P15. Unilateral Pedicle Screw Instrumentation in Minimally Invasive Lumbar Fusion

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Proceedings of the NASS 23rd Annual Meeting / The Spine Journal 8 (2008) 1S–191S

STUDY DESIGN/ SETTING: Prospective, nonrandomized consecutive series of patients undergoing surgery by a single surgeon. PATIENT SAMPLE: Forty-two consecutive patients with painful DLS age 68 years(47-85 years) underwent posterior instrumented reduction/fusion and ALIF in 21 patients at average 4.2 levels (3-6 levels) or TLIF in 21 at average 2.7 levels (1-4 levels). The decision of ALIF vs. TLIF was surgeon preference. ALIF group curves were larger (34 vs 27 ) with less lordosis (25 vs 45 ) pre-op. Follow-up averaged 38 months (24-68 months). OUTCOME MEASURES: Oswestry Disability Index (ODI), visual analog pain scores (VAS), and pain medication use were followed. Radiograph measurements included the main scoliosis curvature, T12-S1 lordosis, coronal and sagittal spinal balance, and pelvic incidence. Fusion was defined as bridging bone on imaging without implant loosening and !3mm motion on flexion-extension. METHODS: Indications for surgery included painful stenosis, rotational listhesis, or spinal imbalance failing O6 months conservative care. Cages and BMP-2 were used in TLIF, and structural allograft or cages and BMP-2 in ALIF. Posterior arthrodesis was achieved with local autograft and allograft. The deformity in both groups was corrected by a combination of direct translation, derotation, and compression/distraction on 5.5mm titanium rods. Posterior constructs averaged 6.8 levels(4-9 levels) for both groups. Clinical and radiographic data was collected pre-op and post-op 6 weeks, 1 year, 2 years, and latest follow-up. RESULTS: The ALIF group had 3 nonunions, 3 adjacent level fractures, 3 revisions for adjacent level degeneration, 3 infections, and one footdrop. Revision surgery was performed in 8/21. Medical complications in this group included 1 each pulmonary embolus, ileus requiring temporary colostomy, and stroke. The TLIF group had 1 each infection, nonunion, adjacent segment degeneration, transient footdrop, and additional surgery to adjust coronal balance, with 3/21 requiring revision surgery. VAS for both groups were similar: TLIF 6.7 pre-op(3-10) improved to 2.9(1-8), and ALIF 6.5pre-op(0-10) improved to 2.9(1-7). Pain medication usage declined post-op for both groups. Oswestry outcomes were also similar: TLIF 46.9(18-66) pre-op improved to 25.5(18-36), and ALIF 52.0(28-82) improved to 31.0(0-64). Curve correction was similar: ALIF group curves of 34 (13-49 ) pre-op correcting 70% to 10 (0-18 ). TLIF group curves of 27 (14-64 ) pre-op corrected 70% to 8 (0-22 ). Lordosis improvement was similar for both groups. CONCLUSIONS: With current deformity correction techniques, both ALIF and TLIF are effective adjuncts in DLS surgery, with similar deformity correction and fusion rates. However, the complications with posterior-only surgery for DLS appear to be significantly fewer. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.

ambiguous with surgeon preference and experience playing a significant role in choice of procedures. PURPOSE: To define the levels of complications and resource utilization related to multilevel cervical spine fusion surgery, and to evaluate the impact of surgical approach on these outcomes. STUDY DESIGN/ SETTING: A retrospective nationwide database study of inpatient perioperative complications. PATIENT SAMPLE: All patients undergoing multilevel (four to eight levels) cervical spine fusion for degenerative disease between 2003 and 2005 at institutions represented in the Nationwide Inpatient Sample database. OUTCOME MEASURES: Measures of patient periprocedural mortality, selected specific morbidities, and resource utilization were evaluated. Resource utilization included length of hospitalization, inflation-adjusted cost, and likelihood of non-routine discharge to assisted living. METHODS: Data for 8548 patients who underwent cervical fusion of four to eight levels was collected from the Nationwide Inpatient Sample database (2003-2005), and subjects were grouped by surgical approach (anterior versus posterior). Descriptive statistics were used to compare baseline characteristics, and bivariate analysis and logistic regression modeling were used to evaluate the effect of surgical approach on mortality, selected postoperative complications, length of stay, hospitalization cost, and discharge disposition. RESULTS: This observational study indicates that a posterior approach to multilevel cervical fusion is associated with more respiratory complications, postoperative infections, symptomatic hematomas, and transfusions when compared to an anterior approach. Resource utilization was nearly double for those undergoing a posterior approach, including hospital length of stay, inflation-adjusted cost, and likelihood of discharge to an assistedliving facility. Not surprisingly, this study confirms that patients fused posteriorly had a lower incidence of symptomatic postoperative dysphagia. CONCLUSIONS: This nationwide study defines the incidence of mortality and the frequency of inpatient complications encountered during multilevel cervical fusion. The results suggest that immediate morbidity from anterior approaches is less than those undergoing posterior fusion. Prospective analysis is required to evaluate if these findings remain significant in a randomized study population. Further, these results represent only perioperative complications. However, based on the data presented herein, when confronted with the patient requiring a four-level cervical fusion, the anterior approach may offer an less risky and less costly option. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. doi:10.1016/j.spinee.2008.06.256

doi:10.1016/j.spinee.2008.06.255

P14. Which is the Best Fusion Approach? A Nationwide Perspective to the Surgical Treatment of Diffuse Cervical Spondylosis Mohammed Shamji, MD, MSc1, Chad Cook, PT, PhD, MBA2, Ricardo Pietrobon, MD, PhD, MBA2, Sean Tackett, BS2, Christopher Brown, MD2, Robert Isaacs, MD2; 1Duke University, Durham, NC, USA; 2Duke University Medical Center, Durham, NC, USA BACKGROUND CONTEXT: Cervical spine fusion is performed for various indications in patient populations ranging from young and healthy to aged and frail. The choice of surgical approach is affected by disease pathoanatomy, but also by age, medical comorbidities, and the number of involved levels. Anterior fusion is more common for single-level pathology in relatively young, healthy patients; and posterior fusion is typically performed on older, more comorbid patients with multilevel disease. Consequently, retrospective comparisons of surgical approaches for cervical fusion will be impacted by this bias, and the optimal management of multilevel cervical spine pathology remains

P15. Unilateral Pedicle Screw Instrumentation in Minimally Invasive Lumbar Fusion Graham Hall, BS1, Jean-Pierre Mobasser, MD2; 1Indiana University, Indianapolis, IN, USA; 2Indianapolis Neurosurgical Group, Indianapolis, IN, USA BACKGROUND CONTEXT: Bilateral pedicle screw instrumentation has become a widely accepted technique for stabilization during single level lumbar fusion. There is very little scientific data assessing whether unilateral instrumentation could provide adequate stability for the interbody fusion process to occur. PURPOSE: The purpose of this study is to assess whether unilateral screw placement has an equivalent efficacy to bilateral screw placement in allowing bone fusion to occur. If unilateral screw placement is proven to be equivalent, then using this approach will: reduce patient morbidity, reduce blood loss, decrease operative times, reduce cost, and result in less postoperative pain. STUDY DESIGN/ SETTING: This is a retrospective review looking at follow up computed tomography scans 6–12 months after a minimally

Proceedings of the NASS 23rd Annual Meeting / The Spine Journal 8 (2008) 1S–191S invasive transforminal lumbar interbody fusion with unilateral percutaneous pedicle screw instrumentation. Off-label use of rhBMP-2 was performed in the interbody space in all cases. PATIENT SAMPLE: 21 patients with unilateral instrumentation have had follow up computed tomography scans in the 6–12 month post-operative period to assess fusion. OUTCOME MEASURES: This is a purely radiographic analysis to assess interbody fusion with unilateral instrumentation. Independent neuroradiologists reviewed all computed tomography scans and analyzed the interbody fusion. METHODS: All post-operative ct scans were performed at the same hospital and 1mm slices with reformatted images were utilized to assess fusion. RESULTS: All 21 patients showed radiographic evidence of fusion between 6–12 months post-operatively. There were no non-unions observed in this group of patients. CONCLUSIONS: Unilateral pedicle screw instrumentation provides adequate stability for the interbody fusion to occur. FDA DEVICE/DRUG STATUS: Pedicle screw device: Approved for this indication; rhBMP-2: Not approved for this indication.

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RESULTS: Average follow-up was 25 months. Average preoperative Cobb’s angle, pelvic obliquity and apical rotation were 118.2 , 16.7 and 57 respectively. Average postoperative Cobb’s angle, pelvic obliquity and apical rotation were 48.8 , 8 and 43 respectively showing 59.4%, 46.1% and 24.5% correction, which were significant statistically. Average number of osteotomy level was 4.2 and average blood loss was 33566884 milliliters. Mean operation time was 330646 minutes and none of the patient required postoperative ventilator support. None of the patient displayed any signs of neurological or vascular injuries during or after the operation. CONCLUSIONS: We recommend multiple posterior vertebral osteotomies for severe and rigid scoliosis because of following advantages: 1) it provides release of anterior column under direct vision of cord; 2) it facilitates creep relaxation to the anterior as well as posterior structures and 3) prevents need of anterior procedure, and reduces massive bleeding and chances of neurological damage. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. doi:10.1016/j.spinee.2008.06.258

doi:10.1016/j.spinee.2008.06.257

P16. Multi-level Posterior Vertebral Osteotomy for Correction of Severe and Rigid Neuromuscular Scoliosis: A Preliminary Study Hitesh Modi, MS, Seung-Woo Suh, MD, PhD, Yang Jae-Hyuk, MD; Scoliosis Research Institute, Korea University Guro Hospital, Seoul, South Korea BACKGROUND CONTEXT: For correction of severe and rigid scoliotic curve, anterior-posterior combined or posterior vertebral column resection procedures are used. Anterior release is a burden for patient with already compromised pulmonary functions and posterior column resection carries a high risk of neurologic damage as well as massive intraoperative bleeding. Therefore, authors developed a new technique, which avoids the both. PURPOSE: It is a prospective study of 13 neuromuscular scoliosis patients with severe and rigid curves to determine the effectiveness and amount of correction with this technique without anterior release. STUDY DESIGN/ SETTING: Thirteen neuromuscular scoliosis patients (7 CP, 2 DMD and 4 SMA) who had rigid curve more than 100 degrees were selected for the study prospectively. All patients were operated with posterior-only approach using pedicle screw construct. PATIENT SAMPLE: There were seven males and six females with an average age of 21 years (range, 13–32 years). There were nine thoraco-lumbar curves, three lumbar curves and one thoracic curve. Average preoperative Cobb’s angle in coronal plane was 118.2 (range, 100 150 ) with flexibility of 20.3% (average 24.1 , range 10 -36 ) on bending radiograms. OUTCOME MEASURES: The correction in Cobb’s angle, pelvic obliquity and apical axial derotation were compared with paired t-test. For further evaluation, we divided our patients in two groups: spastic and paralytic groups and we evaluated our results between these two groups using unpaired t-test. P value of less than 0.05 was considered significant for all the statistical calculations. METHODS: To achieve desired correction, multilevel vertebral osteotomies were executed at three to five levels (apex and one or two level above and below the apex) through laminectomy sites connecting from concave to convex side. Once osteotomies were finished, repeated corrective manipulation was applied over temporary short segment fixation, above and below the apex, on convex side. On concave side, the rod was fixed with screws with manipulation followed by derotation maneuver. Finally, short segment fixation removed and rod-screw construct fixed on convex side, which was followed by posterior fusion. Intraoperative MEP monitoring was applied for all patients.

P17. Acute Fracture of the End or Adjacent Level after Posterior Lumbar Spine Fusion and Instrumentation Edward Abraham, MD, Neil Manson, MD; Atlantic Health Sciences Corporation, Saint John, New Brunswick, Canada BACKGROUND CONTEXT: The incidence of Adjacent Segment Degeneration after spinal fusion is variable with a third of cases requiring revision surgery. Acute Adjacent Segment Fracture (AASF) of the end or adjacent, proximal or distal vertebrae is not well recognized and sparsely reported on. Associated neurological compromise and instability necessitates urgent major revision surgery and subsequent potential morbidity in this population.Identifying risk factors to prevent these catastrophies from taking place is important. PURPOSE: The purpose of this study was to determine the incidence of AASF and to identify risk factors associated with its occurrance. STUDY DESIGN/ SETTING: Acute fracture post spinal fusion was defined as those presenting within 4 months.321 instrumented thoracolumbar fusions were performed between 2005–07 and 13 cases of AASF were identified. These patients were analyzed clinically and radiologically to look at possible risk factors. The clinical presentation and treatment of AASF was studied. This was a retrospective review of a prospective data bank in one institution. PATIENT SAMPLE: 13 cases of AASF were studied over the 2 yr time period 2005–2007. These were decompression, fusion and instrumentation surgeries performed at the index operation for spinal stenosis. 1 pt was a 2level and 12 were for O2 levels, all surgery performed in the same institution by the authors. OUTCOME MEASURES: Patient demographics, fusion levels at index operation, radiological analysis (sagittal, coronal axes; pre-fracture pedicle screw instrumentation position, type of fracture), type of revision surgery necessary and SF-36, ODI evaluations were outcome measures in this study. METHODS: 321 instrumented spinal fusions were reviewed between 2005–2007. 13 cases of AASF were identified presenting before 4 mos post op and are the subject of this study. Type of fracture, neurological picture, radiological assessments and clinical evaluations were carried out. Type of revision surgery and response were assessed.Incidence and risk factors were identified. RESULTS: The incidence of AASF in this group was 4%(13/321). The overall incidence of Adjacent Segment Degeneration of all types was 25%, 8% requiring surgery. There were 12 females and 1 male in the AASF grp, avg age 75, avg no. levels fused:3.5 at the index OR.9/13 had proximal and 5/13 had distal fractures. 2 pts required surgery for repeat fractures. 12/13 required surgery to address instability and