Proceedings of the NASS 19th Annual Meeting / The Spine Journal 4 (2004) 3S–119S 5S

Fig. 1. Mean (�50) implant load vs. load applied to motion segment.

repeated with silicone to simulate fibrous tissue ingrowth to model thechronic implantation state. Statistical analysis was conducted using a two-way repeated measures ANOVA.RESULTS: The proportion of load through the implant varied in responseto the load applied to the motion segment (Fig. 1). At applied loads of250N, 37% of the load was experienced by the implant, whereas at loadsof 1500N, a significantly lower proportion (22%) of the load through theimplant was found (p�0.01). The addition ofsimulatedfibrous tissue resultedin a small, but significant interaction effect (p�0.01) between load leveland silicone with a 6% greater proportion of load through the implant athigh loads. The proportion of the load through the implant was independent ofload rate.CONCLUSIONS: This study demonstrated load sharing between theannulus/facets and nucleus prosthesis in annulus sparing replacementtype spinal arthroplasty. The proportion of load between these structuresvaries depending upon the applied load and interposed soft tissue. As appliedloads increase, a greater proportion of the loads pass through the annulus/facets. This behavior suggests a protective effect for the device at highapplied loads which may prevent device subsidence and fatigue failure.The interposed fibrous soft tissue effect was consistent with a prior studywhich indicated greater device load sharing with increased device stiffness.The load sharing found in this study may deviate in vivo with varyingspinal alignment.DISCLOSURES: Device or drug: Intervertebral Prosthetic Disc.Status: Investigational/Not approved.CONFLICT OF INTEREST: Author (GB) Stockholder: Author ownsstock in Dynamic Spine, Inc.; Author (GB) Board Member: Author is boardmember of Dynamic Spine, Inc.

doi: 10.1016/j.spinee.2004.05.0063:116. Gene expression associated with pseudarthrosis repair by OP-1or autograft in a nicotine exposed rabbit modelAndrew White, MD1, Daniel Prince1, Todd Albert, MD2, Alan Hilibrand,MD2, Alexander Vaccaro, MD2, Jonathan Grauer, MD1; 1YaleUniversity, New Haven, CT, USA; 2Thomas Jefferson University,Philadelphia, PA, USA

BACKGROUND CONTEXT: Osteogenic protein 1 (OP-1), also knownas bone morphogenetic protein 7 (BMP-7), is an osteoinductive recombinantprotein that has achieved a 100% fusion rate in an established rabbit fusionmodel, even in the presence of nicotine. The application of OP-1 to challeng-ing scenarios such as pseudarthrosis repair may also foster fusion success.Previously, fusion outcomes with and without OP-1 were correlated withthe cytokine gene expression profile of the developing rabbit spinal fusion.The increased expression of osteogenic and angiogenic cytokines in re-sponse to OP-1 may be responsible for the improved rate of solid fusionwith OP-1 as compared to autograft. Additionally, fusion success ratesand the expression of similar cytokines are both decreased in nicotine-exposed rabbits. These observations lead to the hypothesis that OP-1 wouldbe more effective than autograft for pseudarthrosis repair in a nicotine-exposed rabbit model and that this effect may be attributable to OP-1’sinduction of cytokines otherwise inhibited by nicotine.

2:255. Sagittal spinopelvic alignments standing and in an intraoperativeprone positionRoger Jackson, MD1, Karen Behee, RN2, Anne McManus, RN2; 1NorthKansas City Hospital, North Kansas City, MO, USA; 2Midwest SpineFoundation, North Kansas City, MO, USA

BACKGROUND CONTEXT: Studies of patient positioning on variousframes and tables for spinal alignments have largely focused on lumbaror lumbosacral lordosis. Measurements for thoracic kyphosis have beenminimal and there are no data for combined lumbopelvic (L/P) lordosisand pelvic alignment around the hips, as it relates to intra-operative patientpositioning, pelvic morphology and lumbar lordosis.PURPOSE: Radiographic comparisons of sagittal spinopelvic alignmentsstanding and in an intra-op. prone position were done to determine if thereare significant differences. If so, what is the implication for patient care?STUDY DESIGN/SETTING: Prospective radiographic comparisons ofmeasurements for thoracic kyphosis, lumbopelvic (L/P) lordosis and pelvicmorphology standing and after prone positioning at surgery on a Jacksontable with contoured chest pads supporting the ribs laterally.

PATIENT SAMPLE: Twenty-one surgical patients (18 F, 3 M, avg. age46 years) were studied. Each had standing pre-op 36 inch PA and lateralfilms taken of the spine. The patients had the following primary diagnoses:degenerative spondylo (9), lytic spondylo (7), degenerative lumbar scolio-sis with stenosis (4) and adolescent idiopathic scoliosis (1).OUTCOME MEASURES: Lumbopelvic lordosis was measured using thepelvic radius technique.METHODS: After general anesthesia and prone positioning on the Jacksontable equipped with adjustable contoured chest pads, intra-op thoracic andlumbar 14×17 inch lateral films were taken and compared to the pre-opstanding lateral film for each patient. All of the radiographs, except theintra-op thoracic films, showed both hips. T4–T12 kyphosis was measuredby the Cobb method. The L/P lordosis was measured using the PelvicRadius (PR) technique by establishing a line from the mid-point betweenboth hips to the posterior superior corner of S1 (PR line). Distal L/P lordosiswas the angle from the PR line to the line along the superior endplates ofL5 and L4 (PR-L5 and PR-L4 angles, respectively). Measurements werealso made for pelvic morphology (pelvic incidence and pelvic lordosis bythe PR-S1 angle). Pelvic lordosis, determined by the PR technique, is thecontribution of the pelvis to lordosis. Pelvic lordosis is inversely propor-tional to the pelvic incidence. The PR-L5 angle is the combined pelviclordosis (PR-S1 angle)�the L5-S1 Cobb angle for segmental lordosis. ThePR-L4 angle is the pelvic lordosis (PR-S1 angle)�the L5-S1 and L4–L5Cobb angles for segmental lordosis.RESULTS: Standing vs. prone mean measurements were: T4–T12 kypho-sis, �33� vs. �39�; PR-L5 angle, �37� vs. �47�; and PR-L4 angle, �52�

vs. �65� (p .003 for all measurements). Measurements for pelvic morphol-ogy were not different: pelvic incidence, 65� vs. 64� and pelvic lordosis,�22� vs. �23�. The increase in L/P lordosis occurred primarily at thelumbosacral level and appeared to be associated with anterior pelvic rotationaround the hips. Measurement of L/P lordosis did not require direct identifi-cation of the S1 endplate and this proved to be very helpful clinically.CONCLUSIONS: Patients positioned prone on the Jackson table usingthe contoured chest pads maintained or increased their thoracic kyphosis.The distal L/P lordosis was also significantly increased. Pelvic morphologydid not change between films for the same patient, as expected. The reportedincrease in sagittal spinal alignments may be necessary for some surgicalpatients, such as those with decreased lumbar lordosis and/or thoracickyphosis.DISCLOSURES: No disclosures.CONFLICT OF INTEREST: Author (RJ) Other: Royalties: OrthopedicsSystems, Inc.

doi: 10.1016/j.spinee.2004.05.007