103SProceedings of the NASS 26th Annual Meeting / The Spine Journal 11 (2011) 1S–173S

OUTCOME MEASURES: Clinical outcomes were based on Visual ana-

logue scores (VAS) for back and leg pain, Oswestry disability index (ODI),

Short form-36 (SF-36), North American Spine Society (NASS) scores for

neurogenic symptoms, returning to full function and patient rating of the

overall result of surgery. Radiological fusion was based on Bridwell grad-

ing system.

METHODS: Before surgery, 6 months and 2 years after TLIF, patients

were assessed with clinical outcome measures, and with static and dy-

namic lumbar spine radiographs. Retrospective analysis on the prospec-

tively collected data was then performed by independent assessors.

RESULTS: In terms of demographics, the 2 groups were similar in terms

of patient sample size, age, gender distribution, body mass index and spi-

nal levels operated, with no statistical difference. Perioperative analysis re-

vealed MIS cases have comparable operative duration (Open:181.8 min,

MIS:166.4 min, pO.05), longer fluoroscopic time (Open:17.6s, MIS:49.0s,

p!.05), less intra-operative blood loss (Open:447.4 ml, MIS:50.6 ml,

p!.05) and post-operative drainage (Open:528.9 ml, MIS:0 ml, p!.05).

MIS patients needed less morphine (Open:33.5 mg, MIS:3.4 mg, p!.05)

and were able to ambulate (Open:3.4 days, MIS:1.2 days, p!.05) and be

discharged from hospital (Open:6.8 days, MIS:3.2 days, p!.05) earlier.

At 6 months, clinical outcome analysis showed both groups improving sig-

nificantly (O50.0%) and similarly in terms of VAS, ODI, SF-36, return to

full function and patient rating (pO.05). Radiological analysis showed sim-

ilar grade 1 fusion rates (Open:52.2%, MIS:59.4%, pO.05) with small per-

centage of patients developing asymptomatic cage migration (Open:8.8 %,

MIS:6.0 %, pO.05). There were 1 major complication (Open: myocardial

infarction, MIS: misplaced screw requiring subsequent re-positioning) and

2 minor complications in each group (Open: pneumonia and post-surgery

anaemia, MIS: incidental durotomy and pneumonia). At 2 years, both

groups continued to improve in clinical outcomes compared to the preop-

erative state (pO.05), with 50.8% of Open and 58.0% of MIS TLIF patients

returning to full function (pO.05). Almost all patients have Grade 1 fusion

(Open:98.5%, MIS:97.0%, pO.05) with minimal new cage migration

(open:1.4%, MIS:0%, pO.05).

CONCLUSIONS: MIS TLIF is a safe option for lumbar fusion, and it has

similar operative duration, good clinical and radiological outcomes as

Open TLIF, with additional significant benefits of less perioperative blood

loss, pain, earlier rehabilitation and shorter hospitalization.

FDA DEVICE/DRUG STATUS: Sextant I pedicle screw-rod instrumen-

tation: Approved for this indication; Capstone interbody cage: Approved

for this indication.

doi: 10.1016/j.spinee.2011.08.255

198. Extended Fenestration Surgery in Degenerative Lumbar Canal

Stenosis

Ashwani Singh, MD; New Delhi, India

BACKGROUND CONTEXT: Therapy for degenerative lumbar spinal

canal stenosis remains difficult. Decompression by total laminectomy is

the treatment of choice for central canal stenosis in the lumbar region. It

is critical that sufficient bone is removed to free the nerve roots, but the

extent of decompression should be as small as possible, in order to prevent

postoperative instability. However, too limited a decompression can be ac-

companied by re-growth of bone that affects the long term results. Also to-

tal laminectomy at multiple levels may result in instability of the spine. So

extended fenestration has been described in Japanese literature as a solution

to the limitations of laminectomy.

PURPOSE: To evaluate the clinical results of extended fenestration sur-

gery in degenerative lumbar canal stenosis based on JOA score.

STUDY DESIGN/SETTING: Prospective study.

PATIENT SAMPLE: Fifteen patients of degenerative lumabar canal

stenosis.

OUTCOME MEASURES: On following parameters Improvement in

low back ache, Improvement in leg pain, Improvement in claudication

All referenced figures and tables will be available at the Annual Mee

distance, Neurological improvement: a. Sensory improvement b. Motor

improvement.

METHODS: All patients were operated under general anaesthesia. The

patient was placed in prone position with the abdomen free. Midline skin

incision was given over the affected level. The superior margin of the cau-

dal lamina and the inferior margin of cephalad lamina at the level of the

stenosis was thinned out with a burr and curreted and removed with kerri-

son’s rounger, taking care to preserve at least 5 mm of the pars interarticu-

laris. Ligamentum flavum was dissected from the underlying dura using

a right angle dissector. The undersurface of the spinous process decom-

pressed by a chevron cut to expose the ligamentum flavum completely.

RESULTS: All patients were regularly evaluated over two and half years.

The Japanese Orthopaedic Association (JOA) score increased from 8.90

points before operation to 28.30 points at the time of the study on average.

(p!.005). Surgical outcome was excellent in all patients.

CONCLUSIONS: Extended fenestration surgery is a safe procedure with

predictable outcome. It does not cause spinal instability and can be per-

formed without any sophisticated instruments. Extended fenestration has

a short learning curve as compared to microendoscopic decompression

laminotomy as given in literature. No specialized instrumentation are re-

quired in extended fenestration technique. Results of extended fenestration

technique are comparable to microendoscopic decompression laminotomy.

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

any applicable devices or drugs.

doi: 10.1016/j.spinee.2011.08.256

199. Effect of Minimally Invasive Lumbar Posterolateral Fusion

Using Percutaneous Pedicle Screw on Paravertebral Muscle Change

and Postoperative Residual Low Back Pain

Yoshihisa Kotani, MD1, Kuniyoshi Abumi, MD1, Hideki Sudo, MD2,

Ken Nagahama, MD3, Akira Iwata1, Manabu Ito, MD, PhD4,

Akio Minami, MD2; 1Hokkaido University Hospital, Sapporo, Japan;2Sapporo, Japan; 3Department of Orthopaedic Surgery, Hokkaido

University Graduate School of Medicine, Sapporo, Japan; 4Hokkaido

University Graduate School of Medicine, Sapporo, Japan

BACKGROUND CONTEXT: To minimize the perioperative invasive-

ness and improve the quality of life (QOL), we have performed the mini-

mally invasive lumbar posterolateral fusion (MIS-PLF) with percutaneous

pedicle screw fixation for degenerative spondylolisthesis. The minimum

two-year clinical outcome data demonstarated that the MIS-PLF decreased

the perioperative pain and invasiveness, as well as providing the significant

improvement of chronic LBP parameters and QOL.

PURPOSE: This study investigated the effect of MIS-PLF on paraverte-

bral muscle change and residual low back pain, when compared to conven-

tional open-PLF.

STUDY DESIGN/SETTING: Prospective non-ramdomized clinical

study.

PATIENT SAMPLE: A total of ninety patients received single-level PLF

for lumbar degenerative spondylolisthesis. There were forty-seven cases of

MIS-PLF and forty-three cases of open-PLF. The surgical technique of

MIS-PLF includes 4 cm of main incision and percutaneous pedicle screw-

ing and rod insertion. The posterolateral gutter including the medial trans-

verse process was decorticated and iliac bone graft was performed.

OUTCOME MEASURES: Oswestry-Disability Index (ODI), Roland-

Morris Questionarre (RMQ) and Japanese Orthopaedic Association (JOA)

score and recovery rate.

METHODS: Using MR T2 horizontal images, the outline of multifidus

muscles were traced at the levels of L4/5 and L5/S1 disc. The area of

multifidus muscle was calculated with a computer software and the per-

cent area (%F-up/ preop) at L4/5 and L5/S1 were obtained (%Area4/5,

%Area5/S1). The muscle density was also measured at both levels

using same data series (%Density4/5, %Density5/S1). The correlation

analyses were statistically carried out between those data and age,

ting and will be included with the post-meeting online content.