Biomechanical Validation of a Synthetic Lumbar Spine

Proceedings of the NASS 29th Annual Meeting / The Spine Journal 14 (2014) 1S–183S management, etc.).Our results are based on 1,000 simulated patients, each proceeding through 6-month cycles over 10- and 20-year follow-up periods. Confidence intervals are formed by repeating the simulations for 1,000 iterations. RESULTS: Surgical costs averaged $170,523 over 10-year follow-up, with average QALYs of 6.3. Meanwhile, nonsurgical costs averaged $40,046 over 10-year follow-up with average QALYs of 5.4. This resulted in an average ICER from surgical treatment of $144,000 (95% CI: $121,500 to $177,500) per QALY gained. Over 20-year follow-up, surgical costs averaged $208,616 and QALYs averaged 9.8, while nonsurgical costs averaged $63,467 and QALYs averaged 8.6. Over 20-year follow-up, the ICER decreased (became more cost-effective) to $115,000 (95% CI: $88,850 to $156,200) per QALY gained. CONCLUSIONS: Our results illustrate the potential for surgical treatment for ASD to be cost-effective over extended follow-up compared to nonsurgical treatment. These findings argue in favor of longer follow-up in ASD studies for accurate cost-effectiveness comparison. Future research should also pursue measurement of indirect costs/benefits resulting from changes in absenteeism or productivity. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. http://dx.doi.org/10.1016/j.spinee.2014.08.316

P63. Role of Implant Costs in the Long-Term Cost Effectiveness of Surgical Treatment of Adult Spinal Deformity (ASD) International Spine Study Group1, Chessie Robinson, MA2, Ian McCarthy, PhD2, Michael F. O’Brien, MD3, Munish C. Gupta, MD4, Christopher P. Ames, MD5, Virginie Lafage, PhD6, Robert A. Hart, MD7, Douglas C. Burton, MD8, Shay Bess, MD9, Christopher I. Shaffrey, MD10, Frank J. Schwab, MD6, Khaled M. Kebaish, MD11, Justin S. Smith, MD, PhD12, Eric O. Klineberg, MD13, Richard A. Hostin, MD14; 1Brighton, CO, US; 2 Baylor Health Care System, Dallas, TX, US; 3Baylor Scoliosis Center, Plano, TX, US; 4University of California Davis Orthopaedic Surgery, Sacramento, CA, US; 5University of California San Francisco, San Francisco, CA, US; 6New York University Langone Medical Center Hospital for Joint Diseases, New York, NY, US; 7Oregon Health and Science University, Portland, OR, US; 8University of Kansas Medical Center, Kansas City, KS, US; 9Rocky Mountain Scoliosis and Spine, Denver, CO, US; 10University of Virginia Department of Neurosurgery, Charlottesville, VA, US; 11Baltimore, MD, US; 12University of Virginia Health System, Charlottesville, VA, US; 13University of California Davis School of Medicine, Sacramento, CA, US; 14Southwest Scoliosis Institute, Plano, TX, US BACKGROUND CONTEXT: Surgical implant costs of ASD surgery remain high. However, little is known regarding the impact of potential reductions in implant costs in the cost effectiveness of ASD surgery over long-term follow-up. PURPOSE: Using a Markov model populated by estimates from literature and observed data on costs and health-related quality-of-life (HRQOL) outcomes, we simulate costs and outcomes for surgical and nonsurgical treatment, estimating incremental cost-effectiveness ratios (ICERs) over 10-years. We analyze the incremental cost-effectiveness of surgical treatment for ASD incorporating hypothetical reductions in the cost of implants (0-50%). STUDY DESIGN/SETTING: Analysis of statistics from published literature and retrospective analysis of observed data from a single-center, administrative dataset and a multicenter prospective dataset. OUTCOME MEASURES: Summary statistics on mortality rates, revision rates, and nonsurgical costs are taken from literature, while statistics for surgical costs and quality-adjusted life-years (QALYs) are taken from a single-center, retrospective administrative dataset and a multicenter prospective dataset. Inpatient costs were collected from hospital administrative data and costs of implants were measured as the total amount paid

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by the hospital for the entire construct, excluding biologics. QALYs were calculated from the SF-6D. METHODS: We develop a Markov model with parameter uncertainty, incorporating costs and outcome distributions from published literature and observed patient data. We project costs and QALYs for the surgical and nonsurgical cohort allowing varied readmission, cost and QALY outcomes over 10-year follow-up. Costs for surgical and nonsurgical patients are intended to reflect the full spectrum of services incurred for surgical or nonsurgical care (eg, physical therapy, pain management, etc.). Our results are based on 1,000 simulated patients, each proceeding through 6-month cycles over 10-year follow-up. Confidence intervals are formed by repeating the simulations for 1,000 iterations. RESULTS: Total surgical costs averaged $179,385 over 10-year followup, including average implant costs of $70,514, with average QALYs of 6.3. Nonsurgical costs averaged $40,039 over 10-years with average QALYs of 5.4, resulting in an average ICER from surgical treatment of $153,818 per QALY gained. Over 10-year follow-up, ICERs ranged from $144,722 based on an assumed 10% reduction in implant costs to $108,335 assuming a 50% reduction in implant costs. CONCLUSIONS: Through 10-year follow-up, reductions in implant costs of 50% are associated with a $45,483 improvement in the cost per-QALY. Our results illustrate the potential to improve the cost-effectiveness of ASD surgery to within the World Health Organization’s cost-effectiveness acceptability range (3 times GDP or $140,000 in 2010 dollars) based on reductions in implant costs, provided any such reductions can be made without negatively impacting health outcomes. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. http://dx.doi.org/10.1016/j.spinee.2014.08.317

P64. Biomechanical Validation of a Synthetic Lumbar Spine William Camisa, MS1, Jeremi M. Leasure, MS2, Jenni M. Buckley, PhD3; 1 Taylor Collaboration, San Francisco, CA, US; 2Oakland, CA, US; 3 University of Delaware, Newark, DE, US BACKGROUND CONTEXT: Human cadaveric testing is the standard model used to evaluate fusion hardware in the lumbar spine. Traditionally a cadaver specimen is biomechanically tested in its intact state, instrumented with fusion hardware and then retested to determine differences in range of motion, pedicle screw loading and fatigue properties. These measures help compare different hardware and are often used to determine an optimal fusion construct. Unfortunately cadavers can add substantial cost to a project and vary greatly between specimens in properties such as density, size and shape. In some cases having a spine with consistent mechanical properties may be beneficial. Because of this, a synthetic spine has been biomechanically tested in order to compare its properties, in this case range of motion, to those of cadaveric specimens in order to determine if it may be used as a surrogate material. METHODS: Three synthetic lumbar spine models were obtained with simulated intervertebral discs, vertebrae and ligaments. Three human cadaveric specimens, L1-L5, were also obtained and cleaned of paravertebral soft tissues with care taken not to disrupt ligamentous structures. All specimens were potted in a polymer-casting agent (Smooth Cast 300, Smooth-On, Easton, PA) to facilitate rigid fixation to the test frame during biomechanical testing. Pedicle screws were implanted into each specimen and four common lumbar fusion treatment groups were tested: intact, bilaterally fused from L1-L5, stand alone ALIF at L4-L5 junction and ALIF with bilateral fusion from L1-L5. Motion tracking markers were placed to measure the relative motion between L2-L3, L3-L4, and L4-L5. Each specimen was driven under a load-controlled pure moment up to 7.5 Nm in flexion/extension (F/E), axial rotation (AR), and lateral bending (LB). Specimens were preconditioned for 3 cycles to 7.5 Nm and then tested for 1 cycle to 7.5 Nm in increments of 1.5 Nm. Non-destructive, multidirectional bending tests were conducted on each spinal section in its intact

Refer to onsite Annual Meeting presentations and postmeeting proceedings for possible referenced figures and tables. Authors are responsible for accurately reporting disclosures and FDA device/drug status at time of abstract submission.

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Proceedings of the NASS 29th Annual Meeting / The Spine Journal 14 (2014) 1S–183S

state and following each surgical treatment. A servohydraulic press (MTS MiniBionix 858) instrumented with a custom-designed pure moment testing apparatus was used for testing. RESULTS: Results showed similar range of motion values for flexion/ extension, lateral bending and axial torsion. The average difference between the cadaver and synthetic model was 0.6 in F/E, 0.4 in lateral bending and 2.5 in axial torsion. At the L4-L5 junction, the synthetic and cadaver spine range of motion was statistically (pO0.05) similar for all four treatment groups. CONCLUSIONS: Synthetic spine offers advantages to cadaver spine if it is biomechanically similar in terms of range of motion. This study tested in order to compare its properties, in this case range of motion, to those of cadaveric specimens and found that the flexibility is similar for the intact specimens as well as three common spinal fusion procedures. If variability is not needed and a test is needed to compare two hardware constructs where a similar test material might prove more valuable the synthetic biomechanical lumbar spine models may be used. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. http://dx.doi.org/10.1016/j.spinee.2014.08.318

P65. Posterior Surgical Correction with or without Interbody in Matched Curves Provides Similar Correction in Adult Spinal Deformity International Spine Study Group1, Eric O. Klineberg, MD2, Munish C. Gupta, MD3, Stacie Nguyen, MPH4, Virginie Lafage, PhD5, Christopher P. Ames, MD6, Douglas C. Burton, MD7, Robert A. Hart, MD8, Vedat Deviren, MD6, Behrooz A. Akbarnia, MD9, Gregory M. Mundis, Jr., MD9, Christopher I. Shaffrey, MD10, Justin S. Smith, MD, PhD11, Themistocles S. Protopsaltis, MD5, Kai-Ming G. Fu, MD, PhD12, Khaled M. Kebaish, MD13, Matthew E. Cunningham, MD, PhD14, Michael P. Kelly, MD15, Frank J. Schwab, MD5, Thomas J. Errico, MD16, Richard A. Hostin, MD17, Han Jo Kim, MD18; 1Brighton, CO, US; 2University of California Davis School of Medicine, Sacramento, CA, US; 3University of California Davis Orthopaedic Surgery, Sacramento, CA, US; 4San Diego Spine Foundation, La Jolla, CA, US; 5New York University Langone Medical Center Hospital for Joint Diseases, New York, NY, US; 6University of California San Francisco, San Francisco, CA, US; 7University of Kansas Medical Center, Kansas City, KS, US; 8Oregon Health and Science University, Portland, OR, US; 9San Diego Center for Spinal Disorders, La Jolla, CA, US; 10University of Virginia Department of Neurosurgery, Charlottesville, VA, US; 11University of Virginia Health System, Charlottesville, VA, US; 12Weill Cornell Medical College, New York, NY, US; 13Baltimore, MD, US; 14Hospital for Special Surgery, New York, NY, US; 15St. Louis, MO, US; 16New York University Langone Medical Center, New York, NY, US; 17Southwest Scoliosis Institute, Plano, TX, US; 18 Hospital for Special Surgery, New York, NY, US BACKGROUND CONTEXT: Multiple options exist for the surgical correction of adult spinal deformity. The choice of these surgical procedures is often based upon surgeon preference, patient profile and curve pattern. There remains little guidance for surgeons to determine which options will provide them with the appropriate correction. PURPOSE: Evaluate the curve correction, change in health related quality of life measures (HRQOL), and complications in deformity matched Posterior Interbody (PI) or Posterior Only (PO) surgical correction. STUDY DESIGN/SETTING: Multicenter, prospective, consecutive case/ control series. PATIENT SAMPLE: 56 ASD patients. OUTCOME MEASURES: Oswestry Disability Index (ODI), SF36, and SRS-22. METHODS: Prospective, multicenter database. Inclusion criteria ageO18, adult spinal deformity, no prior fusion surgery, O4 levels fused, fusion to sacrum, complete radiographic and HRQOL outcomes, min 2-yr follow-

up. Complications were defined as minor or major per previously published criteria. Health related quality of life measures were determined for each patient for baseline, one and two years. Posterior approaches were propensity matched for Posterior Interbody (PI) and Posterior Only (PO) based on baseline SVA, PI-LL mismatch and PT by using linear regression. RESULTS: 56 patients met inclusion criteria and were matched; PI (28) and PO (28). Baseline demographics were similar for age (65 vs 63), BMI, co-morbidity, SVA (73 vs 63mm), PT (23 vs 23), LL (34 vs 38) and PI-LL (18 vs 18); PO0.05. Baseline HRQOL measures similar for both groups, except for SF-36 mental (45 vs 37; p50.03), and SRS-appearance (2.4 vs 2.1; p5.04). At 1 and 2 years HRQL improved significantly for each group, with no difference between groups. Radiographic improvement, 1yr and 2yr measures were all similar. Total EBL was greater for PI (2823 vs 1782cc; p5.014), with similar OR time and hospital stay. More Smith-Peterson Ostotomies were performed in PI group (3.2 vs 1.9 per pt; p5.005), with similar rate of PSO, and BMP dose and frequency. Intraoperative major complications occurred more often in the PI group (25% vs 4%; p5.02). There was no difference in posterior fusion grade. However, by 2 years, more revision surgery occurred for implant complications in PO (5 vs 1) for late rod fracture (3 vs 1). CONCLUSIONS: The addition of interbody to posterior deformity correction does not significantly improve radiographic parameters, HRQOL or fusion grade at 2 years. However, implant related complications were higher in the posterior only group, and were related to rod fracture. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. http://dx.doi.org/10.1016/j.spinee.2014.08.319

P66. Sagittal Alignment Following Lumbar Three-Column Osteotomy: Does the Level of Resection Matter? International Spine Study Group1, Barthelemy Liabaud, MD2, Emmanuelle Ferrero, MD3, Christopher P. Ames, MD4, Khaled M. Kebaish, MD5, Gregory M. Mundis, Jr., MD6, Richard A. Hostin, MD7, Munish C. Gupta, MD8, Oheneba Boachie-Adjei, MD9, Justin S. Smith, MD, PhD10, Robert A. Hart, MD11, Bassel G. Diebo, MD2, Themistocles S. Protopsaltis, MD12, Frank J. Schwab, MD12, Virginie Lafage, PhD12; 1 Brighton, CO, US; 2New York University, New York, NY, US; 3New York, NY, US; 4University of California San Francisco, San Francisco, CA, US; 5 Baltimore, MD, US; 6San Diego Center for Spinal Disorders, La Jolla, CA, US; 7Southwest Scoliosis Institute, Plano, TX, US; 8University of California Davis Orthopaedic Surgery, Sacramento, CA, US; 9Hospital for Special Surgery, New York, NY, US; 10University of Virginia Health System, Charlottesville, VA, US; 11Oregon Health and Science University, Portland, OR, US; 12New York University Langone Medical Center Hospital for Joint Diseases, New York, NY, US BACKGROUND CONTEXT: 3-column osteotomy (3CO) is an effective technique to correct sagittal malalignment, but is associated with high complication rates. However the distribution of correction of global truncal alignment versus pelvic retroversion remains unclear, with a belief that more caudal osteotomy leads to larger correction. PURPOSE: This study sought to investigate the impacts of osteotomy site and postoperative apex of lumbar lordosis 1) on sagittal correction and 2) on postoperative complications and revisions rates. STUDY DESIGN/SETTING: Radiographic retrospective study of a multicenter database. PATIENT SAMPLE: 347 adult spinal deformity patients with 2-year follow-up, upper instrumented vertebra above L1, and lumbar 3CO were included. OUTCOME MEASURES: 3CO resection angle, sagittal vertical axis (SVA), pelvic tilt (PT), lumbar lordosis (LL), LL apex, pelvic incidence minus lumbar lordosis (PI-LL). METHODS: Radiographic, demographic, and OR data, revisions and complications, were analyzed at baseline, 6m, 1Y, 2Y FU to quantify

Refer to onsite Annual Meeting presentations and postmeeting proceedings for possible referenced figures and tables. Authors are responsible for accurately reporting disclosures and FDA device/drug status at time of abstract submission.