P65. CT and Biomechanical Evaluation of Screw Fixation Options at the Cervicothoracic Junction Intralaminar vs. Intrapedicular Techniques

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Proceedings of the NASS 23rd Annual Meeting / The Spine Journal 8 (2008) 1S–191S FDA DEVICE/DRUG STATUS: MAVERICK: Investigational/Not approved; KINEFLEX: Investigational/Not approved; CHARITE: Approved for this indication. doi:10.1016/j.spinee.2008.06.307

P64. Adjacent Vertebral Body Osteolysis with Bone Morphogenetic Protein Use in Transforaminal Lumbar Interbody Fusion Ronald Lehman, Jr., MD1, Melvin Helgeson, MD2, Jeanne Patkowski, BS2, Andrew Mack, MD1, Michael Rosner, MD1; 1Walter Reed Army Medical Center, Washington, DC, USA; 2Washington, DC, USA

Figure 2. Empirical density estimation at C3-4 comparing age 45 and younger (dotted line) to all subjects. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. doi:10.1016/j.spinee.2008.06.306

P63. Prospective Randomized Comparison of Three Lumbar Artificial Disc Replacements (ADR) Kenneth Pettine, MD, E. Jeffrey Donner, MD; Rocky Mountain Spine Arthroplasty Specialists, Loveland, CO, USA BACKGROUND CONTEXT: This is the only prospective data available comparing three different ADR’s. PURPOSE: To establish safety and efficacy between the MaverickÔ (M), Charite´ Ô(C), and KineflexÔ (K) A.D.R.’s. STUDY DESIGN/ SETTING: Follow up on three ADR’s performed by two surgeons, as part of FDA studies at one I.D.E. site were reviewed. PATIENT SAMPLE: There were 25 Maverick, 31 Charite´, and 35 Kineflex patients. The majority of A.D.R.’s were performed at L5-S1 vs. L4-L5 (M) 19 to 6, (C) 19 to 12 and (K) 28 to 7. Inclusion/exclusion criteria will be discussed. OUTCOME MEASURES: Clinical success was defined by at least 25% improvement in ODI and VAS scores at minimum two year follow-up. METHODS: ODI, VAS, patient satisfaction, additional procedures, and type of implant were evaluated prospectively. RESULTS: Re-operations included: (M) 1 infection, (C) 3 implant complications (K) 1 implant complication. These cases will be presented. ODI results for all groups: Pre-op5(M) 57.6, (C) 63.8, and (K) 61.1; One-year post-op5(M) 16.3, (C) 27.3, and (K) 20.4; Two-year postop5(M) 14.6 (p!0.001), (C) 20.5 (p!0.001), and (K) 19.3 (p!0.001) VAS results for all groups: Pre-op5(M) 74.1, (C) 85, (K) 83.9; One year post-op5(M) 27.9, (C) 31.4, and (K) 27.3; Two-year post-op5(M) 20.5 (p!0.001), (C) 33.8 (p!0.001), and (K) 26.9 (p!0.001) F.D.A. clinical success was met in (M) 90%, (C) 83.5%, (K) 90.5% of patients. Patients with a VAS less than 2 occurred in (M) 68%, (C) 29%, (K) 47%. Patients with an ODI less than 10 occurred in (M) 67% (C) 33%, (K) 52%. Patient satisfaction at two-year follow up was (M) 96%, (C) 84%, and (K) 91%. CONCLUSIONS: All three A.D.R.’s demonstrated safety with a trend to more device related complications with (C) 3 compared to (M) 1 and (K) 1. They all showed efficacy with a statistically significant improvement in ODI and VAS at two year follow-up (p!0.001). F.D.A. clinical success was (M) 90%, (C) 83.8%, (K) 90.5%. The Maverick demonstrated statistical superiority in ODI(p!0.05) measurements compared to the Charite´ or Kineflex and VAS (p!0.05) compared to Charite.

BACKGROUND CONTEXT: Recently transforaminal lumbar interbody fusions (TLIF) has gained popularity as a method to obtain an interbody fusion from a posterior approach. Several authors have reported cases of osteolysis associated with bone morphogenetic protein (BMP) use in interbody fusions, but to date no study has evaluated the time-dependent rate of osteolysis in the postoperative period. PURPOSE: The purpose of our study was to determine the incidence and resolution of osteolysis associated with BMP used in TLIF. STUDY DESIGN/ SETTING: Retrospective Radiographic Clinical Review. PATIENT SAMPLE: 23 Patients who underwent TLIF with BMP. OUTCOME MEASURES: CT Scan. METHODS: We performed a retrospective analysis of all patients at our facility who underwent TLIF with BMP. Included were all patients who had obtained a CT scan on the day of surgery, 3 to 6 months postoperatively, and 1 to 2 years postoperatively. Areas of osteolysis were defined as lucency within the vertebral body communicating with the interbody spacer that was not present on the immediately postoperative CT scan. All CT scans were obtained with 1.25 mm cuts in the axial, sagittal and coronal planes. Areas of osteolysis were measured in all 3 planes and the volume used for comparison of the 3–6 months CT scans with the greater than 1 year CT scan. Fusion was determined by flexion/extension radiographs and CT scans at final follow-up. RESULTS: Twenty-three patients whom underwent TLIF with BMP had obtained CT scans at all time periods required for evaluation. There were 5 females and 18 males with an average age of 38.2 years at the time of surgery (range 23–81). Seventy-eight vertebral bodies/endplates were assessed for osteolysis (39 levels). The incidence of osteolysis three to six months postoperatively in the adjacent vertebral bodies was 54%. Comparatively, the incidence at 1 and 2 years was 41%. Although not statistically significant, the mean volume of osteolysis was less at 1–2 years compared to 3–6 months (p50.082), 0.306 cm3 and 0.216 cm3, respectively. The area/rate of osteolysis did not appear to significantly affect the rate of fusion or final outcome with an overall union rate of 83%. CONCLUSIONS: The rate of osteolysis decreased at 1 year compared to 3–6 months, but only 25% of the vertebral bodies with evidence of osteolysis at 3–6 months completely resolved by one year. Furthermore, although the volume of osteolysis decreased, it was still present at ultimate fusion in the majority of patients creating a bone void within the fused segment. FDA DEVICE/DRUG STATUS: Bone Morphogenetic Protein: Not approved for this indication. doi:10.1016/j.spinee.2008.06.308

P65. CT and Biomechanical Evaluation of Screw Fixation Options at the Cervicothoracic Junction Intralaminar vs. Intrapedicular Techniques Mario J. Cardoso, MD, Anton Dmitriev, MSc, Ronald Lehman, Jr., MD, Melvin Helgeson, MD, Patrick Cooper, MD, Michael Rosner, MD; Walter Reed Army Medical Center, Washington, DC, USA BACKGROUND CONTEXT: Proximal thoracic fixation in cevicothoracic fusions is placed in a challenging biomechanical environment.

Proceedings of the NASS 23rd Annual Meeting / The Spine Journal 8 (2008) 1S–191S Transpedicular instrumentation is well accepted, but salvage techniques in this region are limited. Recently, the intralaminar technique for fixation into this region has gained in popularity. PURPOSE: The purpose of our study was to define T1 and T2 anatomic laminar size, and evaluate the bone-screw interface strength of various pedicle screw options and intralaminar techniques. STUDY DESIGN/ SETTING: In-Vitro Cadaveric Human Study. PATIENT SAMPLE: 14 Human Cadaveric Specimens. OUTCOME MEASURES: Insertional Torque and Peak Failure Load. METHODS: Fourteen fresh-frozen cervicothoracic cadaveric specimens were DEXA scanned for bone mineral density (BMD). In addition, all specimens were imaged under computed tomography (CT) obtaining 1 mm axial sections. On the right side, pedicle screws were first placed in a straight forward trajectory, with insertional torque (IT) recorded with each revolution. Screws were then pulled out in-line with the screw axis to simulate intraoperative failure of fixation. ‘‘Salvage’’ anatomic trajectory pedicle screws were then inserted into the same pedicle, with IT and pull-out strength (POS) measured in a similar fashion. Finally, all specimens were ‘‘salvaged’’ with intralaminar screws placed into the contralateral laminae from the right spinous process/ lamina junction. All screws were placed by a fellowship trained spine surgeon under direct fluoroscopic visualization. Standard 4.5 mm cervical pedicle screws were utilized as they are the maximum diameter available in a cervical set for cervicothoracic reconstructions. Insertional torque (IT) was measured in ‘‘lbs-in’’. Tensile loading to failure was performed at a rate of 0.25mm/sec using a MTS 858 MiniBionix II System. Data was normalized to peak failure load of the index straight forward trajectory and recorded as percent change. RESULTS: Laminar screws as a salvage technique generated statistically greater peak IT (p!0.001) and relative POS (p50.032) compared to straight forward transpedicular screws as the initial fixation type (Table). Furthermore, laminar screws, when compared to the salvage anatomic trajectory pedicle screws, had a significantly greater peak IT (p50.007). The peak IT showed a stronger correlation with POS in laminar screws (r50.744) than straight forward (r50.548) or anatomic (r50.471) pedicle screws. A similar trend was noted in mean IT (r50.786, r50.568, r50.521, respectively). BMD correlated with POS in all methods of fixation: straight forward pedicle, anatomic pedicle, and laminar screws (r50.765, r50.719, and r50.632, respectively). The mean laminar width measured on CT at the thinnest point was 5.960.7 mm (Range 4.8-7.5). CONCLUSIONS: Our results suggest that laminar screws, used as a salvage technique in the proximal thoracic spine, provide stronger fixation than transpedicular screws when using standard 4.5mm cervical screws. Intralaminar screws present as a biomechanically sound salvage technique in this region, and appear to be a safe, effective option for instrumenting the proximal thoracic spine.

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sacrum remains the weak link in posterior constructs. The purpose of this study is to present the technique of transilial bar pelvic fixation, investigate the clinical and radiographic outcomes using this technique. PURPOSE: The purpose of our study is to present our experience with the technique of transilial bar fixation for lumbosacral fixation. STUDY DESIGN/ SETTING: We retrospectively reviewed the clinical and radiographic data of 53 consecutive patients who had undergone long posterior spinal fusions extending to the sacrum using the transileal bar technique for spinopelvic fixation. Patients clinical outcome were evaluated using prospectively collected validated questionnaires, specifically the Oswestry disability index (ODI), the SF 12 and the VAS. All patients underwent surgery at a single institution. Minimal follow up was 2 years (2-7). Radiographs were assessed for evidence of fusion, degree of correction and instrumentation failure. Patients completed the ODI,the SF12and the VAS, pre operatively and at the most recent follow-up. PATIENT SAMPLE: 53 consecutive patients treated at a tertiary care university hospital. OUTCOME MEASURES: Patients clinical outcomes were evaluated using prospectively collected validated outcome questionnaires. METHODS: We retrospectively reviewed the clinical and radiographic data of 53 consecutive patients who had undergone long posterior spinal fusions extending to the sacrum using the transileal bar technique for spinopelvic fixation. Patients clinical outcomes were evaluated using prospectively collected outcome questionnaires, specifically the Oswestry disability index (ODI), the SF 12 and the VAS. All patients underwent surgery at a single institution. Minimal follow up was 2 years (2-7). Radiographs were assessed for evidence of fusion, degree of correction and instrumentation failure. Patients completed the ODI, the SF12 questionnaire and the VAS, at regular follow-up. RESULTS: Overall fusion rate was greater than 90%. Five patients sustained a fracture at the sacrum below the level of the transilial bar. Four patients had the bar removed secondary to pain. There was an overall improvement in both ODI, SF 12 and VAS scores from pre-operative baseline. CONCLUSIONS: Sacropelvic fixation using the transilial bar technique, is an easy and effective method of achieving sacropelvic fixation in long posterior spinal fusions. However patients with osteoporosis are at an increased risk for sacral fractures and this procedure may not be suitable in this group. The mode of failure appears to be a shear/compression fracture at or below the S1 pedicle screws.

Mean Insertional Torque and Peak Pull Out Force

Mean IT (lbs-in) Mean POS (% change)

Straight Forward Trajectory

Anatomic Trajectory

Laminar Screw

2.20 6 0.53 1006 0.00

2.7660.78 108.96 20.3

3.8661.65 115.8637.6

FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. doi:10.1016/j.spinee.2008.06.309

FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. doi:10.1016/j.spinee.2008.06.310

P66. Sacropelvic Fixation Using the Transilial Bar Technique in Adult Spinal Deformity Surgery Philip Neubauer, MD1, Richard Skolasky, Jr., ScD2, Khaled Kebaish, MD2; 1 Johns Hopkins Hospital, Baltimore, MD, USA; 2Johns Hopkins University, Baltimore, MD, USA BACKGROUND CONTEXT: Achieving solid fusion at the lumbar sacral junction remains an ongoing technical challenge. Stable fixation to the

P67. A Lateral Fluoroscopic Guide to Prevent Occipitocervical and Atlantoaxial Joint Violation during C1 Lateral Mass Screw Placement Jin Sup Yeom, MD1, Jacob Buchowski, MD2, Kun Woo Park, MD1, Bong-Soon Chang, MD1, Choon-Ki Lee, MD1, K. Daniel Riew, MD2; 1 Seoul National University Bundang Hospital, Sungnam,