Proceedings of the NASS 20th Annual Meeting / The Spine Journal 5 (2005) 1S–189S146S

PURPOSE: To compare the lower thoracic and upper lumbar pediclewidths using MRI, as a measure of the safety and ability to place pedicle screwsat these levels.STUDY DESIGN/SETTING: A retrospective study of 118 non-deformitypatients, comparing the pedicle isthmic width of the lower thoracic spine(T10-12) and the upper lumbar spine (L1-2) using magnetic resonanceimaging.PATIENT SAMPLE: A total of 118 patients (1180 pedicles) were includedin the study. Patients ranged in age from 12 to 94, six were less than 18years of age. There were 58 women and 60 men.OUTCOME MEASURES: All patients were referred for magnetic reso-nance imagines (MRI) study for diagnostic purposes due to either degenera-tive lumbar disease or low back pain. All patients with spinal deformities,pedicle or vertebral fractures, tumors, infections or instrumentation at theselevels, were excluded.METHODS: The MRI was obtained using a 1.5-tesla Magnetom Visionunit (Siemens) under a consistent protocol and included the pedicles fromT10 through L2 on both sides. The pedicle isthmic width was defined andmeasured in the axial plane at the narrowest part of the pedicle, perpendicu-lar to the pedicle axis. Difference among levels was assessed with a one-way analysis of variance with post-hoc least significant difference (LSD)to assess pairwise differences. Student’s t test was used to test for differencebetween genders. Differences in pedicle width due to age and bodysize were assessed using regression analysis.RESULTS: The pedicle size of T12 was larger than the lumbar pediclesin a vast majority, 99% when compared with L1 and 97% when comparedwith L2. In 83% of the patients, T10 was larger than the L1. On average,the smallest mean pedicle isthmic width was noted in L1 (mean�7.0mm) and L2 (mean�7.2 mm) (no statistical difference). The upper lumbarpedicles were smaller than T12 (mean�10.1 mm), T11(mean�9.7 mm)and T10 (mean�8.5) (post-hoc least significant difference pairwise analysis,p values�0.05) (Table 1). No pedicles less than or equal to 5 mm widthwere observed in the lower thoracic area. Overall, 21 of 118 patients (18%)had at least one pedicle �5 mm in the upper lumbar area, most often atthe L1 pedicle. Pedicle widths were larger in males compared with females(p�.05). Body size (height and BMI) did not affect the pedicle size. Leftpedicles were larger than right pedicles in approximately three-quarters ofthe vertebra.

Table 1Mean pedicle diameter by level

95% Confidence 95% ConfidenceMean Std. deviation interval interval

T10 8.5 1.6 5.4 11.5T11 9.7 1.7 6.4 13.1T12 10.1 1.5 7.1 13.1L1 7.0 1.6 3.9 10.1L2 7.2 1.6 4.1 10.2

CONCLUSIONS: In the 99% of non-deformity patients, the isthmic pedi-cle width of T12 was larger than the upper lumbar pedicles. While noneof the lower thoracic isthmic pedicle widths were less than 5 mm, 18% ofpatients had at least one upper lumbar pedicle with width �5 mm. Whenplanning surgery in the thoracic spine for a given patient, in the vastmajority of non-deformity cases, the lower thoracic pedicles will be ableto accept larger screws than will the upper lumbar pedicles.DISCLOSURES: No disclosures.CONFLICT OF INTEREST: No conflicts.

doi: 10.1016/j.spinee.2005.05.290

P76. Neuralgia following posterior lumbar interbody fusionChandra Bhatia, MD, Manoj Krishna, MD, Raymond Pollock, PhD;University Hospital of North Tees, Stockton on Tees, Cleveland, UnitedKingdom

BACKGROUND CONTEXT: Over the last 60 years posterior lumbarinterbody fusion (PLIF) has evolved and available instrumentation andimplants have improved. However a fear of neurological complicationsremains.PURPOSE: To study the incidence, aetiology and management of neuralgiafollowing PLIF surgery. By studying this problem, it may be possible todetermine the causes of neuralgia and therefore prevent the problemoccurring.STUDY DESIGN/SETTING: Prospective case series consisting of pa-tients who underwent PLIF surgery at a spinal unit in a university hospitalin the United Kingdom.PATIENT SAMPLE: Two hundred and twenty five patients who met theinclusion criteria for PLIF surgery. This included chronic back pain withdegenerative disc disease, grade I–III spondylolisthesis, postlaminectomysyndrome and a large central disc prolapse with back and leg pain.OUTCOME MEASURES: Neuralgia was assessed by patient’s subjectivedescription of their leg pain post PLIF.METHODS: Neuralgia was assessed by patient’s subjective descriptionof their leg pain post PLIF. For type I (see results) neuralgia patients wereinvestigated with CT/MRI and possible reexploration of the nerve roots.Type II were treated with Prednisolone and Gabapentin. If symptoms per-sisted, a nerve root block was performed and possibly reexploration.RESULTS: Sixteen (7%) of the 225 patients who underwent PLIF surgerydeveloped neuralgia. The causes were relative swelling/stenosis (9 patients),screw misplacement (2 patients), conjoined nerve root (2 patients), looseposterior arch (2 patients) and graft subsidence (1 patient). Neuralgiaresolved in 11 of the 16 patients. From these results a classification of postPLIF neuralgia is proposed. Type I has its onset �24 hours post surgeryand is due to misplaced screw, loose spinous process, conjoined nerve rootor bony fragments near the nerve root. Type II has onset �24 hourspost surgery and is due to nerve root swelling/relative stenosis or graftsubsidence.CONCLUSIONS: The incidence of post PLIF neuralgia can be minimizedby performing adequate decompression, peforming total facetectomy, bycareful nerve handling and diathermy, avoiding fracture of the spinousprocess and ensuring removal of bony fragments. If neuralgia does occuraggresive management is essential.DISCLOSURES: No disclosures.CONFLICT OF INTEREST: No conflicts.

doi: 10.1016/j.spinee.2005.05.291

P77. Dynamic stabilization with a flexible pedicle screw system: apreliminary outcomes report with 1-year follow-up from twosurgical centersReginald Davis, MD1, James H. Maxwell, MD2; 1Greater BaltimoreMedical Center, Baltimore, MD, USA; 2Scottsdale Spine Care,Scottsdate, AZ, USA

BACKGROUND CONTEXT: Spinal fusion has been the standard treat-ment for radicular pathology secondary to low grade instability and stenoticlesions. In theory, procedures that address the pathology but do not requirefusion of the affected segments may be preferable. The Dynesys SpinalSystem is designed to dynamically stabilize the spine by constrainingmotion, without reliance on a subsequent solid fusion. Although, there havebeen in excess of 14,000 implants performed outside the US, there islittle published information.PURPOSE: To critically measure clinical outcomes following implantationof the Dynesys Spinal System.STUDY DESIGN/SETTING: This is a prospective outcome report fromtwo centers participating in a multicenter US IDE.PATIENT SAMPLE: The 45 patient cohort consisted of 23 males and22 females with a mean age of 54.6 yrs. Patients exhibited radicular pathol-ogy for a mean of 6.4 yrs due to instability or stenosing lesions at 1 or 2contiguous lumbar levels. Seven of the cohort had compensation claimsand 11 reported using tobacco products.

Proceedings of the NASS 20th Annual Meeting / The Spine Journal 5 (2005) 1S–189S 147S

PATIENT SAMPLE: The TLIF surgical procedure was performed on124 patients and the AP surgery was performed on 43 patients. Patientswere treated for painful degenerative disc disease, facet arthropathy, degen-erative instability and spinal stenosis.OUTCOME MEASURES: Clinical parameters such as surgical bloodloss, duration of the procedure, length of hospitalization and complicationswere quantitatively assessed in this study.METHODS: Data were compared for two different TLIF approaches (openversus percutaneous pedicle screw placement) versus AP. Statistical sig-nificance was evaluated using the Chi square method.RESULTS: Compared with the AP surgery group, operative time in theTLIF groups was shorter by 233 min in the open (p�.0001) and by 200min in the percutaneous cases (p�.0001). Blood loss was 126.5 mL lowerin the open (p�.03) and 319 mL lower in the percutaneous TLIF group(p�.0001) as compared with the AP group. Length of stay was shorter by1.95 days in the open (p�.0001) and by 2.9 days in the percutaneous TLIFgroup (p�.0001). Total number of complications was two times lower inthe open or percutaneous TLIF group (62.7% vs. 35.3% and 30.0%) ascompared with the AP group.CONCLUSIONS: Anterior-posterior lumbar interbody fusion is associatedwith approximately two times as many complications, significantly in-creased blood loss, and longer operative and hospitalization times comparedwith both percutaneous and open TLIF for lumbar disc degenerationand instability.DISCLOSURES: FDA device/drug: rhBMP-2 off label use. Status: Notapproved for this indication.CONFLICT OF INTEREST: No conflicts.

doi: 10.1016/j.spinee.2005.05.293

P79. Cervical disc arthroplasty: preliminary results of a randomizedprospective study of single level ACDF vs. Prodisc-C for themanagement of cervical spondylosisMichael Janssen, DO1, Ruth Beckham, NP2, Hugh McPherson, MD2,Douglas Beard, MD2; 1Spine Education and Research Institute, Denver,CO, USA; 2Center for Spinal Disorders, CO, USA

BACKGROUND CONTEXT: Single-level anterior cervical discectomyand fusion (ACDF) has proven to be an excellent treatment for variousdisorders of the cervical spine. However, a concern for adjacent leveldegeneration and loss of cervical motion has prompted the need to considermotion-sparing disc replacement technology in the cervical spine. TheProdisc-Cisa cervical totaldiscreplacement designed to provide thepotential

OUTCOME MEASURES: In addition to demographics and surgical de-tails, patients were assessed for back pain, leg pain, satisfaction and recom-mendation (100 mm VAS), functional status (Oswestry), nuerologicalimporvement, general health (SF-12).METHODS: Patients were placed in a prone position for a posteriorapproach. The pathological segment(s) were exposed via a mid-line or Wiltseapproach. Pedicle screws were placed more anterolaterally than typical anddirected convergently. Care was taken to place the screw properly on thefirst attempt, with the screw head low and at or ventral to the sagittalplane of the facet joints. Stabilizing cords and universal spacers were placedbilaterally and the construct was completed according to manufacturer’srecommendations.RESULTS: 65 segments were instrumented (25 1- and 20 2-level); L4-5accounted for 55.4% of the instrumented levels. Mean blood loss andsurgical time were 421cc and 183min, respectively. Both blood lossand surgical time were less in 1- rather than 2-level cases. Median hospitalstay was 4 days. Mean preoperative leg and back pain was 81.8 and 49.3respectively. Both measures decreased after surgery and were 32.1 and32.7 at 1 year. Oswestry scores decreased from 56.5 preoperatively to 35.4one year postoperatively. General health improved with the PCS increasingfrom 27.3 to 37.1 one year after surgery. The MCS increased from 39.9to 49.9 at the same time. Neurological assesments 1 year post after surgery,revealed maintainance/improvement for motor testing in 92.9%, sensorytesting in 100.0%, SLR in 64.3% and reflex testing for 85.7% of patients.Mean patient satisfaction was 74.8 and likelihood of recommendationwas 79.4at 12 months.CONCLUSIONS: The surgery appeared well tolerated. Postoperative out-come measures were noticeably improved in all areas. This is neitherinconsistent nor noticeably inferior to other treatments. However, avoidingfusion and the ability to maintain a relatively large amount of naturalanatomy may yield greater improvements in outcomes over time. Twosurgical aspects have already become apparent. It is clear in some casesthe Wiltse approach can be successfully used, causing much less tissuetrauma. Also, it appears that there may be cases where stabilization withoutdecompression can alleviate symptoms again minimizing trauma. The lim-ited follow-up length and cohort size suggest careful interpretation ofthese results. Despite the moderate sample size and follow-up lengths, thesepreliminary data are optimistic.DISCLOSURES: FDA device/drug: The Dynesys Spinal System. Status:Investigational/not approved.CONFLICT OF INTEREST: Author (RD) Consultant: Zimmer Spine.

doi: 10.1016/j.spinee.2005.05.292

P78. Transforaminal lumbar interbody fusion vs. anterior/posteriorreconstruction for lumbar disc degeneration and instabilityAlan Villavicencio, MD1, Sigita Burneikiene, MD1, Ketan Bulsara, MD2,Jeffrey Thramann, MD1; 1Boulder Neurosurgical Associates, Boulder,CO, USA; 2University of Missouri, Columbia, MO, USA

BACKGROUND CONTEXT: Multiple various lumbar interbody fusionapproaches are used to treat painful degenerative disc disease and spinalinstability. Both anterior-posterior (AP) reconstructive surgery and transfo-raminal lumbar interbody fusion (TLIF) provide a circumferential fusion.However, the TLIF approach is theoretically less invasive and simultane-ously allows for decompression of neural structures and relief of a radicularpain. There is currently no data in the literature that directly comparesthese two approaches.PURPOSE: The purpose of this study was to compare clinical parameterssuch as surgical blood loss, duration of the procedure, length of hospitaliza-tion and complications for the transforaminal lumbar interbody fusionapproach versus anterior-posterior (AP) reconstructive surgery for lumbardegenerative disc disease and instability.STUDY DESIGN/SETTING: A retrospective analysis was completed on167 consecutive cases performed at Boulder Community hospital (Boulder,Colorado) between January of 2002 and March of 2004.

for motion at the involved cervical functional spinal unit.PURPOSE: The objective of this study is to clinically compare prospective,randomized preliminary results of patients with subaxial cervical radiculo-pathy who treated with either ACDF or cervical disc replacement with theProDisc-C.STUDY DESIGN/SETTING: Under IRB approval, surgeons at a singlecenter performed the surgeries for a total of 46 patients.PATIENT SAMPLE: The ACDF group consisted of 22 patients whounderwent a one level cervical fusion with allograft bone and anteriorplating. The ProDisc-C group consisted of 24 patients who underwent aone level disc replacement. Patient inclusion criteria for the study includeddisc herniation, loss of height, or spondylotic changes between C3-7 levelswith myelopathy and/or radiculopathy. Patients who had undergone previ-ous cervical surgery were not eligible. The average age in the ProDisc-Cgroup was 44 years (range: 33–56) and the ACDF group was 43 years(range 25–60).OUTCOME MEASURES: Efficacy was assessed by evaluating patientsat follow-up by the Neck Disability Index (NDI), SF-12, VAS, and rangeof motion (ROM). Range of motion was measured using standard radio-graphic methods.METHODS: Patients will be assigned a treatment, either Prodisc-C orACDF surgery according to a blocked randomization schedule. During thecourse of the study, patients are assessed preoperatively and postoperativelyat 6 weeks, 3 months, 6 months, 1 year, and 2 years.