Proceedings of the NASS 19th Annual Meeting / The Spine Journal 4 (2004) 3S–119S 93S

in the usual care treatments over the 24-week study. In addition, no untowardeffects of AE training were reported in the study.CONCLUSIONS: A low to moderate intensity home based AE programwas found to a safe intervention associated with improvements in cardiovas-cular fitness measures and low back flexibility and function, but had noeffect on medications, epidural injections or physical therapy referrals inpatients with symptomatic lumbar HNP in treatment.DISCLOSURES: No disclosures.CONFLICT OF INTEREST: No Conflicts.

doi: 10.1016/j.spinee.2004.05.187

dimensions prior to fracture, but to a much lesser degree than radiographicassessments of the pediatric pedicle have suggested.PURPOSE: To demonstrate viscoelastic accommodation and expansion ofthe pedicles of pediatric spine during placement of thoracic pedicle screws.STUDY DESIGN/SETTING: A biomechanical study performed in a labo-ratory setting.PATIENT SAMPLE: An intact, fresh-frozen cadaveric spine of a scoliotic9-year-old male.OUTCOME MEASURES: Pedicle failure was based upon visualinspection.METHODS: Pedicles were studied between T2 and T12 bilaterally. AfterCT and radiographic imaging of the spine, the spine was disarticulated ateach level and all soft tissues were carefully removed. The height, width,and circumference of each pedicle were recorded at each reference point.Measurements were performed at the following stages: prior to pediclemanipulation, after placement of a 2-mm thoracic pedicle finder, afterremoval of the pedicle finder, and after placement and removal of sequentialpedicle screws (beginning at 4.75 mm, enlarging in 0.75 mm incrementsto a maximum of 8.5 mm). The moment of failure of the pedicle andperiosteum were recorded.RESULTS: The average dimensions of the thoracic pedicles were: 8.47mm height, 5.92 mm width, and 30.1 mm circumference prior to manipula-tion. The average initial dimensions of the lumbar pedicles were: 10.37mm height and 6.58 mm width. The pediatric thoracic pedicle diameterexpanded to accept a screw with an average diameter 111% of the originalexternal transverse diameter (range: 73% to 143%). When compared to theinternal diameter of each pedicle (based upon CT scan measurements atthe isthmus of the pedicle), the pedicle expanded an average of 198%(range: 141% to 265%) without failing. The overall circumference of thethoracic pedicle increased an average of 6.3% to accommodate the screw.The earliest pedicle failure was at the left pedicle of T4 with a 5.5 mmscrew. 83% of the pedicles accepted a 6.25 mm screw, 63% accepted a7.0 mm screw, 30% accepted a 7.75 mm screw, and 17% accepted an 8.5mm pedicle screw before failure. There were no failures of the medialpedicle wall.CONCLUSIONS: The relatively mild change in the overall circumferencein the face of a dramatic change in the transverse diameter can be explainedby viscoelastic accommodation and expansion. During accommodation, thecross section of the pedicle undergoes plastic deformation and changesfrom a vertically-oriented oblong shape to a more rounded shape prior toexpansion. Our data confirm the viscoelastic properties of the pediatricpedicle are very significant, allowing almost a 200% increase in internaldiameter prior to failure. A single pedicle was unable to accept a 5.5 mmscrew prior to failure suggesting significantly smaller screw sizes may notbe necessary in the pediatric population.DISCLOSURES: Device or drug: Pedicle Screw. Status: Approved forthis indication.CONFLICT OF INTEREST: Authors (PC, ASR, AG, MS, RH, AP)Other: Screws, instruments, and specimen were provided by DePuy Spine,Inc.; Author (SAR) Other: The specimen, insrtuments, and screws were pro-vided by DePuy Spine, Inc.; Author (HS) Other: Employed by DePuySpine, Inc.

P88. Posterior decompression and fusion for symptomatic metastatictumors of the thoracic and lumbar spinePaul Arnold, MD, Joshua Klemp, BS,BS, Joan Mcmahon, MSA, BSN,CRRN; University of Kansas Medical Center, Kansas City, KS, USA

BACKGROUND CONTEXT: Controversy exists regarding the optimalmanagement of symptomatic metastatic spine disease. Laminectomy aloneyielded poor results, andhasgiven way to anteriordecompression, fusion,andfixation in a single setting; posterior decompression with instrumentation;or a combined approach. For many patients, an anterior operation is optimal:the bulk of the tumor is ventral, and decompression and anterior columnsupport can be achieved with one approach. However, in some patients aposterior approach is preferable, due to multiple lesions, inability to toleratean anterior procedure, predominantly posterior lesion, or kyphosis.PURPOSE: We present our experience of 73 patients who underwentposterior decompression, fixation, and fusion.STUDY DESIGN/SETTING: Retrospective case review.PATIENT SAMPLE: Patients with symptomatic metastatic spine disease.OUTCOME MEASURES: Pain reduction, neurologic improvement, com-plication rateMETHODS: 73 patients with symptomatic metastatic disease underwenta posterior operation with dorsal and ventral decompression, posteriorinstrumentation, and fusion. Five patients also had an anterior operation.Age range was 23–83 years. Indications for surgery included intractableback pain; spinal cord compression with or without neurologic deficit; needfor tissue diagnosis; worsening neurologic status while undergoing radiationtherapy. All patients had plain x-rays, CT scan, and MRI performed pre-operatively. Lung cancer was the most common primary tumor, followedby breast cancer and renal cell carcinoma.RESULTS: 74% of patients had improvement in pain scores one monthafter surgery. 54% of patient improved neurologically. Three patients (4%)had neurologic worsening. There were two cases of hardware failure (onesix years after surgery) and five wound infections.CONCLUSIONS: Posterior decompression, fixation, and fusion is a safe,efficacious method of treating selected patients with metastatic spine dis-ease. This approach may be particularly useful in patients who cannottolerate an anterior procedure, who have kyphosis, who harbor multiplespinal or extra-spinal or extra-spinal lesions, or whose tumor is predomi-nantly dorsally located.DISCLOSURES: No disclosures.CONFLICT OF INTEREST: No Conflicts.

doi: 10.1016/j.spinee.2004.05.188

P8. Thoracic pedicle expansion after pedicle screw insertion in apediatric cadaveric spine: a biomechanical analysisPatrick Cahill1, Anthony S. Rinella, MD1*, Alexander Ghanayem, MD2,Salvador A. Rinella, MD3, Mark Sartori, BS4, Robert Havey4, HassanSerhan, PhD5, Avinash Patwardhan, PhD2; 1Loyola University MedicalCenter, Maywood, IL, USA; 2Loyola University of Chicago, Maywood,IL, USA; 3Silver Cross Hospital, Joliet, IL, USA; 4Hines VA Hospital,Hines, IL, USA; 5DePuy AcroMed, Raynham, MA, USA

BACKGROUND CONTEXT: Prior studies suggested significant pedicleexpansion in immature spines during pedicle screw insertion, but no bio-mechanical studies have confirmed the viscoelasticity of the pediatric pedi-cle. Studies of adult cadavers demonstrate a mild increase in pedicle

doi: 10.1016/j.spinee.2004.05.189

P33. The impact of residual low back pain on quality of life aftersurgical treatments for lumbar disc herniationEtsuro Yorimitsu1, Kazuhiro Chiba1, Morio Matsumoto2, YoshiakiToyama2; 1Keio University, Tokyo, Japan; 2Keio University, Shinjuku,Tokyo, Japan

BACKGROUND CONTEXT: Residual low back pain (LBP) is one ofthe most frequent complications after standard discectomy (SD) for lumbardisc herniation (LDH). Our previous study, using LBP score of JapaneseOrthopaedic Association (JOA) scoring system, revealed that residual LBPafter SD was significantly stronger than that after anterior spinal fusion(ASF). However, there have been few studies that focused on residual LBP