Quantifying Radiation Exposure During Minimally Invasive Extreme Lateral Interbody Fusion

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Proceedings of the NASS 27th Annual Meeting / The Spine Journal 12 (2012) 99S–165S

to detect cells expressing red fluorescent protein (RFP), and the beta-galactosidase (b-gal) assay to detect cells expressing b-gal. METHODS: Allogeneic articular chondrocytes, obtained from young New Zealand White (NZW) rabbits, were transduced with recombinant adenovirus expressing RFP and b-gal and then labeled with infrared dye. Surgeries were performed on young adult NZW rabbits. Three IVDs per rabbit were injured with 18 gauge needles. Four weeks later, transduced/labeled chondrocytes were injected into the IVDs. At 2 or 8 weeks post injection, the rabbits were sacrificed. The spines and IVDs were imaged with an infrared scanner to detect infrared-dye labeled cells and then sectioned and processed for the b-gal assay and fluorescence microscopy. RESULTS: Infrared-dye labeled cells were detected in the spine and individual discs. The infrared fluorescence intensity did not significantly decrease from 2 to 8 weeks after injection. The two transgenes, b-gal and RFP, were also detected in the injected IVDs at both time points. CONCLUSIONS: These studies have demonstrated that infrared-dye labeled cells survived in the rabbit IVDs for up to 8 weeks without any decrease in infrared fluorescence intensity. Transplanted cell presence and viability were further confirmed by detecting RFP and b-gal activity in the discs. This study suggests that allogeneic chondrocytes would be a valuable source for cell therapy for disc diseases. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. http://dx.doi.org/10.1016/j.spinee.2012.08.378

P105. Effectiveness of Physical Therapy as an Adjunct to Epidural Steroid Injections in the Treatment of Lumbar Spinal Stenosis: A Pilot Randomized Controlled Trial Venu Akuthota, MD1, Amy S. Hammerich, DPT2, Paul E. Mintken, DPT3, Joshua A. Cleland4, Julie M. Whitman5, Jaspal R. Singh, MD6, Elizabeth Knight, MD7, Kelly J. Santo, BS, MS8; 1Golden, CO, US; 2Regis University, Denver, CO, US; 3Lakewood, CO, US; 4Franklin Pierce University, Concord, NH, US; 5Evidence In Motion, Roseville, CA, US; 6 Denver, CO, US; 7Evergreen, CO, US; 8University of Colorado School of Medicine Department of Physical Medicine and Rehabilitation, Aurora, CO, US BACKGROUND CONTEXT: Lumbar spinal stenosis (LSS) is a prevalent and disabling condition in the aging population that often results in substantial physical and psychosocial burden and is associated with significant health care costs. Nonsurgical options have been used to control pain and provide self-management of lumbar stenosis flares. Epidural steroid injections and physical therapy are commonly used non-operative treatment options in patients with symptomatic lumbar spinal stenosis. However, the comparison between epidural steroid injections alone and in combination with physical therapy has not been fully evaluated. PURPOSE: This study was a preliminary investigation of the effectiveness of epidural steroid injections, with and without physical therapy, in the treatment of symptomatic lumbar spinal stenosis. STUDY DESIGN/SETTING: Pilot multicenter, randomized controlled, single-blind clinical trial. The study was conducted in spine specialty and physical therapy clinics. PATIENT SAMPLE: Twenty-seven participants (59% men; mean age 69.8 years) with clinical symptoms of leg pain due to radiculopathy or neurogenic claudication and correlating advanced imaging findings of lumbar spinal stenosis were enrolled into the study. Subjects were randomly assigned to receive either injection only (IO) or injection and physical therapy (IPT). OUTCOME MEASURES: Outcomes were assessed at baseline, 10 weeks, and 6 months. The results from a numeric rating scale (NRS), the Oswestry Disability Index (ODI), and the short form (SF-36) were compared between groups.

METHODS: All participants received at least 1 transforaminal epidural steroid injection. In addition, participants in the IPT group were enrolled in a therapy program. Using principles outlined in the Whitman et al. study, manual therapies targeted the lumbo-pelvic spine, hips, thoracic spine and abdominal/core stabilization muscles as well as aerobic conditioning. Patients attended 1-2 physical therapy sessions/week for 8-10 weeks. RESULTS: Data was collected at baseline and all follow up intervals on fourteen patients (7 in IO and 7 in IPT) with mean duration of symptoms of 20.6 months and 18.8 months, respectively (p50.35). Significant reduction in pain scores (NRS) occurred at 6 months in the IO group, (6.7 and 3.0 [p !0.05], at baseline and 6 months, respectively). The IPT group did not show significant difference, (7 and 5.6 [p50.34], at baseline and 6 months, respectively). ODI at baseline and 6 months in the IO group was 16.8 and 9.9 (p50.08), and in the IPT group was 18 and 17.6 (p 50.73), respectively. There were no differences between groups at any follow-up interval although there was a trend towards more improvement in the physical component score (PCS) of the SF-36 in the IPT group. CONCLUSIONS: Preliminary results from this sample suggest no additional benefit for physical therapy in conjunction with epidural steroid injection when evaluating pain reduction and improvement in disability in symptomatic lumbar spinal stenosis patients. However, the positive trend in the physical component scores in the IPT group suggests that physical therapy may be beneficial in terms of quality of life and general sense of well-being. These data are part of an ongoing clinical trial evaluating the use of epidural steroid injection and physical therapy. Further research is needed to evaluate whether these findings are consistent when applied to a larger sample. The limitations of this study were a high loss to follow-up, relatively short-term follow-up period, and a small sample size. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. http://dx.doi.org/10.1016/j.spinee.2012.08.379

P106. Quantifying Radiation Exposure During Minimally Invasive Extreme Lateral Interbody Fusion Jacob H. Bagley, BS1, Scott T. Brigeman, BA1, Andrew Marky, MD1, Jian Xi, MD, Christopher R. Brown, MD2, Robert E. Isaacs, MD1; 1Duke University Medical Center, Durham, NC, US; 2Durham, NC, US BACKGROUND CONTEXT: Minimally invasive Extreme Lateral Interbody Fusion (XLIF) is an increasingly popular procedure for the treatment of isthmic and degenerative thoracolumbar spondylolisthesis. During this procedure, intraoperative fluoroscopy is used to visualize the vertebral anatomy and ensure the proper placement of the radiopaque construct. Patients and surgeons may be exposed to significant levels of radiation during their surgery. In sufficient doses, such ionizing radiation can cause skin burns, nausea, and cataracts as well as increase the lifetime risk of cancer. While several studies have demonstrated that the XLIF procedure is welltolerated and produces a high rate of arthrodesis, the procedure requires more intraoperative fluoroscopy than open approaches. However, no study has yet quantified the amount of radiation to which the patient is exposed during XLIF. PURPOSE: We sought to quantify the radiation dose to the patient during the XLIF procedure. STUDY DESIGN/SETTING: A prospective cohort analysis. PATIENT SAMPLE: Eighty consecutive patients, who underwent XLIF between April, 2010 and January, 2012. OUTCOME MEASURES: Total absorbed radiation per patient, absorbed radiation per level fused, total fluoroscopy time per patient, and fluoroscopy time per level. METHODS: Radiation dosage data was prospectively collected from 80 consecutive patients who underwent XLIF. All surgeries were performed by two fellowship-trained spine surgeons, each with over 5 years of

All referenced figures and tables will be available at the Annual Meeting and will be included with the post-meeting online content.

Proceedings of the NASS 27th Annual Meeting / The Spine Journal 12 (2012) 99S–165S experience with the procedure. An OEC 9900 Elite C-arm that measured total absorbed dose and exposure time was used to provide fluoroscopic imaging in both the AP and lateral planes. When necessary, surgeons used magnification to improve image quality. In smaller patients, pulsed imaging could be used to reduce radiation exposure at the expense of image resolution. Cases involving heavy use (O30% total fluoroscopy time) of magnification (‘‘Mag group’’) and those utilizing pulsed imaging (‘‘Pulse group’’) were compared using one-way ANOVA to those cases performed under normal imaging (‘‘NoMag group’’). RESULTS: A total of 228 vertebral levels were treated with minimally invasive XLIF, ranging from T9-T10 to L4-L5. Mean fluoroscopy time was 2.96 minutes (1.04 min/level) and mean absorbed dose was 107.9 mGy (37.9 mGy/level). The Mag group (N544), NoMag group (N528), and Pulse group (N58) were statistically similar in age (62.3 Mag, 67.5 NoMag, 65.8 Pulse, p50.16), male-to-female ratio (0.36, 0.39, 0.25, p50.76), BMI (30.2, 28.7, 24.9, p50.08), and levels treated (2.7, 2.9, 3.5, p50.56). Differences between the total fluoroscopy time per level (1.64 min/level Mag, 0.75 min/level NoMag, 0.34 min/level Pulse, p! 0.001) and absorbed dose per level (64.5 mGy/level, 20.7 mGy/level, 12.2 mGy/level, p!0.001) were statistically significant. CONCLUSIONS: Patients undergoing the XLIF procedure absorb a moderate amount of ionizing radiation during fluoroscopy. The amount of radiation exposure in our sample was more than the typical amount reported for open thoracolumbar fusions, but is well within the reported range of radiation exposure for minimally invasive spine procedures. Pulsed imaging, which can only be used in patients with a thin body habitus, was associated with an almost 50% reduction in radiation exposure per level compared to normal fluoroscopy. The use of magnification during intraoperative fluoroscopy was associated with a 300% increase in the amount of radiation used per level over normal fluoroscopy. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. http://dx.doi.org/10.1016/j.spinee.2012.08.380

P107. Retention and Early Osteogenic Induction of Bone MarrowDerived Mesenchymal Cells by Commercially Available Carrier Substrates Christopher D. Chaput, MD1, Matthew B. Murphy, PhD2; 1Scott & White Hospital, Temple, TX, US; 2Celling Biosciences, Austin, TX, US BACKGROUND CONTEXT: Carriers or substrates used in fusions, nonunion defects, and as bone void fillers are often selected based on handling properties rather than their effects on co-implanted or endogenous stem cells and osteoblasts. PURPOSE: To examine the immediate retention of co-implanted cells by the carriers and assess their osteoinductive potential after 48 hours. The general state of the material and pH also was studied. STUDY DESIGN/SETTING: In vitro assay of cell retention and osteoinduction. PATIENT SAMPLE: Pre-expanded human mesenchymal stem cell (hMSC) preparations established from bone marrow aspirate samples were used in this in vitro study. OUTCOME MEASURES: Cell retention was measured on 9 different carrier substrates (decellularized bone chips, demineralized bone matrix (DBM) putty, DBM/poloxamer, pure Tricalcium Phosphate (TCP), TCP/ collagen, HA/collagen, TCP/collagen/bioglass, CymbiCyte (60/40 HA/ TCP), and GenOsteo Engineered Scaffold (HA with interconnected pores and high surface area)) at 30/60 minutes and 48 hours. Osteogenic inductive potential was examined by gene expression of Runx2, alkaline phosphatase (ALP), and collagen type I (Col1) at 48 hours. METHODS: Of the selected substrates, 0.5 mL were incubated in hMSCrich fluid at 37 C for 30 and 60 minutes (benchtop) and 48 hours (5% CO2). After culture, substrates were washed with saline to remove

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loosely-adherent cells. Cell counts were determined by analysis of GAPDH mRNA expression against known standards by real time reverse transcriptase-polymerase chain reaction (RT-PCR). Osteoinduction was determined by Runx2, ALP, and Col1 mRNA expression by RT-PCR at the 48 hour time point. The pH of the solution was measured at early time points as some substrates became soluble. RESULTS: At 30 minutes, inorganic substrates (CymbiCyte, GenOsteo, and pure TCP) exhibited significantly more cell retention than bone chips and other commercially available materials. By 60 minutes, bone chips, CymbiCyte, and GenOsteo demonstrated significantly higher cell counts than all other materials. After two hours of culture, collagen-containing materials became soluble and lost their structure. Dissolution of those carriers made evaluation beyond early time points impossible. The DBM putty had an acidic effect on the solution while the bioglass caused an increase in pH during the first hour. After 48 hours, bone chips and GenOsteo exhibited significantly higher cell counts than all materials examined and were statistically equivalent, while CymbiCyte achieved approximately half of those values. On a per cell basis, bone chips, CymbiCyte, and GenOsteo increased Runx2 production 8.5, 10.5, and 8.7-fold, respectively, over tissue plastic monolayer culture controls. ALP expression was only moderately increased by culture on the substrates (2.3, 1.7, and 1.8fold, respectively). Col1 expression was highest on bone chips (4.6-fold increase over plastic), although the protein was upregulated by CymbiCyte (3.8-fold) and GenOsteo (1.5-fold). CONCLUSIONS: Bone chips and insoluble calcium phosphate-based substrates provide sufficient structural integrity for cell retention, growth, and differentiation. High cell counts on GenOsteo at each time point are likely related to the greatly increased surface area per volume of the material. Bone chips, CymbiCyte, and GenOsteo all demonstrated an osteoinductive effect on hMSC’s without the addition of other chemical or mechanical stimuli to enhance differentiation. FDA DEVICE/DRUG STATUS: Genosteo (Not approved for this indication), Cymbicyte (Approved for this indication), Demineralized bone matrix (Approved for this indication), DBM/poloxamer (Approved for this indication), Pure tricalcium phosphate (Approved for this indication), TCP/collagen (Approved for this indication), HA/collagen (Approved for this indication), TCP/collagen/bioglass (Approved for this indication). http://dx.doi.org/10.1016/j.spinee.2012.08.381

P108. Clinical Review of Lumbar Spine Fusion for Chronic Low Back Pain Due to Degenerative Disc Disease Frank M. Phillips, MD1, Paul J. Slosar, MD2, Jim A. Youssef, MD3, Gunnar B. Andersson, MD, PhD4, Frank J. Papatheofanis, MD, MPH, PhD5; 1 Midwest Orthopaedics at Rush, Chicago, IL, US; 2Spine Care Institute of San Francisco, San Francisco, CA, US; 3Durango Orthopedic Associates, Durango, CO, US; 4Rush University Medical Center, Chicago, IL, US; 5 University of California San Diego, San Diego, CA, US BACKGROUND CONTEXT: Despite a large number of publications on the outcomes of spinal fusion surgery for chronic low back pain there is little consensus on efficacy. PURPOSE: This clinical review aimed to compile and categorize the published evidence for lumbar fusion surgery for discogenic chronic low back pain in a systematic way to provide an updated and comprehensive summary of the clinical outcomes. STUDY DESIGN/SETTING: Systematic literature review. PATIENT SAMPLE: Fusion cohorts from the studies reviewed included a total of 3,974 patients. OUTCOME MEASURES: Studies were included in the review if they reported two or more validated patient-reported clinical outcomes measures: VAS, ODI, SF-36 PCS, and patient satisfaction. METHODS: A MEDLINE search was performed to identify published articles reporting clinical outcomes measures with minimum 12 months follow-up following lumbar fusion surgery in adult patients with low back

All referenced figures and tables will be available at the Annual Meeting and will be included with the post-meeting online content.