P111. Disc height restoration and its effect on range of motion and clinical outcome after semi-constrained lumbar total disc replacement (ProDisc-II)

164S

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

c-Jun, GFAP, TNFRI, TNFRII, XIAP, and NOS subtype (nNOS, eNOS, iNOS) were performed on the spinal cord sections. RESULTS: Open field motor testing using the BBB Locomotor Rating Scale showed that young rats substantially improved hind limb function compared with adult rats. At 7 days, statistically significant differences were noted between the two groups (p⬍.01). Continuous upregulation of c-Jun expression and downregulation of GFAP were noted in adult rats. Conversely, upregulation of GFAP expression and downregulation of c-Jun expression were noted in young rats Upregulation of TNFRII expression occurred later than TNFRI in the spinal cords of both young and adult rats following SCI. RT-PCR demonstrated that TNFRI and II expression was greater in young rats than adult rats and the expression of TNFR approximately equaled that of XIAP. Increased neuroprotective eNOS reactivity was prominent in young rats, whereas increased neurodestructive iNOS expression was prominent in adult rats. CONCLUSIONS: Our results demonstrate that young and adult rats exhibit significant differences in cytokine expression following SCI. In young rats, upregulation of GFAP, TNFRI, TNFRII, eNOS and downregulation of cJun may play significant neuroprotective roles following SCI. These results are a necessary preliminary step in devising potential therapeutic treatments of spinal cord injury. Future work will focus on the development of agonists and antagonists to prevent or control apoptosis. DISCLOSURES: No disclosures. CONFLICT OF INTEREST: No conflicts. doi: 10.1016/j.spinee.2005.05.324

P110. Improved sacral fixation using a new fenestrated pedicle screw with PMMA Darrel S. Brodke, MD1, Jonathan Pond, MD1*, Kent N. Bachus, PhD1, James Chappius, MD2; 1University of Utah, Salt Lake City, UT, USA; 2 Atlanta Orthopedic Group, Atlanta, GA, USA BACKGROUND CONTEXT: Rigid posterior sacral fixation is often required when extending a posterior lumbar fusion to the sacrum. In the normal spine the L5/S1 junction allows for 20 degrees of flexion/extension, contributing 25% of all lumbar spine motion. In addition, sacral fixation is ofen the last instrumented level in a long fusion construct. These factors lead to large demands on sacral fixation to resist loosening and/or pullout. Rigid fixation in osteoporotic spines is problematic due to poor bone quality leading to loose sacral pedicle screws. Augmentation of sacral pedicle screws with PMMA in osteoporotic lumbar spines has been shown to increase pull-out strength of sacral pedicle screws. We postulate that a fenestrated pedicle screw augmented with PMMA will improve sacral fixation. PURPOSE: The objective of this study is to compare the fixation of a bicortical sacral pedicle screw to the following two fixation constructs in osteoporotic human sacra: 1) unicortical fenestrated sacral pedicle screw augmented with PMMA, 2) unicortical solid pedicle screw augmented with PMMA. STUDY DESIGN/SETTING: Biomechanical cadaveric study. PATIENT SAMPLE: DEXA confirmed osteoporotic human cadaveric sacra. OUTCOME MEASURES: Cantilever pull-out strength of various sacral fixation methods in osteoporotic spines. METHODS: Osteoporotic sacra were divided from attached spine and potted in two-part filler compound. A 6.5 mm bicortical pedicle screw was placed into one pedicle of each sacra. The contralateral side was randomly assigned to receive a unicortical fenestrated 6.5 mm pedicle screw augmented with PMMA, or a unicortical solid 6.5 mm pedicle screw augmented with PMMA. All screws had the same dimensions and unicortical screws were placed such that the tip was within 2 mm of the anterior cortex. Pull-out testing was performed as follows: The potted sacrum was affixed to the base of a testing machine. A rigid rod was attached perpendicular to the pedicle screw. To mimic in vivo failure, a fulcrum was positioned 2cm cranial to the S1 screw along the rod. Cantilever pull-out was accomplished

by applying an anterior force 2 cm cranial to the fulcrum until there was a disruption in the force displacment curve. Pull out force was recorded. The PMMA augmented screws (fenestrated and solid) were normalized to the specimen by recording pullout as a percentage of the contralateral bicortical control. 95% confidence intervals were calculated. RESULTS: Fenestrated pedicle screws augmented with PMMA outperformed both bicortical pedicle screws and solid pedicle screws augmented with PMMA (Table 1). Table 1 Comparison of performance of the three types of pedicle screws Fixation method

Mean pull-out force (N)⫾95% CI

Bicortical Solid with PMMA Fenestrated with PMMA

1047⫾293 1035⫾118 1342⫾302

Pull-out normalized to specimen control (Bicortical)⫾95% CI Bicortical Solid with PMMA Fenestrated with PMMA

100⫾0% 81⫾14% 136⫾12%

CONCLUSIONS: In osteoporotic sacra, pull out strengths of fenestrated pedicle screws augmented with PMMA were superior to bicortical pedicle screws. Pull-out strength of solid pedicle screws augmented with PMMA were not statistically different than bicortical pedicle screws. In osteoporotic sacra, fenestrated pedicle screws augmented with PMMA may decrease screw/bone fixation failure. DISCLOSURES: FDA device/drug: pedicle screw. Status: Approved for this indication. CONFLICT OF INTEREST: Authors (DSB, JP) Grant Research Support: Grant# dsb040601. doi: 10.1016/j.spinee.2005.05.325 P111. Disc height restoration and its effect on range of motion and clinical outcome after semi-constrained lumbar total disc replacement (ProDisc-II) Ben B. Pradhan, MD, MSE*, Hyun W. Bae, MD, Michael A. Kropf, MD, Linda E.A. Kanim, MS, Rick B. Delamarter, MD; Saint John’s Health Center, Santa Monica, CA, USA BACKGROUND CONTEXT: With the notion that motion preservation may reduce adjacent segment degeneration, the first US clinical trials of lumbar total disc replacements (TDR) have been completed with encouraging results. Modularity of the device allows disc height restoration and indirect foraminal decompression. Collapsed discs are distracted with appropriate releases of contracted tissues. Surgeons generally attempt to restore the disc height to what is considered normal (ie, unaffected adjacent segments). However, no reports exist about how disc height restoration affects motion and clinical outcome after TDR. PURPOSE: To examine the effect of disc height restoration on range of motion at the operated spinal segment, and on clinical outcomes after TDR with a semi-constrained prosthetic disc (ProDisc-II). STUDY DESIGN/SETTING: A cohort analysis from a prospective, randomized, and controlled study of TDR versus fusion for lumbar degenerative disc disease. PATIENT SAMPLE: Patients who underwent single-level disc replacement for degenerative disc disease with a semi-constrained prosthetic disc. OUTCOME MEASURES: Visual Analog Scale (VAS), Oswestry Disability Index (ODI), and sequential radiographs (including bending films). METHODS: 96 patients with single-level TDR as part of a prospective, randomized, controlled study were included. Preoperative and postoperative disc heights and range of motion were measured from radiographs at 6 weeks, 3, 6, 12, 18, and 24 months. The Visual Analog Scale and Oswestry Disability Index were used to measure outcome. Results were categorized according to gain in disc height to analyze for any correlation.

Proceedings of the NASS 20th Annual Meeting / The Spine Journal 5 (2005) 1S–189S RESULTS: Results reveal that TDR is able to restore and preserve motion at all time points (approximately 9 degrees at ⬎12 months). The results also reveal that more motion is gained when the postoperative disc is within 0.8–2 times the preoperative disc height, versus 2–4 times (9–10 versus 5–6 deg, p⬍.05). Comparing to the unaffected adjacent disc, again more motion was seen when the postoperative disc height was within 0.8–2 times the “normal” disc. Specifically, discs likely to be distracted most (relative to preoperative) were those most collapsed–these showed the least postoperative motion, were difficult to distract intraoperatively, and were more likely to be at L5-S1. VAS and ODI significantly decreased in all TDR patients, although less improvement occurred with the most distracted discs (p⬎0.05). CONCLUSIONS: Disc mobility and clinical outcome may be optimized by achieving disc heights close to those of the unaffected adjacent discs. However, less postoperative motion can be expected after TDR at a highly collapsed disc. This tends to be more common at L5-S1, where there may be less motion to begin with. Moreover, the tensioning of tissues around a highly collapsed disc after TDR may contribute to reduce range of motion as well. DISCLOSURES: FDA device/drug: ProDisc-II prosthetic disc. Status: Investigational/not approved. CONFLICT OF INTEREST: No conflicts. doi: 10.1016/j.spinee.2005.05.326

P112. Early experience with a minimally invasive vertebral reconstruction technique utilizing contained bone graft Karl Schultz, Jr., MD, Todd Stewart, MD, Gilbert Chandler, MD, Nabil Muhanna, MD; Specialty Clinics of Georgia, Gainesville, GA, USA BACKGROUND CONTEXT: The growng successful use of vertebroplasty and kyphoplasty with methylmethacrylate (MM) to treat painful osteoporotic, traumatic, and neoplastic compression fractures is well documented. However, embolism, risk of extravasation, and adjacent segment fractures remain realistic concerns with MM. A contained biologic alternative to MM would have the theoretical advantages of being non-toxic, osteoconductive, and more closely approximate the modulus of elasticity of native bone, possibly reducing the incidence of subsequent adjacent segment fractures. PURPOSE: To evaluate the feasibility and efficacy of a novel minimally invasive biological vertebral reconstruction technique in the treatment of traumatic, osteoporotic, and neoplastic spinal compression fractures. Specific attention is paid to clinical outcome and complications (including incidence of adjacent segment fractures). STUDY DESIGN/SETTING: Prospective clinical feasibility and efficacy evaluation in a multispecialty clinic treating traumatic, osteoporotic and neoplastic vertebral body fractures. PATIENT SAMPLE: 50 vertebral levels treated in our first 40 patients. Age range⫽37–96 follow-up⫽3–12 months Traumatic compression fractures: n⫽6 Osteoportic compression fractures: n⫽41 Neoplastic compression fractures: n⫽3. OUTCOME MEASURES: Visual Analog Pain Score (pre and post procedure); Immediate CT scan after procedure CT scan and Xrays at 6 months post procedure. METHODS: Prospective evaluation of patient’s VA pain score, Xrays, and CT scan by independent observer. Preop X-rays, Postop X-rays, Postop CT scan, and 6 month postop CT scan and X-rays evaluated and scored on percentage of collapse. Preop bone density scores recorded when appropriate. Pain score and stability of vertebral reconstruction (ie, collapse, migration, infection, etc) each recorded at follow-up time points. RESULTS: A significant improvement in pain scores (VAS) was seen in all but two patients at their latest follow-up. All but two fractures (4%) were stabilized by the procedure at latest follow-up. There was one case (2%) of adjacent segment fracture during the follow-up period. While there was no evidence of implant containment failure, there were two cases

165S

of encroachment of the implant into the spinal canal, both related to operator error. There were two infections in two separate patients, 1) a superficial tract infection, and 2) a postoperative osteomyelitis. CONCLUSIONS: In our early experience, the expandable allograft implant appears to be an effective and safe treatment alternative to MM for the management of spinal compression fractures. With the rates of adjacent segment fractures only 2% in our early study, the improved modulus of elasticity of this technique may reduce adjacent segement fractures, a complication currently being seen more frequently with the use of non biologics such as methylmethacrylate. DISCLOSURES: FDA device/drug: Optimesh. Status: Approved for this indication. CONFLICT OF INTEREST: Author (KS) Consultant: Spineology. doi: 10.1016/j.spinee.2005.05.327

P113. Outcome evaluation of operative and nonoperative management of lumbar disc protrusion causing radiculopathy Kenneth Thomas, MD1, Charles Fisher, MD2*, Paul Bishop, MD3, Michael Boyd, MD2, Peter Wing, MB2, Marcel Dvorak, MD2; 1 University of Calgary, Calgary, Alberta, Canada; 2University of British Columbia, Vancouver, British Columbia, Canada; 3Vancouver Gen. Hospital, Vancouver, British Columbia, Canada BACKGROUND CONTEXT: Several authors have documented the favorable natural history of lumbar disc protrusion causing radiculopathy and its predictable response to nonoperative care. On the other hand, clinical improvement may be greatly accelerated by lumbar microdiscectomy and it is for this reason that lumbar discectomy is among the most common surgical procedures performed in North America. Studies using standardized outcome measures that compare nonoperative with operative care are rare and clear treatment guidelines have not yet been identified. PURPOSE: To assess health related quality of life (HRQOL) following either lumbar discectomy or nonoperative care for lumbar disc protrusion causing radiculopathy (LDPR). STUDY DESIGN/SETTING: Prospective cohort study from a tertiary care referral center. PATIENT SAMPLE: Six-hundred and twenty-three patients, assessed for LDPR, were enrolled in a prospective cohort study. Four hundred ninety seven patients, 333 in the lumbar discectomy group and 164 in the nonoperative group, had sufficient follow-up and were analyzed. OUTCOME MEASURES: Primary–NASS Lumbar Spine Instrument NSS Score Secondary–NASS Lumbar Spine Instrument PDS Score Short Form 36 (SF-36). METHODS: Patients completed baseline as well as six and twelve month generic (SF-36) and disease-specific (NASS Lumbar Spine Instrument) HRQOL measures. Demographic comparisons between groups, using standard descriptive statistics, were made. Multivariable analysis was used to adjust for known confounders to obtain an unbiased regression coefficient for the primary outcome–the neurogenic symptoms score (NSS) from the NASS instrument. Outcome measures were compared between groups and to published normative data. RESULTS: The NSS showed significant improvement in both the lumbar discectomy and nonoperative care groups at the primary study end-point. The difference in the magnitude of improvement, between groups, was not statistically or clinically significant. The study was adequately powered. Of the secondary outcome measures only the NASS pain and disability score (PDS), mental health (MH) domain of the SF-36 and the mental component summary (MCS) of the SF-36 showed a significant difference between groups favoring surgery, the clinical significance of which is questionable.. CONCLUSIONS: Health related quality of life after LDPR, as measured in this study by NASS NSS was not meaningfully associated with the treatment received, within the time frame of this study. At follow-up all outcome measures remained lower than population normative scores, suggesting that irrespective of treatment an element of disability remained. DISCLOSURES: No disclosures.