were operated of which 14 were single levels and 20 double levels (L2-3-

2; L3-4–9; L4-5–22; L5S1–1). The duration of the symptoms varied from

18 months to 25 years.

OUTCOME MEASURES: Patients were asked to complete self-adminis-

tered clinical questionnaires. These questionnaires were the Zurich Claudi-

cation Questionnaire, Oswestry Disability Index, and SF-36.

METHODS: Questionnaires were collected preoperatively, and at 3, 6,

and 12 months after surgery in the follow-up clinic.

RESULTS: 54% of patients reported clinically significant improvement in

their symptoms, 33% reported clinically significant improvement in phys-

ical function, and 71% expressed satisfaction with the procedure. 29% of

the patients required caudal epidural after 12 months postoperatively for

recurrence of their symptoms of neurogenic claudication.

CONCLUSIONS: The results of this prospective observational study in-

dicate that X Stop offers significant short-term improvement over a 1-year

period. It is a safe, effective, and less invasive alternative for treatment of

lumbar spinal stenosis. Our results, however, are less favorable than the

previous multi-center, randomized study.

FDA DEVICE/DRUG STATUS: X Stop: Approved for this indication.

CONFLICT OF INTEREST: Author (MS) Grant/Research Support: St.

Francis Medical Technologies, Inc.

doi: 10.1016/j.spinee.2006.06.308

P50. Disc Space Preparation in Transforaminal Interbody Fusion:

A Comparison of Open and Minimally Invasive Technique

Peter Grossi, MD, Louis Radden, DO, Pradhan Ashtoush, MD,

Isaacs Robert, MD; Duke University, Durham, NC, USA

BACKGROUND CONTEXT: The main determinant for arthrodesis after

interbody fusion is adequate disc removal and end plate preparation.

Cadaver studies have demonstrated that the graft fusion area should be

significantly greater than 30% of the vertebral body area to ensure ade-

quate bone-graft contact to prevent subsidence and obtain a secure and sta-

ble arthrodesis. More recent studies examining postoperative imaging have

demonstrated that after a unilateral posterior transforaminal lumbar inter-

body (TLIF) approach, 56% of the end plate cross-sectional can be

exposed for fusion. Early reports suggest that, although technically more

demanding, TLIF utilizing minimally invasive spine techniques

(MIS-TLIF) results in significantly less intraoperative blood loss and sur-

gical morbidity without a significant change in operative time when com-

pared with standard open TLIF. Furthermore, although these reports

suggest that MIS-TLIF affords comparable surgical exposure, disc

removal, end plate preparation, and placement of interbody graft, these

measures have never been quantitatively compared in a cadaver model.

PURPOSE: To compare standard open and MIS approaches to the lumbar

spine to determine if comparable discectomy and end plate preparation can

be obtained with MIS technique.

STUDY DESIGN/SETTING: MIS-TLIF and open TLIF approaches were

performed in 12 lumbar segments in cadavers. The spinal segements were

then analyzed to determine the extent of discectomy and end plate

preparation.

PATIENT SAMPLE: Twelve lumbar spinal levels in four fresh human

cadavers.

OUTCOME MEASURES: Comparison of extent of end plate preparation

of the rostral and caudal end plates of lumbar segements measured as per-

cent of bony end plate exposed relative to total cross-sectional disc space

area.

METHODS: Standard open TLIF and MIS-TLIF exposures were

performed in alternating segments of 12 lumbar disc spaces in four human

cadavers from L3-4 to L5-S1 (six MIS, six open). Identical technique and

instruments were utilized regardless of approach. In each case, a unilateral

facetectomy was followed by a radical discectomy; the only exception was

that in MIS levels, a fixed 22-mm MIS portal was used. An effort was

made to perform the maximal possible discectomy in each case. After dis-

cetomy, the spines were removed from the body. The segments were then

cut through the disc space and digitally photographed. The extent of disc

removal and end plate preparation was then measured and analyzed by two

observers blinded to the approach using data analysis software, to quantify

the extent of disc removal and bony end plate exposure.

RESULTS: MIS technique afforded an exposure of 74.0% (69.1%,

range555-88%) of the end plate, whereas open technique allowed

78.5% (610.3%, range561–96%). No significant advantage was noted

with either open or MIS approaches (p5.37). With both techniques, the

contralateral dorsal corner was the most difficult region to reach, and in

all cases there was greater than 50% of the bony end plate exposed and

prepared for graft placement.

CONCLUSIONS: Although clinical reports suggest that MIS-TLIF af-

fords comparable surgical exposure, disc removal, and end plate prepara-

tion, when compared with standard open technique, this has never been

confirmed in a cadaver model. Herein we report that for single-level

interbody fusion, with respect to disc space preparation for fusion, an open

approach offers no significant advantage compared with an identical MIS

technique in a cadaver model. With either technique, adequate disc space

preparation can be obtained.

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

any applicable devices or drugs.

CONFLICT OF INTEREST: Author (IR) Consultant: DePuy; Author

(IR) Speaker’s Bureau Member: DePuy.

doi: 10.1016/j.spinee.2006.06.309

P51. Aspiration of Osteoprogenitor Cells From the Vertebral Body:

Comparison of Progenitor Cell Concentrations at Different

Aspiration Depths

Robert McLain, MD, Cynthia Boehm, George Muschler, MD; Cleveland

Clinic Foundation, Cleveland, OH, USA

BACKGROUND CONTEXT: While successful spinal fusion is more

likely when the site is augmented with autograft bone, iliac crest graft har-

vest is often associated with complications and persistent pain. Connective

tissue progenitors (CTPs), aspirated from the marrow of the iliac crest and

concentrated with allograft matrix and DBM provide an alternative to au-

tograft harvest. Recent investigations have shown that the vertebral body

provides progenitor cell concentrations superior to those of the iliac crest.

The question remains: how much marrow can be aspirated from the verte-

bral body before the progenitor cell population is depleted?

PURPOSE: This study assesses whether the progenitor cell concentration

is maintained as multiple aspirates are drawn from the same vertebral

reservoir.

STUDY DESIGN/SETTING: After IRB approval was obtained, 12 adults

undergoing posterior lumbar fusion and pedicle screw instrumentation

were recruited for this study. Each underwent their indicated operation

in the usual fashion. As pedicle screw pilot holes were created, transpedic-

ular aspiration of connective tissue progenitor cells was carried out using

a custom probe.

PATIENT SAMPLE: Adult men and women undergoing spinal surgery

for degenerative disease. Patients were excluded if they had had previous

spinal instrumentation, radiation to spine or pelvis, if they suffered from

any myeloproliferative disorder, or if they took chronic steroid medication,

thyroxin, or chemotherapy.

OUTCOME MEASURES: Histochemical analysis provided the preva-

lence of vertebral progenitor cells relative to depth of aspiration, vertebral

level, age, and gender. Cell count, progenitor cell concentration (cells/cc

marrow), and progenitor cell prevalence (cells/million cells) were

calculated.

METHODS: Bone marrow cells were aspirated directly into 10.0-cc sy-

ringes preloaded with heparinized saline. A smear was made at the time

of each aspiration to confirm the adequacy of the aspirate. 2.0-cc aliquots

were aspirated at four depths: 30, 35, 40, 45 mm, from both the left and

right sides. The number of CTPs in a sample were estimated from the num-

ber of colony forming units (CFUs) expressing alk phos activity in culture.

108S Proceedings of the NASS 21st Annual Meetings / The Spine Journal 6 (2006) 1S–161S

Each sample was cultured for CTP assay at day 6. Alk phos staining was

carried out on day 6. The number of CFUs (8 or more cells/cluster)

expressing alk phos activity provided a quantitative measure of the preva-

lence of CTPs relative to depth of aspiration, vertebral level, age, and gen-

der. Data were analyzed relative to gender, age, site of harvest, and depth

of harvest within the vertebral body. Statistical significance was defined as

p!.05.

RESULTS: Aspirates demonstrated high concentrations of progenitor

cells at the more proximal sites. CTP concentrations were higher at the first

aspiration (30 mm) than at any of the deeper aspirations (p5.05). The con-

centration of CTPs from aspirates 2 and 3 was equal to the mean values for

vertebral aspirates in previous studies. The concentration of CTPs from the

deepest aspirates was significantly lower than from the first aspirate, yet

was equal to established values for iliac crest aspirates.

CONCLUSIONS: The vertebral body is suitable for marrow aspiration.

The concentration of osteogenic progenitor cells declines with serial aspi-

rations along the pedicle axis, but the lowest values were still equal to

values obtained from the iliac crest, considered the standard for harvest

and fusion augmentation.

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

any applicable devices or drugs.

CONFLICT OF INTEREST: Author (RM) Grant/Research Support:

Depuy Spine.

doi: 10.1016/j.spinee.2006.06.247

P52. Transforaminal Lumbar Interbody Fusion With rhBMP-2

and Allograft: Two-Year Prospective Clinical Evaluation of

a Surgical Strategy

Milan G. Mody, MD1, Ramin Raiszadeh, MD2, Rex A.W. Marco, MD1,

Vivek P. Kushwaha, MD1; 1Foundation for Orthopaedic, Athletic &

Reconstructive Research, University of Texas Health Science Center,

Houston, TX, USA; 2La Jolla, CA, USA

BACKGROUND CONTEXT: Circumferential fusion is becoming in-

creasingly popular and has been advocated by many authors to improve

the fusion rates and clinical outcomes of the degenerative lumbosacral

spine. Anterior lumbar interbody fusion (ALIF) with posterolateral fu-

sion provides direct access to the disc via a separate approach but poses

neurovascular risks. Posterior lumbar interbody fusion (PLIF) with pos-

terolateral fusion requires significant retraction of neural elements with

higher incidence of postoperative radiculitis, reduces surface area for fu-

sion, and disrupts the posterior tension band. TLIF allows for a circum-

ferential fusion through a single posterior incision with only slight

retraction of the neural elements, mitigating the neurovascular. To our

knowledge, there are no studies that report the use of recombinant hu-

man bone morphogenic protein (rhBMP-2) and allograft in a TLIF

setting.

PURPOSE: To assess clinical and radiographic outcomes of patients

treated with one or two level posterior instrumented TLIF using allograft

and rhBMP-2 for symptomatic spondylolisthesis or degenerative disc

disease.

STUDY DESIGN/SETTING: This is a prospective, single-arm study

evaluating clinical outcomes from this surgical strategy.

PATIENT SAMPLE: During a consecutive 13-month period, 77 patients

underwent TLIF with rhBMP-2 with simultaneous posterolateral fusions

with allograft.

OUTCOME MEASURES: Patients were followed at 2 weeks and 3, 6,

12, and 24 months after surgery with functional parameters including

the visual analog scale, SF-36, and Oswestry Disability Index (ODI).

METHODS: All procedures were performed by one spine surgeon. Pedicle

screw instrumention provided distraction, and a carbon-fiber curvilinear

cage packed with rhBMP-2 was placed into the disc space after hemifacetec-

tomy and discectomy. Results from follow-up assessments were compared

with preoperative values, and fusion was assessed with static and dynamic

radiographs at the prescribed intervals.

RESULTS: Seventy-one patients (92%) were available for follow-up (mean

16 months; range 6-24 months). A fusion rate of 94% was achieved with

only four pseudoarthroses. At 12 months, 85% and 77% of patients had im-

provement over preoperative ODI and SF-36 measures, respectively. At 24

months, 85% and 81% of patients saw improvement over preoperative ODI

and SF-36 measures, respectively, while 70% of patients had good to excel-

lent outcomes by both ODI and SF-36 measures. There was one wound in-

fection treated with hardware removal and intravenous antibiotics. One

patient had excessive bone growth into the foramen, necessitating surgical

decompression with subsequent excellent clinical outcome. Ten patients

had paresthesias on the side of the TLIF, all of which resolved completely

by 3 weeks.

CONCLUSIONS: The use of rhBMP-2, in combination with posterolat-

eral allograft, can provide a high fusion rate and good clinical outcomes

in a TLIF setting. The cage with rhBMP-2 must be placed anteriorly

enough to avoid overgrowth of bone into the neural foramen, likely re-

lated to the residue of rhBMP-2 at the TLIF entry site. The morbidity

associated with iliac crest bone graft is avoided, with fusion rates ap-

proaching that of a true anterior/posterior circumferential fusion. Compli-

cations were few, with no significant neurologic sequelae from the

placement of a structural graft into the anterior column through a poste-

rior approach.

FDA DEVICE/DRUG STATUS: rhBMP-2: Not approved for this indica-

tion; Carbon fiber cage: Approved for this indication; Pedicle screw instru-

mentation: Approved for this indication.

CONFLICT OF INTEREST: No conflicts.

doi: 10.1016/j.spinee.2006.06.248

P53. Kineflex (Centurion) Lumbar Disc Prosthesis: Two-Year

Results

Ulrich Hahnle, MD1, Ian R. Weinberg, MD1, Malan De Villiers, PhD2;1University of the Witwatersrand, Johannesburg, Gauteng, South Africa;2University of Potchefstrom, Johannesburg, Gauteng, South Africa

BACKGROUND CONTEXT: The Kineflex lumbar disc is an uncon-

strained disc designed to allow accurate placement in advanced degenera-

tive disc disease (DDD). It gives the option of a metal on polyethylene or

metal on metal mechanism.

PURPOSE: To evaluate clinical results at 2 years outcome of patients

treated with the Kineflex disc.

STUDY DESIGN/SETTING: Ongoing prospective, single-center study

using the Kineflex lumbar disc.

PATIENT SAMPLE: Seventy-five consecutive patients who received 100

Kineflex lumbar disc implants have been followed for 2 years. The average

age of the patient was 43 years (range 23–63 years). The primary diagnosis

was degenerative disc disease. Seven patients had undergone previous

fusion operations. Thirty-nine patients underwent an isolated single-level

disc replacement, 25 patients a two-level disc replacement, one patient

a double-level replacement adjacent to a previous fusion, and 7 patients

had a fusion of another level at the time of the index procedure (hybrid

cases).

OUTCOME MEASURES: The patient satisfaction and functional out-

come of treatment was regularly evaluated by use of our own questionnaire

(includes pain scoring, patient satisfaction, and ‘return to work’ time and

rate) as well as the Oswestry Disability Index (ODI) for back pain.

METHODS: Clinical and radiological evaluation was performed preoper-

atively and at set follow-ups (6 weeks, 3, 6, 12, 24 months). Clinical out-

come measures used pain scoring, patient’s satisfaction, return to work

ratio, and the ODI.

RESULTS: Postoperative hospitalization averaged 3.1 days (2 to 8 days).

All patients who were employed before surgery returned to work after

31616.8 days. Two-year clinical outcome was available for 72 of 75 pa-

tients (44 excellent, 17 good, 7 fair, 4 poor). The Oswestry score improved

from 47.8616.0 preoperatively to 14.5615.8, p!.01 at the latest follow-up

questionnaire. The pain score improved from 9.161.4 preoperatively to

109SProceedings of the NASS 21st Annual Meetings / The Spine Journal 6 (2006) 1S–161S