Distribution of in vivo and in vitro range of motion following 1-level arthroplasty with the CHARITÉ artificial disc compared with fusionBryan W. Cunningham, M.Sc.1, Paul C. McAfee, M.D.1, Fred H. Geisler, M.D., Ph.D.2, Gwen Holsapple, B.S.1, Karen Adams, B.S.1, Scott L. Blumenthal, M.D.3, Richard D. Guyer, M.D.3, Andrew Cappuccino, M.D.4, John J. Regan, M.D.5, Ira L. Fedder, M.D.1, and P. Justin Tortolani, M.D.1 1Spine and Scoliosis Center, St. Joseph's Hospital, Baltimore, Maryland; 2Illinois Neuro-Spine Center, Aurora, Illinois; 3Texas Back Institute, Plano, Texas; 4Buffalo Spine Surgery, Lockport, New York; and 5Goldstein and Penenberg Orthopedic Associates, Beverly Hills, California Abbreviations used in this paper: FDA = Food and Drug Administration; IDE = Investigational Device Exemption; PS = pedicle screw; ROM = range of motion. Address correspondence to: Fred H. Geisler, M.D., Ph.D., Illinois Neuro-Spine Center, 2020 Ogden Avenue, Suite 335, Aurora, Illinois 60504. email: fgeisler@fredgeisler.com. DOI: 10.3171/SPI-08/01/007 Object One of the goals of lumbar arthroplasty is to restore and maintain range of motion (ROM) and to protect adjacent levels from abnormal motion, which may be a factor in transition syndrome following arthrodesis. In this study, in vitro ROM results were compared with in vivo, 2-year postoperative radiographic ROM evaluations. Methods Radiographs of patients enrolled in the CHARITÉ investigational device exemption study were analyzed at baseline and at 2 years postoperatively. The ROM in flexion/extension at the implanted and adjacent levels was measured, normalized, and compared with ROM results obtained using cadaver (in vitro) evaluations. Results Preoperative ROM distributions in patients enrolled for arthroplasty or fusion at the L4–5 level was as follows: 28% motion was observed at L3–4, 35% at L4–5 and 37% at L5–S1. Following a one-level arthroplasty at L4–5, the in vivo ROM distribution from L-3 to S-1 at the 2-year time point was 36% at L3–4, 30% at L4–5 and 35% at L5–S1. Following a one-level fusion with BAK and pedicle screws at L4–5, the in vivo ROM distribution from L-3 to S-1 at the 2-year time point was 45% at L3–4, 9% at L4–5 and 46% at L5–S1. Conclusions The baseline as well as the 2-year in vivo data confirmed previously published in vitro data. One-level arthroplasty was shown herein to replicate the normal distribution of motion of the intact spine. KEYWORDS:arthrodesis; arthroplasty; clinical trial; investigational device; range of motion.
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