by axis off by 3 mm in either AP or lateral plane) was 43.2%, whereas the

mean ingrowth of prostheses inserted in ‘‘ideal position’’ within 3 mm of

the optimal prosthesis axis in both planes was 46.4%. The definition of

successful biologic ingrowth in the extremities for total joint replacement

is porous ingrowth over 30%, which was achieved in 58/68 (85.3%) of

vertebral end plates.

CONCLUSIONS: The porous ingrowth TiCaP bioactive technology per-

mits osseointegration despite nonideal positioning. The surgeon’s technical

shortcomings to place the prosthesis in ideal position were more than com-

pensated for as 85.3% of the components were successfully ingrown and

biologically fixed to the vertebral trabeculae at the time of explantation.

There were no cases of osteolysis or biomaterial failure encountered in this

retrieval study.

FDA DEVICE/DRUG STATUS: Porous Coated Motion Device: Investi-

gational/not approved; Charite: Approved for this indication; Acroflex:

Approved for this indication.

CONFLICT OF INTEREST: No conflicts.

doi: 10.1016/j.spinee.2006.06.222

P77. A Comparative Biomechanical Analysis of Cervical versus

Lumbar Rotational Stability in Preparation for Cervical and

Lumbar TTDR

John Sefter, DO1, Bryan Cunningham, MSc2, Nianbin Hu, MD2,

Helen Beatson, BSc2, Paul McAfee, MD1; 1Spine and Scoliosis Center,

Towson, MD, USA; 2Union Memorial Hospital, Baltimore, MD, USA

BACKGROUND CONTEXT: N/A.

PURPOSE: The current study was undertaken to evaluate the structural

role of the intervertebral disc, comparing rotational stability of the cervical

spine to the lumbar spine, and quantifying the relative contribution of the

annulus to arthroplasty stability.

STUDY DESIGN/SETTING: An in-vitro biomechanical study.

PATIENT SAMPLE: N/A.

OUTCOME MEASURES: Biomechanical kinematic data.

METHODS: Fresh-frozen human cadaveric spines (n56, C5-C6) and

(n56, L4-L5) were used for the biomechanical testing and underwent

the following graded instability conditions: 1) Intact; 2) Resection of

ALL, annulus, disc, PLL as if in a clinical setting; 3) A more radical

annulus resection; 4) Entire 360 degree annular resection; and 4) insertion

of the respective unconstrained type disc replacement. Using a six degree

of freedom spine simulator, unconstrained pure moments of 68.0Nm

(lumbar) and 63.0Nm (cervical) were used for axial rotation, flexion-

extension, and lateral bending testing, with quantification of the operative

level range of motion (ROM) and neutral zone (NZ).

RESULTS: The Neutral Zone total degrees of rotation for the cervical

spine was as followsd1) Intact cervical54.63 degrees, 2) Discectomy

for TDR55.25 degrees, Radical Discectomy55.82 degrees, and then in-

sertion of a PCM TDR restored the Neutral zone back to 3.76 degrees. This

is in great contrast to the lumbar spine where the intact total ROM was 4.3

degrees, and after preparation for clinical lumbar TDR the ROM more than

doubled up to 9.68 degrees. Radical discectomy with removal of the lateral

annulus further destabilized the motion segment up to 14.76 degrees. Im-

plantation of the lumbar Charite never restored the motion segment back to

the rotational stability of the intact segment achieving a range of 120% to

140% rotational ROM compared with the intact condition. This rotational

instability proved to be additive as a two-level Charite TDR resulted in be-

tween 240% and 260% increase in rotational instability compared with the

intact condition. The lateral masses are the key difference in the cervical

spine where the combined joint surface contact area is greater than the

cross sectional area of the cervical disc.

CONCLUSIONS: The capsular ligaments and lateral masses clearly are

the primary stabilizers of rotational stability in the cervical spine. The im-

plications in the cervical spine for TDR clearly show that even for a radical

discectomy and uncovertebral resection, a TDR can safely restore the sta-

bility of the cervical spine back to the physiologic neutral zone. However,

in the lumbar spine the annulus fibrosis, ALL, and PLL are the three most

important primary stabilizers in rotation, and all three are compromised in

lumbar TDR. Even with normal preparation of the lumbar disc for TDR,

the Charite does not return the rotational stability back to the physiologic

neutral zone 120% to 140% rotation compared with intact. The multilevel

TDR lumbar implantation has an additive destabilizing effect as two-level

annulus lumbar resection results in 240% to 260% rotation (with intact

being normalized to 100%). Clearly the lumbar spine is more prone to be-

come out of balance and rotationally unstable with multilevel TDR com-

pared with cervical TDR.

FDA DEVICE/DRUG STATUS: Porous Coated Motion Device: Investi-

gational/not approved; Charite Disc Replacement: Approved for this

indication.

CONFLICT OF INTEREST: No conflicts.

doi: 10.1016/j.spinee.2006.06.223

P78. Evaluation of the Efficacy of rhBMP-2 to Overcome

Pseudoarthrosis in a New Zealand White Rabbit Posterolateral

Fusion Model

James Lawrence, MD1, Walid Waked, MD1, Thomas Gillon, MD1,

Andrew White, MD1, Christopher Spock1, Debdut Biswas, BA1, Todd

J. Albert, MD2, Jonathan Grauer, MD1; 1Yale University, New Haven, CT,

USA; 2Thomas Jefferson University, Philadelphia, PA, USA

BACKGROUND CONTEXT: Lumbar fusion surgery is associated with

defined limitations. For example, pseudarthrosis continues to be a problem

with posterolateral lumbar fusions, even with autogenous bone graft (the

current gold standard) and modern instrumentation. This is particularly

a problem in certain situations such as nicotine exposure or prior failed

fusions. Therefore, much research is being done to investigate the role of

potential bone graft alternatives. Recombinant human bone morphogenetic

protein-2 (rhBMP-2) has been shown to be a potent osteoinductive factor.

High fusion rates have been shown in multiple preclinical and clinical

studies.

PURPOSE: To use an established preclinical pseudoarthrosis repair model

to evaluate the ability of two different formulations of rhBMP-2 to induce

fusion in comparison to autograft and nongrafted controls.

STUDY DESIGN/SETTING: Preclinical rabbit posterolateral lumbar

pseudarthrosis repair model.

PATIENT SAMPLE: New Zealand White Rabbits.

OUTCOME MEASURES: Fusion rates as assessed by manual palpation

and histologic analysis.

METHODS: Seventy-four New Zealand white rabbits underwent postero-

lateral lumbar fusion with autograft from one iliac crest. To maximize the

incidence of pseudarthroses, nicotine was administered to all rabbits via

subcutaneous mini-osmotic pumps. At 5 weeks, the animals were taken

back to the operating room and fusion beds were explored and evaluated.

If fusion was identified, the animals were excluded from the study. If pseu-

darthrosis was identified, they were re-decorticated and randomized to re-

ceive one of four bone graft materials: no additional graft, autograft from

the second iliac crest, or one of two different formulations of rhBMP-2

(Medtronic Sofamor Danek, Memphis, TN): absorbable collagen sponge

(ACS) or hydroxyapatite-tricalcium phosphate compression-resistant

matrix (CRM). Of the two BMP formulations, the first was the form com-

mercially marketed as INFUSE Bone Graft (1.5 cc of 1.5 mg rhBMP-2 / cc

ACS per side). The second was the AMPLIFY Matrix formulation, which

is being developed (1.5 cc of 2.0 cc rhBMP-2 / mL CRM per side). At the

second surgery, the subcutaneous nicotine pumps were reinstated. At 10

weeks, the rabbits were sacrificed and fusions were assessed with manual

palpation and histology. Representative specimens were assessed with

radiography or computed tomography.

RESULTS: Four rabbits (5.4%) were lost to complications. Sixty-six

(97%) had pseudarthroses on exploration at 5 weeks, and repair was

attempted. By manual palpation at 10 weeks, there were 1 of 17 (5.9%)

pseudarthroses that received no graft fused, 5 of 17 (29.4%) pseudarthroses

120S Proceedings of the NASS 21st Annual Meetings / The Spine Journal 6 (2006) 1S–161S

that received autograft fused, 34 of 34 (100%) pseudarthroses that received

rhBMP-2 (with either ACS or CRM) fused. Plain radiographs, computed

tomography, and histology further characterized the fusion masses.

CONCLUSIONS: This study used an established rabbit pseudarthrosis

repair model with control fusion rates similar to those of prior research.

Recombinant human bone morphogenetic protein-2 (in either of the two

carriers studied) was able to induce fusion in all rabbits (100%) in this

challenging preclinical posterolateral lumbar model.

FDA DEVICE/DRUG STATUS: Infuse Bone Graft: Investigational/not

approved; Amplify Matrix: Investigational/not approved.

CONFLICT OF INTEREST: No conflicts.

doi: 10.1016/j.spinee.2006.06.224

P79. L2 Single Segmental Wedge Osteotomy for Correction of Severe

Kyphotic Deformity in Ankylosing Spondylitis

Jiayong Liu, MD1, Nabil A. Ebraheim, MD1, Steve P. Haman, MD1, Chris

G. Sanford, Jr., BS1, Hui-Lin Yang, MD2; 1Medical University of Ohio,

Toledo, OH, USA; 2The First Affiliated Hospital of SuZhou University,

SuZhou, Jiangsu, China

BACKGROUND CONTEXT: There is controversy about single segmen-

tal or multiple segmental wedge osteotomies for correction of severe

kyphotic deformity in ankylosing spondylitis. There are no reports on L2

single segmental wedge osteotomy for correction of severe kyphotic defor-

mity in ankylosing spondylitis.

PURPOSE: To evaluate the effect of single segmental wedge osteotomy

for correction of severe kyphotic deformity in ankylosing spondylitis.

STUDY DESIGN/SETTING: A retrospective study on patients with

severe kyphotic deformity from 1998 to 2002.

PATIENT SAMPLE: Fifteen patients with severe kyphotic deformity

who have been treated with L2 single segmental wedge osteotomies.

OUTCOME MEASURES: Cobb’s angle and the height of the patient

were measured before and after the operation. Neurological evaluation

on all patients was also conducted.

METHODS: Before surgery, we simulated the wedge cut that the patient

would receive on X-ray film from preoperative radiographs. The patient

received general anesthesia and was laid in the prone position on an ad-

justable operating frame in a reverse-V shape. All procedures were per-

formed by monitoring somatosensory-evoked potentials. The lumbar

spine was exposed through approximately a 15-cm midline incision over

the center of the L2 spinal process. Pedicle screws were inserted into

one segment above and below the osteotomy level. Subperiosteal dissec-

tion was performed to expose the posterior elements as far laterally as

the transverse processes. A 3.5-4.5 cm cut was made into the fused spinal

process and was continued in a V-shape to the anterior column of the L2

vertebrae. This approach included laminectomy, facetectomy, and resec-

tion of both L2 pedicles. The posterior and bilateral cortices were then

cut down into the body using a small chisel (less than 1 cm in width) with

the nerve clearly seen and protected. Approximately 1/4–1/5 of the ante-

roposterior diameter remained uncut during this process. Wire was in-

serted through the spinal processes above and below the osteotomy

level. The operating frame was slowly extended while at the same time

the wire was gently tightened. The neurological and vascular status as well

as the vital signs of the patient had to be closely monitored continuously

during this entire process. Adverse effects from any of these areas deter-

mined to what extent the procedure could be carried out. Once the correc-

tion is complete, a pedicle screw is tightened on the rod to complete

fixation. Postoperative management included that patients were kept in

a supine to a 90 � lateral position for 2 months after surgery. During this

time, the patient could only move if the body was turned as a whole with-

out any twisting of the spine.

RESULTS: The average correction achieved ranged from 25 to 30

degrees. The average increase of the patients’ height was 18 cm. There

was no mortality, nor were there any major neurological complications.

CONCLUSIONS: L2 single segmental wedge osteotomy can effectively

and safely correct severe kyphotic deformity of the thoracolumbar spine

caused by ankylosing spondylitis.

FDA DEVICE/DRUG STATUS: CCD Pedicle Screw System: Approved

for this indication.

CONFLICT OF INTEREST: No conflicts.

doi: 10.1016/j.spinee.2006.06.225

P80. Results of Surgical Treatment for Metastatic Disease Involving

the Sacrum

Iman Feiz-Erfan, MD1, Remi Nader, MD2, Dima Suki, PhD3, Ehud Mendel,

MD3, Indro Chakrabarti, MD3, Ziya Gokaslan4, Laurence Rhines, MD3;1Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center,

Phoenix, AZ, USA; 2Greenwood Leflore Hospital, Greenwood, MS, USA;3University of Texas M.D. Anderson Cancer Center, Houston, TX, USA;4Johns Hopkins University, Baltimore, MD, USA

BACKGROUND CONTEXT: Hematogenous metastases to the sacrum

can produce significant symptoms.

PURPOSE: Since the role of surgery for this condition has been poorly

defined, the purpose of this paper is to delineate indications, complications,

clinical outcome, and survival of these patients after surgery.

STUDY DESIGN/SETTING: Retrospective chart review.

PATIENT SAMPLE: Twenty-five consecutive patients treated surgically

for hematogenously disseminated metastatic disease to the sacrum between

1993 and 2005.

OUTCOME MEASURES: Overall and sacral progression-free survival,

semi-quantitative outcome of pain on a three-tiered scale (same, better,

worse), modified Frankel scale for ambulatory function, incidence and type

of postoperative complications, surgical mortality within 30 days after

surgery.

METHODS: Extraction of consecutive patients harboring sacral meta-

static disease from a prospectively collected surgical database with retro-

spective analysis of their medical records.

RESULTS: Surgical indications included symptom palliation (n524),

oncological control in cases where the sacral metastasis was the only site

of disease (n512), diagnosis (n52), and overt spinal instability (n53). The

majority of symptoms were related to refractory pain (n524) and inconti-

nence (n57). Tumor resection was performed in 23 cases (gross total in

12, subtotal in 11). Among the cohort of gross total resection, 3 were re-

sected en bloc and the remainder were resected piecemeal. Instrumentation

was applied in 12 cases (modified Galveston technique). Sixteen proce-

dures were done after failure of prior nonoperative measures. Primary sites

included kidney (n515), prostate (n53), melanoma/sarcoma (n53),

breast, colon, nasopharynx, and thyroid (each n51). Complications

occurred in 11 patients. These consisted mainly of cerebrospinal fluid leaks

(n53), deep venous thrombosis (n52), wound infections (n52), and dis-

tant site infections (pneumonia, cholecystitis, urinary tract and line infec-

tion) (n54). There was no surgical mortality. Overall survival averaged 19

months (range 1–86 months). Sacral progression-free survival averaged 11

months (range 0.5–86 months). Patients in whom the sacral metastasis was

the sole site of disease had a mean overall survival of 19 months. Those

with multiple metastatic sites had an overall survival of 17 months. At last

follow-up, all but 3 patients were dead of disease. Sacral progression

occurred in 10 (no sacral progression was noted after en bloc resection),

and distant progression occurred in 18 patients. Postoperatively, pain im-

proved in 21, and was unchanged in 3. Postoperative ambulatory function

improved in 8, worsened in 3 (due to disease progression), and remained

unchanged in 14. Among patients with kidney cancer, the mean overall

survival was better in patients in whom the sacrum was the sole site of dis-

ease (24 vs. 8 months), and was worse for histologies with sarcomatoid

features (5 vs. 19 months).

CONCLUSIONS: Primary indications for surgical intervention for

metastatic disease to the sacrum included palliation of symptoms that were

refractory to maximal nonoperative measures or where no effective

121SProceedings of the NASS 21st Annual Meetings / The Spine Journal 6 (2006) 1S–161S