P6. Quantitative Estimation of Surgical Magnitude in Spinal Surgery: Measurement of Serum Interleukin-6

Proceedings of the NASS 21st Annual Meetings / The Spine Journal 6 (2006) 1S–161S P5. CT Evaluation of Minimally Invasive Transforaminal Lumbar Interbody rhBMP-2 Fusion and Fixation Anthony Salerni, MD; Orthopedic Professional Association, Gilford, NH, USA BACKGROUND CONTEXT: RhBMP-2 has been shown to reliably induce spinal fusion. The best data relate to its use with ALIF. There is less reliable information concerning the use of rhBMP-2 for posterior approaches. PURPOSE: The safety and efficacy of rh-BMP-2 fusions via TLIF have not been satisfactorily elucidated. CT analysis of these fusions can yield highly accurate anatomic data. Correlation of this data with observed complications can also provide needed information. STUDY DESIGN/SETTING: This prospective study is based on the clinical and CT radiographic data. PATIENT SAMPLE: 66 patients underwent MITLIF with rhBMP-2. 50 patients had CTs that were useful for analysis. 66 levels were fused in this group. OUTCOME MEASURES: Fusion is defined as the presence of trabecular bone filling at least the interior of the interbody cage in the absence of indirect parameters that are associated with failed fusion. Extent of intradiscal fusion, F, is defined as the transverse dimension of the fusion mass relative to the transverse span of the disc space as measured on the midcoronal reconstruction of the CT. Exophytic bone, X, is categorized into a hierarchical order of sets according to the extent and location of the new bone growth. The categories were as follows; 0–no exophytic bone, 1–new bone at the annulotomy site and/or along the superior edge of the inferior pedicle, 2–new bone above disc space, 3–new bone filling Kambin’s Triangle, 4–new bone bridging pedicles and/or reconstitution of the lamina. The axial, sagittal, and coronal CT reconstructions of the neuroforamina on the operated and nonoperated sides were used to assess foramenal narrowing. Radicular pain was noted to be either present or absent in each patient at the study’s conclusion. METHODS: Between 5 and 24 months postoperatively 54 patients underwent high-resolution CT of fused levels to assess the nature and extent of the new bone formation. All CT images were digitized. Dimensions were obtained by importing the images into a CAD program and applying the program’s linear measurement tool to each specific image that required relative measurements. Clinical and surgical data were gathered from the records and from patient interviews. CT data are reported for each of the 66 levels fused. RESULTS: Scans of all operated levels fit the criteria for fusion. Measurements of the percentage of the disc space fused showed that 22 levels were between 31–50%, 29 were between 51–70% and 15 were above 71%. 47 levels had either 0 or category X1 exophytic bone. Seven displayed category X2 growth and 12 were in categories X3 and X4. Seven neuroforamen exhibited narrowing. Only 2 patients developed radicular pain that required treatment (Fig. 1).

Fig. 1. A neuroforamen with category X4 exophytic bone growth.

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CONCLUSIONS: The fusion rate was 100%. Most levels displayed superphysiologic amounts of fusion. Formation of substantial amounts of exophytic bone was a frequent occurrence, but development of chronic radiculopathy was uncommon. This risk is offset by those associated with the traditional procurement of iliac crest autograft. Consequently, the use of rhBMP-2 for minimally invasive TLIF can be cautiously recommended as long as patients are closely monitored and the surgeon has a mechanism in place to report adverse events. FDA DEVICE/DRUG STATUS: rhBMP-2 (Infuse): Not approved for this indication. CONFLICT OF INTEREST: Author (AS) Royalties: Medtronic Sofamor Danek. doi: 10.1016/j.spinee.2006.06.264

P6. Quantitative Estimation of Surgical Magnitude in Spinal Surgery: Measurement of Serum Interleukin-6 Satoru Demura, MD, Norio Kawahara, MD, Hideki Murakami, MD, PhD, Katsuro Tomita, MD; Kanazawa University, Kanazawa, Ishikawa, Japan BACKGROUND CONTEXT: An extent of surgical stress was sometimes estimated based on an incisional length, operative time, and blood loss amount. However, these factors are not always consistent with the extent of surgical stress which the surgeons felt by their experience. Interleukin-6 (IL-6) is a cytokine which is one of the key mediators in systemic inflammatory response. Hence, a serum IL-6 level was used to try to estimate a quantitative marker of surgical stress in major cardiac and thoracoabdominal surgery. PURPOSE: Our purpose here is to evaluate whether the serum IL-6 level is a quantitative marker of the surgical magnitude in spinal surgeries. STUDY DESIGN/SETTING: Prospective clinical study. PATIENT SAMPLE: There were 60 patients who had electively undergone the spinal surgeries. These patients were divided into 6 groups according to the surgical procedures: Total en bloc spondylectomy (TES; single-level, 10 patients), posterior lumbar interbody fusion (PLIF; single-level, 10 patients), posterolateral fusion (PLF; single-level, 10 patients), lumbar laminotomy (LL; single-level, 10 patients), lumbar open discectomy (LD; single-level, 10 patients), and cervical laminoplasty (CL; 4 levels, 10 patients). OUTCOME MEASURES: Serum IL-6, C-reactive protein (CRP), creatine kinase (CK), blood loss amount, and operation time were measured. METHODS: Blood samples were taken from venous blood in the following periods: before the surgery, at the end of the surgery, and 6 hours after the surgery, and the first, third, and seventh day after the surgery. The serum IL-6 level was measured by chemiluminescent enzyme immunoassay. RESULTS: The serum IL-6 level peaked on the first day. CRP peaked 3 days after surgery and was preceded by a peak in IL-6 concentration. The peak IL-6 level significantly correlated with CRP (r50.71, p!.01), CK (r50.59, p!.01), operation time (r50.67, p!.01), and blood loss amount (r50.79, p!.01). The IL-6 level on the first day was 184.8625.4 pg/ml (TES), 79.9625.7 pg/ml (PLIF), 80.7615.3 pg/ml (PLF), 30.364.7 pg/ml (LL), 31.864.7 pg/ml (CL), and 18.763.5 (LD) (Fig. 1). CONCLUSIONS: CRP reflects the extent of systemic response. From our results, IL-6 is an earlier marker of systemic response than CRP in the spinal surgery. CK reflects the extent of local soft-tissue damage. Our results indicate that IL-6 also reflects the severity of local tissue damage in the spinal surgery. The IL-6 level on the first day might be a quantitative marker of surgical magnitude (Fig. 1). From this point of view, TES was the largest surgical magnitude from our experience and IL-6 level. Although the surgical magnitude of PLIF seemed to be larger than that of PLF from the view of blood loss amount and operation time, both were the same surgical magnitude from the IL-6 level. Our results suggest that the IL-6 level reflects the reaction of both systemic and local response which were of surgical magnitude in the spinal surgery.

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Proceedings of the NASS 21st Annual Meetings / The Spine Journal 6 (2006) 1S–161S

Fig. 1. Changes of serum IL-6 levels in spinal surgery.

FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. CONFLICT OF INTEREST: No conflicts. doi: 10.1016/j.spinee.2006.06.265

were given to the patients followed by their RSA examination. Standing biplanar films were collected and the ROM (sagittal and coronal bending) of the adjacent vertebrae was determined by RSA. RESULTS: Based on the clinical surveys, this group of patients had similar outcomes compared with larger clinical populations with ProDisc replacement. The flexion/extension ROM with the disc replacement averaged 2.5 degrees at 1.5 months and increased to 8.8 degrees over the follow-up time points. The lateral bending ROM with the disc replacement remained consistent over the five time points and averaged 3.0 degrees. The flexion/extension ROM after lumbar interbody fusion did not change over time and averaged approximately 2 degrees. The motion at the L4/5 level after disc replacement was consistently greater across all time points than the motion at the L5/S1 level for both sagittal (5.9 vs. 2.1 degrees) and coronal (4.2 vs. 0.6 degrees) bending. In many cases no motion within the accuracy of 0.5 degree could be detected at L5/S1. CONCLUSIONS: The amount of flexion/extension segmental ROM measured in this study for those with disc replacement was similar to other studies using planar radiography and less than the typical 10-20 degrees reported for normal ROM. However, the flexion/extension ROM is significantly more and increasing over time in those with disc replacement compared with those with lumbar fusion. In lateral bending, the amount of motion with disc replacement was less than the typical 6-16 degrees reported for normal ROM. It is yet unclear how much motion is necessary to prevent adjacent segment disease. FDA DEVICE/DRUG STATUS: ProDisc: Investigational/not approved. CONFLICT OF INTEREST: Author (AF) Grant/Research Support: Synthes Spine. doi: 10.1016/j.spinee.2006.06.266

P7. Eighteen-Month Follow-Up of Lumbar Spine Range of Motion Following Intervertebral Disc Replacement Using Radiostereometric Analysis Amir Fayyazi1, Nathaniel Ordway1, Bruce Fredrickson2, Kenneth Yonemura3, Hansen Yuan4; 1State University of New York Health Science Center at Syracuse, Syracuse, NY, USA; 2Syracuse, NY, USA; 3 Institute for Spine Care, Syracuse, NY, USA; 4SUNY - Upstate Medical University, Syracuse, NY, USA BACKGROUND CONTEXT: Lumbar spinal fusion has been shown to result in degeneration of adjacent levels. An intervertebral disc replacement may reduce or delay the incidence of adjacent level degeneration by allowing motion at the surgical level. However, many clinical studies that have examined intervertebral disc replacements have focused on clinical pain scores and less on kinematics after implantation. Although flexion and extension of the motion segment can be measured on lateral X-rays, measuring lateral bending and rotation of the device is extremely difficult on plain radiography. Radiostereometric analysis (RSA) is a method to accurately monitor lumbar motion in three dimensions and has been used to examine kinematics after lumbar fusion, but has not been used after disc replacement. PURPOSE: To accurately measure the postoperative range of motion of the spinal segment after placement of ProDisc interbody device using RSA. STUDY DESIGN/SETTING: This study was performed as a part of the prospective randomized clinical study evaluating the efficacy of ProDisc lumbar total disc replacement. PATIENT SAMPLE: Twelve patients (15 discs) with a ProDisc intervertebral disc replacement were followed postoperatively at 1.5, 3, 6, 12, and 18 months. For comparison purposes, five patients with an anterior lumbar interbody fusion were followed postoperatively at 3 and 12 months. OUTCOME MEASURES: VAS and Oswestry outcome measures were examined as part of the clinical evaluation. Sagittal and coronal range of motion measures were analyzed from the RSA evaluations. METHODS: The intervertebral disc implant surgery was performed and implants sized in standard fashion. Five tantalum beads were inserted into the vertebrae adjacent to the surgical level during surgery for follow-up RSA analysis. At the postoperative time points, ODI and VAS surveys

P8. Relationship Between Total Disc Replacemet Device Position, Range of Motion, and Clinical Outcome Paul Jeffords, MD, Jack Zigler, MD, Donna Ohnmeiss, PhD, Barton Sachs, MD, Ralph Rashbaum, MD; Texas Back Institute Research Foundation, Plano, TX, USA BACKGROUND CONTEXT: The biomechanics of total disc replacement (TDR) are still being investigated and there has been little information available related to the clinical function of these devices. PURPOSE: The purpose of this study was to determine if the placement of the ProDisc implant significantly affected either the range of motion achieved with the device or clinical outcome. STUDY DESIGN/SETTING: Data were extracted from that collected at one center participating in the prospective FDA-regulated trial evaluating ProDisc. PATIENT SAMPLE: The study was based on 29 patients undergoing TDR at a single level as part of an FDA-regulated trial. OUTCOME MEASURES: Outcome measures used in the study were visual analog scales (VAS) assessing pain, Oswestry Disability Index, and patient satisfaction scores (based on a 0–10 VAS). METHODS: Device placement in the sagittal plane was determined by measuring the distance of the device end plates from the anterior and posterior margins of the vertebral body on the neutral lateral radiograph. Patients were divided into two groups based on device placement. In one group, the device was placed posterior to midline or within 2 mm anterior of the midline. The other group of patients was comprised of those in whom the device was implanted more than 2 mm anterior to midline. All radiographs were measured by a single evaluator. Radiographic evaluation and clinical outcome were based on the 6-month follow-up. RESULTS: Device placement in the sagittal plane was significantly related to ROM. In the group with posterior to midline placement of the device (n57), the mean ROM was 7.4 compared with only 2.8 (p!.05) in the group with anterior placement (n522). Among the levels with posterior to midline device placement (n57), the mean ROM