Proceedings of the NASS 20th Annual Meeting / The Spine Journal 5 (2005) 1S–189S 179S

METHODS: Disc height was assessed with CT scans which provide com-plete 3D descriptions of the inter-vertebral (IV) space. Accuracy of CT-based measurments were verified in a separate study using a cadavericspine (�0.5% error). An effective disc height was calculated by determiningthe volume of the IV space, then normalizing it by the IV cross-sectionalarea. Essentially, this value represents the average of all disc heights inthe transverse plane. CT scans of patients were obtained preoperatively(n�20 in A; n�6 in B), and at 6 weeks (n�16 in A; n�2 in B), 3months (n�13 in A; n�3 in B), 6 months (n�8 in A; n�3 in B), 9 months(n�5 in A; n�4 in B), and one year (n�5 in A; n�1 in B) postoperatively.RESULTS: Patients undergoing discectomy only (Group A) lost disc heightfollowing surgery. The average preoperative disc height was 6.16 (SD 1.95)mm, and an initial collapse of approximately 20% occurred within theinitial 6 weeks. By one year, nearly 50% of the preoperative disc heightwas lost. In contrast, patients who had also received the annular closuredevice (Group B) maintained their preoperative disc height throughoutthe follow-up period. Increased disc heights for Group B were even observedat 9 months.CONCLUSIONS: Although our study is at its earliest stages, our resultsshow the following: 1) Patients lose a substantial amount of their preopera-tive disc height following discectomy. 2) There is initial evidence supportingthe concept that an annular closure device can successfully maintain, oreven increase, disc height in discectomy patients, potentially improvingtheir clinical outcomes and disc health.DISCLOSURES: FDA device/drug: Barricaid. Status: Investigational/not approved.CONFLICT OF INTEREST: Authors (EK, OY, AV, JE, GO, GL) Other:Employee of Intrinsic Therapeutics, Inc.; Author (MV) Other: Partial fund-ing received for Group A patient follow-up.

doi: 10.1016/j.spinee.2005.05.358

P144. Healos/rhGDF-5 induces posterolateral lumbar fusionin a New Zealand white rabbit modelDavid P. Magit, MD, MDIV, ME1, Travis Maak, BA2, Bradley Raphael,BA3, Qusai Hammouri3, Gert Polzhofer, MD3, Inneke Drespe, DVM4,Todd J. Albert, MD5, Jonathon N. Grauer, MD1; 1Yale University, NewHaven, CT, USA; 2Yale University; 3CT, USA; 4Yale University, CT,USA; 5Thomas Jefferson University, PA, USA

BACKGROUND CONTEXT: Much work is being done to define poten-tial bone graft alternatives to alleviate the need for autograft with fusionprocedures. Recombinant human growth and differentiation factor-5(rhGDF-5), a bone morphogenic protein, is one such product which isunder consideration. The commercially developed carrier for this productis Healos (cross-linked type I collagen with hydroxyapetite coating). Thiscombined product has been evaluated in some preclinical animal studies andis now being investigated in humans.PURPOSE: The purpose of this study was to evaluate the efficacy ofHealos/rhGDF-5 in inducing fusion in a well established animal model.STUDY DESIGN/SETTING: New Zealand white rabbit posterolaterallumbar fusions carried out to eight weeks.PATIENT SAMPLE: 67 New Zealand white rabbits.OUTCOME MEASURES: Fusion masses were explanted and assessed bymanual palpation, radiography, computed tomography (CT), and histology.METHODS: Single level intertransverse process fusions were performed in67 New Zealand white rabbits. Five fusion constructs were evaluated (n�13for each group): autograft, Healos alone, or one of three does of rhGDF-5 lyophilized to Healos. The doses studied were 0.5mg/cc, 1.0mg/cc, and1.5mg/cc, with one 1.5cc strip used per side for each procedure. At eightweeks, the rabbits were sacrificed. Fusion masses were explanted andassessed by manual palpation, radiography, computed tomography (CT),and histology.RESULTS: Two animals (3%) were lost to anesthesia-related complication.Fusion results by manual palpation were: autograft 38% (5/13), Healos

alone 0% (0/13), and all doses of Healos/rhGDF-5 100% (13/13 for each).Histologic analysis demonstrated abundant bone formation of varying matu-rity with numerous osteoblasts and trabecular architecture in both the low(0.5mg/cc) and middle (1.0mg/cc) doses. Radiographs were 84% sensitiveand 86% specific for detecting fusion based on manual palpation results.Representative CT highlighted bone formation. The high dose (1.5mg/cc)groups were found to have examples with a thin outer shell of mature bonewith numerous osteoblasts that surrounded a marrow-filled matrix filledwith hematopoietic, fat cells and fibrous tissue.CONCLUSIONS: Using a well-established lumbar fusion model, rhGDF-5/Healos induced fusion in 100% of the rabbits studied. This rate wassignificantly greater than the fusion rate produced in the autograft group(38%). Solid bone formation in the two lower doses evaluated suggestedappropriate dosing. The bone shells seen in the highest dose group sug-gested that this dose was too high for the application being evaluated.Overall, the results of this study were encouraging and support furtherongoing studies.DISCLOSURES: No disclosures.CONFLICT OF INTEREST: No conflicts.

doi: 10.1016/j.spinee.2005.05.359

P145. Prospective, single-site evaluation of recreational activitylevels, medication use and return to work in Charite artificialdisc replacement patientsJohn Regan, MD1, Brian Perri, DO2; 1Cedars-Sinai Medical Center,Los Angeles, CA, USA; 2Cedars-Sinai Medical Center, Institute forSpinal Disorders, Los Angeles, CA, USA

BACKGROUND CONTEXT: Recreational activity levels, pain medica-tion use and return to work (RTW) outcomes data has not been reportedin patients following artificial disc replacement (ADR). These variablesare not assessed in typical outcome studies yet are important measures ofsuccessful ADR surgery. Further, no studies have reported ADR outcomesin patients with severely collapsed disc spaces preoperatively.PURPOSE: This prospective study measured activity levels, drug use andRTW data in ADR patients. Are patients able to 1.) return to sports activities;2.) reduce/eliminate medication use for their back pain; and 3.) RTWfollowing ADR? Finally, are there outcome differences in patients withsevere versus minimal disc height collapse preADR?.STUDY DESIGN/SETTING: Sixty consecutive patients were questionedpreADR and at 6 months postADR in routine follow-up. Patient’s recre-ational activities and pain medication use were recorded and scored appro-priately. Outcomes in a subset of patients with either minimal (�20%) orsevere (�80%) disc height collapse were compared.PATIENT SAMPLE: Outcome data were prospectively collected in 60consecutive ADR patients during routine follow-up visits preADR and 6months postADR. There were 12 patients with severe and 36 patients withminimal disc height collapse preADR.OUTCOME MEASURES: Patient’s recreational activities were recordedand scored using an Activity Level Scale before and 6 months after ADR.Similarly, pre- and postADR medication use was recorded and scored usinga Medication Scoring Index. Patients work status was recorded pre- andpostADR. Two subsets of patients with either severe or minimal disc heightcollapse preADR were analyzed for outcome differences.METHODS: Data were collected with respect to patient’s activity levelsand medication use, and then scored according to the pre-defined outcomescales. The results were analyzed and comparisons made between preADRand 6 months postADR time points. Percent RTW and mean time for RTWwas calculated. The outcomes between severe and minimal disc heightcollapse groups were compared.RESULTS: Patients showed a significant improvement in activity levelfollowing ADR from 1.3 preADR to 2.7 postADR. Medication scores alsosignificantly decreased from 3.7 preADR to 2.4 postADR. 68% patientstaking narcotics preADR discontinued by 6 months postADR and requireda mean 3.1 months to stop. A significant number of patients were working

Proceedings of the NASS 20th Annual Meeting / The Spine Journal 5 (2005) 1S–189S180S

CONCLUSIONS: Direct repair of spondylolysis can be recommended foryoung patients which would save a functional segment. The above mean6 year follow-up shows encouraging results.DISCLOSURES: FDA device/drug: Hook screw. Status: Approved forthis indication.CONFLICT OF INTEREST: No conflicts.

doi: 10.1016/j.spinee.2005.05.361

P147. In vitro evaluation of soak time-dependent release ofrhBMP-2 in the immediate postoperative environmentHyun Bae, MD1, Li Zhao, MD2, Pamela Wong, BS3, Ben Pradhan, MD1,Michael Kropf, MD1, Rick Delamarter, MD1, L.E.A. Kanim, MPH, MA1;1Spine Institute at Saint John’s Health Center, Santa Monica, CA, USA;2Saint John’s Health Center, Santa Monica, CA, USA; 3Spine Research

6 months postADR (88%) versus preADR (76%). 12% of patients out ofwork on disability were able to return to work by 6 months postADR.There were no statistical outcome differences in patients with preADR severedisc height collapse verses those with minimal collapse.CONCLUSIONS: Patients were able to significantly increase recreationalactivities and reduce medication use following ADR. RTW rate, even inpatients out on disability may be significantly increased in patients followingADR. Patients with severe disc height collapse may experience similarimprovements in outcomes as those patients with minimal disc heightcollapse.DISCLOSURES: FDA device/drug: Charite Artificial Disc (SBIII). Status:Approved for this indication.CONFLICT OF INTEREST: No conflicts.

doi: 10.1016/j.spinee.2005.05.360

P146. Direct stabilization of lumbar spondylolysis with a hook screwAnand Agarwal, Alan Hammer; Medway Maritime Hospital, Kent,United Kingdom

BACKGROUND CONTEXT: Treatment methods for spondylolisthesisin adolescents and young adults are a matter of controversial discussion.The hook screw method is a direct repair technique that permits restitutioad integrum for a functional segment.PURPOSE: Spondylolysis with instability can produce low back pain.This technique has been successful in young adults and adolescent. Thisstudy shows the postoperative outcome of this patients.STUDY DESIGN/SETTING: A retrospective study involving 32 patientswith spondylolysis who underwent direct repair with a hook screw wasconducted.PATIENT SAMPLE: 34 patients who underwent direct repair for spondy-lolysis.OUTCOME MEASURES: OLDI score preoperative and postoperative.METHODS: A subjective study of direct repair with a hook screw forspondylolysis using the Oswestry Low Back Disability Index (OLDI) andthe Short Form 36 (SF-36) Score. All the patients who underwent a directrepair with a hook screw for spondylolysis between 1996 and 2005 werecontacted and asked to complete an OLDI Score and an SF-36 Score. OLDIand SF-36 scores were obtained preoperatively and postoperatively andthe results compared.RESULTS: A total of 34 patients were included in this study. Responserate was 100%. Mean age of patients was 34 years. Mean preoperative OLDIscore was 18 and postoperatively was 36. The results were subdivided intopoor, no change, good, very good, and excellent results. Good resultsmeant a 5–10 point improvement; very good result meant 10–15 pointimprovement; excellent result meant a greater than 15 point improve-ment. Good to excellent results were reported by 94% of patients. Goodand Very Good results were reported by 23% respectively. Excellent resultwas reported by 76% of patients. One patient had no change and 1 waspoor. Pseudoarthrosis rate was 6%.

Fig. 1.

Foundation, Santa Monica, CA, USA

BACKGROUND CONTEXT: Typically rhBMP-2 is applied to anabsorbable type I collagen sponge (ACS) at least 15 minutes prior toimplantation during a spinal fusion procedure. After careful preparation,rhBMP-2/ACS implant is placed in a surgically prepared bed or a containedsite such a titanium cage or a femoral allograft. Most of the studies onBMP retention and preparation soak time have been performed beforeimplantation. However, the biologic activation of BMP-2 occurs at implan-tation and the immediate postoperative period. During this critical period,the BMP-2/ACS are exposed to different cell types in a fluid sanguine-ous environment.PURPOSE: This in vitro study investigates the influence of preimplantationsoak time on BMP-2/ACS retention in the critical postoperative periodimmediately after implantation.STUDY DESIGN/SETTING: In vitro.PATIENT SAMPLE: NA.OUTCOME MEASURES: NA.METHODS: Sixteen ACS sponges, 1 cm long 0.5 cm wide, 0.5 cm thickwere prepared with 125 ul of 1.5mg/ml rhBMP-2 and allowed to soak for1, 20, 60, or 120 minutes (n�4 sponges / soak time). The prepared spongeswere then placed in normal saline solution at 37 Celsius and continuouslyagitated. Aliquots were withdrawn from each vial at 1, 20 minutes (short-term soak), 1, 12 or 24 hours (long-term soak). The concentration of rhBMP-2released from the sponge into the solution were assessed by ELISA.ANOVA was used with a grouping factor of ‘preparation soak time’ witha repeated measure for ‘sampling release time’ to test for significance.RESULTS: The concentration of rhBMP–2 released from the ACS intothe saline solution was significantly decreased as a function of preparationsoak times of 1, 20, 60 and 120 minutes. (The longer the prep soak time,the less rhBMP-2 in solution.) However, the difference in concentrationwas quite small. The concentration of rhBMP-2 significantly increasedin aliquots sequentially withdrawn at 1 min, 20 min, 1 hr, 12 hrs, and 24hrs from the same vials. (The mean rhBMP-2 concentration in fluid thatwas leached from the ACS was greater over time.) The pattern of release wassimilar for 4 preparation soak times. Overall the total amount of release