Sagittal Alignment Following Lumbar Three-Column Osteotomy: Does the Level of Resection Matter?

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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.

Proceedings of the NASS 29th Annual Meeting / The Spine Journal 14 (2014) 1S–183S spinopelvic alignment, apex of lordosis, resection angle and complications or revisions rates. Uni- and multivariate analyses were performed and correlations were tested using Pearson for continuous variables and Spearman for apex or osteotomy level. RESULTS: 347 patients were included (mean age 60 yrs, BMI 28kg/m2, 69% female). Preoperative parameters demonstrated a severe deformity (PT: 32.6610.9, SVA: 145.6678.6mm, PI-LL: 36.8619.3). Average resection angle was 25.3 without significant difference across 3CO levels. Postoperatively, all these parameters were significantly improved (at 1 year, PT: 23.9611.5, SVA: 45.7663.4, PI-LL: 5.2618.0, p!0.001). There were no significant correlations between 3CO level and amount of SVA or PT correction (postoperative change in SVA: -106.8676.8, in PT: -8.769.2). Postop apex location, which was more caudal than 3CO level, significantly correlated with a greater correction of PT (2 per more caudal level, r5-0.2, p50.006) but not with SVA or PI-LL. A significant correlation existed between lower 3CO level and revision for pseudarthrosis (OR54.4 between 3M-1Y; OR52.8 between 1Y-2Y, p50.01) and a higher rate of motor deficits (OR52.0, p50.015). The overall risk of perioperative complications was related to the degree of wedge resection (p50.03). CONCLUSIONS: In this study, caudal lumbar 3CO does not lead to greater SVA correction. The location of postoperative apex of lordosis has a significant impact on PT. While much attention is paid to the degree of resection during surgery, restoration of lordotic apex appears to have a greater impact on spinopelvic alignment, which is not identical to osteotomy level. However, caudal levels are associated with a higher rate of motor deficits. This could be due to the anatomical consideration of roots and lumbar plexus. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. http://dx.doi.org/10.1016/j.spinee.2014.08.320

P67. Surgical Skills Curriculum: Development of Orthopedic Training Modules William Camisa, MS1, Eric A. Hohn, MD2, Adam G. Brooks, MD2, Jeremi M. Leasure, MS3, Dimitriy G. Kondrashov, MD4, William H. Montgomery, III, MD5, William McGann, MD2, Jennifer van Warmerdam, MD6; 1Taylor Collaboration, San Francisco, CA, US; 2St. Mary’s Medical Center, San Francisco, CA, US; 3Oakland, CA, US; 4St. Mary’s Spine Center/San Francisco Orthopedic Surgeons, San Francisco, CA, US; 5San Francisco, CA, US; 6San Francisco Orthopaedic Surgeons Medical Group, San Francisco, CA, US BACKGROUND CONTEXT: In the present state of orthopedic education, many of the basic manual skills required of orthopedic residents are taught in the clinic or during surgery. A need exists to develop a curriculum to assess and track progress in these basic manual skills outside of the operating room. These assessments will speed improvement in target areas for each resident. METHODS: Four modules were developed with the input of attending faculty along with orthopedic surgery residents. The modules include 1) cortical drilling, 2) drill trajectory, 3) oscillating saw, and 4) pedicle probing. These modules were tested on 15 orthopedic surgery residents ranging from post-graduate year (PGY) 1 to PGY 5 experience. Validity and reliability results were calculated using standard ANOVA and multivariate regression analysis accounting for PGY level, number of attempts, and specific outcome target results specific to the simulation module. RESULTS: The first module (cortical drilling) carried a mean success rate of 56% 6 5%. There was a statistically significant (p!0.05) difference in performance according to the diameter of the drill used from 33% 6 7% with large diameter to 70% 6 6% with small diameter. The second module (drill trajectory) carried a success rate of 85% 6 3% with a trend (p50.11) toward improvement across PGY level. The third module (oscillating saw) carried a mean success rate of 25% 6 5% (trajectory) and 84% 6 6% (depth). We observed a significant (p!0.05) improvement in trajectory

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performance during the second attempt. The fourth module carried a success rate of 46% 6 10%. CONCLUSIONS: A surgical skills curriculum consisting of 11 modules was designed to improve the basic manual skills of orthopedic residents. The results of this pilot study on a small number of residents are promising. The modules were inexpensive and easy to administer. Conclusions of statistical significance include 1) residents could more easily detect changes in surrogate bone thickness with a smaller diameter drill than with a larger diameter drill, and 2) residents significantly improved saw trajectory with an additional attempt at the module. It is very likely that a higher powered study with a larger pool of residents would yield more statistical conclusions. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. http://dx.doi.org/10.1016/j.spinee.2014.08.321

P68. A Biomechanical Comparison of Short-Segment Posterior Fixation Including the Fractured Vertebra versus 360 Fixation in Unstable Burst Fractures of the Lumbar Spine in an Animal Model Kenny S. David, MBBS, MS, FACS; Christian Medical College, Vellore, India BACKGROUND CONTEXT: Posterior short-segment fixation has been favored over long-segment fixation for burst fractures of thoracolumbar spine in view of preservation of motion levels. However, short-segment spanning fixation (SSSF) is known to be associated with a higher rate of progressive kyphosis and implant failure. Combined anterior and posterior or ‘‘circumferential’’ fixation (CF) provides superior biomechanically stability, and has been shown to be clinically successful, but is known to have associated morbidities and a high rate of complications. The option of augmenting SSSF by the insertion of an ‘‘intermediate screw’’ into the fractured level (SSIF) is popular. However, the comparative biomechanical stability provided by SSIF and CF is unknown. PURPOSE: The aim of our study is to compare the biomechanical stability of short-segment spanning fixation (SSSF) and circumferential fixation (CF) under physiological loading in a cadaveric animal model. STUDY DESIGN/SETTING: Biomechanical study in a cadaveric animal model. METHODS: Ten fresh-frozen calf spine specimens were prepared and then underwent testing of biomechanical characteristics. Range of motion (ROM) and load-displacement curves (LDC) were recorded for the intact specimens using a universal testing device and 3D motion tracker in flexion–extension, lateral flexions and torque. An unstable burst fracture was then produced in all specimens using the drop weight method, and confirmed with computerized tomography (CT) scans. The specimens were then divided into two groups; Group A specimens were instrumented using SSIF, and Group B specimens were instrumented using CF. Biomechanical testing was repeated for all specimens. Finally, the middle (intermediate) screws in the Group A specimens were removed and the specimens were tested again. RESULTS: Both groups exhibited a decrease in the ROM and increase in the construct stiffness in all test directions. The change in ROM and construct stiffness was comparable in both groups. Group A specimens were significantly more stable in torque, while group B specimens showed greater stability in lateral flexions. The ‘‘intermediate screw’’ significantly decreased ROM in both lateral flexion and torque. CONCLUSIONS: Both SSIF and CF can restore comparable stability to the injured thoracolumbar spine. The insertion of an intermediate screw is useful for enhancing construct stiffness, and is biomechanically comparable to circumferential fixation. In view of these facts, and also the favourable clinical safety profile of SSIF, consideration should be given to SSIF over CF in the operative treatment of unstable burst fractures of the thoracolumbar spine.

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.