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  • The Most Recent Evidence for the Radiographic Diagnosis of Cervical Arthrodesis – When will the Food and Drug Administration Change the Spinal Investigational Device Exemptions Guidelines.

    Final Number:

    Blake N Staub MD; John Hipp PhD

    Study Design:

    Subject Category:

    Meeting: Congress of Neurological Surgeons 2014 Annual Meeting

    Introduction: Medical device trials rely on the Food and Drug Administration (FDA) Investigational Device Exemptions document as a guide for fusion assessment. Unfortunately, the methodology of grading cervical spinal arthrodesis suggested by this fourteen-year-old document is flawed and antiquated according to more recent data. Lax fusion thresholds can potentially have a significant impact on reported rates of fusion and pseudoarthrosis. The purpose of this abstract is to review the current literature for assessing cervical segmental fusion and provide a new perspective on the current FDA requirements.

    Methods: A literature review was undertaken to elucidate new guidelines for what constitutes a fused cervical segment based upon the most recent scientific literature.

    Results: The current FDA guidelines state that cervical arthrodesis can be identified by: evidence of bridging, trabecular bone, translational motion less than three millimeters, and angular motion less than five degrees on flexion-extension imaging. In 2009, Kaiser et al concluded that pseudoarthrosis is best detected by intra-spinous process motion of greater than two millimeters. In addition, they suggested that all fusion assessments be performed by blinded observers as radiographic diagnoses diverge between the operating surgeon and a blinded radiologist when patients show clinical improvement. More recent data has shown that with validated computerized measurement systems, intervertebral motion less than or equal to one millimeter has been shown to be as reliable as thin-slice CT scans in assessing arthrodesis.

    Conclusions: Recent studies have set forth new criteria by which cervical segmental fusion should be assessed: interspinous process motion less than two millimeters and/or intervertebral motion less than one degree measured by a computerized system. Radiologists assessing attempted fusion should be blinded to the clinical results. Also, bone trabeculation is neither as sensitive nor specific as interspinous or intervetebral motion in assessing fusion. When will the FDA change its guidelines to match the current scientific evidence?

    Patient Care: Medical device companies frequently release new products and studies either promoting enhanced fusion rates in the cervical spine or using anterior cervical arthrodesis as the control group for studies on motion preserving devices. The lax fusion thresholds promoted by the FDA lead to an underdiagnosis of pseudoarthrosis after attempted cervical arthrodesis. In addition, in motion sparing device trials, if the rate of pseudoarthrosis is being under reported in the control fusion group, the evidence could point more strongly to the use of motion sparing devices in the cervical spine. Patients and clinicians will both benefit from tightened fusion criteria as medical devices will be held to a higher standard.

    Learning Objectives: By the conclusion of this session participants should be able to: 1) Understand the current FDA guidelines for radiographically assessing cervical arthrodesis. 2) Describe the criteria recommended by the most recent literature for radiographically assessing fusion/pseudoarthrosis.

    References: 1. Phillips FM, Carlson G, Emery SE, Bohlman HH. Anterior cervical pseudarthrosis. natural history and treatment. Spine (Phila Pa 1976). 1997;22(14):1585-1589. 2. Ploumis A, Mehbod A, Garvey T, Gilbert T, Transfeldt E, Wood K. Prospective assessment of cervical fusion status: Plain radiographs versus CT-scan. Acta Orthop Belg. 2006;72(3):342-346. 3. Newman M. The outcome of pseudarthrosis after cervical anterior fusion. Spine (Phila Pa 1976). 1993;18(16):2380-2382. 4. Kaiser MG, Mummaneni PV, Matz PG, et al. Radiographic assessment of cervical subaxial fusion. J Neurosurg Spine. 2009;11(2):221-227. 5. Sudhakar N, Laing RJ, Redfern RM. Assessment of fusion after anterior cervical discectomy. Br J Neurosurg. 2003;17(1):54-59. 6. Fountas KN, Kapsalaki EZ, Smith BE, et al. Interobservational variation in determining fusion rates in anterior cervical discectomy and fusion procedures. Eur Spine J. 2007;16(1):39-45. 7. Food And Drug Administration. Guidance document for the preparation of IDEs for spinal systems. U.S. Department of Health and Human Services Food and Drug Administration Center for Devices and Radiological Health Orthopedic Devices Branch Division of General and Restorative Devices Office of Device Evaluation; 2000. 8. Hipp JA, Reitman CA, Wharton N. Defining pseudoarthrosis in the cervical spine with differing motion thresholds. Spine (Phila Pa 1976). 2005;30(2):209-210. 9. Cannada LK, Scherping SC, Yoo JU, Jones PK, Emery SE. Pseudoarthrosis of the cervical spine: A comparison of radiographic diagnostic measures. Spine (Phila Pa 1976). 2003;28(1):46-51. 10. Skolasky RL, Maggard AM, Hilibrand AS, et al. Agreement between surgeons and an independent panel with respect to surgical site fusion after single-level anterior cervical spine surgery: A prospective, multicenter study. Spine (Phila Pa 1976). 2006;31(15):E503-6. 11. Selby MD, Clark SR, Hall DJ, Freeman BJ. Radiologic assessment of spinal fusion. J Am Acad Orthop Surg. 2012;20(11):694-703. 12. Fassett DR, Apfelbaum RI, Hipp JA. Comparison of fusion assessment techniques: Computer-assisted versus manual measurements. J Neurosurg Spine. 2008;8(6):544-547. 13. Ghiselli G, Wharton N, Hipp JA, Wong DA, Jatana S. Prospective analysis of imaging prediction of pseudarthrosis after anterior cervical discectomy and fusion: Computed tomography versus flexion-extension motion analysis with intraoperative correlation. Spine (Phila Pa 1976). 2011;36(6):463-468. 14. Mourning D, Reitman CA, Heggeness MH, Esses SI, Hipp JA. Initial intervertebral stability after anterior cervical discectomy and fusion with plating. Spine J. 2007;7(6):643-646. 15. Hacker RJ, Cauthen JC, Gilbert TJ, Griffith SL. A prospective randomized multicenter clinical evaluation of an anterior cervical fusion cage. Spine (Phila Pa 1976). 2000;25(20):2646-54; discussion 2655. 16. Gruskay JA, Webb ML, Grauer JN. Methods of evaluating lumbar and cervical fusion. Spine J. 2014;14(3):531-539. 17. Hilibrand AS, Dina TS. The use of diagnostic imaging to assess spinal arthrodesis. Orthop Clin North Am. 1998;29(4):591-601. 18. Biswas D, Bible JE, Bohan M, Simpson AK, Whang PG, Grauer JN. Radiation exposure from musculoskeletal computerized tomographic scans. J Bone Joint Surg Am. 2009;91(8):1882-1889. 19. Parry RA, Glaze SA, Archer BR. The AAPM/RSNA physics tutorial for residents. typical patient radiation doses in diagnostic radiology. Radiographics. 1999;19(5):1289-1302. 20. Baskin DS, Ryan P, Sonntag V, Westmark R, Widmayer MA. A prospective, randomized, controlled cervical fusion study using recombinant human bone morphogenetic protein-2 with the CORNERSTONE-SR allograft ring and the ATLANTIS anterior cervical plate. Spine (Phila Pa 1976). 2003;28(12):1219-24; discussion 1225. 21. Coric D, Nunley PD, Guyer RD, et al. Prospective, randomized, multicenter study of cervical arthroplasty: 269 patients from the Kineflex|C artificial disc investigational device exemption study with a minimum 2-year follow-up: Clinical article. J Neurosurg Spine. 2011;15(4):348-358. 22. Dai LY, Jiang LS. Single-level instrumented posterolateral fusion of lumbar spine with beta-tricalcium phosphate versus autograft: A prospective, randomized study with 3-year follow-up. Spine (Phila Pa 1976). 2008;33(12):1299-1304. 23. Cauthen JC, Theis RP, Allen AT. Anterior cervical fusion: A comparison of cage, dowel and dowel-plate constructs. Spine J. 2003;3(2):106-17; discussion 117. 24. DuBois CM, Bolt PM, Todd AG, Gupta P, Wetzel FT, Phillips FM. Static versus dynamic plating for multilevel anterior cervical discectomy and fusion. Spine J. 2007;7(2):188-193. 25. Foley KT, Mroz TE, Arnold PM, et al. Randomized, prospective, and controlled clinical trial of pulsed electromagnetic field stimulation for cervical fusion. Spine J. 2008;8(3):436-442. 26. Heller JG, Sasso RC, Papadopoulos SM, et al. Comparison of BRYAN cervical disc arthroplasty with anterior cervical decompression and fusion: Clinical and radiographic results of a randomized, controlled, clinical trial. Spine (Phila Pa 1976). 2009;34(2):101-107. 27. Miller LE, Block JE. Safety and effectiveness of bone allografts in anterior cervical discectomy and fusion surgery. Spine (Phila Pa 1976). 2011;36(24):2045-2050. 28. Mummaneni PV, Burkus JK, Haid RW, Traynelis VC, Zdeblick TA. Clinical and radiographic analysis of cervical disc arthroplasty compared with allograft fusion: A randomized controlled clinical trial. J Neurosurg Spine. 2007;6(3):198-209. 29. Pechlivanis I, Thuring T, Brenke C, et al. Non-fusion rates in anterior cervical discectomy and implantation of empty polyetheretherketone cages. Spine (Phila Pa 1976). 2011;36(1):15-20. 30. Song J, Taghavi CE, Hsu DW, Song KJ, Song JH, Lee KB. Radiological changes in anterior cervical discectomy and fusion with cage and plate construct: The significance of the anterior spur formation sign. Spine (Phila Pa 1976). 2012;37(4):272-279. 31. Suchomel P, Barsa P, Buchvald P, Svobodnik A, Vanickova E. Autologous versus allogenic bone grafts in instrumented anterior cervical discectomy and fusion: A prospective study with respect to bone union pattern. Eur Spine J. 2004;13(6):510-515. 32. Yue WM, Brodner W, Highland TR. Long-term results after anterior cervical discectomy and fusion with allograft and plating: A 5- to 11-year radiologic and clinical follow-up study. Spine (Phila Pa 1976). 2005;30(19):2138-2144.

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