).

STUDY DESIGN/SETTING: N/A.

PATIENT SAMPLE: X-ray images were collected for 73 patients treated

with the XLIF/DLIF, PLF, ALIF and TLIF techniques. Only patients with

a lumbar Cobb angle greater than 10� were reviewed.

OUTCOME MEASURES: In order to review scoliosis correction, vari-

ous measurements were taken on pre-operative and post-operative AP

and lateral X-rays of the lumbar spine. These include lumbar scoliosis

using the Cobb angle measurement, focal scoliosis at each intervertebral

level, lateral listhesis, global lordosis, focal lordosis/disc angle and disc

height.

METHODS: N/A.

RESULTS: Patients receiving scoliosis correction with the DLIF/XLIF,

PLF, ALIF and TLIF techniques received fusion at an average 3.0, 2.8,

2.8 and 2.4 levels respectively. Global and focal Cobb angle correction

with DLIF/XLIF surgery is shown below in comparison to other fusion

techniques. Global Cobb Angle Correction: DLIF/XLIF(n539 patients):

Pre-op520.2�(610.5�); Correction58.5�(64.6�) PLF(n518 patients):

Pre-op517.0�(69.8�); Correction52.5�(63.1�) ALIF(n58 patients):

Pre-op526.6�(615.0�); Correction57.0�(66.6�) TLIF(n58 patients):

Pre-op517.9�(65.6�); Correction53.0�(63.0�) Focal Cobb Angle Cor-

rection: DLIF/XLIF(n5117levels): Pre-op59.5�(66.4�); Correction5

4.1�(64.7�) PLF(n547levels): Pre-op57.5�(65.7�); Correct-

ion50.9�(62.9�) ALIF(n522 levels): Pre-op58.1�(66.4�); Correction5

2.6�(64.4�) TLIF(n519levels): Pre-op56.3�(65.5�); Correct-

ion51.4�(64.7�) The DLIF/XLIF technique is significantly more effective

than PLF (p!0.001) and TLIF (p!0.05) in correcting global Cobb angle

and is comparable to ALIF. Amongst the 26 DLIF/XLIF patients with lat-

eral radiographic images, little change in mean lumbar lordosis was noted,

but focal lordosis (disc angle) at each vertebral level increased 106% from

4.1�(65.5�) to 8.5�(64.7�). This also resulted in a 72% increase in ante-

rior disc height and a 48% increase in posterior disc height.

CONCLUSIONS: The XLIF/DLIF procedure is comparable to ALIF and

is more effective than TLIF and PLF in correcting lumbar spine deformity

caused by degenerative scoliosis. It produces a greater reduction in both

global Cobb angle and focal Cobb angle than these surgeries and is a less

invasive procedure. It also corrects degenerative changes of the spine by

significantly increasing disc height and disc angle.

FDA DEVICE/DRUG STATUS: XLIF: Approved for this indication.

doi: 10.1016/j.spinee.2009.08.144

Thursday, November 12, 20095:05–6:05 PM

Focused Paper Presentations 3: Diagnostics/Imaging

119. The Efficacy of Motor Evoked Potentials in L5-S1

Transforaminal Lumber Interbody Fusion

Ahmed Aljahwari, MD, Russel Lyons, Shane Burch, MD, Vedat Deviren,

MD1, Sigurd Berven, MD, Serena Hu, MD; University of California, San

Francisco, San Francisco, CA, USA

BACKGROUND CONTEXT: Neurophysiologic monitoring has been

used effectively to detect and prevent spinal cord injury during cervical

and thoracolumbar surgery.However, the ability of these methods to detect

isolated lumbar nerv root is less consistent. Dermatomal SSEP have not

gained wide use as they are technically challenging, lack reliability and

are not instantaneous, requiring extensive signal averaging. EMG is overly

sensitive, with a high incidence of false positives, and has poor positive

predictive value for injury. Evoked EMG may help to prevent injury from

screw malposition but not from other causes, such as neural compromise

related to vascular compromise or nerve retraction. The efficacy of Trans-

cranial Motor Evoked Potentials (TcMEPs) in detecting isolated nerve root

injury for surgery below the conus has been demonstrated recently in lum-

ber corrective osteotomy(Liberman et al Spine June2008).

PURPOSE: to determine the sensitivity and specificity of TcMEPs to de-

tect and predict isolated nerve root injury in selected patients having trans-

foraminal lumber interbody fusion (TLIF) at L5/S1 level.

STUDY DESIGN/SETTING: Retrospective analysis.

PATIENT SAMPLE: 152 patients with TLIF procedure at L5/S1.