RESULTS: Of 184 patients, 62 were smokers (22 M, 40F; age 52.8 yrs)

and 122 nonsmokers (45 M, 77F; age 57.5 yrs). Average 12-month Lenke

score across all subsets was 1.07 (smokers 1.08; nonsmokers 1.07). At 24

months, average Lenke score across all subsets was 1.03 (smokers 1.00,

non smokers 1.02). There were no infections, neurologic complications

or plate breakages. One patient, a 59 year-old diabetic male smoker, devel-

oped a pseudarthrosis; at the 6-month follow-up, the patient remained

asymptomatic and declined re-operation.

CONCLUSIONS: The combination of a demineralized bone matrix-local

bone contained within allograft dowels or PEEK spacer resulted in similar

fusion rates (O 97%) for both smokers and nonsmokers at 12 months and

24 months postoperatively.

FDA DEVICE/DRUG STATUS: PEED Spacers: Approved for this indi-

cation; Allograft Dowels: Approved for this indication.

doi: 10.1016/j.spinee.2009.08.415

P155. DBM Use in 2-Level PLIFs: Fusion Comparison of Smokers

and Non-Smokers

W.B. Rodgers, MD, Curtis S. Cox, MD, Edward J. Gerber, MD; Jefferson

City, MO, USA

BACKGROUND CONTEXT: Smoking has been cited to potentiate post-

operative infections and interfere with bone graft incorporation in fusion

procedures. As such, higher pseudarthrosis (non-union) rates have been

historically reported in this population subset.

PURPOSE: Rates of fusion are presented between smokers and non-

smokers, using a commercially available demineralized bone matrix

(DBM) coupled with bone marrow aspirate and local bone in 2-level pos-

terolateral interbody fusion (PLIF) procedures.

STUDY DESIGN/SETTING: Prospective, nonrandomized clinical and

radiographic assessment.

PATIENT SAMPLE: Of our single-site consecutive series of 110 two-

level PLIF patients, 47 smoked at the time of surgery.

OUTCOME MEASURES: Clinical and radiographic measures were pro-

spectively collected and evaluated to assess comorbidities, complications,

and fusion results at 12 and 24 months postop.

METHODS: 110 instrumented, 2-level PLIF procedures were performed

by a single surgeon using a graft composite were prepared from ground la-

mellar bone, supplemented with DBM and posterior iliac crest bone mar-

row aspirate (BMA). The composite was placed in the aperture of PEEK or

machined allograft spacers (to achieve interbody fusion) and along the in-

tertransverse membrane (to achieve posterolateral fusion). Anteroposterior

and lateral flexion and extension radiographs, obtained at three-, six-, and

twelve-months, were evaluated utilizing Lenke’s criteria for intertransverse

fusion and modified Lenke criteria of interbody fusion. Global fusion was

defined as either: Lenke or modified Lenke score of 1; or Lenke score

2þmodified Lenke score 2.

RESULTS: 46 smokers and 62 non-smokers, ranging in age from 33-85

years (average age557.42 years) presented for 12-month follow-up.

Intertransverse/interbody scores for smokers51.89/1.20 and for non-

smokers51.69/1.25. To date, 32 smokers and 40 non-smokers have pre-

sented for 24 month follow-up. Lenke scores for smokers at 24 months

postop were 1.81/1.25; non smokers 1.63/1.18. Similar complication rates

were observed in both groups; 6 re-operations were performed for adjacent

segment disease.

CONCLUSIONS: Smoking is often identified as a contributing factor to

increased pseudarthrosis (non-union) rates in spinal fusion surgeries. The

fusion rates for smokers and non-smokers were 97.8% and 98.4% at 12

months respectively, and 97% and 97.5% at 24 months; no significant dif-

ference was shown between the two groups. Slightly better (intertrans-

verse) Lenke scores were noted in the nonsmokers.

FDA DEVICE/DRUG STATUS: PEEK Spacers: Approved for this indi-

cation; Allograft Dowels: Approved for this indication.

doi: 10.1016/j.spinee.2009.08.416

P156. Rod Derotation vs. Direct Incremental Segmental Translation:

A Biomechanical Analysis

Xiaoyu Wang, PhD1, Carl-Eric Aubin, PhD1, Hubert Labelle, MD2,

Dennis Crandall, MD3; 1Ecole Polytechnique & Sainte-Justine University

Hospital Center, Montreal, Quebec, Canada; 2Sainte Justine University

Hospital Center, Montreal, Quebec, Canada; 3Sonoran Spine Center,

Mesa, AZ, USA

BACKGROUND CONTEXT: Scoliosis is corrected by different maneu-

vers applied to the spine via a mechanical constructs, with rods usually

bent to desired sagittal profile. Basic techniques involve vertebral transla-

tion, rod derotation, direct vertebra derotation, compression and distrac-

tion, and in situ rod contouring. In order to maintain the correction rods

are fully seated and locked into the slot of each implant, making it difficult

to fine-tune the implant-rod relative location and control the force distribu-

tion amongst the implants. Direct incremental segmental translation

(DIST) was proposed to provide a better control on the vertebra location

with respect to the rod. The most distinguishing point of this concept is

the ability to translate each implant toward and fixed on the rod from

any distance and at any angle.

PURPOSE: Compare the forces at the bone-screw interface during scoli-

osis correction using rod derotation vs. DIST.

STUDY DESIGN/SETTING: We analyzed the biomechanics of two in-

strumentation paradigms: rod derotation technique (RDT) vs. a direct in-

cremental segmental translation approach (DIST).

PATIENT SAMPLE: Reduction techniques documented using pre- and

post-op radiographs as well as intra-operative video of surgical maneuvers

of 10 cases were used to develop a model for computer simulation of cor-

rection techniques for scoliosis.

OUTCOME MEASURES: Computer simulation of scoliosis correction.

METHODS: A common curve pattern (thoracolumbar curve) for adoles-

cent idiopathic scoliosis was chosen. Simulations with both the RDT and

Figure. Simulated forces and their orientation at the vertebra-implant connections

for the RDT (a) and DIST (b) techniques. The length of the arrows is proportional

to the forces.

194S Proceedings of the NASS 24th Annual Meeting / The Spine Journal 9 (2009) 1S-205S

DIST techniques were performed using the same patient biomechanical

model built using biplanar X-rays, with same instrumentation levels and

rod shape. The correction maneuvers and resulting effects were analyzed

and compared.

RESULTS: The vertebra position relative to the rod for the DIST is deter-

mined by 5 independent variables (position, orientation) vs. 2 for the RDT;

thus increasing the possible correction of the connected vertebra. The

DIST allows the spine deformity to be reduced by either gradually pulling

the spine towards the rod through helical connections or translating it by

pivoting the posts. Load at the vertebra-implant connection was on average

18% lower for the DIST, and better distributed (lower STD).

CONCLUSIONS: The direct incremental segmental translation approach

allows more control with better load sharing amongst implants. SIGNIFI-

CANCE: This analysis provides insight into the different biomechanical

effects of the 2 instrumentation paradigms.

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

any applicable devices or drugs.

doi: 10.1016/j.spinee.2009.08.417

P157. An Anatomical Study which Describes the Relationship of the

Pedicle Center to the Mid-Lateral Pars (MLP) in the Lower Lumbar

Spine as a Guide to Pedicle Screw Placement

Brian Su1, Paul Kim, MD2, Thomas Cha, MD2, Joseph Lee, MD2,

Ernest April, PhD2, Mark Weidenbaum, MD2, Alexander R. Vaccaro, MD,

PhD1; 1The Rothman Institute, Philadelphia, PA, USA; 2Columbia

University, New York, NY, USA

BACKGROUND CONTEXT: Traditional medial-lateral starting points

for lumbar pedicle screws use the facet as an anatomical reference for

all lumbar levels. The facet is often a difficult landmark to use secondary

to degenerative changes and the desire to minimize damage to the facet

capsule in the most cephalad level. These techniques can also result in ped-

icle violation particularly in the lower lumbar spine. Use of the non-ar-

thritic MLP is proposed in this study as an alternative anatomical

reference point for the pedicle center.

PURPOSE: Describe morphometric data of the lower lumbar pedicles, the

unique coronal pedicle footprints of L4 and L5, and their impact on the re-

lationship of the pedicle center to the MLP.

STUDY DESIGN/SETTING: Human Cadaver Study for morphometric

data.

PATIENT SAMPLE: Not applicable.

OUTCOME MEASURES: Not Applicable.

METHODS: Seventy-two pedicles (L3-S1) from embalmed cadaveric

spines were used. Linear and angular dimensions of the pedicle were mea-

sured including the degree of coronal pedicle tilt of L4 and L5. The center

of the pedicle relative to the MLP and relative to the midline of the base of

the transverse process was measured. The axial superior facet angle and

angle of pedicle screw insertion was also measured.

RESULTS: The minimum pedicle width was 10.9 mm and 12.4 mm and

the coronal pedicle tilt was 36 and 55 for L4 and L5 respectively. A clas-

sification of two types of L5 pedicles relevant to pedicle center location

was developed. In the medial-lateral direction, the pedicle center is

2.9 mm lateral to the MLP at L3 and L4. At L5, it is 1.5 mm and

4.5 mm lateral to the MLP for a Type I and Type II pedicle respectively.

In the superior-inferior direction, the pedicle center is 1 mm superior to

the midline of the transverse process base for all lower lumbar levels. Sig-

nificant differences between a Type I and II L5 pedicle were a larger ped-

icle width and distance of the pedicle center to the MLP for a Type II

pedicle. The difference between the axial pedicle screw insertion angle

and anatomic superior facet angles was 8 from L4-S1.

CONCLUSIONS: The MLP is a reliable anatomic reference point for the

center of the pedicle in the lower lumbar spine. Consideration needs to be

taken when inserting pedicle screws at L4 and L5 because of the degree of

their coronal tilts and unique pedicle footprints. It is important to distin-

guish a Type I from Type II L5 pedicle as a Type II pedicle is wider,

has a more lateral pedicle center relative to the MLP, and has the potential

for lateral screw placement while still remaining within the pedicle.

Figure.

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

any applicable devices or drugs.

doi: 10.1016/j.spinee.2009.08.418

P158. The Surgical Approach to the Cervico-Thoracic Junction: Can

a Standard Smith-Robinson Approach Be Utilized?

Woojin Cho, MD, PhD1, Takeshi Maeda, MD, PhD2, Yung Park, MD,

PhD3, Jacob Buchowski, MD, MS1, K. Daniel Riew, MD1; 1Washington

University School of Medicine, St, Louis, MO, USA; 2Spinal Injuries

Center, Fukuoka City, Japan; 3Yonsei University School of Medicine,

Seoul, South Korea

BACKGROUND CONTEXT: A number of techniques for exposing the

anterior cervico-thoracic junction have been described. However most

are associated with significant morbidity.

PURPOSE: There are few reports that describe techniques for determin-

ing when a standard Smith-Robinson approach is adequate and when

a more invasive approach, such as a sternal splitting approach is necessary.

We undertook this study to help clarify this issue.

STUDY DESIGN/SETTING: Case Series Report.

PATIENT SAMPLE: The records and radiographs of all patients who had

undergone anterior cervico-thoracic arthrodesis to T1 or below by a single

surgeon at an academic institution were evaluated by independent

surgeons.

OUTCOME MEASURES: Descriptive Obsevational Study.

METHODS: The senior author’s technique for preoperatively determining

whether a standard Smith-Robinson approach could be utilized to expose

the intended caudal segment was based on preoperative lateral x-rays. A

line was drawn from the intended skin incision site to the top of the ma-

nubrium (at the suprasternal notch) to the level of the disc space. This line

represented the trajectory of the approach. If it appeared to allow adequate

195SProceedings of the NASS 24th Annual Meeting / The Spine Journal 9 (2009) 1S-205S