Proceedings of the NASS 19th Annual Meeting / The Spine Journal 4 (2004) 3S–119S 101S

cervical discectomy and fusion; increasing numbers of surgeons are aban-doning its use in favor of nonautologous materials. Bone graft donor sitepain and morbidity, as well as increased operative time are factors citedby surgeons for this trend. The most commonly used substitute for AICBGis human cadaveric allogeneic bone. Freeze-dried allografts may be storedat room temperature and have an indefinite shelf life; however, the processof freeze-drying can reduce mechanical strength by 50% compared withfrozen grafts. Frozen allografts maintain their mechanical strength and canbe stored for up to 1 year.PURPOSE: The purpose of this study was to evaluate the fusion rate insingle and multilevel ACDF using a machined, frozen, corticocancellousallograft.STUDY DESIGN/SETTING: This multicenter study retrospectively re-viewed a cohort of patients who underwent ACDF using a machined,frozen, corticocancellous allograft comprised of two cortical planks of bonesurrounding a cancellous center. The data is compared to historical cohorts.PATIENT SAMPLE: 93 patients with 148 fusion levels were includedand followed for two years. All patients underwent either a single-level ormulti-level ACDF using the Smith-Robinson technique. An anterior cervicalplate was used in all cases.OUTCOME MEASURES: Fusion was identified by the absence of aradiolucent gap between the graft and the endplate and the presence ofcontinuous, bridging, bony trabeculae at the graft-endplate junction. Fusionwas assumed if at least two of three evaluators identified a given levelas such.METHODS: Follow-up radiographs were obtained at six weeks and threemonths postoperatively. Additional interval studies were obtained as clini-cally or radiographically indicated for up to two years or until fusion wasobserved. Lateral cervical spine radiographs were presented in a randomfashion with regard to patient identity and examination date and assessedby three independent evaluators, blinded with regard to surgery date, out-come and all other clinical and demographic data.RESULTS: 47 of 51 patients (92%) who underwent single-level ACDFachieved fusion during the observation period. In patients who underwentmulti-level ACDF 92 of 97 levels (95%) were observed to fuse during theobservation period. 38 of the 42 patients (91%) who underwent multi-levelACDF achieved a solid fusion at all operated levels. The overall combinedfusion rate was 94%.CONCLUSIONS: The reported fusion rate for unplated single-level ACDFusing AICBG is 83% to 100% depending on the series cited. Fusion ratesfor multi-level ACDF are generally lower. Published studies report a fusionrate for unplated two-level ACDF using AICBG of 50% to 75%. Our resultscompare favorably with published results for single-level ACDF. For multi-level ACDF our fusion rate was substantially higher than that of mostpublished series. This machined, frozen, corticocancellous allograft demon-strates fusion rates similar to or better than those reported for autologousiliac crest and freeze-dried iliac crest or fibular allografts.DISCLOSURES: Device or drug: VG2 Cervical Allograft. Status: Ap-proved for this indication.CONFLICT OF INTEREST: No Conflicts.

doi: 10.1016/j.spinee.2004.05.205

P44. The association between psychiatric comorbidity and opioidanalgesia in patients with discogenic low back painAjay D. Wasan, MD, MA, Gudarz Davar, Robert Jamison, PhD;Brigham and Women’s Hospital, Boston, MA, USA

BACKGROUND CONTEXT: Psychiatric comorbidity affects approxi-mately 50% of all patients with chronic low back pain and diminishesthe effectiveness of many treatments. The primary psychopathologies aredepression, anxiety for pain, and neuroticism (a tendency to respond withsadness, worry, and other negative emotions). These frequently co-occur,such as in pain patients with a mixture of anxiety and depression symptoms.

P49. Mechanisms of persistent neck pain following nerve rootcompression injury understanding behavioral hypersensitivity in thecontext of spinal cytokine responses and tissue biomechanicsRaymond Hubbard, BS, Sarah Rothman, BSE, Beth Winkelstein, PhD;University of Pennsylvania, Philadelphia, PA, USA

BACKGROUND CONTEXT: Spinal nerve roots have been identified assources of low back pain. While risk of such injury exists in the cervical spinedue to neck motions, no study has examined the cervical nerve root’sresponse to mechanical injury. Nerve root compression or transection in-duces behavioral hypersensitivity and a host of spinal immune changesin pain models, including glial activation and upregulation of inflammatory

cytokines, such as TNF and IL6. Cytokine responses have been shown toboth depend on root compression magnitude and directly modulate pain.PURPOSE: The purpose of this study is to examine the cervical nerveroot’s potential for pain due to injury and to understand pain responses inthe context of spinal nociception (cytokine) and injury biomechanics.STUDY DESIGN/SETTING: N/APATIENT SAMPLE: N/AOUTCOME MEASURES: N/AMETHODS: The right C7 nerve roots of male Holtzman rats (275–375g) were injured by: transection (n�4), compression (via 10 or 60gf mi-croclips) (n�17), or sham (n�10) surgeries, according to IACUC-approvedprocedures. After injury, bilateral forepaw hypersensitivity was assessed for7 days quantifying mechanical allodynia (MA) and thermal hyperalgesia(TH). In a subset of rats (n�14), spinal IL6 was assayed by ELISA 1 dayafter injury. Biomechanical estimates of compression injury were made usingimage analysis; applied stress and strain and tissue recovery were measuredfor both clips (n�16).RESULTS: Bilateral MA was elevated over sham for all 7 days in bothcompression injuries (p�0.042) and did not depend on clip force. MAresolved by day 5 after transection. While ipsilateral MA peaked at day 1after compression, contralateral MA did not peak until day 7. In contrast,TH responses were only slightly different from sham and these changeswere apparent only in the forepaw ipsilateral to injury. On day 1 aftertransection, spinal C7 IL6 increased 5–fold over normal levels and was2 times that of shams. Likewise, root compression (60gf) increased spinalIL6 by 2.5 times over normal; yet, this was not different from sham. Fornerve root compression, imposed injury stresses (16.5�1.1, 100.6�6.6g/mm2) and tissue recovery (66.9�19.6, 39.3�17.4%) were significantlydifferent (p�0.006) for 10 and 60gf, while strains differed by only 6%(81.7�4.7, 87.7�3.6%).CONCLUSIONS: These behavioral data confirm the cervical nerve root’ssusceptibility for injury and pain. Varied MA responses for these injur-ies suggest separate nociceptive mechanisms for each injury mechanism.Differential sensitivity to thermal and mechanical stimuli in the rootcompression model mimic clinical observations and suggest differentialdamage to Ad and C fibers of the root. Further, spinal IL6 correlates withMA with rapid elevation following transection. IL6 levels are also elevatedafter compression but not to the same degree as transection, suggestingeither a less severe spinal inflammatory response for compression, or thatIL6 levels may continue to rise at later time points in compression injury.Continued efforts will further examine this and other cytokine responses forpainful cervical injuries. Biomechanical analyses of the clip injuries suggestthat nerve root strain, not stress, may dominate pain given the similarityin applied strains for these clip compressions and resulting MA. Behavioral,cytokine, and biomechanical findings here indicate the nerve root’s poten-tial for generating neck pain. In addition, a complex interplay between injuryparameters, nociceptive mechanisms, and modulatory factors of nociceptionand pain has been identified.DISCLOSURES: No disclosures.CONFLICT OF INTEREST: Author (BW) Grant Research Support:NIAMS (#AR047564-02) Whitaker Foundation (#RG-02-0311).

doi: 10.1016/j.spinee.2004.05.206