P58. Necromechanical comparison of augmentation techniques for insufficiency fracture

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Fig. 2. Range of motion and prevalence of adjacent level degeneration (ALD). was performed plotting the flexion-extension ROM of the most cephalad TDR (x-axis) against the prevalence of radiographic ALD (y-axis) at 9year follow-up. Statistical significance testing was performed using twotailed Fisher exact test. RESULTS: Of 42 patients evaluated, 10 patients (24%) with radiographic ALD were identified. Four patients had loss of disc space height, 3 had anterior osteophyte formation, and 3 had both height loss and osteophytes. None had static or dynamic listhesis ⬎3.5mm. The mean TDR ROM measured was 3.8⬚ (0–18). Mean ROM was 1.5⬚ at L2-3, 3.8⬚ (0–12) at L3–4, 4.4⬚ (0–18) at L4–5, and 3.1⬚ (0–10) at L5-S1. The patients with ALD had a ROM of 1.6⬚ (0–4) whereas the patients without ALD had ROM 4.7⬚ (0–18), (Student t-test, p⫽0.035). A clear relationship between TDR ROM and the development of ALD at 9-year follow-up was observed. When patients were stratified by ROM, none with ROM 䊐5⬚ developed ALD. The overall prevalence of ALD was 24% but was higher in patients with less ROM (FIG. 2). Patients were divided into those with ROM 䊐5⬚ (n⫽13) and those with motion ⬍5⬚ (n⫽29). The prevalence of ALD was 0% in the high ROM group and 34% in the low ROM group (Fisher exact p⫽0.021, odds ratio 13.5). CONCLUSIONS: These data clearly demonstrate that the prevalence of adjacent level degeneration after TDR is higher in patients with ROM ⬍5⬚, and suggest that 5⬚ of flexion-extension ROM may represent a protective threshold against the development of ALD. This information may prove useful in the design and clinical evaluation of nonfusion technologies in spine surgery. Longer-term follow-up of this and other patient cohorts is essential. DISCLOSURES: Device or drug: PRODISC LUMBAR TOTAL DISC REPLACEMENT. Status: Investigational/Not approved. CONFLICT OF INTEREST: No Conflicts. doi: 10.1016/j.spinee.2004.05.177 P108. Can rhBMP-2 (InFUSE) enhance fusion rates in anterior lumbar interbody fusion using standalone femoral ring allografts? Ben Pradhan, Edgar Dawson, Vikas Patel, Rick Delamarter, Michael Kropf, Hyun Bae; The Spine Institute at St. Johns Health Center, Santa Monica, CA, USA BACKGROUND CONTEXT: Anterior lumbar interbody fusion (ALIF) is a well-accepted procedure, and plays an important role in reconstructive spine surgery. Advances in spinal surgical technology has produced a multitude of anterior interbody implants. Still, the femoral ring allograft (FRA) remains a simple and adequate alternative for anterior structural support in spinal surgery. As a stand-alone device however, like most other impacted allografts, the FRA has fallen into disfavor because of reports of high rates of pseudarthrosis. [1,2] PURPOSE: To determine whether the use of rhBMP-2 (InFUSE) applied to an absorbable collagen sponge (ACS) can enhance fusion rates in ALIF with stand-alone FRAs. We also attempt to analyze the factors that may affect fusion in this surgical setting. STUDY DESIGN/SETTING: This is a retrospective study of 36 consecutive patients who underwent ALIF with stand-alone FRAs. A single surgeon

(ED) at the same institution performed all surgeries using identical technique. Minimum follow-up length was 20 months. PATIENT SAMPLE: All patients included in the study had symptomatic degenerative disc disease diagnosed by symptoms of intractable leg and/ or back pain with positive diagnostic imaging findings. The first 27 consecutive patients received FRAs with autologous bone graft packed inside the intramedullary cavities. In an attempt to increase the fusion rate, the next 9 patients received FRAs in which the intramedullary cavities contained InFUSE-soaked ACS. OUTCOME MEASURES: To determine whether BMP enhanced fusion in these patients, pseudarthrosis rates in the BMP and non-BMP groups were compared. METHODS: Nonunion was diagnosed using flexion/extension radiographs, computed tomography scans, and confirmed during revision surgical procedures. RESULTS: Nonunions were identified in 7 of 27 (26%) patients who underwent stand-alone interbody fusion with FRAs and autologous bone graft. In an effort to improve the fusion rate, the surgeon then switched to adding InFUSE-soaked ACS to the FRAs. However, nonunions were identified in 5 of 9 (56%) of these patients who received BMP, a worse fusion rate than the non-BMP group. (The stand-alone FRA technique was no longer used after it became apparent that the use of BMP was not improving fusion rates.) CONCLUSIONS: ACS with rhBMP-2 was not able to increase the fusion rate in ALIF with stand-alone FRAs. In fact there was a trend toward higher pseudarthrosis rates. These results raise interesting points about the way BMP works, and the environment it needs to function properly. The literature has shown that stand-alone FRAs are susceptible to high nonunion rates, which is likely related to motion since supplemental posterior fixation can increase fusion rates. BMP use in fusion cages and threaded allograft dowels has been shown to be succesful in enhancing fusion. [2– 4] However, in this study, even though the compared groups were similar, BMP did not enhance fusion. The compartment created by the FRA and endplates in which the BMP resides was analyzed in an attempt to rationalize the findings. Important variables were considered to be the blood supply, lack of perforations in the graft, the absence of osteoconductive material within the compartment, and motion beyond that which is amenable for fusion. DISCLOSURES: Device or drug: InFUSE. Status: Investigational/Not approved. Device or drug: Femoral ring allograft. Status: Approved for this indication. CONFLICT OF INTEREST: No Conflicts. doi: 10.1016/j.spinee.2004.05.178 P58. Necromechanical comparison of augmentation techniques for insufficiency fracture Heather McCann, MD, Matthew Lepine, John Glaser; Medical University of South Carolina, Charleston, SC, USA BACKGROUND CONTEXT: Current techniques for insufficiency fracture restore pre-fracture strength and all potentially have the complication of cement extrusion. There is minimal information directly comparing techniques. PURPOSE: To compare three techniques of vertebral body insufficiency fracture augmentation by analyzing restoration of height, strength, and stiffness, and quantifying cement leakage. STUDY DESIGN/SETTING: Ex Vivo mechanical study. PATIENT SAMPLE: Four osteoporotic/osteopenic fresh frozen cadaveric spines (T6–L5). OUTCOME MEASURES: ANOVA for Height, Strength, Stiffness, Measurement of Cement Leakage. METHODS: The vertebral bodies were divided into the three treatment groups and by levels (thoracic, thoraco-lumbar, lumbar). All were compressed via MTS by 25% of their initial height to create compression fractures. The bones were fixed using Vertebroplasty, Osteoplasty (Interpore Cross) or Cavity Creation System (Synthes). Pre and post-treatment height,

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

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Table 1 Stiffness (N/m) Group Cavity Creation

Osteoplasty

Vertebroplasty

T TL L T TL L T TL L

Strength (N)

Height (m)

Initial

Treated

Initial

Treated

Initial

Fractured

Treated

1656 2630 3548 1991 2398 1672 2371 1108 2134

3386 1185 1572 1385 1519 1071 3114 2173 1281

5717 4539 5206 5230 5160 4994 4232 5767 5782

9464 7352 7989 8543 6920 5875 9360 8564 7455

2.29 2.49 3.17 2.46 2.83 3.1 2.28 2.61 3.13

1.66 2.14 2.37 1.64 2.05 2.28 1.59 1.99 2.23

1.89 2.2 2.53 1.85 2.25 2.43 1.8 2.13 2.3

strength and stiffness were measured. Cement leakage was deemed significant if more than 1 mL was seen in the spinal canal, endplate or periphery. RESULTS: Strength was not significantly different among the techniques. T6-T9 was significantly stronger post-fixation versus initially (p⬍0.001). There was a significant difference in height measurements between initial, fractured, and post-fixation for all levels, thoracic p⬍.001, thoraco-lumbar p⬍0.004, and lumbar p⬍.001. No significant difference was found between techniques. Stiffness was significantly different in the lumbar levels between initial and post-fixation measurements p⬍0.02. There was no significant difference in stiffness at other levels or between fixation techniques. Cement extrusion was noted at L4 of the vertebroplasty group. A 1 mL leak was noted in the anterior periphery. T11 for vertebroplasty and T7 of osteoplasty peripherally leaked ⬍0.1 mL and 0.8 mL, respectively. CONCLUSIONS: Strength was not significantly different between the three techniques. The thoracic level (T6–T9) was significantly stronger post-fixation versus initially (p⬍0.001). There was a significant difference in height measurements between initial, fractured, and post-fixation for all levels, thoracic p⬍.001, thoraco-lumbar p⬍0.004, and lumbar p⬍.001. No significant difference was found between techniques. Stiffness was significantly different in the lumbar levels between initial and post-fixation measurements p⬍0.02. There was no significant difference in stiffness at other levels or between fixation techniques. Cement extrusion was noted at L4 of the vertebroplasty group. A 1 mL leak was noted in the anterior periphery. T11 for vertebroplasty and T7 of osteoplasty peripherally leaked ⬍0.1 mL and 0.8 mL, respectively. DISCLOSURES: Device or drug: Methylmethacrylate. Status: Not approved for this indication. CONFLICT OF INTEREST: Authors (HM, JG) Grant Research Support: Funding and equipment supplied by Synthes Spine and Interpore Corporation.

STUDY DESIGN/SETTING: A retrospective review of 45 patients who underwent MOTA or VATS for anterior release, discectomy, and fusion prior to posterior instrumented fusion at one acedemic institution. PATIENT SAMPLE: Twenty-one (13 females, 8 males) consecutive patients who underwent MOTA and 24 consecutive patients (17 females, 7 males) who underwent VATS. The indications included rigid and severe scoliosis or thoracic kyphosis. OUTCOME MEASURES: The patients were compared in terms of correction, number of levels operated, blood loss, and operative time. METHODS: All postoperative data was collected and reviewed. A twosample t-test was used in statistical analysis (p⬍0.05). CONCLUSIONS: As hypothesized, no differences were found in terms of correction and blood loss. We found significant differences in the number of levels operated, favoring VATS, and the overall operative time, favoring MOTA. Both approaches resulted in corrections which compare favorably with open thoracotomy. We suggest that one factor in choosing between these two minimally invasive techniques is the number of thoracic levels requiring release. For four levels or less, MOTA offers a faster and simpler operation. For five or more levels, the added complexity of VATS is justified by an incremental decrease in operative time and blood loss with each additional level. DISCLOSURES: No disclosures. CONFLICT OF INTEREST: No Conflicts.

doi: 10.1016/j.spinee.2004.05.179

BACKGROUND CONTEXT: There is a lack of information on national prescription patterns of NSAIDs and muscle relaxants among individuals with back pain in the US. PURPOSE: To examine national prescription patterns of non-steroidal anti-inflammatory drugs (NSAIDs) and muscle relaxants among individuals with back pain in the United States. STUDY DESIGN/SETTING: Secondary analysis of the 2000 Medical Expenditure Panel Survey (MEPS). PATIENT SAMPLE: A nationally representative sample of American adults with back pain in 2000. OUTCOME MEASURES: Prescription of traditional NSAIDs, COX-2 inhibitors or muscle relaxants. It was defined as a dichotomous variable and measured whether or not an individual with back pain had at least one prescription of a drug of interest during the year. METHODS: Individuals with back pain were stratified by socio-demographic characteristics and geographical regions. For each medication category, overall prescribing frequency was compared across different strata and individual drug prescription was analyzed. RESULTS: Traditional NSAIDs, COX-2 inhibitors and muscle relaxants respectively accounted for 16.3%, 10% and 18.5% of total prescriptions for

P13. Mini-Open Thoracoscopically Assisted thoracotomy versus Video Assisted Thoracoscopic Surgery for anterior release in thoracic scoliosis and kyphosis—comparison of operative and radiographic results Rafael Levin1, David Matusz,2*, Amir Hasharoni1, Baron Lonner1, Thomas Errico1; 1New York University, New York, NY, USA; 2Lenox Hill Hospital, New York, NY, USA BACKGROUND CONTEXT: Combining anterior releases, discectomies, and interbody fusion with posterior instrumented fusion is the accepted treatment for severe rigid scoliosis or kyphosis. Video Assisted Thoracoscopic Surgery (VATS) and Mini-Open Thoracoscopically Assisted thoracotomy (MOTA) are two minimally invasive approaches to the thoracic spine. Both reduce surgical trauma, improve cosmesis, and provide effective exposure for release and fusion. PURPOSE: This study compared MOTA and VATS under the hypothesis that both result in similar corrections and comparable operative parameters when used in conjunction with posterior instrumented fusion.

doi: 10.1016/j.spinee.2004.05.180 P103. Prescription of nonsteroidal antiinflammatory drugs and muscle relaxants for back pain in the United States Xuemei Luo1, Ricardo Pietrobon2, Lesley Curtis3, Lloyd Hey, MD1; 1 Duke University Medical Center, Durham, NC, USA; 2Duke University Medical Center, NC, USA; 3Duke University, NC, USA